ST205 ECU for chargecooler pump control

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asdrewq
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ST205 ECU for chargecooler pump control

Post by asdrewq »

Evenin' all

Is anyone successfully running an ST205 ECU on a rev3+ mr2 turbo? I have just picked one up and intend to use it for pump control (& those better fuelling maps), but am struggling to locate pinout diagrams of Mr2/Celica ECU's.

I know the ST205 ECU will require the 3 inputs from the chargecooler pump & the water level sensor which is easy enough. What else is different? I think the rev3 ECU interfaces with power steering ECU, engine bay fan ECU, possibly aircon amplifier?

Any help from anyone who has done or even considered this is appreciated :thumleft:
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Peter Gidden
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Re: ST205 ECU for chargecooler pump control

Post by Peter Gidden »

ST205 GT4 ECU diagram and pinouts:

Image

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Marf
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Re: ST205 ECU for chargecooler pump control

Post by Marf »

asdrewq wrote:Evenin' all

Is anyone successfully running an ST205 ECU on a rev3+ mr2 turbo? I have just picked one up and intend to use it for pump control (& those better fuelling maps), but am struggling to locate pinout diagrams of Mr2/Celica ECU's.


Paging Toxo, come in Toxo.
asdrewq
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Re: ST205 ECU for chargecooler pump control

Post by asdrewq »

I have been attempting this today Using a wiring diagram in japanese for the rev3 ECU I found online, and the celica one posted. One thing that has confuised me - My car appears not to have the PCST pin in the wiring loom (only PS) - These pins are labeled 'ATS' and 'RLY' on the circuit board respectively.

Can anyone who has done this confirm what they did with these pins? I have read several times people had to remove both the PS/PCST pins.
**BETSY**
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Re: ST205 ECU for chargecooler pump control

Post by **BETSY** »

Visit: http://www.gtfours.co.uk/

click on the 'How To'
asdrewq
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Re: ST205 ECU for chargecooler pump control

Post by asdrewq »

I discovered the problem. the diagram I was using to locate the PS/PCST pins was incorect.

From this link: http://www.mr2oc.co.uk/forums/41/129693.html?start=42

PSCT/PS are not on adjacent pins as illustrated. That is the rev1/2 ECU layout. rev3+ is pin 8 for PSCT (as in diagram), pin 18 for PS.

Only PSCT must be cut (ST205 ECU uses this pin for aircon signals). PS is an idle up signal from PS ECU > EFI, and as far as I can see this pin is unused on ST205 ECU so no need to disconnect.

I'm still to wire up the pump signal lines so am running with a check engine light, but the car started and drove down the drive ok.
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Re: ST205 ECU for chargecooler pump control

Post by RST »

There must be an easier way, the CC pump in my ST205 WRC I just bought comes in at about 1,000rpm then waits about 30s then stops. If I recall the a'PEXI RSM I had years ago and simlar devices have PnP's (or NpN's) which can be set to various trigger limits, if you use something like that via a relay then you will have something very similar and simple wiring? Then there'd be no mucking about with the car's wiring with similar end effect?
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Re: ST205 ECU for chargecooler pump control

Post by toxo »

Marf wrote:
asdrewq wrote:Evenin' all

Is anyone successfully running an ST205 ECU on a rev3+ mr2 turbo? I have just picked one up and intend to use it for pump control (& those better fuelling maps), but am struggling to locate pinout diagrams of Mr2/Celica ECU's.


Paging Toxo, come in Toxo.


*waves*

I ran my MR2 on an ST205 ECU for ages. If you've seen the side-by-side comparison rolling road print outs between the two ECUs, they were probably mine.

You only need to disconnect one of the two PS pins but I can never remember which one - but you've already worked that out!

The INT pin replaces the FAN pin, so you lose your connection from the ECU to the engine bay fan controller. This is no big deal - the fan controller runs autonomously.

Some of the pins used for pump monitoring (M+, M- and MTT) I think overlap with pins that are identified as part of the interface between the MR2 ECU and the (optional) traction control ECU. As I've never played with an MR2 with TRC and only actually know of one person with rev3+ TRC, this never bothered me. You can't use the chargecooler and the Toyota TRC together for another reason anyway - the TRC incorporates a 2nd throttlebody with its own throttle position sensor which would encroach into the space the core fits in.

I rebuilt my pump loom using resistive wire rather than inline resistors as it is from the factory - the ancient resistors had crumbled to pieces and I thought resistive wire coated in heatshrink would be a bit more weatherproof.

The ST205 aircon setup is identical, but the power steering pump has an additional idle up valve on it which is another difference between the two ECUs.

Oh and just to check, you are using a JDM ST205 ECU, right? Otherwise you'll lose power!

I know of someone else who's since done this ECU conversion (also on a cari blue rev3!) who didn't have the idle speed problems I encountered. I'm interested to hear how your car idles once the weather has improved a bit.

RST wrote:There must be an easier way, the CC pump in my ST205 WRC I just bought comes in at about 1,000rpm then waits about 30s then stops. If I recall the a'PEXI RSM I had years ago and simlar devices have PnP's (or NpN's) which can be set to various trigger limits, if you use something like that via a relay then you will have something very similar and simple wiring? Then there'd be no mucking about with the car's wiring with similar end effect?


Changing the ECU is the right way to do it IMO, if your intention is to run the chargecooler and retain stock Toyota management. The pump doesn't kick in at 1000rpm, otherwise it would be on constantly at cold idle. There's more logic behind it than that (it's throttle driven not rpm driven for starters). Combine that with warning lights for low coolant level and pump failure, a measurable power increase and a tangible effect in engine smoothness, it's pretty good for £50.
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asdrewq
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Re: ST205 ECU for chargecooler pump control

Post by asdrewq »

Thanks for the input chaps,

The ST205 aircon setup is identical, but the power steering pump has an additional idle up valve on it which is another difference between the two ECUs.


Hi toxo can you clarify this point? do you mean the celica runs a VSV to raise idle when steering is activated? I did not notice an additional PS output on the celica schematic.

Oh and just to check, you are using a JDM ST205 ECU, right? Otherwise you'll lose power!


I'm running 89661-2B840 from a 1994 Import ST205. I believe this is the 'earlier' part number of JDM ECU's :thumleft:

I guessed the UK ECU would be designed around the fact the car ran a steel turbine & EGR etc.

I know of someone else who's since done this ECU conversion (also on a cari blue rev3!) who didn't have the idle speed problems I encountered. I'm interested to hear how your car idles once the weather has improved a bit.


I can provide some preliminary feedback - At first the idle was 1600 on the cold start. I have done around 40 miles now and it seems to have settled down. Cold idle seems higher than the MR2 ECU (up from 1200ish to 1400ish) and settled warm idle is now around 700rpm with oil temp of 86 deg.C.

The warm idle is in line with the idle speed mentioned in the Celica 3SGTE BGB supplement (page EG-33 700+-50rpm) but the cold idle seems high to me. I cannot find a reference as to what this should be. My ICV is in good shape and recently cleaned out.

Also I can barely tell the idle up under electrical load from heradlamps/demister, whereas I found this immediately noticeable with the std ECU. The Celica increases by 50rpm according to the book, I wonder if the mr2 is higher?

When I have everything wired up and no error codes i'll check the idle speeds again.

Changing the ECU is the right way to do it IMO, if your intention is to run the chargecooler and retain stock Toyota management. The pump doesn't kick in at 1000rpm, otherwise it would be on constantly at cold idle. There's more logic behind it than that (it's throttle driven not rpm driven for starters). Combine that with warning lights for low coolant level and pump failure, a measurable power increase and a tangible effect in engine smoothness, it's pretty good for £50.


<<I agree with this :)
asdrewq
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Re: ST205 ECU for chargecooler pump control

Post by asdrewq »

For reference I used the MR2 JDM wiring diagrams from this site:

http://gtfour.supras.org.nz/diagrams.htm

click the links > EFI Schematic Diag 7 & Diag 8

At the top of each diagram it can be seen that the rev3 pinout is indicated by *2 (93.11 onwards)
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toxo
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Re: ST205 ECU for chargecooler pump control

Post by toxo »

asdrewq wrote:Thanks for the input chaps,

The ST205 aircon setup is identical, but the power steering pump has an additional idle up valve on it which is another difference between the two ECUs.


Hi toxo can you clarify this point? do you mean the celica runs a VSV to raise idle when steering is activated? I did not notice an additional PS output on the celica schematic.


I forget exactly how it works, it was a long time ago that I looked into it. See if you can find a parts diagram for the ISCV and vacuum piping for the ST205, it's markedly different.

asdrewq wrote:
Oh and just to check, you are using a JDM ST205 ECU, right? Otherwise you'll lose power!


I'm running 89661-2B840 from a 1994 Import ST205. I believe this is the 'earlier' part number of JDM ECU's :thumleft:


It is! Same I had (Well I had both but the earlier one is the one I ran long-term).

asdrewq wrote:I guessed the UK ECU would be designed around the fact the car ran a steel turbine & EGR etc.


95RON fuel, mostly.

asdrewq wrote:
I know of someone else who's since done this ECU conversion (also on a cari blue rev3!) who didn't have the idle speed problems I encountered. I'm interested to hear how your car idles once the weather has improved a bit.


I can provide some preliminary feedback - At first the idle was 1600 on the cold start. I have done around 40 miles now and it seems to have settled down. Cold idle seems higher than the MR2 ECU (up from 1200ish to 1400ish) and settled warm idle is now around 700rpm with oil temp of 86 deg.C.

The warm idle is in line with the idle speed mentioned in the Celica 3SGTE BGB supplement (page EG-33 700+-50rpm) but the cold idle seems high to me. I cannot find a reference as to what this should be. My ICV is in good shape and recently cleaned out.


That should settle down. My MR2 always did that whenever I reset the ECU. The Celica BGB says it'll idle at 700ish rpm and I'm sure the MR2 one says more like 800-850. I noticed the drop quite a lot as I had TRD engine mounts fitted which transmitted the extra vibration through the car. You can easily raise the idle rpm slightly by pulling the ELS pin on the ECU to +12v.

Your ECU may not settle down until you've cleared all your engine warning lights by wiring the pump up.

asdrewq wrote:Also I can barely tell the idle up under electrical load from heradlamps/demister, whereas I found this immediately noticeable with the std ECU. The Celica increases by 50rpm according to the book, I wonder if the mr2 is higher?


Unsure, really. I had so many naff batteries and alternators during my ownership that I was always having voltage drops and the like with headlights. Plus as I mentioned above I had ELS permanently on to raise the idle.
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asdrewq
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Re: ST205 ECU for chargecooler pump control

Post by asdrewq »

Update - Pump/level sensor wired in. After a quick ECU reset all is working perfectly - No idling problems to report.

The ecu only turns the pump off after 30s of idle, and restarts it with the tiniest of throttle movements, so if you have your pump relay wired to +IGN source like I did it's not really worth a rewire.
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Re: ST205 ECU for chargecooler pump control

Post by shinny »

toxo wrote:I know of someone else who's since done this ECU conversion (also on a cari blue rev3!) who didn't have the idle speed problems I encountered. I'm interested to hear how your car idles once the weather has improved a bit.


Oh, hello there 8)

I see I'm a tad late to this party :oops:

asdrewq wrote:
Oh and just to check, you are using a JDM ST205 ECU, right? Otherwise you'll lose power!


I'm running 89661-2B840 from a 1994 Import ST205. I believe this is the 'earlier' part number of JDM ECU's :thumleft:


I looked this up on Toyodiy and I don't remember finding a UK/JDM difference here. I'm also running the 2B840 ECU (from a JDM car IIRC) and haven't seen any convincing reason on the net to change to the 2B841 version.



For reference, this was my post over on MR2OC describing what I did, having received some guidance from Toxo:


shinny wrote:Here's a hacked together pinout showing the pins you need for the conversion.

Image

My car has a field harness which makes playing with the ECU wiring much easier. I therefore don't know if the SW20 ECU plugs have pins in all the necessary lines. Toxo bought new ECU pins to overcome the need to chop any wires :th:

Pump:
M-, M+ and MTT are all on the pump's wiring loom (grey with blue, green or black stripe) and should replace any pins already in the loom at the positions shown. INT is pulled to ground to turn the pump relay on, and hence should be connected to one side of a relay's solenoid (the other side connected to some 12V source - I used the same as the pump). This relay switches the 12V source for the pump, line B on the pump's wiring (black with a white stripe). The pump is grounded via line E (white with a black stripe)

If you don't have the full 5-pin loom for the pump I believe this can be reconstructed if really required.

Charge cooler:
The LEV pin is connected to one side of the coolant level switch on the intercooler. The other wire from the switch should be tied to ground.

Power steering:
The PSCT line needs to be cut to maintain the MR2's power steering. I also cut the PS line by mistake first and haven't yet found a reason to reconnect it.
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Re: ST205 ECU for chargecooler pump control

Post by toxo »

shinny wrote:
toxo wrote:I know of someone else who's since done this ECU conversion (also on a cari blue rev3!) who didn't have the idle speed problems I encountered. I'm interested to hear how your car idles once the weather has improved a bit.


Oh, hello there 8)

I see I'm a tad late to this party :oops:



lol!

shinny wrote:I looked this up on Toyodiy and I don't remember finding a UK/JDM difference here. I'm also running the 2B840 ECU (from a JDM car IIRC) and haven't seen any convincing reason on the net to change to the 2B841 version.


I've absolutely no clue what the difference between the JDM part numbers is (jon sole couldn't find any differences in maps), but the UKDM ECU *is* different. It won't have a 112mph speed limiter and is highly likely mapped for 95RON fuel. This would explain why JDM ST205s are ~255BHP and UKDM ones are ~240.

JDM:
89661-2B840 (02/1994 - 02/1995)
89661-2B841 (03/1995 - )

UKDM:
89661-2B850
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shinny
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Re: ST205 ECU for chargecooler pump control

Post by shinny »

toxo wrote:JDM:
89661-2B840 (02/1994 - 02/1995)
89661-2B841 (03/1995 - )

UKDM:
89661-2B850


Oooh, look at that... I'm blind to the difference between a 4 and a 5 :oops:

I stand corrected :thumleft:



(It also makes alot more sense that there is a difference :whistle: )
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Re: ST205 ECU for chargecooler pump control

Post by megamonkeyman »

Are there any power gains to be had by swapping? I have a Rev 1 turbo converted to Rev 3 ECU, the only problem is there is no chargecooler in my setup.
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Re: ST205 ECU for chargecooler pump control

Post by shinny »

megamonkeyman wrote:Are there any power gains to be had by swapping? I have a Rev 1 turbo converted to Rev 3 ECU, the only problem is there is no chargecooler in my setup.


Toxo's dyno graphs suggest there are minor gains to be had... however the main reason we converted was for warning if the fluid level dropped or the pump failed.

The black line is the ST205 ECU, the pink the rev3 MR2 ECU...

Image

Image

Now my car turns on the CEL and reverts to safe mode whenever the coolant level is even a fraction low, it's got me to really sort out my system's headertank and bleeding situation, whcih can only be a good thing :thumleft:
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Re: ST205 ECU for chargecooler pump control

Post by shinny »

Oh, one very good reason not to do this without the chargecooler system is that the GT4 boys have difficulty fooling the ECU into thinking the pump is actually there. Some use resistors, some use light bulbs; but AFAIK no solution works for 100%. And if the ECU thinks the pump has failed, it's back to safe-mode for you! This is why, when GT4 owners fit a FMIC, they end up seeking out the rev3 MR2 ECU.
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Re: ST205 ECU for chargecooler pump control

Post by asdrewq »

shinny wrote:
Now my car turns on the CEL and reverts to safe mode whenever the coolant level is even a fraction low, it's got me to really sort out my system's headertank and bleeding situation, whcih can only be a good thing :thumleft:


I reccomend using the ST205 coolant overflow tank. I haven't needed a coolant topup in months, including a 3000mile EU roadtrip :thumleft:

My mounting location (aluminium bracket paint optional):

Image
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Re: ST205 ECU for chargecooler pump control

Post by toxo »

asdrewq wrote:
shinny wrote:
Now my car turns on the CEL and reverts to safe mode whenever the coolant level is even a fraction low, it's got me to really sort out my system's headertank and bleeding situation, whcih can only be a good thing :thumleft:


I reccomend using the ST205 coolant overflow tank. I haven't needed a coolant topup in months, including a 3000mile EU roadtrip :thumleft:

My mounting location (aluminium bracket paint optional):

Image Replaced With URL For Quote http://url266.imageshack.us/url266/8021/dsc06421p.jpg


I did similar, but mine was attached to the Apexi induction kit bracket. You can just about see it here next to the radiator cap:

Image

The big difference between the ECUs for me was the fuel map. Look at the AFRs when you reach significant boost at 3500/4000rpm between the two ECUs, in the second graph. Very different!
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