Volumex outboard manifold injection

[markw]

is there anybody on this forum who has successfully installed fuel injection on an outboard manifold? In other words, applying fuel injectors before the supercharger in the inlet tract.

I am in the process of scoping my rebuild. I know I want to move to a more sophisticated, distributor-less ignition. Doing so requires the addition of a subset of the sensors required for injection. I know I need to upgrade the fuel delivery system. A 45DCOE equivalent is an option, but the choke size required to avoid the throttle-open stall issue concerns me. Would replacing the carb with a fuel-injected equivalent avoid this issue, due to the improved atomization of the injectors?

I'm a little hesitant to go all the way to inboard injectors, given the complexity of the task. Hesitant, but not ruling it out.

[WestonE]

Hi Mark

Along the way I ran a Jenvey twin 45 Throttle Body outboard but with inboard injectors as well. I may still have the Jenvey TB and GC manifold for it. It could be done with large injectors. Be aware the back flow can be because a cam with overlap has been used i.e. a cam for naturally aspirated is a bad choice for a supercharger.

ERic 

[markw]

Ah, this is a learning for me. If I understand you correctly, the snap-throttle stall issue is related to backflow due to overlap? If that is the case, could folks run with bigger chokes as long as cam selection is good?

[WestonE]

Hi Mark

I do not know for sure because I have not done it. I went FI and invested a lot of time with a turbo and supercharger specialist rolling road (actually the UK Rotrex importer). Think matched cams inlet and exhaust where a turbo would have lower lift exhaust. Low lift at TDC but high acceleration to peak lift is what you want. So NOT 40/80 more like 3/57 in timing. A pair of Strada/Ritmo 130 TC cams with the timing shifted will do nicely.

Vernier cam wheels and knowing you can swing the cams 100 to 120 without piston to valve or valve to valve contact helps. You can go up to 10:1 with 97 octane plus and FI. You want flat top or minimal piston domes if you go up on compression. I would not do this with a carb and clockwork distributor!

Eric       

[markw]

Vernier cam wheels and knowing you can swing the cams 100 to 120 without piston to valve or valve to valve contact helps. You can go up to 10:1 with 97 octane plus and FI. You want flat top or minimal piston domes if you go up on compression. I would not do this with a carb and clockwork distributor!

I'm planning on moving towards a wasted spark or sequential mapped system, as I don't want to continue using the cam-driven distributor I am using now. Even so 10:1 might be a little hard to control fuel distribution in #4. What do you think?

[WestonE]

As long as you can get good atomisation of the fuel the air will carry it in proportion. The focus will be on enough to stop Number 1 or 2 running lean and hot. Expect different spark plugs by cylinder with warm at number 4 and cold at numbers 1 and 2. These are 3.75 cylinder engines the manifold is so uneven. 1 & 2 9 grade 3 8 Grade 4 6 grade.

They still go incredibly well.