S400 low boost P24v puller

The injectors could be opening late and closing early.
Their spring rate is too high as they are designed for a VP44. Your 12mm pump cant produce enough pressure in the wave traveling down the line to open them very quickly.
If they are aftermarket injector bodies (which are all imported) the springs are most likely a clone of a proper spring from Bosch, making things even worse because most have a rate too high.
 
Think I’ll send the injectors out just for good measure anyway. That’s the last thing in the fuel system I haven’t changed around.
 
Got the injectors back from the pump shop. They said two were spraying bad so they cleaned and lapped all of them and got them spraying right. I asked about lowering them to p-pump pressure and they said it wouldn’t make much of a difference and left them at 305bar.

Pulled this afternoon with it and about the same result. Couldn’t get much more then 4200rpm out of it in 2nd gear and 3rd gear and stayed at about 3400rpm. Boost was about 36psi and drive pressure was about 40-42psi. EGT was 1750* in 2nd gear and once I hit 3rd EGT dropped down to about 1680*. Not sure if that’s a fueling thing or an RPM thing. I didn’t think EGT would cool down like that.

I’m going to check compression this week I’m not sure what else to do at this point.
 
It will definitely make a difference, I dont know why they would say that.

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I mentioned lowering the pop pressure and they said it wouldn’t make that much of a difference beyond just retarding the timing a bit. Or maybe I misunderstood idk. I asked about lowering them but there just have been a communication breakdown somewhere and I got impatient and took them so I could make the pull yesterday.
 
Itll affect timing and duration, they're opening later and closing sooner. I'm not saying that it would solve all the world's problems but it can't be helping anything. Might burn a little cleaner I guess.

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I understand what you’re saying. Like I said I planned on having the pop pressure lowered but I guess there was some confusion. I’ll end up getting them done at some point during the off-season. Kinda aggravating but oh well.

I may try dropping to 33” tires and see if that makes a difference too. Idk I’m up for anything at this point.
 
Scattered said:
6x.018 injectors, forgot to mention.

Drive it harder as in more fuel? I slid the plate all the way forward today so I’m going to see if that helped this Wednesday at our next pull.
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We usually see better power numbers with 6x014" injectors with a 12mm pump, it's not gonna be a huge difference by maybe 20 to 30 HP.

If you send your injectors here to Power Driven, we could do some needle and body work to make them flow more. We could also verify the nozzle size and pop pressure.
 
dmigz57 said:
Try another set of governor springs in the pump like I recommended. My money is something to do with the pump. Very few pump builders to trust these days.
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I’ll be trying new springs. Tried adding a few clicks and I couldn’t get it to idle for the life of me. I’ve hit 5k+ RPM before (on accident hit nuetral) and leaving the line before shifting to 3rd I’ll be 42-4400 RPM. So that would mean the pump has 5K springs in it right? I’m sure there’s 100 different brands of 5K springs I’m just curious if they put 4K springs in it by mistake.
 
Big Blue24 said:
We usually see better power numbers with 6x014" injectors with a 12mm pump, it's not gonna be a huge difference by maybe 20 to 30 HP.

If you send your injectors here to Power Driven, we could do some needle and body work to make them flow more. We could also verify the nozzle size and pop pressure.
Click to expand...

The shop confirmed I had 6x.018 nozzles and added some lift to the injectors.

How would I gain some power by switching to a smaller injector? I’m curious, not doubting you at all.
 
Scattered said:
So you don’t think I have enough fuel?
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Huge difference in a 12mm at around 500cc's, and a 13mm at 500cc's.
I'm not a sled puller, have a drag truck. But did that same scenario yrs back. Made things so much easier
 
I didn’t know there was a difference in a 12mm and 13mm assuming they both are set at 500cc. What makes them different if they both are set the same?

Also idk what deliver valves are in it I never took them out after getting it back from the shop.
 
Injection rate on the 13mm

Going to a set of full cuts on your 12mm now will drive the charger harder.
 
I’ll have to take one out and see what delivery valves are in it then. I’ll check them tomorrow.
 
Took one out tonight. It looks like a full cut to me but the part that the valve sits in has 191 stamped on it.
 

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Scattered said:
Took one out tonight. It looks like a full cut to me but the part that the valve sits in has 191 stamped on it.
Click to expand...

Yes, those are a full cut delivery valve.

On the injectors, we've tested quite a few sets back to back, and bigger injectors do not always make more power. Sometimes they get more fuel in the cylinder, more smoke, more haze at idle, but they don't always make more power, especially on an air limited setup like a class specific pulling truck.

If the smoke is cleaning up, and boost is down, you need more fuel. If the smoke is thick and heavy, and boost is down, EGT is below 1600*, you need less fuel. However, it's common to see a 30 to 40 HP swing on a 700 to 800 HP truck trying different size injectors, different spray patterns, etc.
 
Would it be wise to maybe try a smaller injector? EGT stays 1650*+ and I don’t really think the smoke is ‘too’ thick. The pump shop mentioned my injectors had a flatter spray pattern but didn’t give me an exact degree.

Say I tried a different set with a narrower spray pattern- does spraying more inside the bowl net that much power gain or is it more to keep the pistons from melting and excess smoke in an average street truck? I’d also be able to run more timing safely?
 
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