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Thread: Finally bypassed the FDC in my deuce.

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    2 Star General ageregunner's Avatar
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    Default Finally bypassed the FDC in my deuce.

    Last week I bypassed the FDC in my 1971 M35A2. Today I finally got to take it out on a test run to see if the differences described in several Steel Soldiers posts, would apply to my truck. The difference in hill pulling was simply unbelievable. Hills that made me downshift all the way down to third gear, could now be pulled in fifth. My EGT display now has become a vital part of this truck, as I now can easily hit the 1200 degree F limit. But that being said, the improvement to the performance of this truck is amazing. Thanks for all the posts on bypassing the FDC. The procedures shown were easy to follow. I highly recommend all deuce owners to install EGT gauges on their trucks, and then bypass their fuel density compensators.
    Barry

    1971 AM General M35A2 W/W
    1989 Libby Welding MEP-002A
    MVPA #36115
    NRA Benefactor Member
    FFL Curio and Relics license holder

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    4 Star General rustystud's Avatar
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    Quote Originally Posted by ageregunner View Post
    Last week I bypassed the FDC in my 1971 M35A2. Today I finally got to take it out on a test run to see if the differences described in several Steel Soldiers posts, would apply to my truck. The difference in hill pulling was simply unbelievable. Hills that made me downshift all the way down to third gear, could now be pulled in fifth. My EGT display now has become a vital part of this truck, as I now can easily hit the 1200 degree F limit. But that being said, the improvement to the performance of this truck is amazing. Thanks for all the posts on bypassing the FDC. The procedures shown were easy to follow. I highly recommend all deuce owners to install EGT gauges on their trucks, and then bypass their fuel density compensators.
    Just be careful as now you have the ability to fry your pistons ! Just because you have a "Pyrometer" installed doesn't mean it cannot happen either. In just a moment pulling hard you can reach the critical temperature that will destroy your engine. I once had a Semi-Truck reach 1400 F in minutes pulling up I-5 . I just glanced down to the gauge and realized what was happening and let off the fuel in time. They do make Pyrometer alarms that you can buy.

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    dumpsterlandingfromorbit! gimpyrobb's Avatar
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    Well, at least with the pyro, he has an educated idea of whats going on inside.


    Just cause a truck is stock, that doesn't mean it won't fry something, especially if lugging the motor!

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    4 Star General cattlerepairman's Avatar
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    I have a pre-turbo thermocouple in my LDS. FDC is bypassed and I am still wary of the power it has. No way would I turn it up more, even though it seems to hardly get up to danger temps, ever. That thing pulls like a freight train. The key is to drive it right; downshift and keep the rpm up, do not torture it at low revs with the pedal mashed to the floor. Lugging sees the temps climb fast and even then, lifting the pedal just a tiny bit produces a noticeable drop in pre-turbo temps.
    MVPA member. 1974 M35A2C w/w "Queen Lola", rebuilt LDS-465-1A, "D" turbo, Waterloo Overdrive upgrade. Med towbar, 11.00R20 Goodyear G286, flipped hubs, remote brake fluid reservoir, bypassed FDC, LED taillights, LED headlights, LED turn signals, WESTACH EGT/boost gauge, AVM lockout hubs, LED convoy light, LED lollipop lights, HMMWV seat on air ride base, M211 dash passenger grab handle, hood lift kit, 24V solargizer/battery minder, ether start kit, flasher module mod, heavy duty dog bone ends, M35A3 aluminium fuel tank.

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    2 Star General ageregunner's Avatar
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    Quote Originally Posted by rustystud View Post
    Just be careful as now you have the ability to fry your pistons ! Just because you have a "Pyrometer" installed doesn't mean it cannot happen either. In just a moment pulling hard you can reach the critical temperature that will destroy your engine. I once had a Semi-Truck reach 1400 F in minutes pulling up I-5 . I just glanced down to the gauge and realized what was happening and let off the fuel in time. They do make Pyrometer alarms that you can buy.
    Thanks for the response, Rusty. My electronic EGT unit has an alarm, which I have set for 1100 degrees F. It lights a bright alarm light on the display, but after reading your reply, I will probably use the alarm contacts to energize a loud audible.
    Barry

    1971 AM General M35A2 W/W
    1989 Libby Welding MEP-002A
    MVPA #36115
    NRA Benefactor Member
    FFL Curio and Relics license holder

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    4 Star General FloridaAKM's Avatar
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    I bypassed the FDC in the '85 Deuce yesterday, but have not had a chance to drive it due to the missing HH parts that were broken. Floridianson suggested it since all of the injector lines were removed & it was just a matter of removing some fittings & lines &plugging them & lengthening the output of the secondary filter to the HH. If it works as well as you guys mentioned, I will probably do it to the '87 Deuce as well. I do have the necessary EGT gauges to help mind the temps while driving. Thanks for your reports.
    1985/87 M35A2C Wo/w Deuce x 2
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    4 Star General frank8003's Avatar
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    Quote Originally Posted by ageregunner View Post
    Last week I bypassed the FDC in my 1971 M35A2.~ My EGT display now has become a vital part of this truck, as I now can easily hit the 1200 degree F limit. But that being said, the improvement to the performance of this truck is amazing. ~ I highly recommend all deuce owners to install EGT gauges on their trucks, and then bypass their fuel density compensators.
    The FDC was stuck, [failed] as described by rustystud in copious notes.
    I was here, had a good time.

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    4 Star General Floridianson's Avatar
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    Quote Originally Posted by cattlerepairman View Post
    I have a pre-turbo thermocouple in my LDS. FDC is bypassed and I am still wary of the power it has. No way would I turn it up more, even though it seems to hardly get up to danger temps, ever. That thing pulls like a freight train. The key is to drive it right; downshift and keep the rpm up, do not torture it at low revs with the pedal mashed to the floor. Lugging sees the temps climb fast and even then, lifting the pedal just a tiny bit produces a noticeable drop in pre-turbo temps.
    Agreed if you lugging it will get hot fast.
    This is my GMC 3500 when I go to pass someone for just maybe 30 seconds.
    Attached Images Attached Images
    Real trucks don't have spark plugs! Me strong as bull smart as tractor. James

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    4 Star General cattlerepairman's Avatar
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    Quote Originally Posted by ageregunner View Post
    Thanks for the response, Rusty. My electronic EGT unit has an alarm, which I have set for 1100 degrees F. It lights a bright alarm light on the display, but after reading your reply, I will probably use the alarm contacts to energize a loud audible.
    I think you are very much on the safe side. The consensus from many threads seems to be that you do not want to see more than 1250-1300 pre-turbo, so you do have a little wiggle room.
    MVPA member. 1974 M35A2C w/w "Queen Lola", rebuilt LDS-465-1A, "D" turbo, Waterloo Overdrive upgrade. Med towbar, 11.00R20 Goodyear G286, flipped hubs, remote brake fluid reservoir, bypassed FDC, LED taillights, LED headlights, LED turn signals, WESTACH EGT/boost gauge, AVM lockout hubs, LED convoy light, LED lollipop lights, HMMWV seat on air ride base, M211 dash passenger grab handle, hood lift kit, 24V solargizer/battery minder, ether start kit, flasher module mod, heavy duty dog bone ends, M35A3 aluminium fuel tank.

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    Sergeant MudMarine's Avatar
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    Default

    Two questions,

    1. (On topic) where's the best place to get said EGT gauges from? I've seen some of the surplus aftermarket dealers here advertise their kits but those don't look like they come with any kind of alarm

    2. (Off topic)
    I keep forgetting to ask and haven't found a smoking gun thread, but the LDS motor is the one that give more power and RPM right? Part 2, what trucks came with LDS, 5-tons?

    Sorry for hijacking the thread a little!
    Last edited by MudMarine; 02-11-2019 at 20:34.
    1988 M35A2c

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