Whether to or when to downshift

[Astro Imager]

Greetings to everyone!

Starting the 1300 mile journey south for the winter season from Washington.  We have some fairly steep climbs that I want to understand better about how to climb with the Alison in our 2009 Camelot 42’.  Coming home this last June, we encountered a couple ‘Stop Engine’ lights and lost power at uncomfortable spots on the road.  This summer I drained the coolant and flushed the system after degreasing and cleaning both sides of the CAC & the radiator.  Re-Filled the coolant system with Final Charge (Red) and topped it off after a couple short runs as needed.  I also replaced the recovery tank pressure cap.  All this in hopes of not repeating the Stop Engine issues.  My question is this;  I’ve been told by several people I trust with years of diesel driving experience that I’m not driving the transmission aggressively enough if I’m just leaving it in D.  Yet I have a very experienced friend on this forum who I’ll call my “Sensei”, tell me that it’s not necessary with the excellent Alison Transmissions we have.  Can I help myself avoid these hot engine issues by keeping the RPM’s higher and the torque in a better range when starting up grades?

 

Thank you for your consideration,

Dale

[DavidL]

Push the Go pedal to go faster.

Your transmission knows how to shift.

There is no such thing as "not driving it hard enough".

If the motor was getting hot, then your coolant system needed maintenance (hopefully what you have already done)

 

[JetAburner]

I like to manually shift keeping it between 1500-2000. I know that the ISC hits peak torque at 1200, and the book says you can WOT down to 1200, but after years of trucking, I don't like to pull em that low. On the other hand, the ISC doesn't like to twist high either. After 2000 your pretty much out of the torque range. Just my 2cents.

[Dr4Film]

You didn't post what engine your coach has but here goes my advice. When I had the Windsor with the ISC-350 plus the Banks Power Pack, on really steep grades the throttle was WAO pedal to the floor. If needed the Banks would de-rate the engine if the EGT got over 1250F. Plus I always kept the rpm's at peak HP.

Now with the ISL-400 chipped to 425 I watch my rpm's and if they get too low I will always downshift to bring the rmp's back up to peak HP.

Rolling grades I will let the Allison do it's thing but on steep grades I will help the Allison and engine do a better job of climbing.

Edited October 10 by Dr4Film

[Frank Bergamo]

Higher RPM’s means more coolant circulation. Drop to a gear that allows climbing a grade, but holding RPM’s a little below red line on tach. Whatever that means for your coach, find that gear and leave it there. If it is still overheating doing this, then there is another problem that needs diagnosing. Hope this helps, good luck!

[Tom Cherry]

4 hours ago, Astro Imager said:

Greetings to everyone!

Starting the 1300 mile journey south for the winter season from Washington.  We have some fairly steep climbs that I want to understand better about how to climb with the Alison in our 2009 Camelot 42’.  Coming home this last June, we encountered a couple ‘Stop Engine’ lights and lost power at uncomfortable spots on the road.  This summer I drained the coolant and flushed the system after degreasing and cleaning both sides of the CAC & the radiator.  Re-Filled the coolant system with Final Charge (Red) and topped it off after a couple short runs as needed.  I also replaced the recovery tank pressure cap.  All this in hopes of not repeating the Stop Engine issues.  My question is this;  I’ve been told by several people I trust with years of diesel driving experience that I’m not driving the transmission aggressively enough if I’m just leaving it in D.  Yet I have a very experienced friend on this forum who I’ll call my “Sensei”, tell me that it’s not necessary with the excellent Alison Transmissions we have.  Can I help myself avoid these hot engine issues by keeping the RPM’s higher and the torque in a better range when starting up grades?

 

Thank you for your consideration,

Dale

This is the way I drive mine 09 Camelot….have almost 65K of me driving it new…. Hill climbing….you need to never use the cruise.  Get a running start and then start to downshift when the RPM gets down to say 1500 or so.  Anything below that….you don’t have max HP.  The things I learned, and I have been out west a few times and been on some major grades….you want to keep the engine RPM UP.  Push the TEMP button and monitor the engine and the tranny.  I climbed up….a LONG grade into Sequoia.  I kept the RPM a little low…maybe 1600.  It was going OK, but if you keep the rpm nearer 1800/2000.   then you get MORE cooling.  No idea since I have never had a “light”, much less a downrate situation.  If I had kept the RPM nearer 1600, the tranny was getting hot.  Try to keep the tranny at maybe 210/12….the fluid is good for much higher…but the valves are not happy much above 225.  I don’t think I have ever been there.

If there are pull offs then do that and let it idle….and then let traffic pass.  As long as you watch the temps….engine below say 205 and tranny below 215/220….you should be good to go.  That has worked for me for over 14 years.

If you get a light, call out the engine and tranny temps to our wife to write down.  Never climb, or descend, without dash screen on TEMP and monitor that. I sometimes will max out…and the “rev limiter” kicks in around 2100/2200. Downshift for a while…but if the temps climb…slow down and then downshift tomkeep the revs up.  Cooling is better.  A cooler engine is a happier engine.

If you get lights….find a GOOD CUMMINS shop and have then look at the codes.  Money well spent.  You need to know what caused it.  May be a bad sensor or who knows.  Don’t want to be penny wise and pound foolish with that engine….

[Frank McElroy]

Look up the Torque vs RPM and HP vs RPM graphs for your engine. You want to climb long grades at an RPM near max HP NOT max Torque.  To keep the RPM high at max HP you will likely need to manually downshift and climb at a lower speed.  You never want to climb a long grade at wide open throttle letting the transmission to select the gear to climb at max speed.  Climbing long grades near max HP puts the least amount of strain on the engine and cooling systems.  Climbing long grade at WOT to maintain maximum speed puts the most strain on the engine and cooling systems and generates high exhaust temperatures.

[Dr4Film]

Following up on Frank's previous post.

https://www.dieselhub.com/tech/horsepower-vs-torque.html

[Tom Cherry]

1 hour ago, Frank McElroy said:

Look up the Torque vs RPM and HP vs RPM graphs for your engine. You want to climb long grades at an RPM near max HP NOT max Torque.  To keep the RPM high at max HP you will likely need to manually downshift and climb at a lower speed.  You never want to climb a long grade at wide open throttle letting the transmission to select the gear to climb at max speed.  Climbing long grades near max HP puts the least amount of strain on the engine and cooling systems.  Climbing long grade at WOT to maintain maximum speed puts the most strain on the engine and cooling systems and generates high exhaust temperatures.

https://www.rvtechlibrary.com/engine/ISL425_specs.pdf
 

Here is the “book” on the ISL425 that is in the Camelots or Scepter…..I think it might be the same in the Dynasty, but the Dynasty has the additional Jacob’s (JAKE) Brake….  See below the main spec sheet screen shot from the above.

I totally agree with Frank.  Keep the engine near the top end…the Rev Limiter will take care of the engine.  Only upshift when you are climbing and the grade is reduced….so that you can run in a higher gear…..but keep the RPM’s up…Look at the HP curve chart….

[Astro Imager]

We have the ISL425 Cummins in our ‘09 Camelot.

[Rocketman3]

If in doubt - get behind a full semi and just follow him up.  When I was having overheating issues - often I would just follow a semi up on 3rd gear.

In 4th my engine load (on my Silverleaf computer) would be 100% and I could pass semi’s. In 3rd and following a semi it was often about 60-70% load - but the RPM’s high which helped me keep the temperatures down.  
 

Your not in a race.

[Gary Cole]

9 minutes ago, Rocketman3 said:

9 minutes ago, Rocketman3 said:

Not in a race. So true.

 

 

Edited October 11 by Gary Cole

[96 EVO]

6 hours ago, Astro Imager said:

Greetings to everyone!

Starting the 1300 mile journey south for the winter season from Washington.  We have some fairly steep climbs that I want to understand better about how to climb with the Alison in our 2009 Camelot 42’.  Coming home this last June, we encountered a couple ‘Stop Engine’ lights and lost power at uncomfortable spots on the road.  This summer I drained the coolant and flushed the system after degreasing and cleaning both sides of the CAC & the radiator.  Re-Filled the coolant system with Final Charge (Red) and topped it off after a couple short runs as needed.  I also replaced the recovery tank pressure cap.  All this in hopes of not repeating the Stop Engine issues.  My question is this;  I’ve been told by several people I trust with years of diesel driving experience that I’m not driving the transmission aggressively enough if I’m just leaving it in D.  Yet I have a very experienced friend on this forum who I’ll call my “Sensei”, tell me that it’s not necessary with the excellent Alison Transmissions we have.  Can I help myself avoid these hot engine issues by keeping the RPM’s higher and the torque in a better range when starting up grades?

 

Thank you for your consideration,

Dale

Do you 'Know' your engine temperature was high, or just that you were getting Stop Engine Lights?

425HP ISL's have a habit of getting high crankcase pressure. Don't know if it will de-rate the engine though. 

[Frank McElroy]

25 minutes ago, 96 EVO said:

Do you 'Know' your engine temperature was high, or just that you were getting Stop Engine Lights?

425HP ISL's have a habit of getting high crankcase pressure. Don't know if it will de-rate the engine though. 

Yes, high crankcase pressure will derate and could throw a stop engine light if bad enough. The only way to know for sure what caused the stop engine light is to look at the engine code history report via Insite software.

[Jim Pratten]

 

I used to have the ISC 350 Power v RPM graph (from this brochure) taped to the console.  When going up a pass, I try to keep the rpm around 2000. 

[Tom Cherry]

9 hours ago, Frank McElroy said:

Yes, high crankcase pressure will derate and could throw a stop engine light if bad enough. The only way to know for sure what caused the stop engine light is to look at the engine code history report via Insite software.

There is a crankcase filter on the valve cover that is accessible from the two removable covers in the bedroom.  That filter, at least on mine, is a bit persnickety.  Unless you have records or such, changing it would be a good and cheap PM.  The filter is readily available online and easy to change.

Frank gave me a few tips.  Remove the old one, clean the sealing surfaces as well as doing some housekeeping on the valve cover. Get the new one seated, firmly in place….then get the bolts started and use the crisscross pattern and bring or seat it, down a smidge at a time to make sure it is sealed.

There are several threads out there on this.  Cummins also has a recommended method for verifying the accuracy of the dip stick.  Many shops will overfill.  Contact Cummins and verify the total oil capacity with filter and then make sure that the correct amount is put in.  In this case, MORE is NOT better….

[Gary Cole]

Driving an engine hard? I have no idea why anyone would think that increased heat, vibration,  and material stress would increase the life of their engine. Detroit once provided data on their 71 series of engines which plotted horsepower rating against mean time failure and engine life. Engine life and component failure was indirectly/directly proportional to horsepower rating. In other words, engine life and failure is indirectly/directly proportional to where you generally keep your foot.

Edited October 11 by Gary Cole

[Dr4Film]

Where you keep your foot also plays a direct role and outcome of your mpg.

[Astro Imager]

The first thing I did 2/3 of the way home on that homeward bound trip was to replace the Crankcase Filter.  I had no record of its previous replacement and it did look a mess.  Carefully replaced it and with more attention paid to RPM’s and gear selection, the issues did not repeat on the balance of the trip.

Thank you all for your thoughts on this.

 

Dale

[96 EVO]

Watch your Aladdin screen next long climb to see what your actual engine temp is getting to.

Not trying to scare you, but a 425 ISL owner I met, started getting stop engine lights for hi-crankcase pressure. He changed out the filter, but it didn't solve the issue.

Haven't heard from him for a while, so don't know what the resolution was.

I replaced my crankcase breather filter at 55,000mi, and it was almost as clean as the new filter I replaced it with. This was on the 400hp ISL.

Definitely a good idea to invest in a monitor like a Scangauge D, or better, that can display the fault codes!

Without the code from the Engine Control Module, best we can do is guess!

Edited October 12 by 96 EVO

[HarleyR]

From the time I bought my motorhome, I had attempted to solve my overheating problems first by flushing the cooling system, then by replacing the radiator. I finally received the proper diagnosis from "The Little Diesel Shop" in Kelowna, BC after a very tedious summer climb over the Rockies. My hydraulic radiator fan was not operating properly due to my hydraulic pump failing. A replacement was not available in North America! The manufacturer was in Italy, but had no replacement parts. They could, however, manufacture and supply a replacement of the discontinued pump next year for $7 or $8,000. I limped home to the east coast, and my mechanic found a clever hydraulic specialist who found a replacement and the problem was solved. I never knew how easy my coach was to handle with power steering that actually worked!!

I sincerely hope that your problem is easier and cheaper to solve, but my story may help in your diagnosis. 

[Steven P]

On 10/11/2023 at 8:05 PM, 96 EVO said:

I replaced my crankcase breather filter at 55,000mi, and it was almost as clean as the new filter I replaced it with. This was on the 400hp ISL.

I have a 400 ISL too.  Where is the crankcase breather? Do you have a part #? Source?  Thank you. 

[96 EVO]

Steven, they made a big change of that filter for the '07 compliant engines.

Yours and mine won't be the same at all, and possibly not even installed in the same location on the engine.

[Steven P]

@96 EVO gotcha.  Thanks. 

[Bill R]

@Steven P You should have a crankcase breather with a drain tube back to the crankcase and blowby tube that runs down and exits by the starter.  @96 EVO is correct that our year 400ISL engines do not have the filters though.  See image below.  Number 6 points to the crankcase breather on top of the engine.