porting plenum on 91. did you increase hp?
Thread Starter
Drifting
Joined: Apr 2003
Posts: 1,379
Likes: 4
From: rome ny
porting plenum on 91. did you increase hp?
i was thinking of port matching my plenum on my 91 to a 52 mm tb. runners and the base are stock. is it worth it to port just the plenum or should i port the whole thing. i am tring to keep labor time to a min.. dont really want to pull of the intake. and if i do port the plenum should i port the side where the runners mount or laeve them until i get large tubes.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: porting plenum on 91. did you increase hp? (mos90)
I don't have any time slip data but I tend to do this sort of mod along with others while I'm "in there".
Since you have a 52mm TB it would be a good idea to port the plenum to match. Also remove the two protrusions just behind the openings and open up the two side walls as much as possible.
Yes it's a good idea to also port the openings into the runners. I flute the runner openings and then port match into the plenum. Think of it as a musical horn in reverse. Air doesn't like to make sharp bends at high velocity so fluting helps somewhat in getting that first "gulp" into the runners.
I didn't port my intake base but rather siamesed the base runners about 2" deep x 1" high. The result was 20chp gain at 5,400rpm with a little low end torque loss. To compensate I installed a 2,000rpm TC to launch higher into the power band and raised my A4 shift points into the mid 5k RPM range to take advantage of better breathing up top.
Have you done the other "free mods"?
-toss the "frisbee"
-install a 160deg stat & fan switch
-etc.
Since you have a 52mm TB it would be a good idea to port the plenum to match. Also remove the two protrusions just behind the openings and open up the two side walls as much as possible.
Yes it's a good idea to also port the openings into the runners. I flute the runner openings and then port match into the plenum. Think of it as a musical horn in reverse. Air doesn't like to make sharp bends at high velocity so fluting helps somewhat in getting that first "gulp" into the runners.
I didn't port my intake base but rather siamesed the base runners about 2" deep x 1" high. The result was 20chp gain at 5,400rpm with a little low end torque loss. To compensate I installed a 2,000rpm TC to launch higher into the power band and raised my A4 shift points into the mid 5k RPM range to take advantage of better breathing up top.
Have you done the other "free mods"?
-toss the "frisbee"
-install a 160deg stat & fan switch
-etc.
Thread Starter
Drifting
Joined: Apr 2003
Posts: 1,379
Likes: 4
From: rome ny
Re: porting plenum on 91. did you increase hp? (65Z01)
i tossed the frisbee aready. stage 2 tpis chip.tpis headers no cats. 160 stat. adj fuel reg. k&n with cut filter lid. 125hp zex wet nos kit. msd digital 6 ignition. the tpis chip has the fan on at 180 deg. and 52mm tb. also i have a 6 speed.
Burning Brakes
Joined: Jun 2003
Posts: 949
Likes: 0
From: smithtown ny
Re: porting plenum on 91. did you increase hp? (mos90)
i also have a 91 i ported everything, except the dumb butt that i am i should have changed the manifold when i did my injectors. but i was being cheap well guess what it has to come apart again. even with a port job the stock manifold won't flow like an accel or tpis. i bought a accel manifold. ebay has them brand new for $397 jegs wants $525. i have the accel lg tube runners so i wanted it to match. it's worth doing i have other things to, tpis long tube headers and so on, i feel more top end.
Thread Starter
Drifting
Joined: Apr 2003
Posts: 1,379
Likes: 4
From: rome ny
Re: porting plenum on 91. did you increase hp? (6spd)
i heard its a waste of time to port the stock manifold. and unless you have heads and cam you dont even need large tubes. thats what tpis said at least.
but usually they are right.
but usually they are right.
Burning Brakes
Joined: Jun 2003
Posts: 949
Likes: 0
From: smithtown ny
Re: porting plenum on 91. did you increase hp? (mos90)
well tpis isn't so hot my friend has a 91 auto i have a 91 6spd we both have the same mods to the t. they told him he needs a chip for $500 they told me i don't need one. what's up with that?? if tpis said it's a waste for runners then why port your plenum?? i could see adding a miniram or superram with stocks heads and a cam that's one thing. but i felt results. just like they claim a 95hp miniram gain on a stock motor if that was true everybody would have them. when you start porting i belive you should port all not just the plenum you fill up the plenum with air now it's going back into a smaller opening.
Thread Starter
Drifting
Joined: Apr 2003
Posts: 1,379
Likes: 4
From: rome ny
Re: porting plenum on 91. did you increase hp? (6spd)
if you port the plenm the next most restictive part on the intake is the base. if you have a 52mm tb you must port it to match at the runners and where the tb mounts. if you dont you will see no gains with your new tb. 10-12 hp. 20hp extra with a accel base so 52mm tb, ported plenum, and accel base = 30hp extra with no mods to chip neccessary. and you will breathe at at 200-300 more rpm. if you add heads and cam then you will benifit from large tube runners.
