RB20 ideal A/F tuning

[ToroGTS]

Ideally what is the perfect A/F to be at at idle and under boost, lower throttle and WOT? if I had to take a shot in the dark I'd say 12.5ish all around maybe a little leaner at idle?

[h4X6]

sounds about right for idle, boot, you want to be just a tad rich just a little bit over stoich. i could be wrong here but i dont think i am lol

[ToroGTS]

Answer: After scouring the internet here is the answer.... idle at 13-13.5 then dropping to 12 as boost rises, 12-11.8 thereafter.

[nimblestix]

14.7 is perfect stoich for idle from what I understood. 13-14 for cruise and 10.9-12ish for boost?

[ToroGTS]

Better to run slightly rich at all times to keep cylinder/exh gas temps down. The unburt fuel absorbs energy when it changes from liquid to vapour and carries heat out the cylinder when it leaves.

[Skym]

14.7 is perfect stoich for idle from what I understood. 13-14 for cruise and 10.9-12ish for boost?

That's if running stock cams. Into 10's is best for reliability when on boost.

With A/F ratio, have to take into account cheaper widebands can be out by 0.6:1 and more expensive dyno widebands can be out by 0.1:1 (experienced, trained ECU tuner on GTRC mentioned this problem).

Also have to take into account voltage drops to fuel pump when aircon, headlight's, etc are on (even if hardwire fuel pump) at night time or on hot day, etc. You don't want to be above 12.0:1 with factory engine, so 11.2-11.4:1 (taking into account wideband inaccuracy and voltage fluctuation at fuel pump, which I think can be as much as 2 volts, as factory voltage drops from 12v to 10v at higher rpm), advance ignition timing to get the hp when on boost. But for 100% reliability on racetrack, 10's (just like factory tune).

If look at the voltage vs flow graphs here, you can see that drop in voltage causes a lack of fuel problem -

http://www.deatschwerks.com/resources/fuel-pump-tech/dw300-fuel-pump-tech

Just 2 volts more results in a rough 55lph difference.

In total, I think it's around 3 volts max (roughly what I worked it out to via testing with aircon, headlight's, etc on) can be lost to fuel pump (with aircon, head light's, etc on).

[Nismo_line]

dont want to be above 12 when on boost? so is what nimblestix said pretty bang on?

[Skym]

To be safe, under 12.0 (max). Each tuner is different at what they think is best as far as A/F ratio goes under 12.0:1, due to experience of what produces the most hp, better fuel economy without engine letting go, but 11.2-11.4:1 is safe, ideal would be high 10's if possible for 100% reliability.

The main problem is the voltage drop to fuelpump, loss of fuel that have to compensate for. That's why this product was invented to provide a stable voltage to fuelpump (voltage could drop to 10 volts going into device, but still output a higher voltage), but it comes with it's own set of tuning, reliability problems (could fail and wouldn't know it has failed, as has no warning light on it, hence why many use the hardwire method, as it's simple and reliable) -

http://www.kennebell.net/KBWebsite/Accessories_pg/Boost%20A%20Pump/layouts/boostapump.htm

You can make something similar if know how to (many tutorials showing how to on Youtube).

In Japan they tend to run engine rich and use ignition timing to make the hp. There's a limit you can go with ignition timing due to fuel engine is running on (before unstable combustion / knock happens), intake temps (intercooler size, type), A/F ratio.

With stock cams it should be correct. If fit aftermarket cams (depending on specs of cams that determines how much air enters cylinders) you run engine richer, raise idle rpm due to get lower vacuum with more aggressive cams (also have to change BOV spring to suit lower vacuum if run say a Tial BOV).

The A/F ratio at idle, idle rpm vs Tomei cam specs (up to 270 duration) is mentioned here -

http://www.tomei-p.co.jp/_2003web-catalogue/e140-157_reytec_page/e154-157_te-info.html

I think with NA RB engine it was around 13.5:1 at peak hp (where turbocharged engine would be when on boost). But with turbocharged engine you have to take into account the extra air turbo provides (known as boost or basically above 0 on stock, aftermarket boost gauges) on top of what engine sucks in via pistons going up and down (vacuum or under 0 on boost gauge), so is around 12.0:1 max.

[Nismo_line]

To be safe, under 12.0 (max). Each tuner is different at what they think is best as far as A/F ratio goes under 12.0:1, due to experience of what produces the most hp, better fuel economy without engine letting go, but 11.2-11.4:1 is safe, ideal would be high 10's if possible for 100% reliability.

The main problem is the voltage drop to fuelpump, loss of fuel that have to compensate for. That's why this product was invented to provide a stable voltage to fuelpump (voltage could drop to 10 volts going into device, but still output a higher voltage), but it comes with it's own set of tuning, reliability problems (could fail and wouldn't know it has failed, as has no warning light on it, hence why many use the hardwire method, as it's simple and reliable) -

http://www.kennebell.net/KBWebsite/Accessories_pg/Boost%20A%20Pump/layouts/boostapump.htm

You can make something similar if know how to (many tutorials showing how to on Youtube).

In Japan they tend to run engine rich and use ignition timing to make the hp. There's a limit you can go with ignition timing due to fuel engine is running on (before unstable combustion / knock happens), intake temps (intercooler size, type), A/F ratio.

With stock cams it should be correct. If fit aftermarket cams (depending on specs of cams that determines how much air enters cylinders) you run engine richer, raise idle rpm due to get lower vacuum with more aggressive cams (also have to change BOV spring to suit lower vacuum if run say a Tial BOV).

The A/F ratio at idle, idle rpm vs Tomei cam specs (up to 270 duration) is mentioned here -

http://www.tomei-p.co.jp/_2003web-catalogue/e140-157_reytec_page/e154-157_te-info.html

I think with NA RB engine it was around 13.5:1 at peak hp (where turbocharged engine would be when on boost). But with turbocharged engine you have to take into account the extra air turbo provides (known as boost or basically above 0 on stock, aftermarket boost gauges) on top of what engine sucks in via pistons going up and down (vacuum or under 0 on boost gauge), so is around 12.0:1 max.

ok thanks for the info. for mainly stock engine, would 14.5 ish for idle and 13-14 for cruising good?

[Skym]

You're welcome. Rough idea of how it's set (best to consult a trained ECU tuner), stoich at idle (best fuel economy) is around 14.7:1, some say 14.6:1. Into 13's when cruising, light loads and gets richer as boost level increases above 0 on boost gauge until at peak boost where it's at 11.2-11.4:1 and stays like that until redline (if boost plot is flat). Ignition timing is matched to that.

[Nismo_line]

k great thanks. this is just for now till next year when nistune and other engine mods go in.