[Pkula]

Hi everyone, I got a 1990 celica gts with a 3sgte swap from an st205. I got some problems with it and was wondering if anyone can help me with it. I bought the car with the 3sgte and whoever did the swap didnt know what they were doing :headbang:. I got 2 problems. 1. I think the ecu is screwed up because the enginne will cut out at 5500rpm and its suppose to at 7500. (I know because i had and st205 before). It has the ecu from an st205. So how do i rewire this ecu? and Number 2. The transmission blew in the car. I read in diff forums that the celica tranny can only last 220hp and mines running 270. So can i use a different tranny like from an mr2? would that be alright? Would i have to change the clutch if i did an mr2 tranny swap? If anyone would let me know that would be great thx alot

 

[93celicaconv]

Good luck with taking ownership of someone elses work, especially engine swaps like this.

Engine high throttle cutoff is controlled by a tuned crystal within the ECU itself. If your ECU was from an ST205, then that crystal is tuned to intiate a fuel cutoff when the engine it controls reaches an RPM that is considered too high for the safety of that engine. There isn't any different wiring you can do to change this. And I would think the crystal in your ST205 ECU would not have been changed. Maybe the original person doing the swap changed the crystal in the ECU?

Sounds like you want to use all the HP your 3S-GTE can put out. I'm not aware of any potential transmissions that are FWD, that fit in a GT-S, and also fit on a 3S block, that can handle that kind of input torque. I know some people put in transmissions from V6 Camry's, but even the 3.0L V6 Camry doesn't put out 270 HP.

 

[Pkula]

Good luck with taking ownership of someone elses work, especially engine swaps like this.

Engine high throttle cutoff is controlled by a tuned crystal within the ECU itself. If your ECU was from an ST205, then that crystal is tuned to intiate a fuel cutoff when the engine it controls reaches an RPM that is considered too high for the safety of that engine. There isn't any different wiring you can do to change this. And I would think the crystal in your ST205 ECU would not have been changed. Maybe the original person doing the swap changed the crystal in the ECU?

Sounds like you want to use all the HP your 3S-GTE can put out. I'm not aware of any potential transmissions that are FWD, that fit in a GT-S, and also fit on a 3S block, that can handle that kind of input torque. I know some people put in transmissions from V6 Camry's, but even the 3.0L V6 Camry doesn't put out 270 HP.

Thanks for the reply. Is there anyway to reset the ecu?

 

[93celicaconv]

Thanks for the reply. Is there anyway to reset the ecu?

Not when it comes to cutoff engine speed. The crystal has a resonant frequency, and as the engine speed impulses to the ECU change with engine speed, once the impulse frequency matches the crystal resonant frequency, the ECU detects resonance and kills the fuel (maybe the ignition as well, I don't remember anymore). You can't change the resonant frequency of the crystal you have. You can buy different crystals to replace, though. But for the life of me, if you have an OEM ECU that has never been tampered with, you have the correct crystal in that ECU to match up with the cutoff limits for that engine.

 

[Murgatroy]

You have several options on transmissions. You can convert an MR2 transmission to FWD, or you can get a transmission out of a V6 Camry. Either will work, however you will have to change your crossmember out for an ST185 one.

The other option is to convert an AWD transmission to FWD, as this is all an MR2 transmission is. There is information about this on the web.

Those transmissions can handle more horsepower. So can the stock S53 or the S54, both of which have been known to handle 300+ HP. Sometimes though, they don't. It is basically a crap shoot. Some do, some don't.

Also, what makes you assume you are pushing 270 HP? The 3rd Gen 3SGTE is only rated for 250 HP. And if your engine isn't revving all the way, that easily means that you aren't even reaching the full 250 HP your engine makes stock.

 

[Murgatroy]

Not when it comes to cutoff engine speed. The crystal has a resonant frequency, and as the engine speed impulses to the ECU change with engine speed, once the impulse frequency matches the crystal resonant frequency, the ECU detects resonance and kills the fuel (maybe the ignition as well, I don't remember anymore). You can't change the resonant frequency of the crystal you have. You can buy different crystals to replace, though. But for the life of me, if you have an OEM ECU that has never been tampered with, you have the correct crystal in that ECU to match up with the cutoff limits for that engine.

You can change the crystals and it has been done. Mr. Turrari has done it on his 5SFE and considers it 'overclocked.' It essentially makes the ECU think the car is running at a different RPM and changes the A/F mixture.

It is not a novice modification though.

 

[93celicaconv]

You can change the crystals and it has been done. Mr. Turrari has done it on his 5SFE and considers it 'overclocked.' It essentially makes the ECU think the car is running at a different RPM and changes the A/F mixture.

It is not a novice modification though.

Yes, the crystal can be changed. And the high speed cutoff speed can be increased, at the cost of not having the correct A/F ratio. Another adjustment needs to be implemented to offset this induced ECU error.

But the primary question is, why is the engine being cut off at 5,500 RPM? Isn't the OEM crystal in the original ECU supposed to allow an engine speed greater than that? So why is the ECU with an OEM crystal limiting the engine speed below the OEM upper speed limit?