cliffyk

OK, first of all open this page, read the intro, and then look at the numbers for the OEM upper plenum.

You will see that the OEM upper plenum is the weak link in the stock intake, even with a 70 or 75 mm TB the best it can muster is 491 cfm at 2 inHg.

Next, look at the flow rates for the aftermarket plenums with the stock 65 mm TB. Every one of them (except the C&L which seems to be a bit if a dud), with the OEM 65 mm TB, will outflow the OEM plenum with a 75 mm TB.

Slap a 70 mm TB on any aftermarket plenum (except the C&L) and you're moving 100+ cfm more than the OEM plenum with a 75 mm TB.

Also note that there is only a slight advantage to the 75 mm TB over the 70 mm TB, and that in the case of the Accufab and TrickFlow plenums the 70 mm TB performed as well or better than the 75 mm.

All aftermarket upper plenums are 5/8" to 3/4" taller than the OEM plenum, which permits a more optimal area/sweep/shape to the unavoidable 90° elbow. The OEM plenum is too short to have this optimally shaped elbow and no amount of "porting" can change this--there just isn't enough "meat" in the OEM casting.

I.e. the "ported" OEM plenums on eBay are a complete rip-off.

As for the "85 mm TB", it's way too big for any 4.6L 2V n/a application and would likely hurt both performance (due to reduced charge velocity at WOT), and driveability (twitchy as hell at low revs/loads).

defconfire

Do you happen to know what the flow specs are for the PI intake manifold or the stock intake tube? I have been tracking those numbers down for quite a while and can't seem to find much.


Also where did you pick up your ProProducts Plenum

StriderTacticaL

Oopsies, I swear I read the link and didn't see that. It's my mistake, ok? I'm not new here, but I can't help it, ok?

medrick

All I've gotta say is cliffyk seems to be the man. I've read countless posts where he comes in and schools people. Always enjoy it. On a side note your push-button mod you have on your page. got any pics? and have you thought about making some and selling them?

defconfire

Are you talking about his push start or his cruise control buttons.

I think his cruise control buttons are one of the coolest things.

medrick

havn't seen the cruise control buttons. where can i find link. i don't see them on his page

cliffyk

I drew up the PB mod for a friend in the Carolinas, he installed it using my diagram and last I knew it was still working fine. I have never seen it or even and photos though.

You can see the cruise control switches in the shifter bezel here. When I installed the aftermarket steering wheel they had to be moved somewhere and that location seemed to make the most made sense.

medrick

oh ok i always wondered what those were in your avatar. thats pretty freaking sweet.