N/A's leaning out...
 

At what point should one worry about an N/A leaning out?

Intake/exhaust? Porting? Is it possible to free the flow up TOO MUCH, with mods such as the TB mod on top of intake/full exhaust, where the stock fuel system can't compensate? And if it matters, an s5?

Once you start porting then I would worry about running lean. NAs can handle running lean much better than turbos as well. Nothing some TII secondaries can't fix though.

NA injectors are big enough for ~250hp, which you won't get even with a streetport. You'd need a bridgeport and/or nitrous before you're near that. Manufacturers tune on the very rich side at WOT for safety reasons, and most cars will benefit from slightly leaner mixtures with more power and lower consumption. It's much easier to significantly increase airflow with a turbo, which is why they start to lean out when you go beyond basic mods. It's a lot harder to get NA's (any NA engine) up to that point, so fuel isn't such an issue.
The best thing to do is get your car on a dyno and get the mixtures logged. Then you'll see quite clearly if enrichment is necessary, or if you could run a little leaner in some areas (or even both). Your best bet for that is a piggy-back fuel controller like an S-AFC.

hey colby, IM me on AIM (OsborneStyle) and I will give you jamie knight's email address... hes from greenville and was running low 9s (1/8) in his n/a rx7 before it got wrecked. Im sure he could help you out with whatever you need to know about that new car. Also my friend wants to know if youre selling your exhaust and I think I may know whats with your "fuel cut" problem.

thx Chris, I'll IM you sometime to talk about that.

and thx again NZ and Ryde, I'm pretty familiar with how TII's lean out with simple intake/exhaust mods.. I might be venturing into the N/A world soon and wanted to know if it was possible.

But from what you guys are telling me, on a 91 N/A, I do NOT have to worrying about running lean with a full RB exhaust including header, Apexi intake w/ cold air box, ported intake manifold and the TB mod?

And as far as nitrous goes, as long as you do a wet setup, you should be fine shouldn't you?


Thanks again.

hey colby I sent the box out today!

i have 86 na, pretty much the same mods you have maybe a little more but not even close to lean. actually my a/f guage shows rich and i have taken the fuel back a bit with the safc. i don't think u shoudld worry

You can drive an N/A so lean that the car misfires and makes mo power but it won't detonate. Running lean is a non-issue with N/As, the only think you have to worry about is a lack of power. You probably won't get to that point even with porting (unless you max out injectors - not likely) because AFM style injection is very good at compensating for engine mods since it measures the airflow directly and adds the programmed ratio of fuel.