DS4 max fuel rates at X rpm

[SmithvilleD]

Does anyone have any documentation on DS4 max fuel rates at different rpms?

Say 2000, 2500, 3000, 3400 rpm?

I've heard the DS4 max rate is 89 mm3 @ 2000 rpm, but more like 70-75 mm3 @3400 rpm.

I'm trying to get a better understanding of what the practical limits of the common DS4 & aftermarket chip. I understand the fueling tables in the chip will dictate what the PCM calls for. I'm assuming the practical limit is the pump itself.

If anyone knows of a good reference on the DS4 capabilities, I'd love to hear about it.

 

[Missy Good Wench]

I have been told that the DS4 has a limit of about 92MM of fuel.
This is likely the limits placed on things by the mechanical parts.

The latest and greatest DS4 along with the tweeked up tricked out chip from Heath are supposed to get near this point.

The chip/ecm can be reprogramed to just about anything you want to stuff into the thing up to the limits of the IP itself.

The Plungers it would seem to me would be the bottleneck.

The Marine setups that Peninsular builds use either custom DB2 or DB4 Pumps to get the high HP that they advertise.

The DS4 is pretty well all in and done up near 90mm.
Considering that around 68-70 is around stock its not bad at all..


Not sure how the aftermarket chips have the fuel maps set up.

I have a Heath chip in the DaHooooley and it seems to dump enough in to make plenty of Black Smoke even with the Turbo master tightened down a fair bit.

You know, I would give Bill Heath a call and chat with him about this stuff. He is the Guru on the 6.5's when it comes to fueling with a DS pump.


Missy

 

[kojo]

Plungers travels same distance at all rpm's so pumps mechanical ability to pump should be same at all rpm's. Only problem is how to get enough long pulse to solenoid

 

[SmithvilleD]

Plungers travels same distance at all rpm's so pumps mechanical ability to pump should be same at all rpm's. Only problem is how to get enough long pulse to solenoid

This is why I'm wondering what the real world fueling limit at 3400 rpm/redline is?

All the specs I've read including marine pumps show a somewhat lower rate for the highest rpm.

My guess is, it's the same as one big reason why all engine's torque curves fall off at some point, as rpms rise. Less & less time the valves are open. Less & less cylinder fill, so torque per pulse goes down.

 

[schiker]

Lets clarfiy a bit becasue this is a good question and leads to the often debated injector arguement.

A pump's output is usually stated in 92 mm^3/1000 strokes. And this is max capable. Is that 1000 revs of the IP and 500 crank revs ? But the fuel map or table is the PCM control of injection event. It monitors ECT, IAT, RPM, and APP. Then its suppose to control boost and fuel delivered to produce power and control emissions/economy/driveability/safety.

So everyone tweaks the table to thier tune of boost and safety margin for heat and the pumps ability to physically inject fuel in the aloted time AND the fuels ability to combust cleanly in the aloted time as the piston sweeps up and over TDC and down towards BDC. Also cleanly means with the right ratio of air so it doesn't burn too rich and build too much unproductive heat.

Injector orifice, timing, and boost are huge variables and makes quite a difference between 1700-1800 rpm vs 3300-3400.

So we probably need to know injectors for number comparisons.

I'll bet truck injectors limits the ability of the fuel to combust quickly enough at above 2800 rpms for optimal combustion AND maybe moreso to insure peak injector line pressure is not exceeded. Vs marine injectors that might perform better at higher rpm or allow the pump to inject the fuel in the faster time without as high of injector line pressure.

 

[schiker]

I don't think its an air shortage at upper rpm. I think its a peak injector line pressure limit and how well the fuel combusts.

What is so hard is the injection isn't as variable like common rail. And its one big ole trade off on the power band/emissions/heat/drivability/idle quality etc.

 

[Matt Bachand]

Lets clarfiy a bit becasue this is a good question and leads to the often debated injector arguement.

. Vs marine injectors that might perform better at higher rpm or allow the pump to inject the fuel in the faster time without as high of injector line pressure.

But don't marine injectors have a higher pop pressure, meaning it would increase line pressure before popping?

If line pressure increases considerably at higher RPM's (Does it?) Then I could clearly see the benefit to running high pops/marine's for higher RPM performances.

Or does line pressure decrease, as there is less time to pulse fill? Keep in mind fuel pressure is usually down too at extreme rpms, does the combination of this have any effect on the chambers ability to fill completely?

Wouldn't that result in less pressure?

Wouldn't low pop injectors open faster?

You would think at real high RPM you would want a little more advance?

 

[schiker]

Pop pressure is just opening pressure.

Peak line pressure comes from flowrate vs nozzle size.

Crude comparison

So if you have 1.3 MM^3 that has to go through a 0.010" ?? diameter hole in 0.14 seconds (estimated stroke as piston stroke time) at 1700 rpm

Vs.

2.6mm^3 that has to go through same 0.010 hole in 0.07 seconds at 3400 rpm.

That is 2 different flowrates at same orifice so line pressure must be higher at higher rpm because the flowrate is higher at higher rpm same orifice.

Someone else have more realistic numbers or better way of saying it? I more than likely made a math error.

 

[schiker]

Maybe why feeding the beast helps at high rpm/high fuelrates there is less recirculation in the fill/spill chamber of ip and shorter time??? Feed the beast does seem to help at higher fuelrates especially.

Timing would have an affect on start of injection event and total elasped time availiable, pop pressure would also affect timing. Its all related and has to be tuned to work best together.

 

[schiker]

Pop pressure is just opening pressure.

Peak line pressure comes from flowrate vs nozzle size.

Crude comparison

So if you have 1.3 MM^3 that has to go through a 0.010" ?? diameter hole in 0.14 seconds (estimated stroke as piston stroke time) at 1700 rpm

Vs.

2.6mm^3 that has to go through same 0.010 hole in 0.07 seconds at 3400 rpm.

That is 2 different flowrates at same orifice so line pressure must be higher at higher rpm because the flowrate is higher at higher rpm same orifice.

Someone else have more realistic numbers or better way of saying it? I more than likely made a math error.

Should have finished math

Very crude and rough comparison .... IF.... you could use all available pump flow. Again, I probably made a conversion and or math error but tried to use same approx for both comparison.

At 1700 rpm you could have 9.2 mm^3 /sec of flowrate

At 3400 rpm you could have 37.4mm^3/sec of flowrate

Through the same injector so that would require approx - crudely 4x more pressure if things were linear (they aren't).

 

[ak diesel driver]

I was under the impression that MI have a larger orifice size as well as higher pop pressure

 

[schiker]

Yes, My thinking is the bigger orifice requires a little more pop pressure to atomize the initial burst of injection then the flowrate takes over for pressure/atomization.

Then there are high pop injectors that I think just insure best atomization performance at lower flow rates.

Get too far mixmatched in pop pressure, atomization, fuelrates etc and you get rough idle and or cylinder imbalance etc.

 

[buddy]

Line pressure is up to like 11,000 psi.

The GM code only allows you to command 80mm3, and you can command that at any RPM. GM cuts fuel at 3900 RPM, but it can easily be added up to 4800 RPM. The difference is how to make it actually spit more fuel in the pulse width GM provides. Higher PMD resistor values will do this. Modded IPs may push more fuel in the same time (with higher internal pressures, or larger orifices)

Last weekend I hit about 120MPH at 22.5 degrees cam timing, which is 45 degrees crank advance, running 80mm3 at 3400RPM. If you add in the 4mm3 from the #9 resistor that would be 84mm3.

 

[6.5quest]

Before I left Heath I was working with a company that specializes in injection pumps. I was told it was possible to get a DS-4 up to 120mm of fuel but it would require a program to go with it. I had them do it to a mechanical pump for a guy but it ended up not running very well and was really smokey do to lack of quality injection timing from the mechanical pump.

 

[buddy]

well at 3400RPM with 100% TPS I was commanding 80mm3 and to get that there was a pulse width of 1.65ms. It doesnt code until 2.5ms, so if I or we can figure out how to add time to the pulse width parameter for a given fuel rate and RPM, then going from 1.65ms to 2.5ms for example would be 50% more fuel than what PCM thinks its commanding, so from 80mm3 to 120mm3.

 

[6.5quest]

I would talk to Lindon at Westers Garage. He knows these PCM's very well and might be willing to do some custom programing if you were so inclined.

 

[kojo]

pulse width = How long solenoid is closed
pulse widht what tech 1 or gmtdscan shows = how long time it takes for solenoid to close
so two different pulse widht...

 

[SmithvilleD]

Before I left Heath I was working with a company that specializes in injection pumps. I was told it was possible to get a DS-4 up to 120mm of fuel but it would require a program to go with it. I had them do it to a mechanical pump for a guy but it ended up not running very well and was really smokey do to lack of quality injection timing from the mechanical pump.

Do you know if it could deliver this higher fuel rate above 3000 rpm? It seems common to see a max fuel rate given, but no spec on what rpm the max fuel rate can be achieved.

I understand the PCM can command a given fuel rate. Just trying to confirm how much fuel the common, off the shelf 5521 DS4 can actually inject at 3000 rpm & above. I've seen a Stanadyne spec quoted on the 5521 as max of ~90 mm^3 @ 2000 rpm, but around 75 mm^3 at 3400 rpm. I can imagine reasons why the IP's ability to deliver max volume tapers off as rpm's rise. Just don't have any solid info where fuel flow was actually measured.

Where I'm going with this is wanting to calculate the realistic hp limit imposed by the fueling limit of the common, latest generation DS4. I'm happy to not go beyond the hp/fueling limit a DS4 can reliably produce.

If my 1st attempt at the math is correct, 75 mm^3 comes to around 1.97 lbs/min which correlates w/ ~ 275-285 hp w/ room temp air, under 1000 ft altitude, & a reasonably well sized/efficient turbo & IC.

That would seem to correlate well with the 225 - 250 hp RW hp inertial chassis dyno numbers some healthy 6.5's have produced.

 

[Woody35]

i would be intersted in how someone would get the ds4 to flow so much as 120mm of fuel

 

[buddy]

Well I can certainly program it to command 80mm3 at any RPM, so it reports 80mm3 all the way to 4800rpm if you like. GM cut out fuel at 3900rpm though.

I dont know if IP is limited that way or not. I dont know how the IP flow would be limited by RPM. The injection event is very short. So the time between pulses is the RPM factor, which is usually expressed as a duty cycle. 50% duty cycle would be a pulse width half the period. The PCM is capable of sending pulse width long enough to command 80mm3 at up to 3800 rpm ive taken it in 3rd, and no engine explosion or DTC codes. I didnt mean to go to 3800, but had power all the way to it, forgot I didnt have it in OD