Interesting findings after Dyno Days - Pressure Relief Valve Failures

[Tomeygun]

So, with my trusty DRB3 in hand I watched a few 3rd gens on the dyno and monitored the rail pressure.



We found quite a few trucks that we are seeing poor rail pressure and low HP when compared to other trucks...



I thought I would let everyone know what this seems to be a big problem with trucks that have seen heavy pressure boxes,etc



That part I can get for $313 - less if I buy in volume

 

[Lonestar]

I WANT ONE!!!



KEEP ON TRUCKIN'

Lonestar

 

[RMalone]

Seems like one of the aftermarket companies should make a relief valve that is bullet proof and adjustable.

 

[JMerola]

Tomey - what are your thoughts as to the ultimate cause of these low rail pressure readings. Is the mechanism of the low rail pressures due to the valve failing to close fully after damage (and therefore preventing presure build up)?



This association between "pressure" boxes and rail / injector damage has not only got me paranoid, but confused as to how to continue to add (additional) SAFE power. It seems like the timing/duration envelope has been pushed pretty far (maybe as far as it can be pushed) with the likes of the TST (maybe the HOT Juice) box. How do we add more fuel safely?



I wish someone would design a "smart" pressure box that would negatively feedback on itself to prevent excessive rail pressures - one that would augment a duration box nicely without causing damage. (maybe this already exists?)



Or maybe the answer is higher flowing injectors and/or a modified CP3 that would be able to maintain sufficient rail pressures with greater "open time" from these duration boxes.



What do you think?



- Thanks, Jason

 

[jwilliams3]

Tom,

Did the trucks with bad valves dyno low?

 

[DieselTweaker]

Tom good find, did you notice anything else odd when watching the pids??

 

[dhill]

What I want to know is, how much is the DRB3 if you buy in volume?



Dave

 

[robertyoke]

What I want to know is, how much is the DRB3 if you buy in volume?



Dave

I may want in on that.

-robert

 

[05mxdiesel]

yes tom, tell us what brand and where you got your scan tool, as I been looking for a while and I am not sure what to buy.

 

[Reb.B]

The cheapest i've seen the DRB III has been $5800 with 2 years of updates. Used one are cheap, but you need extras do do the can bus 06 trucks. The duration boxes when they get turned up really drop the HP. I lost 150 HP going from level 5 to level 7. The rail pressure relieve to get is the Marine QSB 425HP i believe. I've been told that they are built to pop off easier without failure. Cummins has them for $625. I'm gonna try one out as soon as i get a dual feed or a bigger CP3.

 

[GWoody]

So, with my trusty DRB3 in hand I watched a few 3rd gens on the dyno and monitored the rail pressure.



We found quite a few trucks that we are seeing poor rail pressure and low HP when compared to other trucks...



I thought I would let everyone know what this seems to be a big problem with trucks that have seen heavy pressure boxes,etc



That part I can get for $313 - less if I buy in volume

Tom, what kind of pressures were you seeing @ wot, would the pressure drop off at the first mat of the throttle and then return or did it stay low through the entire wot run??? Did the trucks in question ever reach the 26000 psi or was the pop off valve seeping not letting them acheive that number.

 

[Tomeygun]

Tom,

Did the trucks with bad valves dyno low?

IMO, yes - three trucks with 66mm turbos, TST/EZ chips, and all different hp, 524 - 471 - 417



And the lowest HP one was never even got tot 11k in the rail... Its GOTTA be the valve

 

[Tomeygun]

What I want to know is, how much is the DRB3 if you buy in volume?

Dave

I can get them on sale for $3200 (most cables, etc, new in box)

How do we add more fuel safely?



I wish someone would design a "smart" pressure box that would negatively feedback on itself to prevent excessive rail pressures - one that would augment a duration box nicely without causing damage. (maybe this already exists?)

Or maybe the answer is higher flowing injectors and/or a modified CP3 that would be able to maintain sufficient rail pressures with greater "open time" from these duration boxes.

What do you think?

I think 50hp from pressure is all you need, and there is a certain company already working on a box that backs down due to low rail psi... .



And my mod'ed CP3 will be here/on mid december, expect a full review

 

[Tomeygun]

The rail pressure relieve to get is the Marine QSB 425HP i believe. I've been told that they are built to pop off easier without failure. Cummins has them for $625. I'm gonna try one out as soon as i get a dual feed or a bigger CP3.

I found the part number for a QSB5. 9 300hp motor, and it was the same part number as our relief valve... I had such high hopes, let me know what Part# you found.



Ours off our trucks is - 3947799 (cummins #)

 

[Reb.B]

yah, the new number started with a 4. I gave it to Piers. I'll have to go through my records and get the part number. Count me in on that DRBIII, does it come with the software to work on 06 trucks? PM me when you get a chance.

 

[SP Diesel]

TommyGun,



I just wanted to be sure you remember that the DRB will not show actual rail pressure when there is a pressure box like the EZ on the truck. 11,000 on the DRB does sound a bit low, but I'm not sure how much EZ is actually fooling the ECU.

 

[Reb.B]

Okay, here we go, fuel rail part number is 3957077. My price is somewhere around $640. I haven't tried too hard to find a price. I figured most of my problems where in the CP3 now. I could be wrong though. I was hoping mine would quit altogether, (preferably as i roll into the shop, lol) then i would have an excuse to go get the rail pressure relief. Some more numbers, ... . 4930441 425HP QSB injector around $275 each and #4089183 for the piston around 155 each. I just need the part number for the CP3 now.

 

[Tomeygun]

TommyGun,



I just wanted to be sure you remember that the DRB will not show actual rail pressure when there is a pressure box like the EZ on the truck. 11,000 on the DRB does sound a bit low, but I'm not sure how much EZ is actually fooling the ECU.

IN theory, the box only fools the ECM by like 2-4k -- So even then, I would want to see in the 16-18k reading at the mimnum...



But you are right, with these darn computers, who really knows...

 

[Tomeygun]

Okay, here we go, fuel rail part number is 3957077. My price is somewhere around $640. I haven't tried too hard to find a price. I figured most of my problems where in the CP3 now. I could be wrong though. I was hoping mine would quit altogether, (preferably as i roll into the shop, lol) then i would have an excuse to go get the rail pressure relief. Some more numbers, ... . 4930441 425HP QSB injector around $275 each and #4089183 for the piston around 155 each. I just need the part number for the CP3 now.

BTW - marine CP3 part# - 3972814

Our 03 Cp3 # - same



so it looks like the marine Cp3 is the same as ours(and this was a 380hp marine engine in a sea-ray boat)

 

[Reb.B]

well i guess we need to get the part number off of the 8. 3 CP3 in a QSC 540 HP. Maybe somebody can go over to one of those marine website/forumns and see if you of those guys will get us a CPL # or a CP3 # of their 540 HP engine and then see if it will bolt up