IAC Riddle
Thread Starter
Le Mans Master
Joined: Sep 2000
Posts: 6,303
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From: Bartlett IL
IAC Riddle
Just a question. I have a Xfire and recently balanced the TB's. If the IAC count was 9 WITHOUT the air cleaner and it was 0 with the air cleaner, does that mean that the system needed LESS air when the air cleaner is on to maintain the idle at a prescribed level? So the system is getting more air to it with the air cleaner than without. I am using a K&N element. I did run a dyno once and found that I got an 10 additional HP with the air cleaner element on than with it off.
:chevy
:chevy
Safety Car
Joined: May 1999
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From: Atlantis
Cruise-In I Veteran
Re: IAC Riddle (Dominic Sorresso)
Hey Dominic.
You are quite "famous" over on the Crossfire board for your work with the Crossfire Vette's. I am a PROUD CrossFire owner myself.
I'm going to take a stab at this.
I don't think it's a "flow volumn" thing your're observing.
It's more a flow direction phenomenon.
The air is directed into the TB's in a more linear fashion with the aircleaner on.
Some engines won't run worth a toot with aircleaner not installed because the air doesn't flow into them "right" with the aircleaner installed.
THis is usually noticed more on smaller size engines like motorcycle engines and small equipment engines.
If you could do a "smoke test" on the airflow coming into the top of the TBs without the aircleaner on you'd probably see air coming from a LOT of different directions..... left,right,front,back, top, bottom.
Some of this flow will cancel out some of the other flow simply by air molecules colliding with each other from opposite directions.
You'd need a wind tunnel to analyze all the flow patters but obviously the air from BELOW the tb's is blocked with the aircleaner on.
I've seen engine that the flow got so disturbed they would barely run without the filter housing on.
You are quite "famous" over on the Crossfire board for your work with the Crossfire Vette's. I am a PROUD CrossFire owner myself.
I'm going to take a stab at this.
I don't think it's a "flow volumn" thing your're observing.
It's more a flow direction phenomenon.
The air is directed into the TB's in a more linear fashion with the aircleaner on.
Some engines won't run worth a toot with aircleaner not installed because the air doesn't flow into them "right" with the aircleaner installed.
THis is usually noticed more on smaller size engines like motorcycle engines and small equipment engines.
If you could do a "smoke test" on the airflow coming into the top of the TBs without the aircleaner on you'd probably see air coming from a LOT of different directions..... left,right,front,back, top, bottom.
Some of this flow will cancel out some of the other flow simply by air molecules colliding with each other from opposite directions.
You'd need a wind tunnel to analyze all the flow patters but obviously the air from BELOW the tb's is blocked with the aircleaner on.
I've seen engine that the flow got so disturbed they would barely run without the filter housing on.
Thread Starter
Le Mans Master
Joined: Sep 2000
Posts: 6,303
Likes: 714
From: Bartlett IL
Re: IAC Riddle (VetNutJim)
Jim,
I can believe what you're saying because I have experienced it myself. I happened to be doing some dyno runs and said "Let's try without the aircleaner on". I was down on power by 10hp at the REAR WHEELS. WOW!
I guess K&N ain't bs'ing. So it sounds like there is more air getting to the TB's with the Aircleaner on than with it off. I guess that's why they make velocity stacks. The hassle is adjusting the rear TB throttle opening to get the IAC step count right while the cleaner is on. :seeya
I can believe what you're saying because I have experienced it myself. I happened to be doing some dyno runs and said "Let's try without the aircleaner on". I was down on power by 10hp at the REAR WHEELS. WOW!
I guess K&N ain't bs'ing. So it sounds like there is more air getting to the TB's with the Aircleaner on than with it off. I guess that's why they make velocity stacks. The hassle is adjusting the rear TB throttle opening to get the IAC step count right while the cleaner is on. :seeya
Team Owner
Joined: May 2002
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: IAC Riddle (Dominic Sorresso)
That's an intersting point VettNutJim brings up. It does make sense though from a fluid stand point. With the aircleaner on, the air has a very large surface area, where it can enter the system at low velocity, and be funnelled into the TB, versus the blunt entrance w/o the air cleaner, which is a fluids nightmare.
Flow into a blunt entrance can be increase by up to 50% by adding a carefully contoured nozzle to it.
[Modified by CentralCoaster, 12:14 AM 5/16/2003]
Flow into a blunt entrance can be increase by up to 50% by adding a carefully contoured nozzle to it.
[Modified by CentralCoaster, 12:14 AM 5/16/2003]
