ALFAGTV6.COM

Jarle · Post by **Jarle** » Tue Jan 17, 2006 8:26 am

Building a "high output" V6. Have realised that the stock 36-37mm inntakes are far to small for massive power. Engine is fitted with most of the good stuff, forged high cr pistons, adjustable engine management, custom built exhaust ...... Can anyone with experience with ITB`s on the 3.0 12V recommend a reasonable ID for this engine. Power output should be in the area 260-280hp. In "four stroke performace tunung" Graham Bell writes:
Throttle bore dia: hp of one cylinder:
-36 27-37
-40 35-46
-45 43-56
-48 50-65

As I am working with motorcycles I choose to go for the GSXR 750 throttlebodies, ID 42MM. Anyone with Experience?

Jarle

Mats · Post by **Mats** » Tue Jan 17, 2006 9:30 am

Is it easy to change center to center distance on those?

Post by **Zamani** » Tue Jan 17, 2006 9:57 am

Are you gonna run MAP or MAF based system?

The MAP based system is a little tough... because you need to make 2 holes per throttle, one for MAP and one for idle.... unless you adjust the throttle opening for idle.

Or are you just going to use TPS?

Jarle · Post by **Jarle** » Tue Jan 17, 2006 10:20 am

Yes very easy to work with these Keihin/suzuki units.
I am using Autronic SMC. Use map sensor and TPS. The bodies comes with 2 vacuum outputs/holes.

Jarle

Jarle · Post by **Jarle** » Tue Jan 17, 2006 10:31 am

Zamani: I missunderstood your question. Will use the thr/map setting when mapping the engine.

Jarle

Jarle · Post by **Jarle** » Tue Jan 17, 2006 10:43 am

Throttle is mapped towards the TPS, and ignition towards the MAP.Open throttle for idle... I need vacuum for the MAP, fuel pressure regulator and brake booster.

junglejustice · Post by **junglejustice** » Tue Jan 17, 2006 10:52 am

Pretty interesting using the bike ITBs...

50mm up top tapering down to a 42-43mm seems to work fine on the big-bore 12 valvers that we have done... (You want the taper for velocity...)

Any way, use just one vacuum port per ITB with the MAP setup and then simply drill one tiny hole per t-body plate of equal size for idle! That way you don't have to mess with trying to always map idle or set the 6 ITB's to each remain open EXACTLY the same amount...

Pain in the arse if you ask me...!

Start with very small idle holes and then take them all progressively larger and larger to add more and more air for idle control! Set the ITB-plates to full shut - easiest!

Mats · Post by **Mats** » Tue Jan 17, 2006 12:00 pm

Jarle wrote:Throttle is mapped towards the TPS, and ignition towards the MAP.Open throttle for idle... I need vacuum for the MAP, fuel pressure regulator and brake booster.

i.e. Alpha-N instead of Speed-Density? A mix? Sounds strange.

Post by **Zamani** » Tue Jan 17, 2006 12:35 pm

Autronic's algorithm I suppose.

Jose_76 · Post by **Jose_76** » Wed Mar 15, 2006 8:46 am

Jarle, did you finish the bike ITB's adaptation?
Could you tell us another bike models proper to donate their ITB's?

enzo · Post by **enzo** » Wed Mar 15, 2006 11:06 am

Jose
have a look on this thread
http://www.msefi.com/viewtopic.php?t=6627

Throttlebody size, ITB`s.