ECUTek Think Tank

[Kodename47]

Right, here's my latest query. What's the tie in with all the torque request tables. I've noticed that the requested values dip at around 4k. Is this likely to make much difference? Have people edited them and what for and if so, how? I noticed that one of my previous NA tunes has the WOT 2D table edited.


I've attached a pic of the stock ROM for reference.

[Kodename47]

Also, I'll add on, what is the difference between the 2 acc. to torque and the 2 calculated torque tables.


From what I can tell:
(WOT Tq / Acc. Pedal Desired) = x axis of desired tq to throttle angle


So to get constant WOT I'd assume you want the tables to match to equal 1 on the desired throttle angle.

[Kodename47]

Ok, I found @mad_sb 's post: Link Explains the DBW system, but still a bit in the dark over the calculated torque tables.

[arghx7]

Since this is a broad-open ended question, here's what I can say. This is based on what's been publicly posted about how Subarus drive by wire and engine control systems work.

It could be called a pedal-follower system. @mad_sb 's thread explained it pretty thoroughly, including this post:

Originally Posted by Shankenstein

So to put this in geek-speak:
T_EST = f(N, LOAD) using either map "A" or "B"
T_WOT = f(N)
T_REQ = f(APP, N) using either map "Normal" or "Sport"

T_RATIO = T_REQ / T_WOT

TA_REQ = f(T_RATIO, N)
TA_CUR = current throttle angle

TA_DELTA = TA_REQ - TA_CUR
TA_TARGET= filter(TA_CUR, TA_DELTA, K) where K is the adaptive filter gain

Basically a map(s) requests torque based on pedal position, another map looks up estimated torque based on speed and load, another map looks up throttle position needed to get current torque to that requested value.

Originally Posted by Kodename47

I've noticed that the requested values dip at around 4k.

So here's what most likely happened. Somebody at Subaru or Toyota ran an engine dyno at a bunch of steady-state speed & load points. So at 4000rpm 1.00 g/rev they ran the engine for maybe a minute. All the spark timing, AVCS, etc were all adjusted at each point. The dyno measured the engine torque. It was all spit out into a big Excel-readable file by the dyno control system.

Then they loaded the data from the file either directly into the maps for the ECU, or into some Matlab tool or Excel macro which processed it and spit out the values. There wasn't necessarily a ton of thought put into the numbers in the table. Some guy followed some procedure, that's all. The torque curve of the engine was most likely established on the dyno at each individual point before those maps were ever made.

The FA20 doesn't use an actual model of engine torque, not from what's been seen so far. It's just those look-up tables, which as I said came right from an engine dyno into the maps with maybe some tweaks on top of that.

[jamesm]

according to ecutek, the wide open throttle torque threshold map should be shaped like your torque curve. so i made mine that way, and it works. that's about all i know on this topic lol.

[Shankenstein]

Originally Posted by arghx7

So here's what most likely happened. Somebody at Subaru or Toyota ran an engine dyno at a bunch of steady-state speed & load points. So at 4000rpm 1.00 g/rev they ran the engine for maybe a minute. All the spark timing, AVCS, etc were all adjusted at each point. The dyno measured the engine torque. It was all spit out into a big Excel-readable file by the dyno control system.

Then they loaded the data from the file either directly into the maps for the ECU, or into some Matlab tool or Excel macro which processed it and spit out the values. There wasn't necessarily a ton of thought put into the numbers in the table. Some guy followed some procedure, that's all. The torque curve of the engine was most likely established on the dyno at each individual point before those maps were ever made.

The FA20 doesn't use an actual model of engine torque, not from what's been seen so far. It's just those look-up tables, which as I said came right from an engine dyno into the maps with maybe some tweaks on top of that.

This guy knows what's up. Listen to him.

Tuning starts in the dyno lab. Steady-state testing is great for developing the base tune and working the bugs out of new functions/technology/sensors/you name it.

Once the software design has been validated conceptually, you move on to a production-level validation. Most of the manufacturers will send out fleets of company vehicles, driven by underpaid interns, co-ops, and engineers. These cars usually have a few non-production sensors and fancy data logging systems. Everybody drives like normal, and they get an accurate distribution of people's driving habits... and the car's response them. Send them into all sorts of weather, location, driving styles, etc.

Due to the adaptive variables and correction factors in modern software, it's pretty likely that the car will settle into a semi-usable tune without alot of fiddling. Inefficient and unresponsive, though. The fun is analyzing "how wrong" your open-loop controls were, and determining the root cause. Seeing how far you can push the system before it acts up in altitude, snow, etc.

Alot of modern datalogging systems allow you to update the engine variables in real-time. Most of the legwork is done via test-n-flash method for now.

Side Note: Model-based tuning is the way of the future... but it's a tough sell to management. Even with unlimited computing power, they'll still want to use "streamlined" versions that barely resemble the underlying physics. It's trickling into most code, but I'm not too satisfied with the implementations I've seen thusfar.

[Turdinator]

First of all I don't have Ecutek or a tune of any sort on my car as yet but I had hoped to get one some time this year. I am fairly sure with ecuteks custom maps I could hijack an output and control a bimodular exhaust setup. What I want to know is could I vary that map with something like what VSC mode the car was in? Ie with all the nannies on its more quiet than with VSC sport which is in turn quieter than when the nannies are off.

[Circuit Motorsports]

Currently you can enable a map based on traction control being disabled. The ability to detect VSC mode is not currently implemented.

Let me know if you have any questions. Feel free to PM for tuning details.

- Bob

[nelsmar]

Originally Posted by Turdinator

First of all I don't have Ecutek or a tune of any sort on my car as yet but I had hoped to get one some time this year. I am fairly sure with ecuteks custom maps I could hijack an output and control a bimodular exhaust setup. What I want to know is could I vary that map with something like what VSC mode the car was in? Ie with all the nannies on its more quiet than with VSC sport which is in turn quieter than when the nannies are off.

We are able to log the input but using it as a table input is not added at this time. I am hoping they start adding more and more to these tables though!

[jamesm]

Originally Posted by nelsmar

We are able to log the input but using it as a table input is not added at this time. I am hoping they start adding more and more to these tables though!

you could still do it, with some clever manipulation of the custom maps.

custom map foo active when the traction control is off; output all 1's
custom map bar active on threshold of map foo output, or just use map foo output as an input to map bar

[nelsmar]

Originally Posted by jamesm

you could still do it, with some clever manipulation of the custom maps.

custom map foo active when the traction control is off; output all 1's
custom map bar active on threshold of map foo output, or just use map foo output as an input to map bar

thats traction off, not vsc sport though

[jamesm]

yeah actually that wouldn't work unless you dedicated a whole map switch mode to it. fail lol.

[nelsmar]

Originally Posted by jamesm

yeah actually that wouldn't work unless you dedicated a whole map switch mode to it. fail lol.

Yeah... @EcuTek add more inputs for custom maps for us!!! I'll bake you cookies!

[Xero-Limit]

Watch your throttle angle on datalogs when you alter these. If you go the wrong direction, it will think that it is making more torque than requested, and cut back throttle despite 100% pedal.

Originally Posted by Kodename47

Right, here's my latest query. What's the tie in with all the torque request tables. I've noticed that the requested values dip at around 4k. Is this likely to make much difference? Have people edited them and what for and if so, how? I noticed that one of my previous NA tunes has the WOT 2D table edited.


I've attached a pic of the stock ROM for reference.