Huge changes in LTFT's

1801 Views 3 Replies 3 Participants Last post by ms6ftw, Mar 8, 2011

Dephect

Discussion Starter · Feb 18, 2011 (Edited)

I got my DH a month ago and was checking everything out. I noticed my LTFT's were +3% at idle, PT acceleration was +14.7%, and cruising was +11.7%. My first thought was "that's gotta be off" even tho I had no idea what this meant. These have been my numbers for the last month with no changes After reading the tuning section of the forum, I've determined it's pretty imperative that I get an AP and I plan to place an order for one next week. This thread is a 2 part question.

1) I live in Florida so the temperature has crazy changes here. It was 50's-60's high, then randomly in mid Feb. we get a whole week of high 70's. Since the warmer weather im getting higher numbers in my LTFT's as high as +16% cruising and 5% at idle. I know that warmer air means less molecules per square inch, ect but wouldnt that make my car lean out the fuel trims to adjust to less air? I purchased the car with an MS CAI and I added a SU test pipe but I'm not sure if the filter has ever been cleaned. It also has the hydroshield on it. Could a dirty filter + hydroshield prevent the car from breathing that much? Would cleaning the filter see even a minor drop in FT's? As far as I know the LTFT's are the ECU's adjustments to meet target AFR's and reduce KR, but I have NEVER had KR (possibly because FT's are so high lol) and I figured LESS fuel would be added if less air is being pulled into the system because of temp., dirty filter, humidity, etc.

2) When I do get an AP, should I just calculate the MAF on a stock map or would I be able to run stage 2 with just the test pipe? ( read a thread somewhere a while back that claimed you could "get by") I know COBB says that you need a full exhaust but I dont have the funds for that right this second and I kinda want to stay away from stage 1 because of the super aggressive timing.

Sorry for the long winded post, but thanks in advance to anyone who can answer any of the questions :lol:

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dougefresh_

· #2 · Feb 18, 2011

1) Did you notice any difference in power with the large change in FTs? I'm wondering if you had a very minor leak that "patched" itself with the warm weather. I had no leaks, and then the sub 20F weather created a huge leak somewhere, and I'm only holding 14-15 PSI (instead of 19-20). A dirty air filter could block airflow, but that should result in your FT's becoming smaller (more negative) like you suggested. Fuel is added in the presence of KR... this has nothing to do with your FT's per se... there are separate fueling tables that come into play (which are richer) in the presence of KR. To get a handle on fuel trims, read the two stickies in this section "MAF 101" and "How to calibrate your maf." I understand you cannot until you get the AP, but that should give you a heads start.

Also, check for boost leaks. Build DJ's pressure tester with simple parts from HD/Lowes (go to Lowes). Search "How to find boost leaks" and it should come up.

2) You can run stage 2 with a TP + cbe... I'm not 100% on running Stage 2 with just a TP. I know a couple people were, but I forget who now. However, stage 1 maps have more aggressive timing than stage 2 maps, and many people get a LOT of KR with them (others don't). I always say to stay away from stage 1 maps for that reason. Do yourself a favor, and pick up a used cbe so you can run a stage 2 map, and there won't be a problem. You'll see your wgdc pinned at 99.06% as you have too much back pressure if there's a problem.

Hope that helps-

D

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