Should i use the MAF in my twin turbo 383?

[redmonaro]

Hi, iam new to the tuning game, Ive got a twin turbo 383 ls1 in my monaro, fitted with a small isky cam, stock 241 heads with 918 springs, 6 speed manuel, it has been tuned in speed density, Iam concidereing refitting the MAF, and was wondering what the benifits are? i was also looking at the dynamic table in VCM suite and was wondering if its possible to disable the MAF after 2000rpm so when iam cruising around on light throttle it has good drivabilty and fuel economy then after 2000 rpm it switches to speed density for when its starts to boost? iam hoping to run up to 15 pounds of boost when its tuned

[edcmat-l1]

Why can't you have good driveability and economy running speed density?

[redmonaro]

it runs ok, just seem there some more benifits when using a maf, iam more interested in the maf for low speed drivability and highway cruising, i temporarly refitted it and drivability seems much better at low speed and highway crusing

[SSUte01]

You can't have MAF at lower rpm and switch to SD at higher rpm and then have it switch back as far as I am aware. Depending on the specs of the cam, you will actually get better low speed drivability with SD on LS1 PCMs. If you get better results with the MAF then your SD airflow model (ie VE) and/or bias (resulting in airmass) is not as accurate as it could be.

Definitely had much better results on all cammed LS1s utilising SD, that's not to say that you cannot get good results utilising the GM model of blended MAF and SD or even MAF only, it's just that the slower 0411 PCM gets superior results SD in my experience. Furthermore, being a 75mm MAF (unless you fitted a 85mm MAF) youre introducing a restriction into the intake setup albeit this is less of an issue when boost is involved.

Finally, as stated above the only reason you'd get better economy or drivability with the blended MAF means the VE and/or bias needs addressing. At the end of the day it's your choice, but personally I prefer SD on any 75mm MAF LS1. That's without even starting on the argument of sticking with the MAF with boost on that setup that will quickly be out of range on your setup. Unfortunately, I don't believe you can achieve what you have requested, the other way, sure, but not what you're after. Go (or stay with) 2 Bar SD IMO. Good luck.

[redmonaro]

thanks for the great info ssute, where are you based?
I have the vz 85mm maf

[SSUte01]

No probs, just offering what I have found. The VZ MAF certainly offers less of (very little) restriction on a LS6 manifold.

I live near Newy, so not far from you. Sounds like an interesting and very cool setup.

[redmonaro]

are you a local tuner? And who do you work for?

[redmonaro]

ssute if you look at the dynamic table there is a disable function for maf after a certain rpm, the rpm is changable,

[SSUte01]

If you are referring to Engine ==> Airflow ==> Dynamic ==> High RPM Disable then that is referring to disabling dynamic airflow calculations i.e. SD. So, once the RPM exceeds this value the PCM will use MAF exclusively for airmass calculations (albeit filtered)

This means you can you can run blended MAF/SD below this value and then exclusive MAF above it but not the other way around like you are hoping for. If we are talking about the same table it is effectively a SD disable table not a MAF disable table.

You can run blended MAF/SD and then have the MAF fail so you run pure SD, but the MAF won't "unfail" in my experience without a cycle of the ignition as once a MAF DTC is set it won't "unset".

Yes I do local tuning. You clearly have your own HPT setup, so if you ever want any help let me know, I have helped people in the past face-to-face who have their own HPT setup and get them going. Karian Autos is a family business based in Vic with a small shop and recently upgraded dyno, however I live up here these days so I don not have a shop up here.

PM me if you ever have any questions and I can give you my number if you would like it.

What fuel system, static compression ratio, injectors, and cam specs are you running if you don't mind?

Cheers
Luke

[redmonaro]

I went back into the dynamic table luke, and yes i got it the wrong away around with the MAF disable function.... thought i was on a winner for a moment, i dont have the HP tuning yet Luke, I've been using the demo version but going to purchase vcm suite in the next few weeks..... my engine is a 383 forged internals, 9:5:1 compression, stock 241 heads with 918 springs, LS6 manifold with stock 75mm throttle body, 28/71 turbos, best to date is 590hp at the rears, cam is 221/221 118'ls 575/575, at the moment i dont think the cam is suitable for for application thinking about changing it, along with throttle body and want to put better heads on it.... Tune isnt finished yet... and can only get 12 psi at the moment eboost needs setting up on the dyno

[SSUte01]

I can certainly see some advantages if it were the other way around. When you get your setup and if you would like any help figuring it out, please let me know. It can save a lot of time if someone points out some fundamentals early on as opposed to learning everything the hard way and some "anti-learning" that is out there. I sometimes wished there was someone to ask early on.

I've replied to your PM with my number.

Regarding the car, it sounds like quite a weapon with all the fruit and would like to check it out sometime.