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Discussion Starter · #1 ·
This is the stock volumetric efficiency and ignition timing tables from the UK gen3 ECU tuned for 95RON/ 91 US octane.

 

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Discussion Starter · #2 ·
This is the comparison between JDM and UK ign timing stock, courtesy of JonS in the UK who designed the ToyoTune boards that allows me to tune the stock ECU.

 

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Discussion Starter · #4 ·
I do know not yet, neither does Jon. I should mention that that is the base ignition timing. There are other modifier tables within the the code. The code is written in assembler so not super easy to figure out for the layman. I'm trying to learn enough to figure more out.. If there are any coders/tuners out there that might be able to help, please reach out to me.

The base ignition timing is used in conjunction with VE, manifold pressure, RPM, and coolant temperature to decide on final timing. There's also 3 (iirc, I'm not at home) steps [of severity] of knock retard. And if everything is OK (>4kRPM, >some manifold pressure, coolant temp >141F/61C) there's some code that adds another "26" timing to cylinders 1-3, and 0 timing to cyl4. This seems to jive with the idea that cylinders 3/4 are the first to blow up due to hotter coolant on that side of the block. No timing will be added to any cylinder if all of those conditions are not met.
 

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That's very interesting! certainly the first I've heard where timing if different between the cylinders. I assume fuelling is static across all 4 cylinders?
 

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Discussion Starter · #6 ·
I'm not sure. The 3SGTE does have sequential injection so it might have cylinder specific fueling conditions. The gen3 ECU is a dual CPU system,

Here's the tables that are defined so far for the CPU that seems to do most of the fueling calculations:
http://i.imgur.com/8yok2XR.png

And for the other CPU, that has VE and ignition tables:
http://i.imgur.com/mDWdYwN.png

I toyed with the numbers in extra ignition advance, normally it's only 26 on the second row- which is if all necessary conditions are met. My engine has been modified from stock.
 

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Discussion Starter · #7 · (Edited)
Jon told me this today:

In the ECU code there's two fixed timing values that are referenced in the code.

86 - equates to 5 deg BTDC for cranking
128 - equates to 10 deg BTDC for diagnostic mode

The VE table is not % based, it is on a scale of 0-255

I got IDA working so I can see the raw code before it is built in to a binary file to flash to the chip that holds the code... Indeed, it definitely is going to take a lot of time to understand what Toyota did. http://i.imgur.com/1cCfTic.png

JDM ECU data:

Timing CPU tables:
http://i.imgur.com/d9LHOVB.png

Fueling CPU tables:
http://i.imgur.com/wPKNWV7.png

You'll notice some differences from the UK version of the code- the UK has no speed limiter code, the VE is a bit different (due to different intake setup?), and it adds 26 timing, above 4000rpm, to cyl4 as well.

Comparison of the raw differences in base timing numbers: https://docs.google.com/spreadsheets/d/10krYOnNX5A2-AM_AzFPGgbGd-xuMDeDtW0hc1FsJwgg/edit?usp=sharing
 

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Discussion Starter · #8 ·
Another interesting tid bit that explains why cylinders 3&4 are always the first to go:

We've known that coolant enters the block at cyl1 and exits at cyl4, so coolant (and thus combustion) temperatures gradiate up towards the exit on the block. The long standing presumption is that it is due to 3/4 being hotter they are more detonation prone. That's only part of the story now...

What I said before about additional timing being added to 1-3 is incorrect. I noticed an inconsistency and Jon checked out the ECU code. Turns out that the ECU treats cylinder numbers by firing order, cylinders 1-3 in the firing order receive additional timing @ >4kRPM >60C coolant temp, >X MAP, the 4th cylinder receives none. Now map that on to 1-3-4-2 firing order: cylinders 1, 3, and 4 have the timing increase, while cylinder 2 does not. Hence, boom.
 

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Dam, that explains a bit of the puzzle with centre cylinder detonation.

Another theory I have is that the centre 2 cylinders (2 & 3) not only run hotter due to reasons above but get more air as the air follows path of least resistance. This in turn raises the AFR above any sequensial fuel increase.

jim
 

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What I said before about additional timing being added to 1-3 is incorrect. I noticed an inconsistency and Jon checked out the ECU code. Turns out that the ECU treats cylinder numbers by firing order, cylinders 1-3 in the firing order receive additional timing @ >4kRPM >60C coolant temp, >X MAP, the 4th cylinder receives none. Now map that on to 1-3-4-2 firing order: cylinders 1, 3, and 4 have the timing increase, while cylinder 2 does not. Hence, boom.
This is a very interesting thread! I'm trying to wrap my brain around why Toyota would increase timing to cylinders 1, 3, 4... and not #2? yes, it's in the center, but so is #3, and 3 runs hotter due to coolant temps.... it's just doesn't make sense. I'd like to know if there is extra fuel being sent to #3? In my PFC tune I send 0.5% of extra fuel to cyl #'s 2&3 since I'm using a center feed manifold.
 

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From what I understand with the OEM tune it appears to be an oversight with the programming which was not recognised. I wonder if it's across all models or only on the UK gen 3 ECU's. There seems to be unexplained differences.

Jim
 

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Discussion Starter · #12 · (Edited)
From what I understand with the OEM tune it appears to be an oversight with the programming which was not recognised. I wonder if it's across all models or only on the UK gen 3 ECU's. There seems to be unexplained differences.

Jim
The hardware is nearly identical across all Gen3 ECUs, there are small circuit changes in the UK version to add support for EGR operation but that's it. The software is pretty much the same too. It's the same on JDM ECUs. I wouldn't be surprised if the gen2 ECU contained similar ignition logic, given they're both distributor CPS based.

paluce said:
This is a very interesting thread! I'm trying to wrap my brain around why Toyota would increase timing to cylinders 1, 3, 4... and not #2? yes, it's in the center, but so is #3, and 3 runs hotter due to coolant temps.... it's just doesn't make sense. I'd like to know if there is extra fuel being sent to #3? In my PFC tune I send 0.5% of extra fuel to cyl #'s 2&3 since I'm using a center feed manifold.
Yeah, adding extra fuel hypothetically helps but being able to pull 0.5-1 degree of timing would be much more effective- given if we could rewrite the advance code to support per cylinder advance values. There comes a point where adding fuel doesn't really provide additional detonation resistance and just makes you lose power, I trust you keep in mind.
 

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I've printed off the above pics of ECU tables to study and try and understand logic. It also gives me some info to compare with my EMS in case I have some values which are out grossly of kilter with OEM figures. Thanks for the info.

jim
 

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In the ECU code there's two fixed timing values that are referenced in the code.

86 - equates to 5 deg BTDC for cranking
128 - equates to 10 deg BTDC for diagnostic mode
Did anyone ever figure the formula for converting code in to deg's? Looking through the Ignition table it doesn't quite add up.

In my PFC tune I send 0.5% of extra fuel to cyl #'s 2&3 since I'm using a center feed manifold.
I'm setting up my EMS tune and sequential fuel. Can I ask how you determined the 0.5% extra fuel for cyl 2 & 3 and at what point (rpm & MAP) do you inject? I was thinking something like 7% added fuel above 180kpa and 3200rpm.

jim
 

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Discussion Starter · #15 ·
I built the OBD1 logging cable and played with timing at idle. It appeared that 2 points of ignition adjusted timing by 0.5 degrees at same RPM/MAP values. However, dividing all the cells by 4 gives many of them unrealistic degree values. Assuming that each point is one fifth of a degree gets many of the vacuum values either spot on or very close to the logged value in degrees. Only issue is that the timing I'm seeing under load is far retarded from what this assumption would make you expect, and the ECU says there's no knock either...

ATS Aaron said, during his time playing with a Techtom MDM-100, that a perfectly OK running car basically says it's knocking all the time. I'm seeing single digit to low teens in many areas under boost.
 

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Very useful info. I think I might make a copy of the JDM map and compare to what I have set in my tune. It would be good if I can safely advance my ignition in certain parts but I have been hesitant to do so because I'm picking up some knock using the MSv2 ECU. Believe its more of an adjustment to ECU than actual knock but need to do more research.

Can I ask what happens above 13.78psi with sock ECU?

And I take it this is the gen 2 JDM and not gen 3? Need to go back into beginning of thread and have another read.

jim
 

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Discussion Starter · #18 ·
This is all gen3, JonS does not have hardware for gen2 right now.

Above 13.78psi the ECU behaves as any other- just uses the maximum values specified in the table
 

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This is all gen3, JonS does not have hardware for gen2 right now.

Above 13.78psi the ECU behaves as any other- just uses the maximum values specified in the table
Thanks Los7, I'm going to cross reference to my current table this weekend and see if anything odd jumps out at me.

jim
 

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units

Hi are the positive values also in inHg? Which would mean the map ends at 13.78inHg = 0.46bar = 7 PSI boost?

Thanks.
 
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