Hello EFI/fuel mixture theory interested guys,
recently I got a link to a BMW twin flat aftermarket EFI (carb replacement):
http://www.silent-hektik.com/page16.html (German)
rough English for you:
http://babelfish.altavista.com/babelfis ... age16.html
but both figures (at page16.html) show what's going on and a photo of such a throttle body:
http://www.silent-hektik.com/img119.gif
Do you know other (OEM) setups which use this idea?
I've allways thought that the hot inlet valve should help to vapour fuel, not high air speed around partial opened throttle. IIRC this was the reason why injection should be finished before inlet valve opens to ensure that fuel has enough time time to get well mixed with air.
Is this esoteric tuning or is there any theoretical background?
One reason could be that's not possible to hit the inlet valve directly because the manifold (in cylinder head) is bended to much.
At least in my flat twin (Citroen) it was very hard to find (and weld!) a position for injector bungs so that the injectors point to inlet valve.
What do you think?
»Horst
Single body injection angle of 90° - why?
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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.
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.
I can't say I agree w/ that page. They seem to indicate that a fuel injector squirts in a nearly straight line. Some probably do, but most spray patterns I've seen spread out to about 30 degrees. And at ~40psi, you get decent separation of fuel into tiny globules anyway. I don't think it takes much to get from there to air dissolved fuel.
I do understand what they're trying to do w/ the throttle plate, but I'd imagine that a setup like that would tend to spray and pool the fuel on the wall which is NOT where you want it.
Subarus and others use a tumble generator valve(TGV) just before the injector that does something similar. It's basically a secondary throttle that only covers about 75% of the intake runner at max. At low RPM, low throttle This forces the air around the valve faster and causes it to tumble right where the fuel is injected. Higher RPMS and throttle positions cause the TGV to open relieving the restriction.
Anyway, even in this setup the injector is angled towards the intake valves. If you have the choice, I'd say you want a wide spray injector, angled enough to it's not spraying on the opposite wall, but close to the throttle plate(w/o touching) so you get good vaporization from the injector, good tumble from the plate, and some decent time for these things to work.
I've often wondered what would happen if you aim your injector backwards up the intake towards the throttle. Seems like you could get some really nice mixture going on, but I'm not going to try it
I do understand what they're trying to do w/ the throttle plate, but I'd imagine that a setup like that would tend to spray and pool the fuel on the wall which is NOT where you want it.
Subarus and others use a tumble generator valve(TGV) just before the injector that does something similar. It's basically a secondary throttle that only covers about 75% of the intake runner at max. At low RPM, low throttle This forces the air around the valve faster and causes it to tumble right where the fuel is injected. Higher RPMS and throttle positions cause the TGV to open relieving the restriction.
Anyway, even in this setup the injector is angled towards the intake valves. If you have the choice, I'd say you want a wide spray injector, angled enough to it's not spraying on the opposite wall, but close to the throttle plate(w/o touching) so you get good vaporization from the injector, good tumble from the plate, and some decent time for these things to work.
I've often wondered what would happen if you aim your injector backwards up the intake towards the throttle. Seems like you could get some really nice mixture going on, but I'm not going to try it