Re: 79 DOHC 750 Turbo project

Posted by turbocity tom on Dec 02, 2014; 12:14am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/79-DOHC-750-Turbo-project-tp4054442p4054607.html

I have a slight advantage - I have worked in turbos for 35 years and have built many systems over the years.

The turbo is a custom compilation of parts- largest T25 compressor wheel/ smallest turbine wheel and smallest A/R exhaust housing. including a positive seal to work in the draw thru set up. Carb is sized for a 1000-1200cc engine- that is equal to the 750cc plus the boost.

I have a lot of tuning practice on Weber carbs and have the tools to make custom sized jets. Tuning has really not been that difficult. the biggest issues have been the Mikuni HRS42 is really designed for the V-twin Harley engine and the needle profile doesn't fit the 4 cyl turbo. really should have a custom needle made. Needs to be stepped, not a constant taper.  tried to make one on my cheap little lathe - BIG fail.....
The fuel curve leans just slightly as the engine passes in to boost. Above or below that point it runs perfect.

At this time I do not have a fuel pump on it- I have built a relay into the harness just in case. You really can not hold it in boost for very long (on the street)- it will go over the ton easily/ quickly.

Thanks     Tom