Peak boost pressure for a cat C9

[Jim Edwards]

Hi; For those of you out there with a 400 hp C9 can you tell me what you see for peak boost pressure? Best I see is about 32 psi and I am wondering if this is typical.

Thanks 

[Chuck Jackson]

I try to keep mine down around 26-28psi max but I have seen 30. Never any higher than that.

Sorry...you asked about the 400hp C-9.

[Dave Atherton]

Jim, the peak boost pressure for Cat C-9 is 32 psi max. What happens at max. boost
pressure, the wastegate opens full and dumps exhaust from turbine wheel to exhaust,
doing this will control engine rpm and prevent engine damage from over speed.
Dave Atherton Retired Cat Mechanic

[Jim Edwards]

I guess I just need a C-15!

Thanks

[Doug Allman]

If you are thinking that the boost pressure is way to get more power from the C-9 you may want to ask Dave Atherton about installing a fuel pump like the C-12 has.  C-9 is gravity fed and several Beavers have found that with pump it definitely helps their hp and mileage.

[Jim Edwards]

HI Dave What are your thoughts?  Thanks

[Dave Atherton]

Jim, the C-9 engine need to have 81 psi fuel pressure at high idle and 58 psi at low idle.
The Cat C-12 high idle fuel pressure is 78 psi., both engines kinda have same fuel pressures
To produce max power of 400 hp. This is where engines start to be very different, the C-12
has a gear type fuel transfer pump to maintain constant fuel flow at all times from fuel tank
35 feet away. The C-9 has a piston type fuel transfer pump That has problems maintaining
constant fuel flow with the type of o-ring connections in the fuel line. ( when max power of
400 hp ) everything has to be in the perfect world and time and miles wear on the C-9 will
Show signs of low power because enters of air within the fuel system. Cat has installed a
electric pump that will maintain constant fuel flow on all of there off road equipment and
This makes a big difference. This is a area with motorhomes that needs to be looked at if
your fuel system cannot maintain 81 psi pressure all the time under full load.
Dave Atherton Retired Cat Mechanic

[Dale Walker]

Are you saying installing an electric fuel pump at the tank would be a smart thing to do, Dave? Their are as you know many good electric pumps more than capable of 80# of pressure.

[Dave Atherton]

Dale, what I would suggest to put the Cat C-9 engine the way Cat has made and tested engine. I
would only install a fuel transfer pump made by cat and used for the C-9 engine. Again understanding all the pressure and flow required, the perfect match would be using Cat parts. I do not want
to get something started with C-9 all needing fuel transfer pumps, there are many factors that
can be improved upon to correct low power starting at fuel tank and checking fuel pressure to
Be sure correct pressure is being maintained. If person feels low power and low fuel milage than
I would suggest putting on a electric fuel pump combo water/fuel setup back at engine.
Dave Atherton Retired Cat Mechanic

[Jim Edwards]

Hi Dave; Does Cat make these and would you have a part number? All engine data I can look at is good, no air intake restrictions. Average 7.25 mpg over 3,000 miles. over mostly flat ground (east coast). Not particularly zippy under acceleration but then again? I am concerned that we will be traveling cross country through the mountains later this summer and power will be an important issue. Also, if it squeaks another 1/2 mpg I suspect it will pay for itself.

I am guessing it might be less expensive to put fuel pump in and give it a try than paying cat to look at fuel pressure under max load. I am assuming that the pump can't hurt?

Please advise.

 

[Dave Atherton]

Jim, I guess the best thing for you to do first is contact Jim Nichols on the forum. Jim had a
Low power problem for many years and several Cat Dealers in 3 different states and one
of these dealers, inform Jim that it was his driving. This along with air within the fuel system
via: of mfg connections. Mark Bryant also installed the cat electric fuel transfer pump. Myself
all I have provided, correct information as cat parts, and correct pump that was match for the
C-9 off road engine. The C-9 engine is a very good engine but pulling fuel 35 plus feet is kinda
on the edge to maintain constant fuel flow and pressure over time. Dave Atherton Retired Cat
Mechanic