Am I running rich for an N/A?

Ninety-Nine SE-L · Feb 6th, 2003, 02:45 AM

hey, I was jus taking a look at my old Dyno chart ans I noticed my A/F ratio hangs around 11 throughout most of the run. Is that too rich for an N/A engine? what's a good A/F for an N/A? for a Turbo?

himilefrontier · Feb 6th, 2003, 03:24 AM

Well,you probably won't hurt anything(except maybe the Cat)but it seems a bit rich to me.I think that you would gain some power if you got closer to the stoichiometrically correct ratio of I believe 14.4:1.I think max power is supposed to be around 13.5:1,but can't remember right now(I can't sleep).Hope this helps!

hpro123 · Feb 6th, 2003, 03:36 AM

Car manufacturers and Nissan in particular tend to run rich fuel mixtures at extreme situations (high rpm, high MAF load) in order to assure the longevity and reliability of the engine (rich mixture drops the combustion chamber temps).

They do that to the extreme in Turbo engines that have higher temps.

Your car is fine. I am not familiar with GA16 engines but if SR20s are any indication, you are fine.

N/A SR20s are programmed by the factory for AFR from 11:1 to 10.6:1 at WOT and 6800rpm.

Turbo SR20s are programmed by the factory for AFR from 9.5:1 to 9:1 at WOT and 6800rpm.

Chris

Ninety-Nine SE-L · Feb 6th, 2003, 03:52 AM

could I benefit by bringing it up to about 12 or 13? Would I gain/lose power? right now, I get terrible gas mileage (around 21-22 mi/gal)

hpro123 · Feb 6th, 2003, 04:01 AM

Your poor gas mileage indicates some other problem and cannot be explained by the factory-set AFR at high loads. There are a thousand things that may lead to low mpg and you sohuld definitely start looking for probable causes.

As for the AFR, how do you plan to bring it to ~ 13:1???

You are definitely going to see gains by going from 11:1 to 12.7:1 (theoretical ideal but may vary slightly with the motor and its configuration). Problem is that if it is not done properly you may handicap the car in the longevity/reliability departmetn.

Chris

Ninety-Nine SE-L · Feb 6th, 2003, 04:11 AM

Quote:

Originally posted by hpro123
Your poor gas mileage indicates some other problem and cannot be explained by the factory-set AFR at high loads. There are a thousand things that may lead to low mpg and you sohuld definitely start looking for probable causes.

I thought so. I am thinking either my O2 sensor, something wierd with my ECU, or my driving. BTW, that's my highway miles too.

Quote:

Originally posted by hpro123

As for the AFR, how do you plan to bring it to ~ 13:1???

got me, I was just giving the idea. I'm not sure what would make it run at a 13:1 from a 11:1.

hpro123 · Feb 6th, 2003, 04:21 AM

Quote:

Originally posted by 1997 GA16DE
I thought so. I am thinking either my O2 sensor,

Very probable. Has been known to increase fuel consumption. Change it.

Quote:

something wierd with my ECU,

Very unlikely. Usually if it fails you get Check Engine Light and you KNOW something major has gone down.

Quote:

or my driving. BTW, that's my highway miles too.

Highway eh? Unless you are full of speeding tickets it is not your driving.

Chris

nitestridar · Feb 6th, 2003, 07:08 AM

I have the same gas problem you do...
I am changing the O2 by the cat this weekend to see if that helps..

I also get a real bad smell from the vents when I go FT.

Ninety-Nine SE-L · Feb 6th, 2003, 12:49 PM

Quote:

Originally posted by hpro123
Highway eh? Unless you are full of speeding tickets it is not your driving.

Chris

well, lets just say I like driving @ WOT

. I don't have too many speeding tickets b/c I'm careful, but I usually drive between 80 and 100 on I-4 (that would be at night when it actually moves).

Nostrodomas · Feb 6th, 2003, 08:33 PM

Shifting over 3,000 rpm's, will produce higher mileage. The economical shifting points I believe are between, 2,000 and 3,500 rpm. So driving over the 3,000 rpm mark on the highway will give you a lower mpg.

Ninety-Nine SE-L · Feb 6th, 2003, 10:51 PM

yea, well of course that's true. you get more mileage when you're engine's turning slower. The problem with that is that I have an auto. That means 4 wide ratio gears and also, my car's not that powerful, unless I drive like a granny, I usually shift above 4k. also, I'm a hard driver. I like to hang onto that WOT.

javierb14 · Feb 7th, 2003, 12:52 AM

u might also want to run a higher octane if u alter the A/F.

himilefrontier · Feb 7th, 2003, 03:21 PM

Do you have headders?And if you do,is there a leak in them before the O2 sensor?if there is it could be causing you to read a false lean making your computer richen the mixture.That fuel mileage is horrible.I had a 98 Sentra Xe/5spd a few years ago that got 32 mpg delivering pizza(in the same general area I see that you live in)-and I drove it HARD!Is the car far from stock? Do you have a turbo or something(larger injectors?)that would increase fuel demand?

BORNGEARHEAD · Feb 7th, 2003, 11:32 PM

You can adjust your throttle position sensor to get a little richer or leaner.

Ninety-Nine SE-L · Feb 8th, 2003, 11:55 AM

to answer,
-I already run 93 octane b/c of my advanced timing. This is why I'm so ticked, at 21mpg, GAS IS EXPENSIVE!!!
-No header, all stock around both O2 sensors.
-Not sure how to adjust the TPS.

I think I'm gonna start with my first O2 sensor and go from there.