Jake Brake and effectiveness

belfert · December 31, 2009, 09:25:20 AM

I posted a long time ago that I didn't think my Jake Brake worked all that well. The DDEC and WTEC together will downshift the B500 by one gear automatically any time the Jake Brake is engaged. On my most recent trip I downshifted into 2nd or 3rd manually and man does the Jake Brake really work then! I've never had any training on using the Jake Brake or I probably would have learned this long ago.

The road was quite slippery on my last trip and I ended up using the Jake Brake in combination with downshifting to keep the bus under control. The bus would start sliding if the service brakes were used, but not with the Jakes. I know they don't recommend use of engine brakes when slippery, but they seemed to work better than the regular brakes.

I like the Jake even better now that I know how to make it work better. If it isn't keeping me slowed down enough I just downshift a gear.

DSweet · December 31, 2009, 04:37:47 PM

We have had excellent results with our Jakes on our 4104 [w/6-71]. Hwy 58 through the Tehachipi Mtns. here in California is a series of curving 5% grades. Without the Jakes it was second and third gear and lots of brake action [they were getting hot on the last grade], the Jakes keep us at 45 mph in 4th and 35 in 3rd. Not bad for a 52 year old GMC. To say the least, we are more than happy their performance.

rv_safetyman · December 31, 2009, 05:49:58 PM

Hi Brian. With my 10 speed, I just keep grabbing gears until I get the slowing effort I need. Really easy with the AutoShift and it will not let you go into a gear that will hurt the engine.

In another thread you talked about letting the transmission "do its thing". This is just one example why you should be "in control" of that device when the conditions are demanding. I am told that some world transmissions have two control scenarios. Even there, a good driver knows when to "take over" and optimize the operation.

When I do my SilverLeaf seminar, I talk about using the engine information to help you make decisions on "getting up that big hill better". There, you can watch engine temperature, air inlet temperature and turbo boost to help you make sure you are making your engine happy - by using the proper transmission gearing. The turbo boost is your best indicator of how much you are asking of your engine. Watching temperatures (transmission if you have a gauge), can guide you as to which gear to be in, or when to back off the throttle and "smell the roses". I suggest watching the TREND of the gauges. This will give you an early indication of when to shift. If all the temperatures are holding well, then you are probably in the proper gear. If any of the temperatures are trending upward, you know what to watch and can make the proper gear selection ahead of when a problem can occur.

Sorry, that is a bit off the subject, but somewhat related.

Lots of folks really discourage using Jakes when it is slick. My take is that I put mine in the low or medium setting (two or four cylinders in my case) and really pay attention to what the bus it telling me. I also try to keep my hand close to the switches to shut them off quickly.

You bring up an interesting point. That is that Jakes are not very effective when the engine RPM is low. We had an RV exit off of our infamous I 70 right at the bottom and did not have the brakes to stop him completely at the bottom. Fortunately there was no traffic. When he got to the nearby campground he was talking with my customer about how his Jakes did not work. Turns out he simply left the transmission control set for normal highway (did not shift down) and you DO NOT DO THAT on I 70 heading into Denver.

Jim

luvrbus · December 31, 2009, 06:08:37 PM

If you have Jakes on a 2 stroke with a gear in the 3:33 to 3:76 range and in fourth or fifth gear with a Allision the Jakes are about useless as tits on a boar hog you better down shift and not wait for the tranny to do the work for you.
Check out the braking power on a 2 stroke then compare it to a 60s or any other 4 stroke

good luck

gumpy · December 31, 2009, 10:42:04 PM

It seems to me that if you are using your Jakes because your tires keep sliding when you use the brakes you are probably not driving appropriately for conditions.

How would you stop the bus if you had to make an emergency stop?

belfert · January 01, 2010, 05:55:21 AM

Quote from: gumpy on December 31, 2009, 10:42:04 PM
It seems to me that if you are using your Jakes because your tires keep sliding when you use the brakes you are probably not driving appropriately for conditions.

How would you stop the bus if you had to make an emergency stop?

I was going all of 20 or 25 MPH and I did pull off the road for a while to let things improve. Exits are far between whe you are going so slow.

kwood · January 01, 2010, 06:35:47 AM

I have and mc9 with 8v71 and jakes with an automatic transmission. I don't have very much experience with them but have noticed at low rpm (like slow speed driving) they don't work all that much but on the freeway with the bus in higher rpms they work very well. Problem is with an automatic is is sometimes hard to keep it in higher rpm.

luvrbus · January 01, 2010, 06:45:38 AM

Kwood, the 2 strokes don't have enough oil pressure at low rpms to make the Jake hold ,you need to down shift to keep the oil pressure up that is why I love my Stone/Bennett shifter just a filp of the switch

good luck

rv_safetyman · January 01, 2010, 08:22:59 AM

Kwood and others, we need to separate out driving conditions. On the flatter, open roads, there is no need to try to keep the RPM up for the Jakes. The exception being that even there you want to make sure the engine RPM is not in the "lugging" range. Unless your transmission control system is screwed up, that will probably not happen.

Where we need to take control of the transmission is when we really need the Jakes. That would be on long downhill runs and on tight, twisty roads. There it just make sense to take over control and keep the engine in the higher RPM ranges (say above 1700-1800 RPM). On the real "hills" you want to keep the RPM even higher. We are over 44K and I keep the Series 60 at 1800-2100 when the hills are steep. When the engine frequently wants to go over 2100 in a given gear, you know that you need to slow down and drop one more gear.

You really should not be touching the brakes very often in those conditions, so that you have them available if you really need them. It really does not take long to get the brakes hot and when you do, you are probably in trouble.

Jim

luvrbus · January 01, 2010, 08:38:00 AM

Jim, that is not true in all case some of these older buses need all the help you can get to whoa it up even here in AZ and TX on flat ground.
A lot of folks with the early 01 and 05 Eagles with crappy brakes from Eagle use the Jake's for assist in stopping on level ground.
I for one before upgrading my brakes would have bought several cars without my Jake's in Houston or Phoenix

good luck

rv_safetyman · January 01, 2010, 08:55:37 AM

Clifford, good point.

Kind of a sad testimony about brake design in those coaches.

At typical highway speed, the Jakes should be effective when you first let off. However, you are then reliant on the transmission shifting down aggressively (to keep the RPM up). Under critical conditions, you would probably not be able to control the transmission and handle the other panic functions.

I will be the first to make the observation that, if you have a bus with marginal brakes, you need to really be careful to keep the bus in a safe operating condition. By that I mean good mechanical condition (emphasis on brake adjustment), and keeping the bus in a safe operating range from a driving condition (speed and spacing). Then, I will be the first to say that I have not been as careful of a driver as I should be. Also idiot drivers do not always allow you to be a safe driver

.

I suspect there will be folks who say that Jakes were never intended to augment the brakes under the conditions you describe. Even with the fairly good Jakes on a Series 60, I don't count on them helping except on the downhill and twisty road conditions.

Not debating, just adding my thoughts (I sure don't want to pi$$ anyone off on the first day of the new decade

>

Jim

belfert · January 01, 2010, 09:08:01 AM

I recall one downgrade when I had the Jake brake on. The guys in the back started yelling about using the brakes too much as they could smell burning brakes. I yelled back that it wasn't us as I hadn't touched the brakes in several minutes. It was some other vehicle next to us that was burning up their brakes.

I will admit it wasn't legal to use to use engine brakes on that grade, but I wasn't about to not use a safety device where it is most needed. I wanted my service brakes nice and cool if I needed them.

Lin · January 01, 2010, 09:19:55 AM

Belfert,

That brings up an interesting point. One often sees local signs prohibiting engine brakes, but I was once told that a locality cannot ban the use of safety equipment in some states. Does anyone know the truth about this?

Ed Hackenbruch · January 01, 2010, 09:27:34 AM

Lin, if you look at the signs closely some say all jakes prohibited and others say only non muffled jakes prohibited.

belfert · January 01, 2010, 09:52:15 AM

Jacobs Vehicle Systems has been very agressive about government entities not posting signs banning Jake Brakes. Jake Brake is a registered trademark plus JVS believes it devalues their product. JVS suggests the posting of signs that prohibit unmuffled engine brakes instead.

I have lots of signs prohibiting engine brakes, but I don't recall seeing one that only prohibited unmuffled engine brakes. It seems that unmuffled engine brakes are the real reason for most of the complaints.