Stock 5.3 with Headers the VE table had to be change by 20+% ???

Hey Guys, I could really use some guidance I AM NEW. I?ve got a stock 5.3L swapped into my G35 with just long tube headers for mods. I was working on tuning the MAF, but every time I made adjustments?like adding 10%?it didn?t seem to have any effect, and the car had trouble accelerating.

I thought the MAF might be bad, so I disabled it to start tuning the VE table instead. That actually fixed the drivability issues, but I had to add over 20% fuel in some areas, and now some cells in the VE table are reading over 100%, which doesn?t feel right for a mostly stock setup.

The engine has new plugs and wires also has 58 psi at the rails, so I?m starting to think something else might be wrong, and I?m just making it better by adjusting the VE table but not fixing the real problem. Does that sound right? I'd really appreciate any help figuring out what?s going on.

File is stock besides MAF and VE tables, Ill post the tune and log when I get Home.

This is usually because of fuel pressure issues. Make sure it has fuel pressure under heavy load/ high RPM

I'm certain the system maintains a constant 58 PSI at the pump and holds steady at 58 PSI at the fuel rails while idling. Today, I’ll check the pressure at the rails under load to confirm 58 psi under driving conditions.

I was also told that the IAT sensor placement could be a problem because I have it right on the throttle body because its built into the MAF and If I am getting high IAT readings "Im not sure what a high temp would be 150+?" that can cause the VE model to be artificially higher from the ECM thinking the air density is less than it actually is. So ill be checking that today as well.

The only other thing I have seen is with the key on, engine off check the MAP sensor reading and make sure it reflect my baro pressure to verify that the MAP sensor is calibrated and works correctly. Ill be doing that today as well.

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Originally Posted by popmods

got a stock 5.3L swapped into my G35 .

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so you 5.3 has every intake piece, exactly how GM had it in the truck it came from the factory with?
you only have headers? Every other piece of the exhaust is exactly how GM built it from the factory?

--i bet you have some type of aluminum intake tube, headers, no cats, free flowing exhaust, performance muffler..

all those things change the air going in and out of the engine.

For me, i first tune BRAF, then VE, add timing, retune VE, add more timing, retune VE, then tune MAF, then hook up Wideband O2 and do WOT runs to tune upper VE/PE, then work on idle and cruise.

im telling you this, as you said you are new. So im giving advice.

BRAF first, then VE.

Post up your tune and log files and we can help.

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Full exhaust no cats with long tube headers the intake is exactly how GM had it in the truck, I don't have a aluminum intake tube because i don't have a tube at all the MAF is mounted right to the intake with a coupler.

Putting the MAF right in front of the throttle body with a coupler is the worst place you can put it. You would be better off not using a MAF and tuning it in SD if that is the only place to locate it.

Well that would make since why it did better in SD but why do you think I have to add so much to the VE table?

Alvin mentioned likely why..

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Originally Posted by popmods

Well that would make since why it did better in SD but why do you think I have to add so much to the VE table?

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Without seeing a tune and log no one can see what you are doing right or wrong.

I?ll post it soon as I get home thanks.

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Originally Posted by popmods

the intake is exactly how GM had it in the truck,.

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but, its not.

Here is the Files

well, put it back to the stock tune.

youre adjusting too many things at once.
your pe is flat
you have little timing
and your BRAF is too low

put it back to stock, fail the MAF and tune the VE first.

I haven't touched anything but the VE table so really its a stock file besides the MAF is failed out and VE table has been changed. I will Put it back to stock and start over.

st+lt trims show youre not too far off on your log

Attachment 161688

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Originally Posted by popmods

II will Put it back to stock and start over.

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post up your stock tune so we can compare it.

Look how much I had to change the VE table

Start with this file. Your stoich was flatlined but flex fuel enabled? What injectors and fuel pressure regulator? Double check injector data.

Quote:

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Originally Posted by popmods

I'm certain the system maintains a constant 58 PSI at the pump and holds steady at 58 PSI at the fuel rails while idling. Today, I’ll check the pressure at the rails under load to confirm 58 psi under driving conditions.

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That's the typical response right up until the person puts a gauge on the vehicle and realizes it doesn't.

Attachment 161702

You've got Flex fuel injector data. I'd bet they aren't flex fuel injectors and this is going to be your root cause.