Intercooler Pipes,

[DaveO74]

So I've got a mild 33 gtst and I am in the process of upgrading turbo (2835 pro s) and installing a plazmaman plenum.

I've decided to buy a new intercooler while I'm at it as my old one has seen better days and is a china jobby. Anyway I got to thinking, because the short pipe that runs from the plazmaman to the intercooler piping is 3" an then I will have to put a reducer in somewhere to tie in with the 2.5" pipework that is pretty much standard with most aftermarket pipework why not just go 3" on the whole of the cold side?????

The end tanks all have a 3" flange and reall the only thing that's going to be smaller is the turbo outlet on the hot side. So what would be the pros and cons of running one of the two options below.

Option 1: keep the 2.5" pipework on the hot side and run 3" on the entire cold side from end tank to plenum so the is no reducer (on that side)

Option 2: run 3" pipes on both hot and cold side and have a reducer at the turbo outlet.

Would running the extra .5" pipe diameter create any noticeable lag because it has to fill more area?

And could it cause any problems going from a 2.5" hotside into the intercooler and then out to a 3" pipe setup to the plenum?

Interested in your thoughts.

Thanks

[17psi r33]

search this web site, there is like a thousand threds about this.

[Thelen]

Basically .5" will be more laggy, but will you notice probably not. As for going from 3 to 2.5, it could help marginally in that because there is more volume the air will cool itself slightly more as it exits the intercooler, but again not really noticeable

[R31Nismoid]

More money, no gains.

Leave it

[32rrr]

i'd leave 2.5 on hot side, if you have to replace the cold side or modify it in someway just go 3" you wont notice any extra lag.

[W0rp3D]

no point, your restricted by the turbo outlet, stay 2.5, only reason to go 3 is if you dont like the look of a 3 - 2.5 reducer on your throttle body, in which case just use 3" for the cold side.

[DaveO74]

Thanks for the constructive replies guys (except for one........btw 17psi r33 I've been on these forums long enough to know search is my friend, was a fleeting thought whilst in the garage so I posted whilst searching)

The small Pipe after the tb that plazmaman supplies is 3" so i have no choice but to use it, hence my query. They also supplied me with an extra 3" pipe as well as my old pipework has no lip on one peice so has blown of over 18psi before.

I just didn't specify that I needed 2.5" so that's my fault. A reducer can be hidden away and be barely noticeable so that not a drama. Was more concerned about petential loss of response/lag by going up in size.

[W0rp3D]

The small Pipe after the tb that plazmaman supplies is 3" so i have no choice but to use it

Ummmmm, dosnt the TB bolt to the plenum? if not how far away is it?

[DaveO74]

Sorry should I say before the tb? You know what I mean, plazmaman > tb > small pipe (bov) > pipework under guard > intercooler.

I know it actually goes the other way if I was to explain it correctly.

[hypergear]

Air inside the cooler piping is compressed. Means the greater volume that needs be compressed the greater time would require to compress it. The cooler pipe should just be big enough to maintain boost pressure from the out let of the turbo, and ideal to have the shortest travel length.

So the current 2.5 inches will do fine or its at least more then big enough for the 2835.

[DaveO74]

Would I notice the difference in lag/throttle response being that I am doing away with around a metro of pipe work anyway? Surely it won't feel worse?

[89CAL]

I have 3" Piping with a Greddy copy FF plenum and a GT2835KAI, I hit full boost (18psi) at about 3400psi. But from what I've found the KAI is less laggy then the PRO S and doesnt reach the same power levels.

The only reason I have 3" piping is because a friend blew up his engine with the same plenum and I just bought his pipework off him to save me having to get it custom made for my car. It would probably be better with 2.5" but for what I payed I cant complain.

Go 2.5" if you can. As said its more then enough for the 2835.

[DaveO74]

Mmmmmm, well Ill see what I can do.

I have to use the small 3" that runs off the TB and I do have a 3" pipe for the next length but I am getting a new IC anyway so I'll see if I can get just some of the piping with it and I'll stick with 2.5"

Just to be clear I was going to keep the 2.5" on the hot side it's just the cold side I was wondering about

[paulr33]

i reckon 2.5" is fine

i think trucks run 3" ?

[blk94r33]

I have 3" Piping with a Greddy copy FF plenum and a GT2835KAI, I hit full boost (18psi) at about 3400psi. But from what I've found the KAI is less laggy then the PRO S and doesnt reach the same power levels.

The only reason I have 3" piping is because a friend blew up his engine with the same plenum and I just bought his pipework off him to save me having to get it custom made for my car. It would probably be better with 2.5" but for what I payed I cant complain.

Go 2.5" if you can. As said its more then enough for the 2835.

F***!

LOL

[89CAL]

yeah but its only pushing out 240ish rwkw at the moment. Its a great street turbo but I was aiming closer to 280rwkw which is what the Pro S does. They told me the KAI superseeds the Pro S. So far it looks like they were wrong, but will see what happens when I take it in for another touch up and dyno run

[DaveO74]

Hey Callan are you running an adj cam gear on yours?

[89CAL]

nah standard cam gears

[DaveO74]

If you don't mind mr suggesting grab yourself and adj exhaust cam gear before your next tune, you can then dail it in to get onto boost earlier. Could get all in by ~3200-3300

[89CAL]

Lol hmmm I dunno. It's slightly surging in 4th and 5th ATM when it's getting around 16psi (3000-3500rpm is the range it surges, only in high gears)

Anyway, just don't want to make the problem worse by bringing boost on even sooner, in talks with HKS about maybe putting a .8 rear on it but I dunno. Don't know enough about that stuff lol