Time for e85.. Have a few questions
- Thread starter wesking1
- Start date
how much of a timing change did you do
Ok that's not bad at all
TC do you remember your timing from your old 2.9 setup?
Lots of things effect a setups MBT.
Are you tuning the car yourself?
Are you tuning the car yourself?
No I don't tune my own car
Here is an interesting article about fuel line sizing. To run a smaller return on a return style system is going to cause trouble when driving the car at low power usages. The fuel needs to return with no restriction or aeration. You should also upgrade to the Fore FC3 Fuel controller to cycle the second pump off when under low power conditions.
L&M Engines
L&M Engines
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One size smaller return can be tuned to run quite well. Yes there will be more of a pressure droop from light load to fully loaded, but it's not that hard to account for.
It isn't about pressure drop. It is about unstable pressure changes at the fuel rail, due to a restriction in the return fuel line at low fuel demand conditions of the engine
Take 2 Walbro 465 pumps at 13.5 V, these flow 430LPH of E85 at 40 psi. 430 x 2 = 860 LPH from the tank to the engine. To give you a better idea of how much fuel this is lets do some more math.
ID1000 injectors flow 95Lbs of fuel an hour. E85 weighs roughly 6.8 lbs per gallon. 95 divided by 6.8lbs =13.97 gallons of fuel per hour at 100% duty cycle of the injector is the max fuel flow the engine can burn x 8 injectors = 111.764 gallons of fuel the engine can burn at 100% duty cycle of the injector each hour the engine is at max power and fuel delivery. Now we have pumps capable of moving 830 liter per hour of E85 at 40 psi. 830L divided by 3.785 = 219.28 gallons per hour of fuel flow from the tank to the engine at all times. 219.28 of fuel pumped -111.764 of fuel used = 107.516 gallons of fuel that must be returned to the tanks each hour at 100% duty cycle of the injectors.
Now to use a smaller return fuel line then the supply is to cause a pressure rise in the return line when you aren't using large amounts of fuel. Cruising at low speeds and engine loads the fuel return has to carry almost all of the 219.28 gallons of fuel back to the tank each hour. If the car achieves 13 mpg at a steady state cruise condition at 60 mph. That is the equavelent of 13 GPH of fuel usage. 219.28 GPH delivered to the engine, the return line must carry 206.28 GPH of fuel back to the tank each hour. To have a smaller return line during this condition is asking for a pressure rise in the whole system. A pressure rise in the return line also cause turbulence in the fuel as it returns to the tank. Turbulence causes aeration of the fuel, which will over time aerate the fuel in the tank. Aeration of the fuel in the tank causes unstable fuel pressures.
The cost difference between 20 feet of number 8 and number 10 return hose isn't enough to try and diagnose the problems at a later date in my mind.
This is also why I recommended the Fore FC3 Fuel Controller. You use this to shut the second pump off during these low fuel usage conditions. Why do you need to pump 219.28 gallons of fuel to the engine each hour, when you're only going to use 13 gallons of that? Shut one pump off and only pump 109.64 GPH. This will lower the heat rise of the fuel over time.
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One thing to remember is that nobody would run the injectors at 100% duty cycle. So the numbers I'm using are being generous versus the actual amount of fuel being used by the engine. So the return line will have to handle more fuel then what my math is showing at 100% engine power output
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You've seen this first hand?
-8 feed, -6 return here. The return dumps into the factory feed outlet from the stock hat. I ran 2' of 3/8" submersible fuel line from the under side of the hat into the tank positioning it over towards the fuel tank fill. Aeration can occur from the return spraying the fuel surface in the tank right around the pumps or sump...
I'm running a glenns sumped tank with dual Pro 044 pumps run external. Very stable fuel pressure.
I wasn't disagreeing with your statement. Equal size feed & return is better than a reduction in size of the return, but real world experience has proven that a reduced size return can work.
-8 feed, -6 return here. The return dumps into the factory feed outlet from the stock hat. I ran 2' of 3/8" submersible fuel line from the under side of the hat into the tank positioning it over towards the fuel tank fill. Aeration can occur from the return spraying the fuel surface in the tank right around the pumps or sump...
I'm running a glenns sumped tank with dual Pro 044 pumps run external. Very stable fuel pressure.
I wasn't disagreeing with your statement. Equal size feed & return is better than a reduction in size of the return, but real world experience has proven that a reduced size return can work.
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I've never played with these engines in this manner. I've played with diesel engines with a return style fuel system and the small fuel return lines with high flow fuel systems cause problems when the return isn't sized to equal or larger than the pressure supply line. Actually most of those systems we run a #6 pressure supply line with a #8 return. If I build a real high flow system it will be #8 pressure supply after the secondary high pressure pump with #8 return with a primary/auxiliary electric 260GPH transfer low pressure pump at the engine to feed the secondary high pressure pump on the engine with it own separate #8 return line. High flow for these engines is roughly around 220GPH at 120 to 135 psi. So these engines will have two # 8 return lines back to the tank. One from the engine and one from the primary/auxiliary pump. The primary pump output pressure is 17 psi to the secondary with its own pressure regulator for the return side of it. The high pressure regulator is after the fuel rail and is a gravity feed with no restriction to the tank. A standard flow system is roughly 90GPH at 90-95 psi
I'm taking what I've learned from building 2500Hp diesel engine fuel systems and using that knowledge to explain the possible problems that can occur with these fuel systems. Also the link to the article I posted basically says the same thing I'm trying to say. The writer is from L & M Engines who is a top Mod engine builder in the country
These cars are dealing with much lower fuel pressure, so the lines size needs to increase to maintain the volume at lower pressures
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