DarinS4Turbo

After hearing about Mike and Doc seeing more airflow with stock filter vs. ITG cone (incidentally, with their cone's intake tube still in the airbox with stock filter), I decided to give it a try. I also left my S-flo tube inside the airbox with the stock filter. I also tested a gargantuan K&N cone filter which is the same that Mark P has tested. Stg1 with AMS chip, temps in the 70's, all filters new.

ITG/S-flo tube - peaked in mid 260's g/sec
K&N/S-flo tube - peaked in mid 260's g/sec
stock filter/S-flo tube - peaked at 280 g/sec

Note that the stock filter had a more choppy MAF curve (values bounced around) than the cone filters, which were smoother (albeit lower). I didn't get a chance to do very controlled FATS time runs, but the times were all very close to the 5-sec flat range, so I can't conclusively say the stock filter was faster yet.

The big question is whether having the intake tube with the stock filter is changing the airflow reading (whether it be a 'real' airflow gain, or artificially manipulating the reading). I might have to do some more testing.

I also have another old dirty ITG filter which I'm going to tear off the foam filter and use the velocity stack base mated up to the S-flo tube inside the airbox (with stock filter). I'm wondering if the velocity stack might help airflow a bit more.

Oh, I also tested my Bosch MAF (which is already screenless), with and without the plastic airflow straightener as well. These tests were with the S-flo tube and stock filter. Without the airflow straightener, the MAF readings *really* bounced around and actually read lower than with the plastic straightener. Interesting.

PSmalls::DoggieStyle

For whatever reason, possibly the choppyness, our FATS times were not significantly faster even though we had a max MAF reading of 20+ g/s higher. Exact same results as you, Darin!

DarinS4Turbo

would make things less choppy, not more. I wonder if having a venturi/velocity stack will help, I'll test that out. Maybe having just the straight edge tube in open space causes the air to enter fairly turbulent (whereas with the cone attached, it has already evened out or straightened the airflow when it enters the tube).

PSmalls::DoggieStyle

Yeah, we'll have to test some stuff. It sounds like Mike has some new intake ideas up his sleeve.

JBear::FATS

Out of curiousity, is that 91 octane on the FATS runs ? Thanks.

DarinS4Turbo

Somewhere around 95 actually

VerrÜckt

You would definitely feel that much difference in the seat of your pants...20 g/s *should* be approximately a 25 hp gain. I'm sure you're just altering the cross sectional flow pattern and the MAF is reading it differently.

I would log fuel trims and see if the MAF "sees" that extra air, adjusts injector duty cycle accordingly, and then catches itself at the O2's as it runs a little rich.

Good stuff Darin. <thumbs up>

Schnell!

Did anything ever come of UrS4's testing of an airbox velocity stack?

QCRAZY

...that the air is pretty turbulent at the MAF sensor.

When you remove the laminar screen the turbulent air doesn't pass directly through the MAF (i.e. it's velocity is not in one direction).

With the laminar screen the air is smoothed out to mmke it better (less choppy) but it still might not be enough to get rid of enough turbulance. With the turbulence there you run the risk of counting the same air twice.

Verrückt, has the right idea. Check what happens to LTFT with the filters. I'd imagine you will see more negative numbers with the stock filter.

NogaroMariner

but it will be interesting to see what happens with the velocity stack and s-flow tube. I think you could make a cheap velocity stack from a speaker port available at any car stereo shop.