Any idea at what HP/boost on the stock turbo, the stock 2.5" Mass Air Flow Sensor is restrictive?? I've been just wanting to do a K&N drop in and maybe the Cobb rubber intake tube... but I don't want my 2.5" MAF to be the bottle neck. Anyone know?

 

The stock MAF at max voltage (5v) will report 41360, which is essentially 379g/s, which works out to be 50.01lb/min. The stock turbo is speced at 42lb/min. Basically, with the stock turbo (or any turbo rated under 50lb/min), you're fine with the factory MAF/housing regardless of other bolt-ons. With bigger turbos, it depends how close you are to maxing them out.

The basic formula for figuring how much MAF scaling you'll need:

x = lbs/min of target turbo
MAF reading at 5v (max) = x / 60 * 453.59237 / 600 * 65536

From there, given a baseline of 2.5" reading 41360, 'estimate' your required diamete using a % increase. This should also give you a bigger number than you need, from my experience. Round to nearest available tubing size and call it a day

IE:62lb/min turbo gives a 5v reading of 51195.

% change: ((51195 - 41360) / 41360) + 1 = 1.237811

new pipe area: pi * (2.5/2)^2 * 1.237811 = 4.8608
* note, this isn't perfectly accurate since area and MAF volts don't scale linearly, but usually 'over estimates', which is fine

you can figure out the diameter from here
also, i've not had any coffee this morning, so double check all that before you take it as gospel =/

 

Yea I would ask the question at what flow level does the MAF max, not horsepower, as horsepower has more conditions other then just flow that dictate the power level, example being octane, etc.

That said. A 3" MAF housing has maxed on our Mustang Dyno, with a PT6262 at a little under 25psi, on 91 octane pump gas, at a little over 450whp. Simply adding E85 and keeping boost the same, you will expect to see much more horsepower, but the same airflow.

- Bryan

 

Wait a minute...So your saying folks with a FP green/Red could be maxing their MAF's? This is the first I heard of this..

 

I've logged VERY close to 5v with BBX's with even a 3" AEM Maf tube.

I'll have to check my logs to be 100% accurate, but my RA with the BBX lite, currently at 24.5 psi flat to 7800 rpm, logged 48 lb/min and MAF logged around 4.7Xv or so, on a AEM Maf housing

- Bryan

 

I'm ordering my green soon, so as long as MAF volts is below 5v, all should be good right?

 

This is why I got a 3.5" intake for my Black

Our local maxed his BBX out on the AMS 3" intake, he was hitting 5v. I would think a maxed red could do the same...the black I am sure will.

This is a known deal with hotwire MAF's...a lot of evo tuners don't know to look for it unless they do other cars like Subaru's or mustangs or something that have hotwire MAF's too.

So I am sure there are a few others that are hitting 5v or higher and just don't know..you can tune around the MAF by just adding tons of fuel at that point, very bad idea though.

 

When you say 3.5" intake, you mean the intake pipe, not the actual hot wire sensor right?

I did buy the cobb FP intake pipe with 3.5" bulge, so I hope I bought the right peice by shear luck I don't even know if a green could max the MAF anyway, though it is a 54lb/min turbo.

 

He is talking about the size of the MAF housing. You have to be careful when you start increasing size however, things like turbulence, resolution, etc start changing.

- Bryan

 

Understood, have you seen any issues with the Cobb FP tube with 3.5" bulge?

 

You have to setup your MAF scaling for the specific intake. The housing around the MAF is what I am talking about. If you increase that, the sensor is not seeing as much air so it doesn't max out as quickly. Brian is right though, you will lose resolution doing this but it's either that or a blow by setup which I don't like.

But the first thing you need to do on a tune, or one of the first is scale the MAF correctly...along with injector scaling too.

 

I understand scaling, but am unsure if it's needed with this Cobb intake. It looks like it connects to the stock MAF housing.

So if that's the case, it shouldn't need to be rescaled. I'm putting the buggy before the horse sort of speak as this is just a paper excercise until I order my FP Green at the end of the month.

 

If it uses the stock maf housing then it doesn't matter.

- Bryan

 

Thanks Bryan, thats exactly what I thought.

I just have to wait and see if my green can push it to 5v.

Screw dyno plots.....let me see you MAF plot...LOL

 

I've asked some shops to post that so I can see because I don't believe where their numbers are and they have never given me one because I usually have a pretty good idea if their dyno reads whack. I don't buy into the whole dynojets all read exactly the same blah blah blah. I have seen all dyno's that read all kinds of things. Only one dyno to the same dyno is worth comparing.