| Author | Message | ||
| Roger Jendrusina (Rogerj)
Registered Member Username: Rogerj Post Number: 8 Registered: 8-2001 Posted From: 69.82.219.30 Rating: N/A |
I recently put Jakes on a DD 6-71. I have driven with the Jake installed for about 5,000 miles. I usualy keep the Jake off and turn it on when needed. Recently I noticed a pretty good amount of black smoke from the exhaust pipe when the Jake was active. I did not notice this before and not sure if the smoke is something to be concerned about. The black smoke is more visible than the trace amount I see when accellerating. Is it normal or do I need to dig deeper into the engine. Roger | ||
| Bill Gerrie (Bill_gerrie)
Registered Member Username: Bill_gerrie Post Number: 73 Registered: 3-2006 Posted From: 209.50.73.34 Rating: N/A |
Roger Check to make sure your accelerator is completely off with no fuel going into the engine when Jakes are on. Bill | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 74 Registered: 7-2006 Posted From: 4.240.141.41 Rating: N/A |
Roger...we have the same situation; been that way for years.....I always thought it was "normal" Thanx for opening this thread.  RCB '64Crown Supercoach (HWC) | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1836 Registered: 1-2001 Posted From: 75.108.87.29 Rating: N/A |
I suspect that your buffer switch is not correctly adjusted and is holding the rack open a little bit allowing fuel to enter the cylinder. Since the Jakes open the exhaust valve and no combustion can occur, then the fuel is exhausted as black smoke. It is my opinion that no black smoke should be visible when operating the Jakes. The buffer switch should only hold the rack open a maximum of 25 rpm from idle. Richard | ||
| Douglas Wotring (Tekebird)
Registered Member Username: Tekebird Post Number: 108 Registered: 10-2004 Posted From: 71.59.75.212 Rating: N/A |
I thought the jake held the exhaust valve closed....hence the compression/engine braking | ||
| Bill Gerrie (Bill_gerrie)
Registered Member Username: Bill_gerrie Post Number: 76 Registered: 3-2006 Posted From: 209.50.74.35 Rating: N/A |
Doug The Jake Manual describes the operation as follows: Energizing the Engine Brake effectivly converts a power producing diesel engine into a power absorbing air compressor. This is accomplished through motion transfer using a master-slave piston arrangement which opens cylinder exhaust valves near the top of the normal compression stroke, releasing the compressed cylinder charge to exhaust. The blowndown of compressed air to to atmospheric pressure prevents the return of energy to the engine piston on the compression stroke, the effect being a net energy loss, since the work done in compressing the cylinder charge is not returned during the expansion process. Right from DA book. Bill | ||
| Douglas Wotring (Tekebird)
Registered Member Username: Tekebird Post Number: 110 Registered: 10-2004 Posted From: 71.59.75.212 Rating: N/A |
cool never would have figured without a sitdown and a bunch of energy consuming thought. Thanks | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1044 Registered: 5-2001 Posted From: 65.74.69.234 Rating: N/A |
Richard, with no compression, how would you get black smoke? If fuel was injected, it would have to be white smoke. I wonder if one of the master hydraulic units is not operating, so that one or two cylinders are firing while the rest are braking. I don't know the right answer to his question, but I have noticed smoke from time to time, and it has always been light colored. Perhaps someone who know these units better then I do might have an idea. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 302 Registered: 11-2005 Posted From: 206.40.238.19 Rating: N/A |
Doug, In other words the exh valve is closed on the compression stroke and open at the end of the comp stroke!! Kind of like firing an air cannon, thus that beautiful sound that small towns at the bottom of long hills love. | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1837 Registered: 1-2001 Posted From: 75.108.87.29 Rating: N/A |
Tom Caffrey, You may be correct.That one Jake solenoid is not opening the exhaust valve and that particular cylinder is firing. I do not understand why there would be black smoke though. When you turn the Jakes on low and half of the cylinders are firing and half are not, it does not generate black smoke. Richard | ||
| Bob greenwood (Bob_greenwood)
Registered Member Username: Bob_greenwood Post Number: 706 Registered: 7-2006 Posted From: 64.136.49.228 Rating: N/A |
black smoke is unburned fuel | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 75 Registered: 7-2006 Posted From: 4.240.213.144 Rating: N/A |
FWIW...I do not have a low/high, Jake...I flip the switch from off to on and immediately "it", the Jake, is in operation. Black smoke pours out of the exhaust, normally....some times, does not. RCB | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1838 Registered: 1-2001 Posted From: 75.108.87.29 Rating: N/A |
Chuck, I would suggest you check the adjustment of the high idle and buffer switch. Richard | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 90 Registered: 8-2006 Posted From: 207.231.81.154 Rating: N/A |
Chuck, The simple answer here is semantics! WHITE smoke is UNBURNED fuel, (actually fuel vapor) which is what we get on cold mornings with no block heat. BLACK smoke is PARTIALLY burned fuel. If the Jake dash switch is on, and the buffer switch is "on" with the fuel rack anywhere out of the no fuel position, fuel will be injected, immediately followed by exhaust valve opening, which means black smoke. I would like to know what happens when the Jake switch is turned on at idle? Absolutely NOTHING should happen, if anything besides the click of the dash switch is heard, go to the buffer switch and adjust... A far out thought could be an injector leaking badly, or a rack with an injector WAY out of adjustment, which is still injecting fuel even though the governor has the rack in the no fuel position? There is a few hundredths difference in the rack position between no fuel and idle, so proper adjustment of the buffer switch is critical. As explanation, the buffer switch "feels" the fuel rack, and only allows Jake operation when the rack is absolutely in the NO fuel position. This only occurs when the engine is being turned by the transmission at a speed higher than the throttle setting. As soon as the governor moves the rack to keep the engine idling, the buffer is supposed to stop the Jake. Two speed Jakes don't cause black smoke either, because, as above, the fuel rack must be in the NO fuel position for the Jake to operate. White smoke while in Jake operation is oil smoke, due to no compression keeping the oil below worn rings. Now, I made a mis-statement in my post on essentially the same topic under "estimated fuel mileage" I believe, (the saga of the $560 4515 and its impending trip from Washington to Texas?) I said a diesel has no compresion braking, as a warning to them not to have a runaway downhill. Someone else said "another poster has it all wrong." I hope these two posts have cleared up the confusion, but both me and Bill put one wrong word in the first time. Our Jake operation explanations SHOULD have said something to the effect of "opening the exhaust valve(s) at the top of the compression stroke releases the pressure that would have re-invested energy to the engine on the POWER stroke. (A lot of energy is consumed compressing the air on the compression stroke, but without Jakes, the same pressure pushes the piston down on the power stroke, with a net result of nothing.) We are ignoring friction loss, heat loss, and auxiliary loads. HTH, George (Message edited by George Mc6 on February 20, 2007) | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1839 Registered: 1-2001 Posted From: 75.108.87.29 Rating: |
Thanks George for a great explaination. Richard | ||
| Roger Jendrusina (Rogerj)
Registered Member Username: Rogerj Post Number: 9 Registered: 8-2001 Posted From: 69.82.253.185 Rating: N/A |
Thanks for all the great feedback. The buffer screw could easily be the problem as I had to replace a stuck injector this past December. I did the work in a campground and reset both the idle and buffer screws in the process of running the rack. I will start by backing out the buffer screw. I make every effort to keep the increase in idle speed to less than 15 RPM while also trying to eliminate any engine speed fluctuations. I may have tweaked the screw too much while correcting for engine roll. Roger | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 94 Registered: 8-2006 Posted From: 207.231.81.154 Rating: N/A |
Roger, Thank you for the feedback, we all like to know when our long range diagnoses are correect. Richard, thanks for the thanks! George | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1047 Registered: 5-2001 Posted From: 65.74.69.234 Rating: N/A |
Richard and George, you both have made good points! On thinking about it for a bit, I realized that I was guilty of generalizing with a specific condition. I don't know the exact point that the exhaust valve opens when the Jake is working, but I remembered that injection begins quite a bit before top center, so if any fuel should be injected, it could well be ignited by the compression that was developed before the exhaust valve pops open. From that, I can see that if any fuel is injected when the Jakes are on, the smoke could have any variation of white to black, depending on the timing and the amount of fuel. Considering the speed that the exhaust pulse must have when the valve pops open, I can see that it might dislodge almost anything that was inside the exhaust system. That leaves us with some interesting possibilities. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1842 Registered: 1-2001 Posted From: 75.108.87.29 Rating: N/A |
Tom, quite interesting to try and determine what could possibly happen when something goes wrong and you can not even see it isn't it? LOL Richard | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 76 Registered: 7-2006 Posted From: 4.240.213.147 Rating: N/A |
WOW>>>>>who would not agree this is the best of the best. Thanx for great, in depth conversation and advice. I, for one, appreciate all the helpful comments on topics such as this one. Thanx Ian and thanx participants. FWIW... RCB | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1844 Registered: 1-2001 Posted From: 75.108.87.29 Rating: |
I believe one of my earlier posts needs to be modified: "I suspect that your buffer switch is not correctly adjusted and is holding the rack open a little bit allowing fuel to enter the cylinder. Since the Jakes open the exhaust valve and no combustion can occur, then the fuel is exhausted as black smoke." It should have stated that "only partial combustion can occur before the exhaust valve opens" Richard | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 305 Registered: 7-2005 Posted From: 69.19.14.21 Rating: N/A |
"only partial combustion can occur before the exhaust valve opens" Kinda, As long as the buffer switch is in the closed position the jake solenoids energize and hold the exhaust valve in the open position (via oil pressure)until the circuit is opened. The smoke that you are seeing is a open rack, leaking or poorly set injector/injectors condition as previously stated. | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1845 Registered: 1-2001 Posted From: 75.108.87.29 Rating: N/A |
"As long as the buffer switch is in the closed position the jake solenoids energize and hold the exhaust valve in the open position (via oil pressure)until the circuit is opened." Dale, I do not think so. If the exhaust valve was held open all the time then there would be no compression build up to then be released when the piston is at top dead center. Richard (Message edited by drivingmisslazy on February 22, 2007) | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 79 Registered: 7-2006 Posted From: 4.240.141.123 Rating: N/A |
Re my earlier post in this thread about black smoke problem for years....today I started the engine. Warmed for quite a while....ran it up then back to idle. 20 minutes or so for the process, maybe more. At idle, turned the Jake switch on...the engine wanted to kill. I wrote a post about this several years ago, but not much information forthcoming. (see Archives). Drive up to a stop light with the Jake on, the enginge will kill. Gerorge...I am ass u me ing this is what you referred to? Thanx. RCB | ||
| Bob greenwood (Bob_greenwood)
Registered Member Username: Bob_greenwood Post Number: 731 Registered: 7-2006 Posted From: 64.136.26.228 Rating: N/A |
jake brakes in town,where were you San Francisco | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1051 Registered: 5-2001 Posted From: 65.74.64.246 Rating: N/A |
RCB, our Jakes would shut off even before we had a buffer switch. I was told that it was because oil pressure at hot idle was too low to pop open the valves. Tom Caffrey | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 306 Registered: 7-2005 Posted From: 69.19.14.25 Rating: N/A |
Richard "Dale, I do not think so. If the exhaust valve was held open all the time then there would be no compression build up to then be released when the piston is at top dead center." OK Had this same discussion with a fellow at work. WHAT controls the "timing" of the jake head to pop the exhaust valve open each time at top dead center through 15 piston strokes?? Now go out to your bus take a valve cover off, cross the tranny switch (if you have an auto), wind the engine up and let the jakes hit. Keep a close eye on one of the jake heads and tell me what you see. I know, I made money off the bet. To make a jake head that would open and close an exhaust valve (as you say)would have to have a way to control the timing of that operation for each cylinder. It's possible with these old 2 strokes, but it would require someway to monitor crankshaft timing to send a signal to open and close the electrical solenoid on the jake head. Now think about a 2 stroke system for a 6V. 1 head will have a control jake head and 2 slave jake heads. WHAT controls the "timing" of the slave jake heads?? The slaves don't have a solenoid to activate them. The slave heads activate from the control head solenoid. The compression build up is achieved by the amount the exhaust valve is held open. If the jake head is adjusted to hold the exhaust valve open slightly you will have more compression trying to escape around the partially open exhaust valve. Now if the exhaust valve is held open more you will have less pressure trying to escape and will be less engine braking. Hope this clears it up. Dale | ||
| Bob greenwood (Bob_greenwood)
Registered Member Username: Bob_greenwood Post Number: 732 Registered: 7-2006 Posted From: 64.136.26.228 Rating: N/A |
maybe I don't understand jakes...seems in my little head,that if you are screwing with WHEN the valves open, you are eliminateing those cylinders from a working engine,meaning you are running on two or three cylinders.. DON'T everybody jump on me...but WHY would you have jakes on except when you are going down a steep hill ???? guess "I JUST DON'T GET IT" | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 308 Registered: 7-2005 Posted From: 69.19.14.23 Rating: N/A |
Hey Bob, The jakes are only activated when you have let off the throttle. Then a switch is closed and allows the jakes to be energized. That robs power from the cylinders to help slow you down. If you add throttle (any at all) the jakes are disabled. The switch to control the jakes on the dash is the one that folks are talking about leaving on. Jakes have at least 2 switches(depends on the vehicle). 1 on the dash (master control)and 1 in the throttle circuit to actually activate the jake head solenoids. | ||
| Bob greenwood (Bob_greenwood)
Registered Member Username: Bob_greenwood Post Number: 733 Registered: 7-2006 Posted From: 64.136.27.228 Rating: N/A |
I DO UNDERSTAND THAT...read my question again | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 309 Registered: 7-2005 Posted From: 66.82.9.55 Rating: N/A |
Saves on service brake wear and adjustment, Saves on driver fatigue, More comfortable for passengers instead of stabbing the brakes everytime you are 5 or 10 miles over the speed limit. Probably some other reasons also I love mine and use them just about all the time, but I have a quiet exhaust. | ||
| Len Silva (Lsilva)
Registered Member Username: Lsilva Post Number: 88 Registered: 12-2000 Posted From: 71.28.18.56 Rating: N/A |
It's all right here: http://www.jakebrake.com/support/parts-and-service-literature.php?engine_mfr=3&engine_mode l=28&jacobs_product=25 Len | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 80 Registered: 7-2006 Posted From: 4.240.213.183 Rating: N/A |
That's great IF one has a DD....Mine is a Cummins.... RCB | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1846 Registered: 1-2001 Posted From: 75.108.79.35 Rating: N/A |
Dale, this is an excerpt from the Jake manual. "Once activated, the engine brake opens the exhaust valves near the end of the compression stroke, releasing the highly compressed air through the exhaust system. Little energy is returned to the piston, and as the cycle repeats, the energy of the truck’s forward motion is dissipated, causing the truck to slow down." Please note that it says the exhaust valve is opened near the end of the compression stroke. I do not recall how this is accomplished but I feel certain it is done on each and every compression stroke of each piston. Richard | ||
| Bob greenwood (Bob_greenwood)
Registered Member Username: Bob_greenwood Post Number: 734 Registered: 7-2006 Posted From: 64.136.26.228 Rating: N/A |
so...do you nuts that use your jakes in town have it hooked up to the brake lights....or do you just let them rip & let people run into the back of you..this is silly..jakes are for steep hills | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 310 Registered: 7-2005 Posted From: 69.19.14.24 Rating: N/A |
Richard, The manual that you are quoting from is a newer manual (written in 1995 I think). That is a general manual that does not directly address the principals of operation of the DD 2 stroke jakes. Trust me I have been through this with Jacobs while diagnosing several jake problems on our trucks. I would have to go count, but I think we have 7 or 8 trucks with 2 stroke DD engines with jakes on them. I have some of the worst cry baby drivers when stuff ain't perfect I'm the idiot that they tell all about it. Still can't get one of them to understand that a 2 stroke won't have the engine brake capacity of a 4 stroke especially with 50K lbs worth of logs on. LOL. Now the newer computer controlled engine brakes do indeed work that way, but each jake head has it's own solenoid and control wiring. Bob, Most engine brakes won't work below 20 mph. These monsters won't slow down instantly when an engine brake comes on, so if you rear end a bus or truck you were following too close to begin with. I'm sure your state (TX and many others)will find that the driver that hit the vehicle in front of them was at fault. It's an automatic ticket in Va. if you rearend someone. (Message edited by Happycampersrus on February 23, 2007) | ||
| Bob greenwood (Bob_greenwood)
Registered Member Username: Bob_greenwood Post Number: 735 Registered: 7-2006 Posted From: 64.136.26.228 Rating: N/A |
so...if YOU don't get a ticket..YOU have no feelings about screwing up somebodys life.... | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1847 Registered: 1-2001 Posted From: 75.108.79.35 Rating: N/A |
BOB, Several years ago I read about some people hooking up a center light to operate when the Jakes actually are slowing the vehicle down. I was going to do it but just never got around to it. And Dale is correct, they will not operate at all below 15-20 mph and even at higher speeds, the speed reduction is not so great that it should cause anyone to rear end you. Many, many people I have talked to leave the switch on all the time. Dale, Unfortunately I do not still have my Jake manual that thoroughly described the operation so I am going to have to concede that the exhaust valves stay open all the time. I still do not understand why they provide braking in this mode of operation however. LOL Richard Richard | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 311 Registered: 7-2005 Posted From: 69.19.14.44 Rating: N/A |
Bob, Didn't you ever hear of the 2 second rule. Just because someone can't drive doesn't make it my fault. Yes I would feel sorry for them, but I didn't hold a gun to their head and make them tailgate me. Always leave yourself enough distance to plan for what if. Richard, On the mechanical 2 stroke with the jake on, The piston on it's way up will compress the air some, but not enough to ignite fuel because the exhaust valve is open only slightly. This compression built up is what causes the braking effect. The DDEC II and above have better jake capabilities for cruise control and such, but my old engine is left out. Oh well, time to upgrade Honey | ||
| Bob greenwood (Bob_greenwood)
Registered Member Username: Bob_greenwood Post Number: 736 Registered: 7-2006 Posted From: 64.136.49.228 Rating: N/A |
DALE... I know you guys up north won't understand,even after I explain it,but, the reason they invented brake lights ,is so the poor guy behind you has a little warning that you are slowing down ...SOME of you are going to fix it where EVERYBODY has to have a CDL to drive a bus...before you GET the CDL, you will learn the rules..I have mine...so, ..we just will eliminate people like you that just don't care. (Message edited by bob greenwood on February 23, 2007) | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 312 Registered: 7-2005 Posted From: 69.19.14.40 Rating: N/A |
UHH Bob, I have class A CDL and I'm licensed to saftey inspect ANY vehicle in the state of VA. including Tanker trailers to carry hazardous materials. I have been licensed for years. Ask any driver trainer and they are going to tell you about correct following distances. Up north?? Do you know were Virginia is?? Guess I will have to tell all my friends and family we live up north. LOL. | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 81 Registered: 7-2006 Posted From: 4.240.144.40 Rating: N/A |
Easy guys....this is a good thread...and a great board and.... helpful without the personal asides....we all have expertise....in something. Doesn't make any one right....or wrong. FWIW RCB | ||
| Len Silva (Lsilva)
Registered Member Username: Lsilva Post Number: 89 Registered: 12-2000 Posted From: 71.28.18.56 Rating: N/A |
Posted on Friday, February 23, 2007 - 10:50 am: -------------------------------------------------------------------------------- That's great IF one has a DD....Mine is a Cummins.... RCB =========================================== Go back to the link I posted, click on "Support", they have docs for jakes on most engines. Len | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 82 Registered: 7-2006 Posted From: 4.240.213.99 Rating: N/A |
Thanx for the re-direct Len....forest and trees issue, I guess ....then again, could be maturity issue. RCB | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 99 Registered: 8-2006 Posted From: 207.231.81.154 Rating: N/A |
EEGADSO, Maybe an explanation of the overall will help? First off, when I said "if anything other than the dash switch click is heard, adjust the buffer switch." If the engine dies, the buffer switch is out of adjustment, period. Same for black smoke in Jake operation. The buffer switch is in series with the dash switch, and is SUPPOSED TO ONLY ALLOW JAKE OPERATION WITH THE FUEL RACK IN THE NO FUEL POSITION. If the governor has moved the fuel rack to the idle fuel position, OR beyond, the buffer SHOULD BE OFF. In proper/normal operation, the Jake dash switch can stay on, it will just be noisy every time you shift or take your foot off the throttle. The buffer should open the Jake circuit as soon as the governor begins to move the fuel rack away from the no fuel position. When the buffer is out of adjustment, it will cause black smoke while slowing, and the engine will die instead of idling. Jake brakes work by COMPLETELY opening the exhaust valve(s) at the TOP of the compression stroke, and venting all the compressed air in the cylinder into the exhaust manifold. They do this by using engine oil pressure controlled by solenoid valves to pull a modified exhaust valve rocker arm assembly closer to the cylinder head. The timing signal for this is a follower on the fuel injection cam, so it occurs at essentially the top of the compression stroke. Release (closure) occurs before the bottom of the power stroke. Low oil pressure will not operate Jakes properly. They are either on or off, two speed or more just have part of the control wires hooked up to seperate terminals on the dash switch, and seperate master Jake units. One master controls one slave, each has their own cam feeler for correct timing. Same thing exactly happens on two or four cycle, just half as often on a four stroke. Richard, this was/is exactly what I was referring to, a simple but precise adjustment, and you're good to go! | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1849 Registered: 1-2001 Posted From: 75.108.79.35 Rating: N/A |
Based on this, then you suggest that Dale is wrong and the exhaust valve is not held in the open position continuously. He questioned how the Jake would get a signal to open the exhaust valve on each compression stroke. Based on your explanation, there is a cam feeler that signals the Jake to open the exhaust valve on each compression stroke. I personally thought that was what happened, but I did not know where the signal came from that told the Jake to open the valve. Richard I | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 84 Registered: 7-2006 Posted From: 4.240.213.48 Rating: N/A |
George....is one to ass u me then that EVERY Jake has a "buffer switch" that can be adjusted? Seems that might be contrary to another post here on this thread. Could (would) you elaborate a bit please? From the length of this thread, there is a lot of interest in Jakes in general. That's good, right? RCB '64 Crown Supercoach (HWC) | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 100 Registered: 8-2006 Posted From: 207.231.81.154 Rating: N/A |
Evening Richard, IMNSHO, your posts are correct. Yours of 2/23 11:34 is the exact explanation of Jake operation. And you are correct that holding the exhaust valve open wouldn't accomplish anything. The operating force behind the Jake is the same as "Ford Powerstroke" fuel injection. Lube oil pressure is used to pull a modified rocker arm down closer to the head, and with one end still following the cam in the closed position, it see-saws the exhaust valve open at the right time. There is another description in one of the other posts about "take off a valve cover, rev it up, put on the Jake, and watch the exhaust rocker move." As he says, it will only do it once or twice until the engine is slowed and the buffer opens the circuit. I agree with your comment on 2 speed Jakes also, in "Low" speed, or whatever we are going to call it, only half of the masters are energized, and since the buffer is only supposed to allow operation with the rack in the no fuel position, no black smoke should occur, because no fuel should be injected. As a result of the above, I don't feel that the other post is correct... If the buffer is adjusted too far loose, it will allow the Jake to come on (or stay on down to) idle speed where the governor begins to move the fuel rack to keep the engine idling. The engine will throw out black smoke and die. If the buffer is turned in too far, it may prevent the rack from moving completely into the no fuel position, which would cause black smoke during braking, really too far would prevent the engine from stopping. R. C. Just like the first part of an assumption, everybody's got one. It is possible to run Jake's without one, but you would have to work the switch every time you slowed down or clutched, or the engine would die. We have to remember that our foot is not directly connected to the fuel rack, the governor is inbetween, and controls fuel rate according to engine speed and throttle position. Any time the driveline is turning the engine faster than the throttle position, the governor moves the rack to the no fuel position. When the buffer feels this, (its just a fancy name for a microswitch) it connects the Jakes to the dash switch. If the dash switch is on, you get braking, until the governor moves the rack. This SHOULD occur just above idle speed. All of the mechanically injected engines do it the same way, only with different looking parts. The electronic engines do it with a signal from the computer, which is only present when it is telling the injectors not to. HTH George | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 313 Registered: 7-2005 Posted From: 69.19.14.26 Rating: |
"One master controls one slave, each has their own cam feeler for correct timing. Same thing exactly happens on two or four cycle, just half as often on a four stroke." Not exactly true, but close. Back in the 60's when these engine brakes were designed the first series did NOT have the master piston (4 fingered fork or cam feeler). There wasn't any timing device. They operated just as I said earlier and EVERYONE complained that they didn't have great engine braking. I will try to borrow a digital camera and take pic of a jake head without the master piston before everyone says they didn't exist. "And you are correct that holding the exhaust valve open wouldn't accomplish anything." For the record they are still playing with this system. http://www.jakebrake.com/technology/bleeder.php In the early 70's (this is per Jacobs) they developed the jake heads you see today. NOW this is were I have to swallow my shoe. I was under the impression that these were developed for the 92 series engines, but no. They were developed to replace the 1st series that weren't that great. I will go lick my wounds over that one. "One master controls one slave" That is ONLY true on 8V engines. That is not true for ANY 6cyl engine inline or 6V. On the 6v the center jake head is the master with a slave on each side. On the inlne 6 #2cyl and #5 are to be the master jake heads. Dale 35+ yrs as a heavy equipment mechanic and still learning. (Message edited by Happycampersrus on February 25, 2007) | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1851 Registered: 1-2001 Posted From: 75.108.79.35 Rating: N/A |
Dale, ain't it nice that we still can learn after this many years. I know this has been a learning experience for me and I thought I knew all there was to know. LOL Thanks everyone for a very interesting thread, for all the knowledge shared and for keeping it clean and without any flames. Richard | ||
| Dale Waller (Happycampersrus)
Registered Member Username: Happycampersrus Post Number: 314 Registered: 7-2005 Posted From: 66.82.9.87 Rating: N/A |
I have never thought name calling and flaming was a very good way to learn anything. Actually I hope that the way I post never seems to harsh. I (like many others) want to make my points, but I so hope I don't offend anyone. I would hate to need help or advise only to be left out in the cold. This board and the Mak board has some of the sharpest folks I have ever talked to. I have alot of time working on Heavy Equipment and the older I get the less I know. Technology seems like it has blown by me. I still learn stuff everyday, problem is remembering it. My buddy has a great saying "The man who dies with the most friends wins" | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 85 Registered: 7-2006 Posted From: 4.240.213.122 Rating: N/A |
With all the information expounded, I intend to "chase" the black smoke that shows on occasion when I use mine. I have noticed that, for the most part this seems to take place at a higher speed. Once again...thanx to all for the extra effort on this question....and I agree with Richard's comments. Great board!! | ||
| larry currier (Larryc)
Registered Member Username: Larryc Post Number: 37 Registered: 2-2007 Posted From: 207.200.116.13 Rating: N/A |
I wonder if a DD jake works anything like a Cummins Jake? The mechanical motors (855) all need to have the exhaust push tubes changed out if you add Jakes. The Jake push tubes have a tulip around them. A good jake will always roll out the black smoke. Its like going up the hill, no smoke, no fire. With a manual trans, a Jake will have 2 switches. One will be mounted on the clutch linkage so if its engaged the Jake is off. One is mounted to the throttle linkage to turn the Jake off if your foot is on the throttle. If both circuits are closed the Jake works! If the Jake works good, its gonna smoke. In a lifetime career in trucking I have never seen or heard of a brake lite hooked to a jake. Thats funny! Damn things barely stop anyway! | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1856 Registered: 1-2001 Posted From: 75.108.72.204 Rating: N/A |
Larry, perhaps you would be so kind as to explain how there would be any smoke if the fuel is shut off. I know that I never saw any smoke from my exhaust when the Jakes were operating. I think Bob might want brake lights to come on any time you downshift, coming down a grade, so the tailgater knows you are slowing down. LOL Richard |
