Another GM MAFT thread Options

[KOU In3]

Ok, I'll be upfront that I'm just being a bit of a Devil's Advocate here. I like the MAFT and from what I hear, I'll probably end up owning one. I've plowed through most of the DSMtalk threads on it too. But, just to cause trouble I'll ask the following from those of you that have it.

Anyone have any concrete dyno numbers or even track numbers and actual gains from this mod? Before and after improvements?

I know the 3.5 in flows like the Mississipi in and of itself but when you neck down to the throttle body is all that flow lost and even disturbed by all the steps to get it to mate up? The 2G MAS looks to be pretty close to a 3" MAS flowing more or less straight through.

Although tuneable, can it match the increments of the SAFC in terms of fine tuning?

Granted, everyone who's bought one seems to love it. I'm just wondering if anyone's truly dialed it in on the Dyno and done a side by side with the 'old' SAFC 2G mas combo.

OK, flame suit is on. Time to endure the punishment of the translators.

[natedogg]

The MAFT definitely can't match the fine tuning of the SAFC (1% increments on SAFC vs. 5% increments on MAFT), but at the same time it seems to be less finicky than the SAFC. When I had the SAFC on my FWD I was always f-ing with it to get my car to run just the way I wanted it to. With the MAFT, it took a few tuning sessions with the logger and I was done. (Well, I'm never really done with this damn car, but you know what I mean.) Plus, if you really don't want to let go of the SAFC you can use it in conjunction with the MAFT. Just set the MAFT's base setting for your injectors, leave the rest of the MAFT dials at 0 and do all your tuning with the SAFC.

I personally don't have any dyno numbers, but I think AMS is supposed to be dyno proving one sooner or later. I hear they've been pretty busy developing mods for the EVO though.

I've never seen any concrete flow numbers on the 2G MAS, but I know the 3" GM MAS flows up to 800 CFM and the 3.5" flows up to 1000 cfm. I kinda doubt the 2G MAS can match those numbers.

The main reasoning behind removing as many intake restrictions as possible on the intake side of the turbo is the simple fact that turbos are designed to blow, not suck. The less turbo intake restrictions, the less the turbo has to work to spool up and hit max boost, hence quicker spool up and more power.

I think one more plus is the simplicity. Installing the GM MAFT in draw-through form is truly a 15 minute job and tuning it to perfection doesn't take much longer. Perhaps a couple of hours on a country road...or in front of my asshole neigbors' houses.

[KOU In3]

Granted the flow numbers are much higher for the MAS itself, but will it flow as much when necked down to the size of the piping it is attached to (especially in the case of the 3.5")?

This is where I follow with the really dumb question: If using it in draw through form, isn't the turbo still 'sucking' through the resistance of the MAS? I've tried studying the set-ups but I'm a bit of an idiot so...

Holy cow though I have to pay omage to the 15min install though! Very nice product there.

Finally: As much as I love DSM's I do kind of miss the way the muscle car mags are constantly dyno flogging motors to get concrete numbers and direct product comparisons. Seems like it takes months before someone runs one on our cars and it's rarely even redone/ rechecked by other companies. Look at the hp numbers for Webcams that used to be on RRE's site for instance. Never saw it verified, tested or compared elsewhere yet.

Anyways, enough of my newbie ranting.

[natedogg]

Well, all I can tell you is my butt tells me it makes my car faster.

In draw-through the turbo is sucking through the resistance of the MAS, but its pretty clear to see that the GM MAS's, with their higher flow rates and aerodynamic design, offer less restriction than either of the stock DSM MAS's.

As far as flow goes on the car, we basically measure that by the turbo. For instance a small 16g flows 505 cfm at 15 psi. It flows more than this at a higher boost pressure. Obviously the 3" GM MAS can easily handle this much flow without overrunning. We can run a turbo that flows up to 800 cfm without overrunning the 3" MAS. After that, its probably best to get a 3.5" MAS.

[AWD DSM 1]

Travis has a good question, why put a huge MAS on if you can't flow enough through the TB to make use of it all? Enlarging all the piping from the turbo to the cylnder head would help the MAS perform to it's full potential, right? I guess it becomes an instance of the weakest link... Whatever flows least will be your limiting factor for intake airflow... I wonder if we will see people starting to put on 3.5" exhausts now. I'm sure that any car using the GM MAS would also benifit from larger intercooler piping, TB, intake manifold, intercooler, head porting, turbo porting.... anything to flow more air once the stock MAS is out of the equation. I guess it all comes down to how limited your resources are....

[natedogg]

I think flow before the turbo and after the turbo are two different monsters. Flow before it isn't pressurized, its being sucked in like a N/A car. After the turbo the air is pressurized so you can flow more because you are forcing it into the engine rather than sucking it into the engine like a N/A car. The turbo is the deciding factor on how much flow your car sees. It doesn't care what the piping after it looks like, because its going to force the air in there anyway. Don't get me wrong, bigger IC piping is better for higher flowing turbos because the turbo doesn't have to work as hard to push the air, but it still will push the air. I'm sure there comes a point where upgraded IC piping is required (eg. Running a monster L3R on stock IC piping) just for the turbo to spool up. But you could have a small 16g running on stock IC piping still flowing 505 cfm at 15 psi whether the piping behind it is stock or upgraded. If our cars were N/A, then I'm sure the (now unnecessary) IC piping would flow maybe 250-300 cfm (guessing), but hell the stock 14b flows more than this at the stock boost pressure.

Anyway the point is flowing more is the whole point of a turbocharger. If the piping behind the turbo was going to limit the amount that it could flow to what the piping itself would flow naturally, then turbos would be useless.

[AWD DSM 1]

Makes sense. Basically, since it's being pressurized, you can multiply the actual amount of air being moved through the piping. The bigger piping would just make it move easier and reduce the "backpressure' on the compressor of the turbo, right? Big pipe doesn't necessarily = more flow in a pressurized system?

(you'll have to excuse me, it's been 6yrs since I had a physics class)

[natedogg]

Makes sense. Basically, since it's being pressurized, you can multiply the actual amount of air being moved through the piping. The bigger piping would just make it move easier and reduce the "backpressure' on the compressor of the turbo, right? Big pipe doesn't necessarily = more flow in a pressurized system?

(you'll have to excuse me, it's been 6yrs since I had a physics class)

No problem man. I had to stop and think about it too.

Anymore brainbusters, Travis? j/k

[KOU In3]

[QUOTE=

Anymore brainbusters, Travis? j/k

Actually, yes. Here it is:

Using a dumped 02 housing. Initial boost onset should be the same since all the exhaust routes through the downpipe. But, once boost hits and the wastegate opens, then excess exhaust is vented driectly to the atmoshpere, bypassing the downpipe. This effectively makes your exhaust system function as if it has a bigger diameter piping as the full amount of exhaust does not have to travel through the system.

Now, given that adequate diameter piping (e.g 3" or even 3.5") is used, what is the benefit of a dumped 02 housing? No spool-up benefit. Possibly boost creep elimination. But does it free up any real power? Hoping for reference to dyno numbers again (note my current obsession there). If it does net a real increase doesn't this indicate instead that the exhaust tubing diameter is insufficeint to flow the exhaust gasses produced under boost and the dumped 02 serves as a band-aid for the problem?

Here's your 'brain-buster' Nate. Help a struggling nOOb out.

[akamiami]

I've actually had the chance to run both types of 02 eliminator pipes. Other than noise you won't find much of a difference. Diverting the exhaust back into the pipe should disrupt the flow, but at this point the exhaust is probably still getting most of its velocity from the properties of thermal expansion.

[awd4kicks]

Currently I have to disagree, but there is no hard evidence.

There are a number of people on DSMtalk that claim a 10th or two in the quarter simply by adding the dump tube. A tenth or two is a lot in the quarter, but may not be nearly as noticeable on the butt-O-meter.

The only crude logic I can come up with to make sense of this is backpressure and combustion charges not being in sink. What I mean is, when an internally plumbed waste gate opens it re-routes a portion of the exhaust gasses around the turbo and then back into the exhaust stream in a different location. This may get a bit complex, but the gasses coming out of the pre-turbo exhaust stream released some 'pressure/flow' between the engine and the turbo - hence cutting back on the turbo's driven output. This batch of gasses has force, displacement and it has not expanded as it travels through the wastegate tubing. Once it reaches the exhaust piping 'post turbo' this pressurized gas is interjected into another part of an already flowing exhaust stream. Besides adding volume, and force on the wrong side of the turbo, both of these are multiplied as the waste gate gasses expand in the large exhaust piping, thus raising the average pressure on the back side of the turbo. With that said I understand that we're are not talking about forces that will break off turbine blades or slow the turbo down. The key is efficiency, and if your adding pressures on the wrong side of the turbo the efficiency could be better.

So when you have an external dump pipe the exhaust gasses flow un-interupted through the turbo and exhaust piping while the re-routed waste gate gasses have the open atmosphere to expand into (almost like a vacuum compared to the exhaust piping), releasing the force and volume that drive the turbo that much quicker.

The only proof I have of this is that the external dump O2 housing is the only major change that I had on my car when I ran the 12.67. I hope I have this wrong, because I'd like to go back to a more stealthy exhaust. I just don't see how right now.

BTW - This same efficiency theme should hold true for the intake piping as well. It's not a matter of whether the turbo can make the pressure, it's how much air in volume can you make that engine pump through. The difference between pressurizing a 2" diameter pipe to 15psi and a 2.5" pipe to 15psi is a substantial volume increase. That is where your performance gains come from.

[natedogg]

Travis, if you plan on driving your car on the street I suggest you get the wastegate dump plumbed back into the exhaust. The external dump is just too damn loud. Its already got me into trouble with the man a couple of times.

Other than that, I like Marcus's theory, but at the same time there is definitely something to be said for Kris having tried both, but I believe his only reference is the butt-o-meter as well. Obviously there are pros (less possible boost creep) and cons (damn loud) to the external dump. The choice is yours.