Active Rev Matching & CAGS & DOD

[Evolution1980]

I've never had to worry about CAGS, but I know it's one of the first things manual transmissions owners usually disable/defeat.

Any one care to venture a guess on how these two will play together? (Assuming CAGS is still there.)

I'm also curious to know how the cylinder (de)activation will factor in. I still call it "Displacement on Demand" ("DOD"). Is there any lag? What does it feel like, if anything? Is there some display that shows what cylinders & when they are active/inactive? I'm assuming direct injection significantly helps in this area.
Is it always the same cylinders, like the back two? Or is it random as a way to avoid uneven cylinder wear & contaminant deposits?

 

[LLC5]

I've never had to worry about CAGS, but I know it's one of the first things manual transmissions owners usually disable/defeat.

Any one care to venture a guess on how these two will play together? (Assuming CAGS is still there.)

I'm also curious to know how the cylinder (de)activation will factor in. I still call it "Displacement on Demand" ("DOD"). Is there any lag? What does it feel like, if anything? Is there some display that shows what cylinders & when they are active/inactive? I'm assuming direct injection significantly helps in this area.
Is it always the same cylinders, like the back two? Or is it random as a way to avoid uneven cylinder wear & contaminant deposits?

Rev matching and CAGS will not interfere with each other, CAGS is at low rpm and light load, and rev matching is at higher rpm's and greater engine loads.

DOD is not noticable when in active mode, no lag or noticable performance changes. Harmonic frequences do change however and, white noise is usually filter through the stereo speakers to cancel the sound differences. I have never seen a display of the cylinders being deactivated, manufacturers want it to be seamless and not noticeable at all. It is the same cylinders being deactivated, but I have never seen any mechanical problems associated with DOD.

 

[Evolution1980]

Since CAGS is effectively an EPA thing, I'm wondering if they've done away with it since the car now has DOD? Does it not effectively work to attain the same goal, that being less fuel consumption when it's not needed?

 

[LLC5]

Since CAGS is effectively an EPA thing, I'm wondering if they've done away with it since the car now has DOD? Does it not effectively work to attain the same goal, that being less fuel consumption when it's not needed?

It may be a thing of the past with direct injection and DOD. Direct injection will have the biggest effect on fuel economy and power since the compression ratio can be higher, DOD is only active during limited parameters and under light load conditions usually at cruising/freeway speeds so the actual mpg increase is minimal unless you are on a totally flat cruising speed road for quite some time. With CAFE numbers beginning to skyrocket, even a tenth of a mpg is critical for every manufacturer.

 

[Gorgon]

Since CAGS is effectively an EPA thing, I'm wondering if they've done away with it since the car now has DOD? Does it not effectively work to attain the same goal, that being less fuel consumption when it's not needed?

Has anyone heard of the manual Stingray gets around the Gas Guzzler tax like Vettes before? If this is truly a goal of the new car then it might incorporate CAGS as well as DOD and direct injection. I believe CAGS was introduced on the LT1 equipped, 6-speed C4. The new car has increased base power by 150hp so I have to think all three are likely to be present to meet CAFE numbers.

 

[Vettelt193]

Has anyone heard of the manual Stingray gets around the Gas Guzzler tax like Vettes before? If this is truly a goal of the new car then it might incorporate CAGS as well as DOD and direct injection. I believe CAGS was introduced on the LT1 equipped, 6-speed C4. The new car has increased base power by 150hp so I have to think all three are likely to be present to meet CAFE numbers.

My Dad's 1991 Convertible that he bought new had CAGS and, of course, was L98 powered. The salesman made no mention of it and my Dad was frustrated as hell with the car for the first few days because it would lock him out of gears randomly. Once he figured out the pattern he got around it for a bit and as soon as he saw the eliminator in Mid America it was ordered and installed. IMO it's a safety issue. No one wants to shift 1-4 because it's too big of a jump. When my cars had it enabled there was more than one time that I short shifted out of first then needed to get on it and was locked out of anything but 4th... and 4th has yugo like acceleration. The standard skip pattern for most vette drivers in 'cruise mode' is 1-3-5-6 or 1-2-4-6. With the 7 speed I imagine it will be 1-3-5-7.

One of the things I think they missed the mark on is the shift pattern. A starting position of 1st back would have been nice. Most of the time shifting around is between the other gears. Allowing the 2-3 shift to be up down would have been killer for the curvy roads.

 

[Evolution1980]

One of the things I think they missed the mark on is the shift pattern. A starting position of 1st back would have been nice. Most of the time shifting around is between the other gears. Allowing the 2-3 shift to be up down would have been killer for the curvy roads.

Wow, that's a very interesting and astute observation! *golf clap*
Since the car does 0-60 in 1st gear, it does seem to make more sense to have 2nd & 3rd inline with each other. Unless having 1-2 inline makes more sense for a 1/4 mile run (which it does). Or, I don't know for sure, but isn't 1-2 inline more 'standard' globally? Or do other manufactures with odd-numbered gears have 1st gear by itself?

 

[hzl6cm]

Porsche has 1st down and to the left (under reverse) and then 2nd and 3rd in line with each other. At least they did on the last Porsche I drove, a used 914 that I test drove in the early 80s. When I pulled up to the first stoplight I about pulled an "American Graffiti" move when I slipped the shifter in to reverse while waiting for the light to change. Fortunately I realized it before letting the clutch out. The salesman said the pattern was for real world driving when you were much more likely to be downshifting from 3rd to 2nd and back up again than you were from 2nd to 1st - which you mostly do when coming to a stop.

 

[1analguy]

...DOD is not noticable when in active mode, no lag or noticable performance changes. Harmonic frequences do change however and, white noise is usually filter through the stereo speakers to cancel the sound differences. I have never seen a display of the cylinders being deactivated, manufacturers want it to be seamless and not noticeable at all. It is the same cylinders being deactivated, but I have never seen any mechanical problems associated with DOD.

Chrysler has had DOD on the 5.7L HEMI since, I believe, 2009. They'll only employ it on cars equipped with automatic trasmissions, as they experienced insurmountable NVH issues when they tried to use it with manual transmissions. My brother owns an '09 300C and it does indeed have a display in the instrument cluster that tells you when it operating is in 4 cylinder mode. Also, they are starting to see premature timing chain failures on HEMIs equipped with DOD. Just saying...

 

[Evolution1980]

I've never had to worry about CAGS, but I know it's one of the first things manual transmissions owners usually disable/defeat.

Any one care to venture a guess on how these two will play together? (Assuming CAGS is still there.)

I'm also curious to know how the cylinder (de)activation will factor in. I still call it "Displacement on Demand" ("DOD"). Is there any lag? What does it feel like, if anything? Is there some display that shows what cylinders & when they are active/inactive? I'm assuming direct injection significantly helps in this area.
Is it always the same cylinders, like the back two? Or is it random as a way to avoid uneven cylinder wear & contaminant deposits?

Hey! Resurrecting my own thread!!! That's a change...
So my buddy got a 2015 with the 7-speed manual.

CAGS is still there. Sucks. Gotta find a defeat mod for it.

DOD kicks in when you're driving in ECO mode. It's nearly imperceptible unless you are trying to notice it. Although with the exhaust flap operation set in a certain mode, you'll know when you come out of 4-banger mode because it goes from a silent ride to a mild drone.

Rev-matching is probably the most awesome part of that transmission! It's nearly impossible to botch a downshift.

 

[LLC5]

Chrysler has had DOD on the 5.7L HEMI since, I believe, 2009. They'll only employ it on cars equipped with automatic trasmissions, as they experienced insurmountable NVH issues when they tried to use it with manual transmissions. My brother owns an '09 300C and it does indeed have a display in the instrument cluster that tells you when it operating is in 4 cylinder mode. Also, they are starting to see premature timing chain failures on HEMIs equipped with DOD. Just saying...

This is an old thread but an update is in order. I'll have to take back what I said about the mechanical issues, we are seeing piston ring sealing issues (plug fouling and oil usage) on the cylinders that are being disabled.

Good point on the manual transmissions, ours are only on torque converter automatics and you cannot tell the difference when DOD is activated. A visual display would let the owner know that they are getting what they paid for.......

 

[Hib Halverson]

Since CAGS is effectively an EPA thing, I'm wondering if they've done away with it since the car now has DOD? Does it not effectively work to attain the same goal, that being less fuel consumption when it's not needed?

I know this is an older thread but...

Computer Aided Gear Selection or "CAGS" is not an "EPA thing". The original reason for developing CAGS was the Fed's and some States' pass-by noise standards. In a nutshell, the pass-by noise test required starting off in first gear, then shifting to the next highest gear, then passing by the microphones at wide-open-throttle. GM was able to convince the Feds that, if it blocked the 1-2 shift and forced a 1-4 shift, that would be the "next highest gear". Obviously, if you go by the microphones at WOT in 4th the car will be a lot less louder than if you go by the mics at WOT in second. It was only later, after CAGS was developed and EPA mileage testing was done, that GM found that in certain drive cycles, CAGS made a slight improvement in fuel economy.

As for "Active Fuel Management" AFM, "Displacement on Demand" (DOD) or "cylinder deac", as GM engineers say, on a V8, it deactivates the same four cylinders by disabling their valve lifters. The system is electro-hydraulic and it is nearly impossible to feel, very difficult to hear, and changes states almost instantaneously. Cylinder deac causes no significant problems with deposits, contamination or "uneven wear".

 

[korvettekarl]

There is one indicator on the main display if you have it in INFO mode and INSTANT MILEAGE. I'm going from memory here but,it seems like there is V8 indicator that is orange and a V4 that is green when in DOD. I don't use ECO mode very often. Still gets 18-21 mpg daily driving around Vegas. I did have one instance of DOD going bonkers on me this summer. It was around 118 degrees and I was on the 215 Beltway, Friday rus hour traffic in ECO mode. All of a sudden the car goes into REDUCED ENGINE POWER. I had to floor the accelerator just to keep up with 60 MPH traffic. Found the first off ramp and stall it at the light because of the REDUCED ENGINE POWER. Managed to get it home and parked in the garage. Sweating all night, I get up to take it to the dealer. Fire the Stingray up and, all is well. My relief woke the wife up (large yell, I hate taking a car to the dealer. I would rather lick a dirty toilet bowl clean with my tongue). Apparently the heat and maybe some bad gas caused a Twilight Zone PCM incident. It hasn't done it since. I also haven't used ECO mode since.

 

[LLC5]

There is one indicator on the main display if you have it in INFO mode and INSTANT MILEAGE. I'm going from memory here but,it seems like there is V8 indicator that is orange and a V4 that is green when in DOD. I don't use ECO mode very often. Still gets 18-21 mpg daily driving around Vegas. I did have one instance of DOD going bonkers on me this summer. It was around 118 degrees and I was on the 215 Beltway, Friday rus hour traffic in ECO mode. All of a sudden the car goes into REDUCED ENGINE POWER. I had to floor the accelerator just to keep up with 60 MPH traffic. Found the first off ramp and stall it at the light because of the REDUCED ENGINE POWER. Managed to get it home and parked in the garage. Sweating all night, I get up to take it to the dealer. Fire the Stingray up and, all is well. My relief woke the wife up (large yell, I hate taking a car to the dealer. I would rather lick a dirty toilet bowl clean with my tongue). Apparently the heat and maybe some bad gas caused a Twilight Zone PCM incident. It hasn't done it since. I also haven't used ECO mode since.

Something happened that was not good if you recieved the REDUCED ENGINE POWER indicator. There should be a history code in the PCM and it would be a good idea to scan it and see what that code is.

 

[korvettekarl]

Thanks. Next time I go to the dealer I will inform them. I have my eyes on a 16 Shark Grey Z51 I might trade her on.