Bouncey A/F?? Using a Wideband.

[Dave]

I just installed my AEM WB 02 sensor. Sitting at 13psi once I nail it the A/F will go to 10.9, then climb to 11.3, fall back to 10.6 then stay at 11.1, and it continues to bounce between the extremes.

Does everyone's do this? Am I just looking for a safe high point of not to reach?? Is 11.5 too high, or 12.0 the highest on a safe note? Not sure if there's a real HP difference between .5:1, I'll have to jump on the dyno to find that out for sure.

Thanks,
-Bryan

[turbovanman²]

Moved it to the right section Bryan, ;)

[Marcus86GLHS]

"...the A/F will go to 10.9, then climb to 11.3, fall back to 10.6 then stay at 11.1, and it continues to bounce between the extremes. ...."


that seems pretty normal, that range is not too wild. with forced induction you'll never seen a/f ratios pinned like on an engine w/o a turbocharger.

a generally accepted safe compromise between power and reliability would be in the range of say 11.5 - 12.2 for your mixture.

[8valves]

Are you still running a stock ECU? I've never had a wideband on a car with a stock ecu in a TM, but in some of the imports I've dealt with they've oscillated quite similarly running stock electronics.

Once you have a nice tune on the car they become much more solid, although I've never seen one sit dead steady on a single number.

[Dave]

Are you still running a stock ECU? I've never had a wideband on a car with a stock ecu in a TM, but in some of the imports I've dealt with they've oscillated quite similarly running stock electronics.

Once you have a nice tune on the car they become much more solid, although I've never seen one sit dead steady on a single number.

Aaron, yes I'm still using the stock ECU and I plan to for a while longer. I may stick in a quick S3 computer from Cindy, but that's about as far as I'll take it. That wont matter for my intake will it? ;)

I thought it would sit at a single number, but as long as I'm tuning for the high number during the oscilation then I guess I'll be fine. Thanks guys.

[8valves]

Aaron, yes I'm still using the stock ECU and I plan to for a while longer. I may stick in a quick S3 computer from Cindy, but that's about as far as I'll take it. That wont matter for my intake will it? ;)

I thought it would sit at a single number, but as long as I'm tuning for the high number during the oscilation then I guess I'll be fine. Thanks guys.


I don't know. I've never ran one of their ECU's so I don't know how they run a car to begin with, let alone when you get into some of the larger airflow modifications.

[Dave]

I don't know. I've never ran one of their ECU's so I don't know how they run a car to begin with, let alone when you get into some of the larger airflow modifications.

I definately have the setup to cram in a boatload of air. Do you think the intake will affect my A/F or EGT's?

[8valves]

I definately have the setup to cram in a boatload of air. Do you think the intake will affect my A/F or EGT's?

Most definately.

[Dave]

Most definately.
I can guess the intake will aid in higher A/F's (more air is obviously coming in) so will that also make my EGT's lower?

[Speedeuphoria]

I thought it would sit at a single number, but as long as I'm tuning for the high number during the oscilation then I guess I'll be fine. Thanks guys.


thats why datalogging is king:thumb:

[GLHNSLHT2]

sounds like some tuning to the Pumping efficiency table is in order or does it bounce holding 13psi and holding the rpm steady with the brakes? Cause as your rpms climb the fueling changes obviously.

[Dave]

sounds like some tuning to the Pumping efficiency table is in order or does it bounce holding 13psi and holding the rpm steady with the brakes? Cause as your rpms climb the fueling changes obviously.

I'll look at that later tonight.

[Dave]

I installed a cut out raiser today just temporarily (actually it's just a G-valve, but like I said, temporary ;)). I turned the boost up from 13psi to 14psi and my A/F rocketed from 11.3:1 to 12.2:1. :eek: The cut out raiser wouldn't have done this as it doesn't supply extra input past 14.7, I stayed at 14psi. I'm gonna go play with it some more right now, I'll post what I find.

[Dave]

Okay I tried to take a video of all my gauges while I wrapped it out through 2nd gear but the quality really sucks. :( My parents need to buy a better camera. ;)

Anyways I did learn a few things. I did a comparison from 12psi vs 14psi. Changed nothing else and just saw that 2psi equals roughly .2:1 A/F. Today the A/F seemed a bit more steady. Weird.

[GLHNSLHT2]

boost level has nothing to do with what a/f you're getting. Example. If you're running 10:1 at 10psi, turning the boost up does not nessacarily mean you're gonna lean to 12:1. Why? Because the computer adds more fuel for more boost. So say at 10psi you have (just for the example) 30 milliseconds of fuel going in at 3000rpms, K? No you crank the boost to 12psi at 3k rpms. Well the computer see's the higher boost level and say's ok for this level I need to increase the fuel by 5 milliseconds. So at 12psi at 3krpms the a/f should stay the same at 10:1 if everything is setup right. You can do this for 11.5:1 or 12.0:1 wherever you like to run your a/f.

The reason you probably saw leaner a/f's is because the cutout raiser is starting bleed off some air, causing the Map to see less pressure than what's actually in the intake. The map tells the puter I'm at Xpsi instead of Ypsi and need to lean out a bit. Voila. Now your a/f's go leaner.

[Dave]

boost level has nothing to do with what a/f you're getting. Example. If you're running 10:1 at 10psi, turning the boost up does not nessacarily mean you're gonna lean to 12:1. Why? Because the computer adds more fuel for more boost. So say at 10psi you have (just for the example) 30 milliseconds of fuel going in at 3000rpms, K? No you crank the boost to 12psi at 3k rpms. Well the computer see's the higher boost level and say's ok for this level I need to increase the fuel by 5 milliseconds. So at 12psi at 3krpms the a/f should stay the same at 10:1 if everything is setup right. You can do this for 11.5:1 or 12.0:1 wherever you like to run your a/f.

The reason you probably saw leaner a/f's is because the cutout raiser is starting bleed off some air, causing the Map to see less pressure than what's actually in the intake. The map tells the puter I'm at Xpsi instead of Ypsi and need to lean out a bit. Voila. Now your a/f's go leaner.


Makes sense! I'm learning a bunch now. Thanks a lot. :)

[MiniMopar]

That's really only true if the cal is perfect, which it isn't...even from the factory. With no MAF and no O2 feedback at WOT, the ECU is making a bit of a best guess about how much fuel to put in. The A/F will wander for a given boost pressure through the RPM range and what you are seeing it pretty close to what I see most of the time. The bouncing is a little weird, though.

[t3rse]

first off, you do understand that a lower ratio is richer right? those ranges are fine. I wouldn't go leaner than 12.2 over 18# though. 10.X is too rich. Look for between 11.5 and 12.0. I've gone as high as 12.7 (accident) with no detonation, but not wise to do with stock internals. With a good tune the a/f will be steady spot on. When you actually tune one of these things you'll see that everything is very linear, so moving a little bit is normal on a stock ECU. Why do you use a cutout raiser to hit 12#?