ktmracer21
smart a$$
i agree with the duration theory/not enough cool time in between...someone go kidnap a cummins engineer and a bosch engineer! lock them in a dyno cell!
CR melted piston discussion, why, why not, and for the love of god how not to..
- Thread starter bdp
- Start date
They run a ton of fuel to turn alot of RPM so that they can cool the motor down... The engines aren't even close to running clean.. They seriously roll coal..
There was a mudracer here that was running a diesel, and he actually talked about it for a little while. Was very interesting.. I think the CR's are not running "rich" enough yet...
Merrick
2007 5.9
West Coast Dyno Modifier
They can run lots of duration because they dont have 3 injection cycles.
I wonder if Marco can pull out the pre/post cycles and just run one main event and see what happens. I know he experimented with removing the pre cycle and lost power, but I ownder how it would run with one big event like the P/VP trucks???
I would think that with some time tunning it in, it should make great power and run fine.???
I know the D-Max guys can turnt he events off and on depending on set-up, maybe thats why they can run INSANE amounts of timing with no meltdowns.
Whats everyones thoughts about one big event???
XLR8R
Crew Chief
Essentially, pistons melt when the alloy's ability to shed heat is overwhelmed by the combustion event's rate of thermal impingement on the crown.
The re-entrant design of the 555 motor's injector/bowl is more efficient, IMO due to enhancing the diesel cycle's theoretical constant-pressure/delta-volume thermal energy profile.
Cummins did indeed "revert" back to that style combustion model for the 6.7Ls... and I bet they have all their ducks in a row!
Excessive fuel timing is the easiest way to melt aluminum, since more work is acccomplished before the combustion gasses can escape to punish the EGT probe. Worshipping a pyro is like relying solely on the airspeed indicator in an airplane to determine ETA... :badidea:
Heck, the EGT gauge on the drag truck reads very HOT, but that's because all the thermal coatings reduce energy conducted from the exhaust gasses.
A "timing guage" for these CRs is the best thing remaining uninvented.
The combustion efficiencies engendered by the high-pressure CRs are the reason why their piston alloys are tougher than for the VP & P7100 mills - to better withstand the increased heat input/absorbtion rate that comes with the power.
That's why water injection is such a benefit for common rails (no need for methanol if you're already overfueled) - it cools EGTs while increasing cylinder pressure curves, much like nitrous does on a properly-fueled SI engine.
The combustion chemistry is probably too much for this forum, but suffice it to say that the addition of water to the combustion event enhances power production in a few ways (four that I can think of).
Our drag truck got 70HP out of 12 nozzles worth of hose water while never clearing the smoke more than halfway...
The re-entrant design of the 555 motor's injector/bowl is more efficient, IMO due to enhancing the diesel cycle's theoretical constant-pressure/delta-volume thermal energy profile.
Cummins did indeed "revert" back to that style combustion model for the 6.7Ls... and I bet they have all their ducks in a row!
Excessive fuel timing is the easiest way to melt aluminum, since more work is acccomplished before the combustion gasses can escape to punish the EGT probe. Worshipping a pyro is like relying solely on the airspeed indicator in an airplane to determine ETA... :badidea:
Heck, the EGT gauge on the drag truck reads very HOT, but that's because all the thermal coatings reduce energy conducted from the exhaust gasses.
A "timing guage" for these CRs is the best thing remaining uninvented.
The combustion efficiencies engendered by the high-pressure CRs are the reason why their piston alloys are tougher than for the VP & P7100 mills - to better withstand the increased heat input/absorbtion rate that comes with the power.
That's why water injection is such a benefit for common rails (no need for methanol if you're already overfueled) - it cools EGTs while increasing cylinder pressure curves, much like nitrous does on a properly-fueled SI engine.
The combustion chemistry is probably too much for this forum, but suffice it to say that the addition of water to the combustion event enhances power production in a few ways (four that I can think of).
Our drag truck got 70HP out of 12 nozzles worth of hose water while never clearing the smoke more than halfway...
XLR8R
Crew Chief
Joesixpack
Pull'n it.
Pressure brings on alot more advance then we think, if you don't think so, go out and unplug a fca......
2007 5.9
West Coast Dyno Modifier
Guess I dont get it....:redx:
So running a CR like a Vp/P/VE with one injection event per cycle wouldnt work???
Joesixpack
Pull'n it.
2007 5.9
West Coast Dyno Modifier
No reason at all why it wouldn't work, got the software handy?oke:
No, just thought that its an idea that Marco might see and play with.
If he could find a way to make it work, that might solve some of our problems.
jlibert
New member
after looking at my pistons, the spray pattern, and where the melting occurred, I agree.
Same thing i said in the other thread. The 12v's are alive at high rpms. Maybe there's a difference between cr and 12v that allows one to live.
:bang Dammit. I finally figured out why my cross country eta's are off. Damn wind.......
Really though ---- the pyro is probably the most worthless gauge on my truck.
-jp
chrleb1
Charlie Brown
Someone is catching on......
chrleb1
Charlie Brown
Guess you don't like spinning big turbos easily....
Pilot injection lets us spin bigger turbos easier on a CR than a 12 valve.
Begle1
Active member
I'm not sure how the math would work out on that.
A pump-to-nozzle engine delivers fuel over several degrees of crankshaft rotation, and the injection pressure starts at pop-off pressure, ramps up to a peak pressure a few times higher than pop-pressure, and then drops to a little bit below pop-off pressure.
How does a common rail engine, even with it's multiple injection events, compare in degrees of injection? I imagine that is has almost nothing of the pressure ramp-up and ramp-down, so it doesn't need as many?
The inefficiency of an injection pump engine, in the way it varies injection pressure over a wide range with every injection, helps to cool combustion by mildly hindering combustion at the lower pressures. I don't think that CR's have those lower pressures.
But it's bass ackwards to lower combustion temperatures by reducing combustion efficiency. EGR should work great to lower combustion temperatures, otherways. It's not really that bad to have problems with fuel burning TOO well for once.
