Injector Balancing

[knh208]

I bought a set of new Bosch injectors from RockAuto a while back and finally plan to install them. I dropped them off at the local shop this evening (Diesel Services Group) to have them pop tested at a cost of $58 for the set. They will call me with a report in the morning. When I get the numbers, my plan is to look at what the average number is and have them adjust the worst ones to match the average.

My question is this: How much pop pressure range should I allow? Is ±50 psi good? 20? 10? :???:

They want $29 for each one they open up and shim. So, with that in mind, I want to minimize the number that I have adjusted.

Ideally, they'll all be close out of their sealed packages, and I'll walk away with a piece of paper that gives me the peace of mind, knowing that they're not going to leak or be total garbage when I try to fire it up. Regardless, I really look forward to hearing a silky smooth idle. I bet the neighbors look forward to it even more!

Any advice would be appreciated.

Cheers,

Kevin :thumbsup:

 

[Edzzed]

If they are new you'd think they'd pop test each one before it leaves the factory. If not who's to say they won't be out by 200psi or more.

 

[knh208]

Yes, you would hope they took the time to pop test them and set them very close to even. In the morning, I will have a report letting me know how true that is of the Bosch India assembly plant.

I'd love anyone's recommendation. Perhaps I'll call Bill and find out what he suggests.

 

[Edzzed]

if you have them set up to pop at a higher pressure you will get more finely dispensed fuel which should help in the combustion process.

 

[THEFERMANATOR]

if you have them set up to pop at a higher pressure you will get more finely dispensed fuel which should help in the combustion process.

Also keep in mind that higher pop pressures equal retarded timing to a slight degree. The DS-4 injection pump commands the injector to fire at a certain time, but it must reach a preset pressure before it will open. If you raise the pressure it will take teh pump longer to reach the pop pressure which equals out to slightly less timing. Also if you go to high then max pressure can exceed the 13K mark which can resulkt in a seized rotor and grenaded injection pump. The DS-4's max operating range should be kept under 11.200 PSI I believe for max longevity, but 13,000 PSI is the upper limit I believe.

 

[NVW]

The 13,000 psi would never be reached with a 2250 pop pressure,

 

[knh208]

Spot On

Test results are in. 2155 - 2181 psi. I won't be changing a thing.

Cheers

 

[THEFERMANATOR]

The 13,000 psi would never be reached with a 2250 pop pressure,

The 2250 pop pressure can easily give you 11,000 at the pump during an injection event at 3,000RPM's. There will be a pressure wave between the injector and the pump during an injection event, and it is these spikes that cause the really high pressures. It's been a long time since I studied the DS-4 pump, but I know I was shocked at what it can do. A good example would be a P7100 pump in a CUMMINS. The injectors in that engine are set to pop around 3500-4500 I believe depending on application, but the pump will routinely see pressures in excess of 21,000 at the plungers, and can see as high as 25-27K. Pop pressure is one thing, but pressure rise and spike is a whole nother story.

 

[NVW]

I didn't know that, thanks Ferm.

 

[Edzzed]

The 2250 pop pressure can easily give you 11,000 at the pump during an injection event at 3,000RPM's. There will be a pressure wave between the injector and the pump during an injection event, and it is these spikes that cause the really high pressures. It's been a long time since I studied the DS-4 pump, but I know I was shocked at what it can do. A good example would be a P7100 pump in a CUMMINS. The injectors in that engine are set to pop around 3500-4500 I believe depending on application, but the pump will routinely see pressures in excess of 21,000 at the plungers, and can see as high as 25-27K. Pop pressure is one thing, but pressure rise and spike is a whole nother story.

I guess it's kinda like pushing a door open. It's the initial push that feels the most pressure on your hand vs. pushing to open the door just before you remove your hand to walk thru. Ed

 

[3500GMC]

Test results are in. 2155 - 2181 psi. I won't be changing a thing.

Cheers

Very close range there. Peace of mind to know they're matched up pretty good. :thumbsup: