3P's TCCS Disassembly/Analysis

3p141592654

3p141592654

90T
Oct 11, 2005
3,815
13
38
Thousand Oaks, CA
This thread is getting so big its hard to find stuff, but see here for timing computation. http://www.supramania.com/forums/sh...bly-Analysis&p=1712465&viewfull=1#post1712465

There is a hot coolant table that retards the timing for coolant above 95C, peaking out at 105C (max correction is 4 deg retarded).
Click to expand...
So, on a hot day you will see some impact to timing.

Another thing to consider is that the air intake temp goes through the roof on a hot day because the AFM is beside the exhaust manifold and gets heat soaked. Its not unusual to see intake temps above 60C on a hot day after 30 minutes of driving, even though the air intake for the factory filter is in a cool place. That will also reduce power.
 
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73tlc3fe

New Member
Aug 3, 2011
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Southport, NC
I read this thread with interest. I have a 3FE that uses a similar Toyota TCCS ECU. I am curious if there are any reader boards available so I can dump the code from my ECU.
 
3p141592654

3p141592654

90T
Oct 11, 2005
3,815
13
38
Thousand Oaks, CA
I do not have any more reader boards available. The design files are available on Assembla for this board, and you can have dorkbots make it for you fairly cheaply. Alternatively, you can desolder the MCU chip and send it to me and I can read out the code for you.
 
Rollus

Rollus

New Member
Jun 2, 2011
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Paris, France
Hi Mr Pi,


I found the post below explaining the switch from open to closed loop at cold start, and another one during hot start.
3p141592654;1899674 said:
Its hard to discuss the fuel calcs without the overall picture of the ECU engine model, and I will write up a more detailed explanation of the fuel calcs soon.

After a cold start the ox sensor reads lean (0V) and won't do anything until it heats up to about 300C. During this time the ECU uses 4 cold start trim counters to add fuel to the basic model. These counters are set to specific values (from internal maps) at startup depending on coolant temp, and rapidly count down with time and temperature until they reach 0, at which point cold start enrichment is over. The longest one lasts until a coolant temp of 60C is reached, the others are faster. They also drop with time.

Now, the switch from open loop to closed loop happens when the ECU sees the O2 sensor switch from lean to rich. For this morning, which was 7C here in So Cal, it took 2 minutes before the ECU switched to closed loop. At that point the mixture will be forced to stoichiometric unless the ECU is forced open loop for other reasons (like high load). So, after cold startup, you will be running open loop, but the ECU is calibrated to get the fuel pretty close on startup to help with lightoff emissions.

Vf will read 0V when open loop. You should not see 2.5V right after a cold start.

You can see a datalog of my cold start this morning. Warning: this will waste 2 min of your life. Note that the purple line (short term fuel trim) stays at 100% for most of the datalog because fuel control is open loop after a cold start. At about 1:56 it starts to move indicating closed loop fuel control has started. Even though it in closed loop, the fuel enrichment continues to help the model stay close to the actual required values.

[video=youtube;cu6TJqXtBV4]http://www.youtube.com/watch?v=cu6TJqXtBV4&feature=youtu.be[/video]
Click to expand...


I'd like to know how does the TCCS switch from closed to open loop during load.

I'm dreaming about this switch been only because of the narrowband lambda, and maybe that with a wideband + some narrowband emulation (using a µC board with a lookup table), we can keep the TCCS in closed loop.

Even if I'm trully dreaming, please explain (if you know, and I hope you know) the closed/open loop switch when driving at the operating temps, etc.. according to throttle position or maf, whatever make this switch happen.

Regards,

Reynald
 
3p141592654

3p141592654

90T
Oct 11, 2005
3,815
13
38
Thousand Oaks, CA
Actually its pretty straightforward. There is a map versus rpm that is compared against the current engine load. If the load is > than the map value it goes open loop:
2800 rpm 48%
7600 rpm 0 %

So for rpm <= 2800, if load exceed 48% it goes open loop. As the rpm increases, the threshold linearly drops, so at 5200 rpm the threshold is 22%, and so on. You can see that the faster the engine is spinning, the sooner it will drop into open loop.

There is also a throttle check, and if the the throttle is greater than a certain amount (48% to be exact) then it will go open loop regardless of rpm.

There are a bunch of other special cases that come into play, including rpm < 300, right after startup with no O2 sensor cross counts detected, derivative of the load variable, and some extreme odd behavior of the short term fuel trim variable, but those are just covering certain special cases.
 
Rollus

Rollus

New Member
Jun 2, 2011
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0
Paris, France
Thanks for your answer. So we cannot force TCCS to run closed loop.

So if we want closed loop, we need to have a piggyback allowing this, and to think about the reliable way taking into consideration the learned TCCS open loop table...
 
3p141592654

3p141592654

90T
Oct 11, 2005
3,815
13
38
Thousand Oaks, CA
No, if you want to stay closed loop all the time, you need to rewrite the software to do so. A piggyback would never be able to make this work. You don't want 14.7 AFR at WOT anyway, and that's all this ECU will give you closed loop.

It could be done with our daughterboard and a lot of software development and a modern wideband O2 sensor in place of the 3 wire sensor. I don't see the point though. The manufacturers do it on their cars rolling off the Lots today to meet emissions and optimize fuel economy.
 
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Rollus

Rollus

New Member
Jun 2, 2011
593
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Paris, France
Great.

I'd like to buy a prototype please :-D

I'm used to microcontroller development, testing, debugging, and soldering..

Envoyé depuis mon GT-N7100 avec Tapatalk
 
M

mjwillia

New Member
May 13, 2013
2
0
0
Perth
Hey guys,
I've had mk3's for going on 15 years now, and have a few friends with them also.

At the moment I'm rebuilding mine (7mgte with a gt42/94) and I'd like to become involved with this project.

I'm not an expert with this technology but I have extensive experience with electronics, tuning aftermarket ecu's (haltech, emanage) and delco 808's.

I have a couple of later type 7m ecu's (the one with the 2 boards in it).

Whats required to get going / where's the project at?

Thanks,

Matt
 
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