Chim 500 running lean 260 bhp
Discussion
Hi guys, Chimaera 500 1999 27,000 miles, just been serviced.
just had a rolling road session, and i think the results are disappointing. according to the tester ( my son in law) the car runs lean exactly when the power drops off, which if i have read the graph right seems to be at 4500 revs.
my question is this, is this a realistic bhp , 260 at the flywheel, or is there a fault i can rectify that gives me more horse power.
He suspects the air flow meter, if this is the case do i just swap it and hope i stop it running lean? i have no idea how to test it myself. should i get a bigger bore afm which theoretically will make it run richer when i need it? i personally think its the fuel pump not getting enough fuel through at higher revs. any input whatsoever i would be grateful to have. if i do nothing because the concensus of opinion thats just about the right bhp, he warned me that if i use high revs often enough while it is running lean then i could damage the engine.
thanks in advance
Lester
just had a rolling road session, and i think the results are disappointing. according to the tester ( my son in law) the car runs lean exactly when the power drops off, which if i have read the graph right seems to be at 4500 revs.
my question is this, is this a realistic bhp , 260 at the flywheel, or is there a fault i can rectify that gives me more horse power.
He suspects the air flow meter, if this is the case do i just swap it and hope i stop it running lean? i have no idea how to test it myself. should i get a bigger bore afm which theoretically will make it run richer when i need it? i personally think its the fuel pump not getting enough fuel through at higher revs. any input whatsoever i would be grateful to have. if i do nothing because the concensus of opinion thats just about the right bhp, he warned me that if i use high revs often enough while it is running lean then i could damage the engine.
thanks in advance
Lester
my 97 450 made 269 at the fly last year. Only mod is the ACT induction pipe and pre-cats removed. IIRC I gained 9Bhp with the ACT kit (comparing before and after runs).
The more accurate measurement would be the at the wheels figure as thats a 'real' number as opposed to the calculated fly number. So do you have the at the wheels figure?
Shouldnt run out of puff until ~5400-5600 so somethings not right. Hopefully someone more knowledgeable will be along shortly to give some proper advice.
The more accurate measurement would be the at the wheels figure as thats a 'real' number as opposed to the calculated fly number. So do you have the at the wheels figure?
Shouldnt run out of puff until ~5400-5600 so somethings not right. Hopefully someone more knowledgeable will be along shortly to give some proper advice.
spend said:
If the test is 'in the family' get him to stick a fuel pressure gauge on for a power run so that you can see whats happening before you start making assumptions.
sorry for being a dipstick, but is a fuel pressure meter something he would have to hand, or be expected to?i am not so worried at the moment about the apparent lack of power as it still seems fast, i mean quick to me. i am more worried about damage if its running lean as i often go up to the higher revs
i intend to keep my car so will be looking for more power once i know my car is healthy
bigdods said:
my 97 450 made 269 at the fly last year. Only mod is the ACT induction pipe and pre-cats removed. IIRC I gained 9Bhp with the ACT kit (comparing before and after runs).
The more accurate measurement would be the at the wheels figure as thats a 'real' number as opposed to the calculated fly number. So do you have the at the wheels figure?
Shouldnt run out of puff until ~5400-5600 so somethings not right. Hopefully someone more knowledgeable will be along shortly to give some proper advice.
i have a graph that shows flywheel bhp on one side, revs at the bottom and on the other side it shows high speed air flow ratio? so i think the answer is no :-(The more accurate measurement would be the at the wheels figure as thats a 'real' number as opposed to the calculated fly number. So do you have the at the wheels figure?
Shouldnt run out of puff until ~5400-5600 so somethings not right. Hopefully someone more knowledgeable will be along shortly to give some proper advice.
lestershaw said:
spend said:
If the test is 'in the family' get him to stick a fuel pressure gauge on for a power run so that you can see whats happening before you start making assumptions.
sorry for being a dipstick, but is a fuel pressure meter something he would have to hand, or be expected to?i am not so worried at the moment about the apparent lack of power as it still seems fast, i mean quick to me. i am more worried about damage if its running lean as i often go up to the higher revs
i intend to keep my car so will be looking for more power once i know my car is healthy
blitzracing said:
A Spend says, you need a fuel pressure check on the fuel rail whilst on the Rolling road at full power. It should be 37-38 psi, and not drop as long as the throttle is wide open up to peak RPM. If it drops even a couple of PSI, it will make the engine lean out, and shows that you have a fuel delivery problem of some sort, such as a knackered pump,(or low pump supply voltage- worth checking), blocked fuel filter or restrictive fuel line. The fuel pressure will drop when you close the throttle, this is quite normal. As for engine damage, its not done that easily unless you run for a period under load like this where things can get hot enough to do some damage. Less fuel means less cooling around the combustion chamber, so pre ignition becomes more of a damaging issue.
Hi blitz, for the sake of £60 is it worth just changing the fuel pump anyway, or would i still have to confirm that it was working as it should? pre ignition is pinking? the rolling road guy said it would pink occasionally, and if he used his listening equipment he would probably hear it.i dont think my driving, spirited as it is, would place the engine under load for that long anyway, which puts my mind at rest a bit
Lester
Chilliman said:
Lester, I've just posted my RR print outs in a new topic thread, may be interesting as a comparison ????? R.
Hi RichardThe read out i took with me was the afr and flywheel results i think. my flywheel graph looks very similar to yours iirc, but i cant remember what the fuel graph looks like, i will post it tonight and see what any one else can make of it.
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