custom individual throttle bodies? fab your own

[jpnovak]

I was looking for potential individual throttle bodies for a future motor build which will likely be a hot 3.2SS. One of the goals of this project is to investgate various EFI systems. In order to take advantage of hot cams and other typical Hp goodies I need individual intake runners. This leaves all but a few usual choices for fuel mixing...

In my search I came across some information from a honda tuning board.

http://www.homemadeturbo.com/tech_projects/itb/index.html
http://honda-tech.com/zerothread?id=775280&page=1

The listing of this project uses a Suzuki GSXR throttle body mounted to the stock Honda intake manifold. I think something similar could easily be done and the sizes are just about right.

The GSXR 700,1000 ITB have 48mm butterflys and 42mm port size. the GSXR 600 has a 44mm butterfly and 38mm ports. This could be configured easily to whichever size engine you were bulding, except for a 3.6+.

They come with 4 lined together. Two sets for 4 could be separated, shortened to 3, correctly spaced and setup for a weber/pmo manifold using a custom adaptor plate. minimal fabrication would be required.

Here's the best part. other than fab time the parts could be found for under $300. This is an order of magnitude cheaper than the other choices of TWM, etc. Of course, one would still have to find the right injectors, etc.

Since custom runners would be made, you could calculate optimum butterfly and injector distances from the intake valve. This could give you optimum flow and atomization with minimal effort.

What do you think? I am interested in some opinions from those who know more than I.

[MotoSook]

Jamie....I've been noodling that too. I've got a more low tech, low cost solution in the secret Gruppe B lab...just can't find time to finish it

[KobaltBlau]

Very interesting, Jaime.

Souk, don't hold back on us.... let's hear about it!

now the real question is, what is the measurement between the bore centers of a set of weber IDAs?

[jpnovak]

I'll measure the carbs tonight.

[Randy Webb]

I hope the US military doesn't bomb the secret Gruppe B lab. .....

Seriously, keep us posted on this. It's interesting -- esp. the under $300 part.

[MotoSook]

The secret GruppeB lab....even I forgot where it is

And my low tech solution will not be as low cost as $300, but it will be a good alternative to some more costly induction ...that's all I'm saying...otherwise I'll be erased.

[MichiganMat]

me likey low costy

[Shuie]

Originally posted by MichiganMat
me likey low costy

Me to. Cant find a way to make it happen though.

No matter how I try to piece an EFI system together in my head I wind up with a list of parts totalling $3k-$5k.

[KobaltBlau]

Originally posted by jpnovak
I'll measure the carbs tonight.

Cool, thanks Jamie.

[KobaltBlau]

Originally posted by Shuie
No matter how I try to piece an EFI system together in my head I wind up with a list of parts totalling $3k-$5k.

Are you thinking MegaSquirt? that should help a bit.

[Tim Walsh]

Custom ITB's for under $300 would go a LONG way towards making hotroding the CIS cars and even *gasp* the MFI cars too. I'm going to be really interested in this to see how it progresses.

[jpnovak]

Don't worry Tim, I will post some results of my experiment. Now I need to find the injection system to go with the ITBs.

I was thinking I could use some CIS runners with injector bungs. Cut them off above the bungs and weld an aluminum spacer between the runner and the TB. Should be a simple fab. I don't know about linkage though. That might take a bit of thinking. All the geometry is slowly coming back when you have to think about arc lengths through bell cranks... End result must be 90^o butterfly travel for WOT!!

[Mike Bonkalski]

Here is a drawing of the linkage for DTA throttle bodies. Hopefully it can be used as a reference.

[jpnovak]

HMM cable actuated. I assume there is a splitter for the cable somwhere to reach L and R bank. I like that design. I wonder how linear that cable run is.

Funny how my ideas just seem to gather information and get more complicated than originally planned.

[KobaltBlau]

Jamie, did you get a chance to measure the center-to-center on the carbs?

[jpnovak]

Sorry, I didn't I will go home at lunch and check. Last night I got too busy with suspension setup.

[Tim Walsh]

DO the CIS runners have enough of straight section above the injector bung to braze or adhear in some fashion to the throttle body?
Also alot of the cable system should be pre done if you're using preexisting throttle bodies, shouldn't they?

[KobaltBlau]

no worries. I'm just trying to figure out how similar the "bore spacing" is between IDAs and the GSXR750/1000 ITBs. The guy that put them on the honda said "I think it was about 80mm" on the 'Zuki throttles.

On a related note, I looked at some of the honda throttles on ebay. Most of them look less desirable because the have the injectors mounted in a "shower" configuration above the throttle plate. The problem is that the injector mounting frame seems to be bolted to the airbox, and the airbox is not the right shape for our application.

[jpnovak]

CIS runners have enough space to weld a section of Al pipe to extend the TBs. Most applications I have seen (links above) use an extension. This may only be to obtain clearance in the engine bay. The runners already have an injector bung in place.

I just had a followup post on the engine board about dimension placements.

The 911 throttle linkage is all rods and cranks. no cables involved. I just bought a single set of GSXR TBs (group of 4) as a trial part. Once they are in my hands I can comment on hooking up the linkage. If they are mounted to weber manifolds and use the stock GEXR injector ports the linkage issue may be solved. I could likely just hook up like a weber carb using a new throttle end cap arm and the existing linkage.

[KobaltBlau]

Originally posted by jpnovak
I just bought a single set of GSXR TBs (group of 4) as a trial part. Once they are in my hands I can comment on hooking up the linkage. If they are mounted to weber manifolds and use the stock GEXR injector ports the linkage issue may be solved. I could likely just hook up like a weber carb using a new throttle end cap arm and the existing linkage.

Cool you already bought a set of GSXRs!

I was thinking along the same lines: weber manifolds, stock GSXR injection ports (position is good IMO), and modified weber linkage. Even if people don't have them to start with, the weber linkage and manifolds aren't that expensive. it's the throttle bodies that are the killer, as you know.

It looks like there are 4 short throttle shafts so cutting one body off might not be very difficult (fingers crossed)