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Engine braking?


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#11 huskyrunnr

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Posted 22 June 2021 - 02:05 AM

Awesome. Thanks everyone. Never thought about the overdrive button in addition to 1st or 2nd.


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#12 Machinebuilder

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Posted 22 June 2021 - 10:25 AM

You didn't state what engine you have.

 

Gas engines have engine braking, I don't know of any reason you would not use it.....IF YOU MAKE SURE NOT TO OVER REV THE ENGINE.

 

Diesel Engines have minimal engine braking, unless you have an exhaust brake (Jake Brake), again do not over rev the engine.

 

Newer trucks have all sorts of interesting programing that use a combination of engine management and brake management to control speed going downhill.


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#13 Mighty Dodge Ram

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Posted 22 June 2021 - 02:09 PM

Gasser here. Coming down from the cabin, loaded or not, I always drop a gear and cruise down the “hill”. Tow/haul if loaded, but typically I’m empty heading down. Interestingly, when driving up I can always smell hot brakes from those heading down and riding their binders. If I had a modern diesel you can bet I’d be using the OEM “jake brake”. 


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#14 huskyrunnr

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Posted 22 June 2021 - 02:34 PM

Sorry ‘bout that. It’s a 6.8L V10. Downshifting was always what I had learned coming up. I guess I got distracted trying to keep up with my buddy ahead of me in a smaller vehicle. Live and learn, and forget.

 

And Foy, I may very well have taken click and clack out of context. I didn’t remember it was about everyday city driving.


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#15 camelracer

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Posted 22 June 2021 - 06:36 PM

Having a diesel w/exhaust brake and manual trans I engine brake all the time. 

 

When driving my Jeep on loose steep trails I find engine braking much more stable than having a wheel lock up with normal braking.

 

In all cases both systems must be used in conjunction wisely.


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#16 Wandering Sagebrush

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Posted 22 June 2021 - 07:12 PM

You didn't state what engine you have.

 

Gas engines have engine braking, I don't know of any reason you would not use it.....IF YOU MAKE SURE NOT TO OVER REV THE ENGINE.

 

Diesel Engines have minimal engine braking, unless you have an exhaust brake (Jake Brake), again do not over rev the engine.

 

Newer trucks have all sorts of interesting programing that use a combination of engine management and brake management to control speed going downhill.

I don’t see/experience much difference between gas and Diesel engines when compression braking.  What am I missing?  


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#17 Foy

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Posted 22 June 2021 - 09:28 PM

 

 

And Foy, I may very well have taken click and clack out of context. I didn’t remember it was about everyday city driving.

 

The Click and Clack piece kinda stuck with me because pretty much all trucks I've had as daily drivers from 1973 until 2018 were gassers with manual transmissions, with the 4 years in which the F350 was my daily driver as the one big exception..  I had somewhat more regularly geared down to decelerate in combination with braking during daily driving with most of them until I read the piece.  Then the light bulb popped on and I found myself in agreement with the logic, whether it's right or wrong.  With the big diesel and its 4r100 automatic, I simply maintained the same MO--drive to preserve the transmission, not the brakes.  Still, on steep or long descents--on or off highway--I'll punch it out of OD on the column shift which also disengages the "coast clutch" while keeping the torque converter in lock up mode.  Such allows the same degree of engine braking to get to the drive wheels as would a manual transmission truck. As seldom as that comes up now that she's strictly a "play truck", I don't feel as though I'm hurting the engine one iota.

 

Foy


Edited by Foy, 22 June 2021 - 09:31 PM.

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#18 Machinebuilder

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Posted 22 June 2021 - 11:21 PM

I don’t see/experience much difference between gas and Diesel engines when compression braking. What am I missing?


https://en.wikipedia.../Engine_braking

Does this help?
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#19 craig333

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Posted 27 June 2021 - 08:24 PM

They didn't make an engine brake for my truck. Something about it not working with the auto tranny. Might be time to see if thats still true.


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#20 ntsqd

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Posted 28 June 2021 - 12:11 AM

I learned with our '96 CTD auto (mp tow/haul mode option) that turning off the OD changes the trans programming. With the OD on lock-up only happens in OD. With it turned off lock-up happens as low as second gear. However, with Mopar trans you want to be especially careful in down-shifting. We got a nice long ride on a flatbed tow truck because of a broken band anchor due to a forced down-shift when an unexpectedly steep hill caught me off guard.

 

With no throttle plate diesels don't compression brake as well as gassers do. My old Rabbit diesel did basically no compression braking. The CTD is a bit better, but still not in league with some of the gassers that I've driven.

A true Jacobs Engine Brake interrupts the fuel injection and turns the engine into a large air compressor while holding the exhaust valves open.

 

The engine brakes sold for pick-up truck use don't work that way. They put a throttle plate in the exhaust just downstream of the turbo. For this to work w/o engine damage on a Cummins the exhaust valve springs need to be replaced with higher rate springs or the exhaust back-pressure with the throttle plate closed will 'blow' them open, right into the rising piston! This may  be true for other engines as well, but I've no knowledge about that.

 

Pac Brake's applications: https://pacbrake.com...onGuide-PAC.pdf

 


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