Put your CR Pressure Relief Valves back in!

[Soup Nazi]

If you have a pressure relief valve block kit, please remove it, blow on it three times and toss it in the trash can. They were solution to a problem, but the cure is much worse than the disease.

The system needs a valve to relieve huge pressure spikes that occur when the throttle is lifted quickly. The problem is only worse with larger injectors.

FCA duty cycle is higher with larger injectors to keep the target pressure where commanded. Dual pumps, modified puumps, etc all add to the problem, but are not needed to destroy the injectors when no valve is used.

We have seen solenoids exploded off the top of the injectors, nozzles blown apart, cracked injectors, etc. Nearly all this is attributed to the valves being removed from a system that can spike pressures past 60,000 PSI.

We have purchased a "bursting module" with pressure capabilities past 4000 bar ( 58,000 psi ) to do research and development on high pressure common rail fuel components. We can fail parts here at will.

Put em back in or buy injectors, nozzles and parts constantly.

 

[JasonCzerak]

So. how do you vent pressure, many times, with out destroying a $250 valve.

After a hand full of "vents" these things leak.

 

[JasonCzerak]

and one more thing. pressure makes additional power correct? when and where the pressure comes in is 100hp or better.. There is a limit I understand from what you said these injectors won't handle 60K. They do handle 30k right? or in that neighborhood.

can an RV be built to limit to 30k? 35K? where we can have the pressure, but less risk to the other system parts.

I'm all for a proper RV, but dropping in john's bolt made things better. even over the RV with a $1.50 bolt in the top.

 

[WICKEDDIESELS]

We have been working toward a replacement valve that is adjustable, it is quite a bit larger than the factory unit. Packaging and cost is the issue, as it would need to be remote mounted.

 

[Joesixpack]

So. how do you vent pressure, many times, with out destroying a $250 valve.

After a hand full of "vents" these things leak.

That is a bullchit wives tale, they are exactly designed for this purpose, and I've been preaching this for a while. Think about how many times our injectors close and open.

What kill's them is cooking the spring being held open with a mp8 100%

The pressure spikes are killing our chit...

 

[Soup Nazi]

Some people shim them for added pressure. The valves open all the time during normal operation. It is just a spring, a shim to adjust pressure, and a valve.

Added pressure gives us more power and usually less smoke.

The problem is the FCA is almost running wide open to keep the pressure where commanded. When the throttle is lifted in this condition, the system is shocked by a huge spike of pressure. The pressure relief valve is there to bleed that spike away. A block defeats the design to keep things from exploding.

I have tested some crazy pressure now myself in a running truck using several types of transducers and associated gages. Past 60K! Things begin to blow apart before that in some cases.

Some thought might be best directed at multiple valves for multiple pumps or these large output single pumps to get enough volume bled off during the spike. It doesnt take much of a volume removed to get good results.

 

[LReiff]

I have a few prv's that I've forced to fail, someone needs to find a way to rebuild them.

 

[molalla1ton]

Rip told me quite awhile ago DO NOT DO IT stating the same Don.

 

[Snedge]

Are there two threads or am I hallucinating?

 

[LReiff]

There is!

 

[triton]

Just some questions... not questioning your findings.

Obviously you know what you're talking about. My question would be.... are you saying 23K to 25K is all our trucks need to be efficient in the power produced ? Capping the rail has been the only way I've seen to achieve that higher psi.

It also says in the Cummins service manual that valve is a one time only blow off. After seeing the pictures Amish posted of it cut open, that is hard to believe. Cummins says once blown is has to be replaced. I can see a lot of us pushing a lot of fuel having to replace it quite often. Are you saying just do that until something else is come up with ?

If the system is only rated at 30K psi, I would think 60K would have grenaded the rail and many trucks by now.

One more.... how does the relief at the back of the head fit into this ? Is it not sufficient to relieve psi or is it to relieve psi from the injectors only ?

 

[zstroken]

What might be a decent fix would be to put a pressure snubber in the system. Now finding something that would deal with the 60,000 psi might be a little challenging.

 

[LReiff]

What is the possibility of controlling rail pressure spikes on the low pressure side of the system?

 

[Joesixpack]

Just some questions... not questioning your findings.

Obviously you know what you're talking about. My question would be.... are you saying 23K to 25K is all our trucks need to be efficient in the power produced ? Capping the rail has been the only way I've seen to achieve that higher psi.

It also says in the Cummins service manual that valve is a one time only blow off. After seeing the pictures Amish posted of it cut open, that is hard to believe. Cummins says once blown is has to be replaced. I can see a lot of us pushing a lot of fuel having to replace it quite often. Are you saying just do that until something else is come up with ?

If the system is only rated at 30K psi, I would think 60K would have grenaded the rail and many trucks by now.

One more.... how does the relief at the back of the head fit into this ? Is it not sufficient to relieve psi or is it to relieve psi from the injectors only ?

Pretty sure there is a bosch valve with a somewhat higher rating that will screw in place.

The valve is NOT a one time blow off....show me anywhere in a cummins or bosch service manual it says this???

However, it like the rail pressure sensor ARE one time use, as in screw it in once and the ring seal is good for one time, back it out and you are supposed to use a new one.
IMO screw it back in, if it don't leak, your golden.


Now that check valve at the back of the head is a issue as well, and more so with a set of injectors with some horrible leakage.

It can become enough of a restriction that it is the reason the solenoids blow off the top of the injectors.

 

[triton]

Pretty sure there is a bosch valve with a somewhat higher rating that will screw in place.

The valve is NOT a one time blow off....show me anywhere in a cummins or bosch service manual it says this???

However, it like the rail pressure sensor ARE one time use, as in screw it in once and the ring seal is good for one time, back it out and you are supposed to use a new one.
IMO screw it back in, if it don't leak, your golden.


Now that check valve at the back of the head is a issue as well, and more so with a set of injectors with some horrible leakage.

It can become enough of a restriction that it is the reason the solenoids blow off the top of the injectors.

You're correct, it's not in the SM. I'm pretty sure I saw it though, possibly in the manual for repair on Quick Serv. Don't have access there anymore. It's possible I mixed up the two though. Like I said... after seeing the pictures I was in doubt anyway.

I wouldn't have though Bosch would have a higher rated PR that would fit our rails. Yet another opportunity for someone

 

[Devon E]

I tried a few relief valves all poped off to soon. Im going to stick with my capped rail and let off the peddle slow like i bein doing at the end of the 1/4 mile

 

[morkable]

Kinda like I said in the other thread, I would think that using a dual feed line should help this, right?

 

[LReiff]

Kinda like I said in the other thread, I would think that using a dual feed line should help this, right?

I have a dual feed rail and have no pressure spike issues if that is what you want to know.

 

[Joesixpack]

Kinda like I said in the other thread, I would think that using a dual feed line should help this, right?

Not really, thats meant to improve flow from the pump, which would only make the spike worse. BUT the slight extra volume may help with dampening.

I have a dual feed rail and have no pressure spike issues if that is what you want to know.

.

How do you know you don't have spikes?

Our rail gauges are so dampened out we really only see a window of were the pressure really is at.

A split second of 35,40,50 thou we will never see.

 

[partsguy662]

I tried a few relief valves all poped off to soon. Im going to stick with my capped rail and let off the peddle slow like i bein doing at the end of the 1/4 mile

That sure seems like quite a gamble, but I'm sure you're more than aware of the risks involved.