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Re: Jupiter Carburettors

From: Philip Dingle
Fromemail: Pdingle@comcast.netNoSpam!
Category: Technical
Remote Name:
Date: 30 Oct 2004
Time: 21:33:07


Mike; Can't help with the carburation, but do have some comments on use of fuel injection:- If one is considering moving to fuel injection in some form, a throttle-body may be the way to go since it is likely to work out better than PFI (port fuel injection) on the Javelin/Jupiter due to the siamiesed ports. You might have difficulty finding a throttle-body that is sized right for the individual banks, ie, for 750 cc's, so I would be inclined to consider building a manifold to join the two banks together (as on the pre-war engine) and use a single throttle-body suited for a 1.5 litre engine. This would likely bring an additional benefit of improving the low speed torque due to the longer intake tract from throttle to inlet valve. Better still would be to create a "log" style Helmholtz resonator mounted horizontally above the fan spindle, but below the coolant hose, having runners down to the cylinder heads, and the throttle-body mounted in the middle between the hose "Y". This would bring an additional benefit that one could then easily run a duct from there to a single air cleaner that would minimize the staccato intake sound of the standard set-up. The resonator would provide a measure of tuned supercharging, and the throttle-body in conjunction with an ECU (eg, Motec), would give electronic control over fueling and spark timing. This should make for a much more refined engine with better performance and improved fuel consumption. I have given some thought to PFI, but you run up against the same problems outlined at this web site:

Last changed: November 19, 2008