STi2EvoX

I can't seem to get any answers to my questions, so I'll try to rephrase and simplify:

TTP: If a drop in filter increases velocity, then the hotwire maf would be cooled more, and the subsequent increase in voltage required to maintain it's temperature would tell the ecu to actually add fuel and reduce timing, I get that. But, drop in filters seem to lean the A/F ratio in every test I've seen, so what's going on here? Is it in fact not moving load cells? Where is the power gain coming from? I am very curious to learn more about the X's ecu and how the compensation tables work. Thanks again for any insight into this.

TTP Engineering

iTrader: (465)

We have not yet seen this to be the case. We have only tested K&N drop in at this point however as it was what the customer brought in.

spdracerut

iTrader: (2)

Yeah... I've been trying to wrap my head around this one as it makes no sense. This is the best that I can derive: the 'load' value is a combination of the MAF reading, barometric pressure value, air temp, and who knows what else. Point being, it's more than just the MAF reading.

So, the drop-in filters do reduce the flow restriction which increases the barometric pressure (reduced pressure drop) reading relative to the stock filter. I've datalogged this comparing a K&N vs a slightly used stock filter on my VIII.

I'm guessing that the higher barometric pressure readings relative to stock puts the ecu into a lower load cell, which generally has a leaner a/f and less timing past peak torque.

Basically, for a given barometric pressure, the stock filter has less mass flow than a drop-in. So by putting in a drop-in, it's basically throwing off the calibration/tune.

If someone wants to datalog the barometric pressure of the stock filter vs a drop-in on the X, it'd be interesting to see. I did it on my VIII; you guys can search for it if you want.

EVIL_EVO_VIII

iTrader: (5)

when my car was tuned with the zchip we left the STOCK air filter for the first couple of runs. Waited about 15 mins to let the car cool down.We then made another run in the dyno replacing the stock filter with a K&N drop in filter that i purchased and there were NO GAINS what so ever. Pretty much wasted $50. As Scott has tested the stock airbox to its limits, it is good up to 30psi. Its a well constructed design from mitsu. Those of you getting 12-15 whp gains from any intake that DO NOT have a tune, its due to the Ecu running leaner once the filter is replaced due to the pig rich afrs. I myself dont plan on even getting any intakes as the car wont pick up any more power. You guys should spend the couple of hundred dollars on a tune where the timing, afrs can be actually tuned.

TTP isnt trying to bash any intakes or any vendor products, he is in fact helping the Evom community with some hard data and show real world results on their findings

spdracerut

iTrader: (2)

That 'hard data' is that removing the air filter completely from the stock intake system gains 8-10whp. That's it, nothing more.

STi2EvoX

Nobody is disputing that, and we all agree completely. Matter of fact, I've said the exact same thing about intakes for months, long before it was even tested by anyone. I don't know where the miscommunication was, but the question that I have been trying to get answered is this:

EVIL_EVO_VIII

iTrader: (5)

Yes correct but at a level of 30psi, less boost than that and no gains would be made

dcasandman

I think I mostly agree with TTP on this (Which is crazy), and I pretty sure the guys at Cobb Plano felt the same way about it as well. I also agree with AMS about the convoluted stock pipe some too. The stock suction pipe is a mess. Its more ribbed than a ribbed condom, which can not be good for flow. I think replacing it with a good smooth silicone or mandrel bent suction pipe would have to improve flow since it would allow more laminar flow as opposed to turbulent flow caused by the stock suction Pipe. Maybe when we get to crazy Horse Power like AMS is starting to approach with the X now flow will be an issue. Im not sure how much with just boltons and stock turbo the intake will be a limiting factor, and I own an AEM Intake (I took off for the Tune). Even if you make 7-10hp with a tune and an Intake is it worth 300-600 you pay for the intake.

Ivan@AMS

We are talking about two different things now. The MAF housing size difference and the intake tube size / design. There are intakes tubes that use the factory MAF housing and others that replace the MAF housing with a larger one. I am sure that if there were zero gains from an intake tube alone, then said shop would not sell these.

The notion that replacing the MAF housing with a larger one will not give gains and is not proper is kind of far fetched. Mustang owners have been doing it for years. Not only for flow gains but also to increase flow limit of the MAF. 2g MAF in a 1g is a very popular mod for both the above stated reasons. The DSM MAF Translator swapping out a factory sensor for a GM style hot wire, Z32 MAF for a 240sx, the list goes on and on....

You are welcome to test both the effects on MAF housing size and the effects of intake tube size / construction / shape and post up your findings. Till then, you have only showed us that the factory air filter is a restriction with the test you conducted. This same test has been done by every other shop I can think of and is considered common knowledge at this point.

I am not saying that you should "tune" your car solely with the size of the MAF. What I am saying is that with a tune, a car would not be any LESS SAFE with a larger MAF housing and replacement intake tube and would MAKE MORE POWER than one without it.

Ivan@AMS

Trying to state that the stock intake is fine to 30 psi testing it by removing the filter is like trying to say the stock exhaust is good when you see no gains from installing a high flow CAT

If you want to test the intake or the MAF housing, you replace THOSE parts.

Furthermore, stating that people are making gains from removing the stock filter because this "tunes" the car and then later saying that nothing in the tune actually changes when the filter is removed yet it mysteriously picks up power is kind of confusing... dont you think?

STi2EvoX

Ivan, I agree with a lot of what you are saying, but I think the disagreement is whether the intake, larger maf housing or not, makes power AFTER a tune. No one is disputing the fact that an intake makes power on a STOCK tune because it leans out the rich fuel mixture of the stock tune. The problem is that once tuned, the air fuel ratios are properly dialed in and the benefits of the intake seem to disappear.

I think the issue is that on the stock turbo, there isn't enough flow capability to make any better use of an intake than the stock box once the air fuel ratios are dialed in with a tune. I read one test a while back that showed that up until about 400- 450 whp, an evo 8 doesn't make any more power from an intake compared to the stock box with a drop in.

In spite of the improved flow of the larger, smoother pipe of the intake, the difference wasn't enough to really make any difference and it's because of that that it's hard to justify spending a few hundred dollars on something that after a tune, quite frankly doesn't do anything. Now again, I'm sure that once power levels are raised beyond that that an intake IS necessary and DOES yield benefits, but most of us will never go beyond the 450 whp range and in most cases, not even go that high.

Ivan@AMS

The test clearly showed that with the stock filter removed, spool increased dramatically and the ability of the turbo to make more boost with the exact same tune (including boost control) due to less restrictions. HP and TQ were also higher.

I do not think that its a far reach to say that improving the ability of air to flow into the turbo with an intake tube would have the same effects.

I am failing to see where a test was conducted that showed zero gains in spool, the ability for the turbo to make more boost, and HP/ TQ gains by replacing the intake tube or the intake tube and MAF housing.

jsyang15

iTrader: (2)

it seems like on most cars these days, aftermarket intakes lose more power due to unnecessary heat soak...

importjake00

iTrader: (8)

It still does not make sense...

David Buschur

iTrader: (53)

I am not directing my comments here to you, Ivan or Sti2evo, as a matter of fact I didn't even read the responses the two of you have posted. So I am not here to argue with either of you, just so we are clear.

I will give some input. Hopefully it doesn't dirty up this thread.

#1. We sell a MAF pipe. Our MAF pipe does NOT replace the factory MAF housing (I'll get to why in a minute). We do not claim any HP increase with the pipe. There are certain consumers who just have to have a part on their car, many times because other vendors offer them. In some cases parts are built that are more durable, look better or are offered just because customers "have to have it". At the horsepower levels the EVO X's are basically at right now (300-400whp) I do not feel the stock rubber MAF pipe is a restriction what-so-ever. On a budget? Don't buy one. Want the car to have all SS polished pipes on it? Buy one.

#2. We retained the factory MAF housing intentionally. First off all it's large enough with a hot wire MAF sensor to safely support, I'd say, well over 500 whp. The factory ECU is calibrated with the factory diameter MAF housing. Changing the diameter of the MAF housing will absolutely, 100%, no freaking-doubt-about-it, change the MAF scaling and throw the car into load cells that it should not be in. This is extremely important to someone who isn't getting their car re-tuned and also important to someone who is being re-tuned because most tuners do not take the time to rescale the MAF. Cobb has an excellent program in their Subaru software for rescaling the MAF and it is the only real way to actually tune a MAF equipped car. You set the AFR tables to the actual AFR you want the car to run and then you scale the MAF so it knows exactly how much air is coming in and the computer then calculates the fuel needed to hit your target AFR. THAT is the correct way to tune AFR's. Unfortunately that software is not common for the EVO's and the technology hasn't trickled down to the ECUflash software.

#3. Pumping losses. The engine is an airpump, sucks air in, blows air out. Anytime you can descrease the restriction on either end of the engine the engine is going to make more power. That is the simple reason why putting in an air filter with more area or better flowing filtering media the car will gain power, same goes with a less restrictive exhaust.

That's my input. TTP, you are right on the money in this thread.