?'s on matching injectors with p-pumps.

T

Todd W

Comp Diesel Sponsor
I have seen many threads where people have there pumps built and benched and say that they flow such and such cc's of fuel. There are rules of thumb about how much horsepower one can make with a cc of fuel so 500cc of fuel and whammoo 1000 hp. But what about the injectors, obviously not every injector is capable of flowing 500cc of fuel so what are the rules of thumb for injectors per cc.


example
a good set of 5 x .012 will not be a restriction until around 300cc of fuel.

Of course i have no idea if that is accurate but you get the picture, also i read a lot about pintle lift an pop off pressures how do these relate to power production. I know that the injector is a very important piece of the power making puzzle just trying to get a solid grasp of it all.
 
With a gas engine where you are working with a very narrow window for fuel ratio you can make a decent estimation on X amount of fuel can get you Z hp. But with diesel you have the ability to run lean(clean) or severally over fueled and everything in between. So you really can't make a decent estimation on HP based on X amount of fuel. Then you throw in the forced induction curveball and it adds another variable. 500cc of fuel with an HX35 will be a totally different HP than 500cc with an s480.
 
It would be simple math to calculate, but the orifice size is just a part of the equation.

500cc's/1000strokes is 0.5cc/stroke @ 5000RPM would be 2500cc's/ml's per minute which is 2.5LPM. Include the needle restriction to the overall nozzle flow and keep this value above the injected quantity for the desired RPM.
 
Going by the numbers from my Bosch book, typical injection events are 1-2 ms long. So if it has 5000 events/min, the total injection time is only 5-10 seconds in that minute to flow the 2.5 litres. Wouldn't something in the 15 LPM range be needed at that point?

Maybe more ordinary numbers, 0.5cc at 2k pump rpm. 1 litre/min from the pump would need around 6LPM nozzle?

Am I way of base?
 
The IP spins 1/2 of engine RPM, so 5000 injection strokes in one minute would require 10,000RPM @ the crank. Flow numbers measured with a orifice plate will always be higher than when measured with an injector due to opening pressure/needle lift restrictions.

gs1000 said:
example
a good set of 5 x .012 will not be a restriction until around 300cc of fuel.
Click to expand...

300cc's @ 3500RPM would produce ~ 1050ml's per minute, a unmodified "435" micro-blind nozzle 5x0.010" flows ~ 1825ml's per minute without needle restriction. Set up properly this nozzle would be sufficient, but a 5x0.012" would be a safe bet, and make more power.
 
ok so the ml/m of an injector makes perfect sence to me.

So assuming all the oxygen needed is available how does one map out their fueling for desired HP.

Like me for instance

I have a 13mm pump i am wanting to send it to DPE to get gone through. i imagine that he will be able to set the pump to a certain cc range. so for my goals I am wanting around 1200 RWHP. I think i could be competitive in my classes i race in and even bring home a trophy or 2. So for this number to be acheived how much fuel does the pump have to move. I have heard that 1cc of fuel is good for 2 hp. so i would need 600cc's if that were correct.

so using this math

300cc's @ 3500RPM would produce ~ 1050ml's per minute, a unmodified "435" micro-blind nozzle 5x0.010" flows ~ 1825ml's per minute without needle restriction. Set up properly this nozzle would be sufficient, but a 5x0.012" would be a safe bet, and make more power.
Click to expand...

I could just double this and find that i need 3650ml's per minute without needle restriction.

where does the end user find this info on injectors he might buy?
 
Last edited:
Smokem said:
It would be simple math to calculate, but the orifice size is just a part of the equation.

500cc's/1000strokes is 0.5cc/stroke @ 5000RPM would be 2500cc's/ml's per minute which is 2.5LPM. Include the needle restriction to the overall nozzle flow and keep this value above the injected quantity for the desired RPM.
Click to expand...

The IP spins 1/2 of engine RPM, so 5000 injection strokes in one minute would require 10,000RPM @ the crank. Flow numbers measured with a orifice plate will always be higher than when measured with an injector due to opening pressure/needle lift restrictions.
Click to expand...


so does 1 rpm = 1 stroke thus yielding 2500cc in the first example or would it be 1250cc needed at 5000 rpm?
 
Measuring cc's/1000strokes does not include the residual stroke. 1200whp is no small chore, are you planning to do this on fuel only, or with the use of N20? There are a few companies that do flow work that can give you an honest answer as to the hydraulic flow rating.
 
Will be using N20 for sure.

with my current setup i am around 850rwp depending on which online calculater i use, compd calculater has me at 840 rwp. this is with a 215 12mm pump and ddp 4 injectors and of course :nos:

big plans this winter, hoping to figure out the fueling needed for my goals.
 
Many variables. Figure out the long block setup first, then the air, then you can do the fuel setup.
 
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