Don't get me wrong, I'm super stoked that you guys do all this testing and publish numbers! I was just trying to work out in my head what the mechanism is to make more power on the same fuel.

1. Better atomization = higher volatility.
a. More fuel available to actually burn. Less energy required to get through the big drops. Fewer HC's out.
b. Burning happens faster thru quicker flame propagation. Less timing needed for a given BMEP profile.
2. Possibly better charge cooling due to increased fuel evaporation? Profound on DI applications.
3. Better injectors are just more consistent cycle to cycle, bringing average (measured) power up.

Might be interesting to read:
http://www.asnuinjectors.co.uk/tech/atom.pdf

 

I wonder if for a given fuel pressure there is more kinetic energy being introduced into air stream, what F1 does with ITB injector placement more or less. I will have to read up on that link.

 

One challenge I have with rationalizing the improved atomization is that the injectors are spraying all over the IM runners and back of the valves. I would think that much of the improved atomization would be lost or neutralized due to that effect, especially at high IDCs where the injector is spraying pretty much all the time. And it also seems easy to imagine that in-cylinder temperatures are pretty effective at vaporizing the fuel charge which would lessen the need for a highly atomized intake charge. But there's no arguing the numbers.

 

I just poked around some SAE papers and in summary, there's a "fuel preparation rate factor" which is well correlated to the square of the injection velocity, which is the "kinetic energy" of the fuel. They state that this is the dominant factor in determining fuel-air mixing rates. More so than swirl, tumble, squish or quench.

It also reminded me that particle size is largely driven by fuel pressure. A potentially interesting test would be to significantly up the pressure on a smaller injector to get the same effective injector capacity as the new 1050, and see how they compare. Obviously you'd be pump limited much sooner in the real world though.

The F1 guys are turning their motors a little faster so physics get real interesting. I've seen intake ports and cam profiles for CHAMP cars and they really look funny. Very long durations and low lifts.

Totally on & off topic: it seems OEM's may include fuel injection volume in their SD calculations. Might be something for the smarty-pants programmers to look into.

 

In the SAE stuff, wall wetting is a big issue. It seems lots of time is spent picking the injector angle to maximize shear. They also try to minimize the thickness of the wetted layer, and "bounce" the stream back up.

 

Did that with my FIC1100s. Going from 44 psi base to 58 psi base netted me about a 10% increase in mpg and better off boost power, but I didn't pick up any significant power at WOT that I could detect in my road tuning sessions.

 

Just because the AFR is the same in the exhaust doesn't mean the same amount of fuel was burnt in the combustion chamber at the ideal time. I imagine every combustion event is more consistent, thus increasing the average output and more fuel gets burnt in the chamber instead of burning after the exhuast valve is open.

Mrfred, for half the cycle you could be right. But the intake valve is still open for a decent period of time where better atomization could still have a signifigant impact. Makes me wonder what might happen with a large enough injector that maintained excellent atomization with proper injection timing. 20HP here with the spray running into a closed valve for more then half the time...maybe 40HP if the injector is operating in that "ideal window."

Either way, as a purely subjective assesment, I noticed the ID1000s seemed to give the car a smoother power delivery over the stock injectors at WOT. Smoother usually means more power from my experience.

 

I understand what you are saying but would you even see that in injector duty cycle? I think I have the logs (lappy accident) or can get them back to see what the difference was between the duty cycle of the 1100 and 1050.

 

any word on the release of big boy injectors Aaron ?

 

The better the spray/atomization, the more power there is to be made. They look like great injectors for sure.

I personally will be going with 235lb (just short of 2500cc) Moran Billet atomizers. They have low imp as large as 5250cc (500lb).

https://www.moranmotorsports.com/cat...er-injectors-0

 

isn't the intake valve open for something closer to 1/4 of the time? i do agree with your idea of using a monster injector to spray fuel only when the intake valve is open. kinda makes me want to run some fic2150s. another aspect that sounds kinda interesting is getting control over injector phasing. maybe i need to go looking for that...

 

Injector phasing control would be pretty cool. Then we could bump the injectors farther back in the runners and try to make some more power

 

Im going to have to pick up some of these 1050SP's for sho!

 

I don't know of a documented case where GDI was applied and all else stayed the same, but that's where you're going with this...

This seems to be a good paper covering the benefits:
http://www.sciencedirect.com/science...60128599000040

 

I would say direct injection would be the next step up from a big injector timed properly. There is more to GDI then just the timing. There is a GDI head for the 4G motor though, it would defintiely make a cool science project to compare.

Aaron, yeah, my thought is you would see no change anywhere except for power output. You are still injecting the same amount of fuel and ingesting the same amount of air. Only difference is the fuel mixture is burning faster and more completely before the exhaust valve opens. The fuel gets burnt either way thus the registered AFR is the same, it just relative to where the piston is at in its mechanical efficiency point would be the difference. I suppose you might see lower EGTs as the combustion event is more complete by the time the valve opens. It’s a thought anyway.

MrFred...DOOOO ITTT!
Ha, although I know that would be a pretty difficult task as some of those main interrupts are difficult to follow.