Urgent Info Needed On Plenums!

[Sydneykid]

Hi guys, the standard inlet manifold, plenum and throttle body are good for 450 bhp with much more even distribution than any aftermarket plenums I have tested.

For your $2K, 25GTT I would get the standard turbo ball bearing hi flowed. No fabrication required, and you should be able to do the swap over yourself with a limited amount of skill and tools.

I reckon that's a better result for your money.

[APA]

changing the plenum does not increase hp, thats what i thought anyways?

it's more over a increase in response from the engine, to shorten intercooler piping and to move the air easier and quicker then the space provided in the stock plenum!

adrain:p

[JimX]

Adrian_perth, that was my understanding too. However with my old FMIC, the plumbing was absolutely atrocious. The whole lot needed to be re-done because of right-angle bends, and the intercooler itself replaced because it was too small.

I thought I could either run a new set of pipes up and along the top of the engine, or spend a little extra and get a front-facing plenum with less pipework. Doing the latter saved me a bit of dough on 2 extra pipe bends and maybe a metre of straight pipes, so the plenum cost was slightly compensated by needing less pipework.

The front-facing plenum definitely gives me better throttle response, and also seems to bring boost on a little earlier. It can also compensate for lag created by a too-big intercooler because it reduces the volume of air in your intake tract.

[sidewaymambo]

Is there any reason to stay with stock 70mm throttle body rather then go to something like 90mm throttle body?

[JimX]

A throttle body wider than the rest of your intake would only let more air in at WOT. A smaller throttle body can do the exact same job at less than WOT, just with the butterfly valve open slightly more. At WOT, if the rest of the intake is narrower you'll still be limited by the flow of the rest of the intake.

On forced induction cars throttle bodies are less important than on NA cars. The plenum chamber itself holds a supply of pressurised air for the engine and the turbo/supercharger keeps it under pressure when engaged, whereas in an NA car the engine itself has to suck all the air through a small throttle body. ie it has to do all the work on the fly as opposed to having a ready supply of air right next to the inlets on the manifold.

Putting a bigger turbo on but keeping the same throttle body on your car will do lots more for power than keeping the same turbo but putting a bigger TB on.

There is a point whereby a bigger TB will help your power, but I suspect it's somewhere over 450hp. Sydneykid has said above that the standard intake is good for 450hp and I believe him

[sidewaymambo]

I was wondering that "heated gas flows faster" may apply as well, the compressed air cooler after flow through the intercooler, it will "slower" and less acceleration, so if put on a big throttle body, it might have less acceleration, unless running more boost, just a though..please correct me if wrong..

BTW, JimX whia is "WOT", thanks

[JimX]

Whoops sorry, WOT is Wide Open Throttle.

[Ryno]

Does anyone know if Hills motorsport has a website? I'm interested in finding more about their plenum

[JimX]

They used to have a website but I think it's been down for a few months now. They are really hard to track down if you don't know who to ask about them because they aren't in the White or Yellow pages and now that their website is down (or changed domain names without me knowing how to find it) it's even harder. Give them a call and ask them about it. If you want to see what their plenum looks like, try to find a photo of B-Man's engine bay, because he has one fitted. IMO they are very sexy!

[Ryno]

Thanks mate, I'm wondering how one would go on a non-turbo RB30 conversion

[sik32]

I am currently doing the rb30/25 conversion, and will be getting a custom plenum made up with twin rb25 throttle bodies. The reason we chose the twin setup is because 2x 60 mm throttle bodies equals more than most large aftermarket TB. we can then stage them, so that it reduces lag. slightly!

the only problem i can see is a slight restriction

[Ryno]

Sorry mate, I mean I'm staying non tubo... The reason I want the plenum is so I don't have to lose my sway bar, as the VL block is 3cm higher, my standard plenum will be too high

[JimX]

Originally posted by Ryno

Thanks mate, I'm wondering how one would go on a non-turbo RB30 conversion

Oh, if it's non-turbo then the bigger TB is definitely worthwhile. And also, the front-facing plenums will be a waste of time and money! You will either need to make a new air box for it on the opposite corner of the engine bay (very time consuming and tedious) or keep the same over-the-engine setup to keep the intake as short as possible.

The only reason for the front-facing plenum is to cater for front-mount intercoolers. Even if you had a turbo Skyline with the stock cooler it would be a waste of time.

[Steve]

Hills plenum uses the stock runners, and just plants a new chamber on the top to facilitate a forward facing TB. The intake runners are radiused, but not bellmouthed.

The acutal plenum sits quite high at the front and only just clears the bonnet - this is with stock RB25. If anything I believe it would have less underbonnet clearance than the stock plenum.

I got one of these believing it would sit a bit lower than it does, unfortunately, by the looks, I would think it would not clear the bonnet with another 3cm height:(

Get a jun or greddy plenum, or get a decent belmouthed plenum made that allows for extra deck height - wish I did.

Anyone want to buy a hills plenum?

[warrick]

steve can you post a pic of the plenum or email one to [email protected]

cheers

warrick

many thanks

[Steve]

Sorry warrick, my 2 yo has lost (hidden) the digital camera:(

If you do a search, b-man has posted up quite a few pics on the forum:)

[warrick]

thanks for that steve.yeah i did a search but every link i found to a pic he had didn't work unfortunately.b-man if you read this can you send me a pic please.

[email protected]

cheers

warrick

[B-Man]

Oh goody another plenum thread !

Yeah, link sometimes goes down due to dodgy webserver....

I will be getting my Hills Plenum flow tested soon (hopefully) - It looks good - but I'm not sure about the benefit.

Steve, you got one did you ? PM me your findings.

Spend the extra and get a GReddy one - or just for get it if you are aiming for under 450HP.

[warrick]

thanks anyway b-man.these links dont work either.thank you for the response .

cheers

warrick

[RIPS]

We do this sort for R32, R33, RB20/25/30.

The are not just a top 1/2, they have full equal length trumpets,

and retain the original injector and fuel rail mounts....

This is R.I.P.S RB30det 4WD