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High Injector Pop Pressure

6.5L

6.5L

Old Iron Runner
Messages
1,177
Reaction score
433
Location
Northwest Wyoming
Ok. Just looking for a clear answer here. Straight forward. Would increasing pop pressure in an injector help better atomize fuel down low in the RPM for better low end torque and still help the top end after the turbo spools? I am thinking about a set of 2400-2500psi pop pressure. Yes or No?
 
It is a fresh DB2831-4911 with maybe 6K miles on it. It has a quarter turn up for fuel. Do you think it would support that. I have no wish to ever go above 2500psi. I think it wouldn't do too much after that. I was gonna probably settle for 2400psi or so.
 
these pumps make 10,000+ psi of pressure so your pump will be able to support it. imho higher pop pressure inejctors have not been tested enough to know the benifits and disadvantages in these engines. You also have to remember is the higher you set the pop pressure the more strain you put on the inj pump.
 
Yes, I know. But I think stock is 2100 so a 300-400psi bump I don't think would be that terrible on it. I could be wrong. But think I am gonna give it a shot
 
I just need new injectors bad. I can hopefully get them ordered sometime this next week or the one after
 
When ever I break down and do injectors, I'm buying the nozzles and set pop pressure at 3000. But that will be a while still.
 
3300psi almost seems a tad high to me. I am not looking for a huge increase. Like I said, around 2500psi or so. Just a bump over stock, and i think I will definitely notice a difference. I am around 150K miles on mine and I think it is beginning to show. I am sure my pop pressure has dropped a bit as well.
 
3300 may appear high. But there really is nothing that will hurt. There are MANY applications that use the 4 and 6 cylinder version of this pump and have pop pressures greater than that. So the pump isn't an issue. And the marine nozzel was factory set to 3300 psi in the marine application, so we know the injector tip can handle it.
 
I will wait and see how you injectors keep performing but I still think more than likely I am going to have them set at 2500psi. I think anything is better than what I am running now. It seems higher than 2300psi is kind of uncharted with the 6.5L injector so I would rather stay on the conservative side. I can't afford to have anything major break. I am just looking for a bump over stock for better low end torque.
 
You are correct. Anything is better than stock.

Don't wait to see how mine do. Unless something big and bad happens, the 6.5 will fall out of this truck within the next few months...
 
Just be forewarned, high RPM's and increased pop presusres can cause a pump to lock-up due to high injection pressure. The 2200 pop pressure standard is there to keep the injection pressure below 10,800 at the pump. Fuel has weight, and pushing it through the lines at RPM causes a pressure differrential from the pump to the injector. 300 more don't sound like much, but when you multiply it out you could push the pump up to 13,000 PSI where the rotor is in danger of seizing.
 
Fermanator, do you think 2400psi is too much? I think the pump should be able to handle it. I am never really at high RPM. And if I am, it isn't for very long. I would be happy to drop to 2300psi if it meant the pump was saved. What does everybody else think? Any input would be great.
 
You can go as high as you want,or untill it won't start hot. I went as high as 5000 psi ,and no seizure. I had my Tahoe at 2500 psi,it ran ok,but I lowered them back to 1600 psi. I didn't drive it yet but it sounds the same .
 
IMO and thoughts on this.
The springs and parts that get hit with the high pressure to open and close would have the same issues stronger valve springs have. All the pop pressure does is make a clean start and stop of the injection without wasteful dribbling of fuel. Injector is more or less open after the pop pressure can be sustained and really doesn't care if the pressure then hits 10,000 PSI. Because it is wide open at that point.

When the injector closes at 1800 PSI or 5000 PSI it will chatter if there is more fuel delivery on the cam ramp as fluid will not compress. You can only make a cam curve so steep. I suggest that the injector would chatter longer trying to close at a higher pressure when the fuel delivery is nearly stopping. There has to be a 5000 PSI point on the cam and a 1800 PSI further down the slope of the IP cam. 5000 PSI is twice the hammer that 2500 PSI is. So the parts hit twice as hard and get hit more times with the chatter of opening and closing. The opening ramp may not be able to sustain 5000 PSI at first. So full open may chatter the injector longer as pressures bounce around the pop pressure. After all the steel lines, timing chain, etc flex at these pressures.

I suggest from the above theory that the injector would be the weak point and failure would take out the engine not the IP.

The chatter could cause harmonics or other vibrations and fatigue other parts. Like stretching the timing chain with a the hammer action before full open and full load.

My understanding is the DS4 spills fuel at the end of the injection cycle vs. DB2 pumps. So closing as described above may not apply to them. The opening chatter would be the same.

I could be out in left field on this, but, there has to be a good reason pop pressure were set where they were.
 
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