Whipple Fuel Trims

Car hasn't been running too well lately. Way down on power ever since header install. No check engine codes. Brand new NGK plugs gapped at .028. Most recent Whipple tune. 93 octane from 2 different Sunoco stations. I'm awaiting my shop to have an opening to look over everything.

In the meantime I used the flare tool to data log my 8 minute, 2 mile commute to work this morning. Fuel trims were as below.

LT-B1 min -2.31 max 13.28
LT-B2 min -3.90 max 7.03

ST-B1 min -29.68 max 7.81
ST-B2 min -29.68 max 10.15

I do get a whistling type of sound when cruising in and around 2,000rpm, but can't tell if it is supercharger whine or coming from the bypass valve. I inspected all hoses and they appear in place. I also checked out the video from Ken at Palm Beach about the bypass oring being installed incorrectly. I contacted Whipple over the weekend and was advised my unit was put together prior to shipping, so that shouldn't be an issue.

I have an audible exhaust link where the headers step down to 2.5 to meet the cat back, but I don't believe that would effect performance. I'm having a local muffler shop cut out the short 6 inch 2.5 section and replacing with 3 inch pipe so that it will be a true 3 inch all the way back. The exhaust leak will be addressed at that time.

Nonetheless, how do those fuel trims look?

Fuel trims for sure could be affected by an exhaust leak at the header collector. Your LT fuel trims are in spec.

I never really looked at the whipple data log software before but as i know fuel trims those look terrible,but again whipple software maybe setup.differently.

But also look F1 said a exhaust leak up by the header will cause fuel trim issues,the bigger the leak the worse the fuel trims.

I believe the leak I have is right where the cat back hooks up, so beyond both 02 sensors. I was under the impression if an exhaust leak is after the 02 sensors it wouldn't have too much of an effect.

Nonetheless, there may certainly be a leak elsewhere. Hard to tell without a lift and the car being as low as it is. I have an appointment with a local muffler shop tomorrow to have a 2nd set of eyes on it.

I'll keep you guys posted.

U dont want to have any leaks atleast 12 inches from the 02 sensor,also u said u heard a whistling noise,make sure u dont have any vaccum leaks.

Instead of looking at the overall range of fuel trims, you need to look at what you are doing while the trims are at their max. For instance, if your idle LT fuel trim is +13%, then you probably have a vacuum leak. I actually have a problem with high fuel trims when the weather is hot and I'm in stop and go traffic. Still trying to figure it out.

I've noticed that the 132mm throttle body makes a whistling noise under light acceleration sometimes, so that might be what you are hearing. To me, it is high pitched, almost like a metal on metal noise, but it is completely normal.

Ruiner46 said:

I've noticed that the 132mm throttle body makes a whistling noise under light acceleration sometimes, so that might be what you are hearing. To me, it is high pitched, almost like a metal on metal noise, but it is completely normal.

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I'm thinking I'm hearing what you are describing about the 132 mm TB. At idle, I'm sitting between 15 and 17 on the PP vacuum gauge. Not quite sure where vacuum should be at.

stang17 said:

I'm thinking I'm hearing what you are describing about the 132 mm TB. At idle, I'm sitting between 15 and 17 on the PP vacuum gauge. Not quite sure where vacuum should be at.

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I wouldn't trust that, its inferred from what I understand.

I've got a ZT-2 on my car and its showing 21 vacuum at idle.

Can you borrow a vacuum gauge? Might even be time to install a mechanical boost gauge for $85.

stang17 said:

I'm thinking I'm hearing what you are describing about the 132 mm TB. At idle, I'm sitting between 15 and 17 on the PP vacuum gauge. Not quite sure where vacuum should be at.

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Actually the vaccum guage is pretty accurate matches my autometer almost perfect,its just not fast to respond to changes like a mechanical.If your 15 to 16 vaccum u need to look for leaks because that is low for idle in netrual.

Do you guys have any tips on how to go about looking for a vacuum leak?

Look for any loose or vaccum lines that have come off,u can spay carb cleaner on lines and around tb and manifold but be careful if the car is hot.The best way is use a smoke machine,they have some cheap home ones that will work for checking vaccum leaks.

As long as you have the blower seated correctly and nothing has come loose, there is only one real place to have a leak if I remember correctly. That's that line going from the bypass valve under the TB to the manifold.

I also noticed that if the fitting that is under the elbow after the MAF gets pressed on too hard by a coolant line, then it will create a small leak. It really has to be pressed pretty hard though.

I'm curious what everone's idle fuel trims are when the engine is just warmed up vs. very hot after sitting in traffic. My just warmed up LTFT1 is like +5%. After getting very hot sitting in traffic, I have seen as high as +15%. My IAT1 at this point was like 150F from being in traffic for so long, and my idle rpm was trying to stick around 1200rpm. I don't think this is normal, so I'm curious if anyone else has the same problem. I've searched all over for leaks and found nothing. Smoke tested, sprayed propane around, disconnected each vacuum line and plugged them with my finger, etc.

So I came across a questionable fitting on the manifold near the throttle body.

Anyone of you guys have issues with the fittings deteriorating like this?