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GreaTOne65 · 09-29-2015, 07:31 PM

Well, I went and weighed my coach today, a whopping 32,800 lbs. full of water and fuel. My question, economy mode or not, this thing will not shift into 6th under 60 mph. so any thoughts of economizing by driving under 60 is a fallacy, in my coach that is! Next, the EGT, really has me worried, in 6th gear, laying on the loud pedal at 60, produces 1300 degrees. That really worries me, considering the terrain we are about to attempt next month. Another nagging problem, she builds air, 130 lbs. pops off the dryer, but on the road, pressure drops down to 105, and stays there? That's not the way our Road Tractors worked, and the way my Discovery worked, what are your systems working like?

2 Stroker · 09-30-2015, 10:47 PM

Quote:

Originally Posted by GreaTOne65

Well, I went and weighed my coach today, a whopping 32,800 lbs. full of water and fuel. My question, economy mode or not, this thing will not shift into 6th under 60 mph. so any thoughts of economizing by driving under 60 is a fallacy, in my coach that is! Next, the EGT, really has me worried, in 6th gear, laying on the loud pedal at 60, produces 1300 degrees. That really worries me, considering the terrain we are about to attempt next month. Another nagging problem, she builds air, 130 lbs. pops off the dryer, but on the road, pressure drops down to 105, and stays there? That's not the way our Road Tractors worked, and the way my Discovery worked, what are your systems working like?

My wt is 33620 and it shifts into 6th at 55mph and the rpm is 1500, full of fuel and only 1/2 on the water about 50gal.
My air is 110 to 120 all the time, sounds like you need to take it in

2 stroker

Dakrism · 10-01-2015, 07:19 AM

You may need to have an Allison tech reprogram your tranny so you can shift into 6th gear sooner and stay there while cruising around or under 60 mph.I had mine done in Ocala at Detroit Diesel. I can now get into 6th gear at 59-60 mph and more importantly I can stay in 6th with the economy mode down to 55-56 mph.The tech charged me $100.

I also had him change the pre-select on the engine brake from 2nd gear to 3rd.I don't get such a "hard" dowshift in traffic now.

My air system is doing just like yours. It is popping off at 130 but when driving it stays at 106/109. I have been told to replace the regulator. It looks like a simple job and not too expensive but I am not too good with tools so I am procrastinating on doing the job.

Steve Ownby · 10-01-2015, 07:46 AM

Quote:

Originally Posted by GreaTOne65

Well, I went and weighed my coach today, a whopping 32,800 lbs. full of water and fuel. My question, economy mode or not, this thing will not shift into 6th under 60 mph. so any thoughts of economizing by driving under 60 is a fallacy, in my coach that is! Next, the EGT, really has me worried, in 6th gear, laying on the loud pedal at 60, produces 1300 degrees. That really worries me, considering the terrain we are about to attempt next month. Another nagging problem, she builds air, 130 lbs. pops off the dryer, but on the road, pressure drops down to 105, and stays there? That's not the way our Road Tractors worked, and the way my Discovery worked, what are your systems working like?

I'm not familiar with the torque/HP peaks for the C9 but the up shift point is dependent on the peak torque rpm. In flat to gently rolling country, you can maximize your time in top gear. With the Allison in economy mode, accelerate until you get the 5-6 up shift. Then slowly ease out of the throttle until your rpm is just above torque peak. It will take some trial & error to fine an rpm what will not cause a downshift when a very slight up grade presents its self.

Is the EGT gauge OEM or aftermarket? If OEM I would be concerned about 1300 degrees also. If aftermarket, it would depend on where the sensor is located and calibration.

Steve Ownby
Full time since '07

GreaTOne65 · 10-01-2015, 07:29 PM

Thanks for the replies, and the advice, guys! It's kind of a conundrum, the 5-6th gear isn't much of a problem, I like to run 65 mph anyway. I just found it curious people who would be trying to run 55 in this coach wouldn't have a chance. The pyrometer reading is problematic, I have driven it far enough now to get an idea of what it's doing, and what it takes to make it reach those high temperatures. I have installed a number of them, and today, I looked at it with a critical eye. I only had one place that it could go, between the 4-5 cylinders, according to Autometer that should be ideal. There is no calibration on the gauge, after your suggestion, Steve, I called Autometer, they assured me, it has been calibrated at the factory and nothing needs to be done? So now, I'm really spooked, Mon. it hit 1300 degrees, on just acceleration, what happens in NM.-AZ. mountains??

tankcj · 10-05-2015, 10:14 AM

What is the normal EGT for a Cat C9? I did a little searching and what I was seeing is that 1300 deg isn't out of the norm for diesel engines.

GreaTOne65 · 10-05-2015, 08:25 PM

tankcj, I have been driving semi's, farm tractors, for years, and it has been a cardinal rule, 1250 for only a few seconds, or suffer the consequences! I have heard that some engines have been running steel tops on the pistons, and that they can withstand the high exhaust temperatures. I think it may be time for me to call my local Cat dealer?

hardint · 10-07-2015, 10:34 PM

You can think the Greenies of the Government for your EGT's, to meet emissions the manufactures have to have high temps to clean up the exhaust,most any late model diesel will see 1300 under load, my C9 doesn't have a egt and unless you had the power turned up from stock drive it like ya stole it, back when I had a 12 valve 5.9 Cummins I worried,then got a 05 Common rail 5.9 and with programmers and towing 1500 on hills was way to often but it still runs like a striped ape . JMO
On the tranny my only issue is in town or slow driving it will up shift early and it gets this surging until you make it down shift or ride it out till speed increses.

Bucky1320 · 10-16-2015, 10:42 AM

My 3126 won't go into 6th until 60, but I can drive anything over 53 after it goes in.
Cruise is weird in mine. Rolling hills aren't an issue. But Get to something more, and the cruise will simply shut off when it reaches a higher percentage of throttle. Kinda weird. Probably just as well though. Makes me take over one grades which is probably good.

GreaTOne65 · 10-16-2015, 07:27 PM

Hwy Bucky, I had a '99 V-10 that sounds a lot like your 3126. When the V-10 couldn't make the hill, and the cruise dropped out, it would lose it's momentum, and it would end up at 25 mph! I got used to anticipating when the engine was about to run out of the cruise, and I could catch it on the pedal before it lost it's guts! LOL!! I hope this C-9 is as good as my '99 5-9 L Cummins, that thing never lost the cruise, just seemed to keep pouring on the coal, just had to keep shifting back to keep the EGT under control.

Bucky1320 · 10-20-2015, 11:32 AM

We were going through the rolling areas of iowa this weekend with the 9k lb trailer behind us. Cruise wasn't going to work for it. But man the 3126 ran flawlessly! The wind tends to push the front of this rig around a bit though. Once the wind died down we were 65 mph or better all the way home. I run out of bravery before I run out of power!