I've searched and searched on the forum for someone that has used a revup lower plenum on a FI non revup car and can't seem to find any mention of it. I'm wondering because if you sit a revup and a non revup lower plenum next to each other its obvious that due to the shorter runner length that the revup plenum will have more volume than the non revup (correct me if i'm wrong), it would seem to me that a FI setup on a non revup would possibly show some gains with the use of a revup plenum. you would maybe lose some tq but with greater volume and shorter runners i would think you would gain more power overall and have more power usable at the top end. I'd really like to know if anyone has tried this or has any def answers on what would happen and any input from anyone is always welcome, tell me what you think

thanks

 

Runner length is much less important during boost (as positive pressure is driving flow) compared to a NA engine. I think that swap may help top end flow a bit, but you will lose low end torque before the turbo spools - as you predict. In essence you will narrow the powerband, favoring the right half. My prediction would be you would lose more low end (pre-boost) than you would gain at the top, which you can always up the boost for...

 

I just switched to the revup lower plenum on my 04. I have a Greddy TT setup. You can check my mods below on my cardomain page. A loss of torque down low in the RMP will be a good thing. It's the massive torque that's causing traction loss in first and second gears. Off WOT driving around town you won't notice any difference. I have not tuned the car yet so I don't know how it's going to work.

Westpak has the rev-up lower plenum on his non rev-up car. He is making power higher up than what I would consider normal for a non rev up motor.

Here is Westpak's dyno graph showing power til 6850 RPM. He is running the Greddy TT as well.



JET

 

But it's the torque after boost hits that's hard to utilize, not the NA torque (pre-boost), which you still want to maximize. Hard to say if the top end gain will outweigh the loss down low. I notice the OP is an automatic with a fully built tranny (and I presume a high stall TC). In that case, you will be in boost practically always so a revup plenum may have no negative impact on you.

 

I don't think you will narrow the powerband at all I think you will move the whole powerband 500rpm to the right.

Raising ther boost does not move the powerband to the right. It may actually make the powerband move to the left if there is a restriction in the exhast flow.

JET

 

I am always in boost. It may only be 2-4 psi driving around town, but your never really not in boost unless you drive like my grandma.

JET

 

^ sounds like all-around good mod in that case. On a separate note, that's the most linear power band i've seen for a greddy tt. Not sure what to make of it... Do you know if boost is being held steady or increasing?

 

that is very true, and i've never driven an FI 6speed z so i don't know how quickly you guys get into full boost. I am only running a 2500 stall, i'm trying to go the street tire route, but i still find that i'm at full boost almost instantly off the launch causing much wasted time spinning the tires, not only that but i don't come out of boost during shifting. so what i'm thinking is that even though i will lose some tq i will gain overall more usable power and better performance down the track. Atleast in my application if this could help me get a better launch and also the shifted powerband giving me power closer to redline should give me a higher trap speed at the end of the track. i would think through all of this that my quarter mile time would show a nice improvement from a $50-$75 quick and easy mod. and if it would also help out you guys running non revup 6speeds then we would all have a nice cheap and easy mod to do that may make a big difference down the track. The problem is that the tracks are still closed here in the mid west and i don't have the money to spare to do any dyno testing so i'm really looking for anyone that has a good dyno comparison or someone that has already done this and seen some good results at the track.

i'd also like to thank everyone for their input so far

 

did you put your 06 plenum on when you built your motor or did you put it on sometime after running your current setup?

 

The pink line above the blue torque curve is boost as you can see it is actually tapering down as the rpm's go up

I also have a plenum spacer and open dumps

it is probably in the tune as well, I did it conservative and don't start off with a lot of timing down low