Power difference after FDC bypass

[67Beast]

My truck had been like others recently making oil. Well I figured it was the FDC letting diesel into the crankcase. After reading up on it here on SS I found a good diagram showing the bypass. Now my deuce has been a good running deuce even though as far as I can tell it has never had the pump turned up (still safty wired). I had read that after a FDC bypass the pump would have to be adjusted. Well after doing the bypass and not adjusting the pump, this truck now rips! It's still tops out at 2650rpm and 57/58 mph but man does it get there a lot quicker. It is a noticable increase in power as you go though the gears while driving. Now not having a pyro gauge on the exhaust temps I can't tell how hot it's getting, but judging by the smoke from the stack I feel it is burning OK. When you accelerate hard you get a nice plum of dark grey smoke, not black, and once the load is off, it thins out and becomes clear. I'm real happy with the out come and it doesn't bother me to lose the multi option, as I have only been running diesel in it anyway.

 

[acetomatoco]

You may have to plumb the plum to get a plume of smoke..When we went to the one fuel Army, there was no longer a need for the FDC.. ACE

 

[rdixiemiller]

If my understanding of the FDC is correct, when you bypass it it goes into the "gasoline" delivery mode. If it doesn't run too hot with the FDC bypassed and a tank full of diesel, you should be able to run gasoline in as well. You would see a power drop, due to the difference in BTU content of gasoline. I think the FDC was supposed to give consistant power with a wide variety of fuels. With it bypassed, it will be strong with diesel, weaker with gasoline, but still safe to operate..

 

[Armada]

I have only run out of fuel once in a duece I had. The fuel gauge was mis calibrated by over a quarter tank. Anyway, it died as I was coming up on a fuel station. It took a few stalls and restarts to get it to the station and they did not sell diesel. The FDC had been disconnected. So whats a guy to do? I put almost 20 gallons of gasoline in it and 2 quarts of motor oil to act as IP lube. Now I didn't have a pyro hooked up, but performance wise you could not tell the difference between gas and diesel. Granted, there was still a little diesel sloshing around in the tank when it had run out, but the mixture was definately more gas. No change in exhaust either.

 

[Lax]

Okay guys. I always thought that once the FDC is bypassed I was stuck with just diesel. That is okay but I really really liked the idea of being able to burn ANYTHING (almost) if I had to in a pinch. What is the deal hear? My FDC is bypassed I'm pretty sure, so I have only run diesel since I have owned it. Could I run anything in it as long as I throw a gallon of oil in the tank??? Please advise. Thanks a ton!

 

[alphadeltaromeo]

Agreed with Lax. I just don't want the performance, but the flexibility in lower my cost of ownership by leveraging alternate fuel sources.

67Beast...can you provide the diagram showing the bypass? I'd like to review that for my own edification.

Much appreciated - Andy

 

[BFR]

is there a TM or mwo that deals with bypassing the FDC?

 

[Westech]

The fdc does not make it a multi fuel. you still can run any mix of gas, oil, diesel you want. its fdc was there to make all the fuels perform close to the same. if you bypass it its still a multi fuel

 

[gimpyrobb]

Yup, my understanding is its a density comensator. It varies how much fluid is allowed into the motor to keep output the same.

 

[Lax]

That sounds very cool. Please tell me how it stays that way and what I have to do to run well with different fuels. Thanks.

 

[gimpyrobb]

Bjorn has listed the BTU values of different fuels before. Find those and you can confidently mix your fuels to have the same power out put. Or you can leave the FDC hooked up. Do you have a pic of your I.P.? It is easier to tell for sure if yours is bypassed.

 

[67Beast]

Agreed with Lax. I just don't want the performance, but the flexibility in lower my cost of ownership by leveraging alternate fuel sources.

67Beast...can you provide the diagram showing the bypass? I'd like to review that for my own edification.

Much appreciated - Andy

It's in this link about half way down and posted by Bjorn http://www.steelsoldiers.com/index....t=0&postdays=0&postorder=asc&highlight=bypass

 

[alphadeltaromeo]

Excellent....thanks much

 

[ken]

The FDC's main job is to keep power output the same no matter what fuel you are burning. With gas it should increase the rate. Witch should keep the power output very close so as the driver/operator doesen't notice a thing in performance. But on gas mine trucks milage drops like mad! I tried gas in a emergency. Truck ran ok but it drank gas like crazy!! When i got to a lager town i refilled with diesel. Now i run a lot of used motor oil. And the FDC Must be cutting the rate. The power is about the same but there is a difference in milage. Bottom line, you still have a multifuel. But power and milage should vary wildly with different fuels.

 

[alphadeltaromeo]

Ken - What is the difference in mileage that you are seeing when you're running used motor oil and also, what ratio?

Appreciated - ADR

 

[Ferroequinologist]

Could one hook up a bypass for the FDC, and have the FDC connected at the same time? Just putting a valve in the inlet to the FDC and in the bypass, so you could run straight, or run FDC if you wanted just by opening and closing a couple of valves?

 

[cranetruck]

The FDC's main job is to keep power output the same no matter what fuel you are burning.....

Actually only true for the fuels listed in the TM. Not all fuels have the same relationship between BTU value and viscosity.
Biodiesel, for example, has a lower BTU value than #2 diesel and the FDC reduces the delivery...
Density and viscosity may be related, but it's the viscosity that matters. It is really a fuel viscosity compensator.

BTW, heating the fuel is a great way to get more fuel delivered to the IP.

 

[OPCOM]

Could one hook up a bypass for the FDC, and have the FDC connected at the same time? Just putting a valve in the inlet to the FDC and in the bypass, so you could run straight, or run FDC if you wanted just by opening and closing a couple of valves?

probably no reason why that would not work, except I believe they adjust the IP when bypassing the FDC so your power cpuld change.

 

[ken]

Alpha, I'll do a real world test for you to see milage differences. My ruck spends alot of time in the woods so milage is had to keep tract of. But i could do it by engine hours. The next road trip i'll get some better numbers. And the mixture is determined by the price of diesel. If it's high then alot more oil goes in. When it drops alot more diesel gets burnt.
Right now Biodiesel is 2.49 a gallon. Diesel is 2.69 a gallon. And the oil is free! But i try to keep it at about 30% oil max. It could probally handle more but it runs pretty well at 30%. And as they say on TV "your results may vary"

 

[rdixiemiller]

I hooked up a K thermocouple and my Fluke 87V after I bypassed the FDC. My truck will definately need the fuel rate decreased. I can hit 1400 in just a few seconds when I get into it hard. It wants to jump right over 1100 degrees with no provocation at all! I guess I'll turn it down a turn and try it. If I didn''t have the meter on the truck, it would be really easy to burn the engine up.
It's a shame, it runs like a scalded dog right now!