Exhaust Brakes - Montana Owners Club

BandJ · 07-31-2005, 12:30 AM

I would appreciate some information about Exhaust Brakes. What are they. Are they expensive. What is the advantage of installing them.

oldudbob · 07-31-2005, 01:27 AM

Here are two links to sites where you might get answers most of your questions.

http://www.drivetrain.com/exhaustbrake.html
http://www.bankspower.com/tech_howexhaustbrakeworks.cfm

richfaa · 07-31-2005, 01:42 AM

If you have tow command or tow haul you really don't need exhaust brakes.

virgil47 · 07-31-2005, 01:42 AM

Bryan,

Here is an explanation. I am not nearly this technical but Googled "exhaust brake" and used cut and paste. The following is what I found in several different places that made sense to me.

The gasoline engine is designed with a carburetor or injection system that includes a throttle valve often referred to as a butterfly. When the accelerator, or throttle, is not engaged, as when braking, the butterfly closes off the air intake of the engine forming a compressor effect that assists the vehicle in braking. This is not possible in diesel engines because they have no throttle butterfly. When the accelerator of the diesel engine is released, no compression is developed and the brakes of the vehicle are giving the entire task of stopping the vehicle. An exhaust brake uses a butterfly valve behind the turbocharger or in the exhaust pipe to restrict the flow of exhaust gas. When the valve is closed, the butterfly restricts the exhaust flow much like the old "potato-up-the-tailpipe". This forces the engine to act like a large air compressor and results in engine braking better than many gasoline engines can produce.

On my F250 I have a BD Exhaust brake and it has worked beautifully so far. On a recent trip to the Western NC mountains, I rarely touched the brakes when descending long grades. It seems to work reeally well in conjunction with my manual tranny as I can continue to go to a lower gear if the speed gets excessive.

lightningjack11 · 07-31-2005, 04:18 AM

Here is what my DIY Exhaust brake means to me.

Going down a long 8% grade with exhaust brake on and TC locked I will descend at 50mph without applying trailer brakes or truck brakes. As long as no one stops in front of me. So for me it is safety.

richfaa · 07-31-2005, 05:12 AM

The same thing occurs with my 05 F350 in Tow haul mode. Just did the WVa Turnpike (I-77) with all those 7 and 9% grades and never had to touch the brakes unless someone in front of me did. Note that we were traveling with a friend in a 99 Dodge Diesel with the exhaust brake and both systems performed the same. Do more homework but if you have tow haul or tow command I don't think you need to spend the $ on the jake brake. Personal choice of course..

sreigle · 07-31-2005, 12:40 PM

The descriptions of how gas and diesel differ are pretty accurate to the best of my knowledge. However, they're not exactly current. The Ford 6.0 does provide some form of exhaust backpressure. The turbo has a 'variable vane geometry' meaning they open and close according to the demand. During an off-throttle grade descent they close, or nearly so, thus providing backpressure.

Combined with the transmission downshifting in tow/haul, I find the downhill grade holding in this diesel far superior to the gas V10 with the 4R100 (is that right?) automatic transmission. Even when not towing and not in tow/haul this truck slows at least as well as did the gas engine. While an exhaust brake would add even more braking, I really don't see a need with this truck since it holds speed even better downhill than did our V10 gasser.

Just my personal observations.

bob n pam · 07-31-2005, 12:53 PM

We had a PacBrake on our previous TV, a 96 Dodge, Cummins engine, and wouldn't have been without it. It added a measure of safety that we felt was important. It was well worth the expense involved.

BillyRay · 07-31-2005, 02:00 PM

they are nice, but we too have the tow haul mode, and with that, we don't need one.

virgil47 · 07-31-2005, 02:21 PM

Bryan,

Steve is right (again). One of us should have asked you what kind of TV you had. Depending on your answer, the answers provided may have been a lot shorter.

Ormee and Ginette · 07-31-2005, 02:31 PM

I am a bit confused as to how the TOW/HAUL mode of either the Ford or GMC Allison transmission will down shift if your speed is too high and you must apply brakes to get the vehicle under the engine's Red line before the transmission will downshift... This has been my experience with my set up with the 2003 / 3500 GMC Duramax/ Allison combination... I have found that if I am traveling say at 100km/hr or 66mph then I must get the vehicle to around 85km/hr or about 52mph the only way of doing this is with the vehicle's brakes... How does the Tow/haul help out in this situation??? The reason I am asking this is because I am interested in having a BD Engine Retarder installed... I have gotten quotes at 1595 CDN $ and 4 hours labour at 85 CDN $ plus taxes...

Bill Hill · 07-31-2005, 03:31 PM

BandJ,
You didn't say what TV engine/tranny combo you have, but I have to assume that you have a diesel. Virgil47 was right on with his explanation and sreigle is correct too. The newer Ford PSDs have a different turbo than the GM or Dodge diesels and doesn't seem to require an exhaust brake. But if you have a GM or Dodge, it's the safest way to go. If you have a GM product with the Allison transmission, the tow/haul mode with downshift the transmission and will lock up the torque converter, both of which are important. But that doesn't give you the backpressure that you need for braking. The torque converter lock-up is important because if it doesn't, there is slippage that makes for less efficient braking AND significant heat build up of the transmission fluid, neither is a good thing.

Like many things, it is a personal thing, but it really is the safe way to go. You asked about price, somewhere between $1,000 to $1,500. It's money well spent in my opinion.

sreigle · 08-01-2005, 07:38 AM

Ormee, my understanding is the grade braking of the automatic transmission in the GM is very similar to the Ford. So I hope my explanation is accurate for the GM. On mine, if in tow/haul and you start down a grade AND are giving it NO throttle, when speed increases 3 to 5 mph the transmission downshifts a gear. If it continues to gain another 3 to 5 mph it downshifts again. At some point you are at a speed where the engine would be over-revved if it downshifts again. In that situation you will have to brake to bring the speed down. As soon as you reach a speed safe for the downshift it will do so. This situation is extremely rare. That is one situation where an exhaust brake would be an advantage but it is so rare I've only experienced it one time. I just used the brake to slow down to about 45 and it downshifted again.

Also, if you want it to shift more quickly you can step on the brake for a second or two and it will downshift, assuming you are off-throttle and it won't be over-revving.

My understanding is the GM works the same way. Someone correct me if I am wrong.

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