Stagea Throttle Body Boring - Anyone Done It/can It Be Done?

[Stagea_Neo]

I was just curious if anyone has had the throttle body bored out and a bigger butterfly put in to allow more airflow?

In saying that, can it actually be done, is there enough metal to work with on the Stagea throttle body.

I was going to get it done ages ago on my r31, as there was quite a few mm to play with,

but never got around to it. Another option with the R31 was to put on an Ford XF throttle body.

Think the r31 is 60mm and the xf 76mm from memory.

[scotty nm35]

The M35 is 76mm also. Of course it would be hard to install without putting the rest of the engine in.

It would probably give bugger all improvement unless that is the only restriction you have left, have you done intercooler, piping and turbo highflow?

[zei20l]

TB makes a good difference on the top end even on mildly modified engines.

im looking for something, maybe a VQ35DE one is larger than the VQ25DET

[Stagea_Neo]

thanks for replies

if it helps the top end a little/lot that can only be good, it needs a bit of help there in stock form.

no mods yet all stock.

planning to do a stealth cooler, engine management, boost controller soon.

high flow maybe later down the track.

[Sydneykid]

I have run over 320 rwkw through a standard RB25DET throttle body with no measureable boost difference before and after the throttle body. Unless you are looking at higher power outputs than that, the standard throttle body is not a restriction, so changing it or enlarging it will make zero difference, waste of time, money and effort.

Cheers

Gary

[zei20l]

of course there is no boost difference after you changed it, it doesnt change the boost! it decreases a restriction in the intake piping.

i have dyno outputs before and after a TB was done on a 'lowly' SR20. bumped 170rwkw to 175rwkw.

[_Ryan_]

of course there is no boost difference after you changed it, it doesnt change the boost! it decreases a restriction in the intake piping.

i have dyno outputs before and after a TB was done on a 'lowly' SR20. bumped 170rwkw to 175rwkw.

and restriction affects pressure

[zei20l]

sorry yes it does, i should have specified at WOT

[KiwiRS4T]

of course there is no boost difference after you changed it, it doesnt change the boost! it decreases a restriction in the intake piping.

i have dyno outputs before and after a TB was done on a 'lowly' SR20. bumped 170rwkw to 175rwkw.

You are missing the point. SK didn't change the throttle body but just measured the boost either side and found it to be the same thus indicating that the throttle body on a RB25DET is not a restriction.

[floody]

thanks for replies

if it helps the top end a little/lot that can only be good, it needs a bit of help there in stock form.

Its almost completely pointless, a total waste of time and money. The throttle body is no restriction worth worrying about. It is also certainly not worth wasting money on as your first modification!

Edited July 5, 2009 by floody

[zei20l]

ahh duh, i should stop posting while watching tv. thanks for clearing that up

but you cant say a TB makes NO difference at all. besides the fact that i have dyno proof

[wolverine]

was the car dyno'ed back to back.

5kw is a pretty skinny margin on a dyno to be sure there wasn't other changes like ambient temps, tyre pressure etc.

[zei20l]

the temp didnt change much, and tyre pressures? that was the last thing on my mind lol

[Stagea_Neo]

Thanks again for the feedback.

I'm in two frames of mind now.

Yes do it, no dont.

I don't think the existing throttle body would be restrictive,

I'm of the thought that the more air you can get in the better (with correct tuning).

p.s. I was advised originally by an engineer/mechanic to do this on the r31,

if he says it's worthwhile, I tend to agree.

In saying that I always get second opinions.

[wolverine]

I wouldn't spend money on a new throttle body when there are places you can spend money and definitely make power.

[zei20l]

any restriction is a restriction. is allows the volume to flow. if the engine didnt need volume, all the intake piping would be 1/4 inch in diameter.

[BensDR30]

If you're chasing that last few HP, then the way to go would be to machine the actual butterfly & shaft to remove any protrusions. i.e. machine the edge of the butterfly to a fine edge, clean up the screw heads & shafts and smooth the transition when the butterfly mounts to the shaft.

Having said all that, the kind of mods I've just listed would be something you'd do when stuck with specific parts that were too small, but were homologated and therefore mandatory.

There's no way I'd be even considering such bollocks on a street car - especially a turbo where you could increase the boost by a fraction of a psi & overcome the 'restriction' anyway.

[wolverine]

any restriction is a restriction. is allows the volume to flow. if the engine didnt need volume, all the intake piping would be 1/4 inch in diameter.

what about the diameter of the airfow meter? what about the pre and post intercooler piping to the throttle body? what about the individual runner diameters?

assuming you change the throttle body which doesn't appear to be a significant restriction (if it even is a restriction) seems illogical without changing hundreds of $$'s worth of other pipework as well.

comparing to an Sr20 with no clear indication it was back to back tested on the same day is pretty thin evidence when trying to compare it to a completely different car. i have seen my cars vary > 5kw on an individual dyno pulls back to back which means that there are many things that vary dyno figures beyond the changes you make.

i can see the logic of going to a larger throttle body if you are changing plenums to something like a Greddy plenum (rather than using a standard throttle body adapter) but on any other car more time road tuning/dyno time would get you more bang for your buck.

nevertheless, bigger isn't always better, more peak flow doesn't always equal better performance but that is getting a little off topic.

[unique1]

sydneykid knows what he is on about, he isnt someone who says something without experience with the parts in question. The 5kw difference is the difference between a regular dyno run i wouldnt read into it at all, the throttle body would have to be the last possible modification i would ever consider, its gonna gain bugger all.

Its a pretty easy path to make decent power, unless you have done all them i definately wouldnt waste your time.

[zei20l]

ok so im clearly wrong after reading all of your guesses.

dont do the throttle body, it appears its a waste of time. i would know because i have tried it with successful results.

anyway, the AFM isnt a restriction till you increase the boost so much you out-flow it.