I was just thinking, what if you got rid of your throttle bodies all together. Heres what im talking about, you just have the flanges sticking out, and you have the fuel injectors as close to the engine as possible. Then to control how much power you put out, instead of restricting the intake (ie throttle body) you only inject fuel every so many rotations. So even tho all the air is going in and the spark is going off it wont ignite anything. I think this could make more power because of no intake restriction. And could possibly be more effecient because the engine is always igniting at WOT conditions, so the compression ratio is high.

Tell me what you think

 

It's called stratified charge direct injection, except the fuel is injected during the compression stroke. Mazda has had amazing success with SCDI rotaries placing the DI injector about 15 degrees above the trailing spark plug. This controls power by controlling fuel supply, and would offer much finer control over power delivery at low RPM.

It's a good idea, tho.

Brandon
BR7 Racing

 

that'd run incredibly lean as far as I can tell.

 

hey no7yet since im taking out all my oil injecting gear, and running premix, do you think the place where the oil is injected would be a good place to inject fuel into the compression stroke?

Also, is there any ecu out there that could handle this fuel injection requirement?

hmm i just did a search on direct injection and it seems it has a problem with emmissions, so maybe having an injection system similar to what was used on the r26b would be better.

 

The oil injectors are not in the compression stroke. Unless I am retarded. Which is possible.

 

who really knows where the intake stroke ends and the compression begins


hmm running premix could be a problem with this setup because when no fuel got injected no oil would be either. UT OH

 

...that's easy: between 40*-80* After Bottom Dead Centre, depending on what motor, and at what level of rpm... in a turbo on stock ports, it's 50*... in a 6 port motor, it's like 40* on the primaries, and 80* on the tertiary ports (which is pretty neat, as the next cycle opens up before the tertiary port closes fully)...

once reversion is impossible, you can definitely say the compression stroke has begun.

 

This won't work. At low load only a tiny amount of airflow is required compared to WOT. If only requires 3-4hp to push a car along at low speed (~30mph). To do it your way, the injectors would be firing only once every few hundred revs. Because petrol engines require mixtures within a very specific range, an unthrottled engine would need a large injection of fuel for each cycle. So instead if getting a continuous stream of very small bangs, you'd get very big bangs spaced widely apart. This would result in an unacceptably rough running engine.

 

Direct injection still requires a throttle.

 

Probably not, but the big problem is not the electronics but the hardware. DI requires completely different injectors and pumps because the fuel pressures used are much higher, ~1700psi compared to ~50psi for indirect injection. At the moment DI is completely beyond the reach of all but the big manufacturers. On the contrary, one of the features of DI is low emissions. There are quite a few engines available with DI and they all have better performance, economy and emissions compared with equivalent engines indirect injection.

 

i see this done on ae86 all the time. its pretty neat. i was also wondering if it could be done on a rotary.

 

AFAIK - when you go premix, oil isn't a issue, at all. Don't you block off where the oil should be going? Well, what a former member here did to his base (billy)... but I still could be retarded as well

 

Ah no, I don't think so...

 

No i was saying with my idea of injecting only every so many cycles instead of using a throttle there wouldnt be oil injected when their wasnt fuel injected.........see?

 

NZ just explained it. What you are trying to do is the equivalent of DI. You would not have enough fuel pressure to do what you are trying to do. Also there is a reason cars have throttles. I have a paper on DI somewhere, I'll try to dig it up.

 

Stratified charge direct injection doesn't necessarily.

See NASA CR-165399 "Study of Advanced Rotary Combustion Engines for Commuter Aircraft", M. Berkowitz, C. Jones, and D. Myers.

Specifically, "The direct injected unthrottled rotary engine is the only stratified charge engine variation which can operate as lean as a diesel, and achieve automotive diesel fuel efficiency levels." (emphasis added)



Brandon
BR7 Racing

 

Ah, but aero engines operate mainly at constant load. A car engine must be able to constantly vary it's load, and run smoothly at low load. You need to be able to vary the airflow to do that.

In the more relevant example of an automotive 13B, you need a throttle.

 

Am I the only one boggled by this thread? Man this forum is stuffed with amazing mechanics and engineers...too bad I am not one of them!

Keep up the good work!

 

In aviation applications you've still got to be able to vary torque output to compensate for varying conditions such as takeoff and idle. Granted, revs don't change much, but it's varying torque output that's the important part. At idle speeds (in one case, about 1400 RPM) meaningful data were able to be collected at an output of about 10 bhp (though BSFC went waaaay up) indicating (at least) minimally-acceptable run characteristics.

In any case, it's not required.

Brandon
BR7 Racing

 

I'm not disagreeing with you, I'm just saying that it would not provide a suitably smooth-running engine for automotive use. This is a car forum remember...

 

what do u mean no? look at a ae86 in 2nr or ss magazine, most likely it will not have the tb.

 

You're not talking about engines with carbs instead of EFI are you?

 

what you are describing is exactly how a diesel engine works.... no TB. always at WOT.

 

A diesel can run with a wide range of mixures, which is how power is adjusted (more fuel = more power), but a conventional petrol engine cannot do this.

 

so is this the same as the DI in v dubs?