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Old 05-03-2019, 11:26 AM   #1
tomasss
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Default TCU removal

So, I am completely removing the TCU on my B204GT.
The boost pressure is going to be controlled via MBC, the radiator fan is gonna be controlled via external temperature switch so I can completely remove the unit from the car.

I checked the schematics and it looks like this (4/10 is EZK, 4/23 is LH2.4, 4/21 is TCU):


And as I care about the outputs only, the pin # to consider are:
1 - goes to TCU solenoid (no longer valid) -> OK
4 - goes to fan relay (high speed) and also to the LH - any idea what this does in LH?
5 - goes to fan relay (low speed) -> OK (external fan control)
6 - blocking relay for A/C -> OK (no A/C in my car)
7 & 24 - goes to TPS potentiometer do I understand correctly that lh2.4 uses only the microswitch for the corner cases only? Somehow I thought it uses the potentiometer already...
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Old 05-03-2019, 01:01 PM   #2
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If you want to start modifying as something as complicated as the b204ft LH setup with all the associated ECUS... you should just go with a stand alone. It will be much less complicated and more straight forward.
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Old 05-03-2019, 02:38 PM   #3
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The fan works by the ECU completing the ground circuit to the relay and it first starts low speed then goes turns on high speed. So ground wire from the ECU to relay turns on fan at certain temp from temp sensor. If you look at the relay it gets power from the battery so ground controls the stock relay.
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Old 05-04-2019, 03:33 AM   #4
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Hi, the high speed fan wire going to the LH is not for fan control. The control is in the TCU, as Simon stated it only gives the ground path. That wire is only for the LH to know the fan has started at higher speed and to compensate any idle fluctuations that this may cause. Pot on the TPS is also only used by the TCU, LH only wants idle switch. Removing TCU from the equation is simple if you sort out the fan contol. Don't forget wiring knock output from EZK to the LH. On B204FT the input used is from EGT sensor.
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Old 05-04-2019, 06:59 AM   #5
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Quote:
Originally Posted by blkaplan View Post
If you want to start modifying as something as complicated as the b204ft LH setup with all the associated ECUS... you should just go with a stand alone. It will be much less complicated and more straight forward.
I don't agree. The "all the associated ECUS" is actually only the TCU. As soon as that one is gone, it is basically the normal setup with LH2.4 and EZK116k. And tuning that is far more easy than rewiring everything for me.
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Old 05-04-2019, 07:02 AM   #6
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Originally Posted by sbabbs View Post
The fan works by the ECU completing the ground circuit to the relay and it first starts low speed then goes turns on high speed. So ground wire from the ECU to relay turns on fan at certain temp from temp sensor. If you look at the relay it gets power from the battery so ground controls the stock relay.
But that is not my question yeah, the circuit is completed by grounding, but as you can see on the schematic it is not controlled by the ECU but TCU in this case...and the question was why it still goes to the ECU then.

Last edited by tomasss; 05-04-2019 at 07:11 AM..
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Old 05-04-2019, 07:09 AM   #7
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Originally Posted by ipdown View Post
Hi, the high speed fan wire going to the LH is not for fan control. The control is in the TCU, as Simon stated it only gives the ground path. That wire is only for the LH to know the fan has started at higher speed and to compensate any idle fluctuations that this may cause. Pot on the TPS is also only used by the TCU, LH only wants idle switch. Removing TCU from the equation is simple if you sort out the fan contol. Don't forget wiring knock output from EZK to the LH. On B204FT the input used is from EGT sensor.
Wonderful, thanks for this post.
Idle fluctuations caused by the high engine temperature or the fan running at high speed? I will just connect that to the external high speed ground then.
I don't get your remark about the knock sensor. That doesn't go to the TCU at all, so as far as I understand there is no change with this. I see that the LH also receives the values from EGTC sensor (pin 28) but I will get a modified firmware that doesn't check that - so I should be fine just leaving that as it is.
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Old 05-04-2019, 07:20 AM   #8
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Wonderful, thanks for this post.
Idle fluctuations caused by the high engine temperature or the fan running at high speed? I will just connect that to the external high speed ground then.
Mode by the power draw of the fan, but maybe both.

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I don't get your remark about the knock sensor. That doesn't go to the TCU at all, so as far as I understand there is no change with this. I see that the LH also receives the values from EGTC sensor (pin 28) but I will get a modified firmware that doesn't check that - so I should be fine just leaving that as it is.
You can wire knock output from EZK to pin 28 of the LH. They work a bit different, but this way you will activate fuel enrichment if EZK detects hard knock on all cylinders.
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Old 05-04-2019, 07:41 AM   #9
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Originally Posted by ipdown View Post
You can wire knock output from EZK to pin 28 of the LH. They work a bit different, but this way you will activate fuel enrichment if EZK detects hard knock on all cylinders.
But how is the knock enrichment done on the stock system? Or it is not present in the stock configuration and your proposal above is an "upgrade"?
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Old 05-04-2019, 07:50 AM   #10
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But how is the knock enrichment done on the stock system? Or it is not present in the stock configuration and your proposal above is an "upgrade"?
On B204FT EGT sensor grounds when exhaust temps goes higher than ~900 degC
LH enriches the mixture in turn to lower the temp.
Normal configuration on B230FT uses knock signal from EZK wired to pin 28 to enrich in case of knock.
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Old 05-04-2019, 07:55 AM   #11
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Quote:
Originally Posted by ipdown View Post
On B204FT EGT sensor grounds when exhaust temps goes higher than ~900 degC
LH enriches the mixture in turn to lower the temp.
Normal configuration on B230FT uses knock signal from EZK wired to pin 28 to enrich in case of knock.
Ok. So stock B204ft basically doesn't enrich the mixture based on knock (only based on EGT) and your proposal makes this possible, do I get it right?
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Old 05-04-2019, 07:58 AM   #12
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Ok. So stock B204ft basically doesn't enrich the mixture based on knock (only based on EGT) and your proposal makes this possible, do I get it right?
Yes, correct, on knock TCU lowers the boost, EZK retards, LH does nothing. Wiring it like this you will make it a works like a standard B230FT configuration.
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Old 05-04-2019, 08:09 AM   #13
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Quote:
Originally Posted by ipdown View Post
Yes, correct, on knock TCU lowers the boost, EZK retards, LH does nothing. Wiring it like this you will make it a works like a standard B230FT configuration.
Wonderful thanks
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Old 05-06-2019, 12:59 PM   #14
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Just for reference: wiring the knock enrichment from EZK -> LH:
On normal B230FT, this is wired from EZK pin #4 to LH pin #28.
On B204FT the output EZK pin #4 originally goes to TCU pin #30.
The enrichment signal from EGTC goes to TCU pin #10, and is connected via the wiring loom to the pin #28 of the LH.
So if my assumption is correct, the only thing I need to do is short the pin #30 and #10 in the TCU connector.
Doing that, I will connect the EZK knock output to the LH enrichment input.

Last edited by tomasss; 05-06-2019 at 01:28 PM..
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Old 05-06-2019, 01:40 PM   #15
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Quote:
Originally Posted by tomasss View Post
Just for reference: wiring the knock enrichment from EZK -> LH:
On normal B230FT, this is wired from EZK pin #4 to LH pin #28.
On B204FT the output EZK pin #4 originally goes to TCU pin #30.
The enrichment signal from EGTC goes to TCU pin #10, and is connected via the wiring loom to the pin #28 of the LH.
So if my assumption is correct, the only thing I need to do is short the pin #30 and #10 in the TCU connector.
Doing that, I will connect the EZK knock output to the LH enrichment input.
I don't remember exact pin numbering on the TCU side right now, but you are correct - shorting those pins will give you connection between ezk knock out and lh enrichment input.
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Old 10-25-2020, 07:03 PM   #16
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Hi both,

Did the TCU/EGTC workaround work well? I am facing these problems with mine 204FT:

A2 -> 223
A6 -> 111
A5 -> 342, 421, 421

2-2-3 Idle air control (IAC) valve signal. Faulty or missing signal.
1-1-1 EZK clear/no errors detected.
3-4-2 A/C blocking relay. Signal faulty.
4-3-1 Temperature sensor. Signal missing.
4-2-1 Pressure sensor. Faulty boost pressure.

And I presume that this is the time I decide whether I am going for a new set of EGTC, TCU etc. or for some kind of upgrade/downgrade... one thing I am worried of is that the TCU should, as far as I am concerned, "dynamically" decide what is the current boost level (eg. does a better job than a "static" MBC). Is that true, or totally not and no actual difference can be felt when moving from original installation to the one proposed in here?
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Old 10-28-2020, 03:23 AM   #17
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The faults for the TCU might be just by faulty temperature sensor/wiring and leaky hose that goes to the pressure sensor. Maybe better to have a look and fix it in 5 mins before you start removing all the stuff?

Regarding your question, I don't have a long term experience because my car is currently undergoing extensive engine rebuild, but I did several short rides with it and it was OK...not throwing any errors and everything was functioning normally. The TCU can indeed dynamically change the boost limit based on many input parameters, that is exactly the reason why I've ditched it...I want to keep the system simple and the operation reliable.
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Old 04-28-2021, 09:14 AM   #18
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To have happy end in this topic...the car is completely happy after the TCU removal. Everything works, boost is stable using the MBC, efan works flawlessly. So it is one of the ways to go if you want to ditch the complicated TCU but still retain the LH/EZK units rather than going completely standalone.
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