BrianHeston

Would there be any reason not to move the pump & filter into the engine compartment so that they would still be in the proper order and yet the filter would be easier to monitor?

The only thing that comes imediately to mind is fire hazard if a fitting leaks...

Any yes/no & why would be appreciated...

Thanks,
BrianHeston

jeremy

iTrader: (1)

the pump needs to be placed lower then the pickup on the tank for cyphening reasons. these are low psi pumps (carb).

Kill No Cone

iTrader: (6)

Electric pumps are pushers and not puller pumps (if that makes sense). They need to push the fuel to the carb and therefore need to be placed near the fuel tank.

Directfreak

iTrader: (2)

Also, if you get some crap in the line, it will screw up the entire line up to the filter. Not an issue if the filter is in the rear.

Some people (myself included) prefer two filters. A main one in the rear, and a clear one (to see the quality of the fuel) near the carb or fuel rail depending on your application.

jeremy

iTrader: (1)

i use dual see throughs, fore and aft of the pump and no screens in the carb.

BrianHeston

The whole puller vs. pusher thing doesn't quite jive with basic physics. Pressure in a system being constant and all. But if that's how they work best I guess I'll have to leave it that way.

Thanks for the answers...
BrianHeston

jeremy

iTrader: (1)

but pressure in the system isn't constant. there is less pressure behind the pump. that is why i said it needs to be lower then the pickup for cyphening reasons.

Kill No Cone

iTrader: (6)

I wish that I could give you a physics related answer, but the design of the valves in the pump make them better at pushing fuel than siphoning it.

Call the manufactures tech line and check it out, if you like.

RotaryNotary

For the "physics" behind the answer...

I can't guarantee the answer, but in aircraft engines the fuel pump is usually gravity-fed, and a "pusher" pump. The reason for this is that if the pump "pulls" the fuel, it is easy to get a vapour-lock at any bend in the fuel delivery tubing...(i.e. easier for the gas to turn to vapour than to be pulled towards the pump).

I don't think I've explained this well...if you want more details let me know and I can look it up in some reference texts....

BrianHeston

Okay, I was VERY tired when I posted that question earlier. Now that I look back on the thread I'd think I was dumb too. Thanks for the gentle nudge back into the realm of real physics. The pressure is only constant after the pump, cause the pump is creating the pressure.

You can all give me a big ole celestial head slap now.

Thanks,
BrianHeston

BrianHeston

Kill No Cone - Out of curiousity, you mentioned specifically that electric pumps were pushers. Is there any way to hook up some other type of pump. I don't even know what other types there might be? Vacuum maybe? Let me know if you know any other options.

Thanks,
BrianHeston

Kill No Cone

iTrader: (6)

That is an interesting question…

I know that the high pressure rotary pumps as well as the diaphragm pumps are “pushers”, but the mechanical pumps found on a lot of 60s and 70s cars were probably more on the “puller” side of the spectrum. I guess you could pressurize your tank or something, but that could really cause a problem in an accident.

I think that there are a lot of places to focus a creative engineering mind when building a fast car. This may not be one of those places. There are a couple old stand by methods that work well with the fuel system.

One guy who really knows this stuff is Paul Yaw. If you read the material he writes about setting up a fuel system, you may be surprised who specific he is about setups. If you buy his carb, he will want you to use a specific fuel pump and fuel gauge. He knows how to make his fuel delivery systems do great things. But, you have to do it his way.

Good luck Brain!

ddsmith

Great, a subject I'm familiar with. Some pumps do not need a suction head from the height of the liquid above the pump suction. Normally positive displacement pumps draw pretty good meaning that you could mount the pump above the liquid height and it would draw the liquid up to the pump. Basically it pumps the air out and draws a vacuum in the line. The old mechanical pumps mounted in the engine compartment would be this type of pump. Now for the other beast. Electric pumps are normally centrifugal. They have an impeller and normally needs fluid above the level of the pumps suction. They have a big problem if vapor is formed in them because they do not do well at pumping air/vapor. It has to do with the pumps design. This causes cavitation were the low pressure area of the impeller forms the vapor because the liquid reaches it's boiling point at the reduced pressure and when the vapor moves to the high pressure area of the impeller the rapid increase in pressure causes the vapor bubbles to collaspe and damage the impeller. It sounds like the pump is pumping marbles. If this is carried one step further the pump stops pumping fluid. I guess I could go further but you've probably heard enough.

Don