Skip to main content ↑ ↓
Topic: Compression Brake Performance (Read 952 times) previous topic - next topic
0 Members and 1 Guest are viewing this topic.

Compression Brake Performance

Yahoo Message Number: 16301
Our '05 Intrigue has the CAT C13 engine with Allison 4000MH transmission and 3 stage compression brake. I'm wondering what kind of performance I can expect from the compression brake. I am assuming I need to keep the engine RPM under 2100 (2300 absolute max). At this RPM in stage 3 I still need to apply the brakes quite a bit on a 6% grade. The coach weighs around 43000-44000 (guessing, we still have to weigh it) and we are towing a 4500lb Jeep Grand Cherokee. With my 2001 Dodge pickup and a 23000 lb load, my exhaust brake would hold the whole setup at 60mph in 5th gear. Are my expectations too high?

Bob

'05 Intrigue LE #11872

Re: Compression Brake Performance

Reply #1 –
Yahoo Message Number: 16302
Re: [Country-Coach-Owners] Compression Brake Performance At 4:19 AM +0000 4/21/05, Bob Stephens wrote:

Re: Compression Brake Performance

Reply #2 –
Yahoo Message Number: 16303
So, is it safe to assume that the transmission ECM will upshift the tranny if the RPM's get too high? I know it won't downshift until the RPM's drop to a safe level but does it also automatically upshift if the RPM's get too high? How fast are you traveling coming down the Eisenhower? Third gear seems too slow and fourth gear seems too fast.
Bob

'05 Intrigue LE #11872

Quote from: Dick Bradley\[br\
]
At 4:19 AM +0000 4/21/05, Bob Stephens wrote: > >Our '05 Intrigue has the CAT C13 engine with Allison 4000MH > >transmission and 3 stage compression brake. I'm wondering what

kind

Quote
of performance I can expect from the compression brake. I am

assuming

Quote
I need to keep the engine RPM under 2100 (2300 absolute max). At

this

Quote
RPM in stage 3 I still need to apply the brakes quite a bit on a

6%

Quote
grade. The coach weighs around 43000-44000 (guessing, we still

have

Quote
>

Re: Compression Brake Performance

Reply #3 –
Yahoo Message Number: 16304
Hi Bob,

First, I think that you meant 2300 lb load on your Dodge although I suppose that a 12 ton pickup is theoretically possible but not straight of the line. Just joking.
I have a Cummins ISL with a two stage Jake but assume that Cat works the same. The Allison will upshift to prevent the engine from exceeding its safe rpm limit. I believe that with the Cummins it is 2460 but it was a long time ago that I talked to Cummins. The really scary thing is that it will actually shift into neutral if the rpm limit is exceeded and you are in 6th gear. Cummins said that if you do the math the coach will be doing better than 96 mph at that point and you have a lot of other problems happening by then. Having the coach upshift on a steep grade is a disconcerting experience at best but I can't imagine letting it go into neutral. There ia a point where it would be better to save the passengers than the engine.

If you are not already aware of how a Jake works, it is a hydrolic device built into the engine (no retro-fit) that keeps the exhaust valve closed until just short of top dead center. This turns the engine into a big compressor compressing against itself. It is considerably more effective that a exhaust brake. The loud popping that you hear with large trucks is the escaping exhaust at the top of the stroke coupled often with a set of straight through pipes. Jake actually is a brand name that became identified with the device similiar to 'Skil Saw'.

If 3rd gear is too much and 4th is too little then changing to a lower stage should help. Staging is done by changing the number of cylinders that get to have the valve held shut.

Having a 3 stage Jake is is the best of all worlds. It takes some playing around with the right combination of gears, speed, and stages but it will do the job and with almost no application of the service brake other than to pull the rpm down forcing a downshift. One thing to remeber is that the higher the rpm the more braking so don't get too conservative about rpm.

Don & Mary Seager

40ft 2004 Allure 31046

-

Re: Compression Brake Performance

Reply #4 –
Yahoo Message Number: 16305
[Country-Coach-Owners] Re: Compression Brake Performance The trans will upshift if too many RPM's. We can leave the tunnel at 35 mph and keep it on the 55 mph speed limit all the way to the bottom, or we can slow it to 30 mph if desired. I ran this grade for 3 years in my Beaver with only the 2 speed brake and had to use the service brakes numerous times. The key is to anticipate the increasing speed in time to toggle down before the rpms get too high.

Dick

04 Intrigue

Re: Compression Brake Performance

Reply #5 –
Yahoo Message Number: 16306
Thanks, Dick, for the info, I'll just let her run on the next hill.
Given that I can exceed the 2100 RPM I'll use 3rd gear on some of the hills and hopefully it will hold to 50-55 MPH. My Dodge had a stick shift so you had to watch the RPM's yourself or listen to valves hitting pistons. I had read somewhere that the engine braking RPM for the CAT was higher than the governed speed but I couldn't find it anywhere. We are really loving the coach and it was your comments to me that helped us make the decision to go CC over Beaver. Since we purchased the coach we've met 2 new Beaver owners and they have had significantly more warranty issues than we have.
Donald, I did mean 23000lbs on the Dodge. That was the weight of the truck and trailer. I was 1500lbs overweight by Dodge standards and the reason I switched to a Ford 550 before trading for the CC. Also, thanks for the info on exhaust vs engine brake but I did know the difference. I just wasn't sure how high I could run the engine and this motor is too expensive to abuse.

Bob

'05 Intrigue LE #11872

Re: Compression Brake Performance

Reply #6 –
Yahoo Message Number: 16312
If you have to use the brakes quite a bit, you are going to fast. Slow down to where the transmission will downshift to a lower gear, and you will have more braking power from the Jake brake. Leaving Death Valley this January, I actually had to slow down to where I used first gear Jake brake to preclude using the brakes too much. You are pushing a lot of weight (gravity is pulling it!), so a lower gear will give you added torque to counteract the force of gravity.

Per

Affinity 5259

--- Dick Bradley richardLbradley@...> wrote:

Re: Compression Brake Performance

Reply #7 –
Yahoo Message Number: 16314
Bob,

Sorry, I just never got used to thinking of a trailer as 'load' but of course it is. It is interesting that you could hold speed with that weight without using the trailer brakes. I had a Dodge with a
5.9 liter and straight stick. I pulled a John Deere 870 on a 16ft
flat bed and I can't imagine not having to use the trailor brakes in that situation. The truck didn't have an exhaust brake so I had no idea that it would be that effective.

Don & Mary Seager

40ft 2004 Allure 31046

Quote from: Bob Stephens
>

Thanks, Dick, for the info, I'll just let her run on the next

hill.

Quote
Given that I can exceed the 2100 RPM I'll use 3rd gear on some of

the

Quote
hills and hopefully it will hold to 50-55 MPH. My Dodge had a

stick

Quote
shift so you had to watch the RPM's yourself or listen to valves > hitting pistons. I had read somewhere that the engine braking RPM

for

Quote
the CAT was higher than the governed speed but I couldn't find it > anywhere. We are really loving the coach and it was your comments

to

Quote
me that helped us make the decision to go CC over Beaver. Since

we

Quote
purchased the coach we've met 2 new Beaver owners and they have

had

Quote
significantly more warranty issues than we have.

Donald, I did mean 23000lbs on the Dodge. That was the weight of

the

Quote
truck and trailer. I was 1500lbs overweight by Dodge standards

and

Quote
the reason I switched to a Ford 550 before trading for the CC.

Also,

Quote
thanks for the info on exhaust vs engine brake but I did know the > difference. I just wasn't sure how high I could run the engine

and

Re: Compression Brake Performance

Reply #8 –
Yahoo Message Number: 16316
On a couple of grades I slowed to 35mph and downshifted to 3rd. It didn't take long for the RPMS to climb to 2300 so I got on the service brakes to keep the RPM's down. If I don't have to worry about overspeed, I'll try 3rd gear and let it run out a little further to see what happens.
Bob

'05 Intrigue LE #11872

Quote from: Per Korslund\[br\
]
If you have to use the brakes quite a bit, you are > going to fast. Slow down to where the transmission > will downshift to a lower gear, and you will have more > braking power from the Jake brake. Leaving Death > Valley this January, I actually had to slow down to > where I used first gear Jake brake to preclude using > the brakes too much. You are pushing a lot of weight > (gravity is pulling it!), so a lower gear will give > you added torque to counteract the force of gravity.

Per

Affinity 5259

--- Dick Bradley
wrote:

> At 4:19 AM +0000 4/21/05, Bob Stephens wrote: > > >Our '05 Intrigue has the CAT C13 engine with > > Allison 4000MH

> >transmission and 3 stage compression brake. I'm > > wondering what kind

> >of performance I can expect from the compression > > brake. I am assuming

> >I need to keep the engine RPM under 2100 (2300 > > absolute max). At this

> >RPM in stage 3 I still need to apply the brakes > > quite a bit on a 6%

> >grade. The coach weighs around 43000-44000 > > (guessing, we still have
>

Re: Compression Brake Performance

Reply #9 –
Yahoo Message Number: 16317
If you will use 4th gear with engine brake you'll have no problem. TWI 2004 Intrigue 42' Ovation

Re: Compression Brake Performance

Reply #10 –
Yahoo Message Number: 16318
Bob,

You may have checked all of this but I'll mention some things anyway.

Do you get a positive difference in speed and rpms when you shift between the 3 different stages of the Jake? it is remotely possible that something is not working.

Are you watching the rpm with the analog on the dash or the SilverLeaf? Analog guages are notorious for being inaccurate. The SilverLeaf should be right on.

Have you checked with Cat to see exactly what is the upper RPM limit to be looking for. I did with Cummins and really didn't get a positive response but that might be a factor of who I was talking to.

I don't manually downshift because I find the manual upshift later to be somewhat jerky. It seems like unecessary wear on the tranny so I let it do its own thing. In mine it will not downshift no matter manual or automatically until the RPM drops below about 1800. For that reason I am not really aware of what gear it is in but on a 6% grade I often have to drop the Jake down a stage to keep the speed from dropping too low.

Just a couple of thoughts.

Don & Mary Seager
2004 Allure 31046

Quote from: Bob Stephens
>

On a couple of grades I slowed to 35mph and downshifted to 3rd.

It

Quote
didn't take long for the RPMS to climb to 2300 so I got on the > service brakes to keep the RPM's down. If I don't have to worry > about overspeed, I'll try 3rd gear and let it run out a little > further to see what happens.

Bob

'05 Intrigue LE #11872

[quote author=Per Korslund

> If you have to use the brakes quite a bit, you are > > going to fast. Slow down to where the transmission > > will downshift to a lower gear, and you will have more > > braking power from the Jake brake. Leaving Death > > Valley this January, I actually had to slow down to > > where I used first gear Jake brake to preclude using > > the brakes too much. You are pushing a lot of weight > > (gravity is pulling it!), so a lower gear will give > > you added torque to counteract the force of gravity.
>
> Per

> Affinity 5259
>

> --- Dick Bradley
> wrote:
>

> > At 4:19 AM +0000 4/21/05, Bob Stephens wrote: > > > >Our '05 Intrigue has the CAT C13 engine with > > > Allison 4000MH

> > >transmission and 3 stage compression brake. I'm > > > wondering what kind

> > >of performance I can expect from the compression > > > brake. I am assuming

> > >I need to keep the engine RPM under 2100 (2300 > > > absolute max). At this

> > >RPM in stage 3 I still need to apply the brakes > > > quite a bit on a 6%

> > >grade. The coach weighs around 43000-44000 > > > (guessing, we still have
> >

Re: Compression Brake Performance

Reply #11 –
Yahoo Message Number: 16355
I tested 2nd and 4th gear settings. In Denver the best gear for a 2005 Inspire Genoa 40 is 3rd. I had Allison set the computer for 3rd gear and I get optimum braking when riding on I-70.

Quote from: Bob Stephens
>

So, is it safe to assume that the transmission ECM will upshift

the

Quote
tranny if the RPM's get too high? I know it won't downshift until > the RPM's drop to a safe level but does it also automatically > upshift if the RPM's get too high? How fast are you traveling > coming down the Eisenhower? Third gear seems too slow and fourth > gear seems too fast.

Bob

'05 Intrigue LE #11872

[quote author=Dick Bradley

> At 4:19 AM +0000 4/21/05, Bob Stephens wrote: > > >Our '05 Intrigue has the CAT C13 engine with Allison 4000MH > > >transmission and 3 stage compression brake. I'm wondering what > kind

> >of performance I can expect from the compression brake. I am > assuming

> >I need to keep the engine RPM under 2100 (2300 absolute max).

At

Quote
this

> >RPM in stage 3 I still need to apply the brakes quite a bit on

a

Quote
6%

> >grade. The coach weighs around 43000-44000 (guessing, we still > have
>