IAC hissing

[delcowizzid]

You have to watch out with it in the wheel well it's generally a negative pressure area and will have some suction effect on the pod .I learnt this with my vp years ago when I cut a hole under the airbox I ended up running 4" cold air pipe to the front bumper .the factory maf pipes are keyed to the maf and airbox so the maf can only fit in one orientation to the airbox lid and throttle

 

[nes138]

You have to watch out with it in the wheel well it's generally a negative pressure area and will have some suction effect on the pod .I learnt this with my vp years ago when I cut a hole under the airbox I ended up running 4" cold air pipe to the front bumper .the factory maf pipes are keyed to the maf and airbox so the maf can only fit in one orientation to the airbox lid and throttle

And the pipe gets longer.... You mean the direction (as per the flow arrows) or it has to be up a certain way aswell?

 

[Deuce]

I was reading info from an aussie air filter maker yesterday and they say 1.5xdisplacement should be the volume between filter and t/body.

It annoys me, because for a 5.8ltr this means 1.9metre of 3" piping between the two

 

[nes138]

I was reading info from an aussie air filter maker yesterday and they say 1.5xdisplacement should be the volume between filter and t/body.

It annoys me, because for a 5.8ltr this means 1.9metre of 3" piping between the two

Wouldn't it be 1.5x the diameter of the TB and = 4.5" long?? That'd make a lot more sense or you'd need one of those 4wd pipe running up the A pillar


Although you may be right. Found this on another forum.

Here is what the GM crate engine control system instructions have to say about it:

"Ensure the MAF sensor is oriented correctly in the induction (it will
only read correctly in the proper direction). An arrow is located on the
sensor indicating correct flow direction. Verify this before welding the
mounting boss, as the sensor will mount only one way in the boss.

Ensure the MAF Sensor is mounted in the middle of a minimum 6 inch
length of 4 inch diameter tube, and is a minimum of 10 inches from
the throttle body."

 

[EYY]

Yeah they REALLY don't like being in the wrong spot or orientation. When I first did the sequential injection conversion to my 304 I couldn't figure out what was wrong.

I had the maf rotated 90 degrees from the factory position and there was an elbow in the intake immediately before the MAF on the airbox side. Fixed those problems and it was a different car. It idled well, had good fuel economy and actually had power. Couldn't believe the difference it made. The MAF calibration in the tune relies on the factory MAF position. If you change MAF position - it'd really need to be retuned to compensate for that.

Basically, the sensor or 'hot wire' is in the centre of the maf and relies on airflow being consistent through the entire CSA of the MAF. If there's more air flowing though one section of the maf than another, that's where you have problems because the pcm doesn't know that there's extra air entering the inlet because it relies largely on MAF data for fulling calculation. Thing with MAF based systems is that they measure the ACTUAL air that enters the engine, and it's not just a calculation of air intake like a MAP based system.

 

[nes138]

Thanks EYY.

Closest I can come up with is this. BUT I am using a spare MAF as a joiner in the middle and the air con compressor is right below it and lines need to go to the fire wall.
Makes that cruise control wire awkward too.
https://photos.app.goo.gl/mJyGrhFEdbN2iPRr5

Or maybe even mounted a spare backing to an Apollo filter to put through the wall.
https://photos.app.goo.gl/Vvx2FhW1uMyXyfce7

I can’t find anyone supplying 80mm ID pipe either. It’s all 76mm and is too tight.

 

[nes138]

Or go all the way down under the front bar??
https://photos.app.goo.gl/QMjaAwgaUzGDTdHS8

 

[EYY]

I'd be going under the bar. Keeps the engine bay looking tidy too and plenty of room for some straight pipe to put your maf in.

 

[nes138]

I'd be going under the bar. Keeps the engine bay looking tidy too and plenty of room for some straight pipe to put your maf in.

Yeah I think I’ll go with that. Even lengthening it slightly didn’t really change it and this is warmed up.
https://photos.app.goo.gl/yR76HYbyoYadaCHJ9

 

[EYY]

You won't get rid of the hissing unless you put a proper airbox back on it. what you've done there won't work well at all. better off having it coming straight out of the throttle with a bit of pipe and fitting a shallower pod if you want to keep it like you had it originally. The 'black box' section of the maf needs to be down towards the ground.