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> ITB project, Honda VFR 800 ITBs
kevin311
post Aug 17 2012, 11:25 AM
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I've been running Megasquirt II for a while now on my 71 1.7 with the stock D-jet components and it has been running well. But everything is looking tired in the engine bay and I am planning on taking out the engine to clean everything up and install SS fuel lines.

Then I remembered seeing a video youtube with an australian guy reviewing his 914 and he mentioned having GSXR ITBs on his car. Sounds like a fun project to me so I started researching and think I have found an even better solution.

The throttle bodies I found are from a 2001 Honda VFR800. The bike is a V4 so the TBs and fuel rails are already split into pairs, and have a linkage that connects both. They have 37mm throats, and came with the throttle position sensor, fuel pressure regulator , injectors and and all the wiring and connectors. Also the brackets on the sides already have a tab for throttle cable.

The injectors are high impedance so I wont have to run PWM on Megasquirt anymore and hopefully can get an even finer tune.
I'm also thinking about switching the PCs for 96mm, but I think that will wait until later, but you never know this started out as an engine cleaning...

The only things I need to figure out are the flow rate of the injectors, where I'm going to hook up the IAT sensor, and will need to build a vacuum plenum. Also these injectors run at 36 psi, can the stock fuel pump handle that or do I need to look for another solution?

Here are some pics, check out how close the spacing is for weber manifolds.
Please excuse the dirt. I still haven't cleaned them up.

This is gonna be fun. (IMG:style_emoticons/default/beerchug.gif)

(IMG:http://www.914world.com/bbs2/uploads_offsite/i694.photobucket.com-11752-1345224315.1.jpg)

(IMG:http://i694.photobucket.com/albums/vv310/Kevin31188/DSC03555.jpg)

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(IMG:http://i694.photobucket.com/albums/vv310/Kevin31188/DSC03552.jpg)

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(IMG:http://www.914world.com/bbs2/uploads_offsite/i694.photobucket.com-11752-1345224346.3.jpg)

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Dr Evil
post Aug 17 2012, 01:41 PM
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Always interesting (IMG:style_emoticons/default/popcorn[1].gif)
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mrbubblehead
post Aug 17 2012, 02:02 PM
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DBCooper
post Aug 17 2012, 02:06 PM
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I had the GSXR TB's back in the day. I actually never used them, went to a single TB because it's so much simpler, but you're right, those look better in every way, almost ideal.
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kevin311
post Aug 17 2012, 03:59 PM
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The best part is the whole assembly was $60.00 shipped to my door. So if it doesn't work out its not going to break the bank. I'm excited about this project, I always liked the look and especially the sound of webers but I don't want carbs.
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mrbubblehead
post Aug 17 2012, 04:02 PM
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did you happen to get the mounting boots? looks like it wouldnt be to hard to make some adapter flanges to adapt to the manifold...
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mrbubblehead
post Aug 17 2012, 04:09 PM
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seems like i recall someone over on the type4um doing something very similar. but he was having a problem with his throttle bodies staying put. like they were coming loose and popping out of the boots. i wonder if you could fab up an aluminum flange and weld the throttle bodies directly to the flange. then bolt them to the manifold. then they would be hard mounted.
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kevin311
post Aug 17 2012, 04:33 PM
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The plan is to fab up some adapter flanges to mount with rubber boots. Then make some brackets that attach between the weber manifolds and the bolts for the oem bracket in the side of the TBs to hold them solid. Unfortunately I didn't get the stock rubber boots with these, but found a set on eBay I might buy.
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Chris Pincetich
post Aug 17 2012, 06:59 PM
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rick 918-S
post Aug 17 2012, 07:21 PM
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Love it! (IMG:style_emoticons/default/popcorn[1].gif) Easy to make an adaptor to transition that set onto the manifolds! That cast in piece between the TB's would make for a solid mount to hold them to the boots. (IMG:style_emoticons/default/beerchug.gif) 37mm should flow enough volume to feed a 1.7 air pump.
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euro911
post Aug 17 2012, 08:11 PM
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Looks interesting. (IMG:style_emoticons/default/popcorn[1].gif)

I don't know much about FI, but with ITBs, will it 'sound' similar to a carb'd engine? I'm already getting tired of the noise the carbs produce right behind my head (IMG:style_emoticons/default/dry.gif)
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kevin311
post Nov 25 2012, 02:32 PM
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I got the ITBs mocked up on an engine today. I found some flange adapters for a Harley Davidson that are 40mm that fit perfectly on the empi manifolds. They are not bolted down in the pics.

(IMG:http://www.914world.com/bbs2/uploads_offsite/i694.photobucket.com-11752-1353875554.1.jpg)
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Sleepin
post Nov 25 2012, 02:48 PM
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Wow! Amazing project!

Are the Harley adapters stout enough to hold the weight of the throttle bodies, rail, filter and hoses? Or will you need to mount a stabilizing bracket to hold some of that weight?
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ConeDodger
post Nov 25 2012, 03:42 PM
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I'm not sure how well this will work. I have to assume you have stock 1.7 internals. Cam, p&c's, heads.

If so, you had about 1.75" of throttle plate. Less actually I think. You will now have 5.8"+ throttle plate area without increasing anything else to use that volume.
You have 425cc/cylinder.

Let's compare my engine. I have 6.25" of throttle plate area but I have 608cc/cylinder, 200cfm heads, and tangerine headers. All this together produces 225hp and over 200lb/ft of torque in a table-flat curve.

I think you have to pay attention to the other parts of the engine before you can expect that to work. I love the innovation though. A few more details and you'll have a screamer!

Good luck!
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ConeDodger
post Nov 25 2012, 03:48 PM
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To answer your questions, yes, the stock pump on mine is now set at 40psi. I used an aftermarket common plenum from Golden Eagle I think? Search my build thread for pics of it.
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kevin311
post Nov 25 2012, 04:47 PM
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I had similar thoughts about the throttles when I started this project but I figured it couldn't be worse than weber 40s and I've seen those on smaller engines than mine.
So I figured what the heck, why not. I'm running megasquirt and it would be very easy to switch everything back. I think I'm into this about under $100 so it's worth it even if it doesn't wor, just for the fun/experience.
The Harley flanges are surprisingly stout. The rubber is at around 1/4 of an inch thick and the bases are reinforced. I think it should be okay but have plans for brackets if needed.
Thanks (IMG:style_emoticons/default/beerchug.gif)
Kevin
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ConeDodger
post Nov 25 2012, 04:59 PM
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I thought of that too. Carbs cover their sins in many situations by running pig-rich. Really good running carbs are a real joy. I have triple DCOE's on my 240Z that now fit that description...

I just wonder if you'll be able to get EFI level control everywhere. Still, don't let me stop you. I love the critical thinking here. Prove me wrong!
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Dr Evil
post Nov 25 2012, 06:25 PM
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Send me your transmission!
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Dont forget to use a phenolic spacer to soak up the heat so you dont cook your injectors.

Very cool! (IMG:style_emoticons/default/thumb3d.gif)
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wndsrfr
post Nov 25 2012, 06:32 PM
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Super cool looking setup but I'm concerned with your injector flow rate....might be a bit tight with 1.7l displacement vs. 0.8l on the Honda. Do you have a wideband AFR installed to watch for lean running......?
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FourBlades
post Nov 25 2012, 06:42 PM
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Go go go!

Love how cheap the tbs are...

A great experiment. (IMG:style_emoticons/default/piratenanner.gif)

John
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