Don Wilson jr Posted January 21 Share Posted January 21 I hope someone can help. I have a ENDTB676 engine with the puff eliminator and trying to figure out line connections. The truck was disassembled for restoration and some of my air line and wire markers came off. The truck originally had the five speed manual (TR722). I removed and installed a allision HT 740D transmission that came off another Mack 300 engine. I am not sure if I am missing parts to make this work. Can anyone help. Thanks Don Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/ Share on other sites More sharing options...
mrsmackpaul Posted January 22 Share Posted January 22 ĪPuff limiter worked thru the gear box, depending on the gear you were in Dunno what they did with auto boxes, I would be guessing something was used to operate the puff limiter when a auto was used Is there a switch on the box the tells you what gear it's in that a solenoid to work a air valve ? Paul Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545446 Share on other sites More sharing options...
67RModel Posted January 22 Share Posted January 22 6 hours ago, mrsmackpaul said: ĪPuff limiter worked thru the gear box, depending on the gear you were in Dunno what they did with auto boxes, I would be guessing something was used to operate the puff limiter when a auto was used Is there a switch on the box the tells you what gear it's in that a solenoid to work a air valve ? Paul This is somewhat inaccurate. The puff limiter works off manifold pressure in the reversing valve on the intake manifold. Fuel pumps on trucks with a puff limiter system are full rack by default when the truck is stationary an parking brakes applied to aid in cold starting. Once the spring brakes are released, regulated chassis air is sent to the air cylinder on the injection pump. Once boost pressure is sufficient for full rack the boost pressure overcomes the air pressure supplied by the parking brake valve via the reversing valve that is tapped directly into the intake manifold. Boost pressure and chassis air pressure are always hydraulically "battling" each other in the reversing valve for control of the air cylinder in the injection pump. Once running, if the transmission is put into reverse and/or the low forward gear(s) the torque limiting valve is activated. It is piped from its location on the transmission up to the reversing valve (puff limiter) Once its activated it dumps the boost pressure to atmosphere that would normally build up in the system and allow full rack travel. By doing this rack travel is limited in both systems to protect the drivetrain in the low and reverse gears. Once the shift rails are moved to select a higher gear the torque limiting valve closes and allows boost pressure to build up and allow for full rack travel in the injection pump. The transmission (torque limiting valve) is part of the system but not the primary component. The torque limiting valve on the transmission is only there to protect the driveline. I would think by switching to an Allison and you could eliminate the transmission portion (torque limiting valve) of the system because the the torque converter in the Allision will provide a "cushion" to the driveline. Or just know how to use your right foot in low gear or reverse...... 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545451 Share on other sites More sharing options...
terry Posted January 22 Share Posted January 22 Were early puff limiters no connected to the transmission? Terry Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545457 Share on other sites More sharing options...
67RModel Posted January 22 Share Posted January 22 24 minutes ago, terry said: Were early puff limiters no connected to the transmission? Terry I don't know the history on them or how the system evolved over time. I was on a quest a year or so back to understand the LDA system on mechanically governed E7s and in the process came to understand how puff limiters work as well.... I never did find out if the torque limiting valve was only on Mack transmissions or if it was included on vendor transmissions as well. I just know how they work.... 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545458 Share on other sites More sharing options...
terry Posted January 22 Share Posted January 22 I don't know for sure, but it seems like the first puff limiters were not connected to the trans? terry Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545459 Share on other sites More sharing options...
mrsmackpaul Posted January 22 Share Posted January 22 5 hours ago, 67RModel said: This is somewhat inaccurate. The puff limiter works off manifold pressure in the reversing valve on the intake manifold. Fuel pumps on trucks with a puff limiter system are full rack by default when the truck is stationary an parking brakes applied to aid in cold starting. Once the spring brakes are released, regulated chassis air is sent to the air cylinder on the injection pump. Once boost pressure is sufficient for full rack the boost pressure overcomes the air pressure supplied by the parking brake valve via the reversing valve that is tapped directly into the intake manifold. Boost pressure and chassis air pressure are always hydraulically "battling" each other in the reversing valve for control of the air cylinder in the injection pump. Once running, if the transmission is put into reverse and/or the low forward gear(s) the torque limiting valve is activated. It is piped from its location on the transmission up to the reversing valve (puff limiter) Once its activated it dumps the boost pressure to atmosphere that would normally build up in the system and allow full rack travel. By doing this rack travel is limited in both systems to protect the drivetrain in the low and reverse gears. Once the shift rails are moved to select a higher gear the torque limiting valve closes and allows boost pressure to build up and allow for full rack travel in the injection pump. The transmission (torque limiting valve) is part of the system but not the primary component. The torque limiting valve on the transmission is only there to protect the driveline. I would think by switching to an Allison and you could eliminate the transmission portion (torque limiting valve) of the system because the the torque converter in the Allision will provide a "cushion" to the driveline. Or just know how to use your right foot in low gear or reverse...... A far better and more accurate description than mine But still not answering what actually happens when a Allison auto is fitted Is the line to the transmission on a Maxitorque box just capped off I thinking that what ever is done for a Road Ranger would be the same as for the Allision auto Clearly I don't know but someone must be able to answer this accurately Anyone have a air diagram that ahows what happens ? Paul Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545462 Share on other sites More sharing options...
Don Wilson jr Posted January 22 Author Share Posted January 22 Guys, I don't remember any air or electric wires running to my five speed transmission. Unfortunately I got rid of the trans a long time ago, just not enough room to keep everything. I just need to know if I can make the Allison work. The truck is just a big toy and will not be used for anything other than a truck or tractor show. I have been working on this for several years. I need to get it done before I forget where everything goes. The reversing relay on my truck has one 1/4 air line fitting and a 12 volt pressure switch. The line ran back to the fire wall to a tee, one ran the the discharge side of the park brake and the other line, I don't remember, my location tag fell off. I can take some pics for you guys if it would help. Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545469 Share on other sites More sharing options...
MACKS Posted January 22 Share Posted January 22 You don’t really need it,but I guess u already know that.. Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545470 Share on other sites More sharing options...
Don Wilson jr Posted January 22 Author Share Posted January 22 I would like to try to use it if possible. Would I have any problems by just capping it off. Will have a lot of black smoke or any other potential problem? Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545472 Share on other sites More sharing options...
MACKS Posted January 22 Share Posted January 22 3 minutes ago, Don Wilson jr said: I would like to try to use it if possible. Would I have any problems by just capping it off. Will have a lot of black smoke or any other potential problem? The black smoke will roll only when and if u stomp on the throttle,if u take it easy very little black smoke.. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545473 Share on other sites More sharing options...
JoeH Posted January 22 Share Posted January 22 You get black smoke til the turbo hits 10-15 psi. Then it clears up. No big deal. I have one truck that's still roadworthy with this same engine, the puff limiter just stopped working a couple years ago so we just capped it off, which I believe just involves pulling the aneroid valve (reversing relay) off the rear intake manifold and putting a plug in instead. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545474 Share on other sites More sharing options...
JoeH Posted January 22 Share Posted January 22 I think the brass fitting cracked that threaded into the intake manifold, and it has some sort of a filter screen in it and it was seized into the manifold, so we just deleted it. This truck doesn't have the transmission torque switch, but we had an identical truck one year newer that did. My dad says you'd hear a click when you shifted into 5th and the truck would kick you in the butt. The transmission switch is unnecessary. The whole system is unnecessary at this point. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545475 Share on other sites More sharing options...
Don Wilson jr Posted January 23 Author Share Posted January 23 I think that the local Mack dealer got me straight. I will give it a try. Thanks for all the help. Thanks Don Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545512 Share on other sites More sharing options...
1961H67 Posted January 24 Share Posted January 24 Just a little early emission system, Mack had the Puff limiter, Cat the Air fuel ratio diaphragm , Cummins the Android diaphragm , I’m Unsure what the old 2 cycle Detroit used in the 70s & 80s ; but all these just held the rack/fuel psi back until the turbo built boost so you didn’t get that black “ Puff “ . 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545517 Share on other sites More sharing options...
Brocky Posted January 24 Share Posted January 24 (edited) And my shiny 290 with the android valve removed on the 335 pump, "with a touch of Dutch", would out run most 350's!!!! BUT you had to shift by the pyrometer NOT the Tach!!! Edited January 24 by Brocky 1 Quote Brocky Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545518 Share on other sites More sharing options...
mrsmackpaul Posted January 24 Share Posted January 24 Removing the puff limiter was found that the diesel would wash all the oil from the bore and cause premature wear Anyway, I dunno my as from elbow Paul 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545531 Share on other sites More sharing options...
MACKS Posted January 24 Share Posted January 24 3 hours ago, mrsmackpaul said: Removing the puff limiter was found that the diesel would wash all the oil from the bore and cause premature wear Anyway, I dunno my as from elbow Paul Well it definitely added soot to the oil,even after a fresh oil change the oil would turn black within minutes.. Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545534 Share on other sites More sharing options...
1961H67 Posted January 25 Share Posted January 25 “ Rolling Coal “ between gears with it blocked off ! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73776-puff-eliminator-on-1976-r-model/#findComment-545563 Share on other sites More sharing options...
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