LS7 MAF related question....mind as well start!

[Redline Motorsports]

We'll probably not too many of us playing with the LS7 but with hopes of the LS2/LS7 release looming in the near distance it won't be long. I am having a little issue with my new Z with a slight miss/surge at low rpms/loads. The car is bone stock except for a set of LT headers. I only have 1400 miles on the car and I seemed to have noticed this after the headers where installed and some miles got put on the car. At light throttle between 2000 and 3000 rpm the car has a bucking that occurs. As soon as you drop the hammer the car is gone!

I was checking out the intake tract the other day and noticed that the MAF is just a probe that is protrudes into only part of the intake snout. GM must have calibrated the MAF VERY accurately and must know how much air goes through the stock system but how much gets measured.What I mean by that is that ZI don't see how this new design can measure all the air going into the motor. I am wondering if the header install MAY have had some effect on the MAF scaling despite what we normally (with the LS1/LS6) understand. The car is also running VERY rich. All the dyno pulls we have done recorded AFR's between 11.4-11.8:1. I also in the last couple times out popped a 0430 code for something with the CATS efficiency. My scanner was also showing part throttle LTRIMS in the -12 % range.

What do you guys think?? Its not like the car is heavily modifed and has stock programming.

On another note; I found a real cool feature that GM has incorporated into the new LS7 computer. Its called ENGINE DRAG CONTROL ACTIVE. At high speeds and high rpm's when you lift from the throttle, the car displays this on the DIC and the car acts like a jake brake on a truck! It feels like the brakes are getting pulses and the throttle is played with. After some research I found that it is designed so at high speeds, lifting the throttle won't unsettle the rear of the car! Cool stuff, thought I would pass it on!

Howard

[Redline Motorsports]

Anyone have any experience with the new MAF's?????

[caver]

They dont have to measure the whole airflow in fact most of them dont. If its a hot film all they measure is the voltage required to keep the film at a constant temperature. More airflow = higher voltage
Someone then mapped the pcm using that info.
Its exactly like you fitting a standalone system and prgramming it.

We get a lot of cat efficiency errors if we remove the cats because the rear lambda sensors output then looks like front sensors. Might be linked?

[Dirk Diggler]

It sounds like the headers caused the car to run a little rich and this is where you are getting the surging/miss from. All the Z needs is to be dialed in and leaned out and your problems will disappear

[Redline Motorsports]

Yeah I was thinking the same thing but you would think that even through the car is rich that the PCM would still pull the AFR to 14.7. So is it still rich?? I mean the PCM was definately showing through the LTRIMS that it was pulling fuel so yes it is a rich condition BUT the PCM corrected the error and theoretically it should be a 14.7 AFR and hence not rich to surge.

There has been a bit of talk about the new MAF as well as the design of the intake tract on the Z. I will post some pictures later of its design as it may help us look into the future of tuning ahead!

Howard