GSXR 600 ITB/EFI project.

[MegaDan]

I've talked about it in other threads, as I am sure you have seen already. I've been scavenger hunting trying to put my idea together and I now have a few parts to do a little experimentation and information verification. I just want to state right now, this is going to be a slower work in progress as I am still missing many parts to really begin the conversion. My plan is to figure out linkage/brackets and other little details while I have the carbs out to clean them.

Initially I considered using the GL1200 EFI setup, and IMHO, if you want to EFI your bike with ITB's, I would say go that route. Going price for a complete setup seems to run 150-200 bucks, and with minor mods will fit a 1000 or 1100. Most of the work was already done by honda, so relatively it's plug and play.

I decided on the 600 throttle bodies because I am aiming for more performance. These are from a 2001-03 model bike, so each body can be separated, unlike the newer bikes which come in joined pairs. This allows me to try and mount them however I want to. They are a 36mm throttle body, which is relatively big, but I don't believe will be too large to hurt overall performance. I won't know for sure until I run them obviously, but seeing as guys are running carbs with 35mm venturies on IDF's and getting impressive performance gains, I feel these should work out fine.

Here are my throttles. They came complete with everything. The wires to the TPS are damaged, but the injectors are all in excellent shape, and overall very nice condition. This is how they arrived straight out of the box. The only real issue is the wires to the TPS are exposed right at the base of the sensor, but I already priced a second one new for cheap. Between a new TPS and these bodies, my investment so far has been $62.


I also scoured until I found some intake runners from a recycler for $14 for the set. I didn't necessarily have to do this, but I figured it would make things easier if riding season arrives and I'm still not ready for the conversion. This had an added side bonus of letting me test mount one of the throttle bodies to the factory boot on the runner... The results:






They fit perfectly. The groove on the boot actually sits inside the notch on the body perfectly, and it's very snug, so there is no chance of them coming out if they were clamped down. About the only potential issue I see is the fuel rail possibly hitting the frame, but I won't know that for sure until I can actually mount a pair up. The nice

Then that leaves me with one of two ideas. I am kind of torn between the two.
First Idea: Making a simple flange with a tube protruding out to allow a silicon coupler to clamp the throttles to the stock plenum, utilizing the stock air filter.
Second Idea. Clamp on 4 shielded air filters straight to the bodies and/or run a set of trumpets. These bodies are about 2 inches shorter than the carbs to the plenum, so there is plenty of room for stacks/filters. For vacuum signal and idle control I can utilize the 4 air ports on the bottom of the bodies and use or make some sort of vacuum block. In terms of work, this would be simpler... and probably sound pretty epic. Plus, it would give me space to mount the ECU where the OEM air box used to sit.

In either case I still have to figure out the linkage, which each presenting it's own challenge, so that's kind of a wash.

[ericheath]

Two different options you may or may not have considered.

1. Use Mikuni rubber flange adapters. I'll find a pic for you.

2. Use 1200 elbows which are canted a bit more and a little lower, also smaller in diameter. Starts the whole speed of the charge vs volume of the charge debate. In my attempts to use V65 carbs, I used a hole saw to hog out enough rubber to stick the carbs in. They sealed for me. My fuel rails failed on them, otherwise they'd still be on it.

[ericheath]

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[MegaDan]

The factory boots are actually the exact right size to work. I didn't have to do anything special to make these go on, just some muscle effort. Admittedly, these boots are hard as a rock, but the fit is absolutely perfect. The O.D. of the throttle body at the boot end is minutely smaller than the I.D. of the boot (talking very minutely). The I.D. of the body itself at the boot end is nearly the same as the runners I.D at 1.5". The bodies literally mount to the runners like they were designed to fit there. My only real concern is letting them just dangle off the end. If I don't use the plenum, I will work out some type of brace to join both banks together for extra support, or make some sort of bracket to brace them off the engine itself.

I will consider the 1200 runners though, especially if I find the fuel rail ends up being an issue, lower and different orientation would be a good thing. 1mm less diameter may help, and if it's a problem, can be corrected easily.

The only interesting tidbit about running velocity stacks with these is that the rear runners are a about 1/2 to 5/8" longer than the front (rough measure). If I want to tune for a harmonic and the engines peak RPM power to the 3rd harmonic, I would have to get two different sets of stacks about 15mm different in length and run shorter in the rear. There should be enough room for a 75mm stack with room to spare between the front two, which, if my numbers are remotely accurate, is what I will need.

[Sugs]

Subscribed! I will be watching this thread intently!

[irishcarbomb]

interested in seeing your plan for mounting the fuel rails...i'm going to be starting round 2 on my bike soon and have a few ideas floating around.

[MegaDan]

interested in seeing your plan for mounting the fuel rails...i'm going to be starting round 2 on my bike soon and have a few ideas floating around.

Well, fuel rails will have to be made. The spacing on the GSXR is narrower than the carbs on these bikes. If all goes well and the bodies sit far enough back (out or away from the bike) on the 1000 intake runners, then the fuel rail should sit just outside of the frame under the false tank. If not, then they will be hitting it. In that case, if it's just barely touching, I will use a silicon coupler instead of the carb boot. That should take up the gap between the two and give somewhere around 1/4-1/2" more space. If that doesn't work, then the 1200 runners will be considered because of the change in angle they would provide. I could also try inverting the bodies and having the fuel rails run underneath (if I have the room).

[Toehead]

Looking good!

[WileCyot]

Out of curiosity, why go ITB? From my calculations, a single 38.5mm throttle body will be plenty large enough for street use or 42mm for a performance application on these bikes. My plan was to use forced induction using a CBR300R throttle body which is a 38mm diameter. Eventually, I would use the single throttle body mounted injector for meth injection if everything worked well.

[MegaDan]

Out of curiosity, why go ITB? From my calculations, a single 38.5mm throttle body will be plenty large enough for street use or 42mm for a performance application on these bikes. My plan was to use forced induction using a CBR300R throttle body which is a 38mm diameter. Eventually, I would use the single throttle body mounted injector for meth injection if everything worked well.

The difference in throttle size is not a direct correlation. Do the math for a single 250cc 1cyl engine (aka 1/4 of our engines) and you will find that the diameter of that single throttle will be around 22mm. That said, basic calcuators can only tell you so much, and are usually super conservative. The factory carbs have a much larger venturi than that theoretical throttle body calculation. The same principal applies to most flow through a tube(s) like exhaust systems. A single 3" I.D exhaust on the same vehicle will roughly flow the same as two pipes a bit smaller than 2.5".

the 40mm IDF carbs run by a few guys on here are 40mm bodies with a 35mm venturi, and they picked up power across the board, and with a more direct airflow path than what I am looking to have. They also seem to have great throttle response. Those same calculations also tell me a Toyota 3.0L I-6 and 4.0L V8 should have 28mm bodies, yet in those two examples I put together, 42-48mm bodies were the best match.

Why go ITB? Performance. It's that simple. Harmonics tuning is much easier on this setup. Second reason - wicked intake noise.

[gltriker]

quote: " If I want to tune for a harmonic and the engines peak RPM power to the 3rd harmonic, I would have to get two different sets of stacks about 15mm different in length and run shorter in the rear."

This has gone beyond my comprehension.
Please explain what tuning to "a harmonic" means.

[MegaDan]

quote: " If I want to tune for a harmonic and the engines peak RPM power to the 3rd harmonic, I would have to get two different sets of stacks about 15mm different in length and run shorter in the rear."

This has gone beyond my comprehension.
Please explain what tuning to "a harmonic" means.

Think of the intake tract like a musical instrument. There are pulses of compressed air caused by the intake valve closing that travel back up the intake. Without going into a long winded explanation, the simple physics are, the pressure wave traveling back up hit's a chamber (or open area) of static air, and creates a reverse wave back down the intake (weaker than the initial like a bouncy ball). The distance traveled out and back to the valve face is your intake harmonic. The idea is to tune the intake length to peak power RPM, or torque depending on desired effect, so that the pressure wave returns to the intake valve as it opens. This increases the volumetric efficiency of the engine by "ramming" more air in than would normally occur.

The terms 1st, 2nd, 3rd, etc. are in relation to how many times that wave travels up and back again before the intake opens. 3rd harmonic means that wave has gone valve to runner end to valve again 3 times. Most production engines tend to tune to the 3rd or 4th harmonic, if the engineers decided to do so, due to packaging. The reason why is the length of the intake pipe. The only drawback is, each progressive harmonic wave is weaker, so the effect is lessened.

The basic math is just figuring out how many degrees the engine must turn between the intake valve closing and then opening again, how much time it takes for it to travel said degrees via engine RPM, then calculating how far said wave will travel at the speed of sound in that time, and then halving it to allow the wave to travel back as it "reflects" off of the open air/plenum end.

Example: My rough math for my 75 engine with a 235 degree total cam duration and 1.5" intake diameter and peak power in my calculation at 7500rpm would put the ideal runner length at 43.88 inches long... a bit unrealistic lol. for each progressive harmonic that number decreases, so second harmonic length is 21.56, 3rd is 14", 4th is 10. etc. It's not quite half each time due to other factors, but as you can see the 3rd and 4th are the most commonly used because those lengths are plenty feasible in most or all applications. If you accurately measured from the intake valve to the open end of the plenum on the stock intake and carbs on a GL1000, you might notice that the runner length is right about 13" long, That put's it within close range of my rough math, and Honda probably had much more accurate math than I did lol

[gltriker]

OK.

[WileCyot]

The difference in throttle size is not a direct correlation. Do the math for a single 250cc 1cyl engine (aka 1/4 of our engines) and you will find that the diameter of that single throttle will be around 22mm. That said, basic calcuators can only tell you so much, and are usually super conservative. The factory carbs have a much larger venturi than that theoretical throttle body calculation. The same principal applies to most flow through a tube(s) like exhaust systems. A single 3" I.D exhaust on the same vehicle will roughly flow the same as two pipes a bit smaller than 2.5".

the 40mm IDF carbs run by a few guys on here are 40mm bodies with a 35mm venturi, and they picked up power across the board, and with a more direct airflow path than what I am looking to have. They also seem to have great throttle response. Those same calculations also tell me a Toyota 3.0L I-6 and 4.0L V8 should have 28mm bodies, yet in those two examples I put together, 42-48mm bodies were the best match.

Why go ITB? Performance. It's that simple. Harmonics tuning is much easier on this setup. Second reason - wicked intake noise.

For the 250cc engine (I'll use a CBR250R) that makes peak power at 8500rpm, I ge that it needs a 19.4mm throttle body for street and 22.3mm throttle body for performance applications.

The Toyota 3.0L (2JZ-GTE) in stock trim made 321hp @ 5600rpm. Based on displacement and peak power rpm, it needs a 54.6mm throttle body for street and 62.8mm throttle body for performance. Now these calculations are based around naturally aspirated engines so this is a tad misleading but the stock throttle body started at 71mm and tapered down to 65mm at the butterfly.

The Toyota 4.0L V8 you're referencing I will assume to be the 1UZ-FE. It made peak power (261hp) at 5100 rpm. Based on my calculations, it needs a 60.1mm throttle body for street and 69.2mm throttle body for performance. It came stock with a 60mm throttle body.

I don't mean to toot my own horn here....

[WileCyot]

And it's not my math...to clarify

http://www.hipermath.com/math_center/ra ... lculations