Air Fuel Ratio Of GT-Rs

[NismoS-tune]

A lot of you guys are running waaay too rich under WOT. Personally i'd like to stay above the 11:1 mark. Excessively rich can be almost as bad as too lean.

Find me a different tuner then lol

[bignate]

A lot of you guys are running waaay too rich under WOT. Personally i'd like to stay above the 11:1 mark. Excessively rich can be almost as bad as too lean.

[kengeroo]

this is what I am shooting for,,, basic stock rb26 ,, other than the basic upgrades,,, meth, divided pipe, new intercooler

does this seem like a good start ??

[NismoS-tune]

I idle around 13 and WOT around 9.8

[GodziRRa]

Well my idle is playing somewhere around 14.7 to 15.2. Can't see the WOT numbers yet coz the engine is newly rebuilt.

[bobbo]

I have my idle set to about 15.5:1, cruise at 15:1 and WOT max boost (1.05bar) is 10.8-11.2:1.

[GodziRRa]

I see. Hmmm gonna check out my a/f play tom. I run a Mine's ECU, and if I remember it right my idle is 15 to 15.3? I'll double check it.

[Skym]

It's set for max of around 14.7:1 on stock fuel map with stock car at idle. With o2 sensor + ECU it might make it reach 15.0:1 at idle before o2 sensor voltage hits o2 sensor lean voltage trigger on ECU and ECU makes engine run richer, then hits rich voltage trigger and ECU runs engine leaner, then repeats. The lean o2 sensor voltage trigger might be set at 15.0:1 (I think is set at 230mv), but haven't converted the lean o2 sensor voltage trigger to A/F ratio to check.

With intake, exhaust it might make that 14.7:1 leaner and hit the lean o2 sensor voltage trigger. When combined with idle stabilisation (adjust's ignition timing), might get a miss, stumble at idle. When you unplug or disable o2 sensor (force ECU into open loop), the missing at idle stops, as o2 sensor is not making engine run leaner, richer and ECU is using what's set on fuel map only (not good idea if engine is running lean due to intake or exhaust leak, weak fuelpump or weak voltage to fuelpump due to old wiring, clogged fuel filter, etc).

[GodziRRa]

Ok. So the Nissan set a/f ratio will not go above 15... Is this precise? I remember some say that Nissan set it at around 15+. And with the intake and exhaust add on, what would be the effect? Make the ratio leaner?

[Skym]

The A/F ratio is leaner with intake, exhaust due to rise in boost level.

R32 GTR ECU is not so hot on fueling side.

Nismo swap it for a retuned R33 GTR ECU + R33 GTR o2 sensors to match which is better with fueling -

http://www.nismo.co.jp/omori_factory/original_menu/engine_m/sr/index.html#bnr32

[frankiman]

stock gtr with stock everything it might be,
but as soon as you change something in the system without tuning the ECU for it, the AFR can change
like if you install an aftermarket intake kit, or exhaust system, it will all affect afr

and after that it depends on the tune

i had issues earlier this summer with injectors, and a good tune was hard to settle,
sometimes i could idle at 17 to FL and other times at 12
and on some occasions, i got as low as 10,4 at WOT

[Skym]

The A/F ratio varies depending on what cell ECU is looking at on fuel map. The above dyno graph is the WOT run where it runs across multiple cells when going from left to right of fuel map on stock ECU.

Stock GTR = 14.7:1 is as lean as it can go at idle and 10.7:1 is richest at WOT. But idle, cruise A/F ratio is affected by o2 sensor, so might be leaner or richer at idle, cruise.

[needavdub]

I'm about 14.6:1 at idle and similar cruising, and about 11.8-11.9:1 under full boost at WOT. Using a Innovate LC-1 wideband and running a Blitz Access tuned ECU with stock turbos @ 15 PSI.

[GodziRRa]

Nice graph bro. Anyways, anyone knows what is the Nissan set A/F ratio on idle, cruise, and WOT for the GT-Rs?

[frankiman]