Been toying with the Idea of doing a cheap version (non Jenvey) of EFI for my RVF using OEM parts and off the shelf EFI computers for a while, but have mostly been hung up on the lack of access to hard parts to see if it is even possible to do. I finally got the first piece of the puzzle, read on.....

I was cruising Yahoo Auction (Japan) and came across a full set of Suzuki GSR400 Throttle Bodies (TB's) and decided to snatch them up for around 100 USD. They arrived today and I am impressed with the package and setup as a whole, a nice piece of kit in true Japanese quality that we all come to expect (Mikuni is the Manufacturer for those keeping score). I had always had an eye on the GSR400 TB's since they were one of the first 400's to have EFI. What I didn't know is how high tech they went with it. I knew I could at least try when I noticed that the TB assembly is two throttle tubes in one mold and then two molds are bolted together, much like any of today's TB's on larger inline fours. If you un-bolt them then you can line the up for the V-configuration and get to work on the linkages and plumbing.

What I didn't count on was the GSR400 TB's having a primary (PV)[controlled via cable to throttle] and secondary (SV) set of butterfly valves used to modulate the flow of air into the intakes. the first set of valves at the opening of the TB's (SV's) are controlled via a stepper motor on the TB's that is connected to the throttle position sensor (TPS) housing. I am sure that the SV's are getting their inputs based on Vacum Pressure Sensor also on the TB's and of course from RPM's as well. The PV that are controlled via the throttle cables are lower and closer to the cylinder intake tracts and are the same size. Having a computer controlled set of valves complicates programming immensely since I want to go the cheap/easy/uncomplicated route (wait, this is EFI we are talking about...), but if it could be pulled off will help the drive-ability of a road bike. We shall see if it proves too complicated, well I could always remove the valves and plug the holes......

Pics/dimensions to come....

Comments, ideas, thoughts... always appreciated in the house of NC gospel. Especially from the Deacons of Speed; Venom51, G-force performance, mrhuel, and countless other .

Michael Ruehl and Parus are you friends for this.

Going to be superb when one of you sorts it out and posts a vid and dyno run.

Without sounding too negative, cheap and easy don't often go hand in hand, especially when your adding FI to a non FI bike.

What control system do you plan on using for the setup?

I looked into the idea for my ZXR.. using the ignijet 2008 control system and the FI off the CB400 super four.

However, i estimated that by the time i had gotten the box to work with all the relevant sensors and making it fit it was cheaper and easier to install the FCR carbs and SP ignition box / loom.

Since this option doesn't exist for the VFR some kind of FI might be the only way forward..

It's not going to be easy, nor cheap...

Have a read through Parus's thread on fitting EFi to his nc29. It may not be much help though, since you also need to be worried about having two separate banks, and synchronising everything across both banks.

I still think, if the diameter is anywhere near spec, that Triumph bits are a good way to go, since the standard computer is completely reprogrammable. You can do all this with freeware and a £10 diagnostic cable...



Pick up the TB's along with a whole loom and any relevant sensors from a TT600 (or 600 or 650 Daytona or Speed Four) and you could well be on your way. They are even built as 4 separate TB's so no problem making new brackets and re-aligning them to a V4. They are also early-generation Fi, so one injector, one butterfly, no lambda sensor (I think, I know the 955i didn't get one til '02 anyway), nice and simple.



As a bonus you would have stick coils too.

But there you can already see just how many parts you are looking at needing. Computer, loom, stick coils, tank-internal high-pressure fuel pump, custom fuel rail, and and and...

The TB's off most 600cc+ bikes are too big for a 400, and will only compound the issues you have setting them up. You will probably never get big TB's to run well, carbs will seem beautiful after trying to get them to run properly...!

Goinphaster wrote:What I didn't count on was the GSR400 TB's having a primary (PV)[controlled via cable to throttle] and secondary (SV) set of butterfly valves used to modulate the flow of air into the intakes.

Nearly all suzuki 4's use dual throttle butterflys, they adopted it widely acorss many models. Get your hands on this book (invaluable for a project like this), a fantastic read and it explains a bit about the suzuki sensors used for the control of their dual butterfly TB's:

Sounds like an interesting project, do you have pictures of the Suzuki GSR400 Throttle Bodies please?

gonzothegreat wrote:Sounds like an interesting project, do you have pictures of the Suzuki GSR400 Throttle Bodies please?

viewtopic.php?f=28&t=20594

I'm looking at megasquirt for a car but no reason why it can't be used on a bike.

I hate carbs and carb tuning. !

thanks

amorti wrote:

gonzothegreat wrote:Sounds like an interesting project, do you have pictures of the Suzuki GSR400 Throttle Bodies please?

viewtopic.php?f=28&t=20594

I have a spare microsquirt I used on my V8, I might in the future do efi (just for the fun of it).

maderdog_1024 wrote:I'm looking at megasquirt for a car but no reason why it can't be used on a bike.

I hate carbs and carb tuning. !