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Question. I'd like to run a set of manifolds like these and then put Jenvey (or similar) throttle bodies on. Is there any (meaningful) advantage of running injectors closer to the valves (a la where they are for the CIS set up), or would running the injectors in the Jenveys be OK?
This is a complex answer. Really comes down to fuel atomization, valve/cam movent i.e. ramp rate, runner length and with EFI fuel injection phasing. And now we're getting into the finer details of extracting the most optimal burn. CIS is literally continuous fuel flow regardless of valve timing etc.. fuel puddles then gets sucked in. Mercedes and others utilized air shrouding in later designs to help with atomization. Carbs atomize the fuel at the throttle plate. If it falls out of suspension or puddles beyond that... That's runner length and air flow but since an engine runs over a range of rpm and cam/valve movement changes the pulse length... It's only optimum for a very narrow window. EFI, this is why there's so many injector flow patterns. Where is the injector in the runner, how many ports, CFM of port, etc.. Does it matter?, yeah it can for a race engine or for an engine where you have strict emissions STDs and want to optimize fuel economy, etc. For most though, not really. Just make sure you use the right injector for where it sits in the runner. And phasing seems to have more effect.
Yes, the difference between timed port sequential injection on EFI retrofits vs untimed (batch fire) is very noticeable at lower RPM. Like night and day for smoothness. A dual sync dizzy works very well for this, but it is not a common F-car after market item, i am not sure if anyone ever made one? Doug
By phasing, do you mean the injector firing at a different time in the cycle depending upon rpm? And, I suppose, throttle position, load, and a few other variables I haven't thought of. Do modern ECU's take this into account (Motec, Haltech, etc)?
Phasing based on cam timing events. Most notable at idle and part throttle, to mid rpm. WOT and high rpm events are happening I think too quickly to matter. Motec, link, vipec, and maybe others do this. Requires full sequential control. Not familiar enough with Haltech anymore to know if they do, but they probably do, it's not complicated code for it.
Additive mfg aka 3d printing is cost by volume. Large flat areas don't require that much material if it's not needed. Design development is different depending on mfg type, cast, machine and printed. With printed one can actually utilize more 'organic' design that is only possible with printing that could never be machined or cast. There's other hurdles though like the 'triangle problem' but that's more of a data issue.
