Nissan 370Z Forum - Intake, Header, HFC, CBE = Too Lean?

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- - Intake, Header, HFC, CBE = Too Lean? (http://www.the370z.com/intake-exhaust/16437-intake-header-hfc-cbe-too-lean.html)

i believe sharif or tony from f.i. said optimal is middle or high 12's or low 13's? 14.xx seems too lean?

Quote:

Originally Posted by kevin.z (Post 466112)

i believe sharif or tony from f.i. said optimal is middle or high 12's or low 13's? 14.xx seems too lean?

Correct, at idle it might run in the 14.x area because the system is constantly adjusting, but under load it should really be below 13.0 (not 100% sure on the exact range in 12.x though).

The Stoichiometric (ideal) A/F Ratio is around 14.6, that's the A/F ratio you want to run at idle and little loads (cruising etc..)

It is only that you go rich (12-13) A/F @ WOT because it helps keep the combustion chamber temperatures down which helps in avoiding knock and advancing timing safely

Quote:

Originally Posted by Zsteve (Post 466105)

so semtex is your AFR starting at 14 and then at high rpms going down to around 12? I thought it was suppose to go up when you get on it? When I was checking my AFR yesterday it would flucate alot but always seemed to settle around 14.xx, is this good or bad?

The higher the number the leaner your car is running, hence less fuel and too much air. The lower the number the richer your car is running, hence more fuel.

You will not hurt these cars with a lean condition under 3500-3000 rpm's. You can destroy your engine from detonation in the higher rpm's if your A/F is too lean. This specific car needs to have the A/F between 12:6 - 13:2. In my honest opinion 13:2 can even be a little lean but it is borderline. Yes, in theory the leaner you can make the car, the more power the car should make. However I have found with this car there is a happy medium where it likes to live. That medium is those safe numbers I listed above. Obviously if the car was running PIG rich it would make lass power. For example: if your A/F was in the low 11's to high 10's you would be dumping too much fuel....

Tony

To add one more thing, optimum A/F at idol is 14:7

Well it seems this thread may have answered my question that no one responded to on my own thread.

Seems i threw a lean code P0171, unless this is an 02 issue im wondering if i am indeed running to lean with out a tune. However after clearing the CEL my idle rpm returned to 600 from 1k.

___________________________
Stillen CBE, Gen'3s and Berk HFC

To add another thing, you need to try and take the A/F reading as close to the headers/manifolds as possible. Specifically in front of the cats if you have cats installed on the car. By doing this, you will achieve the most accurate number. Running it in the tailpipe will work but like I said is not ideal.

Tony

Quote:

Originally Posted by Nitex (Post 466136)

Well from reading this: Stillen CBE, Gen'3s and Berk HFC

It is a safe bet to say you are running too lean. Now if this is what caused the code, I cannot guarantee that. If one of the O2 sensors was damaged you would probably throw a different code, so we can rule that one out.

I would say it is time to get your car on a dyno and find out what that A/F is doing. If it is lean, you will need a tune. If you cannot afford a tune then put the stock intakes back on the car for the time being and I bet ten to one your A/F will go back to where it needs to be...

Tony

I will check it again tonight or tomorrow and confirm what my numbers are when stepping on it. Thanks guys.

No, what I meant is that IF your air meter is working properly that even with all the bolt on mods, the car should be able to adjust the fuel so that you do not run lean. In other words, the stock fuel system can keep up with the amount of power you will make with all of those mods. If you relocate or your air meter is NOT reading accurately, you could end up with a lean condition.

I wasn't really talking about the "power" itself rather the power compared to what the ECU can adjust to.

Basically, if you have a G3, you're better off getting the car on the dyno and obtaining your a/f ratios. OR...if you have the software, watch the timing during a pull. If you see timing start to decrease through the run, that means your car is going lean and the ECU is pulling timing to compensate...NOT good!

Nice numbers btw!

Quote:

Originally Posted by semtex (Post 465727)

I disagree.

I started off with a CBE and HFC. I never dyno'd before this, only after, so my baseline is with the CBE and HFC.

Baseline: Max = 291.7whp. My only mods were the Stillen cat-back exhaust and the Berk HFCs.

http://www.the370z.com/members/semte...1467494cd8.jpg

Then I went and added the G3 intakes.
After: Max = 306.4whp.

http://www.the370z.com/members/semte...re-14-7whp.jpg

Net gain = 14.7whp.

Then I added headers.

This first graph shows HP and A/F:
http://www.the370z.com/members/semte...209hpandaf.jpg

This one shows torque:
http://www.the370z.com/members/semte...9-042209tq.jpg

So I should be running really lean now, right? And when I get a tune and get my AFR adjusted, my HP should go back down as a result of the AFR correction, right? But it doesn't. And keep in mind that AFR correction is pretty much the only thing a tune is good for right now, because timing adjustments just get bounced back, so it's not like we're offsetting HP loss via AFR correction with HP gain via timing advancement.

Sharif at Forged Performance did my tune, and he made sure the AFR is where it ought to be.

http://i618.photobucket.com/albums/t...e102809_AF.jpg

Final number: 318.1

Unless I'm missing something, it does not appear that my gains from the G3 intake were at any point negated by AFR correction, which leads me to conclude that the gain I got from the G3 was legit, and not simply because it caused my engine to run lean.

When you tune, don't aim for "lean" you will end up with peak numbers, you want the car to allow timing to remain consistent so at times, actually running it "slightly" rich will not give you the peak numbers but it will give you an increase overall.

Of course, don't run it too rich...you want your a/f ratios to be a few points under "lean"
Also, if your car tends to pick up power at any point try actually adding a little fuel in that area instead of leaning it. You'll find that your timing will actually remain consistent VS getting that peak and then having the car pull timing to redline.

so basically once I put my CBE on the car considering i have the G3 and berk HFC i will need a tune immediately?

Quote:

Originally Posted by NewlyIMPORTed (Post 466571)

so basically once I put my CBE on the car considering i have the G3 and berk HFC i will need a tune immediately?

The "safe" thing to do would be having a dyno with an A/F meter to see where you are at. You can drive the car, but not beat on it too hard until you at least confirm that your air/fuel ratios are within tolerance. That and you could be giving up power by not having it tuned.

Better safe than sorry!

Quote:

Originally Posted by F.I. Inc. (Post 466152)

Ahh great thanks! I can afford the tune(aerospace engineer), i was just debating uprev Dyno tune vs Cobb ap or maybee oasis ? just needed to do the research but it seems i may be running out of time. I just hope i havnt done any damage.

____________________________
Stillen CBE, Gen 3's and Berk HFC

Quote:

Originally Posted by Nitex (Post 467375)

You have not done any damage, but you are probably just not getting the best gas mileage and all the power you should be, because the system is no running efficiently.

Quote:

Originally Posted by Nitex (Post 467375)

Hopefully you know I wasn't taking a jab at your financial status. I was just stating all of the options. Like Dreamer said, you should be fine just get a tune asap...

Thanks, Tony