Need help understanding relationship between injectors and pumps. - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 6 (permalink) Old 09-05-2007, 05:24 PM Thread Starter
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Need help understanding relationship between injectors and pumps.

Guys, I'm trying to understand a little better about the relationship between pump output and injector size. Since it applies to 12v Cummins for the most part in this forum, I posted it here.

1. Can you install injectors that are too large for the stock pump? What is the effect? Low injection pressure? Poor atomization?

2. What happens if you increase pump output? Can you "overdrive" stock injectors? Damage? Can you flow stock injectors for a higher pump output?

3. How do you make sure your injectors are matched to the output of the pump? Is there a "range" of injectors suited for given pump modifications? Is injector pop testing and balancing required after pump mods?

Thanks for the help and insight!

-Evan

2000 Ford F250, Merillion, 6sp, AIC, DPTuner, BB turbo, Adreneline pump, modified IDM.

1998 Mercedes E300, Custom injector nozzles, soon to have Eaton M90 supercharger, 7.5mm pump elements, Holset HX40 turbo and a full custom intake and exhaust system = 400HP from 3.0l
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post #2 of 6 (permalink) Old 09-06-2007, 04:58 AM
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Quote:
Originally Posted by Kartek
1. Can you install injectors that are too large for the stock pump? What is the effect? Low injection pressure? Poor atomization?

Hard starting, a miss, poor mileage.......

2. What happens if you increase pump output? Can you "overdrive" stock injectors? Damage? Can you flow stock injectors for a higher pump output?

You can increase the pump output to a point. A set of 215 injectors can handle enough fuel for 425hp for sure. How the pump likes it, I don't know.

3. How do you make sure your injectors are matched to the output of the pump? Is there a "range" of injectors suited for given pump modifications? Is injector pop testing and balancing required after pump mods?

From what I hear, the injectors I have can flow enough fuel for 1000hp, but I'm making around 400hp with my current setup. Pump won't put out that much fuel for 1000hp. Truck runs great. For best performance the injectors should be balanced (pop off pressure). Isn't based off of pump tweaking, though. As long as they are a matched set when purchased new, no further adjustments shouldn't be necessary for a long time. The pump its self needs to be balanced for flow between each cylinder so it runs smooth. Change governor springs or cam plates, no need to take the pump off and put it on the test stand. Only if you want to increase the cc's by turning the plungers in their holders.
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post #3 of 6 (permalink) Old 09-06-2007, 12:57 PM
 
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An injector has to be quite large before it affects streetability, the P7100 delivery valve holder will become the restriction with larger injectors, barrels are turned on a test stand to delay port closure in rack travel.
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post #4 of 6 (permalink) Old 09-06-2007, 02:36 PM Thread Starter
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Thanks guys. So, it's fairly safe to install larger injectors (less potential negative effect) to a point?

Forgive my ignorance, is a P7100 pump the pump of choice for performance?

Is there a good, reliable electronically controlled Cummins pump?

Thanks!

-Evan

2000 Ford F250, Merillion, 6sp, AIC, DPTuner, BB turbo, Adreneline pump, modified IDM.

1998 Mercedes E300, Custom injector nozzles, soon to have Eaton M90 supercharger, 7.5mm pump elements, Holset HX40 turbo and a full custom intake and exhaust system = 400HP from 3.0l
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post #5 of 6 (permalink) Old 09-06-2007, 03:04 PM
 
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Yes

Yes, well depends on the person but a p-pumps potential is undeniable.

Well since the only electronic pumps cummins used in their trucks were the VP-44 (not great for big mods) and the common rail. If you want really big, reliable, electronic HP then the comon rail is where to look.
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post #6 of 6 (permalink) Old 09-06-2007, 03:58 PM Thread Starter
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Thanks for the input guys!

-Evan

2000 Ford F250, Merillion, 6sp, AIC, DPTuner, BB turbo, Adreneline pump, modified IDM.

1998 Mercedes E300, Custom injector nozzles, soon to have Eaton M90 supercharger, 7.5mm pump elements, Holset HX40 turbo and a full custom intake and exhaust system = 400HP from 3.0l
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