GSXR Throttle Body Experiment: The Intro

Posted: June 13, 2011 in Uncategorized

First thing first, this setup has not been installed/tested yet.  It is right now still in the concept/R&D stage, but things are really looking good.  Whith that being said, I am going to open with all the info I have on it.  That’s what blogs are all about, free knowledge.

Why crotch rocket TB’s Supa?

Three reasons:

  1. My notchback’s engine compartment is very much vertically challenged, none, and I mean none of the off the shelf aftermarket will fit under the engine lid.
  2. With my type 4 cam selection, I need ITB’s to get the idle down.  The stock Ljet setup does work, but I’m expecting this setup to work better.  Also this opens a whole new world of modern injector options.
  3. The final and most important reason…$$$.  I’m a starving college student, I can not afford a $2000 EFI setup to upgrade the setup I already have, on the other hand, I can afford a $300 setup.

That’s right, I’m into this deal about $300.  That involved some exhaustive ebay searches, with some ninja-like bidding.

  • 04-05 GSXR 600 throttle bodies $30
  • 04-05 GSXR 600 complete wire harness(even came with COPs, friggin score) $27
  • (2) K&N R-2300 airfilters $70
  • (2) type 4 FI intake runners, free (they were spares I had laying around)
  • Cable linkage $100
  • 1.75″ silicone couplers, and t-bolt clamps, $20
  • (4) 10mm freeze plugs, $4
  • (4) 5/16″ hose barb fittings, $20ish
  • machine work…I owe my boy Eric big time!  He can do more for $150.

I reused/modified the stock composite fuel rails.  Involved some drilling, dremeling, tapping, and jb welding.  One day I’ll have some more attractie ones made so I can run AN fittings and braided line.

A gixxer motor is a inline 4, their TB are 2 double TB’s bolted together.  First step is to remove the choke plates, then pull the shaft out.  Unbolt the 2 bolts that hold the TB’s together.

The mani’s required extra milling to shorten them as much as possible.  He also opened up the insides a bit on the mill.  Eric put some steel piping on the lathe and turned it till the ID/OD matched the TB’s.  He machined the end castings down almost .500″, and welded the .500″ pieces of piping after we lined them up with the TB’s.  The end castings are cast steel, so he had to TIG weld with rod then let them slow cool in a bucket of sand.  Afterwards we trued up the head mating surface on a ultra flat piece of granite with 150 grit sandpaper.  They turned out friggin awesome, better then I imagined.  All thats left on the mani’s is to put 10mm freeze plugs into the factory inj holes.

I attached the TB’s to the mani’s with 1.75″ silicone couplers that I cut down to about 21mm, then used 1 t-bolt clamp per cylinder.  With the nearly identical OD’s of the TB’s and mani’s that won’t be a problem at all for sealing, plus with t-bolt clamps you can crank them down pretty good.

Filter selection for me is quite limited, I crunched the numbers and it turned out 3″ is all the overhead I have for a filter.  K&N has a nice 4″ one but it’s too tall.  They also have a 1.75″ one that will fit the TB’s perfectly but I don’t like the idea of a short air filter choking off my 2L.  So I gambled on a 78mm center to center 3″ tall fitler.  My hunch that the 3mm can be taken up with the clamps was right on the money.  They fit perfect on the TB’s.

The linkage is going to be a cable pull-pull type.  I searched around for custom made ones, and even tried to get ahold of a VW guy that makes a slick setup for Dells and Webers but he must not be interested in doing some experimental stuff, his loss my gain.  The custom ones seemed a bit pricey and most just were not properly suited for my application.  I got learned on how to assemble a cable myself and found a aircraft supply company that had most of the fittings that I needed.  I found a racing company for the rest.  I trial fitted everthing and it is all spot on, going to be very professional looking, and most importantly, fully functional.

There is still a few more things that need to be done to the TB’s so they can work as 2 seperate units.  One of the TB’s does not have a WOT stop or a idle adjust (thats needed for syncing them in).  no big deal, i used a well placed pin for the WOT stop.  The idle adjust screw just required a hole drilled and tapped and knurl topped screw with a spring, about $2 at the hardware store.  there was even a boss cast into the TB for the idle adjust, lol.  Sorry no pics on that.  The final thing is the holes for the choke shaft need to be plugged.  I used some 1/4″ aluminum rod and jb weld for that.  After cutting all the parts and cleaning up the cuts on the belt sander and gluing them in.  I went over it with a small sander and got them all nice and flush.  Once again no pics.

The injector angle is not absolutely ideal, I have a feeling cold starts are going to suck balls.  That pic above is what the intake valve will see.

A couple of interesting observations, these things did come with a TPS, thats good.  I can mount a IAT sensor on the bottom of one of the air cleaners.  I think I will have about a 1/4″ of overhead, it is going to be close.  From what I can tell the injectors are 185cc (same size I have in there now), I’ll find out after I fire it up with them.  My cable setup is going to replace the stock cable but I’m going to have to run it outside of the tunnel, either that or else I have to put a bigger throttle tube inside the tunnel.  This car is not stock so I can care less about it.  That’s about it for now, after I get it installed and running I will make another blog…stay tuned, same bat time, same bat channel.

  1. Jesse Rivas says:

    Outstanding work on the ITB setup. Would you mind sharing the sources for the various ITB parts ie clamps, linkage and assorted bit. About how much including the MS do you have spent on the entire FI portion.


    Jesse Rivas
    Santa Rosa

    • I don’t mind devolging all the nitty gitty details of this ITB build, but it will be too much info for a reply. I’ll make a post of all the details and I’ll include prices too. I’ll get right on it.

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