Stft very high

I recently put together a LQ4 to replace the blown up LS1 in my 2002 WS6.

Stock LQ4 block and crank
Scat rods
Wiseco -3.2cc flat top pistons
TSP Bald Eagle NA cam
PRC220cc as cast heads
Stock ls6 intake
stock ls1 tb and maf
1 3/4 headers
stock injectors resized to 42lb by Fuel Injector Connection

I got a mail order tune and the car starts, idles, and runs, however the STFT are very high.

Is this a sign of a vacuum leak? Or is there something else going on? I already verified fuel pressure isn't an issue.

I have a wideband and smoke leak detector being delivered tomorrow, so I will do some more investigating, but wasn't sure if anyone seen this before.

"stock injectors resized to 42lb by Fuel Injector Connection" What does this mean? Decapped injectors? Did they supply full GM data for the "resize"?

Love the "verified FP is not an issue" instead of posting what it actually is and how it was tested.

Quote:

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Originally Posted by 00transamls1

I will do some more investigating, but wasn't sure if anyone seen this before.

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always post your datalog and tune or we cant really tell you anything

Attachment 161401
Attachment 161402


I apologize, the fuel pressure was tested using a fuel pressure tester screwed to the fuel rail. Pressure is constant 58psi.
Fuel Injector Connection supplied the attached Excel file.

Also attached is the current tune.

Might wanna copy over the rest of the injector data.

Most of the time high positive fuel trims are caused by low fuel pressure. If you're confident the pressure is good (should really have a gauge on it the whole time you're tuning) and if your injector data is right the only thing left to do is dial it in.

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Originally Posted by edcmat-l1

Might wanna copy over the rest of the injector data.

Most of the time high positive fuel trims are caused by low fuel pressure. If you're confident the pressure is good (should really have a gauge on it the whole time you're tuning) and if your injector data is right the only thing left to do is dial it in.

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I had the gauge on it the entire time and the fuel pressure was consistent. I can only take Fuel Injector Connection's word on the fuel injector data so I am hoping it's correct for my injectors. The only fuel injector data I see that is not copied over is the short pulse adder. Is there something else that is missing?

Isn't that enough? They supplied complete data and you've chosen to use 2/3 of it.

Quote:

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Originally Posted by edcmat-l1

Isn't that enough? They supplied complete data and you've chosen to use 2/3 of it.

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The tune was done by mailordertuner.com not myself.
I will update the tune though and see if any difference. If i still have an extremely high stft I guess there's a vacuum leak or the injector data isn't correct (injectors don't flow as much as the file states). I can rule out a vacuum leak this weekend. If there is no leak then I may need to spend some more money and get new injectors and not the "resized" stock injectors.

I'm curious about how the "resized" injector and data works. Are they flow testing each resized injector? Are they trying to modify them all to a standard and sending standard data for all of them. The latter would seem to require better quality control than I would think they would have. Both seem like it would be hard to do for $40/injector.

Quote:

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Originally Posted by 00transamls1

The tune was done by mailordertuner.com not myself.
I will update the tune though and see if any difference. If i still have an extremely high stft I guess there's a vacuum leak or the injector data isn't correct (injectors don't flow as much as the file states). I can rule out a vacuum leak this weekend. If there is no leak then I may need to spend some more money and get new injectors and not the "resized" stock injectors.

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Fixing the short pulse adder is not going to fix your problem. But it needs to be corrected. You need to dial it in. It's going to take some tooning.

Quote:

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Originally Posted by gtstorey

I'm curious about how the "resized" injector and data works. Are they flow testing each resized injector? Are they trying to modify them all to a standard and sending standard data for all of them. The latter would seem to require better quality control than I would think they would have. Both seem like it would be hard to do for $40/injector.

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I am not sure. Their site states that they are flow tested, but the file seems generic and not specific to my order. Your guess is as good as mine

"1-4 BUSINESS DAY TURN AROUND
THESE WILL BE GUARANTEED FOR A 3 YEARS!
FLOW MATCHED TO 1%
Price is per injector."

Quote:

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Originally Posted by edcmat-l1

Fixing the short pulse adder is not going to fix your problem. But it needs to be corrected. You need to dial it in. It's going to take some tooning.

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Thanks for the heads up. I was mainly wondering if anyone could tell if there was a vacuum leak that are causing the extremely high STFT's based on the log. I wouldn't think the fueling itself would be that far off, unless the injectors don't match the data provided.

Quote:

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Originally Posted by 00transamls1

The tune was done by mailordertuner.com not myself.
I will update the tune though and see if any difference. If i still have an extremely high stft I guess there's a vacuum leak or the injector data isn't correct (injectors don't flow as much as the file states). I can rule out a vacuum leak this weekend. If there is no leak then I may need to spend some more money and get new injectors and not the "resized" stock injectors.

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So..... Your "tooner" did not even properly use all the injector data he was given. Do you think this makes it more or less likely that he put any thought whatsoever into the file you were given? Just something to think about.

Quote:

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Originally Posted by 00transamls1

Thanks for the heads up. I was mainly wondering if anyone could tell if there was a vacuum leak that are causing the extremely high STFT's based on the log. I wouldn't think the fueling itself would be that far off, unless the injectors don't match the data provided.

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If it was consuming enough air to cause the MAF to be lower than expected it could cause high trims. But a vacuum leak that bad should have other symptoms. Like a high idle.

I'm not sure what a "Bald Eagle" cam is, but the VE is just slightly altered from stock and the MAF is bone stock. It needs to be tuned.

Quote:

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Originally Posted by edcmat-l1

If it was consuming enough air to cause the MAF to be lower than expected it could cause high trims. But a vacuum leak that bad should have other symptoms. Like a high idle.

I'm not sure what a "Bald Eagle" cam is, but the VE is just slightly altered from stock and the MAF is bone stock. It needs to be tuned.

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I am at work so I don't have the cam card in front of me, but it's
227/234 .600"/.600" 111 LSA 109 ICL from Texas Speed.


Once I confirm no vacuum leak and install the wideband I will start modifying the tune.

The VE does not have the right shape for that cam. In other words, it's basically untuned at this point.

It needs VE tuning.

I'd suspect the tune for the fuel trims. The fuel trims being off means the base tune wasn't perfect. It honestly doesn't look like a great starter file. The VE appears to be stock.

Short pulse adder from the injector data needs to be copied in along with the min pw stuff.

There are transient min PW that need to be zeroed out or modified at least in the transient tab.


Having said all that.. the basic diag/check out should always be done. The percentage of cars that come to me for tuning but have other issues is very high.

Seems overlooked alot too, not saying its the case here, but everything, especially related to air, in and exhaust out, needs to be assembled before even attempting to tune it, especially the exhaust or the O2s wont read correctly, and intake ducting should be in its final form before beginning calibrating the MAF curve

^^^ All good points...