Could Direct prot fuel injection cure knocking?

[Jared_80]

I have been doing reserch on direct prot fuel injection and I was thinking that it would be almost imposable for a properly timed system to knock. I am making reference to the DPFI systems that inject right onto the sparkplug near the top of the compression stroke. It seemes to me like the rate of injection could control the rate of the burn no matter what the cylinder pressure or temparature.

[ivymike1031]

um, aren't "port" fuel injection and "direct" fuel injection necessarily different?
* port injection - fuel is injected into the intake port
* direct injection - fuel is injected directly into the cylinder

Yes, it seems right to me that you cannot have anything but a relatively slow burn if you don't have a premixed charge. The reaction will be diffusion (or mixing) limited, so there isn't a possibility of simultaneous combustion of all the fuel.

[Jared_80]

I don't know why they named it that, but that is the name that they gave it. What would be the downside of using a system like this??

[Jared_80]

Any body else have any idea?

[bigol jonson]

fuel injection will NOT cure pinging there are reasons
a motor pings and as long as your compression and timing are correct among other things your motor should not ping i would also look at the egr but as for you hideously ridiculous question if you want an answer here it is plain and simple please for the love of god dont work on your own car as a mechanic i hate working on things the owner screwed up

[Jared_80]

Originally Posted by bigol jonson

fuel injection will NOT cure pinging there are reasons
a motor pings and as long as your compression and timing are correct among other things your motor should not ping i would also look at the egr but as for you hideously ridiculous question if you want an answer here it is plain and simple please for the love of god dont work on your own car as a mechanic i hate working on things the owner screwed up

For your information I am a certified mechanic, It was not a stupid question you were just too slow to understand it. You should not come to the tech forum, you are just going to get confused here, go home.

[ivymike1031]

Originally Posted by Jared_80

I don't know why they named it that, but that is the name that they gave it. What would be the downside of using a system like this??

Expense, limits of in-cylinder mixing (needs more swirl for one), requires higher injection pressure, allows less time for flame propagation and slower flame propagation. There are OEMs working on it, and there are some production vehicles that use it.

[cvcc_wagon]

mitsubishi has developed a direct injection engine, you can read all about it on this site . anyhow if i remember correctly it is computor controlled in such a way that when the vehicle is under load it injects during the compression stroke for better torque and when performance is needed it is injected during the intake stroke for better mixture, another feature they developed with this engine is a near viritical intake port to help the air and fuel swirl ds as it enters the cilinder.
read for yourself tho, its been a while for me

[454Casull]

Orbital has designed a system that doesn't require swirl in order to have an atomized charge. Very effective, IMO.

http://www.orbeng.com.au/orbital/orb...owpressure.htm

[Jared_80]

Originally Posted by ivymike1031

Expense, limits of in-cylinder mixing (needs more swirl for one), requires higher injection pressure, allows less time for flame propagation and slower flame propagation. There are OEMs working on it, and there are some production vehicles that use it.

Those are all things that can be worked around, do you know somthing that would be detromential to it?? What production cars use this kind of injection???

[Evil Result]

Originally Posted by 454Casull

Orbital has designed a system that doesn't require swirl in order to have an atomized charge. Very effective, IMO.

http://www.orbeng.com.au/orbital/orb...owpressure.htm

its say on #3 it injects air to improve combustion and emmissoins of NOx. wouldn't injecting air make the mixture lean there for increasing combustion temperature and make more NOx?

But since this involves EGR that might compensate for the temperature.

Anyways Direct Injection is the way to go.

[ivymike1031]

Originally Posted by Evil Result

its say on #3 it injects air to improve combustion and emmissoins of NOx. wouldn't injecting air make the mixture lean there for increasing combustion temperature and make more NOx?

But since this involves EGR that might compensate for the temperature.

Anyways Direct Injection is the way to go.

A leaner mixture won't necessarily result in increased combustion temps (in this case it probably doesn't).

[cvcc_wagon]

Originally Posted by Evil Result

Anyways Direct Injection is the way to go.

it seems as though it may be the way to go in the future, mitsubishi clames something like 10% more power than an engine with the same volume, and it opens more doors as far at tunablility goes as well. just my tho

[454Casull]

Originally Posted by Evil Result

its say on #3 it injects air to improve combustion and emmissoins of NOx. wouldn't injecting air make the mixture lean there for increasing combustion temperature and make more NOx?

But since this involves EGR that might compensate for the temperature.

Anyways Direct Injection is the way to go.

It doesn't say that it leans out the mixture. Where does it say that?

[Moppie]

The GDI Mitsi's are very common in Japan, and many models are now only avliable with GDI spec engines. They are becoming more common in new cars sales here in NZ, and in Europe, but the high cost of the engines in export markets still means they are not as common as they could be.

However, all the GDI vechiles Iv seen as used imports here in NZ have all been economy and familiy orintated, the closest thing to a performance model Iv seen is the short wheel base V6 Pajero.
However while not exactly quick, they are VERY efficant, my mother used to have a 1.8 Gallant which was quite thirsty for a small car, however two good mates have both recently got later model GDI 1.8l gallants, which use the same engine, but with a GDI head etc. They areproving to be very very economical even if they aren't that fast.



That Mitsi site is actualy very good, and goes into a surprising amount of detail (altough not a lot of detail for the engineers).
I recomend having a look starting at this page: http://www.mitsubishi-motors.co.jp/i...GDI/page5.html