Mercedes-Benz 722.6 (NAG1) Automatic Transmission

A forum for discussing applications and implementations of the MegaShift transmission controller code for the GPIO from B&G. This can control up to 8-speeds and 6 shift solenoids (plus a 16x9 table for controlling a PWM line pressure valve). It has manual and fully automatic modes (16x9 load x speed table), with under and over rev-limit protection, and full data logging of all inputs and outputs (among many other abilities). A TransStim to test your completed board is also available.
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: Mercedes-Benz 722.6 (NAG1) Automatic Transmission

Post by Bernard Fife »

Vesku,

Someone has sent me a file on the NAG1. The basic shift logic apparently looks like this:
NAG1 (722.6) shift logic
NAG1 (722.6) shift logic
NAG1_shift_logic.jpg (140.19 KiB) Viewed 17820 times
The current code does not have the ability to 'pulse once' or 'toggle' the outputs. However, we do intend to support this trans if at all possible (it looks straightforward at first glance), and I certainly hope we can add that capability to a future code version fairly soon. The CAN shifter likely is a problem, but it may be possible to work around that (1996-1999 were not CAN bus enabled, apparently).

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: Mercedes-Benz 722.6 (NAG1) Automatic Transmission

Post by Bernard Fife »

After thinking about this, the 5.00X+ codes could be used with the 'clutch outputs'. Clutch outputs can be set as active (with user PWM settings) or inactive for the duration of a shift, then they turn off. When outputs are used as clutch outputs, they have two timing elements: a fixed line pressure delay, plus a load dependent shift completion delay. So those delays could be used to adjust the duration of the shift signal as required by the NAG trans.

There is a show-stopper in the code at the moment, though. All current codes determine the current gear by polling the output states. Since all the outputs would all be off after the shift period, the controller would not know what gear it was in after a shift was done.

However, I can easily implement a 'NAG mode', in which the controller would assume the current gear is the same as the last commanded gear. With that and the clutch outputs, I think we are within reach of NAG transmission control (other minor adjustments may be needed, such as for the allowable duration of the delays, etc.).

I will work on this for the next beta release code.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
johnboy426
Posts: 9
Joined: Fri Jul 23, 2010 5:23 pm

Re: Mercedes-Benz 722.6 (NAG1) Automatic Transmission

Post by johnboy426 »

Lance wrote:After thinking about this, the 5.00X+ codes could be used with the 'clutch outputs'. Clutch outputs can be set as active (with user PWM settings) or inactive for the duration of a shift, then they turn off. When outputs are used as clutch outputs, they have two timing elements: a fixed line pressure delay, plus a load dependent shift completion delay. So those delays could be used to adjust the duration of the shift signal as required by the NAG trans.

There is a show-stopper in the code at the moment, though. All current codes determine the current gear by polling the output states. Since all the outputs would all be off after the shift period, the controller would not know what gear it was in after a shift was done.

However, I can easily implement a 'NAG mode', in which the controller would assume the current gear is the same as the last commanded gear. With that and the clutch outputs, I think we are within reach of NAG transmission control (other minor adjustments may be needed, such as for the allowable duration of the delays, etc.).

I will work on this for the next beta release code.

Lance.

This is great news! The factory controller "knows" what current gear is by monitoring the input/output speed sensors and an output (some are a direct output sensor while others are vehicle speed via CAN BUS i.e. wheel speed). Any speed error outside a certain percentage is seen as a ratio error and the transmission enters limp in mode turning off power to all solenoids which defaults the transmission to the current gear. Is there a way to have the code poll the input speed sensors and a wheel speed sensor(or some other type of speed) instead of the output states to make the 'NAG mode' possible?
johnboy426
Posts: 9
Joined: Fri Jul 23, 2010 5:23 pm

Re: Mercedes-Benz 722.6 (NAG1) Automatic Transmission

Post by johnboy426 »

After reading the discussion again, I realized there is more than one gearset for the NAG1. The first post lists:
1st Gear 3.93
2nd Gear 2.41
3rd Gear 1.49
4th Gear 1.00
5th Gear 0.83
Reverse Gear 1 -3.10
Reverse Gear 2 -1.90

Chrysler service information lists:
1st Gear 3.59
2nd Gear 2.19
3rd Gear 1.41
4th Gear 1.00
5th Gear .83
Reverse Gear 3.16
Kma4444
Posts: 2
Joined: Sat Nov 29, 2014 1:04 pm

Re: Mercedes-Benz 722.6 (NAG1) Automatic Transmission

Post by Kma4444 »

Hello all, I am new here and am wanting to use a NAG1 with a stand alone controller. Wonder if there has been any success in making one of these work.

Thanks a lot
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: Mercedes-Benz 722.6 (NAG1) Automatic Transmission

Post by Bernard Fife »

Kma4444,

We are working on the NAG mode for MShift right now. There is a fair bit of work to do, but the basic shifting code is done. I hope we will have something for people to try before too long (hopefully within several weeks if all goes well).

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
Kma4444
Posts: 2
Joined: Sat Nov 29, 2014 1:04 pm

Re: Mercedes-Benz 722.6 (NAG1) Automatic Transmission

Post by Kma4444 »

Fingers crossed that you have good luck with getting it up and running. I am to the stage of installing the NAG in my vehicle and would love to use this controller.

Thanks
Kevin
anthonyh
Posts: 1
Joined: Mon Dec 08, 2014 11:10 pm

Re: Mercedes-Benz 722.6 (NAG1) Automatic Transmission

Post by anthonyh »

Fingers crossed too, I'd love to use the 722.6 behind my v12 M120.
Mclain
Posts: 1
Joined: Thu Feb 19, 2015 3:10 am

Re: Mercedes-Benz 722.6 (NAG1) Automatic Transmission

Post by Mclain »

Any news about this little charm?

Or is it possible to get a beta for testing?
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: Mercedes-Benz 722.6 (NAG1) Automatic Transmission

Post by Bernard Fife »

Mclain,

The best place to find out how the code is progressing is in this thread: viewtopic.php?f=4&t=240&p=5051#p5051 At the moment we are waiting for feedback from bench testing with a NAG trans. So things are progressing quietly.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
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