Manual but without a clutch?

6592 Views 16 Replies 9 Participants Last post by obermd, Jul 25, 2016

mws_1984

Discussion Starter · Jul 23, 2016

I have an automatic Chevy Cruze but I'm told it has this option on the shifter.

Vehicle Gear shift Car Honda Hatchback

Is the D and the +/- basically treated that way?

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obermd

· #2 · Jul 23, 2016

D is the standard automatic Drive instruction to the ECU. The Manumatic controls are accessed by pulling the shifter to the left while in D(rive) and then pushing forward to shift to a higher gear and back to a lower gear. Unlike a true manual the ECU will not let you make a dangerous (to the transmission) shifts. I've driven Manumatics and about the only place I find them useful is for engine braking or long distance highway driving.

NickD

· #3 · Jul 23, 2016

Same here especially on steep downhill grades for engine braking, sure saves on way overheating the brakes. Yep, there is a cop at that bottom of that hill just waiting to give you a speeding ticket for a couple of miles over the speed limit.

May also learn you are getting better fuel economy in driving in 2nd or 3rd gear in town rather than 4th or 5th. Loading the hail out of that engine.

spacedout

· #4 · Jul 23, 2016

obermd said:
I've driven Manumatics and about the only place I find them useful is for engine braking or long distance highway driving.

How about in stop and go traffic so you can keep the transmission locked in a lower gear to keep if from continually up shifting and downshifting as traffic speeds up and slows down? Its also great to lock the car into a lower gear for hills, I've driven for hours in 5th in a hilly areas when I couldn't keep my speed much above the 6th gear 42mph shift point(winter conditions). Never owned an automatic without this drawback, there will always be some speed your driving near a shift point, only way to solve this constant hunting between gears is to use manual mode.

Interesting thing I've noticed:
The cruze automatic seems to have some sort of angle/sensor that once the car downshifts for a hill it will hold the lower gear until the hill flattens out. If starting from a stop it will also automatically hold the lower gear to a higher RPM on even a slight incline even with very light throttle inputs that would typically shift at a much lower RPM.

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obermd

· #5 · Jul 23, 2016

spacedout said:
How about in stop and go traffic so you can keep the transmission locked in a lower gear to keep if from continually up shifting and downshifting as traffic speeds up and slows down? Its also great to lock the car into a lower gear for hills, I've driven for hours in 5th in a hilly areas when I couldn't keep my speed much above the 6th gear 42mph shift point(winter conditions). Never owned an automatic without this drawback, there will always be some speed your driving near a shift point, only way to solve this constant hunting between gears is to use manual mode.

Interesting thing I've noticed:
The cruze automatic seems to have some sort of angle/sensor that once the car downshifts for a hill it will hold the lower gear until the hill flattens out. If starting from a stop it will also automatically hold the lower gear to a higher RPM on even a slight incline even with very light throttle inputs that would typically shift at a much lower RPM.

Good points - I'm a row my own gears guy. As to your observation about holding the lower gear I don't think its a angle sensor. My ECO MT does the same thing with the shift light and doesn't trigger it if I'm going uphill. I suspect it's the load on the engine that the ECU is monitoring so when the engine is loaded the ECU won't shift up (or trigger the shift light in the manuals) until that load is gone.

spacedout

· #6 · Jul 23, 2016 (Edited)

obermd said:
As to your observation about holding the lower gear I don't think its a angle sensor. My ECO MT does the same thing with the shift light and doesn't trigger it if I'm going uphill. I suspect it's the load on the engine that the ECU is monitoring so when the engine is loaded the ECU won't shift up (or trigger the shift light in the manuals) until that load is gone.

If it was engine load then if I let my foot off the gas slightly it should shift like every other automatic or exactly like it does normally. On even the slightly incline(less than 1% grade) it will hold gears all the way to 3000RPM even under very very light throttle and even if you attempt to let off the gas slightly to cause the shift. This is much more pronounced in hills in the lower gears below 25mph.

Another example f why I say it doesn't seem engine load based, lots of hills around here will level out to some degree about half way up and with a typical automatic the car thinks its all OK to use OD again since the load is gone only to have to downshift again to finish the hill 15 seconds later. Drive that same hill with the cruze, once it has downshifted it will never shift out of the lower gear until the car is perfectly level again at the very top for 3+ seconds. That 20-30 second somewhat level spot in the middle on the hill the car has no problem maintaining cruise control set speeds in 6th gear, yet will remain in the lower gain until the car is creased the hill / leveled out.

I've now driven about 140,000 miles so far on the 6T40/1.4T combo and have yet to find any grade hill that ever leveled out enough to cause the cruze to shift back into top gear, something I've had every other automatic car I've ever driven do. You may be right that it's load based, it just it doesn't seem to be on how it behaves. The vehicles stability control system uses Yaw, pitch and steering angle sensors and hill hold technology uses that same data to know when to engage, It would not be far fetched to think the automatic transmission also uses the yaw sensor data as well.

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obermd

· #7 · Jul 23, 2016

Foot off the throttle reduces or eliminates the torque demands on the car. No reason to shift. The Cruze definitely doesn't behave like other cars when it comes to upshifting. It appears the ECU wants to verify that it won't be commanded to provide more torque than what it thinks is comfortable for the speed. Your comment about using the yaw sensor could be a critical observation, both in shift (light) behavior and in the cruise control's seemingly prescient ability to engage and disengage early to prevent the car from overshooting the set speed at the top and bottom of hills.

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spacedout

· #8 · Jul 23, 2016

obermd said:
Your comment about using the yaw sensor could be a critical observation, both in shift (light) behavior and in the cruise control's seemingly prescient ability to engage and disengage early to prevent the car from overshooting the set speed at the top and bottom of hills.

The cruise control is amazing in this car. Even if you have gained speed down a hill well in excess off the MPH you have set, the split second the grade changes from downhill to up again its back on the throttle. It does let the car slow to the set speed at that point, but its so strange to have the cruise control ever give the car gas when its above your set speed.

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obermd

· #9 · Jul 23, 2016

spacedout said:
The cruise control is amazing in this car. Even if you have gained speed down a hill well in excess off the MPH you have set, the split second the grade changes from downhill to up again its back on the throttle. It does let the car slow to the set speed at that point, but its so strange to have the cruise control ever give the car gas when its above your set speed.

Does the AT actually get back on the gas or is it just disengaging DFCO? I've watched my ECO MT using Metric and instant readouts and it appears mine just exits DFCO and idles the engine.

jblackburn

· #10 · Jul 23, 2016

obermd said:
Does the AT actually get back on the gas or is it just disengaging DFCO? I've watched my ECO MT using Metric and instant readouts and it appears mine just exits DFCO and idles the engine.

Mine definitely jumps back on the gas as you start heading uphill too, before it reaches the set point. Smart TBH.

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S-Fitz

· #11 · Jul 23, 2016

spacedout said:
The cruise control is amazing in this car. Even if you have gained speed down a hill well in excess off the MPH you have set, the split second the grade changes from downhill to up again its back on the throttle. It does let the car slow to the set speed at that point, but its so strange to have the cruise control ever give the car gas when its above your set speed.

I've had the same experience. On the transition from downhill to uphill, it will make a run at it before you reach the incline, almost as if the car can see what's in front of it. I frequently drove my Cruze through the Cascades on the west coast and do not recall the car ever hunting for gears. It will even let the speed drop about 10km/h before downshifting on steep hills, and when it did downshift, it would not try to hustle up 10k back to the set speed. It would creep back to the set speed after cresting the hill.

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Alex V.

· #12 · Jul 24, 2016

Mine's a manual, but I find the Cruze control

very refined for not being touted as "adaptive" or "smart". You don't feel it coast right down to the set speed and pour on the coals to stop deceleration.

...Unlike my '85 GMC with 454, Quadrajet, and cruise. Downhill you can hear the engine sucking against the throttle plates, and when it starts up that next hill and bottoms out to the set speed there's a gratifying surge of power (unless one considers the excess fuel being used) and a faint noise not unlike a leaf blower which one can only surmise is those huge secondaries at the mercy of the all-or-nothing, vacuum-canister cruise control.

dhpnet

· #13 · Jul 24, 2016

All cars with auto trans have the ability to manually shift the car into a lower gear. The difference was that older automatics only had 2 or 3 gears, so it was simple to shift from D to L2 or L1. The Cruze has 6 gears, so it requires a different method for manually down shifting.

The Cruze AT will not only stop you from making shifts in manual mode that could hurt the car, but it will also automatically downshift if your speed is too low. It can get a little confusing if you try to manually shift all the time because you have to constantly keep an eye on the DIC to see what gear it is in.

I think it would be nice if they added a way to leave the car in auto mode, but just tell the computer that you think it should be in a lower or higher gear. I frequently shift to M and then back to D in order to do this. The Cruze seems like it is always trying to get the lowest gear possible at the expense of drivability and power.

I may go back to a manual transmission for my next car.

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Kalpazan

· #14 · Jul 25, 2016

Idling engine is not recommended unless car is in a full stop. Transmission should be engaged all the time if car is moving (shifting is an exclusion of course). I doubt Chevy engineers would brake that rule on purpose.

obermd

· #15 · Jul 25, 2016

Kalpazan said:
Idling engine is not recommended unless car is in a full stop. Transmission should be engaged all the time if car is moving (shifting is an exclusion of course). I doubt Chevy engineers would brake that rule on purpose.

The Cruze MT doesn't mind idling. In fact, the ECU will idle the engine to the extend that no fuel is being provided to the engine. What you don't want to do is drive with the clutch part way down - either foot off the clutch or pedal to the floor.

Kalpazan

· #16 · Jul 25, 2016

I have drived MT all my life and I can tell you that while what you say is absolutely right you don't want to keep your clutch depressed for a very long time (sitting at red light for example). You may wear throw-out bearing way too fast like that. Also, uneccessary push and release of pedal wears clutch prematurely. So, avoid it if possible.

obermd

· #17 · Jul 25, 2016

Kalpazan said:
I have drived MT all my life and I can tell you that while what you say is absolutely right you don't want to keep your clutch depressed for a very long time (sitting at red light for example). You may wear throw-out bearing way too fast like that. Also, uneccessary push and release of pedal wears clutch prematurely. So, avoid it if possible.

True. The fastest way to burn a clutch is to ride it. The next fastest way is to push it in and use the friction pad/pressure place combo to slow the car down while you let the clutch out. The throw out bearing should be OK as long as the clutch is on the floor stop - this bearing is under far more stress at intermediate positions.

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