Air Fuel Ratio Setting

[GeKo]

My girlfriend is buying me a AEM Uego, and i was curious on what the settings should be at? im going to tune the air fuel ratio with my SAFCII, and i know it should be running between to numbers but i cant seem to find them when i search it.

Just need to know,
Thanks!

 

[architechnik]

It depends on what kind of boost you plan on running. The for normal cruising, the ideal A/F ratio is 14.7:1 and that will result in the most efficient burning. For running boost, though you'll be getting knock real fast.

For a conservative level, between 12:1 and 13:1 would be fine. If you're running a lot of boost or getting into some aggressive driving, as most of us are, you'll want to shoot between 12 and 10.5. If you're still hitting a lot of knock at 10.5:1, then you've got some other issues and should consider getting a meth/water injection setup or a bigger intercooler.

 

[DSM4me44]

Are you talking about the ideal air/fuel ratio?

If so, it would be 11:1

 

[sbengineering]

Best Power 12.5
Be safe and not get much carbon buildup 11.2-12.2
Looking for nice trap speeds. Lean out to 13.2 in top end.
and we can go on and on.

 

[Zenja]

It should be around 11:1 under boost - 12:1 or leaner is too lean with pump gas under most circumstances.

 

[GeKo]

Thanks alot guys!!

 

[livedsm4g63]

i have always aimed for 11.5:1 anything above that your asking for trouble.

 

[b00sted]

11:1 at peak torque and leaning out just a bit to 11.5:1 as you get to peak power. For cruising, as close to 14.7:1 as you can get while maintaining smooth driving(no bucking, etc.) 14:1 or so should be a good number to shoot for while cruising.

 

[Maranello993]

how am i still seeing 10.9:1 AFR on my PLX devices sm afr when im running 17 psi on an E3 16g and and evo IX pump? And why does the boost DROP OFF to 15psi at higher rpms?

 

[Colt4G63 also]

how am i still seeing 10.9:1 AFR on my PLX devices sm afr when im running 17 psi on an E3 16g and and evo IX pump? And why does the boost DROP OFF to 15psi at higher rpms?

You are still seing 10.9:1 because that's what your AFR really is most likely, (nothing wrong with that) and boost drops off to 15 because you've exeeded the maximum volumetric efficiency of your turbo and/or manifolds. Either that, or it just spikes to 17.

 

[Hubbard 0]

how am i still seeing 10.9:1 AFR on my PLX devices sm afr when im running 17 psi on an E3 16g and and evo IX pump? And why does the boost DROP OFF to 15psi at higher rpms?

You might be leaving a little power on the table, but this is a great and SAFE AFR to run.

 

[Maranello993]

yeah it probably was a spike. There's NO WAY my ported evo 3 is running outa breath at 17 psi. It has a ported 2g mani, tubular 02 housing, catless dp, and 80mm catback behind it.

My injectors are still stock 450cc, i guess the IX pump is putting out alot of pressure?

Maybe the 1gbov is starting to leak and my UICP is a neckdown right now too (i can run more PSI but stay richer than normal due to less flow?).

Edit: I just read the MBC manual and it says the spring it comes with is only good up to 5 psi over stock, so I have to put in the heavy spring.

 

[Bender]

At 18 psi, even with the bigger pump, your injectors are experiencing too high of a duty cycle. Good injectors for a 16g are 650-680's. I believe that is also the max size you can run on the AFC without interfering with timing.

With too high of an injector duty cycle, you can run a little lean (even if AFR is showing rich). This is where EGT tuning helps. The 650 injectors will lower your IDC, and keep you from leaning out, and keep the boost from dropping off.

 

[gettingwop]

I am willing to bet your injectors aren't the issue here. I bet you have a leak somewhere.

 

[zhjiln]

for WOT ....anything in the 11 range is great... 12 im wouldnt recommend but its not the end of the world ...

 

[Hubbard 0]

I still wouldn't recommend anything leaner then 11.3:1 or so at WOT.

Though we are straying from what the OP is asking, which is what he should expect at WOT.

 

[JayRolla]

I agree with the post above mine, all these people saying anything leaner than 11.3 afr at WOT on pump gas is crazy. Stock afr on a dsm in is around 9.5:1 and it rich to be real safe.

On pump gas shoot for 10.5-11.1 afr. I myself never have gone leaner than 10.9 and it seems to like the most boost.

On e85 or race fuel then yes you can shoot for 11.5-12.5 afr as long as you feel safe and you dont get detonation.

For a conservative level, between 12:1 and 13:1 would be fine.

I dont think any car in the world that is boosted at any psi level should run 13:1 at WOT. Talk about bye bye motor.

 

[dsmfa9nutter]

18lbs with an evoIII on 450's? Are you nuts?

 

[spooled_u_1st]

18lbs with an evoIII on 450's? Are you nuts?

That's what I was thinking. You do log your IDC's right?

 

[Maranello993]

it isn't 18 lbs, my boost gauge isnt all that great but it might be spiking to 16/17 then settling at 15. I only did this experiment one night, one time and i didn't get why the afr's were so rich. This car is driven once a week or less at 14/15 psi.

 

[JayRolla]

how am i still seeing 10.9:1 AFR on my PLX devices sm afr when im running 17 psi on an E3 16g and and evo IX pump? And why does the boost DROP OFF to 15psi at higher rpms?

Boost drops off because you have a mitsu turbo and thats what they do. I hit 32-34psi and drop too 24-26psi at redline. The crappy housing cant keep up with the flow.

You are running rich because when you add boost it also adds fuel pressure since fuel pressure rises 1:1 with boost. Most people with loggers and no wbo2 have issues tuning because they think they should add fuel when adding boost when its the opposite.

If you have enough fuel and keep adding boost the motor will just run extremely rich. I have to pull 25% fuel at WOT to get a good 11.5:1 on e85.

ALSO FOR THE PEOPLE ASKING ABOUT AFR. IF ON PUMP GAS DONT GO LEANER THAN 11.1. YOU CAN BURN A VALVE RUNNING LEANER THAN THAT.

 

[Maranello993]

I don't think an e3 would do that, that's why I got rid of the t 25. It's doing that because of the boost controller spring is too soft. I found that out by reading the manual . I have a heavier spring but I'm not going to run 17 pounds on a regular basis anyway.

And for the OP, definitely do not run leaner than 11.1:1. Those numbers ranging from 12 to 13:1 are ridiculous, I would be scared shitless if my AFR was that high under WOT.

 

[JayRolla]

I don't think an e3 would do that, that's why I got rid of the t 25. It's doing that because of the boost controller spring is too soft. I found that out by reading the manual . I have a heavier spring but I'm not going to run 17 pounds on a regular basis anyway.

And for the OP, definitely do not run leaner than 11.1:1. Those numbers ranging from 12 to 13:1 are ridiculous, I would be scared shitless if my AFR was that high under WOT.

No the 16g's do not hold boost. Under 20psi it should hold it fine. Its when you get above 20psi it really likes to drop off the boost. Under 20psi you should see about a 2psi drop at high rpms. Thats why Im going with a holset. Tired of not having the boost I want at high rpms.

 

[Justinawd]

I was always told ideal was 12.6 but that could be wrong ...

 

[Hubbard 0]

I was always told ideal was 12.6 but that could be wrong ...

Not for anything running straight 93 octane. Maybe that's the case with E85 or meth injection, but not regular pump gas.