Help!!!! LTFT's and STFT's

[hcbr929rr2]

So I installed my Cobb Sri last weekend and have been monitoring everything to make sure nothing crazy is going on, and here is my dilemma.

My LTFT's are anywhere from +7 to +17??? but afr is fine if not a bit rich, fuel rail pressure is fine, even STFT's under wide open throttle are at 0.0, all connections are tight, no leaks, stock bpv, any thoughts? I am in Denver so being a mile high will mess with cars a bit but I'm fairly confused here, why would my LTFT's be so far off if my STFT's are ok?

[erod550]

LTFTs are set over time, so at some point your STFTs were up there too. You could always try disconnecting the battery to reset the LTFTs and see what they do. If your STFTs are fine now, then the LTFTs will settle in at a normal level. With the intake though you're getting more air in there so it's natural that your fuel trims will be a little higher. Usually shouldn't see anything over +10 though.

[Mikedubs]

Elevation plays a part of this in my experience. I know when I go driving through the mountains my fuel trims go up a bit.

[I`m Batman]

You need to recalibrate your MAF... with a tune like HyperTech or AP. I had the same problem until I got the HypterTech and set it to the correct intake type. Now my LTFT is at -5.5 at idle and +6.2 to +7.0 at WOT. Very similar to stock.

My CX-7 LTFT and STFT goes crazy with an aftermarket intake. So, I had to switch back to stock until there's a tune available. Or find an intake with the same diameter as stock.

[hcbr929rr2]

ugh, now I went to lunch and I'm up to 18%, I don't understand though cause STFT never went past +8.6% to -8.6% think I should just reinstall stock til my AP, or could reseting the ECU be worth a try?

[erod550]

Is this at idle or WOT or what? There are several different throttle position thresholds which each have different trims. And like I said you could try resetting the ECU and see what happens. I don't think you need to go back to stock. The ECU is doing its job and adjusting to keep the AFR where it should be.

If the AFRs are good, then ultimately that's all you need to worry about. If the trims start getting up to +20-25 and the AFRs are going leaner than normal, then you might have a boost leak, but if the AFRs are staying where they should and just the fuel trims are fluctuating a bit, then you should be fine.

[kingtut]

ugh, now I went to lunch and I'm up to 18%

Mine did the same thing. It was either HT/AP or go back to stock and stop constantly worrying about it.

I miss the extra 'oomph' the car had with the SRI/TIP:(

[hcbr929rr2]

At idle ltft sits at around 8%, under light load i get aprox 10.5% and full throttle 18%, but stft at wot is 0 and while normal driving fluctuates between -8 to +8, maybe i should check my tip connections and stock bpv for leaks?

[kingtut]

At idle ltft sits at around 8%, under light load i get aprox 10.5% and full throttle 18%,

IIRC, mine was nearly identical. (fwiw)

[Shadowden]

I miss the extra 'oomph' the car had with the SRI/TIP:(

You aren't the only one.

[~Barn~]

My understanding is that if your LTFT is +/- (8) at idle, then you are good to go. Assuming of course everything that Eric said about AFR.

[erod550]

I honestly think it's fine. It will get better once you get an AP. It will be the exact same amount of air and fuel going in there (maybe a little less fuel because of the tune) but the fuel trims will read differently because the MAF will be calibrated. The problem now is more air is going in than it's reading so it has to add fuel to compensate to get the AFRs to the target. It's just what happens when you install an intake with a bigger diameter MAF housing.

As long as the AFRs are ok and the fuel trims aren't maxing out and throwing CELs, you're almost definitely fine. But when that happens your AFRs will be going lean too. I had a boost leak and at idle my fuel trims went into the over +20 range and my AFRs were dropping to like 17 and I was getting CELs. What you're describing is nothing like that and everything seems fine.

I assume your fuel pressure is good at WOT too (1600psi+)?

[hcbr929rr2]

well on my way home I spiked to 19.5% LTFT so that was enough for me to swap back to stock for now, yeah full pressure was spiking at over 1800 then settling at around 1700-1750, my afr was pretty consistant at 11.8 to 1 at WOT, I went back to stock and the funny part is the only things that changed are afr (is now back to 10.6 to 1) and LTFT is now -7ish at idle and +6.2 at WOT, the STFT, Ignition advance, boost, and fuel pressure are all pretty much exactly the same, granted I only have about 5 miles logged after going back to stock but I'm guessing it should all stay pretty consistant, I'm confused lol

[I`m Batman]

There's nothing to be confused about. Your MAF is calibrated to the diameter of your stock intake. You then stick a Cobb SRI which has a larger diameter where the MAF is so you're getting more volume of air passing through at the same air speed but your CPU still thinks that it's getting the volume of air as if it was still stock. So you're getting unmonitored air into the system and your CPU had to add more fuel to compensate. If you let it go, you'll probably eventually get a CEL.

[hcbr929rr2]

Well i guess what I'm confused about is if STFT didn't change then why would LTFT change so drastically? I was under the impression LTFT bases its corrections off of input from STFT, and STFT bases its corrections off of the MAF readings? All of this is fairly new to me, i'm used to b series hondas from 15 years ago where this didn't matter with bolt ons lol maybe my brain is just fried from trying to understand all this haha