Safe Afr

[BlackRBS13]

Alright I was just wondering what is the leanest afr you guys would consider safe. Basically I have a stock rb26 with no boost restrictor, exhaust and a FMIC, so the boost is around 15psi. had the car on a dyno and the afr ratio was mostly in the high 11s and low 12s but spiked at about 12.9. Is this getting pretty dangerously lean? Thanks for any help. Also what AFR would you recommend tuning to when I get PFC?

[NYTSKY]

11.8 is safe.Some people do 12-12.2

All tuners are different.

[BlackRBS13]

How dangerous is it to have that spike at 12.9? Is it at serious risk of melting a piston or something else? Just wondering if I should be really hesitant to go WOT.

[GreeceS13]

As NYTSKY said you 11.8 is safe! Don't risk it with 12.9!! I know many tuners that tune with afrs like yours but it is risky and to have many horsepower!

Better safe than sorry!

If you have with 15psi 12.9, try 12psi or less!!

Better safe than sorry!

Buy a PFC or remap your stock ecu. It is cheaper than to rebuild your engine!!

Better safe than sorry!

Edited May 1, 2008 by GreeceS13

[R31Nismoid]

If its a 10+yr old RB26 i'd stick to 13-14psi, likely the turbos will leg go for a start

Second, ensure not only getting a tune/ecu you also have a look at fuel pump, pressure, injectors (might be one slightly blocked etc)

[BlackRBS13]

I would run less boost but I am already running at just the wastegate spring pressure. No real way I can see to limit it below that.

[Adriano]

Does it currently have a stock ecu, if so i would be checking the fuel pump, as there is no real other reason it would be running lean up top.

[BlackRBS13]

So the stock injectors should be good enough to keep up with the 15psi? Also is anyone sure what the boost is without the boost restrictor on a GTR? My car is swapped so I am not positive that the turbos are stock, since i got the motor with 30k on it. though I am pretty sure cause they appear to be stock. Also yes it is a stock computer. Fuel pump is a walbro 255lph so I would think it would be fine. I am gonna get it back on the dyno in a couple weeks and take another look at the afr.

[Guilt-Toy]

A print out of the dyno sheet... power vs AFR & power vs boost would be able to tell me if its dangerous or not. The first one would help if thats all you have.

Alright I was just wondering what is the leanest afr you guys would consider safe. Basically I have a stock rb26 with no boost restrictor, exhaust and a FMIC, so the boost is around 15psi. had the car on a dyno and the afr ratio was mostly in the high 11s and low 12s but spiked at about 12.9. Is this getting pretty dangerously lean? Thanks for any help. Also what AFR would you recommend tuning to when I get PFC?

[BlackRBS13]

A print out of the dyno sheet... power vs AFR & power vs boost would be able to tell me if its dangerous or not. The first one would help if thats all you have.

I will post a dyno sheet when if i can get ahold of one. Also what should the stock wastegate boost pressure be for the stock turbos? my car is boosting between 15 and 18psi. seems like that is higher than it should be.

[VB-]

12.9 isnt dangerous if you have timing to match, which out of a stock ECU shouldnt be too bad, but still dont drive it hard, i'd get it tuned properly first. that said i have seen cars (R34 GTR is the first one that comes to mind) that came out of racepace and was on a dyno elsewhere, its A:F ratio was 13:1 up top, and i believe thats just how it was tuned. i quizzed the dyno operator on it and said he'd seen it a few times from racepace adn it works fine, just less margin of error for crap fuel etc.

point is, i wouldnt say its bad if racepace is doing it (that said i could be entirely wrong lol)