[philwecksr]

Just busted out my calipers and new throttle bodies... Measurements look like this, if you want any more let me know I'm on my way to the garage to see what it looks like when attempting to mount...

I.D. where the throttle bodies meet the intake boots: 37.5mm
O.D. at the same place: 43.8mm
Distance from about the center of one body to about the center of the next is about 80mm...
Length of the assembly (length the air flows): 82.9mm

[whitecl0ver]

NOt seeing the point in all this...just buy a FI bike if you want fi

[philwecksr]

NOt seeing the point in all this...just buy a FI bike if you want fi

Fair enough. I've always been infatuated with the Kat. The body style, the riding position, etc. etc. I finally got one after pining over them for a couple years and I'm not ready to part with it.

That being said, I hate carbs. I hate the uncertainty in my mixture, I hate the inaccurate methods of adjusting them, I hate having such a hard time starting the bike in the cold. My one complaint with the kat at this point in time is that it is carb'd.

Seeing an opportunity to do something fairly unique (moreso than huggers, or undertails, or a slip on) and looking for a project to do, I decided to explore here. I'm looking forward to countless hours spent trying to optimize my mixture at various RPM. I'm looking forward even more to not having to take my tank off and root around in my carbs, but rather plug in my laptop and play a game...

Also, this whole project is gonna run $500 plus my own time to complete, I'll likely spend that getting what I want out of an FI bike by upgrading...

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I just got done trying to fit the throttle bodies to the bike. As Sin said the bodies are a little more compact that the carbs, but not by the original notion. It would seem the 1&2 carbs and the 3&4 carbs are the right distance apart, but 2&3 are about 5mm too far apart for a proper fit.

In addition to the carbs being too far apart, they are not even going to pretend to go into the intake boots. Each throttle body is about 6mm larger than the matching intake boot hole. I'm going to look at kat750 and bandit 1200 boots that might fix this.

Where the bodies meet the air box is a similar problem but in the other direction. The rubber boots on the air box are MUCH bigger than the throttle bodies. I was thinking about running pods or other alternative filter method anyway so I'm not sure I'm upset about this...

Finally, I have concern about the height of the entire assembly. I'm not sure if there is going to be enough clearance between the tank and the fuel rail, so we'll have to wait and deal with that when it gets here.

[grebstev]

hmmm seems like you have taken on a huge project. look forward to hearing the outcome. i like the idea

[TheSteve]

Is there any chance of widening the intake boots just enough to allow a snug fit? Theyre just rubber from what I can tell, just stiff due to age. Or is there not enough material to cut away without being too flimsy? I wonder if the GSXR boots fit the Kat engine. I wouldnt worry too much about the airbox. With EFI you can easily run the pods with no ill effects, though you might need to run in the Prime position on the petcock since you dont really have any good sources of vacuum. Not sure.

The reason I'm doing FI is because I also really hate carbs. I don't know a whole lot about troubleshooting them, tuning them, etc. With fuel injection I can immediately pinpoint the problem, if there is one. Theyre also more reliable setups; every third post on here is "Help me fix my carbs!" And, lastly, with a wideband O2 sensor which I have from the other two vehicles I can accurately set the exact AFR I want to run at for ANY load at ANY rpm. So it allows for more power but greater gas mileage at the same time. And lastly, I'm a nerd. This is what we do.

That being said, $500 sounds a bit steep. My proposed cost list is:
GSXR TB: $46 shipped from ebay
Megasquirt 1 kit: $140
Inline fuel pump: ~$100
This is a little cheaper than some because I already have stuff like a wideband and I can assemble the MS unit myself, saving probably 80 bucks.

I dunno, to me the benefits of a modern EFI system alone are worth the cost and labor. The cool points are just a side benefit.
Oh, and the reason I didnt buy an FI bike to start? This one was cheaper

[pistolpete]

search the internet for other examples, alot of ujms have been MS'd

[philwecksr]

Is there any chance of widening the intake boots just enough to allow a snug fit? Theyre just rubber from what I can tell, just stiff due to age. Or is there not enough material to cut away without being too flimsy? I wonder if the GSXR boots fit the Kat engine. I wouldnt worry too much about the airbox. With EFI you can easily run the pods with no ill effects, though you might need to run in the Prime position on the petcock since you dont really have any good sources of vacuum. Not sure.

The reason I'm doing FI is because I also really hate carbs. I don't know a whole lot about troubleshooting them, tuning them, etc. With fuel injection I can immediately pinpoint the problem, if there is one. Theyre also more reliable setups; every third post on here is "Help me fix my carbs!" And, lastly, with a wideband O2 sensor which I have from the other two vehicles I can accurately set the exact AFR I want to run at for ANY load at ANY rpm. So it allows for more power but greater gas mileage at the same time. And lastly, I'm a nerd. This is what we do.

That being said, $500 sounds a bit steep. My proposed cost list is:
GSXR TB: $46 shipped from ebay
Megasquirt 1 kit: $140
Inline fuel pump: ~$100
This is a little cheaper than some because I already have stuff like a wideband and I can assemble the MS unit myself, saving probably 80 bucks.

I dunno, to me the benefits of a modern EFI system alone are worth the cost and labor. The cool points are just a side benefit.
Oh, and the reason I didnt buy an FI bike to start? This one was cheaper

Good to know somebody is still on board. Check this out when you have a minute:

http://www.puresimplicity.net/~hemi/vehicles/gs-efi.html

Some guy doing an EFI conversion for an old GS. His biggest problem so far is the center to center spacing from one body to the next. His is worse than ours though. His spacings are 77-93-77, where as near as I can tell we have 80-90(85)-80. The throttle bodies are an 80-80-80. I'll try and cram an intake boot over it tomorrow or sunday.

The guy on that site used the same throttle bodies we are but his boots are for 36mm carbs (i.e. kat 750 or bandit 1200). He said it was a very snug fit to get them in, so I think the added 3mm difference is going to be too much to overcome, but I'll give it a whirl.

The next step is to reduce the throttle body as a whole to its individual bodies. Then those will be put into the boots on the engine and I'll measure the difference between the bodies and make up some spacers.

As for my price tag, yeah, thats kind of a worst case scenario. I plan on using the Megasquirt 2 or the Microsquirt instead of the Megasquirt 1. I want the added features and processing power of the newer chip. That'll run me 250 or so if I build it myself (which I will). The throttle bodies came in at 150. I need to buy a wide band sensor. I need a fuel pump. I guess 500 is actually an optimistic guess now that I look at it again...

As far as putting it on prime I'm going to try and modify the petcock (modify=remove ) so that it just flows freely into the fuel pump.

This project is actually moving along much smoother than I was anticipating. I'll probably end up running pods like you said, shouldn't be an issue with as much variability in fuel delivery as I'll have...

[TheSteve]

Hmm, what extra features do you need? Spark control? You can probably run one of the extra firmware variants to get that on MS1. The kat engine is simple enough that I think MS1 even with the base code is sufficient unless you want spark control. Do you remember offhand what the max RPM MS1 allows for?

Another option, somewhat bulkier, would be to have pipes going from the kat's boots to the TBs, so the pipes could be slightly angled instead of modifying the TB. This will make up for the spacing difference as well as the diameter since you could use radiator hose and clamps on the other end to secure it. This isnt ideal, but without the TB unit in my hands I cant tell what the best way to fit it is gonna be. Just throwing ideas out there.

[philwecksr]

I would like to run spark control off the MS2 eventually. It also allows for a more detailed fuel map. Also, I'm not 100% sure I'm going to get rid of the Dual Throttle Valve system yet. I'd like to read into how it works some more and maybe run the electronic servo off the MS2 as well. Just flip it open to allow full flow for now and tune it later...

[TheSteve]

From what I've read, at least the early revisions of the dual butterfly were to offest poor throttle response. You'd snap the throttle open and the engine would cough and sputter until it added in the extra fuel. Id think with MS's complex accel enrichment settings you could overcome that. Unless it really is to increase air velocity at low RPM in which case it could be useful. But I'm not sure MS can do something like that; I know people haven't had much luck with things like VTEC.

[The CyberPoet]

Go look up the post from our mad modding aussie who added turbo to his Kat. As part of the first step, he fuel-injected the bike. After testing, he found that using a single injector at the start of the airbox area and feeding that to all four intake ports was the simplest solution, helped greatly reduce complexity, and let him easily program a viable fuel-map with a MegaSquirt system... So someone on our board has done it before

Cheers,
=-= The CyberPoet

[philwecksr]

From what I've read, at least the early revisions of the dual butterfly were to offest poor throttle response. You'd snap the throttle open and the engine would cough and sputter until it added in the extra fuel. Id think with MS's complex accel enrichment settings you could overcome that. Unless it really is to increase air velocity at low RPM in which case it could be useful. But I'm not sure MS can do something like that; I know people haven't had much luck with things like VTEC.

I think the MS2 would be able to control it. Its just an electronic servo, so if I can output a voltage from the MS2 to the servo I'd be able to control how open/closed it is...

[TheSteve]

Any updates? I haven't gotten my TBs yet and was wondering if you figured out the spacing problem yet?

[philwecksr]

Haven't figured out the spacing yet. I did take an intake boot off the bike and tried to fit it over the TBs. Not gonna happen. the pre and post 750's both used 36mm carbs and i've got a buddy with a 750 engine not on the bike right now so I'm going to try and fit one of his boots on the TB's. I'll have to order new boots then if those work. I've been trying to sources boots from a 750 or bandit 1200, but haven't found any used yet. I might have to buy new... grrrr....

Projects kinda on hold til I have boots of the right size....

[TheSteve]

I just did some measuring, and the stock 600 boots look like they could fit if you bore them out by 4.1mm, which is almost nothing. My other thought was that the Kat 750 (or more commonly the 88-92 GSXR 750) boot should be almost a perfect fit. I've got a set of 31mm and 33mm carbs, and assuming the ratios of taper and wall thickness are the same as the 36mm it should be about ideal. I have 2 sets of boots from a 33mm carb'd kat 600 so I'm gonna try marking a template onto them and gently boring them out with a dremel. Figure even if I screw a couple up I have spares.

So now I need to figure out the spacing which might need to wait until I have the GSXR parts in hand.