Main Menu

fuel pressure

Started by Norm, August 03, 2009, 12:37:24 PM

Previous topic - Next topic
Print
Go Down Pages1
User actions

Norm

August 03, 2009, 12:37:24 PM
My latest obsession is fuel delivery and I'm wondering if anyone knows the best pressure range for FCR carbs? And would it be different for CV carbs and why?

Norm

#1
August 06, 2009, 09:23:25 AM
Anybody? Chris?

ducpainter

#2
August 06, 2009, 04:13:47 PM
If you want to know what an old painter thinks...

pressure is very secondary to volume in this instance.
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


Norm

#3
August 06, 2009, 06:22:28 PM
I've got volume covered, but, as I said, it's my lastest OBBSESION, so I have to know more, and more, and more, and..............

needtorque

#4
August 06, 2009, 06:50:30 PM
I cannot imagine the optimal pressure being any higher than 3-5 lbs.  They are still carbs and thus require very little pressure.  Gravity is really more than enough given a large enough supply line.

But in reality you already know this Norm so.........?  why the question?
Who insures the FDIC?

Norm

#5
August 07, 2009, 08:53:43 AM
3-5 is what I've been assuming, but I don't have a lot of experience with the numbers and was hoping someone had done more work in this area. I've run a number of bikes with only a gravity feed and never had a problem, but, of course, the fuel pressure will go down as the tank empties and I've never used a gauge.
I'm going to set a bike up with an electric fuel pump, a pressure regulater, and a gauge so I can do some experimenting. I'll probable limit the testing to FCR carbs though.

MotoCreations

#6
August 07, 2009, 10:00:57 AM
FCR's -- 3.5psi is what I'm using for years.

Pumps -- three options:

1) self-regulated electric.  Thus only one fuel line required.  (I've done this for 14 Ducati's)
2) non-regulated electric with return line to tank.  Best for volume demand while racing.
3) High volume vacuum.  (just did for my DesmoDevil to try something different)

note: Never was impressed by the factory vacuum pump -- I've had fuel volume delivery problems with it and it sucks having to back off the throttle when the carbs are starving.

note: Gravity feed isn't an option as my fuel pickup is lower than the carb's -- fuel doesn't flow up hill very well.

64duc

#7
August 07, 2009, 11:21:11 AM
Quote from: ducpainter on August 06, 2009, 04:13:47 PM
If you want to know what an old painter thinks...

pressure is very secondary to volume in this instance.


As long as you stay under 7psi. Any more and you chance overpowering the needles and floats. No FHP with FCR's just general to carbs.
94 M900, 64 Diana 250

Norm

#8
August 09, 2009, 02:46:30 AM
I'm sticking with Mark's #1 for starters. I've never had a fuel starvation problem but I want to see what minor pressure changes do for throttle response and sustained high rpm. I hope to be able to test at some speed tracks like Daytona but I don't know yet.
As some of you know, I'm developing a new motor and while I don't mind buying down a couple of stockish Duc motors, the new ones are going to be waay too expensive for me to use as "throwaways".
Print
Go Up Pages1
User actions