Chimaera technical. 500 engine (and others) Epic
Discussion
This is an epic!
Teetertank likes his cars.
This has been an epic.
His latest buy is a TVR Chimaera 5ltr V8, took him ages to buy it, a bit choosey is our Teetertank, fussy, you know? 50,000miles with history (it has had a head off a couple of years ago apparently. Had to fix the electric mirrors (much needed with such a poor rear view! Wiper motor park was an easy fix. Service, oil etc.
He knows the advantages of LPG having his last cars on it (Saab 9000 turbo, BMW 328 and would like the TVR on gas. The purist, most other owners of TVRs, and others say why have a Supercar on LPG as it goes against the grain of ownership of this type of car.
I am an LPG systems specialist. I convert to run on LPG
Being fussy he wants to ensure that the thing is up to muster and running perfect, not your ordinary perfect, he is fussy as I said.
So he turns up enthusiastic, keen and optimistic. You see it does not idle perfect. Its okay as t can be excused as being ‘high performance’ with idle rpm specified at 950, a bit high, but it ain't right!
He knows a bit does our Teetertank, code readers are rumoured to be the answer, but not readily available, we are chasing an idle problem because performance is not an issue (this is gonna come back and haunt us as our investigation gets very involved!)
First things are the obvious. Ignition! New plugs, leads, dizzy cap and arm. Still the same. The coil packed up coincidentally, it was weird, so was replaced too. No difference. Fuel!
Checked both lambda probes, engine is perfect according to the readings, beautiful but still poor idle.
Checked every possible reading from every possible source, stepper resistance and movement, tps sensor, temp sensors, airflow sensor, everything! Using pin-out data from several sources we also find that the K-light pin is not connected. Disconnection of the ECU (removing memory feed permanent 12volts resets any codes stored but no difference. I now know this injection system inside out, so any questions?
End of day one, nothing found. To summarise we have VERY low vacuum, idle is poor and Teetertank is very worried. Performance s excellent as he can keep up with a fast motorbike, he has tried it. 0 to 60 times are good too! Maybe it ain’t broke and we don’t need to fix it. As I said, he is a fussy sort.
Compression test: all cylinders around 120psi (within 5%)
Vacuum at idle 12ins hg, very low!
Performance s acceptable.
These figures above give us plenty of head scratching, nothing makes sense, such a low compression on ALL cylinders, and oddly low vacuum at idle!!
Low vacuum indicates:
Leak at inlet manifold/induction system, usually accompanied by a noise. We sprayed WD 40, brake cleaner and anything else handy all over the induction system, nothing.
Ignition timing could be out, we checked this at the ignition stage but swung the dizzy at idle anyway, no improvement in vacuum what ever we did!
Much scratching of heads and phone calls to everyone who may have an answer, I even went to the meet of the TVR club last Sunday (19th October) in Connington! All I discovered was that all 5ltr V8s idle ‘a bit rough’ but the ones I listened to were not as bad as ours.
The Guru of engines, John at Impressions (the fuel injection specialist who I only phone as a last resort) said t has to be a mechanical problem with low vacuum. He’s good, very good as we will discover.
End of day 2
Remove right rocker box , spark plugs and using a DTi and dial gauge on the crank we tried to measure opening/closing of the valves; this is very difficult and accuracy is like shooting n the dark! We did manage to discover that inlet valve opening was at 6degrees before top dead centre (BTDC) which is wrong for sure, the book gives valve timings of:
29°BT-64°AB-75°BB-16°AT
This translates to:
Inlet valve opens 29 degrees BTDC and closes 64 degrees ABDC (After Bottom Dead Centre)
Exhaust valve opens 75 degrees BBDC and closes 16 degrees ATDC
Or so we think.
Several hours of rotating the crank, looking at DTi, checking angles etc. Was not helped by two pints at lunchtime, it all turned to worms as the concentration level required is huge! We also found that the crank can be swung 4 degrees without the camshaft moving i.e. Backlash.
The scene: The car up in the air on my four-post lift, Bugo with a DTi stood on the lift, me underneath rotating the crankshaft with a 24mm socket and breaker bar able to rotate about 12 degrees on the crank at a time
End of day 3
Teetertank gets to the workshop late and informs me that this car s causing him sleepless nights!
We have spent enough man-hours on this t strip and rebuild the engine so from all our information it is decided to remove the inlet manifold. Fortunately my son is a Land Rover apprentice and he only took 50mns to remove inlet manifold, left bank rocker box cover and rocker-shaft assy.
We found lots of the unexpected!
Internally the engine is spotless.
The trumpets are made from 46mm ID steel tubing.
The inlet manifold has been ported and polished to a very high standard.
The cylinder heads have been ported and polished too, a very expensive job done well!
The camshaft is as good as new with not even a scratch on any of the 8 followers which could now be inspected.
Does anyone know if this is how they left the factory
By exposing the camshaft we could accurately measure what it was doing and when. A DTi could be used to measure the exact point of lift, the amount of lift and the overlap.
By trolling the net we had additional information by now, Kent Cams publish just what we needed n their online catalogue, not only the timings, durations, lift etc. But a base method: Inlet valve lift at TDC off the compression stroke, i.e. When the valves are at overlap.
We first checked that our timing mark on the crank pulley was correct by putting a depth gauge onto the top of the piston and marking the depth of the piston about halfway down the bore on both sides of TDC and checking the crank pulley mark for TDC. It was one degree out . So at TDC:
2.16mm lift specified for a competition cam
0.83mm for a mild road cam
Ours? 0.3mm!!!
Such a small lift at this point indicates that the inlet valve has only just started to open!!
Kent Cams also gave angles for inlet valve beginning to open: from 23 degrees on a road cam to 44 degrees on a competition cam (bet that would be rough as rats at idle).
Ours: Inlet valve begins to open 4 (yes four) degrees BTDC!!!!
At this point Teetertank was in two mind, with some questions unanswered. He was pleased to note that this engine s n tip-top condition, even with its faults. He was worried that he had bought (another) dog of a car, possibly clocked, with a worn engine/cam/rings, worked on by amateurs etc.
Does anyone know f the porting work was carried out at the factory or has someone been throwing money at it? My reckoning is that the trumpets are aftermarket and bigger than standard and so someone has spent a fortune on it. Any ideas?
So we know what s wrong now, or at least we have theories that would stand up n court, the cam timing is out....way out. We were just gong to remove and refit the inlet manifold so Bugo could drive home, but after some soul searching he decided to have the timing chest off an have a look at exactly what is going on.
We know that the cam timing s out, by about 20 degrees (sounds a lot!) The £64,000 question is why?
Theory:
The timing chain has stretched. Unlikely.
The engine has been assembled incorrectly. unlikely
These two do not stand up!!
Off with the timing cover, a couple of hours work and can you guess what we found? We were amazed. I will leave you with it until I can get the photographs done. Try for tomorrow!
Teetertank likes his cars.
This has been an epic.
His latest buy is a TVR Chimaera 5ltr V8, took him ages to buy it, a bit choosey is our Teetertank, fussy, you know? 50,000miles with history (it has had a head off a couple of years ago apparently. Had to fix the electric mirrors (much needed with such a poor rear view! Wiper motor park was an easy fix. Service, oil etc.
He knows the advantages of LPG having his last cars on it (Saab 9000 turbo, BMW 328 and would like the TVR on gas. The purist, most other owners of TVRs, and others say why have a Supercar on LPG as it goes against the grain of ownership of this type of car.
I am an LPG systems specialist. I convert to run on LPG
Being fussy he wants to ensure that the thing is up to muster and running perfect, not your ordinary perfect, he is fussy as I said.
So he turns up enthusiastic, keen and optimistic. You see it does not idle perfect. Its okay as t can be excused as being ‘high performance’ with idle rpm specified at 950, a bit high, but it ain't right!
He knows a bit does our Teetertank, code readers are rumoured to be the answer, but not readily available, we are chasing an idle problem because performance is not an issue (this is gonna come back and haunt us as our investigation gets very involved!)
First things are the obvious. Ignition! New plugs, leads, dizzy cap and arm. Still the same. The coil packed up coincidentally, it was weird, so was replaced too. No difference. Fuel!
Checked both lambda probes, engine is perfect according to the readings, beautiful but still poor idle.
Checked every possible reading from every possible source, stepper resistance and movement, tps sensor, temp sensors, airflow sensor, everything! Using pin-out data from several sources we also find that the K-light pin is not connected. Disconnection of the ECU (removing memory feed permanent 12volts resets any codes stored but no difference. I now know this injection system inside out, so any questions?
End of day one, nothing found. To summarise we have VERY low vacuum, idle is poor and Teetertank is very worried. Performance s excellent as he can keep up with a fast motorbike, he has tried it. 0 to 60 times are good too! Maybe it ain’t broke and we don’t need to fix it. As I said, he is a fussy sort.
Compression test: all cylinders around 120psi (within 5%)
Vacuum at idle 12ins hg, very low!
Performance s acceptable.
These figures above give us plenty of head scratching, nothing makes sense, such a low compression on ALL cylinders, and oddly low vacuum at idle!!
Low vacuum indicates:
Leak at inlet manifold/induction system, usually accompanied by a noise. We sprayed WD 40, brake cleaner and anything else handy all over the induction system, nothing.
Ignition timing could be out, we checked this at the ignition stage but swung the dizzy at idle anyway, no improvement in vacuum what ever we did!
Much scratching of heads and phone calls to everyone who may have an answer, I even went to the meet of the TVR club last Sunday (19th October) in Connington! All I discovered was that all 5ltr V8s idle ‘a bit rough’ but the ones I listened to were not as bad as ours.
The Guru of engines, John at Impressions (the fuel injection specialist who I only phone as a last resort) said t has to be a mechanical problem with low vacuum. He’s good, very good as we will discover.
End of day 2
Remove right rocker box , spark plugs and using a DTi and dial gauge on the crank we tried to measure opening/closing of the valves; this is very difficult and accuracy is like shooting n the dark! We did manage to discover that inlet valve opening was at 6degrees before top dead centre (BTDC) which is wrong for sure, the book gives valve timings of:
29°BT-64°AB-75°BB-16°AT
This translates to:
Inlet valve opens 29 degrees BTDC and closes 64 degrees ABDC (After Bottom Dead Centre)
Exhaust valve opens 75 degrees BBDC and closes 16 degrees ATDC
Or so we think.
Several hours of rotating the crank, looking at DTi, checking angles etc. Was not helped by two pints at lunchtime, it all turned to worms as the concentration level required is huge! We also found that the crank can be swung 4 degrees without the camshaft moving i.e. Backlash.
The scene: The car up in the air on my four-post lift, Bugo with a DTi stood on the lift, me underneath rotating the crankshaft with a 24mm socket and breaker bar able to rotate about 12 degrees on the crank at a time
End of day 3
Teetertank gets to the workshop late and informs me that this car s causing him sleepless nights!
We have spent enough man-hours on this t strip and rebuild the engine so from all our information it is decided to remove the inlet manifold. Fortunately my son is a Land Rover apprentice and he only took 50mns to remove inlet manifold, left bank rocker box cover and rocker-shaft assy.
We found lots of the unexpected!
Internally the engine is spotless.
The trumpets are made from 46mm ID steel tubing.
The inlet manifold has been ported and polished to a very high standard.
The cylinder heads have been ported and polished too, a very expensive job done well!
The camshaft is as good as new with not even a scratch on any of the 8 followers which could now be inspected.
Does anyone know if this is how they left the factory
By exposing the camshaft we could accurately measure what it was doing and when. A DTi could be used to measure the exact point of lift, the amount of lift and the overlap.
By trolling the net we had additional information by now, Kent Cams publish just what we needed n their online catalogue, not only the timings, durations, lift etc. But a base method: Inlet valve lift at TDC off the compression stroke, i.e. When the valves are at overlap.
We first checked that our timing mark on the crank pulley was correct by putting a depth gauge onto the top of the piston and marking the depth of the piston about halfway down the bore on both sides of TDC and checking the crank pulley mark for TDC. It was one degree out . So at TDC:
2.16mm lift specified for a competition cam
0.83mm for a mild road cam
Ours? 0.3mm!!!
Such a small lift at this point indicates that the inlet valve has only just started to open!!
Kent Cams also gave angles for inlet valve beginning to open: from 23 degrees on a road cam to 44 degrees on a competition cam (bet that would be rough as rats at idle).
Ours: Inlet valve begins to open 4 (yes four) degrees BTDC!!!!
At this point Teetertank was in two mind, with some questions unanswered. He was pleased to note that this engine s n tip-top condition, even with its faults. He was worried that he had bought (another) dog of a car, possibly clocked, with a worn engine/cam/rings, worked on by amateurs etc.
Does anyone know f the porting work was carried out at the factory or has someone been throwing money at it? My reckoning is that the trumpets are aftermarket and bigger than standard and so someone has spent a fortune on it. Any ideas?
So we know what s wrong now, or at least we have theories that would stand up n court, the cam timing is out....way out. We were just gong to remove and refit the inlet manifold so Bugo could drive home, but after some soul searching he decided to have the timing chest off an have a look at exactly what is going on.
We know that the cam timing s out, by about 20 degrees (sounds a lot!) The £64,000 question is why?
Theory:
The timing chain has stretched. Unlikely.
The engine has been assembled incorrectly. unlikely
These two do not stand up!!
Off with the timing cover, a couple of hours work and can you guess what we found? We were amazed. I will leave you with it until I can get the photographs done. Try for tomorrow!
do you know what the camspecs are for this cam?If the inlet is opening late then it stands to reason it's closing late too, which would reduce the dynamic compression ratio and perhaps explain the low CR test results and lack of torque at idle (requiring more throttle hence less manifold depression).
Is it something silly like an adjustable can drive gear not locked down?
The standard induction looks like bit of old exhaust pipe but are in fact carefully tapered tubes. I've been told that replacing them with 'proper' trumpets gives negligible improvement.
Is it something silly like an adjustable can drive gear not locked down?
The standard induction looks like bit of old exhaust pipe but are in fact carefully tapered tubes. I've been told that replacing them with 'proper' trumpets gives negligible improvement.
GAVC said:
The vernier locking screws on the cam wheel are loose?
Spot on Timing sprocket had slipped to end of vernier travel adjustment. This travel on the sprocket is approx 15°, hope this is enough to account for the large timing error that is present on the cam, and once reset will solve the problems the engine is having.
Planning on replacing with a non-vernier sprocket, to ensure this can't happen again - any recommendations for good quality replacements?
Teetertank said:
Planning on replacing with a non-vernier sprocket, to ensure this can't happen again - any recommendations for good quality replacements?
Just put a new set on mine. Rob from V8Developments recommended the non adjustable duplex set. This has a set of keyways which enable it to be set to 1 degree IIRC.Edited because Spendy said so!
Edited by Chimjunkie on Monday 27th October 20:57
Chimjunkie said:
Teetertank said:
GAVC said:
Planning on replacing with a non-vernier sprocket, to ensure this can't happen again - any recommendations for good quality replacements?
Just put a new set on mine. Rob from V8Developments recommended the non adjustable duplex set. This has a set of keyways which enable it to be set to 1 degree IIRC.
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