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914World.com _ The Paddock _ Fuel starve in AX sweepers
Posted by: ChrisNPDrider Aug 19 2013, 01:34 PM
So this Saturday I dusted off the 914 and did an AX race after more than a year of being "too busy" w my great job at www.seaturtles.org
I've ALWAYs shown up to the AX w less than a quarter tank of gas. I have a 1972 1.7 w stock D-jet and aftermarket intake and exhaust. Stock fuel pump, OE low rear mounted, stock gas tank and lines but with evap system on top of fuel tank completely removed (recently).
So, on runs 2-5 I get a period of "no power" after each of the long, fast sweeping left and right turns. Ok, either I have a fuel problem, or ignition. All wires solid, so I drive out and get 4 gallons of gas.
More gas = Problem solved! 
I'm posting because I used to always do AX races w barely any gas and have never had this problem. Any ideas on why I had this problem? Fixes to improve for next time?
Thanks!
Posted by: Woody Aug 19 2013, 02:20 PM
So this Saturday I dusted off the 914 and did an AX race after more than a year of being "too busy" w my great job at www.seaturtles.org
I've ALWAYs shown up to the AX w less than a quarter tank of gas. I have a 1972 1.7 w stock D-jet and aftermarket intake and exhaust. Stock fuel pump, OE low rear mounted, stock gas tank and lines but with evap system on top of fuel tank completely removed (recently).
So, on runs 2-5 I get a period of "no power" after each of the long, fast sweeping left and right turns. Ok, either I have a fuel problem, or ignition. All wires solid, so I drive out and get 4 gallons of gas.
More gas = Problem solved!
I'm posting because I used to always do AX races w barely any gas and have never had this problem. Any ideas on why I had this problem? Fixes to improve for next time?
Thanks!
switch to carbs.
Posted by: Randal Aug 19 2013, 06:20 PM
Slosh boxes and foam work great.
Posted by: SirAndy Aug 19 2013, 08:18 PM
I'm baffled ...
Posted by: plays with cars Aug 19 2013, 09:39 PM
I'm baffled ...
Posted by: Racer Aug 20 2013, 07:56 PM
Um, don't run sticky tires? 
fwiw, I couldn't run below 1/4 tank in my '70 w/o starvation problems. I just ran 1/4-1/3 tank. An extra gallon or two sure prevents frustration and slower times despite any weight penalty.
Posted by: McMark Aug 21 2013, 09:23 AM
For AX you could probably get away with mounting a small fuel cell in the front trunk with a selector valve to shut off the main tank.
Like http://www.summitracing.com/parts/jzp-250-003-nf/overview/
Posted by: brant Aug 21 2013, 01:26 PM
fuel accumulators work wonders too....
I haven't really heard much of a problem with stock stuff in autox though
surprised (But perhaps I'm misinformed) that your having this problem
Posted by: ChrisNPDrider Aug 21 2013, 01:51 PM
I haven't really heard much of a problem with stock stuff in autox though
surprised (But perhaps I'm misinformed) that your having this problem
Me too!
Over a dozen races w no issues and always w very little fuel
More testing is needed
Best check my local AX calendar and go racin again
I have fun, but it's kinda depressing being on the back half of the standings.
If only PAX was horsepower alone, it'd be top 10 since I have ~90 HP
Posted by: Racer Chris Aug 22 2013, 06:33 PM
I haven't really heard much of a problem with stock stuff in autox though
surprised (But perhaps I'm misinformed) that your having this problem
Me too!
Over a dozen races w no issues and always w very little fuel
More testing is needed
Best check my local AX calendar and go racin again
I have fun, but it's kinda depressing being on the back half of the standings.
If only PAX was horsepower alone, it'd be top 10 since I have ~90 HP
I always ran an accumulator when I road raced with a d-jet injected engine.
Low pressure pump to keep a 1 quart cylinder filled with fuel and the stock FI pump to deliver fuel to the engine. Overflow from the FI system went back to the accumulator and a top fitting on the accumulator returned any excess to the fuel cell (tank).
Posted by: grantsfo Aug 22 2013, 08:02 PM
My Z has four scavenger pumps feeding an accumulator. Fuel starve what's that? I never ran less than 1/4 tank in my stock 914 tank - the weight up there in ax is good too!
Posted by: r_towle Aug 27 2013, 12:02 PM
So this Saturday I dusted off the 914 and did an AX race after more than a year of being "too busy" w my great job at www.seaturtles.org
Old fuel.
So, on runs 2-5 I get a period of "no power" after each of the long, fast sweeping left and right turns. Ok, either I have a fuel problem, or ignition. All wires solid, so I drive out and get 4 gallons of gas.
More gas = Problem solved!
Fuel filter replacement time.
Posted by: dlestep Oct 3 2013, 08:01 PM
I know that this was awhile back, but I was compelled to respond.
With fuel starvation problems, one might look to the off-road endurance setups.
In the 80's, a simple change to the carbs was the way to go.
The floats were removed and a plate added to cap-off 90% of the bowl.
I ran two pumps, one pressurizing the bowls, the other scavaging / fuel return.
or
fuel injection, mechanical or electrical.
Posted by: Heater Guy Oct 4 2013, 02:46 PM
Attached is a photo of a fuel collector. The low pressure fuel pump is always scavenging fuel from the tank and pumping it into the one quart container. On top of the container is a line back to the fuel tank. This keeps the container full. The high pressure or another pump supplies fuel to the fuel injectors or carbs. This system prevents fuel starvation no matter how much cornering you do. I can run my tank down to 1 gal.and never have a problem. This system is used on many hard corning cars like Toyota Atlantics and D Sport Roadsters.
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