I have a 3406a, and the jake alone is not enough for the hauling I'm doing. Can I add an exhaust brake to supplement the Jake? It seams to me that Mercedes was doing something like this.
I think it's entirely possible, but i remember reading a Blue ox exhaust brake brochure stating some engines require stiffer exhaust valve springs to do the combo braking. You may want to check into that.
With a Cat engine you can also add a retarder. That is the best way to go. I am not positive, but I think they came on the "A" model 3406. My "E" model has one, and with jakes and the retarder it can comfortably come down hills as fast as it climbs them, and it climbs really good.
Yes, the Cat Brakesaver/retarder was available on the A model. But adding one to an existing setup would be extremely expensive. It would move the trans back 5-6" for a start, then the monstrous oil cooler and plumbing, the oil pan and valve would have to be added. and that's all assuming the radiator has enough capacity to dissipate the heat. Brakesavers were pretty much something that needed to be specced into a new truck.
Agree! Yes you can add an exhaust brake, I know of three B models that had them. But they didn't add much to the braking. You may not get the results your after. Truck Shop
Another vote for a retarder. In fact if you fit a really good one you can probably do away with the Jake Brake all together.........
I've used exhaust brakes a lot and I am not thrilled with them but they were better than nothing. However an exhaust brake plus a Jake is not something I have ever seen. I have my doubts about how well it would work in that config. I will save the details unless you really want them. Engines of that era just did not have very good Jakes. They were kind of an afterthought. Cat especially because they had no injector rocker. I have heard tales about the brakesaver being a leaky old thing and never really staying sealed. Cummins might have had the best Jakes. It is probably impractical but I will ask if you can switch engines. There are also electric and hydraulic drive shaft mounted brakes that work really well. But any of these 3 (brakesaver, electric, hydraulic) are very heavy and you are probably trying to save weight. Another idea if you have been wanting an automatic is that Allison transmissions come with an optional hydraulic retarder but again, probably heavy.
I am not an engineer, but if you consider that the jake essentially uses the compression stroke of the engine to provide braking, and then opens the exhaust valves around TDC to release that compression so it doesn't push the stored energy back to the piston, if you add a whole bunch of backpressure on the exhaust it will probably make the jake less efficient. Seems to me it would be a case of diminishing returns. Couple things to consider: First what iteration of the Jake brake do you have on that engine? There were four or five for the 3406 mechanical, early ones were I believe a lot lower performance. Secondly have you had it checked over, kitted and adjusted? The CAT jakes are essentially hydraulically activated so leaks and being out of adjustment from normal wear can make a huge difference in braking performance. Also the general engine condition: low compression and valve lash adjustment can affect braking performance also. I drove a truck with 3406B mechanical (425hp) and a 13 speed back in the early 90's, same jake as on yours but the newest version for that engine. At just over 100K gross it handled long downgrades without the slightest issue as long as you were in the right gear. Usually around 22-23 mph, with just a touch of air brake before a corner or on a long straight steep pitch.
you can also do a 300-500HP retarder on a manual transmission.
I wish the truck cane with a 400 cummins...what a jake!
Ive got a brakesaver on a 3406b,it does work well when its not leaking your engine oil.When I bought the truck I told be careful with it as you can cook the seals out of them.First 2 hours of driving in some steep country I was down over a gallon of oil,so I guess the seals were cooked when I got the truck.I think its a 4 or 5 thousand$ job to remove and reseal it by the time you throw in a new clutch while your in there.Thats a hard pill to swallow on an 86 Kenworth with some wiring issues and needs a set of skins.In saying that the braksaver is great and would be better with a jake to,but as said above it probably has to come new with the truck
I have two trucks, both with 3406B's and retarders, one with jakes as well. The jakes on the b models ( or a models too) were never that strong, but turn them off going down a hill and one quickly realizes that you don't want to be without them. I really like having both retarder and jakes as Jerry mentioned. Drawbacks to the retarder are: 1) Might be hard to find nowadays 2) Have to add larger oil cooler and associated plumbing, and shorten driveline by 4" 3) Have to monitor oil temperature, and get in the habit of manually turning on the fan. This adds additional retarding though - not much, but every little bit helps 4) Added weight The retarder air pressure can be adjusted up - mine will go to around 65psi. without changing the pressure regulator. Too much pressure though and one will have to change diaphragms frequently I suppose. The higher the pressure, the more effective the retarding. As mentioned above, the addition of a PAC brake or Blue Ox would probably result in diminishing returns as the effectiveness of the Jake would be reduced. Also as previously mentioned, there are several versions of Jakes - 346 (a,b,c,d?), and 349. I think the 349s worked the best, but may be more temperamental to keep adjusted. Another option is to add an electromagnetic drive line retarder, like these: http://www.telmausa.com/ I drove a truck that was fitted with one, and it worked very well, but you had to watch using it before coming to a stop as it needed a spinning driveline to cool. They are quiet as well, but must be installed correctly regarding driveline angles.
My experience with Telma was on ambulances and I guarantee you nobody ever cared about cooling before stopping and those things had zero problems other than the occasional relay failure. In fact they were actuated off the brake pedal in 4 stages. The place we got parts from was a bus sales company if that tells you anything. They are basically a huge slotted cast iron brake rotor in the drive shaft with electromagnets instead of brake pads.
I wonder why the big power cats are rated at like 600 retarding hp, and these old 3406s are considerably less? The displacement/braking hp ratios do not coincide.
If the retarder is mounted on or in the transmission then the "retarding HP" can be higher than the engine HP because the retarder's capability to absorb power bears no relation to how much power the engine can produce. As an example we had a fleet of Scanias on my last job with 420HP engines but they were fitted with transmission retarders capable of absorbing 600HP, a very useful thing to have when loaded up to max permissible GVW on a 10% downgrade. The retarder could pretty much stop the truck all on its own without even resorting to the brake pedal. Wearing a seat belt was essential otherwise you'd be wiping your nose off the inside of the windshield.
I'm speaking of engine retarding hp only. They are up to 725 with addition of driveline retarders.
In the absence of more specific knowledge, I'd say it is because back in those days we were just happy to have any Jakes at all and they were kind of an afterthought. Men were still hauling loads around with 6-71s and even big gas engines back then. Somebody recently posted that he likes to descend hills using no service brakes at all, and while I am not going to argue with him, that it is a good idea, in the old days that was just not an option unless you wanted to go down in 1st gear. You had to use service brakes and lots of them, you just had to plan ahead and not let them get too hot but they always got hot to some degree. That plus keeping engine RPM up, way up like at the governor speed all the time when using the Jakes. You had to watch that it did not run away from you because engine kablooie was close by.
I think some of that is related to camshaft profiles and the fact that the C15 and C16 use rocker operated injectors that time the Jake operation more accurately than the old 3406 jakes could. I know the Cummins ISX could use the variable geometry turbo to build 40 psi of boost with the jake on to help increase cylinder pressure, and most kicked the fan on to help suck up HP too.
The ISX is unique in that it has a special braking cam profile and they used that as a selling point. https://www.youtube.com/watch?v=JF6ZeybmQ1U I hate the fan function and had it disabled most of the time. Too loud for too little effect. There is a fan switch on the dash if I want it.
The log trucks in my part of the world all used to have water tanks behind the cab, when you left the landing and started down, you opened the valve and let the water run on the brake drums.... also used to see stacks of fractured brake drums, but it helped in those days.
My new truck has an ISX, and I am still learning it. The fan does not come on automatically, but I use it manually, and it is like another half of a setting on the Jakes. Not a lot of help, but some, and like you said, it does add to the noise level. I do agree that the ISX Jakes work better than the Cat, though my Cat has not had an adjustment in years, and I am sure that would help. My KW with a 3406E had the fan switch on automatically with the Jakes. Also, as stated above all of these things work best at holding you back with the engine near the governor.
My Dad was a mechanic in those days and said that cracked drums were usually a result of turning on the water after they were already hot. If they got water first and stayed wet then they did not bust.
I think I read that a 32" 9 blade fan could suck up 20HP+ at governed speed. I do know when the fan comes on in my junky old 86 Volvo with a 3406B, its very noticeable as far as power loss. It also has the 346 jakes that haven't been reset forever, but they seem to do the job. But this truck is lucky to run twice a month for a couple hrs. here and there.
The DD15 series has the best jake of any that I have driven,IMO. They accomplished it by actuating the exhaust valve twice to totally expend the energy created on the compression stroke. So the piston is pulling against a dead cylinder expending total energy to pull the piston down. Truck Shop
This thread has me remembering that Cat had a model of Jake for A's and B's called quote ** the Super Jake** unquote. The model is a 349A, the standard model was the 346B. The 349 was 25 to 30% stronger. To verify that I called a friend of mine that is an ex Cat Mechanic that now teaches diesel at the Walla Walla St. Penitentiary. Know as Mr. Penner, that is his real last name. If the OP could find a set of the 349A's it would take care of the jake issue. We had a owner operator that had a set on a 7FB 400 that were real strong for a Cat. Hope this helps. Truck Shop
Jake also had an upgrade kit for the 349 series called a "B+" kit to increase braking in the 3406B models. If you want the best performance and life, you would want the latest 349D setup I should think. YMMV.
Thanks for adding that, I forgot to. Too many irons in the fire for Sunday. Truck Shop
Good info, thank you! I'm kinda wonder if I'm pissing in the wind though. I'm grossing 95k, right now there is a grade that I have to go down that requires 1st gear, and I still have to use the brakes. I might be asking too much out of this Ole girl? How do I verify which jake I have now?
I guess I would say it depends... axle ratio, transmission model, tire size, steepness and length of grade. As long as your brakes are not smoking hot at the bottom I would think you're golden. Pop a valve cover off, I think the model number is cast into the jake units? If not there should be a tag. Talked to a heavy haul driver back in the day, had 500+ hp CAT, 15 speed with deep reduction, four speed brownie and two speed drivers... hauling precast concrete bridge beams onto Mt. St. Helens to rebuild the road after she blew with a second driver in the race car under the load at the back. On the last pitch he said he was all in, everything in the last low gear, never spun a wheel just flat ran out of power. They brought a D9 down to help him the last couple hundred yards. Sometimes no matter what you got, it just ain't enough.
I just can't wrap my brain around this. How steep and how slow are we talking about? 1st gear must be good for 1 mph?
I was in my Sterling when you posted, it runs about 9 miles per hour in first gear governed speed. I would say the Peterbilt is running at least five probably 7 miles per hour
I called a exhaust brake company...an exhaust brake will not work in conjunct with a jake.
Sorry if I am sidetracking but what % grade is this you are talking about? What is your gear ratio and transmission model?
Grade is 18% at worst. 13spd. Not sure ratio, 4.5???
It seems to me like you may have kind of a tall transmission and/or rear axle for this kind of thing. According to the only horsepower calculator I could find, it returns 377 HP at 95,000 lbs on an 18 percent grade at 7 mph. That is for going uphill so downhill will be a little less because gear losses work for you instead of against you. If that calculator is worth anything. I don't think the old 3406 Jakes ever got 377 HP even when they were brand new. I can't find a chart of it but the 3406c only got to about 320 @ 2000 RPM.
Problem solved, fresh 6NZs
A cluster of Kittens?
I wish one of those "kittens" would stray and end up in my yard, instead of all the others that do.