Fueling _ Lowest safe fuel pressure?

Prophet

Prophet

Prophet

Soldato
Joined
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I've got an issue with my fueling. On Wide Open Throttle the car overfuels when on boost. The Wideband is reading 10.2 which is way too low. It should, for my setup be reading around 11.5. Currently my fuel pressure is 1.7Bar at idle with the vacuum hose connected to the pressure regulator, and rises as it should as engine speed increases etc.

At idle the wideband reads around 14.5/15 which is fine.

I'd like to decrease the fuel pressure to stop the overfueling however I'm worried about running it too low on idle. Mainly to avoid compromising the spray patten of the injectors and leaning out.

Looking for any info that may help :)
 
What car is this? how are you controlling fuel pressure.

10:1 sounds normal on a lot of engines under full throttle - it stops the spark plugs melting holes through pistons
 
Getting the ECU map tweaked would be a better option than messing about with the fuel pressure. Besides, as Simon said, ~10:1 isn't out of the ordinary for boosted engines under W.O.T. Sure it's a little rich but it's helping to keep your pistons nice and safe.

Just turn up the boost a bit ;)
 
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Its a Calibra Turbo engine.

From what I've read/been told 12 is acceptable however 11.5 offers the safety element. Some of the guys I know seem to have it around hight 10's to low 11's.

Fuel pressure is controlled via a Webber Regulator. The same type used on Cossies.

Mapping the ECU isnt really an option at the moment.
 
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I would just leave the fuel pressure where it is, that richness gives you a cushion to turn up the boost a little, unless you are already on/near the safe amount boost for your turbo and engine.
 
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Boost is currently set to 15PSI. The ECU allows upto 22PSI on overboost and holds 16PSI. I'm going to tweak it up a little and recheck the figures.

I'd like to get it a little higher if possible as I'm getting the odd pop/bang/flame from the exhaust. I've been told it looks cool but as I can't see it I'd prefer to back off the pressure a little.
 
Altering fuel pressure to get a change in mixture is a total total bodge. Lowering the fuel pressure to get the kind of drop in on boost AFR will leave you too lean at idle(if it would idle at all) and too lean on cruise.

I would recomend leaving the fuelling well alone and saving for an aftermarket ECU, even if its just a Greddy eManage piggy back which you could use to alter the on boost fuelling to a more acceptable level.
 
Marf said:
Altering fuel pressure to get a change in mixture is a total total bodge. Lowering the fuel pressure to get the kind of drop in on boost AFR will leave you too lean at idle(if it would idle at all) and too lean on cruise.

I would recomend leaving the fuelling well alone and saving for an aftermarket ECU, even if its just a Greddy eManage piggy back which you could use to alter the on boost fuelling to a more acceptable level.
Click to expand...

Aftermarket ECU and mapping is planned but not for a while hence my initial question. I understand its not ideal.
 
I would just leave it well alone until you can get an ECU on there of some sort, the fuel wont atomise properly either if you lower the fuel pressure, plus you may end up too lean as it starts to come on boost which could result in higher EGTs and detonation, which will either melt you a piston or blow your headgasket.

Sure 10.2:1 is rich but it wont be doing any harm. My MR2 Turbo runs high 9's in the top end on full boost. Should unlock about 15-20 hp reigning that in to 11:1 or so. :)
 
That was my worry. I'll leave it for now :)

Mine should be producing around 260BHP at the moment however with the increase in boost and correct fueling it should be good for 300BHP hopefully.

I'd like an EGT gauge. Do you have one installed?
 
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