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DCD 24th August 2002 01:38 PM

Larger throttle bodies for RB26
Any idea the benefits of larger throttles on the RB26? I've never really seen too many of these used on tuned cars and even demo cars. I imagine that more air means more power if combined with other variables(ie injectors, mapping...)

Any thoughts?

hipogtr 25th August 2002 02:24 AM

Here are my thoughts, DCD.

IMHO, the larger 6 throttle bodies are best used where increased high rpm air flow is required but not at the expense of responsiveness - as you get with a larger single throttle conversion. For example, circuit cars. However, they are not paricularly popular because:

(1) They are quite expensive (same costs as a single throttle conversion);
(2) The overall increase in surface area of the throttles is restricted due to machining constraints - its about 3-4mm increase in diamater for each throttle plate;
(3) The compromise in responsiveness from going to a single throttle body setup is outweighed by the gains in mid to high range torque that a large single throttle conversion provides; and
(4) In a high powered RB engine, there appears to be just as much to gain from a reshaped intake plenum and air charge entry point as increased individual throttle body size (ie. improved air trajectory into the plenum resulting in better air distribution, particularly for cylinders 5 & 6 which seem to suffer from getting more air than the other cylinders).

Cya O!

DCD 25th August 2002 02:31 AM

Thanks hipogtr. Thought as much after reading the single throttle body thread on SDU. I would have thought this could be a haflfway option between stock throttles and a big 80-100mm single. But as you said the price is far too high...

I was wondering what size of throttle bodies the old Gr.A engines used to run? Any ideas?

hipogtr 25th August 2002 11:53 AM

Hey DCD... Based on the Group A Calsonic BNR32 specifications (in the GT-R Owner's Book), they use the factory 6 butterfly throttle body. There's no mention of any changes or enlargements. Come to think of it, maybe that is on of the things that the Group A cars are restricted from changing.

Cya O!

DCD 26th August 2002 03:18 AM

Hipogtr....just picked up that book. Bloody great isn't it!!!

hipogtr 26th August 2002 09:03 AM

Definitely one of the best reference books I've seen around, DCD. I think that type of book will be coming out for a number of other cars as I've already seen the RX-7 one as well.

Cya O!

Scott 2nd September 2002 04:56 PM

So what is this book then guys?

Where can I get one and how much???

DCD 2nd September 2002 05:21 PM

Its called "GT-R Owners Book" and its 2500Yen. Contains a look at a few racing GTRs, goes through the RB piece by piece, and a few other things like GTR catalogues. The main section is a very good graphically represented guide of basic maintenance procedures. Gives you all sorts of info on parts that need to be looked at, tells you the tools you will need, the approx time you need, parts number and generally very useful info. Would be twice as good if I could read Japanese properly...but nonetheless a very good buy.
Its been out a month or so...but I would have no idea who would sell this in the UK

Philip 2nd September 2002 05:48 PM


Who publishes it?


DCD 2nd September 2002 05:54 PM

Published by Sanei-shobo Publishing Co., Ltd.

I also found a link:

GT-R Owners Book


DCD 2nd September 2002 05:57 PM

The book can also be ordered directly from them for 4610 Yen (airmail)

Hope this helps

Order Info

Philip 2nd September 2002 06:07 PM


Quicker than I could search for it - thanks.


MDG 4th September 2002 04:08 PM

Just to get back on the issue of throttle bodies, maybe some of you have already seen this thread on SkylinesDownUnder:

It makes for some interesting reading, especially if you're serious about drag racing.


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