R33 Intake Plenum

[skyxhp]

Has anybody modified the standard intake plenum on a series 1 R33 skyline so that the throttlebody is front mounted ? Is there any problems apart from making up a new throttle cable. If so have you any pictures of this mod.

[MacGuyver]

Sub Zero make modified intake plenums with the throttle body front mounted, supposed to be pretty good ones too. I think Greddy also make a modified inlet plenum for S1 R33's also?

"Games don't affect people. If Pacman affected us as kids, we'd all be running around in darkened rooms munching on pills and listening to repetitive music."

[r33_racer]

yeh you should do a search cause this topic has been coverd with some massive arguments for and against it, alot of interesting material too.

In short, it wont work properly as it was not designed to take air from the front of the plenum, but the centre. Look into it more before doing anything.

Normally only change plenum when you increase engine capacity.

[MacGuyver]

Auto Salon did a review of the new bolt on Plazmaman intake plenum and intercooler upgrade last month. They said it made solid power gains, throttle response was sharper and the turbo spooled up a lot quicker. The install was done on a stock R33 GTST. But I have also read about them not working too well in some cases like r33 racer has said. I wonder what's so special about this kit? They do say that the kit was designed for high performance applications in mind though.

"Games don't affect people. If Pacman affected us as kids, we'd all be running around in darkened rooms munching on pills and listening to repetitive music."

[paulr33]

theyre trying to make money and sell his brand, of course they will say it made more power and increase response.

[paulr33]

i dont see how it could make the turbo spool up quicker

[R31Nismoid]

do a search

stock item is perfectly good for oever 350rwkw.

[BookyVL]

Yeah, I had mine done. I had Sub Zero build me a RB25DET with some nice goodies on the inside into my VL.

They modified the intake plenum fo it was front mounted...

Really good job, built engine well and all welds etc very neat...

[MacGuyver]

I think the claim they made about 'the turbo spooling quicker' is based on the shortened intercooler piping, i.e. less lag. But I've read on these forums that the increase in ic piping doesn't really make all that much difference in lag times/throttle response, does it? In the test they claimed to have gained 17kw and 47Nm of torque, with a consistent power and torque increase through out the rev range. But I'm more inclined to believe that the stock plenum is fine.

"Games don't affect people. If Pacman affected us as kids, we'd all be running around in darkened rooms munching on pills and listening to repetitive music."

[BookyVL]

Here is a pic of my engine bay in the VL before it was sold:

[StockyMcStock]

how much did they charge you to do that BookyVL? i need to do something similar to mine..... but i bet the local fabricator would be a heap cheaper than SubZero.

[r33_racer]

I think if u were to reuse the standard runners...you could in no way reuse the top throttle part of the intake, as it was designed to take air from the centre and go down evenly, not fed in from the front. A whole new top unit would have to be constructed to at least try and feed the air from front to back and try to cover all 6 runners evenly, even though the bottom runners were designed to work with the stock top chamber only. Im only a fabricator, but from what ive read and seen myself, modifying the std top chamber couldnt improve performance as a whole all over the range, if at any range at all. Either leave the std plenum alone, or use a fully custom plenum or greddy unit which incorporates chamber and runners ready to bolt onto the head. Now whether they increase your power or not is another different story which is also debatable, depends on your engine and setup as per bloudy usual.

[Dahtone Racing]

thats review in ASM was plenum and FMIC kit not just the plenum

[Freeman]

Thats what MacGyver said man

[Dahtone Racing]

oops i missed it

i must be going blind

[ISL33P]

like r33 racer said, original plenum is designed for a side feed.

the power increase will be mainly down to the intercooler upgrade.

increased throttle response/better spool will be down to the shorter piping without a doubt. tried and proven over and over again.

[StockyMcStock]

i don't expect it to improve power at all, i just have to have a front-inlet plenum because there's a supercharger and a GT40 on the other side of the engine. there is no possibility of retaining the standard inlet design at all. instead of buying a custom unit i would prefer to just mod the standard one cleanly, but whether or not the charge distribution would be good at all is anyone's guess.

having said that, i have no more faith in a brand name plenum than a modified standard one, doing flow simulations on similar systems in solidworks has led me to the conclusion that it's basically all guess-and-check until the engine doesn't blow up. flow testing is largely useless for a complete system of inlet pipe-plenum chamber-runners as it doesn't simulate what's actually happening when the engine is on full song. pressurised air in a system feeding six runners out of a box is a LOT different to just pulling vacuum through the pipes individually and measuring how much comes out.

anyway enough ranting - how much did it cost you Booky?

[R31Nismoid]

get a purpose made one then, not a cut'n'shut which wasnt designed for the T/B to be on the front to begin with.

There is actually engineering behind it, doesnt have to be a Jap one.

Locally made properly designed ones are common

[StockyMcStock]

i don't believe there is any significant engineering behind ANY of them, that's the problem

if i really wanted to i would make one myself but it will give similar results to the standard modified one i believe, just cost me a lot more.

[R33NT]

I have a cut and shut plenum identical to the one on the VL that i am looking at selling because i can get a greddy for $900 (brand new).

I have been told that the cut and shut is fine as long as you use a standard turbo and dont run more than 1 bar. The problem is that if you exceed that it will starve some of the cylinders.

If you where going to do a cut and shut you should probably cut a wedge out of the plenum starting at the front and increasing towards the back (then weld it up afterwards) so that your plenum tapers of towards the back. Then flow bench it and move the throttle body to the front and by then you could have just dont it properly and bought a greddy plenum (probably for the same amount of money)!!!