Are my fuel trims off?

[LKWTSI]

Having just installed a Walboro 255hp and AFPR, all 3 fuel trims seem to be going off the wall. My High and Low are at 119% and the Mid is creeping up the more I run the car. It started around 104% just after I did the install and now it's heading up towards the other 2, at 112%.

I understand that the higher these numbers are the ECU is getting the signal that I'm running lean and it's adding fuel to compensate. From the info', I've been able to get from the threads and my pocketlogger, 120% is max for 1g's. If this is the case I'm at the max( or near as can be) once I hit this the ECU can't add any more fuel to compensate and I'll be running lean at boost. I've dialed down the boost from 15 to 13 psi and it helped with the knock, by coming down a couple of counts.

So what could be causing this or am I interpreting this information wrong. I don't want to keep this thing running lean and would like to bump the boost back up to get the max power out the motor.

As a comparison before the fuel pump and AFPR install, I was running about 118 x 3 on the fuel trims.

 

[Mindslayer]

You don't have any fuel management. You need to turn down the boost 1-2 psi. And, mostly be worried about your HFT and keep it around 100-110% MAX. And then work on your LFT and then your Mid.

 

[LKWTSI]

You don't have any fuel management. You need to turn down the boost 1-2 psi. And, mostly be worried about your HFT and keep it around 100-110% MAX. And then work on your LFT and then your Mid.

I already did the boost lowering, but, what do I do about the high values? With stock ECU and no SAFC how can I get the trim values back down?

Even when I was running stock fuel setup and (maybe a little to much boost), my first logs after getting my logger showed 118%, so what other possibilities am I looking at that's driving my trims so high.

 

[Mindslayer]

Try to reset your ecu and drive up Tryon. But, if that don't work open your gap on your plugs by .1. Or you'll just need a Chip or fuel management.

 

[big_d]

I hate playing guessing games...If you plan on sticking with the 16g and don't plan on really going any bigger, I would find some evo injectors, safc, and a wideband and run some safe boost levels. You could always plan ahead and go with dsmlink and injectors of your choice, but that might be a little overkill for your goals...Until you find some sort of fuel management, lower the boost and keep knock down. Oh and keep the idc below 80-85%

 

[habitatguy187]

Vacuum leaks will make the car run lean, also any pre-o2 sensor exhaust leaks can throw the reading off. If you're good on both of those items then bump your fuel pressure up a little with the afpr.

 

[LKWTSI]

Vacuum leaks will make the car run lean, also any pre-o2 sensor exhaust leaks can throw the reading off. If you're good on both of those items then bump your fuel pressure up a little with the afpr.

Definitely no vac' leaks, but now you mention it I think I have a small leak at the head to manifold under the power steering pump bracket. I will be taking the motor out near the end of the year and getting it bored and re-gasketed. I'll take care of that then.

Until then, I guess I'll just back off the boost and save for a Link and bigger injectors.

 

[LKWTSI]

Try to reset your ecu and drive up Tryon. But, if that don't work open your gap on your plugs by .1. Or you'll just need a Chip or fuel management.

Tryon here I come, but I do prefer the 485 westbound

Oh and I'll try opening the plug gap and see if it helps. I had the ECU reset while doing the pump install and they went from 100 to 119 almost within 3 or 4 runs. So I'm definitely catching a problem from something.

 

[habitatguy187]

If your low, mid, and high trims are that far off you really need to up your fuel pressure as a safetry precaution, even with the exhaust leak.

 

[Mindslayer]

Tryon here I come, but I do prefer the 485 westbound

Oh and I'll try opening the plug gap and see if it helps. I had the ECU reset while doing the pump install and they went from 100 to 119 almost within 3 or 4 runs. So I'm definitely catching a problem from something.

I know what you mean. I've tuned on 485 before

 

[LKWTSI]

I know what you mean. I've tuned on 485 before

Every time I go to work I pull a log...

 

[LKWTSI]

If your low, mid, and high trims are that far off you really need to up your fuel pressure as a safetry precaution, even with the exhaust leak.

really You think I should add more pressure? Am I thinking you're thought is more fuel being dumped in to the cylinders will lower the leaning out some. Does this work.

 

[habitatguy187]

really You think I should add more pressure? Am I thinking you're thought is more fuel being dumped in to the cylinders will lower the leaning out some. Does this work.

Basically what's happening now is your car is (or thinks it is due to the pre-o2 sensor exhaust leak) that it's running lean, so the computer adds more fuel. What's dangerous about this is that it doesn't add any more fuel than normal when you're going WOT (wide open throttle)

So if you bump up the fuel pressure to where the fuel trims reach around 100 then you should be fine to do WOT pulls.

 

[->PrOjEcTGS<-]

What's dangerous about this is that it doesn't add any more fuel than normal when you're going WOT (wide open throttle)

But remember if it's a pre-turbo/O2 sensor exhaust leak then he's not actually running lean it's just getting reported back to the ECU that he is. Also, remember that the stock open loop fuel maps are really rich and even if he is running leaner it's not going to melt anything unless he's knocking really bad.

OP, what is your fuel pressure currently set at? I agree that you should bump it up a little bit till you see the low fuel react to the changes. If you have to go really high with it (like up into the 50's) then something else is wrong.

Who installed the pump? Have you had this problem ever since the pump/afpr was installed?

 

[habitatguy187]

But remember if it's a pre-turbo/O2 sensor exhaust leak then he's not actually running lean it's just getting reported back to the ECU that he is. Also, remember that the stock open loop fuel maps are really rich and even if he is running leaner it's not going to melt anything unless he's knocking really bad.

I agree that it's most likely due to his exhaust leak, but even so you can never be positive, I mean yeah you're losing a lot of air before the o2, but you're also losing a lot of gas that the o2 would pick up too.

It's just something I'd do for safety's sake until he got the leak taken care of.

 

[LKWTSI]

Good points on all counts, about the pre O2 leak. I'll try bumping the fuel pressure just to see, but the pump install and AFPR were done recently and pre install the trims were at 118% across the board. So I don't know if they are any worse since the install I just know they haven't gotten any better.

The pump and AFPR DID help with the knock count though. Pre install I was getting upwards of 20 counts at WOT and now I can see only 7-9 if I really get on it. Most of the knock is now caused by lifter tick, pretty sure about that, so at least I know that helped a little bit in my quest for power.

 

[habitatguy187]

The pump and AFPR DID help with the knock count though. Pre install I was getting upwards of 20 counts at WOT and now I can see only 7-9 if I really get on it. Most of the knock is now caused by lifter tick, pretty sure about that, so at least I know that helped a little bit in my quest for power.

If you're getting that much knock, and the fuel pump and afpr helped with the knock, then you probably are running lean. What temps/boost/turbo are you seeing these 7-9 counts?

 

[LKWTSI]

I'll have to get on my laptop and post the log, later tonight.

But to give you a quick detail of setup- Evo3B16g, 13psi boost, running about 120-130*F intake temp, and 37psi base fuel pressure. Other than that I'll get a log posted later to look at the O2 and other readings that I'm seeing since the install.

 

[LKWTSI]

Here's the log.

 

[chanley talon]

What data logger are you running? Tmo?

 

[bastarddsm]

I'd say that knock your getting is real, but it might be just a junk knock sensor. have you replaced it?

By your O2's at wot, your not running lean.

Also keep in mind that the fuel trims DO NOTHING when the car is in open loop. The trims are just there to make the O2 sensors job easier. They record how much compensation the O2 trim has been making in those three areas, and then apply them to help keep the 02 trim as close to 0 as possible. This keeps the rich-lean swings of the 02 as small as possible to keep you as close to stoich as possible and get good mileage.

 

[LKWTSI]

Update..

I replaced the knock sensor a few months ago, the old one was completely shot. I replaced the O2 sensor last week as, I thought it was going bad, based on a new thread and responses to my O2 readings, it looked like it was dodgy.

So as far as this OP, I will add that since the new O2 sensor I reset the ECU and started with 100% across the FT's. Within a few miles the Low FT had shot up to 115% and is currently at 118%. The High stayed low for a while, but has since crept up to 116% and the Mid, is still trailing in the 110, but slowly working up.

I upped the fuel pressure a little and turned down the boost to 13psi. I may try bumping the fuel pressure up a little more and see what happens.

As far as the datalogger, I'm running Pocketlogger through a palmIIIx.

Thanks for keeping up with the thread. I hope to have this thing cured sometime.

 

[habitatguy187]

Three questions -

1. Is the an auto or manual car?

2. What did you turn the fuel pressure up to?

3. When was the last time you changed your fuel filter?

 

[LKWTSI]

Three questions -

1. Is the an auto or manual car?

2. What did you turn the fuel pressure up to?

3. When was the last time you changed your fuel filter?

1. Manual
2. 39psi
3. 1 month ago, when I installed the 255 and AFPR.

What are your thoughts??

 

[habitatguy187]

1. Manual
2. 39psi
3. 1 month ago, when I installed the 255 and AFPR.

What are your thoughts??

Autos require a higher fuel pressure, that takes care of questions one and two, and I thought maybe your fuel filter was massively clogged causing poor flow. Have you pulled any of the honeycombs out of your mas?