Suppose a fellow wanted to build an 8 stack fuel injection system in a limited space. Is there a reason the injectors couldn't be placed ahead of the butterflys? Would the spray 'fog up' on the plates and ruin the mix? I know... Nobody dose it that way... but why not?
Dunno, but you want the injector close to the valve, not further away, you don’t want pooling of fuel on the butterfly, you probably don’t want the fuel particles falling out of suspension around the butterfly (passing the butterfly when part closed). Note I only play with carbs so that’s just an educated guess. Went off and googled, like anything if you start changing the norm your up for some dyno hours to get it right, apparently if your pumping large amounts of fuel it can be an advantage to move the injector back to allow better atomisation, but having the butterfly in the way may screw that up. An expert will be along shortly.....
Yes, throttle body systems did that. Notice the general consensus is that throttle body sucks. Youre taking a system infinitely better than carburetion , and saddling it with one of its woes. How good is fuel atomization when its just being pulled in drips off the side of the throttle plate?
Define your goals and explain limited space. FWIW, I've seen full race stack injectors with the injector spraying down directly into open air above the air horn. Works great at WOT. Anyhow, these PJ don't have the nozzles above the butterflys. jack vines
Just a bit of Friday night bench racing really. I was looking at a photo of an early hemi with sort of cross ram with individual runners that tucked into the valley real snug. It looked like all the plates were on one shaft.. Obviously I was wrong... It has been done before. And I agree... (my spell check won't deal with atom-i-sation no matter how many ways I screw it up), that its got to disturb the air flow. Its all part of my evil master plan to put us all in very small cars with very large engines. These are the things that I do when I get board
If we can ignore what’s delivering the fuel (pump, pill, injectors, or a computer and injectors) , I know my local expert wants a throttle body with the injector under the butterfly. When converting mechanical to electronic, he wants the same “tip” on the butterfly to the injector (if that makes sense). This all has to do with off idle throttle response, not WOT. So I’d guess you’d like the injector under the butterfly for a street system, regardless of how it’s controlled. I know guys make mechanical system work on the street, but they’re the exception not the rule. I remember watching the CanAm cars run. I don’t think street driving was high on the list for them.
I dunno. I run a naturally-aspirated, one-horsepower-per-cubic-inch, well-mannered street vehicle, that is quick off the line, can cruise at 85 all-day-long, never overheats, and has the injectors above the throttle plates. Apparently, the two-person consensus is that this sucks. Crap. It even gets good mileage. What was I thinking?!
I was wrong. I found a picture of the Delgado car on another thread. Butterflies above the injectors. Probably why it works as well as it does on the street.
Throttle body feed all cyl from one location. Where portinjection is for each cyl. Sent from my SM-J327W using The H.A.M.B. mobile app
There’s an awful lot of stuff, both factory and aftermarket that have the injectors above the throttle blade that work quite well. Yup you must be doing something wrong![emoji3] Sent from my iPhone using H.A.M.B.
Can it be done with the nozzle above the butterflys...sure. Is it "better" to have the nozzle below the butterflys...SURE. As said, there is no fuel bouncing off of the butterfly plates and shafts. Mike
My big block Crower has prevision to run the injectors above or below the throttle plates. I was told that you move the injectors about if running gas. Never have tried it yet though.
As I understand the OP question, I believe he wants to move the injectors a long way above the throttle plates. There is a pretty substantial difference between just above the throttle plates, and several inches above the throttle plates. Once the difference between the location of the injectors and the location of the throttle plates exceeds more then around 4", I think it would work much better if the injectors were closer to the valves, rather then farther away. But I'm not an expert either. Gene
My limited experience with moving nozzles around while on a dyno showed me that. Nozzles away from the valve worked best on gas. Nozzles pointing right at the valve worked well on Alcohol. Same engine and manifold, All of these were after the butterfly on a bug catcher kind of deal.
Speaking of nozzles. On the Flashpoint streamliner, Don Jackson built the injection system. It has 93 nozzles. 8 down nozzles in the heads. 8 in the intake manifold ports and the rest in the hat. Spray bar. Don makes nozzles that atomize the fuel much more that Hilborn type. Very trick and I would like to see how he machines them. Fuel pressure runs up to 400 PSI at high speed. Lots of boost from the 14:71 and around 60% got it to 451 mph so it can't be to bad. Be interesting to see how a more normal injector on gas would work on the street. Atomization seems eo be the issue,
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