So I was under the impression that for the most part, anything above 600rwhp is where you started losing the ability to use a maf tune and would have to go SD. But after doing some reading tonight, I've seen some guys w/well over 700rwhp w/a maf tune. How is this the case. The shop that does my work has done a lot of FI tunes and it seems as though they always run real close to maxing out the mafs at just around 575rwhp. I think the highest hp car to date they've tuned is at 630rwhp on a maf tune. But they were telling me i'd have to do a sd tune (which they've never done before) because I'll be well over 700rwhp. Someone please enlighten me on the facts? And while I'm at it, can someone point me in the right direction to have my car tuned. My guys are good, but they don't have much experience if any w/this hp level. I'll gladly travel out of state. Thanks--Andy

 

Andy, MAF or SD tuning can both work fine for cars making over 700rwhp. The key is to have someone who knows EXACTLY what they are doing when tuning FI cars at that power level. Seeing that you're in Oklahoma, you could check with Ed Wright at Fastchip. He'd have no problem tuning it for you either way you want it.

The benefit to SD tuning (IMHO), is that it allows you to run a boost controller and change boost on the fly. The reason you can do that is due to the use of a 2-3 Bar MAP sensor. The MAP sensor can actually read boost and determine the correct amount of fuel that needs to be delivered based on the amount of boost it sees. This of course relies heavily on the quality of the SD tune that's done to the car.

Without having to go into great detail, my suggestion would be this: Set you car up however you plan to race it when you go to have it tuned (i.e. race gas, alchohol injection, open exhaust, etc). Then tell your tuner that you want the car "safely tuned in SD mode" to whatever the max boost is you want your engine to see. Then set that boost level as the highest setting on your boost controller. From there, you will be able to turn the boost down as much as you like and the tune will still keep a near perfect A/F ratio (something you can't do with MAF tuned FI cars).

With a MAF Tune, you pretty much only get one "sweet spot", and that's whatever boost level the car was originally tuned at. If you turn the boost up, you go lean, down and you go rich. The computer doesn't recognize differences in boost changes because the factory MAP sensor can't read past atmosphere. It only knows that you need x amount of fuel everytime you go WOT, and x never changes. Make sense?

Hoep that helps.

 

Thanks Rob, but also keep in mind I'm running an SC setup instead of TT

 

Excellent explanation, thanks. Would that be why my Vortech set up (MAF) would be running a little rough on a day with a lot of mositure and high density atmosphere in So Cal??. A somewhat unusual condition!!

 

Didn't see where you posted anything about what you were running. Even still, the SD tuning would allow you to change pullies without having to get it re-tuned. And if you were to start getting belt slip at some point, at least the car wouldn't go pig rich.

 

Rob, the one neat thing I have found with a MAF is that there can be more than one sweet spot. It happens when you add in a fuel system with a 1:1 boost reference on vac. Your fuel settings will keep the same under any boost pressure. Works good actually.

Rick

 

And on top of that, MAF based cars using Meth injection offer even a broader range as the fueling becomes a constant an the meth is an adder with boost.