Decel Fuel with AEM

FattyBoomBatty · 05-18-2009

I seem to only see the gauge read lean on decel at very low rpm (around 1500 and below), anything higher and it will go very rich on decel.

in the little box for decel fuel my settings are:
Fuel off above RPM: 2000 RPM
Fuel off below load: -12.06 PSIg
Fuel off below TPS: 1.95 %
Fuel off Coolant min: 30 degrees F

I may have just answered my own question when I saw the TPS was labeled in percentage and not voltage.

I did a quick check with the calculator and 1.95% is like .08775 volts (assuming 4.5 is the maximum which it is pretty close to that).

Can I raise that percentage up to say, 15%? Because I've watched on the computer with the car running, sometimes the closed throttle voltage will vary a bit, and go higher than .08 volts (like up to .45 volts once if I recall correctly (I may have done a TPS reset then)).

**Shane@DBPerformance** · 05-18-2009

You might need to raise the "Fuel off below load". You want the TPS % to a little over whatever it is with your foot off the gas. You usually need some amount of room for flaky readings or slight changes in voltage.

Let off the gas at 3000-4000 rpms and see how much vacuum the car pulls on decel. Set your "Fuel off below load" a bit above that. If it pulls 12 psi of vaccum then try 11.5 or something. You just don't want decel fuel cut happening when you are actually trying to cruise.

FattyBoomBatty · 05-18-2009

Makes perfect sense, thanks!

FattyBoomBatty · 05-24-2009

Finally got this done, and it's much better now. I didn't touch the TPS setting, just the load was good enough, I set it to -10.89, anything lower than that wouldn't trip the function until below 3 grand. It just doesn't pull a ton of vacuum. I also set the rpm limit to 1800 since I am usually still decelerating there. It could even go lower, but it seemed fine to me for the time being.

FattyBoomBatty · 06-09-2009

Last week I discovered I had a vacuum leak coming from the #4 injector o-ring in the manifold. SO, I fixed that and it changed the vacuum a bit and also the fueling stuff on the AEM. I went back into the decel box and dropped the threshold to like -9.8 psi and it has been working perfectly ever since.

But my cruising afr's were way more rich all of a sudden, I figured it's because it's not getting as much air as before under vacuum conditions. So on the way back from Branson yesterday, I whipped out the laptop and did some tuning for low load cruising, and got the AFR's back up to where they should be, in the high 14's and once in a while I'd see 15, but only for a second. I managed 26mpg and 452 miles on that tank, the first bit was in some hilly terrain before leaning it out.

Then after that it started getting cold in IA, and the AFR's went rich, kindof back to wherethey were before, mid 13's sometimes high 12s cruising, it was kindof pissing me off, but I figured it had to do with air temps.

Am I right to assume that? Conversely, when it warms up again, will it go back to being leaner? or am I going to have to tune for different air temps every time a cold front passes through?

**Shane@DBPerformance** · 06-09-2009

Check the air temp compensation table and try adjusting it versus the air temps you are seeing. With no air temp correction at all, it should run richer when it's hot and leaner when it's cold. If it is way over compensating(too much fuel) in the air temp table for colder temps then try lowering it down some at that temperature. Going from 14-15s to 12s though seems like way too much though for the kind of values you normally see in the air temp table. Make sure your air temp sensor or coolant temp sensor hasn't failed and inturn giving extremely cold readings to the AEM and making it run really rich.

FattyBoomBatty · 06-09-2009

Ok, I will do that. I wasn't able to find an air temp compensation table earlier today when I was looking, but I'll just search the PDF instructions.

nevermind, found it. Just being dumb.

niterydr · 06-09-2009

Quote:

Originally Posted by FattyBoomBatty

Ok, I will do that. I wasn't able to find an air temp compensation table earlier today when I was looking, but I'll just search the PDF instructions.

Fuel --> advanced fuel --> fuel trims.

FattyBoomBatty · 06-09-2009

Thanks!

FattyBoomBatty · 06-10-2009

Well, if the intake temps were low enough, it might have been adding fuel, but driving around town, it was acting fairly normal, so I don't know. I'll be observing and noting things over time. I did start messing with the Accel pump function because it was herky-jerky if I tipped in too much, and I had often seen a lean reading in the beginning, but had trained myself not to stomp the gas, but rather roll on the pedal.

So, I added more fuel, tried it out, same thing, added some more, and after a few repeats of this process, I decided it was getting worse, so I took out a bunch of fuel, and things started improving, and eventually I got it so I can romp on the thing off boost in any gear and it just goes, no missing or whatever, then the turbo comes on and things start making loud noises. It's great and the car actually feels faster because of it. I guess it's because I can give the turbo maximum load so it probably spools faster/sooner, or I'm just delusional.

Anyway, it's all working out, but I have another question in regards to the accel fueling. What is a good AFR to shoot for upon tip-in? right now it usually goes into the 10's then evens out in the mid 11's like it does on boost. Should I take a bit more out and make it so tip in only goes to low or mid 11's or is it better to have a good, rich squirt of gas? The reason I ask is because if less fuel made it run good, maybe even less will make it run great?

**Shane@DBPerformance** · 06-10-2009

It depends on the load it makes, usually somewhere around 13s will feel good though. But even widebands often aren't fast enough to catch whats really going on with tip-in and the best thing is to just go by how the car feels. Often it's just trial and error on the street and trying not to screw up the throttle response at one RPM or temperature when you get it good at another range. At least they added the Accell vs Coolant temp table in the 1.19 version. The Accel limit and Accel TP Sensitivity can make the biggest changes in how the tip-in feels, if playing with tables doesn't seem to help enough. But make sure that the TP Sensitivity and the Accel dTPS trigger aren't so sensitive that accel fueling is constantly coming on during normal cruising and making it run rich from it dumping fuel at the slightest movement of your foot.

Super Bleeder!! · 06-10-2009

This should be a thread you have to pay to read!

FattyBoomBatty · 06-10-2009

Maybe there can be a special donate button at the top.

Shane, I truly appreciate your help with all this. Thank you. After getting a ride in that white starion, I decided that 170 more whp is a good idea. So after a while I'll be bringing it back for an e85 tune.

niterydr · 06-10-2009

Quote:

Originally Posted by ecoli

It depends on the load it makes, usually somewhere around 13s will feel good though. But even widebands often aren't fast enough to catch whats really going on with tip-in and the best thing is to just go by how the car feels. Often it's just trial and error on the street and trying not to screw up the throttle response at one RPM or temperature when you get it good at another range. At least they added the Accell vs Coolant temp table in the 1.19 version. The Accel limit and Accel TP Sensitivity can make the biggest changes in how the tip-in feels, if playing with tables doesn't seem to help enough. But make sure that the TP Sensitivity and the Accel dTPS trigger aren't so sensitive that accel fueling is constantly coming on during normal cruising and making it run rich from it dumping fuel at the slightest movement of your foot.

Expanding on this excellent post:

Best way to monitor that is to watch your accel fuel trims and triggers. When they are "too sensitive" you will see your AFR oscillate and the triggers will constantly be moving, if that’s the case, bump down the sensitivity or trigger point. Most cars end up in the 50-80% sensitivity and fewer than 10 for a trigger with good fueling.

Remember the key to fueling is to use it as a cooling agent. It is there to keep the flame under control, there is no "magic" AFR besides STOIC, everything else is a compromise of burn compared to power potential.

lucasoil4u · 06-13-2009

holy shit that makes my brain hurt!