Mismatch fix needed
Discussion
As per my thread hyjack... sorry Neal.
Long story short,
I have a TVR 4.6 RV8 that has been completely rebuilt.
The aim is to fit a turbo or 2 in the future but i need to get it running to a driveable standard asap in order to attend an event at Santa pod that i have arranged on the 9th July.
The car is running.... somehow but is suffering from a mismatch of cam and a low CR of 8:1.
The engine is fitted with ceramic coated, thick ringland, forged pistons.
Heads are fully ported and fitted with bronze guides and double valve springs.
The cam is a high lift and duration solid lifter with adjustable pushrods and is far too big for the engine.
So i need recommendations as to a suitable cam that can get me running.
If it still works with the turbos fitted later then all the better.
All other abuse, ideas and recommendations will be taken and appreciated.
Long story short,
I have a TVR 4.6 RV8 that has been completely rebuilt.
The aim is to fit a turbo or 2 in the future but i need to get it running to a driveable standard asap in order to attend an event at Santa pod that i have arranged on the 9th July.
The car is running.... somehow but is suffering from a mismatch of cam and a low CR of 8:1.
The engine is fitted with ceramic coated, thick ringland, forged pistons.
Heads are fully ported and fitted with bronze guides and double valve springs.
The cam is a high lift and duration solid lifter with adjustable pushrods and is far too big for the engine.
So i need recommendations as to a suitable cam that can get me running.
If it still works with the turbos fitted later then all the better.
All other abuse, ideas and recommendations will be taken and appreciated.
I'm not sure why you need to do anything? Ok, with a low CR, it isn't going to be making very good use of the high rpm breathing capabilites of the cam (and hence not making a huge specific output) And the poor charge motion at part load may result in a fairly retarded ignition timing to avoid detonation (slow burn rate, MBT/BLD ignition well advanced from TDC). But, assuming your have a mappable ECU it will run!
(if it isn't running, then either 1) your mappings a pile of p**, or 2) something is broken ;-)
(if it isn't running, then either 1) your mappings a pile of p**, or 2) something is broken ;-)
TVR tweaked standard ECU with a Torqueflow chip and AFM.
It ran very well on the standard engine. Fuelling was spot on and gave me 273bhp NA before i destroyed my engine due to nitrous greed and misuse.... but thats another story.
This set up can not be tuned to such a wild cam but should be doable on a milder or standard cam.
I am ordering a megasquirt package as we speak but it cant be supplied, fitted and tuned in time.
It ran very well on the standard engine. Fuelling was spot on and gave me 273bhp NA before i destroyed my engine due to nitrous greed and misuse.... but thats another story.
This set up can not be tuned to such a wild cam but should be doable on a milder or standard cam.
I am ordering a megasquirt package as we speak but it cant be supplied, fitted and tuned in time.
dbv8 said:
As per my thread hyjack... sorry Neal.
Long story short,
I have a TVR 4.6 RV8 that has been completely rebuilt.
The aim is to fit a turbo or 2 in the future but i need to get it running to a driveable standard asap in order to attend an event at Santa pod that i have arranged on the 9th July.
The car is running.... somehow but is suffering from a mismatch of cam and a low CR of 8:1.
The engine is fitted with ceramic coated, thick ringland, forged pistons.
Heads are fully ported and fitted with bronze guides and double valve springs.
The cam is a high lift and duration solid lifter with adjustable pushrods and is far too big for the engine.
So i need recommendations as to a suitable cam that can get me running.
If it still works with the turbos fitted later then all the better.
All other abuse, ideas and recommendations will be taken and appreciated.
Have you given up using NOS, or did you just forget to mention it?Long story short,
I have a TVR 4.6 RV8 that has been completely rebuilt.
The aim is to fit a turbo or 2 in the future but i need to get it running to a driveable standard asap in order to attend an event at Santa pod that i have arranged on the 9th July.
The car is running.... somehow but is suffering from a mismatch of cam and a low CR of 8:1.
The engine is fitted with ceramic coated, thick ringland, forged pistons.
Heads are fully ported and fitted with bronze guides and double valve springs.
The cam is a high lift and duration solid lifter with adjustable pushrods and is far too big for the engine.
So i need recommendations as to a suitable cam that can get me running.
If it still works with the turbos fitted later then all the better.
All other abuse, ideas and recommendations will be taken and appreciated.
The issue with AFM sensing on a "Hot" cam setup is reverse flow and pressure fluctations etc
Flap type meters are hopeless due to their mechanical inertia, and Hotwire types need to be set up and calibrated to ignore the reverse flows etc
Does your AFM adaptor box convert a MAP or TPS signal into a psuedo AFM one??
If so, the system should be compatable with a hairy cam. Also, what ignition control are you using? Dissy or coil packs, mapped or not??
Flap type meters are hopeless due to their mechanical inertia, and Hotwire types need to be set up and calibrated to ignore the reverse flows etc
Does your AFM adaptor box convert a MAP or TPS signal into a psuedo AFM one??
If so, the system should be compatable with a hairy cam. Also, what ignition control are you using? Dissy or coil packs, mapped or not??
Planning even more changes when as yet you don't even know if the base engine really is sound strikes me as pointless. Get it on the rollers briefly to find out if it even runs properly, get an idea of what sort of output it has now and then at least you have a baseline to make some sensible decisions from.
What you've never indicated despite it being the most important part of the equation is what the car is used for. Is it a road car, purely a drag one, do you tow it around or drive it around, what tractability requirement do you have? How can anyone advise without knowing all this?
What you've never indicated despite it being the most important part of the equation is what the car is used for. Is it a road car, purely a drag one, do you tow it around or drive it around, what tractability requirement do you have? How can anyone advise without knowing all this?
spend said:
Just stick a cheap LR Cam in & dose it to your delight whilst you do the other things..
I might even have a set of usable cam + followers laying around that will give you breathing space if you want.
Or real steels turbo jobbie is cheap enough.I might even have a set of usable cam + followers laying around that will give you breathing space if you want.
That could be an option Dave thanks. You havent give me a price for the other bits yet! PM me and i will square up.
I still have my old cam in good nick. 435 IIRC. I did have the followers kept in order but a certain somebody emptied them into a box of my other old parts for no apparent reason.
Pumaracing said:
Planning even more changes when as yet you don't even know if the base engine really is sound strikes me as pointless. Get it on the rollers briefly to find out if it even runs properly, get an idea of what sort of output it has now and then at least you have a baseline to make some sensible decisions from.
What you've never indicated despite it being the most important part of the equation is what the car is used for. Is it a road car, purely a drag one, do you tow it around or drive it around, what tractability requirement do you have? How can anyone advise without knowing all this?
Good idea, i will be picking the car up on a trailer next Friday. I will look to see if there is a RR en-route from Clitheroe to Barrow. What you've never indicated despite it being the most important part of the equation is what the car is used for. Is it a road car, purely a drag one, do you tow it around or drive it around, what tractability requirement do you have? How can anyone advise without knowing all this?
Does anybody know somewhere suitable?
If i only planned to use the car for racing i would have said.
The insurance is set for 5000miles and i will probably use close to that in the year. Some shows and meets, driving to the drag strips and the odd Sunday afternoon up the lakes etc. I can cope with a level of undriveability that would not suit most owners.
Hi Derek,
Have you double checked the compression with a different gauge?
Isn't the Torque flow AFM designed around a standard engine? Maybe causing issues,if you still have it bang on the standard one see if helps
As Dave said if Rob specced your Cam speak to him first before spending anymore money on rolling roads, just to put your mind at rest that you have the cam that he specced, if not you'll know where to start
just my 2pence worth,
Have you double checked the compression with a different gauge?
Isn't the Torque flow AFM designed around a standard engine? Maybe causing issues,if you still have it bang on the standard one see if helps
As Dave said if Rob specced your Cam speak to him first before spending anymore money on rolling roads, just to put your mind at rest that you have the cam that he specced, if not you'll know where to start
just my 2pence worth,
It's been a long time since I had any dealings with Kent Cams but I've been looking at the Rover offerings on their website for your application. Trying to pick cams based on seat durations is a completely unreliable method and for many years I've used the duration at 1mm lift as used by Catcams to get a proper idea of what the profile is doing. Similarly the Americans have used 0.050" lift duration figures for decades.
Sadly British companies continue to stick to fairly meaningless seat durations which tell you nothing about how fast the valve actually opens or how tractable the profile will be but even so the Kent specs for the Rover V8 are more bizarre than I was prepared for. The H224 is a road profile supposed to pull from 2000 rpm. The M256 is full race and doesn't pull until 4000 rpm. Astonishingly they claim identical seat durations of 304 degrees inlet and 310 exhaust. Put the part numbers in the search box and see.
http://www.kentcams.com/
How anyone is meant to make sense of that is beyond me. The fact that one cam is hydraulic and the other solid lifter shouldn't make any great difference if a proper duration measure is used. Based on this you can hopefully see why it's such a lottery trying guess how your current cam is likely to behave, what to replace it with or how Kent Cam's profiles compare to anyone else's.
Only when enough people take their custom elsewhere and explain why is this practice likely to stop. I'm not holding my breath.
Sadly British companies continue to stick to fairly meaningless seat durations which tell you nothing about how fast the valve actually opens or how tractable the profile will be but even so the Kent specs for the Rover V8 are more bizarre than I was prepared for. The H224 is a road profile supposed to pull from 2000 rpm. The M256 is full race and doesn't pull until 4000 rpm. Astonishingly they claim identical seat durations of 304 degrees inlet and 310 exhaust. Put the part numbers in the search box and see.
http://www.kentcams.com/
How anyone is meant to make sense of that is beyond me. The fact that one cam is hydraulic and the other solid lifter shouldn't make any great difference if a proper duration measure is used. Based on this you can hopefully see why it's such a lottery trying guess how your current cam is likely to behave, what to replace it with or how Kent Cam's profiles compare to anyone else's.
Only when enough people take their custom elsewhere and explain why is this practice likely to stop. I'm not holding my breath.
But in it's simplest form.
Stick with what is a mild cam, and you'll nearly always have a safe choice. Especially for a boosted engine.
Go for a "big" cam, and there may be potential for some gains up top, but at the risk of massive losses low down.
I have used Real Steel's Typhoon in conjunction with Rhoads lifters very successively with boost. Also Rovercrafts old RC87 worked well.
I also had a custom grind once via Kent, I think it was in the region of 224deg and around 112LSA.
Cant honestly remember though as it was a few years ago.
I think it was in Vizards Yellow Mini book. Choose a cam, then buy one or two steps below milder profile.
very sound advice !
Stick with what is a mild cam, and you'll nearly always have a safe choice. Especially for a boosted engine.
Go for a "big" cam, and there may be potential for some gains up top, but at the risk of massive losses low down.
I have used Real Steel's Typhoon in conjunction with Rhoads lifters very successively with boost. Also Rovercrafts old RC87 worked well.
I also had a custom grind once via Kent, I think it was in the region of 224deg and around 112LSA.
Cant honestly remember though as it was a few years ago.
I think it was in Vizards Yellow Mini book. Choose a cam, then buy one or two steps below milder profile.
very sound advice !
http://www.pumaracing.co.uk/gentune.htm
"When in doubt over a choice between cams always go for the milder of the ones under consideration. I rarely find anyone disappointed after choosing a mild cam but plenty of people have come to regret fitting too hot a cam in the quest for power and losing too much low rpm driveability. Because cams for a given engine are usually the same price regardless of profile, the temptation to be greedy in the choice of duration is always there."
"When in doubt over a choice between cams always go for the milder of the ones under consideration. I rarely find anyone disappointed after choosing a mild cam but plenty of people have come to regret fitting too hot a cam in the quest for power and losing too much low rpm driveability. Because cams for a given engine are usually the same price regardless of profile, the temptation to be greedy in the choice of duration is always there."
I have the car home with an MoT thanks to the guys at TrackvRoad.
I have just come off the phone and have insurance from Adrian Flux (including all mods and the nitrous kit) so i will be taking tha car out for a run to give the rings a better chance of getting bedded in properly. Then i am going to do another compression test of my own before fitting my new wideband sensor and gauge.
Megasquirt is on the way.
So i should have more information and numbers to diagnose later.
I have just come off the phone and have insurance from Adrian Flux (including all mods and the nitrous kit) so i will be taking tha car out for a run to give the rings a better chance of getting bedded in properly. Then i am going to do another compression test of my own before fitting my new wideband sensor and gauge.
Megasquirt is on the way.
So i should have more information and numbers to diagnose later.
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