zjbarra

iTrader: (2)

Similar to this topic, I had a question. When you run the stock injectors on a turbo 2 for primaries, I think Henrick was saying you get surprisingly high injector usage %'s. If you ran 720cc injectors in the primaries, would this be a problem? I could see 1600's being harder to do this with, but if you were to put a 3" full exhaust and do port work to your engine and manifolds, it would seem that even on the stock turbo you'd get some pretty high injector usages. Is this an actual problem to worry about or is it just a bad idea?

Slacker7

iTrader: (2)

When I said that about the velocity stacks I meant that the injectors were placed as far away as possible. Same case for honda bikes

oregano

iTrader: (1)

"When I said that about the velocity stacks I meant that the injectors were placed as far away as possible. Same case for honda bikes"

oops... guess i got it all wrong then eh? sorry dude.

1987RX7guy

iTrader: (3)

Theres probably a sweet spot for it all.

Slacker7

iTrader: (2)

Err no problemo

I stole this picture from somewhere..
the 2ndary injectors are wwwaaay at the top of the airbox *intake manidfold* and the primaries are below.

andrew lohaus

i think the "sweet spot" is related to the rpm of your powerband with a higher rpms needing injectors further upstream. like ted said. the primaries are probobly already right where they need to be for the stock application. now on a high rpm race project this might be a different story.

oregano

iTrader: (1)

ahhhh. i see. interesting. maybe high velocitty air helps to seperate droplets? oh well. first gotta get my baby on the road. then i can get creative...

NZConvertible

I know what an LTX is. Like I said, "If you're running an aftermarket ECU..."

Felix Wankel was a trained and experienced engineer. He got his ideas from a very different place...

Seriously, things like injector placement are the sort of things that teams of highly qualified and experienced engineers take many months of experimentation to decide on. If you look around at other highly modified cars you'll see that in every case of the stock manifold being used, the injectors are still in the stock location. That should give you some clues. If there were advantages to moving them, someone with a helluva lot more know-how would've done it a long time ago.

And for those who say "don't knock people for thinking of new ideas", this is not a new idea. The reasons for not doing it were established a long time ago.

Slacker7

iTrader: (2)

Yeah... Supposedly from a dream when he was 17 years old. He must have been one outstanding 17 year old.

Part and parcel of innovation/invention you get an idea ask around if anyone else has thought about it. If no then submit your idea to the patent office. Pay ridiculous amount of money for patent search. If no current patents exists you then pay a miniscule amt for the patent

1987RX7guy

iTrader: (3)

That looks like different injector pistioning to me.

I guess someone thought about it then eh?


Santiago

PS- I think I just fell in love with those intake manifolds. And the have a turbo plenum to add to that IDA setup

andrew lohaus

nzconvertable, you dont need to get in such a wad over stuff like this. its a plausable geustion and now he's getin some answers. sure the answers not "yes, its a good idea" but thats the chance ones takes. nothing wrong with that.

sunrotor

Long ago I learned to think before I spoke.
I get ideas all the time. They mostly come from applying my education and experience to a new situation. Then I try to think through my "idea" and see where it takes me. This is sometimes called visualization. There are other less kind terms for it as well. If I can state my idea with a "how it works" backing it up, then I feel safe in running it up the proverbial flagpole.
But this thread is about injectors.
If putting the injectors as far from the combustion chambers was good, everybody would run throttlebody injection, cause its cheap..., and cause nothing beats cheap AND good!
So there must be an advantage to port injection.
Let's look at what the OEM set-up is and try to understand why.
Primaries are small and close to the combustion chamber. Secondaries are big and far. What else do we know.
Primaries are for part throttle, low rpm and secondaries are more for WOT and only work above 3500 rpm.
At 3500 rpm in 5th gear, I'm ticket bait, so that isn't a continuous operating condition, but only a transient condition.
AT idle, the butterflies are closed, air is barely leaking into the engine, a high vacuum exists, and the air mass and air velocity are LOW. The period over which the intakes are open is 5 times that at which the primaries kick in and 10 times longer than when I redline. So when I spray fuel now, it just responds to gravity and falls down. To maintain any kind of idle, I'd better spray the fuel into the combustion chanber, or it won't get there. This is why a PP can't idle for squat, to much cross-section in the manifold runners, so low air velocity doesn't keep the fuel suspended in the air. We have all read about how big ports cause a loss of low end power. This is part of that, as well as reversion caused by low intake velocity (caused by the compression stroke starting before the intake closes), and exhaust-intake ovelap causing dilution of the intake charge from exhaust gases.
At 7K, I got that rotor sucking gobs of air and I have little time for the injector to pump the fuel for each charge. The more HP I've set the engine up for, the more fuel I gotta deal with. I want all the help I can get to mix the air and fuel.

Sooo, if I switch them around, what will happen.
At idle\below 3500 rpm operation, only the primaries, located way up the manifold, will operate. A lot of fuel will seperate from the airstream. Paul Yaw says it well in his tech articles:"The biggest contributor to poor atomization is low inlet velocity. While this is much more of a problem with carbureted engines, fuel injected engines will also suffer from poor atomization if inlet velocity is excessively low. In the case of modern emission controlled engines, the injectors are placed as close to the combustion chamber as possible to reduce fuel "drop out" as the mixture travels from the injector to the combustion chamber."
OH, and at the higher velocity of the air at high rpms, the relative distance becomes relative less significant than the distances at low rpm operation, so the low rpm operation will establish the proper positioning of the injectors.
Sorry it was sooo long, but I hope this puts an END to this one.
Flame on

1987RX7guy

iTrader: (3)

VERY nice.

RETed

http://www.thecarricos.com/ACRE/

Check out: 4-rotor-6-11.pdf

Although it's on the R26B, they talk about fuel injector positioning on the engine and their conclusions.

There's a lot of cool stuff in there, and like 3 or 4 SAE papers.
There's also a whole FSM (FD?) there too.


-Ted

andrew lohaus

thanks ted

NZConvertible

Does that look like a stock manifold to you? Ah, no... Were my comments about the stock manifold? Oh yeah, they were.

Those injectors are positioned there because it's a convenient package of throttles and injectors, not necessarily because they're the best place. That should be obvious. Programmable EFI will let you adjust injector phasing to suit that location, but that still doesn't change the fact that at low port velocities closer is better. That's why the primary injectors are located as close to the ports as possible.

Another thing nobody's mentioned, at light throttle the secondary ports don't even flow any air (throttles are closed), so firing only the injectors in the secondary locations would result in the engine not even running.

I think we can put this idea in the bin now.

oregano

iTrader: (1)

that manifold is so hot rxyguy.... im ******* drooling. i hope one day i will be able to manufacture something like that.

Aaron Cake

iTrader: (1)

Thank god this topic turned into something worthwhile...I was about to hit the "delete" button after I read the topic...

BTW, I am using those IDA manifolds in a 12A project I am doing.

1987RX7guy

iTrader: (3)

N/a or FI? Also what kind of air horn setup are you going to use for the 12A? I really want to look into the turbo plenum offered by "tweakit" But I want to get the throttlebody setup from TWM without air horns if possible(to save money) because the turbo plenum doesn't use air horns per say.

Got any thoughts Aaron?

Aaron Cake

iTrader: (1)

Sorry, but I can't get into a lot of details. It will, however, be NA. I will be using those wonderful air horns as shown in the picture above (that is exacty the intake I am using).

1987RX7guy

iTrader: (3)

Come one give us all the juicy stuff man.

Where did your IDA's come from? what company?

projekt

15th century water pumps?

1987RX7guy

iTrader: (3)

RacerXtreme7

iTrader: (2)

I didn't get through the entire thread, so if I missed something and re-peat sorry. It just reminds me of the air pump supercharging.

Further placement of the injector from the port = better full atomization (or dispersion, it actually doesn’t atomize). This is not a theory, but proven fact in most cases. This works only at high rpm were intake velocity is high. At low rpm the fuel falls out of suspension and wets the intake walls being inefficient.

Smaller injectors atomize (disperse or mix with air) fuel better then larger ones do.

NOW, with all that being said, common sense should dictate injector placement. Primary close to the port to avoid "wetting" the runner walls due to low velocity low rpm, smaller injector for primary for better idle, throttle response and emissions (do to better atomizing from smaller injector (dispersion). Larger injectors for secondaries (larger injectors for the larger demand of fuel (higher rpm and or boost) further away from the port (better atomization do to higher intake velocity (high rpm / boost).

I welcome innovation, but there’s a line between a great idea and just plain stupid. I'm not calling anyone stupid, but people who have an idea and don't listen to other who know more or are smarter or have more experience.. their just plain stupid. Learn from others who already know or go the hard route and learn your self. But this isn’t (and neither are any other stupid past ideas from here) a newly found perpetual motion machine or flux capacitor. Its stuff thats been studied or is so common sense doesnt need to be. I know sticking my hand on a burning pan will hurt, I don't need to try it to veryfy it hurts. But here’s the funny part..... a lot of these "stupid" ideas are from people not intelligent enough to test it correctly or get any sort of evidence to prove for or against it. My $0.02, hope non are offended

~Mike...............

Piranha

15th century water pump.... last I checked you can't compress water. How is that even a joke, or funny?

Yeah, this is pretty ridiculous. No one brought up this.

Uhhh... PORT SIZE????? Your primary ports are smaller than your secondaries. Where do you think more air is going to flow through (and need more fuel...)?

I thought this was pretty elementary.