Diesel exhaust brakes

[HickoryFarms]

It’s not the exhaust brake creating the high rpm conditions, it would be the down shifting. When you’re going down hill like you described, turn tow haul off but leave the exhaust brake on. You should remain in whatever gear you are in, while utilizing the exhaust brake to help maintain your speed. It certainly won’t be as effective without the transmission help to slow you down. But it shouldn’t downshift creating the higher rpms anymore if that’s what is bothering you. The ECM’s on these truck have many safety points built in. In general, the ECM on a stock truck isn’t going to allow it to harm or grenade itself.

 

[HickoryFarms]

I did just read where you said you only have a tow/haul mode button, and not a separate exhaust brake button. There are options out there that might interest you like this:

211-216 F25 & F35 6.7L BD Diesel Exhaust Brake Control Kit 22

 

[Morning Wood]

It’s not the exhaust brake creating the high rpm conditions, it would be the down shifting. When you’re going down hill like you described, turn tow haul off but leave the exhaust brake on. You should remain in whatever gear you are in, while utilizing the exhaust brake to help maintain your speed. It certainly won’t be as effective without the transmission help to slow you down. But it shouldn’t downshift creating the higher rpms anymore if that’s what is bothering you. The ECM’s on these truck have many safety points built in. In general, the ECM on a stock truck isn’t going to allow it to harm or grenade itself.

This is what I was thinking as well. If you want the tranny to help too, can’t you drop the tranny into manual and choose which gear you want to be in so it doesn’t rev up too much?

 

[TMGT]

The rpm on the Cummins isnt really a fair comparison. The 6.7L Cummins has a 3000rpm redline so it will be lower anyways.

 

[tjkubota93]

Like hickory farms said, they design all the stuff to work the way they want it. Most of the time that's not going to let the truck tear itself up. There are exceptions (design flaws) though.

 

[zing]

Itç—´ not the exhaust brake creating the high rpm conditions, it would be the down shifting. When youæ±*e going down hill like you described, turn tow haul off but leave the exhaust brake on. You should remain in whatever gear you are in, while utilizing the exhaust brake to help maintain your speed. It certainly won稚 be as effective without the transmission help to slow you down. But it shouldn稚 downshift creating the higher rpms anymore if thatç—´ what is bothering you. The ECMç—´ on these truck have many safety points built in. In general, the ECM on a stock truck isn稚 going to allow it to harm or grenade itself.

Exhaust brakes require higher RPM to function properly, and is disenguaged in the Cummins once your RPM go below 1200. https://www.cumminsforum.com/forum/4th-gen-powertrain/390342-exhaust-brake-1st-2nd-gear-5.html

This seems to corroborate the responses from you Dodge guys that the Cummins is not revving as high. It says the RPM must be high for better exhaust braking, but quoting 2000 RPM as an effective level is certainly not as aggressive as what I have seen in the Ford and Chev diesels. For my Ford 6.7L it will usually hit hit about 2200 when the exhaust brake kicks in (which I am fine with) but if that does not maintain the truck speed down hill it will gear down again and often hit 3300-3500 on a steep downhill. The Chev Duramaxs would hit even higher RPM. Meanwhile the highest I will see when accelerating would be while trying to get on the highway while pulling a load. Accelerating up a steep on ramp, it usually goes between 2400-2600 before it up-shifts. I would never see the same type of RPM while accelerating, as I do when the exhaust brake kicks in and the tranny downshifts.

TURBOCHARGER EXHAUST BRAKE FUNCTION -The VGT works in conjunction with the engine and transmission to provide an integrated braking system used to help slow the vehicle. This is commonly called exhaust braking. This braking power is achieved by modulating the turbo sliding nozzle ring to restrict the flow of exhaust gases from the engine, which in turn creates a high back pressure on the engine. The high back pressure creates a high level of resistance to the motion of the pistons within the engine and this resistance is used to reduce engine speed and thus vehicle speed.
The exhaust brake feature will only function when the driver turns the exhaust brake switch to the on position. Once the switch is in the on position and the vehicle is moving faster than 8 k/h 1200rpm ; the exhaust brake will automatically operate when the driver removes pressure from the throttle pedal allowing the engine to see 0% throttle and 0 fuel delivery.
Exhaust braking is most effective when the engine RPM is higher. The automatic transmission has been programmed to downshift more aggressively when the exhaust brake is enabled to increase brake performance. Use of automatic transmission Tow/Haul Mode improves interaction between the engine and transmission. Inputs to the exhaust brake feature include:
ï½· Coolant temperature
ï½· Ambient air temperature
ï½· Exhaust manifold pressure sensor
ï½· Throttle pedal position sensor

Dodge Ram Heavy Dutyç—´ 6.7-liter Cummins turbo-diesel engineç—´ VGT is capable of creating the maximum exhaust restriction through a wide range of operating speeds, improving braking performance at low and high engine speeds. Testing has shown more than a 30 percent improvement in retarding torque at 2000 rpm compared with traditional brake exhaust methods.

The 68RFE includes an upgraded torque converter that includes a larger dual-face torque converter clutch (TCC). This TCC yields greater engine torque capacity at highway speeds than its predecessor. The new 68 provides ample capability for aggressive engine braking at max GVW on steep grades via electronic algorithms which control the exhaust brake. We ran the 68 at high-speed WOT dyno trailer tow test at full GCW for acceleration testing and then pointed downhill for the hard-line engine brake test, again at full GCW. The engine braking system is electronically calibrated with the 68 to maximize braking force even under the harshest down-hill cycles.

 

[zing]

Lots of threads asking about how to downshift in order to keep the exhaust brake on since it shuts off at 1100-1200 RPM (talking Cummins again here), but not a lot about how high they tend to rev. This guy commented that it seems to be max efficiency between 18-2800. Overall that seems to be about 500-600RPM less than where the Ford 6.7L seems to be working best at.
https://www.cumminsforum.com/forum/07-5-09-3rd-gen-6-7-liter-general-discussion/427361-6-7-exhaust-brake-how-do-i-know-its-working.html

The EB {exhaust brake} works better as higher RPM, it doesn't work like the Duramax where the engine "over revs" for better braking, but in order for the EB to work the engine needs to be moving air. Between 1800-2800rpm seems to be where it's most effective and you should see 10+ PSI of boost when the EB is engaged at higher RPMs. The EB disengages once the RPMs drop to 1100 and under normal driving conditions the EB only engages in gears 3 through 6. When I'm towing and going down a steep grade very slowly in 1st gear the EB will also engage but it won't lock the torque converter.

 

[some zilch]

an automatic and an exhaust brake :laughing:

never driven one in any size that worked

we jokingly called them "exhaust flappers"

 

[deerefan]

an automatic and an exhaust brake :laughing:

never driven one in any size that worked

we jokingly called them "exhaust flappers"

Mine works very well.

 

[HickoryFarms]

The rpm on the Cummins isnt really a fair comparison. The 6.7L Cummins has a 3000rpm redline so it will be lower anyways.

I don’t even shift until 3 grand with my cummins when I’m towing. It’s not a fair comparison because an inline 6 and a v-8 are being compared. Power bands are way different.

Exhaust brakes require higher RPM to function properly, and is disenguaged in the Cummins once your RPM go below 1200. https://www.cumminsforum.com/forum/4th-gen-powertrain/390342-exhaust-brake-1st-2nd-gear-5.html

This seems to corroborate the responses from you Dodge guys that the Cummins is not revving as high. It says the RPM must be high for better exhaust braking, but quoting 2000 RPM as an effective level is certainly not as aggressive as what I have seen in the Ford and Chev diesels. For my Ford 6.7L it will usually hit hit about 2200 when the exhaust brake kicks in (which I am fine with) but if that does not maintain the truck speed down hill it will gear down again and often hit 3300-3500 on a steep downhill. The Chev Duramaxs would hit even higher RPM. Meanwhile the highest I will see when accelerating would be while trying to get on the highway while pulling a load. Accelerating up a steep on ramp, it usually goes between 2400-2600 before it up-shifts. I would never see the same type of RPM while accelerating, as I do when the exhaust brake kicks in and the tranny downshifts.

Exhaust brakes require the torque converter to be locked on an automatic, otherwise there is no way to slow the drive train. The torque converter being locked is RPM based. The effectiveness of the exhaust brake itself will not be altered by the RPMs.