Towing with new Chevy Suburban, cylinder change

[walkers]

[h=2][/h] Mar. 13, 2017, 11:15 PM

I have a old truck but need something more comfortable for around town. I like having two vehicles that can tow and used to have an old Tahoe which came in handy when the truck was in the shop. I Just used it for local hauling.
I haven’t looked at cars/trucks in years and was very surprised when the salesperson told me Suburbans now change from 4 to 6 to 8 cylinders based on speed or something.The truck changes based on speed and more and you can’t disconnect it from happening! He wasn’t very knowledgable and knew nothing about towing.

My questions is how can you tow 2H BP with a vehicle thats constantly changing power like that ? I’d think it would break down pretty quickly and how expensive would that be to fix? I like the safety features in the newer SUV but I just see dollars flying away with all this new technology …My last car had hydraulic air suspension which broke twice, wow was that expensive!
Tow gurus what’s your thoughts?

[Ready_To_Riot]

There should be a “tow/haul” button. It stops it from changing. I didn’t know this and thought my new ram was crap because I didn’t have power. Lol

[soloudinhere]

Tow/Haul mode is a transmission feature and it doesn’t usually have anything to do with active shuttering or cylinder reduction. It just restricts the amount of shifting your transmission does to improve the usage of the power band and reduce transmission wear.

The variable cylinder thing is usually based on engine RPM and thus does not affect towing. It’s meant to shut down cylinders that are not needed for example cruising along on the highway. At flat low-mid RPM it doesn’t need 8 cylinders to keep moving and that doesn’t have anything to do with towing or not. If you were going up a hill, the cylinders would engage just as they would if you were not towing. And no, it does not cause a lot of wear. My 2007 Dodge has this feature and it’s still going strong at 144k miles.

[China_Doll]

@soloudinhere

Tow/Haul mode is a transmission feature and it doesn’t usually have anything to do with active shuttering or cylinder reduction. It just restricts the amount of shifting your transmission does to improve the usage of the power band and reduce transmission wear.

The variable cylinder thing is usually based on engine RPM and thus does not affect towing. It’s meant to shut down cylinders that are not needed for example cruising along on the highway. At flat low-mid RPM it doesn’t need 8 cylinders to keep moving and that doesn’t have anything to do with towing or not. If you were going up a hill, the cylinders would engage just as they would if you were not towing. And no, it does not cause a lot of wear. My 2007 Dodge has this feature and it’s still going strong at 144k miles.

Tow haul mode is also an engine shifting feature for more power in my Chevy

[soloudinhere]

@China Doll

Tow haul mode is also an engine shifting feature for more power in my Chevy

Engines can’t shift, so this makes no sense. The transmission is the only component of the powertrain that does any “shifting.” Shifting requires gears.

You get more power by limiting the transmission’s ability to shift to a higher gear and therefore lower the RPM. You achieve max horsepower at higher RPM ranges unless you are driving a diesel.

Tow/haul is not an on-off button for active cylinder management. Some of the brand new Chevy products do disable when you activate it but it is also locking out overdrive/locking your torque converter/limiting the transmission’s ability to shift. That is why you feel “more power” not because you had 4 cylinders and now you have 8 :rolleyes:

[China_Doll]

You are correct. I wasnt thinking But it keeping in a lower gear makes the engine work harder and it most likely would use more of the cylinders in this instance.

[walkers]

The Suburban SUV changes how many cylinders are being used and so far it looks like this can not be turning off. If I floor it then its on 8 cylinders, highway cruising is 6 and then street may be 4 cylinders. I couldn’t feel the difference during the test drive but when towing I want all 8 all the time. I was hoping this is just on SUV thing hopefully not on full sized trucks.
I was looking at the big SUV as a extra vehicle not my full time towing truck . I had a car that had air compression suspension and it broke twice, first time $1500 to fix and yrs. later broke again then wanted 3K to fix it so I sold it as is. I’m sure when the system breaks for changing cylinders it will be incrediably expensive to fix.
Salesman said it was out of the drivers control it is a of way of making fuel standards.
Ah for a truck w/o all these computers driving the show.

[Heinz_57]

@walkers

I was looking at the big SUV as a extra vehicle not my full time towing truck . I had a car that had air compression suspension and it broke twice, first time $1500 to fix and yrs. later broke again then wanted 3K to fix it so I sold it as is. I’m sure when the system breaks for changing cylinders it will be incrediably expensive to fix.
Salesman said it was out of the drivers control it is a of way of making fuel standards.
Ah for a truck w/o all these computers driving the show.

Fixing anything that breaks in a brand new vehicle is going to be incredibly expensive, though. If you do not want a variable system that changes based on demand, there are lots of late model SUV’s and trucks that would fit the bill (and do not have a base MSRP of nearly $50k!). The switch between 4/8 cylinders takes less than 20 milliseconds, so if you “demand” all 8 - for example, while towing a loaded trailer - all 8 are going to be active. It’s not going to puke around on 4 cylinders while towing your 2H BP, because that amount of weight is going to “demand” the use of 8. There is probably even a gauge somewhere that shows when it’s switching; my experience is with the Dodge version and it did have an indicator in the electronic display, don’t know about the Suburban. The only noticeable difference IMO is that it might cost you less in gas if you drive like a grandma and use it for non-towing a lot. :lol:

Computers have been “driving the show” since the 80’s, generally speaking. Sorry. Kind of hard to avoid them. Since you had a Tahoe you liked, maybe you should look for a slightly older used model in good shape?

[LesleyW]

Guys, it’s a fuel economy feature that’s been around in some vehicles for many years. When the engine is under light load, the computer will shut off the designated cylinders and their fuel injectors to conserve fuel.

It’s very, very unlikely you’ll ever experience this while towing. In a pickup truck it usually only occurs during highway driving. GM and Chevy trucks will usually show you on the information display how many of the eight cylinders are running. Their system, which has been around since the 70s, is called 8-6-4 for that reason.

Although it’s possible for these to malfunction, it’s highly unlikely. While early models of cylinder deactivation systems weren’t that great, they’re pretty sophisticated now and are part of the truck’s engine management system.
There aren’t any flimsy extra parts that are subject to breaking, it’s usually managed with hydraulic oil valves.
Many, many cars also use similar systems (Honda, Dodge, Mercedes).
I wouldn’t worry about it.

[Jim_in_PA]

MDS will not affect towing/hauling because it responds not just to speed, but also load. I have it in my 2012 Grand Cherokee Summit and trust me, it doesn’t shut down cylinders when you are asking the engine to actually work.

[soloudinhere]

My 2007 Hemi has it and not only do I not notice it, but the thing has 144k miles and the engine and transmission are probably the only things on it that haven’t needed repair.

[walkers]

My ram 1500 truck is 2002 and my car is 2004 so yes I was surprised to find cylinder changes on new trucks and Suv’s. My Dodge is not powerful enough to pull loaded 2 HBP trailet. Yes it should be but dealers and others have tried to get this truck to work right and it hesitates on small hills when towing,lurching truck… I added verything on it make it strong for pulling as i bought it new but its just a lemon, 3 transmission under 100K though last one seems to be ok has about 40K on it. Truck is fine when not towing.

[GoForAGallop]

Just so you fully understand how little you’ll notice it…the system switches from 4 to 8 cylinders in .04 seconds. It has been in Dodge trucks since late 2005/early 2006 models.

If you truly don’t believe the hundreds of thousands of people towing and driving these vehicles that you aren’t going to notice it, then you need to start shopping back in the early 2000s.

In terms of reliability, it’s not even remotely comparable to a hydraulic suspension system. Which obviously cost you a lot to fix, considering the types and brands of vehicles you find those on.

[Ready_To_Riot]

Speaking from experience, my 2010 Dodge Ram will in fact shut down to 4 cylinders while hauling. So yes, tow/haul button shuts this off as well as changing the shifting points which gives you more power so to speak. My truck has and “eco” light that comes on and off every time it’s using 4 cylinders. So I know for a fact that does kick in while hauling. It was designed to kick in going over 18mph and anytime you were at a moderate RPM. It will turn off when you need to climb a hill, but just retaining the speep limit on the interstate at 70, you’re pulling with 4 cylinders and it’s awful. It feels awful and powerless and you feel like you can’t get out of the way quick enough if you need to. By pushing my tow button, I turn that off as well as change shifting points, which gives me all the power in the world to climb Mount Everest with my trailer fully loaded if I need.

[LesleyW]

The Eco light isn’t related to cylinder deactivation. It’s a fuel economy indicator, letting you know that you’re either light-footed on the gas pedal, or coasting. Tow/haul gives you more instant power because it changes the way the transmission behaves, giving you quicker access to the torque band. By its nature, it would shut out the cylinder deactivation by giving you maximum power.

[LesleyW]

Here’s a more detailed report, specifically on how Ram manages cylinder deactivation. I spoke to Chrysler engineers when it first came out in the 300 and Magnum wagon - in their systems it works by shutting off the oil supply to those specific lifters, disabling the cylinders.

How Chrysler’s Multiple Displacement System Works

Posted 10/12/2009
By Greg Montero

In 2005, the Multiple Displacement System (MDS) version of the 5.7L HEMI engine was introduced on the Chrysler 300C and Dodge Magnum. This engine can deactivate four of the eight cylinders, and operate as a 4-cylinder engine during periods of low load, improving fuel economy and emissions. The MDS provides the 5.7L engine the fuel economy of a V6 while maintaining the performance of a V8. The fuel economy improvement is estimated to be up to 20 percent, depending on driving conditions. The MDS operation, invisible to the driver, is fully integrated into the fuel injection system.

“In 2005, the Multiple Displacement System (MDS) version of the 5.7L HEMI engine was introduced on the Chrysler 300C and Dodge Magnum. This engine can deactivate four of the eight cylinders, and operate as a 4-cylinder engine during periods of low load, improving fuel economy and emissions.”

When the MDS engine switches to 4-cylinder mode, the powertrain control module (PCM) controls solenoids that manage special “dual mode” lifters, allowing the intake and exhaust valves to remain closed on cylinders 1, 4, 6 and 7. There is one solenoid for each cylinder (two lifters). The PCM also deactivates the fuel injectors for these cylinders when in the 4-cylinder mode.

When the MDS solenoids are in the “off” state (8-cylinder mode), they supply oil pressure of approximately 3 psi to the lifter bores. This lifter oil keeps the bores lubricated and prevents air from entering the system. When the solenoids are activated, oil pressure of 16 psi or greater is supplied to the lifters and the engine enters the 4-cylinder mode.

When the special lifters are supplied high oil pressure by the solenoid, pins inside the lifter move inward. This unlocks the outer portion of the lifter and allows it to move independently from the center portion of the lifter. The camshaft can move the outer portion of the lifter without transferring motion to the inner portion of the lifter.

8-cylinder mode: Solenoids are in the “off” state (de-energized). Minimal oil pressure is applied to the special lifter. They are working normally in this mode.

4-cylinder mode: Solenoids are in the “on” state (energized). High oil pressure is applied to the special lifters and the lifters become inactive and essentially the four pistons are along for the ride. Both valves are closed.

The PCM will activate the 4-cylinder mode when the following enabling conditions are met:

Low engine load

1200 to 3000 rpm

Vehicle speed between 12 mph and 90 mph

Battery voltage from 9 volts to 15 volts

Oil pressure from 15 psi to 147 psi

Oil temperature greater than 120 F

Engine coolant temperature from 158 to 248 F

Ambient temperature from 14 F to 248 F

No throttle position sensor or MDS faults

The PCM deactivates solenoids one cylinder at a time in the firing order. If the system is “on” for long periods of time, such as a long flat road with no stopping, the system will return to the 8-cylinder mode approximately every six minutes to maintain engine temperature. The PCM will also unlock the torque converter before the transition, to minimize the effect on driveability.

[walkers]

Thanks Lesley W for all that information. I think I’ll put more money into my 2002 truck . I would never want to be towing or really even driving a truck with what I just learned from your post. I was really wanting to improve my safety as roll overs kill 25% of people who die in truck accidents because the roof are so weak.(neighborhood has major traffic issues now) After some research I think only Ford has improved the strength of the roof in some of their trucks. Dodge is the worst and they all fail headlight test. Ford is the only one with decent safety rating but the steering on the new Fords is awful…

Seems like everything being built today is just crap and not just trucks.

[soloudinhere]

@walkers

Thanks Lesley W for all that information. I think I’ll put more money into my 2002 truck . I would never want to be towing or really even driving a truck with what I just learned from your post. I was really wanting to improve my safety as roll overs kill 25% of people who die in truck accidents because the roof are so weak.(neighborhood has major traffic issues now) After some research I think only Ford has improved the strength of the roof in some of their trucks. Dodge is the worst and they all fail headlight test. Ford is the only one with decent safety rating but the steering on the new Fords is awful…

Seems like everything being built today is just crap and not just trucks.

I have no idea what roof integrity has to do with anything, but if your truck is “lurching” under load, there is something wrong with the drivetrain and there’s no more “beefing up” you can do that will somehow prevent your truck from rolling over??? I don’t know what engine you have but I hauled with a 2003 Durango with the big Hemi for many years and there was no lurching to be had - and that was on a Dakota driveline. You have an issue somewhere that is unrelated to vehicle “strength” whatever that means to you.

As I said, my '07 has it, I’ve managed to remain upright and safely hauling for 144k miles so far…and I had an old Durango before that and despite its myriad issues, I can’t say it ever ‘lurched’ all all - that one went 95k before I sold it and got the 07.

[walkers]

One last question as the information on COTH has been so helpful.

Are there any trucks that do not have the vairable cylinder changes. I guess diesal but I think beside still ebing so noisy they aren’t that pwoerful or reliable anymore?

So any trucks without this “improvement”?

FYI my dodge 1500 2002 lurches only whole towing up hills( 2HBP )and has had mutiple mechanics look at it including from the factory. Dodge sent him out with me while towing the horses and no they could not figure it out. The gut was really into it but couldn’t fix it and his instaments that he brought along didn’t show what was wrong. This truck transmission broke at 35K then again at 75 K dodge paid for those two but at 100K i had to pay for the THIRD transmission. So its a lemon but after 15 years it still ok but I’d like a bigger trailer and its not going to pull that.

[soloudinhere]

If you want to get something bigger than a 2h bp you aren’t going to want a suburban. You’re going to want a 3/4 ton or larger pickup which will probably not have the active fuel management.

Diesels are more powerful than ever. Not sure where you’re getting info. The emissions systems are annoying but the 2017 Cummins ram lays down an absolutely insane torque figure.