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Can AFM be turned off by putting the car in manual mode? How long before it goes back to auto mode?
Assuming I purchase a Z51 with magnetic ride, can I disable AFM by putting it in PTM?
Tadge answered:
We know some customers are not fans of AFM (Active Fuel Management, otherwise known as cylinder de-activation). They worry it will sound bad, or feel bad as it transitions in and out of V4 mode, or just don't like that the engine doesn't always run on all cylinders. Manufacturers around the world are being put under tremendous pressure to reduce fuel consumption and greenhouse gases. As a result, you see a massive move to electrification, hybridization and small displacement charged engines. General Motors is fully embracing the initiative and has a stated goal to get to a zero emissions future.
So how does Corvette fit into this picture? Even before global greenhouse gas concerns became mainstream, Corvette prided itself on efficient operation. After all, low mass, low drag and efficient engines make for a better sports car. There are a lot of ways to get fuel efficiency and some of them negatively impact the driving experience. Our manual transmission skip-shift we had for years was not a customer favorite, but it helped economy and kept us away from gas-guzzler taxes. The bottom line is that we have to make choices that balance the owner's experience (including operating cost) and our impact on the planet.
Our AFM system is very effective on the small block V8. It lets us close the valves on the de-activated cylinders so the cylinders act as air springs. When the engine rotates we get energy back as the compressed air in the cylinder expands. Other manufacturers just stop fueling the de-activated cylinders and so don't get much fuel savings. The reason 4-cylinder operation is more efficient is that the active cylinders are worked harder with a greater throttle opening. That's like taking a restrictor out of the system saving pumping losses. On Corvette, AFM saves more fuel than start/stop, a feature becoming very prevalent in the marketplace. For many cars, start/stop is a great choice because it is almost transparent to the occupants. Not so on a Corvette. Our engine has a lot of character, so when it stops running it is very noticeable. We have received a lot of very strong input from customers that they would not like it.
One of the innovations on the 2020 Stingray is the integration of AFM with a DCT. We a quite proud of how seamless we've been able to make it. We believe we are getting the efficiency benefit with virtually no compromise to the driving experience. Numerous drive impression articles have been written and I do not remember reading any negative comments about it. Bottom line is that we must balance conflicting demands and make smart choices so we can continue to offer the driving pleasure of a naturally aspirated V8 engine.
So now to the heart of your question. Yes, when you are in manual mode the engine stays in V8. That is true either by hitting the "M" button or by entering "temporary tap" by pulling one of the paddles. Temporary tap will revert to "Drive" after about 5 seconds if you don't request an additional shift in that time. AFM is also de-activated in "Track" mode. Since PTM is only available in Track mode, the answer is yes to that one too. If you are in PTM, it will be V8 only. New for 2020 is the "Z" mode which will come from the factory set up as an extra sporty mode including shift schedules pulled from the "Track" mode, so that will be V8 only. Of course, you can customize "Z" mode any way you want, so if you elect another shift pattern, AFM will return.
Another if you can't dazzle them with brilliance moment from TJ and friends at GM World. Only the last paragraph was necessary ..............
For you, I must assume already knew how the C8's 4-8 cyl could be deactivated!
I can also assume you are not interested in or purchasing a C8, based on you reply!
I myself knew that GM has used 4-8 system for a number of years in various models, and that for some owners it was irritating feel as it went back and forth between them, especially in the early years, and they had it turned off, or purchased device to deactivate it.
There may have been a way to deactivate system without paying to have it done, or purchasing a tuning device to do it.
But for someone like me who hasn't purchased a new GM vehicle since 1973, the reply covered the why GM used 4-8 Vs Stop-Start method, which I can tell you created a starter failure problem for automakers that used it to help meet Federal emission standards, because Manufactures that did it, did not take into account that the starters they used Lifespan was not designed to hold up to the number of starts it was subjected to in even a 2 yr time-frame, so I'll assume you are brilliant enough to understand what happened with owners opinion an with resale value of those cars.
Rather than just saying, as you said, "Yes" and left it at that, the reply given, provided all the ways, that the 4-8 system could be deactivated, if you wanted to bypass the 4-8 cyl system.
For me at least, an I suspect others, as I'm sure, none of have ever owned or driven a GM vehicle with a DCT transmission, which I'm sure based on you reply, have or have read in an Owners Manual, or maybe somewhere else, the ways it could be done.
If so, your only "reply" needed was a "Big YES". But what about those like me?
Couple of OLD sayings, " Ignorance can be Cured, Stupidity is Terminal". "Never argue with an Idiot, they will drag you down to their level and Beat you to death with their vast Experience."
My ignorance on subject was cured by the Reply provided.
Now with my reply, to yours, prove which on of us has the most experience at dragging the other one down to our level of "Stupidity"....?
Problem for me now is, have I let you drag me down to your level with your Vast Experience on Subject by replying.... or will my "Stupidity" for replying, let me drag you down to my Level of Experience at Baiting?
Last edited by Poorhousenext; 11-15-2019 at 12:06 PM.
Another if you can't dazzle them with brilliance moment from TJ and friends at GM World. Only the last paragraph was necessary ..............
Please keep your toxic replies in the other sections of the Corvette Forum. If you don't appreciate the extra work put into this answer by Tadge, you're free to seek info elsewhere.
I really enjoy the background and context that Tadge and his team include in the responses. I believe they are as passionate about the Corvette as the owners and hopefully they continue to see the value in connecting with the customers through efforts like this. Thanks again, Corvette Team!
Tadge should have answered the question first. The BS excuse should have been after the answer. Why didn't Tadge include his comment from a few years ago about the unequal pulsations coming from the engine with the AFM activated and the possible consequence of the uneven loading of the torque convertor and transmission input shaft?
Really? The whole thing took maybe 5 minutes to read, what’s the rush? I’m just thankful that he takes the time to explain the thinking behind the action.
Please keep your toxic replies in the other sections of the Corvette Forum. If you don't appreciate the extra work put into this answer by Tadge, you're free to seek info elsewhere.
Most forums have posters who jump in on every post to increase their POST NUMBERS. They seem to think it gives them a place of importance. MikeyTX's 26,697 posts appears in that category.
Tadge should have answered the question first. The BS excuse should have been after the answer. Why didn't Tadge include his comment from a few years ago about the unequal pulsations coming from the engine with the AFM activated and the possible consequence of the uneven loading of the torque convertor and transmission input shaft?
Why should Tadge include comment from a few years ago that's concerned "UNEVENLOADING OF TORQUE CONVERTER and TRANSMISSION INPUT SHAFT, on a question asked about AFM in conjunction with GM's new Dual Clutch Transmission?
From what I've read and heard about the Dual Clutch transmission, it doesn't use a Torque Converter to transfer power from the engine to the Transmission.
I'll assume you understand how a Torque converter works, vs how a Clutch and Pressure Plate works.
If you understand that, then you should understand that your question about, "Why didn't Tadge include his comment from a few years ago about the unequal pulsations coming from the engine with the AFM activated and the possible consequence of the uneven loading of the torque convertor and transmission input shaft?", is not relevant to this Thread!
Last edited by Poorhousenext; 11-21-2019 at 09:07 AM.
I completely understand how the Government dictated to the Automobile Manufacturers what they had to do to increase fuel economy.... CAFE for short....Hence the AFM. At least in the Corvette you can disable it by going into the Manual Mode....And with Rev-Matching with the Auto Tranny and the paddles it is almost like shifting with a manual. After my Tranny Flush with the new fluid I ALWAYS use the paddles and I really and truly haven't noticed any difference in gas mileage....
From what I've read and heard about the Direct Clutch transmission, it doesn't use a Torque Converter to transfer power from the engine to the Transmission.
Really? The whole thing took maybe 5 minutes to read, what’s the rush? I’m just thankful that he takes the time to explain the thinking behind the action.
not even that, took 30 seconds to skim through and get to the meat and potatoes. This site has some great knowledge and I’m really thankful for that, but it truly is the most negative bitchy forum I have been to in a long time.
This explanation is/was informative and likely necessary due to Govt. fuel mileage requirements. GM can't disable it so has to promote it as best it can. Personally, I think I would prefer the stop/start technology over AFM. Initially I was very skeptical of it, but after driving a BMW Diesel in Ireland a few years back, it really wasn't that irritating. It could also be defeated with a blip of the throttle as we were coming to a stop.
My experiences with AFM haven't been good. Both my C7 A8's have had T/C issues due to AFM. My 15' had T/C replaced and still had problems that required flushing. My son in his G8 GT had the AFM system fail, fortunately a few weeks before the warranty ran out. That car had AFM turned off via a second tuned ECM early in it's life.
I like the idea of saving fuel when traveling. However, if the pulsing issues with T/C are noticeable and aggravating, there needs to be a way to turn it off on A8 models in Eco or Touring modes, WITHOUT having to buy a Range. (which I have in both C7s now). Normally I would have just had a mild tune installed with my HP Tuners Pro, but still want warranty in case the A8 and T/C have more issues.
11-14-2019, 04:18 PM
[ANSWERED] Will the C8 be running in AFM mode by default?
