Out of boredom...
Thread Starter
...94% correct.
Joined: Oct 2002
Posts: 1,283
Likes: 2
From: High Texas
Out of boredom...
...I built an individual throttle body assembly and manifold that bolts to the S4 LIM. It uses four 38mm throttle bodies with runners to the individual four ports on the LIM. I bored out the ports on the LIM to make the transition from 36mm runners smooth and even but there's a little bit of chokeage from the stock piece it's self. I may go back some time and build a different lower or build this to bolt straight to the block...but dunno...just doing this because I'm bored.
Anyway, I built four runners inline to the ITB's and welded injector bungs on the first and fourth runner so that I could bolt up an S5 fuel rail and pressure regulator. I may make a custom fuel rail later but don't see the need. I intend to leave the primaries right where they are.
The ITB's are verticle. there will be no plenum...I'm just going to make four individual runners that will merge just before the stock air meter...but I'm relocating said meter to make a mass air assembly easier to use later on if i change ems.
At the moment I intend to run it with the stock computer and injectors and everything. i'm not really expecting any kind of gain...it's just something I want to tinker with. It's going on a mild mild port engine and will have a full exhaust, running premix...obviously.
Anny comments?
Anyway, I built four runners inline to the ITB's and welded injector bungs on the first and fourth runner so that I could bolt up an S5 fuel rail and pressure regulator. I may make a custom fuel rail later but don't see the need. I intend to leave the primaries right where they are.
The ITB's are verticle. there will be no plenum...I'm just going to make four individual runners that will merge just before the stock air meter...but I'm relocating said meter to make a mass air assembly easier to use later on if i change ems.
At the moment I intend to run it with the stock computer and injectors and everything. i'm not really expecting any kind of gain...it's just something I want to tinker with. It's going on a mild mild port engine and will have a full exhaust, running premix...obviously.
Anny comments?
Thread Starter
...94% correct.
Joined: Oct 2002
Posts: 1,283
Likes: 2
From: High Texas
I didn't bring my digicam to work with me or I would have taken step-by-step shots. It's not very impressive...just a imple flange with splayed runners. It'll require some work and some better tubing than what I have to make a nice gradual and madrel transition...the #1 and #4 runners are coming in at a decent angle.
...man, I just had a thought about how cool it is to be able to go down to the shop and whip together a ITB manifold at work.
...man, I just had a thought about how cool it is to be able to go down to the shop and whip together a ITB manifold at work.
Last edited by Makenzie71; Sep 23, 2005 at 12:24 AM.
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Thread Starter
...94% correct.
Joined: Oct 2002
Posts: 1,283
Likes: 2
From: High Texas
holy crap...this has been here for 6 hours and now everyone cares and everyone wants pics...lol.
Gotta wait til the a.m...I was looking for insight on using the assembly with the stock management mostly at the time...but I WILL get you guys some pictures I promise...lol
Gotta wait til the a.m...I was looking for insight on using the assembly with the stock management mostly at the time...but I WILL get you guys some pictures I promise...lol
Joined: Feb 2001
Posts: 29,798
Likes: 128
From: London, Ontario, Canada
Must have had a lot of boredom time. 
Sounds cool, but with the stock ECU you need to respect how the primaries open with regards to the secondaries. At low throttle, the primary throttle plates open a little before the secondaries do. This way, you drive on the primary ports only under VERY light throttle and idle. This dramatically improves low end, idle stability, off idle throttle response, etc. Grab an FC throttle body, look through it and observe the action of the throttle plates while you "rev" it and you will see what I mean. The stock ECU doesn't deal very well with all the ports opening at once, and you will find that idle and off idle throttle is terrible. Hesitations at low throttle will also result.
Also, this thread is useless without pics.
Sounds cool, but with the stock ECU you need to respect how the primaries open with regards to the secondaries. At low throttle, the primary throttle plates open a little before the secondaries do. This way, you drive on the primary ports only under VERY light throttle and idle. This dramatically improves low end, idle stability, off idle throttle response, etc. Grab an FC throttle body, look through it and observe the action of the throttle plates while you "rev" it and you will see what I mean. The stock ECU doesn't deal very well with all the ports opening at once, and you will find that idle and off idle throttle is terrible. Hesitations at low throttle will also result.
Also, this thread is useless without pics.
Thread Starter
...94% correct.
Joined: Oct 2002
Posts: 1,283
Likes: 2
From: High Texas
Motorcycle throttle bodies are great...they are, by far, the easiest things to tune. I slapped these on a make shift manifold I built for my supra a while back and synced them all. The center two open up 5* before the other two. I'm not sure that's enough...I'll have to wait til I have another RX-7 to put them on...lol. I'm thinking at most 10* advance...it's just hard to duplicate the stock bodies very easily.
Thread Starter
...94% correct.
Joined: Oct 2002
Posts: 1,283
Likes: 2
From: High Texas
Originally Posted by GUITARJUNKIE28
38*~3.14= ~113 * 4 = ~452
45*~3.14= ~141 * 3 = ~424
am i wrong?
45*~3.14= ~141 * 3 = ~424
am i wrong?
I'm looking at having 7238.228mm.
multipersonality disorder
Joined: Feb 2002
Posts: 5,656
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From: so. cal
Originally Posted by Makenzie71
You're wrong. Total surface area of all four throttle bodies (if they were 38mm) would be 4536.46mm. Total surface area of the 3 45mm stockers is 4771.293mm.
I'm looking at having 7238.228mm.
I'm looking at having 7238.228mm.
do the math for me if you would please...
sounds like an interesting project but a simple larger dual stage throttle body would be much simpler as there would be no tuning and no trying to figure out how to stage the secondaries properly.
