Exactly--I run two pumps that can each reach 15 pounds static. I use the
cheap holley regulator because it seems to have a better flow rate than
the spendy, billet aluminum one I bought. I also run a very big, high flow
fuel filter--make sure you aren't using too small a filter or a clogged
one. I set my pressure at three pounds and it maintains three pounds at
full throttle @ 6000 rpm. Your regulator has to be able to flow well, and
it should be close to the carbs. Your lines should be AN6. You need lots
of excess pressure and flow before the regulator. If you don't, when the
regulator gets WFO (wide f#$@ing open) your pumps and the resistance of
everything in the fuel system will determine the pressure available at the
float valve. Don't forget that your float valve can also be the
bottleneck. It's a jet, and if it's too small you won't get the flow you
need at full power.
In a thirty minute race I use four gallons of gas. That's eight gallons
per hour--not an inconsiderable flow rate. A home faucet runs about five
gallons a minute or 300 gallons per hour. That means my car needs a fuel
flow rate about 1/30 the flow rate of a fully open faucet. I frequently
use my fuel pump to drain my fuel cell so I can tell how much gas I used
and avoid running with more than I need. I can fill a five gallon can in
about 15 minutes, which means without the regulator and most of the lines,
my "overkill" pumps are probably not that far from being maxed out in the
straights for a typical race. If you're running out of poop at the middle
to end of the straight it's not out of the question that you simply don't
pump enough fuel. The rest of the track is tiptoeing by comparison.
-----Original Message-----
From: Jack W. Drews [mailto:vinttr4@geneseo.net]
Sent: Monday, May 19, 2003 5:33 AM
To: Randy B. Williams; fot@autox.team.net
Subject: Re: Fuel starvation problem
I had exactly the same problem five years ago. You can measure the problem
with an egt gauge, though, because it does indeed go to zero when the
engine runs out of fuel on long straights. We chased it for two seasons
before we cured it. I tell people the answer, but folks just don't want to
believe it because ee don't know the theoretical reason(!!!!!!).
If you have an electric fuel pump and a regulator, and both of them are
near the same pressure, this happens. For example -- the Facet pump that
puts out maybe 5 psi and the NAPA regulator set to 3 psi. It will happen
quite often -- just on long straights.
You can fix it by using a Holley 15 psi pump and a Holley low pressure
regulator, regulated down to whatever you like. This eliminates the
problem.
There is another aspect to this as well. Watching your fuel pressure gauge
while you are running the car up on a chassis dyno is pretty interesting.
If the regulator is set at the "proper" 3 psi at idle, then by the time
the engine reaches 6000 rpm, the pressure may be near zero! I now run my
regulator at 7 psi, and at 6000 rpm, it is down to three. And, by the way,
although all the books and all the experts say not to run over 3 psi on
SU's, I now have 20 race weekends on my set of stock float valves, with no
leaks yet.
Hope this helps somebody.
At 04:23 PM 5/16/03 -0400, Randy B. Williams wrote:
>I recently purchased a TR3 from Richard Hardison and could sure use
>some help to sort out what I believe to be a fuel supply problem. It
>appears as though I am running out of fuel any time I have an extra
>long run at full throttle. Richard was also having this problem, so he
>had his mechanice, Ed Bernard, install a second fuel pump. What could
>the problem be and what suggestions can be offered to resolve it? The
>pressure after the regulator is only just slightly over 2 pounds????
>Randy Williams
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