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The definitive Katana EFI swap thread

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  • TheSteve
    started a topic The definitive Katana EFI swap thread

    The definitive Katana EFI swap thread

    I'm sure everyones seen the original thread by now ( but I wanted to make a much shorter version of the swap that had all of the tech and pics but without the discussion of various theories and ideas. This thread is clearly not the only way to do it, and probably isn't even the best way. But, my bike does run with this setup and once tuned correctly should offer many benefits over carbs. I'm not going to go into detail as to what the benefits are, as most of it was discussed in the aforementioned thread. Perhaps this could be stickied if it's in depth enough.

    Lets start with the parts list. You'll need:

    01-03 GSXR 600/750 throttle bodies. I recommend the 600s as theyre smaller and easier to fit onto a Katana engine. Make sure the ones you get come with the injectors and any accessories you might want. The 01-02 GSXR 1000 throttle bodies may also fit, but note that they changed to a new style in 2003.

    Fuel pump. Must deliver at least 45psi. Aim for 45-60psi operating range. I went with an inline fuel pump, but if you're crafty you might be able to get an in-tank setup going, which makes for a cleaner look.

    Fuel pressure regulator. Any regulator off any EFI vehicle should work as long as its set at 43-45psi. Note that many GM vehicles in the 80s and 90s use a TBI setup that runs at 20psi. You CANNOT use much of anything from these fueling systems.

    ***SEE NOTES***Megasquirt system. The exact variant isnt critical for a basic running engine, but the different versions allow for different features. There are two CPUs available (MS1 and MS2) and two boards (PCB 2.2 and 3.0). The CPU holds little relevance on an engine as simple as this. MS2 has native spark control, but MS1 can be flashed with custom firmware to do the same thing. The PCB is much more critical on this application. The Katana uses a VR sensor for the signal generator, and the 2.2 board does NOT have the capability to handle this signal without adding external parts. The 3.0 makes the install nice and clean. I have an MS1 2.2, but I recommend the MS1 3.0. Theres also the Microsquirt which is smaller and similar to a MS2 3.0. I'm not familiar with this route so I can't answer many questions about it. EDIT: I now recommend the MS1 2.2 combo as the VR decoder is no longer needed

    Automotive fuel filter. Fuel injectors are clogged very easily and will not tolerate any dirt. These are cheap at any auto parts store.

    Intake Air Temperature (IAT) sensor. This tells the MS unit the temp of the air for calculating air density. The recommended part is Duralast SU109 from Autozone. Cheap and effective. You may also use the same sensor for your oil temp sensor, mounted somewhere on the engine block.

    Fuel hose. 5/16" for the most part. If its a pressurized line you MUST use EFI rated hose. Its more expensive but won't rupture. For return and feed hoses you can use standard fuel hose.

    Oxygen sensor. I HIGHLY HIGHLY recommend a wideband sensor. A wideband tells you the exact AFR you're running at any given time. A narrowband only tells you rich or lean and is not very helpful and CANNOT be used to tune the high end or you'll end up melting pistons. I recommend the Innovate LC-1. You don't need the gauge, the MS handles it.

    Optional parts:

    Katana 750 intake boots. These are a few MM larger than the 600 boots. Either work, but the 600 boots need to be bored out with a dremel. Its easy to do, I wouldn't bother with the 750 parts.

    Metal hose barbs. If you don't use the stock petcock (I didn't) youll need to make a hose adapter. You'll probably need to make one anyway for a return, but you might be able to get around that.

    ***SEE NOTES***GM 4 pin HEI module. Did you buy a PCB 3.0? Then ignore this part. This is needed by the 2.2 board to decode the VR signal from the bike and output a clean signal to the MS. Duralast part number DR100 from Autozone. This is no longer needed.

    Aftermarket fuel rail. If you really really dont want to make this, then you can buy one drilled and cut to your liking. The only place I know of to get one from is ross machine racing. They have a website. I'd also check

    Special tools:

    Welder. Makes things easier, but I'm sure theres ways around using one if you don't have one.

    Grinder. To lengthen the fuel rail youll need to cut it in half and grind it smooth. A bench grinder is the best tool for this job, but I did it with a steady hand and a handheld angle grinder.

    Laptop. It doesnt have to be a good one, in fact only the old ones have serial ports on them (to talk with the MS). You can get a USB-serial adapter if you need. The laptop doesn't need to be anything special as long as it can run windows.

    Carb syncer. I use a Morgan Carbtune and it took 5 minutes to get it perfect. These may not be carbs, but they need to be synced all the same.

    Basic electrical tools. You're going to need to solder here, so soldering equipment is a must. A digital multimeter is a nice tool to have as well.

    That should be it for the shopping list. Lets begin!

    You can see the comparison between the TBs and the carbs here. I've jumped the gun and already removed the secondary butterflies before this pic was taken. You MUST remove the secondaries if you want any power or drivability. This assembly commonly fails on GSXRs, so if you're careful in removing them you can probably resell them to the GSXR crowd. Heres a closeup of the secondary shaft:

    Once you start removing them it's pretty easy. The only things on this entire assembly you need are the bodies themselves, the injectors, the primary throttle plates, and the throttle linkage so don't be shy in tearing them down.

    Here is one of the main reasons this has not been done before:

    With cylinder 1 lined up perfectly between the carbs and TBs, notice the port spacing difference. Cyl 2 is off, 3 is way off, and 4 is a little off. Fortunately this generation GSXR has modular throttle bodies: they all come apart with ease. Its just a matter of altering the spacing to make them fit.

    For reference, here is a pic of the overall height difference:

    You'll have to use your imagination a little bit as my carbs are not completely together.

    So now how do we mate these up to the engine? The stock intake boots are made of soft rubber, and even the stock 600 boots will fit over the TBs without deforming:

    This was a very tight fit, and I highly doubt you'll be able to fit the TBs into the boots while the boots are bolted to the motor. Pressing it in took much force. What I decided to do to make it workable (due to the Katana frame, all 4 throttles MUST be installed at once or you won't be able to fit the bolts in) was pack some paper towels down the intake ports and slowly grind down the inside of the boots with a dremel. It makes a mess, and you don't want this junk in your motor. Theres a small rib in the rubber, if you grind that flush with the rest of the boot it should fit alright. I did flush and then another millimeter or two over that. Dont overdo it or youll have vacuum leaks. After grinding but BEFORE removing the paper towels, blow the ports out. An air compressor works well here, but whatever you can do should be fine. The end result of this step is pleasing, as you now have something to show for your troubles:

    Well, that wasn't so hard. But what to do about the gap from spacing them out?

    First and foremost, you'll need some washers to go between the center two throttles. Without them theyll flex under twisting the throttle and youll never ever get them to hold sync. At this point I'd like to mention that my throttle bodies are actually installed upside down! With them oriented correctly, the fuel rail is on the bottom of the throttles. This would be a good thing normally as air wouldn't get stuck down there. But on a Katana, the fuel rail hits the alternator and wont fit. Having them upside down doesnt hurt anything but does bring up a few issues that we'll deal with later. With the fuel rail on top, it clears the tank by just enough:

    Enough gap for safety, but close enough to be a lucky fit. This is on a Pre, hopefully the 98+ tank doesnt extend any lower. Your petcock is going to hit the rail by just a little bit. You can probably dent the bottom of the tank in a cm or two to clearance it. My petcock was shot so I made my own out of some steel, a hose barb, and some JBweld:

    But back to the other problem with the throttle spacing: the throttle linkage. As you saw in the picture, its not even close to being long enough. The length of the arm has to be extended by about 8mm. I was able to weld a piece of metal to the end of the arm to bridge the gap. Try to make it flat if you can, but if not perfect you'll take care of it while syncing anyway.

    That weld was just a tack for fitment. I don't have a pic of the finished weld, but the positioning didn't change from that picture. Now that you've lengthened the linkage its time for the 2nd half of the job: the fuel rail. You've got options again. Buy fuel rail stock from an aftermarket supplier, build your own rail from a piece of square metal tube, or modify the GSXR part. I was weary of doing this at first but was soon reminded that the rail was worthless to me anyway since it didnt fit. I started with this:

    Cut it in half:

    No chance in hell it'll seal with those casting ridges, so they've gotta go:

    Both sides ground smooth:

    And then test fitted to the motor:

    And bridged with heater hose of a forgotten diameter:

    Now hows that for a stupid idea that ended up working great? Doesn't leak a drop! Dont worry about the pressure rating of that hose. The gap is too short to allow for any swelling. Next up is the throttle cable. Remember how I said the throttle bodies are upside down? Heres one of those issues I mentioned:

    This pic is looking at cylinder 4 from the seat area. Looking closely youll see the throttle cable mounts are now on bottom. I'm not sure how to advise you on this one if you don't have access to a welder, but I'll show you my solution to maybe spark an idea:

    I welded the adjuster nut to the throttle stop on the cable pulley assembly. This allowed the cable to come in from the top as well as have 100% range of motion. The GSXR must have a very long cable, as you would need about 4-5 inches of exposed cable to use this damn thing. If you cant weld, maybe try buying a GSXR cable. You might be able to find a way to make this work easier.

    If you've made it this far, congratulations! All of the major puzzle pieces are now in place. All thats left is the fuel system and wiring harness. Lets go over the fuel system first.

    When I started this I had the following diagram in my head knowing that it had only a 40% chance of success:

    I built this, and as expected, after 10 minutes or so the fuel-cooled fuel pump had heated itself and the metal fuel filter to the point of burning your hand. The gas was evaporating in the lines and bleeding the air out of there took forever each time it happened. This diagram was always known to be the "correct" way that had a 95% chance of success:

    So then why didnt I do that in the first place? Lazyness. I didnt want to drill a hole in my gas tank. What I ended up doing was drilling the return in the metal plate for the fuel sender. Worked perfectly and didnt change the tank from stock. Unfortunately I don't have a pic of this one. It looked the same as the first, but with the hole drilled in the sender rather than a new plate. The reason this one works is that the heated fuel is sent back to the tank to cool off for several minutes before recirculating. With the other setup it repumped the same gas over and over again.

    The other concern for having the throttles upside down is air bubbles. Its a returnless system, so bubbles never get pushed out. The fuel rail is the high point of the system so it collects a lot of air. I changed it up from my earlier pic to have the T level with the valve cover and the regulator on top of the valve cover. The high point is now the FPR instead of the rail, so air is simply pushed back into the tank and dissipated. Pics to come soon, I was working fast and didnt take any work-in-progress shots.

    The last thing I'll cover in this chapter is the misc welding. On a pre98, there is no real tray to mount the MS unit. But I found it fits perfectly under the passenger seat. I welded some steel up to form a flat tray and bolted the MS down. I recommend making a watertight box for the MS (not microsquirt though, its watertight) if you dont live in the hell that is Arizona. It never rains here, so I didnt bother.

    Lastly you'll need to weld in a bung for the O2 sensor. All widebands are heated sensors, so distance from the header isnt critical, but closer is better. I placed mine directly behind the oil pan, tilting slightly upward to keep it out of harms way.

    The bung used comes with the Innovate LC-1 I mentioned. Its a great little package for less than $200. It's 4am and I'm tired of typing so I'll cover the wiring in the next day or so. Then following that, chapter 3 will be about tuning. That has to wait until I'm actually finished tuning mine though. Expect posted fuel maps within a week and a half at the very latest.

    EDIT: After much experimenting, I have found that while the HEI module works, I do NOT recommend it. Theres a better way, which I'll cover in the wiring section. You can omit the 3.0 board and the HEI module as a result. Note that the 3.0 board still works fine, but its no longer required.
    Last edited by TheSteve; 11-29-2008, 04:02 AM.

  • TheSteve
    Very nice, sounds like it'll be a fun project. I've been wondering how the GSXF throttles would work since it was first mentioned, it's good to see that someones actually going to see it through.

    I haven't done a whole lot with projects lately, but I've been trying to resurrect some of them. I still have my zx6r which has been great in every way, but I've pretty much left it stock other than sprocket changes and easy stuff like that. Sold my old Toyota truck which had a megasquirted 2RZ engine which ran excellent because I needed space and never really took it off road anymore. I'm pretty sure I mentioned my old Nissan 240sx at one point or another as well. I still have that but I sold the RB25 since it was being a pain and eventually picked up another KA24DE, which I turboed. I made the mistake of trusting someone else's MS timing map and grenaded a piston back in December or January. I rebuilt the engine myself somewhere between February and April, got it all running again but now it won't pass emissions. Honestly the car was left to sit from April till last week; life has been busy this year. I diagnosed the issue to an intermittently leaking injector and just ordered a new set of 75lb injectors for it last night. Hopefully it'll be able to pass emissions and run properly now. Couple months ago I bought an old F150, I was planning on leaving it stock but the factory engine management is really poorly done, causing the throttle to hang like crazy which is annoying during upshifts and it also lags when first pressing the gas. It's no wonder most of these trucks have automatic transmissions; its miserable to drive in traffic with that much throttle lag. So that might get an MS some day, maybe.

    I finally quit my old job, got a better one and hated it, quit that one, and am now working at least 50 hrs a week at a job that I enjoy. Also bought a house which is a project in itself. Been a real busy year for me.

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  • cintidude04
    Wow, long time no see TheSteve. How have you been? Any new projects lately?

    So far just acquiring parts and figuring how best to fit them to the Kat. Just ordered my LC-1 lamda controller the other night, Found that the TPS unit on the TB's has a built in IAT sensor I should be able to utilize. Pretty much all that is left is deciding which version of megasquirt to use, Picking up a full exhaust and welding the bung to it ( think I/ve decided on the D&D full exhaust and swap the can out for my Scorpion), and figuring out how best to fasten the cylinder temp gauge then on to tuning. Well, after I rebuild the engine of course.
    Still quite a ways off. But hoping here soon to have the funds to get most of the stuff done to finish the motor at least.
    Last edited by cintidude04; 10-31-2011, 09:29 AM.

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  • TheSteve
    Wow how did I miss your update cintidude04? Thats great work! How far along are you with your swap? For some reason I never got the notification in April that this had been updated.

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  • cintidude04
    The stock petcock will filter large particles out and will flow into the fuel pump then to the in line filter, then to the fuel rail via the fuel pressure regulator.

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  • steves
    If you use the stock petcock, then how is the fuel getting pressurized?

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  • cintidude04
    GSX650F Throttlebodies for EFI conversion.

    Ok here's for you others who have requested it. How to fit completely stock GSXF650 TB's on a Kat.
    Hope this helps.

    First off is the diagram of which boot goes where. The boots I used were 1998 750 Kat intake boots. More than likely possible with pre boots as well, but I have not tried. The part #'s I have posted are from the bikebandit fiche.

    I recommend using the GSXF650 boot clamps for the ease of getting rid of the old screw style (the new ones use a hex bolt and cover 2 boots).
    Also the oil lines will now be a very tight fit but will work. Personally I will be replacing the lines altogether with a set of HEL lines and adapters.

    The next possible fitment issue may come from the secondary butterfly motor being in the way of the alternator. Now I don't know if this will actually be an issue as I do not have my alternator hooked up atm. To get around this you could remove the motor entirely since you will not be using the 2ndary butterflys. Personally I just unplugged the wiring connection at the bottom, since it looked like that would be the only problem point.. I figure the less I have to take off the better.

    That should be it for fitment of the GSXF650 throttle bodies in stock form.
    I did however notice that each body has it looks like 2 vacuum ports. if this is true that would mean we can likely use a stock post petcock and still have the other vacuum line for the MAP sensor. If some one has already done research on these throttle bodies and can either confirm or deny this please speak up. .

    Last edited by cintidude04; 10-31-2011, 08:58 AM. Reason: TB Breakthrough

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  • TheSteve

    My old katana is back and being parted out. I'm selling nearly all the EFI parts that were featured in this thread. See for details.

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  • Kat750_1126
    Katata EFI Conversion

    Hey Im new here so I cant send you an E-mail Thesteve. But Mine is Again thanks for the great info and insperation to takle this on my own .

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  • TheSteve
    Oh wow, forgot about this thread lol.

    To answer your questions:
    Send me your email address and I'll send you the latest tune. I'll change the reqfuel value for a 750. The majority of the tune may be a little off (especially for cranking I think) because of differences in the bore, stroke, and cam (which make the differences in VE) but it should be close enough to get you started by just having the displacement variable increased.

    The HEI setup is long gone but it still does work if you'd rather pursue that route. I'm still using the diode/pull up resistor and it's performed flawlessly since installed.

    A few updates to my garage:

    The Katana is still running strong with its new owner.

    I finished the MS conversion on the GSXR. Rode it around the block a few times (ran very well considering it was untuned. Engine was much easier to get running than the old oil cooled ones.

    The GSXR developed some problems starting where the engine would lock up HARD with a tremendously loud BANG when cranking. I pulled apart the starter motor, its gears, and the starter clutch and all looked fine. The bike would push start fine as well.

    Decided I didnt want to mess with it, swapped the carbs back on (anyone need a readymade conversion kit?) and sold the bike.

    Two weeks later I bought an 07 ZX-6R, factory fuel injected of course. Not really any chance of megasquirting this (not that I'd need to, but fun to speculate) because of the way the ECU talks to the gauge cluster. No longer is it a wire for each function, its now a ONE wire digital signal. No chance in hell of the MS convincing that to work. Without that wire, I lose tach, gear postion switch, temp gauge, check engine light, and I think oil pressure. Basically it'd be a very large rewire of the majority of the bike. So this one is staying mostly stock unless I need to make adjustments in which case I'll buy a powercommander..

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  • Kat750_1126
    Hey guys. Im doing the same conversion from carbs. The only problem I have is the tuning Im not too confident about that one. Steve is there any way I can use your files just so I have something to start off with. I have a 750 not sure if yours is a 600? and did you end up sticking with droping the (GM 4 pin HEI module) for the diode/resistor set up.

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  • TheSteve
    Got the temp sensors fitted. The same Duralast SU109 fits the fan switch spot in the radiator just barely. The stock hole is a M18 x 1.5 (same as an O2 sensor or automotive spark plug) and the sensor is a 3/8 NPT. Theyre very close to the same. Since no CTS was ever made in a M18 it'll have to do for now. If it leaks I did find one company that makes an adapter from M18 x 1.5 to 1/8 NPT which is used for many aftermarket and OEM temp sensors.

    The IAT I went with this time is the Duralast SU107 which is the same size, shape, and resistance of the 109. The difference is that rather than being encased completely in brass, the sensor bulb is suspended in a protective cage with open air all around it. This allows less heatsoak and faster response. The intake air temp sensor's home is in the GSXR's spacious airbox.

    All the wiring is done. This is moving along quickly. Fuel pump's JB weld return bung is currently drying. It should be done by the time I'm off work tonight and I'll swap that over and get the fuel lines situated. I need to find a spot to mount the pressure regulator.

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  • TheSteve
    Ok. Took the bike apart. Throttles fit nicely, little boring of the rubber boots was all it took. They fit great. Got the harness made, tomorrow I'll splice it into the TPS, signal generator, power, and ground. May also try to fit a temp sensor in the radiator. Tomorrow I may try to swap fuel pumps as well.

    Everything seems to fit well. Throttle cables seem to be the right length though I havent connected them, airbox fits but the boots are too big, throttles are perfect as far as spacing and height go, etc.

    Only concerning issue right now is the TPS. The TPS's between this and stock are different resistances. The TPS also feeds into the CDI on the GSXR for ignition timing, so the difference may kill my ignition advance. I think it may be ok in that theyre both 0v-5v voltage dividers so it should show relatively the same value at the same throttle position. Guess I'll have to try it and find out since the TPS's are different sizes and cannot interchange.

    Actually one more concern. I dont know if that temp sensor will fit or not. Thats kind of a big deal. I'll figure something out.

    Edit. Just realized I completely repeated myself from my last post about the TPS. I should probably read my previous posts before updating. And my order of operations was abandoned due to me having nothing to do today.

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  • TheSteve
    May have a serious setback here. I pulled the tank off to run a few wires and noticed that the thermostat housing on the GSXR sticks out much higher up on the engine than I thought. It looks like its going to get in the way of the fuel rail and injector #4. It's too close to eyeball it, I need to actually pull the carbs off to see if its still feasible to use these throttles. Theres miles of clearance everywhere but that damn thermostat housing. Hopefully it'll fit.

    Forgot to mention, I did actually get some work done tonight. I pulled off the exhaust and started to mount the O2 bung. Pain in the *** to try and drill that hole. I think I'll cut it out with an angle grinder this time. Also got a 4 gauge chassis ground going straight to the battery. I wonder if this will stop the flickering dash lights. I then burned my hand after touching some freshly welded metal. The O2 bung left a nice O shaped burn on my palm after the exhaust started to slip from my hands and I instinctively went to catch it.
    Last edited by TheSteve; 08-25-2009, 03:26 AM. Reason: Automerged Doublepost

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  • spatula6554
    @ TheSteve

    Amazing work!! Meticulously detailed and well put together. I just spent 3 hours reading from the very first post to this current one, I couldn't stop.

    I have been considering this mod for my bike for a bit now; all of your information and experimentation will be a great help!

    It will take some math and planning in order to collect the right parts for a 1993 GSX1100FP, but I think it is possible.

    Thanks again, I will certainly be keeping a close eye on these projects!

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