Shunting Solved
Discussion
I have been suffering with a shunting problem on my Cimaera 4.0HC, I hope this will help others with a similar problem?.
When I bought the car in the spring it had suffered from very little use and shunted quite badly until the engine spun over 2200rpm.
After about a 1000 miles of Shell Optimax/VPower fuel it started to get progressively better but at 3000 miles it had stopped improving and the shunting, although reduced, was still a pain.
Three weeks ago I replaced the leads, plugs and extenders, it got a bit better.
Number 8 lead shroud was badly burnt though, it was arcing on the exhaust manifold, so to be honest I had hoped for more of an improvement.
Last weekend I added the ACT smooth bore elbow & a K&N air filter, it got a lot better, actually it surprised me how much these relatively simple changes made to the throttle response.
Then yesterday I really went for it and fitted a SC-Power plenum spacer, heat insulating plenum base gasket, trumpet bell mouths and cut the trumpets themselves down just a little bit (8mm).
I wanted to start with a small reduction in trumpet length first so I could experiment in small stages.
The spacer already had the effect of moving the trumpets away from the plenum roof by 20mm so in total they are now 28mm further away from the roof and live in a plenum that has had its volume increased by half a litre.
The car is now a totally different animal, it runs sooo smoooooth and gear changes are much cleaner.
I cant comment on any power increases I may have added but I can defiantly say its a much easier and more enjoyable car to drive.
The engine fuels & breaths fantastically well all the way from idle to the very upper limits.
Because I can now grab the gears faster, get on the power earlier it feels faster and easier to drive faster.
Early tests seem to indicate its using less fuel too.
Perhaps a bit of a cheque-book cure to the problem but hope my ramblings help others with the same issues get their cars running better?
Regards, Dave.
When I bought the car in the spring it had suffered from very little use and shunted quite badly until the engine spun over 2200rpm.
After about a 1000 miles of Shell Optimax/VPower fuel it started to get progressively better but at 3000 miles it had stopped improving and the shunting, although reduced, was still a pain.
Three weeks ago I replaced the leads, plugs and extenders, it got a bit better.
Number 8 lead shroud was badly burnt though, it was arcing on the exhaust manifold, so to be honest I had hoped for more of an improvement.
Last weekend I added the ACT smooth bore elbow & a K&N air filter, it got a lot better, actually it surprised me how much these relatively simple changes made to the throttle response.
Then yesterday I really went for it and fitted a SC-Power plenum spacer, heat insulating plenum base gasket, trumpet bell mouths and cut the trumpets themselves down just a little bit (8mm).
I wanted to start with a small reduction in trumpet length first so I could experiment in small stages.
The spacer already had the effect of moving the trumpets away from the plenum roof by 20mm so in total they are now 28mm further away from the roof and live in a plenum that has had its volume increased by half a litre.
The car is now a totally different animal, it runs sooo smoooooth and gear changes are much cleaner.
I cant comment on any power increases I may have added but I can defiantly say its a much easier and more enjoyable car to drive.
The engine fuels & breaths fantastically well all the way from idle to the very upper limits.
Because I can now grab the gears faster, get on the power earlier it feels faster and easier to drive faster.
Early tests seem to indicate its using less fuel too.
Perhaps a bit of a cheque-book cure to the problem but hope my ramblings help others with the same issues get their cars running better?
Regards, Dave.
blitzracing said:
Chimpaholic said:
I have been suffering with a shunting problem on my Cimaera 4.0HC, I hope this will help others with a similar problem?.
When I bought the car in the spring it had suffered from very little use and shunted quite badly until the engine spun over 2200rpm.
After about a 1000 miles of Shell Optimax/VPower fuel it started to get progressively better but at 3000 miles it had stopped improving and the shunting, although reduced, was still a pain.
Three weeks ago I replaced the leads, plugs and extenders, it got a bit better.
Number 8 lead shroud was badly burnt though, it was arcing on the exhaust manifold, so to be honest I had hoped for more of an improvement.
Last weekend I added the ACT smooth bore elbow & a K&N air filter, it got a lot better, actually it surprised me how much these relatively simple changes made to the throttle response.
Then yesterday I really went for it and fitted a SC-Power plenum spacer, heat insulating plenum base gasket, trumpet bell mouths and cut the trumpets themselves down just a little bit (8mm).
I wanted to start with a small reduction in trumpet length first so I could experiment in small stages.
The spacer already had the effect of moving the trumpets away from the plenum roof by 20mm so in total they are now 28mm further away from the roof and live in a plenum that has had its volume increased by half a litre.
The car is now a totally different animal, it runs sooo smoooooth and gear changes are much cleaner.
I cant comment on any power increases I may have added but I can defiantly say its a much easier and more enjoyable car to drive.
The engine fuels & breaths fantastically well all the way from idle to the very upper limits.
Because I can now grab the gears faster, get on the power earlier it feels faster and easier to drive faster.
Early tests seem to indicate its using less fuel too.
Perhaps a bit of a cheque-book cure to the problem but hope my ramblings help others with the same issues get their cars running better?
Regards, Dave.
You have probibly hit the nail on the head, as I think shunting caused by a series of things that boils down to a lean mixture and poor burn, and possibly poor cylinder filling on the longer duration cams at lower RPM, so as you have found improvements in any of these areas helps. Odd thing though my engine did it slightly on the catalysts map after porting the engine and fitting a 270' cam, but after fitting some decibel tubes to reduce the noise from my side pipes, the shunting dissapeared completely, so a bit more exhaust back pressure helped. Maybe less mixture was lost down the pipes at overlap with a bit more back pressure ???When I bought the car in the spring it had suffered from very little use and shunted quite badly until the engine spun over 2200rpm.
After about a 1000 miles of Shell Optimax/VPower fuel it started to get progressively better but at 3000 miles it had stopped improving and the shunting, although reduced, was still a pain.
Three weeks ago I replaced the leads, plugs and extenders, it got a bit better.
Number 8 lead shroud was badly burnt though, it was arcing on the exhaust manifold, so to be honest I had hoped for more of an improvement.
Last weekend I added the ACT smooth bore elbow & a K&N air filter, it got a lot better, actually it surprised me how much these relatively simple changes made to the throttle response.
Then yesterday I really went for it and fitted a SC-Power plenum spacer, heat insulating plenum base gasket, trumpet bell mouths and cut the trumpets themselves down just a little bit (8mm).
I wanted to start with a small reduction in trumpet length first so I could experiment in small stages.
The spacer already had the effect of moving the trumpets away from the plenum roof by 20mm so in total they are now 28mm further away from the roof and live in a plenum that has had its volume increased by half a litre.
The car is now a totally different animal, it runs sooo smoooooth and gear changes are much cleaner.
I cant comment on any power increases I may have added but I can defiantly say its a much easier and more enjoyable car to drive.
The engine fuels & breaths fantastically well all the way from idle to the very upper limits.
Because I can now grab the gears faster, get on the power earlier it feels faster and easier to drive faster.
Early tests seem to indicate its using less fuel too.
Perhaps a bit of a cheque-book cure to the problem but hope my ramblings help others with the same issues get their cars running better?
Regards, Dave.
Hi blitzracing,
Thanks for your comments, my methods were a bit hit and mis but fundamentally based on some old school theory.
At first I had looked at the Mark Adams chip but before spending the cash on fuelling I went back to basics.
I came to the conclusion the shunting was something to do with volumetric efficiency at low rpm, the Lucas fuel system seems to be pretty good at compensating for most conditions so I focused on the induction side.
It struck me that the induction side is more suited to Range Rover tasks, as I am not planning on driving the Chimaera up a muddy mountain I reasoned there could be some benefit in moving the peak torque further up the rev range.
I figured this would better suit a car weighing just over 1000kg thats fitted with a moderately aggressive cam profile.
Honestly the results are very pronounced, today I happily drove through central London on my way back home to Watford, something I would definitely avoid before my mods.
The car is so much more pleasurable to drive now, it just feels right, where before it made me feel tense driving at low rmp.
So next comes the pre-cat removal, the main cat stays retain sufficient back pressure.
Any tips on removing the pre-cats?
Nice website by the way.
dogbucket said:
So was that the SC Power complete kit @ £195?
Their photos seem a little confusing as to what you get in regards of the bell mouths, did it include the new pipes of various lengths to fit into the base plus the trumpet tops?
Their photos seem a little confusing as to what you get in regards of the bell mouths, did it include the new pipes of various lengths to fit into the base plus the trumpet tops?
Yep thats the kit, its the option four (last one in the list) titled "Plenum Spacer, Insulating gasket, extended bolts and Bell Mouth Trumpets".
It looks a bit confusing in the photo because the bell mouths are sat inside the insulating gasket.
I can not recommend this kit highly enough, it (along with the ACT elbow) transformed the way my Chimaera drives.
Ask away if you need any further advice. Dave.
dogbucket said:
thanks, so did you have to bake the base in the oven to get the old pipes out? So the new pipes are ready cut to length like the photo above the kit, then you lobbed another 8mm off first?
My only other thought is how they compare to the carbon superflare trumpets which cost twice as much but claim better gains, although I guess knowbody has done back to back testing.
My only other thought is how they compare to the carbon superflare trumpets which cost twice as much but claim better gains, although I guess knowbody has done back to back testing.
Your old pipes are retained, what you get are the bell mouths, which is why its cheaper than the ACT carbon trumpets.
The bell mouths are effectively rings with rolled edges that fit in top of your existing pipes.
You could argue that the ACT carbon trumpets are a more complete design as the SC-Power bell mouths are a mixture of your existing parts and some improved mouths.
You choose how much you want to shorten your existing pipes and then fit the bell mouths to the end of them.
When you look at your standard pipes you will see they actually already have the bell mouth shape, this is why they are known a trumpets.
But the standard trumpet mouths are not as close together or as big as when the SC-Power bell mouths are fitted.
Fitting the bell mouths and the shortening of trumpets can be done by Colin at SC-Power for £50 if you want to take some of the hassle out of the job.
I reasoned that the big advantage of the SC-Power kit over fitting the ACT trumpets is that you can reduce the pipe length in stages.
The ACT trumpets make a big jump in the length, I have no doubt this has been well tested but it is fixed.
The point is the shorter the trumpets are the further you move peak torque up the rev range.
I was looking to create a smooth linear power delivery right from idle so I have ended up with trumpets that are somewhere between the ACT trumpets and the standard ones.
Also for the same money as the ACT trumpets the SC-Power kit gives you the very useful plenum spacer and the heat insulating gasket.
I believe the plenum spacer played a big part in improving my throttle response, it not only increases the plenum volume but has the effect of bringing the trumpet mouths 20mm further away from the plenum roof.
Its a bit like shortening the standard trumpets by another 20mmm, but better, as you expand the plenum volume by 0.5 ltres at the same time.
The fitting of the SC-Power kit is very simple, Colin will send you some longer plenum bolts in the kit and I can talk you through the job if you need help.
I have had dealings with ACT and Tim is fantastically helpful and his parts are very well proven too.
So which ever way you choose to go I am sure you will see improvements, however I can only comment on the path I took and the result achieved on my particular car.
And believe me, the results were worth every penny.
Dave.
allanb said:
Chimpaholic said:
I have been suffering with a shunting problem on my Cimaera 4.0HC, I hope this will help others with a similar problem?...........
Hi Dave, At the risk of asking a stupid question. When you say shunting, do you mean the feeling that the car wants to keep moving forward while not pressing on the accelerator? Similar to incorrect timing?
This sounds awfully similar to my Chim, but mine is a non HC engine? at least i think it is!!!! Could the standard 400 engine have the same issue?
Chimpaholic said:
Last weekend I added the ACT smooth bore elbow & a K&N air filter, it got a lot better, actually it surprised me how much these relatively simple changes made to the throttle response.
Regards, Dave.
Secondly, sounds good about the smooth bore elbow, do you know why that elbow is more efficient than the standard item? Is it just the fact that the airflow is smoother along the silicone tube?Regards, Dave.
Cheers
Allan
As an ex-mechanic with a many years in the classic and vintage restoration world I would prefer to call it "hesitance".
Its more of a sensation, a feeling that would normally have me searching for an induction leak or a fuelling fault on the older stuff I am more familiar with.
Its doesn't exactly make the car un-drivable and you can get used to it, I just knew that with all that torque and a 4.0 litre V8 in such a light car things should be feeling much smoother.
The thing we need to understand is what TVR Power did to the the Range Rover engine, but more importantly what they didn't do.
The Range Rover setup is perfect for pulling a horse box or driving up a vertical slope at 4mph.
You need low down power to perform these tasks, so the induction side was carefully set up (by people who know what they are doing) accordingly.
A set of long induction tracts is what you need in the pony club world.
Then the well meaning guys at TVR Power got hold of the Range Rover lump and with a limited budget made some changes that better suit a sports car application.
I believe the problem is they only did half the job.
With a steeper cam profile and a different fuelling map they got some nice power improvements, but at the expense of drive-ability.
I bet they knew they could have done a better job too, but there is always a budget to work to in any business.
In fact from what I have seen TVR Power did do a crude job of cutting the trumpets down on the 5.0 litre cars to try and help.
I bet if you tried to run a 5.0 litre car on the standard Range Rover trumpets that you get in the 4.0 litre cars it would shunt like a b
h.I take no credit for the improvements I have made.
I just listened to all the advise & used my experience to filter out the bull.
All the trade guys I spoke to that seemed to be talking sense were saying the same thing "look at the induction side".
I figured the ones that know had spent many ours and lots of money getting to the answers, so I just followed the good advise of the true experts.
The results are unquestionably a monumental success.
If your RV8 TVR is hesitant at light to part throttle openings, if it makes you feel tense driving it below 2000/2300 rpm then just fit the parts I have added and you wont be diapointed.
Today I did some rolling acceleration tests to see what it could do:
4th Gear at 30mph which is roughly just 1200rpm and the car runs along without a single hicup.
Push on the throttle peddle and the car just accelerates from 30mph all the way until you feel 5th is needed.
If I had tried this before the mods, well lets just say it would have been a nasty experience.
Golflion said:
Fantastic,thought about this before but never got round to asking the question if it improves shunting in any way.
November is going to be a busy month,off road any way...
Hi Mark, I see you run a 4.0HC like me, let me know how you get on.November is going to be a busy month,off road any way...
If you want any fitting advise just shout.
I wouldn't mind betting you will love the results.
Best regards, Dave.
LordB said:
OK just got back after a 35 mile drive through town and country having fitted the kit which arrived this morning (many thanks to Chris at SC - great service). The kit came with the insulating gasket that fits under the plenum base to stop heat soak, a 20mm alu spacer ring that liftst the main plenum body to add more volume to the chamber, and 8 very good quality, billet milled trumpet heads that nicely slide over the top of the old trumpets after cutting, and new longer ss bolts. You will need some epoxy to fix these securly.
Generallyu had no problems with fitting at all - took me about 3hrs in all. But I was messing about with other bits and pieces as I went along. If your focussed should be able to manage it in a couple of hours. Also my plenum wasnt being particularly cooperative, some of the ancilliaries were being a pain, so decided to not remove the whole chamber off the car, just managed to pul it to one side whilst I slipped the trumpet base from underneath. I also decided to cut/mod the trumpets whilst still held in the base (I couldnt find my blow torch to loosen them enought to remove). I would recommend that you do, I had some trouble with cutting them to a precise level - had to spend half an hour afterwards with a file to square a couple up. I found a large hack saw with a new blade managed more than adequately.
I decided to only lower the trumpets by 5mm to give me some future options, should it not provide any noticeable improvements. Everything has come together and worked as it should - without any drama.
Now for the driving: After warming her up and even whilst I was doing, I noticed an immediate improvement in the throttle response, its very noticeable and I really like it. Once warm the car was ever so sweet, with the power and torque feeling much more creamy. These are to be expected with a car that is now breathing much much better than before. I headed for the centre of town to see if there was any improvement in the driveability in traffic. Whilst my 450 wasnt particularly troublesome, like others, I have noticed that at times its a little hesitant.....but isnt anymore, at least in 4th and 5th its very very smooth now. Not sure if its me though, but I think that I might have transfered a little of the old hesitance in 4/5th now into 3rd, but its not a big thing and I could be imagining it.
Having spent 30mins in town the car was fully up to temp so I headed for the hills and my favorite roads to open her up. There is a major improvement now in shifting through the gears particularly UP - in the lower gears. Whereas before I have sometime felt that I was not getting this right, I am now with much quicker and smooth changes off the line particularly. Have to say I not sure why there would be such a major difference - no doubt a techy out there will let me know.
OVerall I'd say the car is much much smoother, easier to drive, more enjoyable because I'm smoother in it. And given the earlier throttle pick up does feel quicker too.
I've posted some pics below. My verdict is, get one, you wont be dissapointed, however well set up you think your car is.
This is the finished trumpet and base - showing the 20mm alu ring spacer
Also a pic of the insulating gasket on the car.Also a pic of the base before the chamber was closed down.
Nice one LordB, same results as me then. Generallyu had no problems with fitting at all - took me about 3hrs in all. But I was messing about with other bits and pieces as I went along. If your focussed should be able to manage it in a couple of hours. Also my plenum wasnt being particularly cooperative, some of the ancilliaries were being a pain, so decided to not remove the whole chamber off the car, just managed to pul it to one side whilst I slipped the trumpet base from underneath. I also decided to cut/mod the trumpets whilst still held in the base (I couldnt find my blow torch to loosen them enought to remove). I would recommend that you do, I had some trouble with cutting them to a precise level - had to spend half an hour afterwards with a file to square a couple up. I found a large hack saw with a new blade managed more than adequately.
I decided to only lower the trumpets by 5mm to give me some future options, should it not provide any noticeable improvements. Everything has come together and worked as it should - without any drama.
Now for the driving: After warming her up and even whilst I was doing, I noticed an immediate improvement in the throttle response, its very noticeable and I really like it. Once warm the car was ever so sweet, with the power and torque feeling much more creamy. These are to be expected with a car that is now breathing much much better than before. I headed for the centre of town to see if there was any improvement in the driveability in traffic. Whilst my 450 wasnt particularly troublesome, like others, I have noticed that at times its a little hesitant.....but isnt anymore, at least in 4th and 5th its very very smooth now. Not sure if its me though, but I think that I might have transfered a little of the old hesitance in 4/5th now into 3rd, but its not a big thing and I could be imagining it.
Having spent 30mins in town the car was fully up to temp so I headed for the hills and my favorite roads to open her up. There is a major improvement now in shifting through the gears particularly UP - in the lower gears. Whereas before I have sometime felt that I was not getting this right, I am now with much quicker and smooth changes off the line particularly. Have to say I not sure why there would be such a major difference - no doubt a techy out there will let me know.
OVerall I'd say the car is much much smoother, easier to drive, more enjoyable because I'm smoother in it. And given the earlier throttle pick up does feel quicker too.
I've posted some pics below. My verdict is, get one, you wont be dissapointed, however well set up you think your car is.
This is the finished trumpet and base - showing the 20mm alu ring spacer
Also a pic of the insulating gasket on the car.Also a pic of the base before the chamber was closed down.
Edited by LordB on Saturday 31st October 15:33
The improvement in gear changes is uncanny isn't it.
I never would have believed my Chimaera could run so much better until I fitted the kit.
taylormj4 said:
Does the gasket that is replaced as part of the mod seal the plenum from air ingress ? If so, could the improvement that is being seen be simply down to the replacement of a leaky gasket below the plenum rather than the trumpets etc.
Shunting for me (450) is the power going on-off-on-off-on.... whilst at light throttles, as if you were gently and constrantly blipping the throttle. There is also a hesitation when you then accelerate out of this situation.
Cheers, Matt
Hi, there is no gasket fitted as standard.Shunting for me (450) is the power going on-off-on-off-on.... whilst at light throttles, as if you were gently and constrantly blipping the throttle. There is also a hesitation when you then accelerate out of this situation.
Cheers, Matt
The purpose of fitting the one supplied by SC-Power is to reduce the heat soak from the engine into the plenum.
The gasket is made from an insulating material, more of a heat shield than a sealing gasket in the traditional sense.
Reducing the temperature of inducted air increases its volume.
Dave.
taylormj4 said:
I see. Thanks for that.
Have been thinking that my shunting was due to an air leak causing it to run lean. What makes me think this is that when I close the throttle to change gear, the revs only die very slowly as if there is air getting in somewhere. No idea where to start looking though.
Have done lots of work on Land Rover engines but a bit more scared playing around with the TVR as it's worth a lot more and is my daily driver so can't afford for it to be off the road for long.
Cheers, Matt
Actually you are probably on to something with your air leak theory.Have been thinking that my shunting was due to an air leak causing it to run lean. What makes me think this is that when I close the throttle to change gear, the revs only die very slowly as if there is air getting in somewhere. No idea where to start looking though.
Have done lots of work on Land Rover engines but a bit more scared playing around with the TVR as it's worth a lot more and is my daily driver so can't afford for it to be off the road for long.
Cheers, Matt
In simple terms your idle speed is effectively controlled by a managed bleed of air into the back of the plenum.
This duty is completed by the stepper motor, before you splash out on the SC-Power kit that I suggest you remove & clean the stepper motor.
There are plenty of posts on here about how best to clean it, just do a quick search.
Or click here for a great article with pictures:
http://www.tvrcc-south-wales.co.uk/stepper.asp
After you have solved the stepper motor operation and your idle is under control, I still recommend fitting the SC-Power kit as it will improve the throttle response significantly if my experiences are anything to go by.
Best regards, Dave.
taylormj4 said:
Chimpaholic said:
taylormj4 said:
I see. Thanks for that.
Have been thinking that my shunting was due to an air leak causing it to run lean. What makes me think this is that when I close the throttle to change gear, the revs only die very slowly as if there is air getting in somewhere. No idea where to start looking though.
Have done lots of work on Land Rover engines but a bit more scared playing around with the TVR as it's worth a lot more and is my daily driver so can't afford for it to be off the road for long.
Cheers, Matt
Actually you are probably on to something with your air leak theory.Have been thinking that my shunting was due to an air leak causing it to run lean. What makes me think this is that when I close the throttle to change gear, the revs only die very slowly as if there is air getting in somewhere. No idea where to start looking though.
Have done lots of work on Land Rover engines but a bit more scared playing around with the TVR as it's worth a lot more and is my daily driver so can't afford for it to be off the road for long.
Cheers, Matt
In simple terms your idle speed is effectively controlled by a managed bleed of air into the back of the plenum.
This duty is completed by the stepper motor, before you splash out on the SC-Power kit that I suggest you remove & clean the stepper motor.
There are plenty of posts on here about how best to clean it, just do a quick search.
Or click here for a great article with pictures:
http://www.tvrcc-south-wales.co.uk/stepper.asp
After you have solved the stepper motor operation and your idle is under control, I still recommend fitting the SC-Power kit as it will improve the throttle response significantly if my experiences are anything to go by.
Best regards, Dave.
Have had the stepper out a couple of times and cleaned it. Never looked particularly dirty. Cleaned the housing too. The only difference this seemed to make was on occasion when changing gear, the revs would drop dramatically quickly and almost cause a stall, certainly not a smooth gear change. After a few days it would be back to normal again.
Matt
Its still possible the stepper motor isn't cycling correctly and needs replacing, or you may need to look at your throttle position sensor.
In fact I could probably make a list for you; servo vac pipe, throttle pos sensor, stepper motor, ECU temp sender, throttle return spring, throttle cable, ECU fault, Lamda sensor, ect, ect, ect.
To be honest without seeing the car this is where we all just start guessing.
I am never a big fan of trying to diagnose a problem via a chat on a forum, its essential to see and check everything in the flesh to make an accurate diagnosis.
Your diagnosing process needs to be systematic and must start at the beginning by making sure the basics are all 100% correct first.
We all like to fix our cars ourselves but sometimes you have to bite the bullet and put the car in the hands of a specialist with the right knowledge, experience & equipment to get to the bottom of a problem quickly.
A bad TVR specialist will make a series of informed guesses just like my list above.
He will replace components one by one at your cost that he assumes may be the cause.
If the bad TVR specialist gets lucky he may find the problem quickly using this process, but there is no telling how much of your money he will spend replacing perfectly serviceable parts in the blind pursuit of a solution.
Find a good TVR specialist who knows his stuff and has the correct kit (fault code reader ect) and you will save money every time.
Sorry I cant offer more help but I suspect your problem will turn out to be an easy cheap fix, ultimately its the time someone takes to find the fault that costs the money.
Good luck and let us all know how you get on.
Best regards, Dave.
taylormj4 said:
blitzracing said:
The stepper should not be coming into play with the car moving, as the ecu has a speed sensor input that disables it. Try unplugging the stepper when the engine is idling nicely and warm (yes with the engine running), and take it for a run, and see the effect. You will have problems getting the car to run when cold if you leave the stepper disconected so its just a test. Mucky steppers can cause the cars idle to be erratic, too low or too high, but cleaning just the cone is only half the story, as the keyway behind the cone also gets mucked up. Its possible to get it out with some skullduggery, or another idea is to undo the stepper almost all the way on its thread, (engine stopped), and then replug it and start the engine. It will now rev too high, and the stepper will push the cone out further than normal to account for the extra distance its screwed out to reduce the tickover. Then DISCONNECT the stepper before you stop the engine, so it remains out. Otherwise it will wind in again as you turn the ignition off. This may give you enough extra movement to get behind the spring and clean the keyway. Dont try doing this- it was a scrap unit!
Blitz,You're correct about the speed sensor. If I put the car into neutral as I am rolling to a stop, the revs stay high (only a very gradual decay) until the car comes to an absolute stop and it is an absolute stop, then the revs gradually step down to normal idle or high-idle if engine is cold. So if it does it when the car is rolling, stepper motor is not the problem, so no point in looking there ?
Matt
Dave,
Makes sense what you say. I do like fixing my own car, plus I am an electrical engineer, so it pains me that I cannot get the information to be able to test all of these sensors. It would certainly annoy me if someone just replaced things until they found the fault.
I could do with a list of resistance ranges for the sensors etc. The car has been on a fault reader previously and lambda sensors all Ok. I suppose I may just have to give in and take it to a "good TVR specialist" - any recommendations ?
Matt
Edited by taylormj4 on Tuesday 10th November 11:03
Edited by taylormj4 on Tuesday 10th November 11:03
I am merely an ex-mechanic, my speciality in the day was very vintage and classic focused, so while I will happily build you a 1932 Wilson Pre-Selector gearbox there are others that are better placed to advise you on the TVR fuelling side.
I am still having lots of fun learning my way around my Chimaera and will be following this thread as I too have a very slight raised idle issue (idles at 1300 rpm for 3 seconds after a long hot run then settles to 1000 very quickly so no biggy).
On the subject of a good specialist I can thoroughly recommend Jason at Str8six, at first he seems focussed on the AJP6 cars but he is ex-factory and knows them all inside out.
He also has a great team of ex-factory guys with a combined no-bull knowlege of all things TVR that has to be respected.
They had my Chim on the ramp and we went through the car together, within 15 minutes they had given me a list of minor jobs to get stuck into.
The way they went straight to the faults was really impressive, in my opinion this type of expertise can only come from years of working on one breed.
It also looks like Austec Racing have a dream team of guys that I recognise and respect from my classic racing days, you don't get more legendary than David Vizard in my book.
Take a look at the kit Austec have, a massive investment including a fully equipped machine shop and rolling road.
However as you are an electrical engineer your approach and knowledge, combined with the right advise on this forum, may just be the combination needed to resolve the problem yourself.
Good luck mate and let us all know how you get on.
Best regards, Dave.
STEV8E said:
Just come back to this after my post at the beginning which now seems a bit abrupt and dismissive. Anyhow having had a good read it all sounds very interesting.
I had fairly bad low speed shunting (I am talking about in traffic) and a slight hesitancy at mid throttle until I did a full decat, removing the precats and fitting "Clive's Y Piece". This did totally eradicate all shunting and the car has been much more responsive throughout the rev range. And loud!
I have just put the main cat back on after five months shunt free driving to get the car through the MOT and guess what... slight hesitancy at mid throttle is back, however at low speed the car is still fine.
So in my case it would appear that low speed shunting is caused by the restrictive nature of the precats and the hesitancy at higher speed is cause by the main cat.
I am now wondering how the car would drive with all the cats removed and the induction sorted.
Well my pre-cats are coming out soon, I have a slight blow on warm up from the O/S manifold to Y piece join.I had fairly bad low speed shunting (I am talking about in traffic) and a slight hesitancy at mid throttle until I did a full decat, removing the precats and fitting "Clive's Y Piece". This did totally eradicate all shunting and the car has been much more responsive throughout the rev range. And loud!
I have just put the main cat back on after five months shunt free driving to get the car through the MOT and guess what... slight hesitancy at mid throttle is back, however at low speed the car is still fine.
So in my case it would appear that low speed shunting is caused by the restrictive nature of the precats and the hesitancy at higher speed is cause by the main cat.
I am now wondering how the car would drive with all the cats removed and the induction sorted.
Edited by STEV8E on Friday 13th November 18:34
So I figure if I need to do some work in that area anyway I may as well remove the pre-cats while I'm at it.
I know I'm a sucker for punishment, who need skin on their knuckles anyway?
So looking at this from the other way I will be able to report on any additional improvements to my very successful induction mods by freeing up the exhaust side too.
The main cat stays in for now as I expect a bit a back pressure will help with cylinder scavenging, plus I don't need the potential MOT hassles in Feb 2010.
I have to say I am very happy with the way things are going so far, from what I have heard, with the pre-cats removed I should enjoy even better throttle response.
I will report on my findings as soon the job is complete.
Dave.
TVR Beaver said:
Hi Guy’s.. Sorry to come in late on this one.. but maybe you could offer me some advice here… I’ve spent a fortune and my car is not behaving like it was….
I apportion no blame here (except myself) and I’m not criticising any parts used (already been flamed on that one!).. but what I’ve ended up with is not what I set out to do… and I’m a lot poorer to boot!!
It all started a couple of months ago.. I had my 500 Griff (cat) at V8D for the White metal shells doing… Whilst in there I asked them to look at the cam and they said it was starting to show signs of tip’s going… so I thought I may as well have it done..
Before, my car was standard, with the exception of pre-cat’s out and the silencer opened up a bit and showed 280 BHP at the Growl.. a nice healthy engine…
Shunting was not a problem although at times I could feel a bit when in 3rd gear crawling in traffic.
Anyway.. I had a Stealth cam fitted and some induction mod’s… 72mm Plenum, Trumpet base. smooth bore 90* and ported manifold…45mm I think
When I got it back, the shunting was more pronounced so I took it back.. they tested her out and said it was running very lean and I’d have to get it on the rollers….
So enter Mark Adams… Great guy and very knowledgeable… He suggested I fit red top’s, Bosch MAF.. move the vac pipe forward a bit (so 2K when it comes in),,, Improve the induction pipe.. fit a K and N etc… We also replaced the plugs, coil and HT leads, Pot… and set it all up… end result is… it still shunts….
Although in other areas it’s much better now (fueling)… my power has moved up the RPM band so not as aggressive off the mark… but goes for ever on the top end… Problem is… driving in town is a sod….
I have a 10mm spacer fitted also but was thinking of trumpet length or may be even the manifold as it appears they close it down at the heads over the standard one to get faster flow… maybe it’s worth opening this up again?.. Mark did say he thinks a lot of the issue is due to my heads having big ports?? It did appear to get a bit worst when I fitted the spacer for some reason?
So all in I’m about £3.5K out of pocket and have a car I’m not keen on driving now (Wish I could go back) and a BHP of 294 and a slight drop in the torque.. …
Not sure what the cam will do over standard but the V8D guy’s say it should be fine.. so suggest it’s on the induction side…
Any thoughts would be appreciated… Cheers…
I apportion no blame here (except myself) and I’m not criticising any parts used (already been flamed on that one!).. but what I’ve ended up with is not what I set out to do… and I’m a lot poorer to boot!!
It all started a couple of months ago.. I had my 500 Griff (cat) at V8D for the White metal shells doing… Whilst in there I asked them to look at the cam and they said it was starting to show signs of tip’s going… so I thought I may as well have it done..
Before, my car was standard, with the exception of pre-cat’s out and the silencer opened up a bit and showed 280 BHP at the Growl.. a nice healthy engine…
Shunting was not a problem although at times I could feel a bit when in 3rd gear crawling in traffic.
Anyway.. I had a Stealth cam fitted and some induction mod’s… 72mm Plenum, Trumpet base. smooth bore 90* and ported manifold…45mm I think
When I got it back, the shunting was more pronounced so I took it back.. they tested her out and said it was running very lean and I’d have to get it on the rollers….
So enter Mark Adams… Great guy and very knowledgeable… He suggested I fit red top’s, Bosch MAF.. move the vac pipe forward a bit (so 2K when it comes in),,, Improve the induction pipe.. fit a K and N etc… We also replaced the plugs, coil and HT leads, Pot… and set it all up… end result is… it still shunts….
Although in other areas it’s much better now (fueling)… my power has moved up the RPM band so not as aggressive off the mark… but goes for ever on the top end… Problem is… driving in town is a sod….
I have a 10mm spacer fitted also but was thinking of trumpet length or may be even the manifold as it appears they close it down at the heads over the standard one to get faster flow… maybe it’s worth opening this up again?.. Mark did say he thinks a lot of the issue is due to my heads having big ports?? It did appear to get a bit worst when I fitted the spacer for some reason?
So all in I’m about £3.5K out of pocket and have a car I’m not keen on driving now (Wish I could go back) and a BHP of 294 and a slight drop in the torque.. …
Not sure what the cam will do over standard but the V8D guy’s say it should be fine.. so suggest it’s on the induction side…
Any thoughts would be appreciated… Cheers…
Hi TVR Beaver sorry to hear about your plight, sounds like you have had some good brains on the problem already.
I would say it must have something to do with how the air is passing down the inlet tracts, it may be pulsing or moving too slowly in the lower RPM bracket.
When tuning for power most people focus solely on the more air more fuel approach.
Its as important, if not more important, to understand how the air is flowing at different RPMs and how this also effects fuel atomization and cylinder filling.
Five years ago I had the pleasure of seeing some software simulating all this at the former BAR HQ in Brackley.
I may also be able to put you in touch with a couple of ex-Lotus development engineers that have just completed some similar modeling on a 1933 Talbot 75 special a friend is building.
They have used their software (In-part) to help extract 173 HP from a naturally aspirated pre-war 2.5 litre straight six and it fuels perfectly from 800rpm to over 5000rpm.
Short of reversing your mods one option that I wouldn't mind betting would solve your problem is forced induction.
The problem is you will probably need to throw a minimum of £4k at it to get a decent supercharger installation.
The Lotus guys are available but certainly not cheap, you may find yourself spending as much as a blower installation, let me know if you need and introduction.
Dave.
TVR Beaver said:
Thanks Dave's,,, for the offer and info... Spending more on the car is not an option if I'm to retain all my bodily bits so the wife tell's me... and I did want to keep it kind of standard (what happened to that!!).
One thing that was of interest on the rollers was a loaded run as if your going up a slight hill and then stop.. it showed the cylinders to be fueling differantly at the 1800 RPM point, so I'm sure your right on the air flow / air waves / movement in the plenum etc... but trying to think which part has caused it... Creating a bigger gap over the trumpets with the spacer appeared to make it shunt more so I will try with that removed... but if I get into re-sizing the trumpets on length I need to understand a bit more about how they function...
My car does run a bit cold also so I need to try it with a new stat to ensure I hold 80 deg or so..
Just a tad annoying going from a £200 bearing replacement to a £3.5K upgrade and ending up with 10 BHP and a shunter....
It was more apperant after the V8D work so if it's not the cam (and people say it won't be?)... It can only be the Trumpets or the manifould?... but which one... and what to do first??.. The joy's..
Indeed our women folk can be the biggest barrier to performance improvements, I have the same issues this end.One thing that was of interest on the rollers was a loaded run as if your going up a slight hill and then stop.. it showed the cylinders to be fueling differantly at the 1800 RPM point, so I'm sure your right on the air flow / air waves / movement in the plenum etc... but trying to think which part has caused it... Creating a bigger gap over the trumpets with the spacer appeared to make it shunt more so I will try with that removed... but if I get into re-sizing the trumpets on length I need to understand a bit more about how they function...
My car does run a bit cold also so I need to try it with a new stat to ensure I hold 80 deg or so..
Just a tad annoying going from a £200 bearing replacement to a £3.5K upgrade and ending up with 10 BHP and a shunter....
It was more apperant after the V8D work so if it's not the cam (and people say it won't be?)... It can only be the Trumpets or the manifould?... but which one... and what to do first??.. The joy's..
I've built many engines from mild to wild, mostly pre-war stuff, no RV8's although the fundamental principles of any four-stroke are always the same.
In my experience its never as simple as finding which part is giving you a certain characteristic.
Its all about the relationship between a number of components, finding the right combination is the difficult part.
With a common engine like the RV8 you will be sure to find that others have done this hard work already, its essentially a recipe.
That's why its always much easier to build an engine from the crank up with a clear brief right from the start, you just follow a known recipe to get a known result.
My early findings lead me to think the RV8 responds well to changes in the length of the inlet tracts.
Without the induction/exhaust modeling software and accesses to a rolling road its a case of experimenting with different lengths of velocity stacks (sorry that's trumpets in the RV8 world).
I just guessed with my mods which is appalling practice, but I did get lucky.
A great option would be to source a spare plenum base and some tubing so you can alter the trumpet lengths until you find a nice match with you cam profile.
In simple terms shortening the trumpets should push the peak torque further up the rev range, but adding in other variables its really more complicated than that.
Ideally what you want and need to see could only be shown on a 3D graph.
For example an F1 engine will have variable inlet and exhaust tracts that shorten or lengthen by following a map after the processing of sensor data by an ECU.
In practice on the simple old RV8 you need to find the best relationship between inlet tract length and your cam, exhaust side, ect, ect.
I bet someone here has the same cam as you and a similar setup, try creating a post to see if anyone has found a good combination.
Sorry I cant be of more help.
Kind regards and good luck. Dave.
spend said:
All sounds brilliant... but the EFi manifold does not have anything like equal inlet tracts so its pretty much a load of rubbish.
Long trumpets (ie extended port volume) may just keep cross contamination on overlap to a minimum. Are you sure it isn't pathetic throttle response due the increased plenum volume that you are experiencing?
You could ask Rob if it is worth advancing your cam? I'd try it if it was my problem and nothing else worked.
Long trumpets (ie extended port volume) may just keep cross contamination on overlap to a minimum. Are you sure it isn't pathetic throttle response due the increased plenum volume that you are experiencing?
You could ask Rob if it is worth advancing your cam? I'd try it if it was my problem and nothing else worked.
Cant remember saying anything abut the inlet tracts being equal?
I am more basic principles than rubbish.
Lets all get on here shall we.
Well I'm back.
As I started all this I thought I better let you all know I have been following with great interest.
Its great to see the subject has sparked so much interest.
The statement that interests me the most was from Mark.
"It is highly beneficial (as a rule of thumb) to have approximately the same distance between the end of the trumpet and the underside of the plenum, as the diameter of the trumpet"
I expect the plenum spacer helped greatly to bring this relationship closer to where it needs to be on my car.
The point of reverse flow of exhaust gas up the inlet tract and the theory that this is worse on an engine that runs a higher lift cam also sounds right to me.
My car is a 4.0HC, the HC gave you a wilder cam and Chimaers thus equipped had a reputation for shunting.
My car was no exception.
However since solving my shunting and creating a much smoother and more pleasurable power delivery I have moved my attentions to improving the fuel economy.
It is clear to me the RV8 does not fuel efficiently between the idle and 2600 rpm range.
As the engine comes on cam everything seems to come together.
At 3000rpm the economy is actually quite respectable for a four litre engine with eight mouths to feed.
I am seeing 28mpg at a steady 80mph in fifth.
I put the poor lower rpm economy down to three things.
1. Induction interference between the trumpets
2. Exhaust gas contamination
3. Rather basic ignition control provided by a distributor using bob weights and bob weight springs
I also think TVR set the fuelling to provide best acceleration off the line.
When driving in the city you are often stopping at traffic lights and then accelerating away, in these conditions I am seeing 13-15mpg.
Although I have my own plans to improve lower rpm fuel efficiency, before I implement them, I welcome your thoughts and ideas.
Thanks all, Dave.
As I started all this I thought I better let you all know I have been following with great interest.
Its great to see the subject has sparked so much interest.
The statement that interests me the most was from Mark.
"It is highly beneficial (as a rule of thumb) to have approximately the same distance between the end of the trumpet and the underside of the plenum, as the diameter of the trumpet"
I expect the plenum spacer helped greatly to bring this relationship closer to where it needs to be on my car.
The point of reverse flow of exhaust gas up the inlet tract and the theory that this is worse on an engine that runs a higher lift cam also sounds right to me.
My car is a 4.0HC, the HC gave you a wilder cam and Chimaers thus equipped had a reputation for shunting.
My car was no exception.
However since solving my shunting and creating a much smoother and more pleasurable power delivery I have moved my attentions to improving the fuel economy.
It is clear to me the RV8 does not fuel efficiently between the idle and 2600 rpm range.
As the engine comes on cam everything seems to come together.
At 3000rpm the economy is actually quite respectable for a four litre engine with eight mouths to feed.
I am seeing 28mpg at a steady 80mph in fifth.
I put the poor lower rpm economy down to three things.
1. Induction interference between the trumpets
2. Exhaust gas contamination
3. Rather basic ignition control provided by a distributor using bob weights and bob weight springs
I also think TVR set the fuelling to provide best acceleration off the line.
When driving in the city you are often stopping at traffic lights and then accelerating away, in these conditions I am seeing 13-15mpg.
Although I have my own plans to improve lower rpm fuel efficiency, before I implement them, I welcome your thoughts and ideas.
Thanks all, Dave.
Ozmira said:
BliarOut said:
Crap tank of fuel?
it was bp fuel and I've filled up since Monday may have to start with the ecu but again don't know what to look for. It's a start though. For instance, something like the coolant temperature sensor that the ECU reads to alter mixture on cold start.
You may have one of a number of faults or a few of them so I also would start by looking at the plug colours just as blitzracing is telling you.
The plug colour can tell a thousand stories.
Then, if you can, get it checked with an ECU fault code reader, it can save hours of guess work.
I wouldn't eliminate something simple like a partially blocked fuel filter or an HT lead that's breaking down.
The thing is its almost impossible to correctly diagnose a fault like this on a forum.
If you are not confident with engine fault diagnostics you really need the services of a good mechanic with diagnostic equipment and ideally knowledge of the TVR/Range Rover fuel system.
A bad mechanic will just replace components until he stumbles on a fault, a good mechanic will diagnose the faulty component and get you sorted much quicker a for less money.
I really hope you find the fault mate, like I say its almost certainly something simple.
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