GSXR Experiment Part II

Posted: April 12, 2012 in Uncategorized


So I got a good understanding of what worked and doesn’t work using GSXR TB’s.  The first iteration was with the 04-05 gixxer 600 TB’s (38mm) on modified type 4 fuel injection runners.  The design was flawed, but I still managed to make 35-40mpg on a recent trip!  The manifold design looked good on paper, but reality is cruel mistress and I had numerous problems sealing them to the TB’s and it didn’t take a lot to pop them off the mani’s.  The also had way to short intake length.  So back to the proverbial drawing board.


Version 2:

  • 06-07 GSXR 600 throttle bodies (40mm)
  • 03-04 GSXR 1000 #24 injectors
  • custom fuel rails, I made them 🙂
  • custom pulley (my buddy Devin on STF made it, it’s sexy)
  • idle set screw from a 00-03 gsxr 600 TB (I just happen to have it laying around)
  • custom bolt plates between TB’s and IDF manifolds (one of the guys in the club made them on his CNC plasma cutter)
  • Spigot flanges (4), mates the TB’s to the bolt plate… KHS-004
  • modified Weber DCOE 45 velocity stacks (4), silicone couples and bolt clamps
  • fuel system is now all -6an, Performance Products FPR, black fittings, and black braided lines…sexy
  • reused my cable linkage, but made a new custom bracket for the right TB
  • some porting of the IDF mani’s and bolt plates

Sounds like a lot going on, but it was about a full days worth of work and it was for the most part all bolt together.  The big improvement on the design is use of the spigot flanges and bolt plates.  I get a real solid mount for the TB’s and it is fairly straightforward to mount to IDF manifolds, which also makes this setup universal for all the ACVW platforms both type 1 and type 4 engines.

Throttle bodies:

I am using the 06-07 TB’s which are basically a similar design to the 04-05 TB’s just a little bigger.  They also have 8 injectors instead of 4, so I had to plug 4 extra holes and I removed the extra rail mounts.  There is still the extra holes to fill for the servo choke plates.  The 04-05 TB’s use a progressive oblong pulley and the 06-07 TB’s use a round pulley.  Devastator on shoptalkforums CNC machined me a very nice round pulley.  I “modified”, AKA chop sawed the return spring bracket behind the pulley.  That was one issue I didn’t get right on the 04-05 TB’s and had to use a extra spring.  No extra sping on this version.  I also didn’t like idle set screw I used on the first version.  This time around I set screw from a junk 00-03 TB that I pillaged a pulley from.  I had to get a oddball 5mm x .5 tap, mcmaster-carr to the rescue.  That turned out awesome, it looks completely factory…nice!

Bolt plates:

The big problem is the 75mm center to center of the gsxr 600 TB’s and 90mm center to center of the IDF mani’s.  The bolt plates are 3/8″ so there is room to do some porting.  I only did a light porting to smooth the transition.  There is still plenty of meat on the mani’s if I want to try and make a straight shot for the air.  I’m trying to create some turbulence to see if I can get better atomization and vacuum.  Seems to be working, I have more vacuum at idle and in cruise, but WOT I’m seeing atmosphere.  I also make some paper gaskets for between the heads and mani, and bolt plates and manifolds.  I went with a fancy hardware choice to mate everything up too.  I used SS flat head cap socket bolts for the bolt plates, and metric flanged button heads for the spigot flanges.  All are 8mm x 1.25, that’s the same size and pitch as the original studs on IDF mani’s.


I could have just modified the metal rails that are stock on the 06-07 TB’s and used the original injectors but I have a set of gixxer 1000 injectors that I have been wanting to run.  The 04-05 and 06-07 TB’s use injectors with 11mm inlets.  the 03-04 1000 injectors and most cars use 14mm inlets so now I have a lot more injector options.  Also the 600 injectors are #18 and the 1000’s are #24, I have been wanting to try out e85, I now have plenty of inj overhead to mess with ethanol.  The rails are extruded aluminum from RMR, I got it from their ebay store.  It was $5 a foot because it was supposedly damaged, even though it looks fine to me.  I used this to machine the rails for the inj a bit pricey but it does a fine job.  The plan was to use -6an, so I used a 9/16-18NF tap on the inlet/outlet of the rails.  There is supposed to be a grove machined for the oring AN fittings, I didn’t want to pay $300 for that so I just JB welded the fittings on.  That is ghetto but it works well.  The last step was to make a bracket to mount the rail to the TB, unfortunately the 06-07 TB’s only have one mounting boss per TB, so the mounting bracket has to be perfect or a car-b-que can result.  When everything was done, I cleaned the rails up on my drill press using scotch pads, the result was a nice brushed finish.

Overall impression:

The longer intake run and the bigger bore creates a sexy growl when I’m on it.  I cruise and idle with more vacuum now, so much so I re-indexed all my maps to take advantage of it.  I haven’t taken it on any big trips yet but I expect the same or better mileage.  I do have a lot smoother midrange and did not lose any throttle response.  The verdict so far is this version is all win.  I have a long trip in another week of so, I’ll use my GPS to try and get a accurate mpg.

Here is a fun little video, that’s about 20 minutes of tuning

This slideshow requires JavaScript.


  1. Greg T. says:

    I want ignition! I want ignition! I want to see how you adapted a trigger wheel to stock type 4 cooling.

  2. I just had the motor out to fix a couple of oil leaks, I could have snapped some pics. It’s real simple and real cheap. I found a guy on ebay that makes trig wheels cheap, paid him $7 extra to open the center hole to 1.5″. Then I drilled the 3 bolt holes into it and the one centering hole. I bolted a ’89 mustang VR sensor to the back of the shroud (on the oil cooler side). Works alright, but I have to take the oil filter off to disconnect the connector. You also have to leave the 1mm spacers that goes behind the cooling fan. It cost about $30 for the wheel and VR sensor. Search corvrman on ebay sellers.

  3. Vin says:

    Nick, Nice site. Nice car. Nice work. Stumbled here from Thanks for sharing.

  4. David Johnson says:

    Are you still in the Houston area? I’m looking to switch to a Megasquirt system for a 1.8 type 4 in a 914. I read your blog with interest. I was hoping to use you as a resource for the conversation.

    • I am still in the Houston area when I visit my mom, the car is at my mom’s and I try to take it out to the Saturday night homedepot show in Kemah. It’s a whole lot easier to show then tell plus I can give you a ride in it so you can get an idea what it’s like. It will be about 3 weeks until I’m back in town.

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