ITB...

[Superdave]

42 sounds good, mine are 45 and work fine though.

you are aware of all the other issues that come with ITB's right? Crappy MAP signal, all kinds of AE tuning issues, vacuum plumbing, throttle shaft misalignment, IAC motor, etc...


don't get me wrong, they're fun and work really well but expect to spend quite a bit of time working out the bugs. I've lost track of how many times i've had mine apart.


BTW, 2% TPS is about 30 MPH on mine VS about 20% on a normal plenum setup.

[ericjon262]

thanks for posting that! thats pretty cool! what size TB's do you guys think I should shoot for?

His TB's were 48mm, his engine displaces .75l/cylinder.

mine is a 3.5 and displaces .58l/cylinder.

I'm thinking about 42mm would be ideal....

[Superdave]

http://www.youtube.com/watch?v=_Eshyr9CdlI&feature=channel&list=UL

good ideas in that vid.

[Superdave]

from Intake valve to the throttle plate i measured 13.5", my velocity stacks add 3" to that.


97000/13.5 = 7185 RPM peak
97000/16.5 = 5878 RPM peak

If i could trust my dyno graphs i'd point at either one to be correct however they won't use the spark pickup and rely on the roller RPM to calculate engine RPM. I run up to 7K every time and the graphs stop at 6500.

[ericjon262]

http://youtu.be/jLikjChQlPE

not mine, but badass!

[ericjon262]

http://www.ebay.com/itm/01-03-SUZUKI-GSXR-600-GSXR600-THROTTLE-BODIES-BODY-2001-2002-2003-GSX-R600-GSX-R-/110901661737?hash=item19d2411029&item=110901661737&pt=Motorcycles_Parts_Accessories&vxp=mtr#ht_1360wt_1163

Like those FF?

[ericjon262]

I've seen superdaves, it rocks!

I think the triumph TB's are 45mm, but I do not have confirmation on that yet.

[Superdave]

Lets define runner length... then i'll go measure mine.

top of the velocity stack to the back of the intake valve? If we go intake valve to throttle plate then mine are the same length as a stock 3500, unless you measure the 3500 UIM's distance from port to TB... which is WAY longer.


I have zero problems with low end torque, and top end peak power is a little lower than my old 3500 UIM. It feels like it peaks around 6500, my old UIM would pull hard past that but it made less power overall.

[ForcedFirebird]

Are you comparing small DOHC ports to push-rod 2v? Where did you come up with 14"?

Also were the runners as large as the 3x00? Sure if you want to compare apples to oranges we work on a lot of BMW's and the ITB runners are never more than a few inches and are making well over 340hp on 3l engines - but that's not a 60v6 either.

ITB's are not new, look at Superdave's build here on the forum.

Eric, what size are those Triumph ITB's? I looked at them a while back to use on an m20 and remember them having quite a large bore - check out the GXSR TB's, there's a few years around 2000-2003 (IIRC) that had throttles that could separate and are popular choices for ITB's in cars due to the fact that that the TB's aren't cast a s a single unit.

[JerryRigg]

Longer than some ITB setups, sure. Too long? That's a bit subjective, IMO. The Mazda ITB's I was working on developing have an optimal runner length of 14" - we settled for 12" OAL I believe. It depends a lot where you are setting up your powerband. Using ITB's on a stock LIM should give a reasonable amount of usable low end torque due to the long runners and great top end power as well.

Only one way to find out?

[ForcedFirebird]

Problem is when you put ITB's on the LIM, the runners are far too long.

[JerryRigg]

I can make a set of LIM > ITB adapters if there's interest

[ericjon262]

Anyone have any thought on ITB's + turbo? I keep running into clearance issues on my 3500 intake.

maybe 6 triumph TBs and an adapter plate?

http://www.ebay.com/itm/06-09-Triumph-Daytona-675-Throttle-Body-Bodies-Carbs-/160546343681?hash=item25614ecb01&item=160546343681&pt=Motorcycles_Parts_Accessories&vxp=mtr#ht_2791wt_905

I'd love to hear thoughts on the subject!