Mongo

Gina you are a Saint!

Mongo

I am bumpiing this back up. If anyone is knowledgable with runner lengths and areas, will a 38mm throttle body and the same diameter piping cause a powerloss with a 41mm intake port diameter?

944CS

you'll be slowing the air down if you go from 38mm to 41mm, something you do not want to do. If you're asking if 38mm is too small for your power goals, first tell me: what is the compression ratio, what cam are you running, exhaust system details, stock head? vavle sizes...
Are you doing ITB's for looks/coolness, or are you trying to make real horsepower with a built motor?

Mongo

According to multiple intake runner area calculators on the internet, 1.5" ID or 38.1mm in metric is suitable enough for this type of engine and torque curve.

The ITB's are definitely NOT for coolness. I'm not looking for a significant 'real horsepower' gain. I am however looking to see if it improves the efficiency of the engine and utilizes the Bosch L-Jetronic better. Considering that our cars naturally run lean with this fuel injection system, I wonder if reduction of runner diameter may reduce the out-of-balance in the A/F ratio. I could be wrong about that one though.

Nevertheless, if these calculators and formulas are saying 1.5" is fine, then I guess I'll go with 1.5"

944CS

what do you mean by naturally run lean?

TopherDow

hey guys, there is some great info in this thread and i wanted to try and share a little if i could.

i know there are a few applications on other cars posted in this thread, but i wanted to share one made for a Nissan 240sx using the GSXR hardware and megasquirt software:

http://www.nicoclub.com/articles.php?id=226806

a little closer to your application than a Honda 2.0 liter

Mongo

The Bosch L-Jetronic system runs lean in upper RPMs on 944s.