Now i've read most of the lift pump and such treads, but haven't seen any mention of one thing i am curious about. When our fuel system is under vaccum at say 5inhg how many gph does it flow???? http://www.dieselplace.com/forum/smileys/Confused.gif Edited by: heartbeatcanada

How did you come up with 5inhg? Are you wanting to know what the max flow to the engine is of the stock system. Or just what it flows at a certain point?

Bit of both, but mostly what is the max flow, in a stock fuel system??? Looking for gph while under max vacumm Edited by: heartbeatcanada

Good luck getting an accurate answer on this one. Too many variables to calculate. Later! Frank

As long as its in the ballpark, that would be fine http://www.dieselplace.com/forum/smileys/Ermm.gif

Like Frank said there are way to many variables and each truck could be different but I know it doesn't flow big #'s like some would think.

Well, here is some crude math. At 12 mpg @ 60mph should be about 5 gph. At 8 mpg @ 60 mph, that would about 7.6 gph. I have never saw anyone get worse mileage with the engine loaded down. It takes a monster load to get the Dmax to burn at max fuel consumption. My guess would be maybe 10-15 gph, maybe even 20 gph. But, I can't imagine any more than that.


I thought I read somewhere that the theoretical max fuel system delivery was 48 gph. But I'm not real sure on that number. That's awful high to me.

Dave- thats what i'm looking for, just have to confirm if it is 48gph or lower or higher. I have the shop manuals, but can't seem to find it in them. Figured some fuel guru would know http://www.dieselplace.com/forum/smileys/Disapprove.gif

Jeremy


I think you have to look to the maximum flow rate of the stock filter ... GM wouldn't allow it to exceed that now would they ...


48 would be a little high ,from what I remember I was told ...


Mac http://www.dieselplace.com/forum/smileys/Wink.gif

I'm sorry! I misunderstood the question. If you just want to know the max fuel flow maybe Mike Tomac can help. I think he is running a stock system and doing 12 second runs. Later! Frank

I'm sorry! I misunderstood the question. If you just want to know the max fuel flow maybe Mike Tomac can help. I think he is running a stock system and doing 12 second runs. Later! Frank





http://www.dieselplace.com/forum/smileys/Confused.gif http://www.dieselplace.com/forum/smileys/Confused.gif http://www.dieselplace.com/forum/smileys/Confused.gif http://www.dieselplace.com/forum/smileys/Confused.gif http://www.dieselplace.com/forum/smileys/Confused.gif

Well the filter flows 48 gph max. Thanks, now back to the drawing board, and put on my dr. evil mask. http://www.dieselplace.com/forum/smileys/HiHi.gif

Dave's math is right on with what I found on a few trucks, less than 15gph. How much hp are you going for Jeremy? 674 with stock stuff, should be interesting what you come up with.


P.S. I've never been able to make 1 extra hp with a lift pump on a dyno but then again I can't make over 600 with stock fuel, turbo, and no extra fuel source.

You can't go by miles per gallon or gallons per hour because of the fuel that is returned to the tank, unless you know how much that is. You did ask how much did the fuel system flow. I don't know the answer.


Gerald

You're right Flyboy, but you can make some assumptions to come up with a ballpark figure and use that as an estimate.


The fuel burn @ 8 mpg @ 60 mph is still 7.6 gph flowed. So now we know that the fuel system will flow at least 7.6 gph.


There are 2 ways we can approach the return flow.


1 - We can assume that the Dmax fuel system is designed to flow approx 2 times the expected worse case fuel consumption. That would take into account going into periodic fuel burns that are above the norm. That would put the 100% fuel flow at 15.2 gph. This may be pretty close but again one is taking a swag at it and is probably conservative.


2 - We can assume that the fuel filter is the limiting component and that is rated for 48gph. This number is higher than one would expect for an engine for this size, so this number is a more liberal estimate.


I think you'll see that the true flow rate capability of the fuel system is somewhere between those extremes. Given more time and a couple of measurements, one could calculate the max possible flow rate that 1/2" tubing will deliver with a 2.5 PSI drop over 10 ft. (Atm pressure-5" Hg Vac). That will be the limiting flow for a stock system.Edited by: DavesDmax

15-20 GPH on the return @ idle. Then just add in what the engine burns. This would be for idle only.

I know the most fuel removed from the tank is less than 15 gph. Sometimes more is used and sometimes more is returned.

How about this..go by driving range in miles, divide by speed for a time..woprk the numbers to use the entire tank capacity..viola'..GPH of the engine at cruise.

Wicked that is right especially if you knew your range towing 100% at max power. But for the fuel pump to feed enough you still need to add what is being returned to that number.

If you are asking for specs at 5 hg then I asssume you are wanting to know fuel flow under full acceleration? I would suggest installing an inline flow meter and recording as you accelerate.


The MPG calculations are good starting point, but are only an average. Very low under constant throttle, very high under wide open throttle, who knows under heavy acceleration?

That is what I did Bronco.

OIC.


I just reread your post about the most measured was 15 GPH.


Was the gauge placed so that it included all fuel leaving the tank?