4.0 GT3 Build - to upgrade to 4.0 plenum or not?
01-30-2018, 07:39 PM
#1
Rennlist Member
Thread Starter
4.0 GT3 Build - to upgrade to 4.0 plenum or not?
I have a big-bore FVD-based 4.0 997.1 GT3 making a healthy ~425whp with a reasonably streetable exhaust (GMG race cats, oem side mufflers and sharkwerks bypass). It was making ~440whp or so with a louder race exhaust but I want to keep it streetable. The car is at Goldcrest Motorsports getting some items refreshed and I have the opportunity to upgrade from the factory 3.6 plenum to the 4.0 plenum and have the car retuned. I am wondering if its worth the roughly $5k cost to do it (incl. parts, labor, dyno time, etc).
Any thoughts? Does the 4.0 just add power up top or cause some loss of torque down below? I know I have seen threads in the past with folks generally supportive of the mod. Just not sure how much power it will pick up and if its worth the cost of entry. All opinions welcome
Any thoughts? Does the 4.0 just add power up top or cause some loss of torque down below? I know I have seen threads in the past with folks generally supportive of the mod. Just not sure how much power it will pick up and if its worth the cost of entry. All opinions welcome
01-30-2018, 10:18 PM
#2
Rennlist Member
Below should be a good read. Ignore last pages as it delves into some aftermarket stuff. Original poster adds good info on before/after gainsliter build. Should help larger engine breathe better.
https://rennlist.com/forums/997-gt2-...ox-insert.html
https://rennlist.com/forums/997-gt2-...ox-insert.html
Last edited by TheSilverFox; 01-31-2018 at 08:37 AM.
01-31-2018, 12:08 PM
#3
Nordschleife Master
man, $5K....it better go faster!
01-31-2018, 04:06 PM
#4
Rennlist Member
Thread Starter
Below should be a good read. Ignore last pages as it delves into some aftermarket stuff. Original poster adds good info on before/after gainsliter build. Should help larger engine breathe better.
https://rennlist.com/forums/997-gt2-...ox-insert.html
https://rennlist.com/forums/997-gt2-...ox-insert.html
02-01-2018, 01:10 PM
#5
Yes, its worth it.
Dundon put a 4.0 plenum on my 3.8 with a paired exhaust and tune. Making +45WHP on the dyno.
by https://www.flickr.com/photos/88859026@N03/, on Flickr
by https://www.flickr.com/photos/88859026@N03/, on Flickr
by https://www.flickr.com/photos/88859026@N03/, on Flickr
by https://www.flickr.com/photos/88859026@N03/, on Flickr
Dundon put a 4.0 plenum on my 3.8 with a paired exhaust and tune. Making +45WHP on the dyno.
02-01-2018, 02:31 PM
#6
Rennlist Member
Thread Starter
Awesome. What exhaust setup are you running?
02-01-2018, 04:48 PM
#7
Trending Topics
02-02-2018, 01:39 AM
#8
Rennlist Member
OP - i just answered your pm — sorry for the delay
I concur with FJ Seattle
If you don’t do it, you will always wonder
small price to pay to know you have done it “correctly”
I concur with FJ Seattle
If you don’t do it, you will always wonder
small price to pay to know you have done it “correctly”
02-02-2018, 01:41 AM
#9
Rennlist Member
02-02-2018, 07:40 PM
#10
Rennlist Member
YES. I've seen before and after dyno plots with a 4L and 4.2L build with and without. Also with a stock 3.8 with and without.
Do it.
Do it.
02-02-2018, 09:01 PM
#11
Rennlist Member
Thread Starter
Thanks all. Very helpful. Was hoping to keep the current exhaust setup (GMG headers with 200 cell race cats, OEM side mufflers and RSS center bypass) but it sounds like the exhaust may need improving to maximize gains from the plenum.
The slippery slope! hehe
The slippery slope! hehe
02-02-2018, 09:03 PM
#12
Rennlist Member
Thread Starter
Anybody have dyno plots they can direct me toward? I know variance is large but curious what a 4.0 build like mine should expect with plenum.
02-06-2018, 02:25 PM
#13
Rennlist Member
I don’t have them.
But. I think Tom posted some in his thread?
But. I think Tom posted some in his thread?
02-06-2018, 02:40 PM
#14
Rennlist Member
4.0 plenum, intake manifolds(upper & lower) are worth ~20whp on a 3.8 with stock exhaust, stock tune.
02-06-2018, 10:19 PM
#15
Late to the party here.
After communicating with PJS about the 4.0 intake / plenum, Champion ordered (not easy back then) it for my 4.2L build.
Yes OP ... IT IS WORTH IT. :-)
Ranger
After communicating with PJS about the 4.0 intake / plenum, Champion ordered (not easy back then) it for my 4.2L build.
Yes OP ... IT IS WORTH IT. :-)
Ranger