Subaru Impreza GC8 & RS Forum & Community banner

ITB's

69K views 206 replies 65 participants last post by  George.of.the.Jungle 
#1 ·
Individual Throttle Bodies.

Since there's so much discussion about them in inappropriate threads, I made a new thread, just for you!!

Discuss.
 
#8 ·
...yea the Blacktop and Silvertop 4AGE 20V people have swapped into their 86's came factory equipped with ITB's. I'd like to build a Toda equipped Blacktop 86 someday.... :drool:

That Tomei system is over $8000.

That's a lot of money for the gains you'd get. It seems like the law of diminishing returns would step in. I think with good tuning and a lightened rotational assembly you could also get good response. I don't even think Subaru WRC cars have ITB's.

I can see the draw though. The throttle response would be pretty awesome. It would be a rare and very cool set-up on a flat engine. They sound great too.
 
#11 ·
sounds like a good investment if you have the means of making or affording them. What is the benefit of the larger manifold in the picture? Just more air "stored" to be readily available? Like the torque box? Kinda crazy to spend 8K$ on that... thats 16x more than my celica is worth!
 
#15 · (Edited)
a buddy and i swapped a pulsar gti-r motor with ITBs into his 200sx. it's setup is fairly simple, i've posted pics of it on here before.. ever since then, i've always wanted to fab an ITB setup for the scoob.
 
#17 ·
Up for sure and maybe a little to the right....but the key is getting the lengths correct for your target peak. Getting the lengths right means taking a whole lotta other factors into consideration. When designed correctly, the VE of the motor can be increased significantly.


The response is improved greatly, since the throttle blades are very close to the intake valve(s). When the throttle is opened, the amount of time it takes to fill the intake port and then cylinder is greatly reduced. Reflected pressurewaves work more efficiently in each throat and are not effected by the other cylinders as in common plenum designs. There is no limit to available air for intake, The only limiting factor is the flow capacity of each throat.

The key to getting the ultimate output from any motor is to treat it as individual cylinders, tuning each one seperately for peak performance. ITB's are just a part of that practice.
 
#24 ·
Motorcycle TB's are a great way to go on inline engines. Alot of the hard work is already done, and they simply clamp on to tubing stubs. All the throttle linkages are close to being usable from the start and the diameters are pretty good for more mild street engines. The aftermarket is pretty big for bikes too....

I looked into adapting a set for one of my projects, but splitting them would've been a PITA.

FWIW.....I learned yesterday that an EJ18 throttle blade is the same diameter as one throat of a WRX TGV :) Unfortunately, the blade is too thick to slide into the TGV shaft. :( It's still progress though.
 
#27 ·
A throttle body modification/boring shop should be able to turn WRX TGV's into ITBs fairly cheaply.

The WRX TGV's will bolt onto ANY Phase II EJ motor SOHC or DOHC & already have injector bosses in them.

You just have to feed the MAP sensor which is as simple as a barbed fitting placed below the throttle plate, fab a TPS mount which should not be too hard either, & adapt a throttle linkage that will work I think something from a VW should be adaptable.
 
#30 ·
They can be done with a MAF sensor too, you just have to limit the incoming air through that MAF sensor. It could be as simple as modded TGV's under a regular plenum and a tube flange instead of a throttlebody, or something like the Tomei setup. Any forced induction system will be going through the same sort of setup....so it's definately possible.
 
#32 · (Edited)
I took some pics of what I'm (slowly) working on. These are 02 WRX TGV housings with the dividing walls removed and smoothed out. I didn't "port" them, as I even left some casting weirdness in other areas. Note that I didn't touch the ports on the cylinder head either.




This is the half butterfly sitting on top of the shaft. Next is an EJ18 TB butterfly sitting on the same shaft.


Here is a dirty phase II EJ22 head with the TGVs installed.
 
#35 · (Edited)
I use a standalone ECU running speed/density air metering.:naughty: I need to drill for a vacuum barb on each throat and plumb it to a collector for the MAP signal.

We have a CNC laser at work, so I think I'll have them cut me some slugs for butterflies. Then I can set about grinding the housings so they swing fully open. Once I get that done, I will work on the throttle linkage. Luckily, my TPS will bolt right onto either housing. I'm in no hurry, as I can still use these under the 06 upper plenum if I plug the shaft holes.

Idle control will probably be similar to a GpN car running anti-lag. The blades will always be open a certain amount, but the ECU will vary ignition timing and fueling to "cycle" the idle. Or, I can drill a small hole in each blade, then experiment with the sizes until I get a decent idle rpm. Cold weather will be a throwback to my carberetor days where I'll use my foot for idle control until she warms up. I can also make a second port in each throat for an air bypass solenoid from a 98RS, modified to mount to a plate with a tube leading to each cylinder.

It's all progress......
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top