Taking the Pressure to the Max

[JeffMcKC]

Re: Taking the Pressure to the Max

here is a different one http://www.youtube.com/watch?v=AKyP1...eature=related

Think if they would really wind that thing up LMAO :o Now if I could just get my stuff to turn that high ;)

[70.5CAMARO]

Re: Taking the Pressure to the Max

My high compression, aluminum headed, solid roller cammed, gear driven Duramax has a fuel rail pressure of 26,000 psi! That will make it atomize!!
Scary to even think about.

how do you even contain 26000 psi. burst pressure on most lines on a durimax wouldnt even begin to hold that.

[dieselgeek]

Re: Taking the Pressure to the Max

My high compression, aluminum headed, solid roller cammed, gear driven Duramax has a fuel rail pressure of 26,000 psi! That will make it atomize!!
Scary to even think about.

how do you even contain 26000 psi. burst pressure on most lines on a durimax wouldnt even begin to hold that.

The "fuel rail" is located inside the cylinder head. The pressure isn't stepped up to 26,000psi+ until it passes through the high pressure pump which feeds that rail. Crazy, isn't it?

I know a couple guys that worked on a standalone engine management system for common rail diesel engines (gov't project), they told me that when you are testing and things go wrong, you break all kinds of expensive stuff at those pressures.

[JeffMcKC]

Re: Taking the Pressure to the Max

Ford does the same thing we are at 2200psi

[joe_rocket45]

Re: Taking the Pressure to the Max

here is a different one http://www.youtube.com/watch?v=AKyP1...eature=related

yea, look at the difference between the two, carbon fiber to aluminum intakes (which means little) but more specifically how the first one I posted has a better plume and vaporization while the second video you can see the fuel sticking to the throttle bodies.

I bet this is not only from better E-management & injectors but also from a higher fuel pressure.

It is interesting to note that they have pulled the injectors as far up the intake track as possible to the point reversion just barely allows the fuel to spill over the top on the second video and it was tuned to nearly perfection on the first video. Man, I'd LOVE a job like that :D

[70.5CAMARO]

Re: Taking the Pressure to the Max

i guess that why you cant even start a ford or dodge in the winter if you didnt plug it in, and the chevy fires first touch of the key.

[Rendid]

Re: Taking the Pressure to the Max

My understanding is that there isn't much more atomization to be had (for gasoline) at existing MPFI pressures. The reason Direct INjection setups are so high pressure (gas AND diesel) is because the time window available to inject the fuel is a LOT shorter going into the combustion chamber, than it is when spraying it into the intake.

I thought it was because the fuel has to fight combustion pressure in a direct injection setup.

[dieselgeek]

Re: Taking the Pressure to the Max

My understanding is that there isn't much more atomization to be had (for gasoline) at existing MPFI pressures. The reason Direct INjection setups are so high pressure (gas AND diesel) is because the time window available to inject the fuel is a LOT shorter going into the combustion chamber, than it is when spraying it into the intake.

I thought it was because the fuel has to fight combustion pressure in a direct injection setup.

That's another part of it, but if you look at the combustion ratio and atmospheric pressure, if you only had to maintain the same (roughly) 40psi differential that a typical port injected EFI setup runs, you'd end up wit more like 600psi on the diesel. The big issue is, you no longer can have the injector open during the exhaust stroke from the previous combustion cycle, when the injector is in the combustion chamber you only have a small portion of a stroke - less than 25% "duty cycle" - to inject all the fuel for that combustion event.


There's a really good explanation of all this in the "Bosch Automotive Handbook" - it's a great read for $35 and has hundreds of pages on both gas and diesel direct injection systems.

[dieselgeek]

Re: Taking the Pressure to the Max

i guess that why you cant even start a ford or dodge in the winter if you didnt plug it in, and the chevy fires first touch of the key.

I have a 10-year old Cummins/Dodge and have often started it in -10-20F (not windchill) without plugging it in. The block heater is so the oil pressure builds faster. The old story about diesels not starting in the winter is more based on fuel quality than the engines themselves.

[70.5CAMARO]

Re: Taking the Pressure to the Max

I used to own a few diesels, none of which would even think about starting i na a michigan winter if i forgot to plug them in. They would straight up say f- you. It would always take ether or have to plug it in for a few hours.

[dieselgeek]

Re: Taking the Pressure to the Max

what engines were they? let me guess: 6.2 GM, and early 6.9 or 7.3 ford?

[70.5CAMARO]

Re: Taking the Pressure to the Max

well yah, I assumed that the block heater was always to keep the coolant warm as well that way the combustion chanber was at a decent temp to start with.

[GibTG]

Re: Taking the Pressure to the Max

No big discoveries waiting to be made here..

The first thing that came to my mind was the fact that there wasn't much in the way of fuel quality to gain because the atomization I'm sure was already very fine to begin with (meaning atomization was already very good with an injector at 40, 50, or 60 PSI). Since there would be no significant gain in fuel quality, there wouldn't be any means to run a leaner mixture so mileage really wouldn't be improved. The pulse width will not directly affect mileage, the mixture ratio will.

[CDMBill]

Re: Taking the Pressure to the Max

True to a point. The new Car & Driver (yes i read other magazines besides HR) reports tkat the new Porsche 911 engine is direct injection, 1460 PSI and the compression ratio is 12.5:1! The fuel atomization reduces the combustion chamber temps enough to alllow that compression on 91 octane improving efficiency as higher compression has done traditionally. So at the same displacement there is reportedly more power and better fuel economy to boot.

[dieselgeek]

Re: Taking the Pressure to the Max

I think it's less the effect of cooling in the combustion chamber, and more the fact that the engine can't detonate or preignite when the piston is on it's way upwards in the cylinder, since there's no fuel in it yet, that lets them get away with the high compression on junk gas.

Inject the fuel a millisecond before you light the spark and who cares if it ignites itself? they say something about this in the Bosch handbook, it's wildly interesting reading!