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Rb26- Enlarging Std Throttle Bodies

XRATED

By XRATED,
in Engines & Forced Induction

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XRATED Veteran

XRATED

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As topic states:

I'd like to know if anyone has had they're standard throttle bodies enlarged on an RB26.

If so, any result data and contact details for who they used for the work would be greatly appreciated.

I havn't really seen or heard about it in Aus. I have noticed a few japanese builds have enlaged std tb's...

Cheers

Justin

PS I'm looking for constructive comments from people who have real world experience.

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GTRNUR Grand Master

GTRNUR

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Getting a normal single throttle body is an expensive enough operation. I cant imagine what it would cost to have 6 throttles done at once. I think it might be easier to modify the base plate, weld and match port it to some aftermarket IDF/IDA/DRLA throttles. Injection Perfection does some really nice throttle with trumpets, which you could then build a custom plenum around. Ive seen then in 48, 50mm and larger. Extremely nice quality.

The other options are to have the throttle shafts profiled, or change to these fancy looking things.

http://www.gtr.co.uk/forum/106680-shaftles...s-rb26dett.html

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XRATED Veteran

XRATED

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I would like a set of these..but they dont seem to be available

I spoke John thismorning. He's going to try and get back into manufacturing a prototype set soon... Know one in the UK seems too interested though.

I'm not really holding my breath for a set... prices are going to be eeeexy! too.

Justin.

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  • 3 months later...
ed_ma61 Contributor

ed_ma61

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I spoke John thismorning. He's going to try and get back into manufacturing a prototype set soon... Know one in the UK seems too interested though.

I'm not really holding my breath for a set... prices are going to be eeeexy! too.

Justin.

thread revival

i had mine bored to 48mm, had the shafts machined down (not quite shaftless but close), and new throttle plates installed.

cost about AU$350 in total

email [email protected] if you still want info. have pics of what we did, and contacts if sill required

cheers

ed

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ed_ma61 Contributor

ed_ma61

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EFI Hardware can do them 0398735400.

i got EFI hardware to do the new throttle blades, but i had the bores milled and finished locally in syd. cost SFA altogether. can recommend EFI hardware to do this.

on the rb26 body you wont get over 48mm. maybe 48.5mm, but that would REALLY be pushing it. 48 is clearly doable though

48mm_throttles_0006.jpg

48mm_throttles_0011.jpg

48mm_throttle_0001.jpg

48mm_throttle_0002.jpg

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OVADRV Collaborator

OVADRV

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From memory reading another thread enlarged throttle bodies are useless unless you've had a valve job port polish,as the thread said your still going to get the same amount of air passing through the intake valves.Is this true? Ive always wanted to do enlarge the Tb but not sure.

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rob82 Mentor

rob82

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The std throttle bodies have a combined area of around the same as a single 100mm throttle body. Porting the std throttle bodies is a completely useless mod unless your making over 1000rwkw. Garunteed the ported throttle bodies are a bitch to seal and have all sorts of idle issues. I thought everybody knows not to f**k with the std throttlebodies.

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ed_ma61 Contributor

ed_ma61

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The std throttle bodies have a combined area of around the same as a single 100mm throttle body. Porting the std throttle bodies is a completely useless mod unless your making over 1000rwkw. Garunteed the ported throttle bodies are a bitch to seal and have all sorts of idle issues. I thought everybody knows not to f**k with the std throttlebodies.

really? wow, i didnt know my engine had such problems!?! thanks for the heads up, ill go remove them now

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Supa Steve Enthusiast

Supa Steve

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Posted (edited)
The std throttle bodies have a combined area of around the same as a single 100mm throttle body. Porting the std throttle bodies is a completely useless mod unless your making over 1000rwkw. Garunteed the ported throttle bodies are a bitch to seal and have all sorts of idle issues. I thought everybody knows not to f**k with the std throttlebodies.

Totally agree mate.

really? wow, i didnt know my engine had such problems!?! thanks for the heads up, ill go remove them now

Ed your application is totally different, Rob is refering to RB26 setup.

Edited by Supa Steve
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ed_ma61 Contributor

ed_ma61

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Ed your application is totally different, Rob is refering to RB26 setup.

not with the 'guaranteed to not seal' part. thats a poor call. and if someone had a problem once with boring a throttle body, then the issue should be brought up with the machine shop, not solved by pissing on the idea in general for generations to come :)

also, throttle blade/bore dia is not dictated by some simple 6 45mm is X times bigger than some Z sized single. that argument is rubbish. you need to look at your port velocities and harmonics, which are a function of bore/stroke, cam timing and intake length. someone may very well need a 48mm throttle in their particular setup.

but im not here to tell someone how to build an engine. OP asked if/how you can bore the throttles. above pics demonstrate how.

cheers

ed

Edited by ed_ma61
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XRATED Veteran

XRATED

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Thanks for all the replies guys... I completely forgot about this thread.. ah ah ha

I ended up getting EFI hardware to bore my tb's out to 48mm. They sent them back to me a couple of weeks ago- they look great.

I don't forsee any idle problems.. The tb's have been machined to a much tighter tolerance than factory and hand finished. I also sent them some re-designed shaft seals that won't pop out under boost and leak. If you have stock shaft seals- they WILL leak under boost. If there is a problem with sealing, I'll send them back... I have plenty of little tricks to be employed to get a good seal too... Really it's not an issue.

It's a bit silly to say that "Garunteed the ported throttle bodies are a bitch to seal and have all sorts of idle issues"

And no I'm not chasing 1000kw.. thats silly. I'm not going into why I went with enlarged tb's as it would take all day to explain, let's just say I did some calculations, taking into consideration the projected airflow, cams, runner length and volume, plennum volume (greddy intake manifold), port size/volume, valve size, lift and engine capacity... The bigger tb's will provide some gains.

For those who have had they're tb's bored out, what gaskets or gasket material are you using? Has anyone made a phenolic gasket yet?

Cheers

Justin

Edited by XRATED
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PM-R33 Grand Master

PM-R33

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Let us know how you go with them once they are on the car. Would be interesting to hear some real world experience with such a mod.

Edited by PM-R33
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XRATED Veteran

XRATED

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Oh and if your considering this, you won't really see any benifit unless you have a well flowing head or much larger capaicty behind them... Also a larger plenum is required to get the best from them- the stock 26 plenum is to small.

J.

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