The reason I ask is because I installed an Edge Insight last week. One of the readings that can be displayed is GPH (gallons per hour).
I set this one up under the EGT (exhaust gas temperature) reading to indicate when regeneration was occurring. During regeneration at 65 mph on cruise EGT's would climb from 800-900 to 1100-1200 and GPH would climb from approx. 3 to 4 gallons per hour.
Also playing with the GPH I noticed the following: when idling @ 600 rpm with the exhaust brake off gallons per hour read 0.4: with the exhaust brake on gallons per hour read 1.4 the same as high idle at 1500 rpm. Did not see any difference in GPH while driving with the exhaust brake on or off.

 

By your information, it sounds like it takes extra fuel to idle with the brake on, but doesn't use more fuel to brake the truck.

 

110k miles on the clock. I've tried running with the e-brake on both empty & towing. According to my experience, it uses more fuel and when towing it seems to have a little less power, meaning I have to put the go pedal down a bit further to maintain my speed. Now I just engage the switch when I need it. I don't leave it on all the time.

 

I was hoping someone actually knew for sure that the exhaust brake uses more fuel when idling or driving. Also if it is possible the edge insight is lying. Under all other driving conditions the gallons per hour shown on the insight appear rational.

 

Here's my take:

The brake uses more fuel when engaged at idle for warmup function. My theory is that it requires slightly more energy to get the exhaust gasses out when the exhaust manifold is under pressure.

The brake does not use more fuel when used at speed for the braking function. This is because the wheels are driving the crankshaft during engine braking, not the pistons. Fueling will be cut to idle levels or even less.

 

I agree. I'm new to this turbo integrated brake, but I've owned a BD brake for 14 years. I never used it to speed warm-up, but I am sure, they don't use more fuel when used to slow the rig.

 

It makes sence to me that it would use more fuel at idle with the EB on. The engine is after all an air pump. If the exhaust brake causes more back pressure, then the engine would require more energy (fuel) to maintain the same RPM at idle while pumping against the higher pressure.

 

I agree with Bigiron - it would have to be using more fuel during warmup, but then, warmup would be shorter time period vrs longer idle time TO warm up, seems prety much moot when both with/without warmups are compared. The brake would have no fuel effect during actual braking against the resistance of speed because the rpm's would be higher due to load against the engine.

CD

 

question on the exhaust brake.... can you hear them when engauged?

 

Yep, nice noise

 

Explanations make sense thank you everyone for your input. ron

 

To update further on the above. When driving in town I like to drive with the exhaust brake on and in the tow-haul mode. While doing this I noticed when stopping fuel consumption would actually rise from 2-3 GPH to 3-4 GPH with my foot off the gas pedal. When the exhaust brake disengaged GPH would drop to 0.7 GPH or less.
Appears this new motor was designed to not only to use fuel for going and cleaning itself but also stopping.

 

Id be interested to know how the edge figured its flow rate?

 

I've always thought that driving with the EB on would lead to worse gas mileage because it increases your drag at times when you would be coasting otherwise...

 

This is a good point. Also, not too many people know it but when the computer gives the engine EGR it has to add fuel to the #5 and 6 cyls. This is because it takes so much of the drive pressure for EGR that the turbo will loose its spool if it doesn't. It mostly adds EGR at lower RPMs so if you consider that the RPMs will be low and emmissions higher during braking it could be seeing an increase in fuel usage because of that. Just a thought.