Low side psi. effects on rail pressure ?'s

[RussJ]

So I've noticed lately that when I floor it I only get around 16,500 to 17,000psi. on the RP guage. I am running my Smarty on level 5 (not sure if it affects rail pressure or not). That sort of pressure just seems kind of low to me after reading about everyone else's pressure. Am I wrong? I've also read that the RP guage should spike at shutdown, mine does'nt spike at all.

Now I'm wondering how much low side pressure affects RP. I usually see about 5 or 6 psi under steady throttle. If I nail it I can easily bring the pressure down to nothing. I usually drive just hard enough to keep the low side pressure form bottoming out.

Sohere's my question. Does low-low side pressure (but not zero) equal low rail pressure?

I've read a lot about these different issues in other posts, just hav'nt yet found the difinitive answers I need yet. If you have any ideas please toss 'em at me!

 

[rbattelle]

Does low-low side pressure (but not zero) equal low rail pressure?

I would say yes. If you suck the low side dry (or partially dry), as when your lift pump isn't keeping up with engine demand, there's simply not enough fuel present at the CP-3 to compress to proper pressure. In other words, there's not enough volume of fuel to completely fill the pumping chambers, so you're only getting partial compression.



This would manifest as a drop in rail pressure. If that's what's going on, you want to repair the lift pump quickly because the CP-3 is fuel-cooled. Not a good idea to starve it.



Ryan

 

[cerberusiam]

Sounds about right for an 03. I think they are specced to max at 19k and you probably won't see that until defuel point. Spike maybe, maybe not. A lot may depend on how well the FCA is working, CP3, etc.



If your not hitting zero on the low pressure side when the rail pressure is maxing it is probably not affecting rail pressure as much as CP3 lubing and cooling. Hard to tell somtimes though.



AFAIK, the Smarty does not do pressure, at least on the stock turbo/injector programs. They were talking about adding a little but not sure what program or if it is in yet.

 

[TCDiesel]

Re-cycle gage (disconnect re-connect with power on) check again ,Stock Cp3 should produce 23,000Psi @ WOT under load, You should see some type of spike at shutdown.

 

[DE Jeeper]

From my expeirience I would say yes. I had a dying lp and I saw EGT's that were lower and I also felt a power decrease. When I put the FASS on I got the power back plus I now get good power through red line. The factory lp can not push enough fuel to the cp3 at high RPM and WOT.



Aaron

 

[RussJ]

I guess that answers my question. I think I've finally decided to upgrade the fuel system, I just did'nt want to spend $400. 00+ on a fuel system just to see IF it would help. I know it obviously adds a great deal of safety to the fuel system. I was just curious if it would affect performance much if at all.

As far as re-cycling the guage, I've never heard of this, but I guess I'll give it a try.

 

[SKneeland]

about $250 should get you an inline walbro pump and a bypass regulator(another $10-25 will get you a filter head to install a 2mic. filter... )



i could bring my fuel press. to zero (down from 8psi at idle) with the TST on 2/2 with the factory setup.



i now have the regulator set at 15psi at idle and i cant bring it down below 12psi at WOT with the TST on 9/9