Engine Torque Request (Transmission Interfacing)

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augenblick
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Engine Torque Request (Transmission Interfacing)

Post by augenblick »

My understanding is that Rusefi doesn't operate on an engine torque model, and that the Bosch ME2.x systems do. I assume atleast a few other electronic transmission/engine combinations are similar. The 722.6 Controllers I'm working with send out a CAN message to ask the engine to back off torque during shifts. Currently, I'm driving around that by lifting off the throttle, but an automagic way of doing that would be more precise. What I am asking is:

a) is there already something in the feature set that would reduce torque/lift-off throttle/whatever based on CAN requests
b) if there is not, what's the least hacky way of going about doing it?
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AndreyB
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Re: Engine Torque Request (Transmission Interfacing)

Post by AndreyB »

Very limited telepathic abilities - please post logs & tunes where appropriate - http://rusefi.com/s/questions

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AndreyB
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Re: Engine Torque Request (Transmission Interfacing)

Post by AndreyB »

Longer answer: at the moment the idea is to use Lua for torque reduction. We have Lua callbacks to move throttle (close it) and adjust timing and induce spark skips if desired

Current thinking is that those three should get the job done? But someone would have to start and try and report back.
Very limited telepathic abilities - please post logs & tunes where appropriate - http://rusefi.com/s/questions

Always looking for C/C++/Java/PHP developers! Please help us see https://rusefi.com/s/howtocontribute
augenblick
Posts: 21
Joined: Fri Jan 15, 2021 10:48 pm

Re: Engine Torque Request (Transmission Interfacing)

Post by augenblick »

Short version is I'm testing this on two imperfect cars, and haven't found a good way to correlate the logs. However there are still some useful takeaways.

PnP is very convenient. Physically, NAG52 will work on any 722.6, but tuning is still a WIP. Ashcon is working on a new revision that will include hardware support for 96-99 shifters (~2000+ use CAN based shifters), we'll see how that goes soon; my arduino shifter converter works mostly fine, but is not super ergonomic, it's a bit less plug and play, especially if you don't have half the interior taken out like I do.

Tunability is also a WIP. Last time I looked at the code, the base map was hard coded, and self adapting. You can adjust the adaption coefficients, but you have to use a config utility Ashcon is working on; it doesn't hitch up to Tunerstudio, which would be useful in getting everything working through a common interface. This only really matters if I'm having someone else work on the transmission tune.

It's designed around more or less stock engine controls, so it communicates according to Mercedes standards. As I mentioned in my forum post, the ME uses torque model somewhere in its control scheme, and that's the context in which the TCM interacts with the ECM. Right now the NAG52 sends out a torque request frame, rusefi flat out ignores it, and the quality & speed of the shift depends largely on how I am operating the throttle. What this means in real world use is if I'm in a high rev or high load scenario, there's a chance it will delay or miss shifting; I'm mostly using +/- gear shift buttons to control shift timing. It will downshift fine on its own on the ratmobile, but upshifting I generally handle. Because the transmission in the CLK is so broken, I have to control downshifting, or there's a chance I'll end up in unknown gear hell.

Circling back, I think we have the tools (mentioned above) to accomplish torque reduction via CAN requests, tuning it is going to take some time, and I'm not sure how to make it behave parametrically so we're not hand tuning every situation. I'll try to dig into it once I finish swapping the transmission out on the CLK.
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