Fuel demand

-
7

71scamp78

Well-Known Member
Joined
Sep 28, 2014
Messages
1,355
Reaction score
343
Location
terre haute indiana
Ok really wanting to run a mechanical pump. Question is what one will be enough. I'm coverting to a 3/8 sending unit and will have around 615 hp in my 512 cubic inch street car. Probably won't see full throttle pulls longer than 15 seconds. Can a stock pump handle it or would I need say a Carter, Hollet or a Eddy pump. No one has the Eddy pump which I like because it has 3/8 inlets and outlets.
 
71scamp78 said:
Ok really wanting to run a mechanical pump. Question is what one will be enough. I'm coverting to a 3/8 sending unit and will have around 615 hp in my 512 cubic inch street car. Probably won't see full throttle pulls longer than 15 seconds. Can a stock pump handle it or would I need say a Carter, Hollet or a Eddy pump. No one has the Eddy pump which I like because it has 3/8 inlets and outlets.
Click to expand...


For what you are doing, I wouldn’t do it. I don’t have the guts.

I wouldn’t even use a mechanical pump for that. I’d find a 140 gph (or bigger) electric pump and run a bypass regulator for what you are doing.

It’s a PITA because you have to run the return line (both the return and the fuel line should be #8 and #10 would work too) and you have to run a loss of oil pressure kill switch so if you get into a crash and the engine shuts off the pump stops with it. You don’t want to be in a crash and have the pump (especially a big pump like that) blowing fuel all over hot engine parts. You’d be getting toasty right quick.
 
Rat Bastid said:
For what you are doing, I wouldn’t do it. I don’t have the guts.

I wouldn’t even use a mechanical pump for that. I’d find a 140 gph (or bigger) electric pump and run a bypass regulator for what you are doing.

It’s a PITA because you have to run the return line (both the return and the fuel line should be #8 and #10 would work too) and you have to run a loss of oil pressure kill switch so if you get into a crash and the engine shuts off the pump stops with it. You don’t want to be in a crash and have the pump (especially a big pump like that) blowing fuel all over hot engine parts. You’d be getting toasty right quick.
Click to expand...


I would think 3/8 line would feed it plenty of fuel??
 
71scamp78 said:
I would think 3/8 line would feed it plenty of fuel??
Click to expand...

1/2 from the tank to the pump and from the pump to the regulator. You can use 3/8 from the regulator to the carb.

Back in the day the fuel pump standard was some Mickey Mouse flow rate. I think it was 1 gallon in 30 seconds. That’s all good if you are standing still. Add motion and G force to it and it’s a piss poor way to judge a fuel system.

All pumps are rated at free flow. As the pressure goes up, the flow drops. A 110 gph pump is 110 gph free flow. Run the line pressure up to 7 psi and the RATED flow drops. I say the real flow is far less than what the graphs all say, because you have to add in hose lengths, fittings and such.

That goes for electric and mechanical pumps. Buying a pump based on free flow ratings or equally as bad, horsepower is a bad policy.

A 140 gph electric pump is about the minimum I run. And I do not dead head any pump, even if it’s a race car.
 
615 hp with the correct A/F ratio consumes a little over 50 gph.
The Carter 460X electric pumps [ most reliable stand alone pump there is ] is rated at 100 gph. These will deliver about 90 gph at the carb, so you have a good safety margin.
 
Bewy said:
615 hp with the correct A/F ratio consumes a little over 50 gph.
The Carter 460X electric pumps [ most reliable stand alone pump there is ] is rated at 100 gph. These will deliver about 90 gph at the carb, so you have a good safety margin.
Click to expand...


LOL.
 
615 HP @ full throttle for 15 seconds ?
On the street ?
Can anyone calculate the terminal speed ?
I ran just over 500 hp with a 440-6 in a 4000 lb charger with 3/8 and a carter HP mechanical pump ( pretty much stock setup) with no issues. Adding an electric pump should be adequet I would think.
 
mbaird said:
615 HP @ full throttle for 15 seconds ?
On the street ?
Can anyone calculate the terminal speed ?
I ran just over 500 hp with a 440-6 in a 4000 lb charger with 3/8 and a carter HP mechanical pump ( pretty much stock setup) with no issues. Adding an electric pump should be adequet I would think.
Click to expand...


Explain how horsepower is the determining factor in pump selection please.
 
I ran a facet jiggler in my Honda 600...same one in my 2.0 Mazda......413 Motorhomes run this same fuel pump..4psi, 25GPH. Run it close to the tank so its pushing. Not 600HP race rated. 1.5psi at full flow, 4 at idle. How long does it take to fill a Holleys fuel bowls at 1.5 psi? faster than it can burn it? That would be a good engine masters episode, put a 440 on a dyno and run a Facet pump and watch the AFR's. Maybe 2 G's could be simulated by putting the fuel pump much lower than the carb so it has to push harder to fill the bowls.
"...Typically, at wide-open throttle (WOT) a gasoline engine will burn approximately .5 lb. of fuel per hour for every horsepower. So that means a 650 hp engine will burn 325 lbs. (54 gallons) of fuel every hour, or under a gallon a minute AT 650HP. .."
 
Last edited:
Pishta,
I tried two of those small transformer style elec pumps on my dart. Forget the actual GPH but it was pretty low, so I had the two connected in parallel [ the fuel lines in par ]. Winding out in 1st gear, engine ran out of fuel. Carter 4594 elec pump fixed it.
 
Scamp,
Worth buying D.Vizard's How to build HP, SA#52.
There is a detailed section on fuel delivery, sizes of lines, g forces etc.
 
Bewy said:
Rat Bastid,
Still laughing?
Click to expand...


Yep, still laughing. Pishta doesn’t explain anything. Picking a fuel pump based on horsepower is like buying a cylinder head based on airflow.

There is way more to it than calculating how many pounds of fuel per hour an engine burns. That’s why an engine dyno can use a much smaller fuel pump than you can in a real car.

That Carter pump you posted wouldn’t run a decent hooking Briggs and Stratton.
 
Really? Just shows how ignorant you are. It fuels a 4100 lb car that runs 119 mph in the quarter.
Pishta explained it very well. So do people like Holley, D. Vizard & a host of others [ Remember Holley? They make carbs & pumps, they would know...]
 
Bewy said:
Really? Just shows how ignorant you are. It fuels a 4100 lb car that runs 119 mph in the quarter.
Pishta explained it very well. So do people like Holley, D. Vizard & a host of others [ Remember Holley? They make carbs & pumps, they would know...]
Click to expand...


Yep. Ignorant I am. But here is a question. It sounds like you think 119 is awesome. It may be. But in reality maybe it should be running 122 or so.

Your word means nothing to me. 119 may be what it should run. Maybe not. Either way, I don’t run lawn mower pumps on performance cars. That’s hillbilly.

As for Holley knowing something...that’s open for adult discussion. Their own literature says they are pretty ignorant on their own products.
 
Rat.

I agree with you!
Maybe 122 or more. But you shot your mouth of without knowing any facts.
These are the facts: the driver probably has a total of 20-25 drag strip runs, started when he was 50 yrs old, now 60. This car has had NO tuning done: not on the carb, ign timing or launch technique. There is definitely more in it just by refining what is there. Car is street reg, driven to & from the track. Pete, being the kind bloke he is, asks the Holley boys if they need any petrol to get home because he has plenty..

I once read that the US had about 1000 1/4 mile tracks. Since then I have read of some closing. In this country we would be lucky to have 12 tracks.....
So our problem is not enough tracks, not open long enough, long travel times to get there & practice/tune.
 
Engine masters did actually do an episode on pumps.


Turns out shitty pumps are shitty.
 
You must log in or register to reply here.
-

Back
Top