anybody know what is a guide line for figures of Air/fuel mixture for optimum performance and likewise lean-ness max
cheers
Out of interest, & once you know the answer to the question you ask, how would you adjust your car’s settings if it were desirable?
craig
google around and you will find lots…
Answers - The Most Trusted Place for Answering Life's Questions is an example
Out of interest, & once you know the answer to the question you ask, how would you adjust your car’s settings if it were desirable?
i would probly play with the up or down switch…
had car dynoed and although favourable over standard output figures (mine with with decat, ultra and standard induction) it was still slightly lean.
When attached the ITG kit it became even leaner and slight drop in power.
Apparantly ECU should cope with extra demand for fuel but now the story goes the problem lies with the fuel pump which isnt man enough for the job. ??? If however this was resolved the ITG kit would come into its own…ermmmmmm… unless someone can cast more of a technical light on it.
i would probly play with the up or down switch…
Thought you might say that However, since when has the Exige S2 ECU been programmable (other than by Lotus)?
good point .
my only thing being is it worth persuing the fuel pump thing or leave well alone with the standard airbox set up, decat and ultra. (providing this set up wont eventually melt down on me)
Now curious - how do you know it was “slightly lean”, then?
craig what are your A/F readings?..I’m installing a a/f meter in my Tri-Point supercharged car now and whould like to compair numbers…
Craig, if its running that lean its losing power then put back some of the original parts until you can the fuelling changed, otherwise you’ll start melting the exhaust valves/cracking heads/cracking manifolds… all not good
The optimum AFR for an engine running on petrol is about 13.8:1. Normally you’ll run this AFR upto about 6000rpm at which point you will have to enriched further in order to maintain a maximum exhaust port temperature of around 950�C so it may drop to say 12.5:1 but this is very engine specific. I have seen some running below 10:1.
Your Lambda sensors in the exhaust are most likely to be only switching types - i.e. they can only say whether its running rich or lean with any certainty so at high load they are useless. The ECU switches to an open loop fuelling strategy and decides how much fuel to pump in by measuring the mass air flow at the throttle and calculating how much fuel is needed to get the target AFR. It appears that the calibration isn’t coping running with reduced back pressure and inlet depression.
Other than finding a chip tuner or EFi dealer whose prepared to break into the ECU and remap it the easiest thing to do is fith a rising rate fuel pressure regulator. This will increase the fuel pressure at high manifold pressure by a larger amount than the standard one does.
Other tricks involve modifying the coolant temp sensor so it thinks the engine is running cooler and richens it up.
To be honest though, remapping is the only sensible thing to do, the others will no doubt throw the MIL light on as the ECU starts to realise the fueling is being pushed richer than it wants.
On other possiblilty is to fit a piggy back ECU such as a Dasteq(?) or PowerFC. This intercepts the ECUs normal outputs and adjusts them. Its still not pretty but it may be the best hope for now.
I dont believe the fuel pump is the issue for a minute, you wont have increased the power that much and I bet the 240Rs pump is the same part.
I hope you sort it.
Bob
Now curious - how do you know it was “slightly lean”, then?
this was the words of the dyno man.
frank:
the AF figures from my dyno sheet read (approx)12:1 at 2000rpm to 14:1 max at cam crossover with average of around 13:1 to 8000rpm this is with standard airbox
Might be worth talking to Red Motorsports in Germany
They have a couple of SC kits including the Swiss kit that uses the standard ECU unit. They have also got 265 from the 240R
Yo guys if you want info on the ECU check out charlies post on www.moremonkey.com register and look in the tech section…much can be learned from monkeys
Craig, if its running that lean its losing power then put back some of the original parts until you can the fuelling changed, otherwise you’ll start melting the exhaust valves/cracking heads/cracking manifolds… all not good
The optimum AFR for an engine running on petrol is about 13.8:1. Normally you’ll run this AFR upto about 6000rpm at which point you will have to enriched further in order to maintain a maximum exhaust port temperature of around 950�C so it may drop to say 12.5:1 but this is very engine specific. I have seen some running below 10:1.
Your Lambda sensors in the exhaust are most likely to be only switching types - i.e. they can only say whether its running rich or lean with any certainty so at high load they are useless. The ECU switches to an open loop fuelling strategy and decides how much fuel to pump in by measuring the mass air flow at the throttle and calculating how much fuel is needed to get the target AFR. It appears that the calibration isn’t coping running with reduced back pressure and inlet depression.
Other than finding a chip tuner or EFi dealer whose prepared to break into the ECU and remap it the easiest thing to do is fith a rising rate fuel pressure regulator. This will increase the fuel pressure at high manifold pressure by a larger amount than the standard one does.
Other tricks involve modifying the coolant temp sensor so it thinks the engine is running cooler and richens it up.
To be honest though, remapping is the only sensible thing to do, the others will no doubt throw the MIL light on as the ECU starts to realise the fueling is being pushed richer than it wants.
On other possiblilty is to fit a piggy back ECU such as a Dasteq(?) or PowerFC. This intercepts the ECUs normal outputs and adjusts them. Its still not pretty but it may be the best hope for now.
I dont believe the fuel pump is the issue for a minute, you wont have increased the power that much and I bet the 240Rs pump is the same part.
I hope you sort it.
Bob
cheers bob,
looking at mine then based on 13:8.1 it doesnt seem that bad???
Those number are very high…my car is runing 10.5 - 11. at 8500rpm…never higher then 13 at cruse…Itg and catless should do nothing to your A/F …It didn’t change mine…could be your tuners meter is off. They do need recalibration from time to time…Installing one in the car and taking it out into the real world is the only way to know for sure…I’ll post my nunbers later for comparison…
Yeah, its not dire. I’d like to see slightly less than 13:1 at the top end though. It would be useful to measure the exhaust gas temp.
Considering you were talking about knocking the other day I’d consider getting one of these -
What happens to the AFR with the new airbox?
The change in AFR with the airbox may not be caused by a change in the airflow rate but more likely that the mass air flow meter doesn’t work properly any more. The air flow through the sensor is very sensitive to the duct geometry leading up to it and your new box will have changed that quite significantly.
BC
Oh yeah Craig, there’s an all comers sports car meet at the Fox and Hounds in Whittlebury starting now. I’m going to pop over for an hour in a few mins and then come back at half time for the footy (devided loyalities?
hi bob,
sorry i couldnt make that…watching the footy.
the AFR with the ITG is about parallel all the way through against the standard airbox AFR (although about 1 part more on average)
The standard airbox also drops more just after 6000rpm to around 12:1 where the ITG is still running the same at around 13.5:1
The question is… is this safe or am i in danger??
(ITG Blue line standard airbox red line)
[image]http://img474.imageshack.us/img474/5963/dscf00021vr.th.jpg[/image]
![[image]http://img474.imageshack.us/img474/5963/dscf00021vr.th.jpg[/image]](http://img474.imageshack.us/my.php?image=dscf00021vr.jpg){kind=link}
Craig, no worries, it was wet and horrible, you did the right thing.
You certainly dont want to be running leaner than the stock engine would. Its a pity we haven’t got a baseline to compare to. I would make it a priority to get it sorted and leave the std airbox in place for now.
Franks certainly mapped his very safely but there’s no need to run AFR of 13 at cruise (unless he cruises at 100+mph). Also he doesn’t have to pay our petrol prices…
I’ll have a think. Its a long shot but I’m wondering if there’s anything that EFi themselves could recommend (Ole Buhl http://www.obr-motorsport.co.uk/ )
Fingers crossed
Thought you might say that However, since when has the Exige S2 ECU been programmable (other than by Lotus)?
since about febuary 2005
since about febuary 2005
Thanks, I thought something in the back of my mind told me it was being done in the USA. Is it a replacement ECU? If not, what mods are done to the original to enable it to be mapped? Either way, I presume it voids the warranty?
TIA