Is it possible to convert our cars to use direct fuel injection or would we have to totally re-engineer the heads? I know you'd have to completely re-do the fuel system, adding a secondary fuel pump, and new high pressure fuel rails to reach the ~ 175bar(2,500psi) pressure needed to DFI, not to mention tune the system. I'm just asking if it's possible? I think this would yield higher all motor gains than anything short of increasing displacement.

 

It's not really possible.. aside from the obvious injector location and fuel pump issues you'd need to design a custom piston as well. A big problem with DI motors is erosion of the top of the piston from the extreme fuel pressure, thats why most di pistons have a "pocket" in the piston the injector sprays into.

DI helps most at part throttle, at full throttle di wont help much since it injects the fuel on the intake stroke just like you get from standard port injection. At this point its more of an economy/emissions thing.

 

Agreed not possible.

Direct injection is really a technology better suited to diesels and two strokes. There are problems associated with DI, like carbon build up on the intake valves, that do not make this technology preferable in a daily driven car.

Wadzii, I'm pretty sure that DI sprays the fuel in after the intake & exhaust valves have closed so that no fuel is lost to pulses in the intake and scavenging from the exhaust.

 

at part throttle you are correct, at WOT and high rpms where more fuel needs to be injected there is just not enough time to inject only while the intake valve is closed, injection has to start on the intake stroke.

The intake valve build is a problem, nearly all DI european cars have to have an actual service interval for intake valve cleaning.

 

Ok. My DI experience comes from my snowmobile background and the systems that are out there for the two-strokes are 100% fuel injected into the combustion chamber after the piston has closed the ports off (same as a valve closing if you're unfamiliar with a two-stroke). I applied it as a blanket knowledge. I find it shocking that they can't inject all the fuel after the valves are closed because they can do it on a two-stroke and there is a combustion event every time the piston reached TDC.

 

I always thought the performance advantage of DI, especially at very high fuel pressures ( > 200 bar) is better fuel atomization, leading to more precisely controlled A/F ratios. Also that the reason DFI uses such high fuel pressure isn't to overcome cylinder pressure so much as to make fuel atomization more homogenous in the AF mixture than possible with PFI.

I know our engines have little to do with F1 engines but the new power units are direct injected 1.6l turbo units, and they can spin up to 15,000 rpm, granted due to fuel flow limits they're doing max 12,000 rpm. I was reading about how Bosch has designed a new fuel pump for the Mercedes engine that outputs 500bar and that this ultra homogenous charge is worth 40hp when properly tuned, so it got me thinking.

http://translate.google.com/translat...20%26bih%3D963

http://www.dynotechresearch.com/blog...nYear=2013#298

 

Of course its possible. Just depends how much you want to invest in the engine development to convert it.

 

Pay to play...... who is in on this game then?