i was looking at my plenum yesterday contemplating porting it out and i noticed these two holes. as you're looking into the openings where the air enters the plenum, these holes are on the bottom. one on each side. are these factory or something that the previous owner did? if they are there for some functional purpose, will it hurt their function if i port out the openings? thanx

 

Are you talking about the EGR holes?

 

i have no clue what they are. if you're looking into the plenum from the front, you will see these two walls coming up from the floor, one on each side, perpinducular to the plenum. these are the pieces that most people remove when porting the plenum. well, the holes that im wondering about are just behind these "walls". my question is if these are there from the factory or not, and what purpose they serve and if i port the plenum will i hurt the funtion, if any, of these holes. thanx. sorry so long

 

Between the runners on each side of the plennum, there is another tube. The two holes that you are talking about, start from the front of the plennum and travel undernieth to these tubes. So I do believe they are from factory. Hope this helps you out.

350 TPI

 

i think hes talking about the EGR holes too. always wondered what actually happens when you grind down the plenum walls. does this allow more EGR gases to enter the incoming air charge? i think thats what those walls were there for, to limit the amount of air that passed over the holes. now that the walls are gone, the air flows directly over the EGR holes, which would in theory, suck more EGR gas out of the holes. could this cause any drivability problems?

 

Yes, I know the holes your speaking of and they are factory. Look at your base and it will confirm if they're egr or not.

 

Hmm. I was thinking more along the lines of IAC bypassed air.

 

I think the IAC is to far forward for the holes to be for bypassing. I would lean towards the tubes allowing more exhaust gasses up from the EGR.

 

The walls cause a change in pressure at that point, helping the EGR do its job. I removed mine with no driveability problems or tripped codes. I can't say if it made any power difference though because I did several mods at once.