Stioetchmetric Ratio

[NimAjNeB]

Hello Guys,

Sorry to bore you people but I was wondering if anyone could give me a little information.

I have just had a new Xforce 3 1/2" exhaust fitted with a stainless pod filter and a bleed value to increase the boost to 10PSI.

I had it tested on a dyno and the air/fuel ratio was at about just under 13 at idle and dropped off towards the end of the scale after the car produced it's maximum power to about 11.

My question is, is this too lean or at a dangerous level to be running the car at? I have had people tell me it's fine then other people tell me they have herd of valve seals burning out at 12.5 and mine is at 13!!!!!!!

Anyway just wondering and any info would be much appreciated.

Cheers

[PlasticStan]

I wouldn't worry about what the afr is at idle. Under load and boost is a different matter and yours is 11:1, most people tune for about 12:1 so yours is running slightly rich. Do you have a programmable ecu as leaning it out a little will gain you more power.

[NimAjNeB]

Hey

No I don't think I have a programmable ECU how would I be able to tell? Do R33 RB25DET's come with a programmable ECU or not?

It's completely standard besides the mod's mentioned!

Thanks for the advice by the way.

[predator]

the rb25det ECU tries to overcompensate when you are running more boost... especially at the higher levels. That is why you are seeing a rich (11:1) ratio at the upper end of the revs. At idle, 13:1 is perfectly fine, as the engine is not under load, and this is good for things like fuel economy.

11:1 is actually fairly rich.. its AIR to FUEL ratio.. so 11 parts air to 1 part fuel.. so more air = leaner mixtures.

You need some form of adjustment, that the ecu simply cannot do - so you will need an aftermarket ecu OR a "piggy back" system to your existing ecu, such as a the popular (and cheap) SAFC... there are plenty of threads in forced induction.. so do a search and read up so u don't get thrown the "do a search" line

[Col-GTSX]

R33 in mostr forms should run an AFR of 14.1:1 at idle and 12:1 under full load.... Anything around these figures is fine and perfectlly normal....