Exhaust Brake for 6.4L - Page 5 - Diesel Forum

**bankspower** · 10-27-2009, 05:31 PM

Quote:

Originally Posted by smotrs

Jeff, cool, so the Foot mode is kinda what I described above like a trailer On/Off mode, making it act more like a manual trans downshift scenario?

I'm actually off this whole week housing hunting. So if you need my truck sooner, let me know. I go back to work on Monday the 2nd.

Exactly, though your brake sounds like it's still on the "high" mode as far as it's aggressivness. Try turning in down to "med" when you are empty as see if that works better

smotrs · 10-27-2009, 06:21 PM

Jeff, I thought the whole High, Med, Low settings were only the Brake On mode, not Speed Control mode? Does the High, Med, Low setting on the Brake On mode affect the Speed Control mode as well?

**bankspower** · 10-27-2009, 06:25 PM

Quote:

Originally Posted by smotrs

Jeff, I thought the whole High, Med, Low settings were only the Brake On mode, not Speed Control mode? Does the High, Med, Low setting on the Brake On mode affect the Speed Control mode as well?

Yes it does. On the iQ you can change it at will, the PDA makes you dig for it. turn it down and try it out

smotrs · 10-27-2009, 06:31 PM

Quote:

Originally Posted by bankspower

Yes it does. On the iQ you can change it at will, the PDA makes you dig for it. turn it down and try it out

Jeff, Will do, I thought because it was on that particular screen that it only affected that mode. Will turn it down and give an update later on how that works.

senix · 10-28-2009, 05:18 AM

great reports, look forward to it.

NEVERSWEAT7 · 10-28-2009, 10:25 AM

Quote:

Originally Posted by senix

great reports, look forward to it.

I too am watching vigilantly

smotrs · 10-28-2009, 06:46 PM

Ok, drove around today, mind you, I haven't hooked up the trailer yet as I wanted to drive in similar conditions as yesterday. Before going anywhere, I switched back over to Brake On mode and verified the brake was set on High then switched back to Speed Control mode and adjusted the preset speed to 35mph. Then I proceeded to drive around a bit so I had something to compare against. Just like yesterday, definitely too aggressive for everyday driving. Soon as you let off on the accelerator, it drops quickly into Tow-Haul mode then jumps quickly into 3rd gear to slow you down to the preset speed. As it nears the preset speed it goes back to 4th gear and then goes through the normal downshift procedure as long as your foot is off the accelerator.

So, after a while of being thrown into the seat belt. I pulled over and switched back to Brake On mode to change the setting to Low then switched back over to the Speed Control mode before hitting the road again. Drove around about 45mph again and this time when I let off on the pedal, just like before it drops quickly to tow-haul mode, but it appeared to wait a little longer for the RPM's to drop before doing the 3rd gear downshift. So I wasn't quite thrown against the seat belt as aggressively as when it was on High. Still a bit more aggressive then you would like for an unladen truck, but add a small trailer or small boat to the back and you may not even notice it as much.

Jeff, so on the Foot On setting, it would be even less aggressive then the Low setting I just described?

**bankspower** · 11-01-2009, 03:14 PM

Quote:

Originally Posted by smotrs

Ok, drove around today, mind you, I haven't hooked up the trailer yet as I wanted to drive in similar conditions as yesterday. Before going anywhere, I switched back over to Brake On mode and verified the brake was set on High then switched back to Speed Control mode and adjusted the preset speed to 35mph. Then I proceeded to drive around a bit so I had something to compare against. Just like yesterday, definitely too aggressive for everyday driving. Soon as you let off on the accelerator, it drops quickly into Tow-Haul mode then jumps quickly into 3rd gear to slow you down to the preset speed. As it nears the preset speed it goes back to 4th gear and then goes through the normal downshift procedure as long as your foot is off the accelerator.

So, after a while of being thrown into the seat belt. I pulled over and switched back to Brake On mode to change the setting to Low then switched back over to the Speed Control mode before hitting the road again. Drove around about 45mph again and this time when I let off on the pedal, just like before it drops quickly to tow-haul mode, but it appeared to wait a little longer for the RPM's to drop before doing the 3rd gear downshift. So I wasn't quite thrown against the seat belt as aggressively as when it was on High. Still a bit more aggressive then you would like for an unladen truck, but add a small trailer or small boat to the back and you may not even notice it as much.

Jeff, so on the Foot On setting, it would be even less aggressive then the Low setting I just described?

Did you ave a chance to try the settings we spoke about on the phone yet?

smotrs · 11-01-2009, 09:50 PM

Not yet, was out house hunting again. Tomorrow I'm gonna drive the truck again so will be able to try it then.

smotrs · 11-09-2009, 06:03 PM

Ok, did some more testing this last week regarding the Low, Med and High settings in both Brake On and Speed Control mode.

Speed Control

Started at a speed of about 50 MPH with the setting on High and a Speed Control set at 20 MPH. When you let off on the accelerator the system immediately drops to Tow Haul and 4th gear, almost right after that it drops into 3rd and shortly after 2nd gear. Mind you, the vehicle is still about 40+ MPH so if you don't have a trailer you'll probably have a bruise on your shoulder where the seat belt was. Med and Low were progressively less aggressive but even in the Low setting it would still drop to 2nd while you were around 35+ MPH or so.

Now mind you, I would have probably had the Speed Control set at 45 typically for that MPH. There's no reason for it being set that low when your average speed is that high. But I wanted to see how aggressive the brake was compared to the Brake On mode.

Brake On

Similar to above, started at a speed of about 50 MPH with the setting on High. Very similar to the Speed Control method above, when you let off the accelerator the system immediately drops to Tow Haul and 4th gear. Shortly after it drops to 3rd gear followed by 2nd gear. Again, speed was still about 40+ but I think it was a bit lower then what it was during the Speed Control test. Kinda hard to tell.

The Med and Low settings were definitely lower though as the Med setting was in the lower 30's before dropping to 2nd gear and the Low setting actually waited until the vehicle was in the higher 20s (around 28 I think) before dropping to 2nd gear, but much more controlled

Brake Off

Lastly, I tried with the Brake turned off to see how the truck would normally act through the downshifting. Mind you, with the brake off, it doesn't use the Tow Haul mode to slow down.

So I'm cruising about 50 MPH, and let off the accelerator. Vehicle begins coasting and gradually goes down through the gears. Didn't get it to drop to 2nd until I started applying the brakes when approaching stop lights but when I glanced at the PDA to see what the speed was it read about 25 or so I think.

Observations

Would have been much easier if there was a way to log the test, then I could have had more accurate results. Oh well. In any case, it appears that the Brake On mode with a setting of Low will give you the closest comparison to how the truck would normally slow down and go through the gears. Mind you, that's the setting I have since left it on for normal driving.

I have also noticed that when you are on a road that has a VERY slight grade, it's best to just turn it off as it will constantly be going in and out of Tow Haul due to even the slightest moderation of your foot on the accelerator to maintain whatever speed your traveling. I'm sure everyone has come across those roads where you kinda hover on the pedal because if you press it you go to fast and due to normal road friction you slow down to much. So you have to hover on the pedal to control the speed. Well, when that happens, it constantly feels like the truck is surging as it goes in and out of Tow Haul mode.

Again, these tests have been done on an unloaded truck doing normal street driving and/or freeway driving.