fuel pumps

Technical discussion, questions, answers and information regarding the F600
Ken Van Horn
Posts: 173
Joined: Sun Mar 01, 2009 9:49 pm
Location: United States, Virginia, Powhatan

fuel pumps

Postby Ken Van Horn » Sun May 18, 2014 1:22 pm

If you are using or are planning to use a Walbro fuel pump, check the specs first. The 392 and 393 look identical but are not. The 392 is rated at 600 hp and high gpm. The 393 is the correct pump for our cars. Hyperacing sells only the 392. Their cars run on alcohol. The 392 will overheat you fuel, bloat your fuel cell and the pump will die. Use 6an return lines and the correct pump to avoid on track failures. Double check my numbers on the Walbro tech site to make sure I HAVE NOT REVERSED THE NUMBERS.
Happy racing
Ken
Ken Van Horn Novakar J9

Chris Ross
Posts: 286
Joined: Sun Jul 22, 2012 3:20 pm

Postby Chris Ross » Sun May 18, 2014 5:35 pm

Glad you brought this up Ken. The Walbro GSL 393 is the pump you want if you are running an external fuel pump. This pump still has plenty of excess capacity to run the 600's, but it isn't a crazy amount of excess like the 392 is. You need to have the fuel pump as close to the fuel cell as possible. Typically these pumps don't last as long if they have to pull a lot of suction to get the fuel from the tank. On my NovaKBS I had the fuel pump inside the fuel cell enclosure laying on top of the bladder right by the suction hook up and that worked well. If you are running an external surge tank then having the pump right by the surge tank and connected to the bottom of the tank will actually give you a positive head of pressure feeding the pump which works great. If you are running an internal pump inside your cell, do not use the GSS340 that Fuel Safe sells. This is the internal equivalent of the 392 and pumps way too much fuel. Use the Walbro F20000110. Physical dimensions are the same as the GSS340 so it will mount up as a direct replacement. The electrical connectors are swapped though so make sure you check this when you install it. The mating connector for the pump can be disassembled and the wires swapped in the connector.

You also need to look at the specs on the side of the pump and install the proper size fuse inline with the pump. If you don't have a fuse, the pump will continue to run as the bearings are failing generating a tremendous amount of heat as the pump is cooled by the fuel as it is burning itself up. Gasoline boils around 150 degrees or so it doesn't take a large amount of heat to start the gas boiling. Eventually the pump will seize up if you continue to apply power to it and at this point current draw will skyrocket until something in the electrical system melts and breaks the circuit. Do you really want electrical components in your fuel system melting? Any of your local autoparts store will have a simple inline bus fuse holder that can be installed with a couple of butt connectors in about 5 minutes.

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Another thing that I'm sure contributed to the pump failure was the heat from the header. Due to the close proximity of the header you need to block the heat from getting to the fuel cell. The best way to do this is with a solid one piece of heat shield material applied to the back side of the firewall/roll bar. This piece of heat shield needs to completely cover the fire wall and frame of the car with no breaks. The frame of the car will absorb the radiant heat from the header and transfer it forward into the fuel cell compartment. You also need apply a piece of heat shielding underneath the header from the firewall back to the engine block. It is easy to overlook this area, but the floor pan of the car will absorb that heat and transfer it forward underneath the fuel cell. I also like to place a piece of sheet metal on the drivers left side of the headers with heat shielding on it to block any heat from headers getting to the coolant tubing and jack shaft if you have one. I'm about to pull the engine one more time to finish up a few things in the engine bay and try to remember to take a few photos.

The product I like to use in the engine bay is called "Zero Clearance" from Thermal Control. Looks pretty typical with a high temp adhesive on one side, 1/8" of a fiber mat insulation, and then an aluminum skin. One nice thing about the Zero Clearance is the aluminum skin is reasonably thick so it has some stiffness and can hold a general shape if you have to fold it over a corner. It is pretty resistant to tearing the skin too. Some of the other stuff I have used the aluminum/mylar skin is so thin it is quite easy to tear it. I recommend you use something like this (there are several other competing brands if you want to find something local) that acts as both a radiant heat block (aluminum skin) and a conductive heat block (insulation) with the 1/8" mat. I would stay away from the really thin products (aluminum/mylar on a fiberglass cloth approx 1/16" thk or thinner) that only block radiant heat and don't provide any insulation for the engine bay. These thin products block radiant heat well, but they need generous air flow to keep cool. We generally don't have adequate air floor around the headers to flush out the hot air to minimize conductive heat transfer.

http://www.thermalcontrolproducts.com/i ... clearance/[/img]
Last edited by Chris Ross on Sat May 31, 2014 8:23 pm, edited 2 times in total.

Jim Murphy
Posts: 2654
Joined: Fri Mar 16, 2007 2:13 pm
Location: United States, Georgia, Winder

Postby Jim Murphy » Mon May 19, 2014 11:08 am

The above is just another reason to maximize your heat shielding around the headers/exhaust pipe all the way to the very end of the pipe. Start with ceramic coating both inside and outside the header and pipe (wrapping the header/pipe is recommended); the muffler will need heat shielding all the way around. Then heat shield whatever faces the header/pipe/muffler from the open space next to the chain IF it goes forward of the left side of the block to the bottom front face of the engine block and the back of the fuel cell/bars (and the bottom in front of the block mentioned above); the front of the valve cover high enough over the plug wires; then form a sort of a "open top tunnel" (three sided) of heat shield plates surrounding the pipe to the end. Whatever faces this "open top tunnel" gets heat shielding as well so that there are THREE layers of heat shielding - coating/wrapping of the exhaust - heat shield "open top tunnel" - and heat shielding of anything facing the "tunnel".

Last, IF the chain runs along the side of the engine block, place heat shielding between the chain and the engine block high enough that the heat does not come over the top of the shield. Excessive heat shortens the life of an expensive chain.

Air ducts to the engine compartment and chain drive along with an OPEN rear of the area covering the drivetrain will help the heat get out as quickly as possible.

If in doubt, heat shield it.

HTH,
Jim

Chris Ross
Posts: 286
Joined: Sun Jul 22, 2012 3:20 pm

Postby Chris Ross » Sat May 31, 2014 8:35 pm

I finally got some time to work on the car today. Here is a good picture of my engine bay without the engine showing the three pieces of heat shielding. You can see the one large continuous piece protecting the fire wall and all the frame members of the roll bar. The piece of heat shielding on the floor of the engine bay doesn't have adhesive on it, but it is surrounded on all sides so it can't move. It butts against the oil pan on the aft edge so all the frame members and floor pan of the car are isolated from the heat of the header. The heat shield on the left side is attached to a piece of aluminum sheet metal. This bolts to the fire wall and to the floor pan. This insulates your fuel lines on the left side of the car and if you have a jack shaft this will also protect your chain from the header heat also. If you have any doubts about your heat shielding an easy way to check is put your hand on your fuel filler neck, your metal seat back, frame members where your shoulder harness attaches. If you can't put your bare hand on these, then you probably need more heat shielding or you have a gap in your shielding.

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