[Mk2] [Turbo] ST205 Chargecooler Installation Guide (non 56k friendly)

[toxo]

It would have complicated things massively, it would be a massive pain and for very little benefit. With the adapted bracket the core is still attached at one point on each side.

I had a thought, another reason we wouldn't have any difficulty getting ST205 parts over here is that they did sell the car here.

[jspec mkii mr2]

It would have complicated things massively, it would be a massive pain and for very little benefit. With the adapted bracket the core is still attached at one point on each side.

I had a thought, another reason we wouldn't have any difficulty getting ST205 parts over here is that they did sell the car here.

Yeah, that may have made getting these parts a lot easier. I got a response from the US based Toyota dealership today basically telling me they can't get the parts because it wasn't a car that was sold here. Unfortunately, I didn't get a response from the dealership you got your parts from, either.

[>PETE<]

Toxo,

Very interesting read! Would you agree that a MR2 ECU is the same as a celica one in terms of how the power steeing is controlled from the ecu?

I've noticed that when I run the ST205 ECU, I don't get any power assist, sometimes I get it for the first 10secs of turning the engine on after its sat and its still hot. No idea why this happens. I've also noticed that when I run this ecu, sometime when I brake my boost gauge in the cluster goes all the way to the top. Once the car has come to a stop the boost gauge goes all the way back down, not sure if this is tied to the fact the MAP sensor is a Gen III instead of a Gen II?

When I plug in a Gen III MR2 Powerfc the power steeing works a treat. However the high electrical load pinout is always on and I cannot get it to switch off. I've tested the pin and it seems to be working correctly, so I'm wondering if its somehow tied to the power steering as well?

I thought my pinouts were done correctly and can't seem to find any other faults.

The power steering does connect to the ECU. It has two pinouts (PSCT + PS from the Gen II) When I connect my Gen III MR2 ECU to the car my power steering starts working, whereas when I connect the ST205 ECU to power steering stops. Remember that the power steering on the ST205 ran via the engine rather then an electric pump.

Ah well, that can't be that hard to fix Also I've got a rev3 so there should be fewer differences between the ECUs (if there are any other than MAP vs AFM rev2 -> rev3 anyway).

The Jap St205 was advertised to put out 255Hp Compared with a Jap Gen III Mr2 being only 245hp. The only real difference between the two was the intercooler, so I can only guess they advanced the timing slightly between the ECU's.

Hm interesting. I can't remember whether my ECU is from a UKDM ST205 or a JDM ST205, I did look when I got it but that was months ago...

I have done some more research into this. The communication between the EFI ECU and the P/S ECU is different on rev1-2 and rev3. Rev1/2 has PS and PSCT which rev3 doesn't have. It's something to do with the idle speed control so that the power steering can raise the revs when it's under load on the Rev1/2 whereas the Rev3 can work it all out without the 2 ECU's talking to each other (maybe due to AFM/MAP differences?)

Rev3 just has PSCT which when grounded turns the P/S off. So all I have to do is break the PSCT connection to the ECU and it should continue working as normal. So, I need to pull my finger out and switch ECU I think G-tech has provided me with some new ECU pins so I can repin my loom to accept the chargecooler once I rebuild the loom.

[toxo]

I'd say that the rev3 ECU and the ST205 ECU are indistinguishable in the way they control the power steering yes. Because you have a rev2 your power steering control unit in the frunk doesn't run properly without input from the ECU, but a rev3+ one does.

In the mean time I have found out why the ST205 ECU produces more power with some help from someone on twobrutal!

[Marf]

In the mean time I have found out why the ST205 ECU produces more power with some help from someone on twobrutal!

I wonder if Jon will be able to nab the maps out of the ST205 ECU, then flash them onto his newfangled ECU for the benefit of those of us running the 205 CC

[toxo]

In the mean time I have found out why the ST205 ECU produces more power with some help from someone on twobrutal!

I wonder if Jon will be able to nab the maps out of the ST205 ECU, then flash them onto his newfangled ECU for the benefit of those of us running the 205 CC

I don't see why not, it's only the VE map and fuel map that are different (that he's found so far). The thing that would be more difficult to replicate with his piggyback system would be pump control, etc. No one really seems to know the logic for that, some people say it runs the pump during boost & for 30 seconds afterwards? We shall see.

I also intend to run both the ST205 and Rev3 MR2 ECUs next trip to Surrey Rolling Road (unless GTech needs my ECU sooner than that) so we can see the definitive difference.

[jon]

I'd say that the rev3 ECU and the ST205 ECU are indistinguishable in the way they control the power steering yes. Because you have a rev2 your power steering control unit in the frunk doesn't run properly without input from the ECU, but a rev3+ one does.

On my Rev 3 the power steering doesn't work at all with a ST205 ECU I haven't yet tracked done why but from memory there are a few components missing on the ST205 ECU PCB that are present on the Rev 3 ECU.

[toxo]

Disconnect PSCT pin from the ECU plug and see what that does

[>PETE<]

Very interesting. I'm going to have a poke around tonight at the pins to see if I can get it working.

I'll let you guys know what I manage to find out.

I did have a read on the differences. Certainly is very interesting! It would be great to be able to get the ignition map so I can program the same into my Powerfc. Great Baseline to work from!

[>PETE<]

OK, well i poked around with the ECU pins and tried putting them into different ECU slots according to the different ECU pinouts I've found.

It looks like I definatley have it pinned correctly for the MR2, as when this ECU is plugged in (Powerfc) the power steering only comes on when the engine is running (PSCT is connected to the ATS ECU Pin)

PS has been pinned to the ABV ECU pin.

If I plug the ST205 ECU in, power steering never comes on. If I unplug the PSCT pin from the ECU, powersteeing comes on when key is on ignition, before the engine has started.

From this, I can only conclude that the ST205 ECU is definatley not designed to work with the MR2 power steering.

Comments?

[toxo]

You've missed a point I raised earlier on in the thread which is that the ST205 ECU should work with the REV3 power steering (provided PSCT is disconnected). The Rev1 & Rev2 power steering control unit is not autonomous and cannot function without input from the ECU which the ST205 ECU does not supply.

[jon]

So in summary:

The PSCT signal is used on the Rev 3 to disable the power steering. On a stock Rev 3 ECU the power steering will be disabled when the engine isn't running, presumably to prevent the battery draining if the ignition is left on.

On a stock ST205 ECU, there is no facility to control the power steering, so the PSCT pin is grounded which has the effect of always disabling the power steering.

Does that sound correct?

[toxo]

I believe that to be the case yes.

[>PETE<]

interstingly enough, I've also found documentation to state that the Intercooler Fan ECU is also different in the Gen III. Where by one wire goes between that and the cars ECU to override the engine bay temp for switching on the fan.

Gen I/II's don't have any integtration between the cooling fan ecu, and the car ecu.

Also, do anyone know if there is a difference between the ELS system of a gen III and a gen II. I can't seem to get this working on the Gen III. The ecu keeps on telling me ELS is always on, when it isn't. (headlights off + defogger off). I've even pulled the pin out of the ECU, and I can assure the wire is in the correct ECU pin.

[toxo]

Not sure what you mean by ELS?

Moved the pump today as over the year since it's been fitted I've smacked it into a few things. It was a little bit too low in hindsight Nice and simple, rotated the bracket on the gearbox through 180 degrees then split the clamp from the mount and rotated that through 180 degrees as well. Lovely job, all fitted nicely but I had to cut the pipes shorter which meant draining the coolant, refilling, bleeding again etc. Ball ache!

[>PETE<]

ELS is the Electrical Load Pin. Tells the ECU when its under high electrica load. Usually its triggered by the rear window demister + front headlights.

[toxo]

Found the diagram I was after:

Image Replaced With URL For Quote http://www.gtfours.co.uk/forum/code54/original.jpg

Discovered at the weekend that this diagram is not correct. There's at least 2 resistors in the pump wiring... the one between the green wire and pink wire has fallen to pieces in mine but I found at least 1 more. Will rip it to bits next weekend (weather permitting) and find out what's what.

[>PETE<]

Thats correct, 2 resistors and a relay to get rid of the Code 54 Error. I've done it myself on the ST205 ECU I'm running. Never had 1 problem since it was soldered in. I'll see if I can pull up the diagram I used. (Which has reference to the corretc resistor values)

[JasonB]

Great thread this.
I've got a set up that I plan to fit in the next month or two so I'll be using this as a workshop manual.

Just a quick question though.
The kit I have has a Celica ST205 rad. It seems that the Fiat Cinq. rad is the normal choice.
Has anyone ever fitted a stock ST205 front rad to an MR2 with or without air con? Stock or aftermarket bumper?

Just trying to work out why the Celica rad is not normally used.

JB

[toxo]

I believe it's only possible to fit the ST205 prerad in behind the stock bumper if you lose the aircon. Fiat rad is only £30 new and is much more readily available.