I have just realised a weak point in my plan to microsquirt my Lotus Eclat and could use a little guidance. It has a 1-3-4-2 firing order and I am using the stock Zenith-Stromberg intake meaning that cylinders 1-2 and 3-4 share carbs which I have replaced with Honda RC-51 throttle bodies. These seemed an ideal choice since they have two 335cc injectors on opposing sides of the throttle that spray more or less right down the intake runners. The problem that I am now seeing, a few hours on the lathe too late, is that when number 2 and 3 open their intake valves they will be getting 3/4 of the fuel leaving 1 and 4 running super lean.
The manifold also has a bridge joining the two sides just past the bodies but I am not sure if this will make much difference beyond making the slightly oversized throttle bodies effectively that much bigger.
I am hoping that by setting up for 1 squirt alternating on these slightly large injectors I can get the timing just right that most of the fuel for 1 and 4 can be injected after 2 and 3 intake valves close but that seems like a very small time window to be working with.
Any advice is most welcome as I am starting to think I will be spending $1000 on a dellorto manifold and webber throttle bodies.
EDIT: I did a search for siamese intake and I'm finding the info I need I think but any other advice is still more than welcome. Thanks search function!
Lotus 907 - I may not have thought this through enough.
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Read the manual to see if your question is answered there before posting. If you have questions about MS1/Extra or MS2/Extra or other non-B&G code configuration or tuning, please post them at http://www.msextra.com The full forum rules are here: Forum Rules, be sure to read them all regularly.
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efahl
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Siamesed ports are a very significant challenge for EFI, even the BMC guys never got it right on the last Minis that had them (read their patent for some good background info: http://www.not2fast.com/patent/ top one on my Big List of Interesting Patents).
If you are looking for max HP and aren't willing to put on a different head, then I hate to admit it but I'd probably go with carbs as that's the only truly proven method for getting a proper mixture into a motor with siamesed ports.
If you just want it to work well and have low emissions and so on, then I'd try putting in some port separator blades and do port injectors down past the blades. There would still be some backwash and charge stealing, but if you can get the injectors in deep enough, it should be tolerable. The new sequencer board for uS would probably help out with timing the injection events, too, allowing you to find what injector timing produces the least stealing.
Eric
If you are looking for max HP and aren't willing to put on a different head, then I hate to admit it but I'd probably go with carbs as that's the only truly proven method for getting a proper mixture into a motor with siamesed ports.
If you just want it to work well and have low emissions and so on, then I'd try putting in some port separator blades and do port injectors down past the blades. There would still be some backwash and charge stealing, but if you can get the injectors in deep enough, it should be tolerable. The new sequencer board for uS would probably help out with timing the injection events, too, allowing you to find what injector timing produces the least stealing.
Eric