330cc and 430cc STANADYNE HEAD AND ROTOR

[Jake S.]

My three stickers look just like Mel's do, but say 175hp

 

[kas83]

whats the reason for pullers running such high timing, in diesel power mag, there was something on a cummins and the was talking about running 50 degrees timing on a 1200+ puller

Cuz Diesel Power is the bible for diesel performance, and should be taken as gospel that they are right?


The truck in question is a P-pumped Cummins, which has a SET timing amount, no matter what the RPM. It doesn't advance or retard timing like a rotary pump does, it's not variable. Say the pump is timed to 30* BTDC, the injection event happens at 30* BTDC at idle, 2000 rpm, 4000 rpm, and everything in between.

50* timing, really? I'll have to look that one up. I wouldn't doubt it tho, if it's a 6,000+ RPM sled puller, it needs that kinda of timing to still run and make power at those RPM's. And BTW, I GUARANTEE that thing starts on ether, no matter what the temp is outside, when the engine is cold, and I'll put money on it.

Quit comparing a direct injected, higher injection pressure engine to the IDI.

 

[jhnlennon]

The reason a direct injected motor will start with lower compression is cuz they spray the fuel DIRECTLY at the piston where temps are highest rather then being sprayed into a pre-chamber where its cooler.

 

[kas83]

The reason a direct injected motor will start with lower compression is cuz they spray the fuel DIRECTLY at the piston where temps are highest rather then being sprayed into a pre-chamber where its cooler.

And they have higher injection pressures for better fuel atomization. Broken record anyone?

 

[jhnlennon]

And they have higher injection pressures for better fuel atomization. Broken record anyone?

I think the higher injection pressures have more to do with over coming higher cylinder pressures from higher boost amounts then with starting, and to make sure the fuel is atomized rather than puddling on the piston top. Atomization has more to do with the injector than it does the pressure.

 

[kas83]

Atomization has more to do with the injector than it does the pressure.

Atomization has everything to do with the pressures, as higher pressures allow a finer mist when sprayed through the injector nozzle. That's why a CR at 26,000 psi has a better atomization than at 19,000 psi, generic numbers and example. Mel will chime in here I hope.

Better atomization, or a finer mist, will allow the fuel to ignite easier in the compressed air, even if the temps aren't as high. This statement holds true in our lovely IDI's, and can be proven by the hard starting people run into with worn, leaky, or unbalanced injectors.

 

[jhnlennon]

How much does atomization affect an IDI considering that the fuel gets sprayed into a pre chamber anyway??? Wouldnt that negate the affect of atomization once it hits the prechamber walls and the fuel molecules re-combine? I have never really noticed ANY difference in starting in my IDI's when it came to injectors. New ones, old ones didnt really make a difference in starting, just grey smoke. In my opinion cold starting has more to do with cranking speed than anything in these old IDI's.

 

[kas83]

How much does atomization affect an IDI considering that the fuel gets sprayed into a pre chamber anyway??? Wouldnt that negate the affect of atomization once it hits the prechamber walls and the fuel molecules re-combine?

With the proper pattern, the fuel spray shouldn't touch anything other than air, and have the flame front travel out of the prechamber, since the fuel is ignited by hot air, and not metal.


My arguement was the DI advantages, not the IDI negatives.