Shunting Solved

[Milky400]

LordB said:

Just ordered the same SC-Power kit. Should be here by Saturday (subject to the PO boys getting back to work!).
Will post how I get on later.
R

would be interested to know, mine shunts a gooden low down

[Del 203]

I thought all these shunting problems were on 500's not drivable 400/450's

& no, no shunting on mine

[Golflion]

Chimpaholic said:

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.

If you want any fitting advise just shout.

I wouldn't mind betting you will love the results.

Best regards, Dave.

Cheers Dave will probably need to get in touch when it comes to the trumpet setting.

Lord B
Please let me know how you get on.

[LordB]

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.

Edited by LordB on Saturday 31st October 15:33

[Milky400]

thanks for the advice, not running the car over winter so it will give me something to spend my spare fuel cash on and waste 3 hours of the next 6 months!!

[Chimpaholic]

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.

Edited by LordB on Saturday 31st October 15:33

Nice one LordB, same results as me then.

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.

[LordB]

[/quote=Chimpaholic]
Nice one LordB, same results as me then.

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.

[/quote]
Maybe somoene out there could explain why that is??

[Golflion]

LordB said:

[/quote=Chimpaholic]
Nice one LordB, same results as me then.

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.

Maybe somoene out there could explain why that is??

I can't wait to do all the basic mods....bring it on!!!!

[taylormj4]

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

[Chimpaholic]

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.

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.

[LordB]

Chimpaholic said:

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.

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]

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

[Chimpaholic]

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.

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.

[LordB]

"....... it will improve the throttle response significantly if my experiences are anything to go by"

thats been my experience too.

[AlRaven]

I've bought the plenum spacer and heat gasket without trumpets and was about to fit it until I read this - however there seems to be a lot of choice trumpetwise. What's the best route for general driveability improvement? I've got the shunting but it's not that bad, so I'm wondering if I'd see much improvement with the trumpets?

P.S. What's the torque setting for the plenum bolts?

[taylormj4]

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.

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.

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

[Chimpaholic]

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.

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.

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

Hmmm that's a shame the cleaning didn't solve your problem.

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.

[blitzracing]

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!

Edited by blitzracing on Monday 9th November 19:56

[taylormj4]

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

[Chimpaholic]

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

Hi Matt, I think Blitz is your man to advise you here, he has lots of experience on the TVR RV8 setup.

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.