FMTV exhaust gas recirculation?

[tennmogger]

Does anyone know if the small hose and pipes which route from the exhaust tip ("deflector, air cleaner") back to the air intake filter is exhaust gas recirculation?

Can't find any notes in the main manual but the system shows up in the -24P parts manual, TM9-2320-365-24P, page 107, figure 31. Look at part 5.

If you have looked at your exhaust pipe tip (aka "deflector, air cleaner") you will notice the output is severely restricted to force exhaust gas toward the air cleaner.

Whatever the purpose (emissions) there's apparently exhaust gas being mixed with clean air for combustion, plus the exhaust is restricted. That seems like double whammy "not good" to me.

Has anyone thought about this? I'm probably going to remove the exhaust tip and see what difference that makes.

Bob

 

[Suprman]

I wondered about that too. Since the exhaust can go underwater and the truck still run. Wouldn't want water to get inadvertently sucked into the air box. Maybe it's some kind of a drain.

 

[PowerstrokeNC]

I think your general idea is correct. Early EGR
Also wonder if it has any effect on helping engine heat up quicker?

 

[Johno176]

I believe it is used to remove the large particle debris taken in throught the air intake by way of vacumn generated as the exhaust passes by the pipe fitted into the exhaust pipe.

 

[Shark Bait]

Some heavy equipment uses this technic to vacuum dust out of the air intake housing.

Dave

 

[tennmogger]

I believe it is used to remove the large particle debris taken in throught the air intake by way of vacumn generated as the exhaust passes by the pipe fitted into the exhaust pipe.

That's an intriguing suggestion. If I can measure the pressure in the tube between the exhaust and the air intake: 1) if tube pressurizes then exhaust gas is being forced toward the air intake,

or 2) if the tube shows a vacuum, then the idea is to clear debris out of the air cleaner.

Will report!

 

[Floridianson]

The Deuce A3 Cat motor has a tube a tube from the exhaust pipe to intake. At idle the intake sucks in and running sucks out. Believe as said first EGR to clean it up at Idle. Remove the tube and get a cig and watch the way the smoke goes at Idle or fast idle.
Not sure if the MVTV is that way but you can see it would cause a venture effect at high idle but suck in the intake when the gases are not moving.

 

[Duckworthe]

I believe it is used to remove the large particle debris taken in throught the air intake by way of vacumn generated as the exhaust passes by the pipe fitted into the exhaust pipe.

This is what my Guard mechanic told me it was for also. It removes a large amount of dust and debris to help keep the air filter cleaner longer. I looked into it because I cut, turned, and moved my exhaust tip further to the rear to make room for my generator mounting.

 

[Floridianson]

Yep the venture effect would do that.

 

[Oxyacetylene]

The item is called a "particulate tube" or something similar in the TM. I don't think they would have added it for EGR purposes as the trucks were produced with an EPA exemption anyway.

 

[Lmtv772]

I had the same thought about EGR, these trucks are exempt anyway. But the large particle thing makes sense. I guess do to the heat the exhaust gasses would pass faster through the exhaust than the intake air through the air intake. Therefore creating an area lower air pressure. Bernoulli's principle

 

[tennmogger]

Thanks for all the great information. I will not be modifying that exhaust tip after all!

 

[Floridianson]

If it was like I said then at start up idle then warm exhaust air would help in subzero temps? If it was for emissions then the EGR would be at all RPM levels.

 

[Overdrive]

I could be wrong here but the trucks are not EPA exempt... There is an EPA sticker on the engine and "EPA Exempt" is exactly the reason you cannot run a HUMVEE on the street (or at least what GP makes you sign when you get one at auction). It is my understanding that LMTV/FMTVs came with the correct emissions equipment as a similar civilian medium duty truck for the given year they were produced.... Then again, I could be all wet.

OD

 

[Lmtv772]

If it was like I said then at start up idle then warm exhaust air would help in subzero temps? If it was for emissions then the EGR would be at all RPM levels.

Not thing to do with EGR it's a large particle pre filter.

 

[coachgeo]

There is a post that somewhat explained how it works at: http://www.steelsoldiers.com/showth...Expo-today-!&p=1878490&viewfull=1#post1878490 While the pdf in that post is about a separate "pre-filter" unit of similar intentions.... appears the one on the FMTV setup has similar prefilter integrated into the filter housing. Donaldson does make the filter setup on these trucks.


FWIW thread linked from above contains lot of info on the air filter setup.

 

[Oxyacetylene]

I could be wrong here but the trucks are not EPA exempt... There is an EPA sticker on the engine and "EPA Exempt" is exactly the reason you cannot run a HUMVEE on the street (or at least what GP makes you sign when you get one at auction). It is my understanding that LMTV/FMTVs came with the correct emissions equipment as a similar civilian medium duty truck for the given year they were produced.... Then again, I could be all wet.

OD

The trucks, or the engine, do carry an EPA exemption. You may or may not recall a while back the DoD stopped selling surplus equipment to the public due to concerns over emissions and the EPA exemption. The premise was that the vehicles, generators, etc were made with these exemptions for national security...so they did not have to worry about restrictive emissions equipment or hinder the performance/design of said items. After a while, the EPA agreed that the exemption carried for the life of the vehicle, and they started selling the trucks and equipment again. There was a lot of discussion here on SS about all of that. From what I have read, these FMTV's do meet the emissions requirements for the year they were produced, as long as they are running on regular diesel. The issue is when you run them on some of the other fuels like JP8.

 

[HETvet]

You all must realize that EGR is NOT an EPA item. It's there to help cool the piston down. That's it. Under WOT the EGR valve remains closed for maximum power.

 

[lmtvjunky]

I'm think'n it's a block heater, it's the only natural way to warm the block up when cold, that's the best way to trash ur filter too, sucking exhaust?

 

[HETvet]

The Venturi effect pulls particulate matter out of the air box and in to the exhaust. What heats up the block is what's called open loop operation. The PCM sees that the ECT sensor (engine coolant tempature) is not at a predetermined temperature. So it increases injector pulse width (inject more fuel) to help accelerate engine warm up. Once the PCM sees the ECT sensor is reading operating tempature, it goes in to closed loop operation; taking in to account MAP (intake manifold absolute pressure), IAT (intake air tempature), TPS (throttle position sensor), and ECT reading to modulate injector pulse width for optimal injection quantity and Timming. That is the most basic description of how the engine warm up works. This applies for all modern automobiles.