Getting frustrated now (idle speed)
Discussion
Got the laptop working and linked to the ECU, read the posts several times and went for the set up. discoverd pot1 was a bit spikey so replaced it. Got the pots set to 14.8 stinking hotwhich brought the adaptive figures in line and looking good. Throttles appear closed but running fine. Went for a test and its running great, smooth pick up and pops and bangs nicely but i just cannot get the idle speed below about 1050 to 1100..... If I block both air intakes completely - it makes no difference.still keeps running at 1100... What am I missing? I assume it can only be an air leak downstream of the butterflys or worn throttle bodies. So how do I diagnose each of these? The bodies look good and I can't detect any sideways movement when closed, so whats the test for worn bodies?
What is the likelyhood of a downstream air leak
Cheers
GG
What is the likelyhood of a downstream air leak
Cheers
GG
jammy_basturd said:
On the passenger airbox, right at the back (near the Y-piece that goes to the water manifolds) there should be a MAP take off hose that goes to the ECU, double check that it is still connected.
Excellent advice. It was unhooked. Now running a little slower. What does the pipe do and should I re-run the set up now the pipe is connected? jammy_basturd said:
On the passenger airbox, right at the back (near the Y-piece that goes to the water manifolds) there should be a MAP take off hose that goes to the ECU, double check that it is still connected.
I was sure Julian at Raceproved said that this MAP sensor which is inside the ECU is not used in the TVR software? A MAP sensor (manifold pressure) isn't used with the Cerbera it uses the throttle pot inputs.
The pipe off the NS airbox goes to the barometric pressure sensor which is a little black box that sits above the trim above the passenger's knees. The input from the baro pressure sensor is used by the ECU.
The pipe off the NS airbox goes to the barometric pressure sensor which is a little black box that sits above the trim above the passenger's knees. The input from the baro pressure sensor is used by the ECU.
I had this once, even with the idle screw wound right out still couldn't get it ticking over at low enough revs.
Had just had the throttle bodies put back onto a rebuilt engine, it had been done badly and the o rings weren't
seated correctly you could see two of them sticking out when looking down the inlet,
Austec have a much better answer to the o rings, a gasket that is connected on all inlets so much more difficult
to get trapped and misaligned, maybe worth biting the bullet get these and get it set up once and for all.
I know it's good to crack a problem but sometimes just get it sorted and enjoy the car.
Good luck.
Had just had the throttle bodies put back onto a rebuilt engine, it had been done badly and the o rings weren't
seated correctly you could see two of them sticking out when looking down the inlet,
Austec have a much better answer to the o rings, a gasket that is connected on all inlets so much more difficult
to get trapped and misaligned, maybe worth biting the bullet get these and get it set up once and for all.
I know it's good to crack a problem but sometimes just get it sorted and enjoy the car.
Good luck.
Tanguero said:
An air leak will only affect the idle if it is on the engine side of the throttles. A leak into the airbox will not (they already have quite a large leak in through the air filter).
I realised this would be the case after I sat and thought about it for a few minutes. But it did seem to make a detectable difference so I guess the barometric sensor has some input on the MAP. I will reset it all tonight. Austec also suggested they could change the idle timing through the map (currently at 18 deg Advance) which is probably the next thing to try.GG
I would strongly caution against adjusting the timing to fix this unless you are utterly certain that it really is the only cause of the problem. If it is something else that you later find and correct then your mapping will be wrong and you will have the problem that it wont idle at all! At best it is a horrible bodge rather than fixing the problem 
Have you used an airflow meter to compare flow on each throttle on both banks? This might show a butterfly not closing properly etc. I picked up a synchrometer on fleabay for about 25 quid and it makes setting up throttle pots & adaptives so much easier and more accurate.
The Cerbera definitely does not have a MAP sensor! There is a barometric pressure sensor that attaches to the passenger air box that monitors atmospheric pressure. Your air boxes should be close to atmospheric unless you have a seriously clogged air filter!! I suppose it could make a small difference being disconnected, but it is only a fine trimming input to the ECU unlike a MAP metering system.
Is this a 4.2 or a 4.5?
Have you used an airflow meter to compare flow on each throttle on both banks? This might show a butterfly not closing properly etc. I picked up a synchrometer on fleabay for about 25 quid and it makes setting up throttle pots & adaptives so much easier and more accurate.
The Cerbera definitely does not have a MAP sensor! There is a barometric pressure sensor that attaches to the passenger air box that monitors atmospheric pressure. Your air boxes should be close to atmospheric unless you have a seriously clogged air filter!! I suppose it could make a small difference being disconnected, but it is only a fine trimming input to the ECU unlike a MAP metering system.
Is this a 4.2 or a 4.5?
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