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View Full Version : Upgrading ecu from st185 to st205



rsos1
06-05-2006, 04:10 PM
Does anyone have any information on upgrading from a st185 ecu to a st205 ecu. This would eliminate the AFM. I have found some little things about it but no specific wiring diagrams. I have a RC ecu would this make a differance?

Lagos
06-05-2006, 05:53 PM
it could be done but you would need to spend some rewiring time to make it work. you would also need a 3rd gen map sensor, and the 550 injectors from that car for everything to work right.

Luni
06-05-2006, 07:36 PM
Need ECU, repin harness or new engine harness. 550s, map sensor, IAT sensor, MAT sensor, ignitor.

Its an expensive conversion and not worth it in the end unless you can get that shit for cheap.

Gurr
06-05-2006, 09:26 PM
Well, I wouldn't say useless in the end. It allows you to use all the piggy backs the 205 ecu has...

ChrisD
06-05-2006, 10:42 PM
Also renders your TVIS and cold start injector useless. But it can be done (and has been) with some repinning. Gets you into 540cc injectors though.

Luni
06-06-2006, 04:04 PM
For the money youd spend on the 205 ECU and crap you could get a decent used standalone. Youre looking around 800-1000 for all the crap. I priced it out once. It was ridiculous.

But if youre wanting to do it I knwo someone who has a gen3 MR2 Turbo ECU.

ChrisD
06-06-2006, 04:08 PM
Yep it wouldnt be cheap. And theres no guarantee the tuning will be good for a gen 2 engine. Not the way I'd go personally, but it can be done.

scothaniel
06-09-2006, 03:40 AM
The only expensive / hard to find parts are the MAP sensor and ECU. Everything else is cheap and easy to find.

ST205 Ignitors are the same as practically every mid 90's Toyota - from the ST20x Celica's, 90-94 Tercel, 91+ Paseo, 94+ rav4, 94+ Previa, 94+ GS300 and LS400

The IAT is the same as any ST20x Celica, though any temp sensor will work.

The MAT is Celica only - BUT it has the same temp range as any other Toyota temp sensor (water or air). Toyota use's standard NTC sensors so that they are all interchangable. You can also buy a 1/8 NPT sensor from summit and tap into the stock manifold or IC piping - The ECU has no problems with it.

The MAP sensor is tricky - I had a spare when converting my 3SGE over, so I was lucky. You can see the pressure/voltage relationship here: http://gtfour.supras.org.nz/mapsensor.htm
Just need to find the best matching map sensor - or maybe cross reference the denso part number to another vehicle line.

rsos1
06-10-2006, 05:31 AM
Thats what i have read also. The only hard and expensive thing to find would be the ECU. Does anyone have the wiring diagrams on how to switch it over? It shouldnt be that hard wouldnt you just be able to look at the ecu pinouts?

burnyd
06-10-2006, 09:27 AM
Well it would be really hard to find a st205 ecu. So Im not really sure how much it would honestly run you. your best bet is a standlone.. Someone like A motech. Which is actually plug and play for a sw20/st185 Computer. Even if you found a St205 computer wiring would not be fun.

Dlux4life
06-10-2006, 03:28 PM
**Caugh Caugh** I have an st205 ecu i got from my engine importer and didnt use it in my swap ** Caugh Caugh** Yours for 300$ + Ship **Caugh Caugh**..Ahem...something in my throat...

scothaniel
06-11-2006, 05:21 AM
I've bought 2 x 3rd gen 3SGTE ECU's in the past year - MR2 and Celica. Both were around $220. The MR2 and Celica ECU's are pretty much interchangable - I perfer using the MR2 's if you dont have the W/A IC setup.

Repinning a ST185 harness for these ECU's are pretty easy. Just convert the 185's EGR wires to use for THAM and tap into the AFM wires for THA. Everything else is just moving wires at the ECU. If you can get your hands on a VPC harness, you can repin the wires there to leave the 185 harness mostly un-modified.

The wiring diagrams for the 205 are on this site.

rsos1
06-12-2006, 01:38 AM
Does anyone have a ECU pinout for a st185 RC ecu

alltracman78
06-12-2006, 03:15 AM
I've got a CS pinout.
It should be similar, but it probably won't be exact...

Punisher
06-12-2006, 06:29 AM
I've bought 2 x 3rd gen 3SGTE ECU's in the past year - MR2 and Celica. Both were around $220. The MR2 and Celica ECU's are pretty much interchangable - I perfer using the MR2 's if you dont have the W/A IC setup.

Repinning a ST185 harness for these ECU's are pretty easy. Just convert the 185's EGR wires to use for THAM and tap into the AFM wires for THA. Everything else is just moving wires at the ECU. If you can get your hands on a VPC harness, you can repin the wires there to leave the 185 harness mostly un-modified.

The wiring diagrams for the 205 are on this site.

You kick ass.

rsos1
06-12-2006, 03:12 PM
can you send or post that pinout on the RC ECU jeremy? How did those struts work out for you?

alltracman78
06-16-2006, 02:16 AM
Hey, I missed this.
Sorry.

The struts worked great!
It's a whole different car with the RC suspension. :D
But I blew my turbo. :sigh:
So when I finally get that back I'll be back on the road.

I will send those to you, but I have to figure out a problem with my yahoo first.
I'll see if Jay will shoot them to you.