Running out of MAF

[3Dee]

Trying to sort out my violent hesitation at around 3k revs the last few weeks with Paul Spinks who knows his stuff with HP Tuners gear.
After many attempts and maps we still are having problems although the stuttering point moves around a bit as we tinker with the settings.

He tells me yesterday that he has maxed out the MAF setting limit, yet it appears still not enough fuel is being delivered at certain point which results in this stuttering. Rather than just keep tweaking, I wonder if I should look into the MAF more closely.

Have checked all usual suspects, earthing, fuel pressure at rail (consistent 63psi), injectors consistent etc, but I did wonder if I have either an air leak post MAF, or a DIRTY MAF sensor, or a duff unit?


Presumably the air leak possibility can be checked easily,but not so sure how to diagnose the MAF sensor itself??
The easiest way of eliminating this would have been to beg/ borrow one to see what if anything is the difference.

I don't suppose anyone has one knocking around?

I could always nick one off an Ultima visitors LS7 for 1/2 hr?

[Paul.B]

A couple of things that may help?

1 - I remember reading on the US forums that the MAF should be further from the TB. Do a quick Google and see what is said in the forums. Maybe a make shift extension tube to move it away is worth a try?

2 - I had to do an awful lot of careful fettling to get the inlet manifold to sit down square after rotating it. You may well have an air leak.

[deadscoob]

Have you spoken to the supplier re all the mapping issues you've had?

Can your mapper not run some diags? If the maf had any problems, it would come up during diags?

[chuntington101]

If you really are out of MAF, why not go Speed Density?

[3Dee]

I think the plan of action is to check and make sure the breathers are all capped properly, and I do know that a while back I had to remove one or two (not adjacent to each other) of the intake manifold bolts to change a bracket so I will check that they are torqued properly (44 the 89 inch lbs I think). Then if no change, I might even reposition the MAF unit as it is rather close to the TB. I understand from some that this can cause some feedback problems, so moving it might be good anyway.

Then if no different, I need to find a way of checking the MAF itself, but I have no idea how?

[Storer]

Here is a pic of mine after a second rolling road session. How does the position of your MAF sensor compare?



There are also quite a few pipes into the manifold that are tucked away where they are not easy to see so pop a camera phone under the throttle body and check they are all sealed.

Hope this helps

Paul

[3Dee]

Storer said:

Here is a pic of mine after a second rolling road session. How does the position of your MAF sensor compare?



There are also quite a few pipes into the manifold that are tucked away where they are not easy to see so pop a camera phone under the throttle body and check they are all sealed.

Hope this helps

Paul

Yep Paul, The engine was delivered with the MAF only a few inches away from the TB - and you picture confirmed what I had decided to do - the MAF this weekend will be repositioned at the other end of the U Tube!

[deadscoob]

I think the install instructions say it has to be a minimum distance from the tb, certainly way more than a few inches. My setup is the same as Storers and no issues.

[Graham-P]

For my LS3 setup the MAF guidelines are,

The induction system should be 4 inches in diameter and have a minimum straight section 6 inches in length. Mount the MAF sensor in the middle of the straight induction section, ensuring that the middle of the mounting boss is at least 10 inches from the TB.

This is why I have my air filter almost sticking out of the back of the car . No problems so far.

Graham