Using a 99 Clone ECU in a 91

[Alex3000gt]

I searched, and the information was pretty scattered. I thought it would be helpful to post all of the information in one place for people in the future.

Goal: Use a 99 Clone ECU in a 91 RT/TT.

What is needed:
-A 99 Clone ECU
-Adapter harness to connect your 91 vehicle side plugs to the 99 ECU interface
-Fan control - First gen radiator fans are controlled by temp switches at the bottom of the radiator, independent of the ECU. The 99 ECU controls the fans, so a harness to connect to the stock fans is needed
-Manifold Air Pressure (MAP), this sensor doesn't exist on first gen cars but the 99 ECU is not expecting a signal. No change required.
-Cam vs crank angle sensors. The 91 uses a cam angle sensor while a 99 uses a cam and crank angle sensor. No adjustment is needed as far as the ECU is concerned.

Please feel free to chime in. This isn't intended to be perfect on the first pass, and I will edit this post as more information flows into the thread.

[Greg E]

-Fan control - First gen radiator fans are controlled by temp switches at the bottom of the radiator, independent of the ECU. The 99 ECU controls the fans, so a harness to connect to the stock fans is needed

You can keep your 91 setup if you don't wish to convert to the ECU control.

-Manifold Air Pressure (MAP), this sensor doesn't exist on first gen cars but the 99 ECU is expecting a signal.

No it's not.

-Cam vs crank angle sensors. The 91 uses a cam angle sensor while a 99 uses a cam and crank angle sensor. I am sure there is some software adjustment that can be made to accomodate for the signal differences, if any is needed.

Nothing needs to be adjusted.

[Alex3000gt]

You can keep your 91 setup if you don't wish to convert to the ECU control.



No it's not.



Nothing needs to be adjusted.

Thanks for the info. I updated the original post. It looks like the ECU is just a drop in once you have a fan control harness and ECU adapter harness.

I am considering the 99 ECU as a replacement since my stock ECU finally kicked it due to leaking capacitors. I figured it may be a nice "future proof" for any future upgrades, and the new capacitors can't hurt either.

[Greg E]

I forgot to include the instructions for wiring up the 1G fans to be ECU controlled. (note: this setup is optional. Your fans will still work with the thermo-switch setup if you choose not to wire up ECU control)

http://www.cloneecu.com/wiring-guides/1g-fan-control

AND

http://chromedecu.org/?p=823

[ChargerX3]

Might want to make some minor timing map changes though once you get it. The latencies are slightly different.

[Alex3000gt]

What are the risks of not adjusting for the latencies? Not able to retard ignition timing under knock conditions quickly enough?

[Alex3000gt]

Getting closer to pulling the trigger on this. Need to buy the wife an anniversary gift first.

[Ange]

I forgot to include the instructions for wiring up the 1G fans to be ECU controlled. (note: this setup is optional. Your fans will still work with the thermo-switch setup if you choose not to wire up ECU control)

1G Fan Control | THE ORIGINAL VR4 Clone? ECU

AND

Chromed ECU | 91-93 Radiator Fan Control Conversion for Flash Ecu

damn never thought of that. need to get this. have fmic so probably a good idea for me.

[Chris@Rvengeperformance]

Lowering the fan temps makes a big difference in the cars temps. My car doesn't get over 190 hardly ever now

[aaronatstate]

What are the risks of not adjusting for the latencies? Not able to retard ignition timing under knock conditions quickly enough?

You will get knock more quickly. With the 1g setup on the flash ECU the timing is advanced up to 4 degrees in the upper RPMs.

The true timing the engine runs is: Timing called for by ECU + (RPM*.0005). This factors in the latencey differences for the different sensors.

I've been running a 99 Clone ECU in my 92 RT/TT for almost 3 years now with zero issues.