Jim_Patterson

iTrader: (13)

I think as much as you dyno you should just through a open filter on there one of these times, then we will really see the difference.

Jeff_Jeske

iTrader: (66)

I would like to know if the stock intake pipe is restrictive. I keep hearing how the stock filter and air box are the best because they use a cold air snorkel at a high pressure source but that darn lump rubber intake pipe sure doesn't look high perf.

my03

so is this saying there is no benifit of a map sensor over a air flow meter unless you're flowing heaps?

Ludikraut

iTrader: (17)

Yes ... and that would be HEAPS.

l8r)

David@Vishnu

iTrader: (2)

Yes, don't forget the capital letters!

SaabTuner

How odd. Even with zero restriction, there should have been pressure drop. Now I'm suspicious.

jj_008

iTrader: (8)

For fun, I decided to put a piece of cardboard in my airbox just to see how much vacuum I could create in the intake pipe after the MAF. I cut a piece that was nearly half the area of the air filter. Then went for some runs.

Results: At 20 psi I was roughly 4 inhg and at 30psi I was 9 inhg. I couldn't boost any higher then 30 psi either.

To conclude, if you have half the area of the stock air box on your EVO, then it would benefit you greatly to upgrade to speed density or buy a bigger air box/open filter .

SaabTuner

Interesting ...

Cirrusly Evolvd

iTrader: (44)

I might be a little behind on physics but how would you show a vacuum unless the intake was completely blocked off and all the air was sucked into the engine....therby stalling the engine due to lack of air? A true vacuum would be equal to or less than 0 inches of mercury.
I think the point that I'm trying to make is that there will never be a full vacuum in the intake...there will more air pressure which equals more air flowing or less pressure/air flowing. Find a way to meter how many inches of mercury there are with varying states of blockage.

Precision Dyno

iTrader: (5)

Lets clear up a couple of things here.... the nine MAF does not read "higher" as some have posted.
The difference is that the ecu is able to calculate a higher percentage of load via new variable tables in the mapping protocol.
Now as far as the stock MAF in the EVO is concerned, it does reach a limit. But the hint here is that it does not reach a mechanical limit. Just a sampling limit used by the ecu for load reference...

C6C6CH3vo

iTrader: (9)

The MAF cold pipe is low pressure compared to the volume, any restriction will be undetectable on a 1 psi incremented scale.

Infact, I bet if you took the equivelent airflow that occurrs in the MAF pipe and restrict it's diameter to 50, you will probably not see 1 whole psi differential pressure.

A different method needs to be employed for the test, I have no idear what can be used though.

jj_008

iTrader: (8)

All right guys, the intake pipe, MAF, and air box is a zero pressure system. It is not pressurized.

Think of what's happening. The turbo is sucking air mass at X rate. If the MAF can't give the air mass the turbo requires then a vacuum will occur in the intake tube.

jj_008

iTrader: (8)

For example, think about a straw with a small hole in it. You then put the straw in some water w/ the hole (MAF) outside of the water. If you start lightly sucking on the straw (turbo) no water will come enter your mouth because the hole (MAF) is supplying enough air. Now you start sucking really hard. The hole (MAF) can't supply enough air so water now moves up the straw and into your mouth (vacuum).

nothere

iTrader: (23)

that cardboard idea was a good one. however its still hard to believe that any filter does not restrict air to some extent.

Now, lets say you remove the stock air box cover and tape a scarf across it so only air that goes through the scarf can get into the pipe. If the scarf shows signs of being sucked when you open the throttle, would you say there is a slight vacuum?
Remove the scarf, if you watch the filter, do you think you would see it being sucked deeper into its bed?
that is the only point I am making, somehow your gauge is not seeing the slight pull, however slight, caused by the filter- at the very least.
In fact there has to be an atmospheric depression in the pipe for air to be be drawn through it at all.

jj_008

iTrader: (8)

Lets think about the filter for a minute. The amount of air, the filter has going through the filter, is X amount. If the engine requires Y amount then, the filter amount X better be greater then Y. If its greater then Y, then no vacuum will occur. In order for a filter to flow Y amount it has to have a bigger surface area or use a higher flowing material.

The scarf analogy is an interesting, but the reason a scarf would fold in is due to the air movement of the compressor blades. If the system is open to atmosphere, then no vacuum can occur. The scarf would be sucked in due to is poor stiffness against the air mass. The air that is being pulled into the turbo is hitting a weak structual scarf. If the scarf was infinitely stiff and flowed the same air or more as the filter, then it wouldn't move.