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KA42E speed sensor


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I am helping a friend (with the wiring, not the mechanical, so please bear with my limited engine knowledge) convert his KA42E from carbureted to EFI and we are so close. This is a striped down race car (not a stock car). He purchased a #10 manual ECU with S13 harness for the conversion.

 

It has the dreaded "under load, ECU cuts fuel to the injectors before the red line limiter (AKA rev limiter, AKA limp mode, etc)" problem that I've seen in several forums.

 

Some details:

 

1989 KA42E, S13 harness, manual ECU #10

 

We are only using the EFI portion of the harness.

We have wired the remaining portion of the harness as drawn here (the S13 KA42E diagram - link):

 

When the car is in neutral, 1st and 2nd gear, we can hit the rev limiter (a little past 6000 RPM).

In 3rd gear, we can only get to about 4300RPM.

We have to wait until 3000RPM before the ECU turns the fuel injectors back on

 

The neutral, and 5th gear sensors are not connected (there is no 4th gear in this harness).

There is no speed sensor (not using the stock transmission).

 

We have the FSM (link) and have been through it (especially the harness drawing) many times.

 

At first we had a temperature sensor fault (code 41) but a 2K resistor in the sensor connector convinced the ECU that we were always at a pleasant 20C.

After that we got the 55 - all good status.

 

My best guess (from what I have seen in the forums) is that the ECU needs to know the speed to keep from shutting down.

 

I've also read this which may also be the problem (link):

"Cause if the ECU see high air flow value and almost full throttle, for more than 6 second (if I remember right) it will cut fuel...until you release the throttle cable. (on a S13 SR)

 

I don't know if this is real or something localized to their car.

Can anyone confirm this (either the cause of the injector loss or the means to return control)?

 

My questions:

Will telling the ECU the speed of the car fix the problem, or is this a limitation of the #10 manual ECU?

 

If it will fix the problem, how do we tell the ECU how fast we are going when we don't have a speed sensor?

 

Does anyone know what the signals look like that connect to the ECU (S13 harness):

 - pin 3 (Y/R) which goes to the instrument cluster

 - pin 32 (Y/G) which goes to the instrument cluster as well as the resistor module that goes to the power transistor and ignition coil

 

Are either of these pins an vehicle speed sensor (VSS?) input?

 - I imagine if they are an output, it shouldn't matter if they aren't connected.

 - Pin 3 feeds the collector of the power transistor, so my guess is that it is an output, but it is hard to say.

 

Those are all the details I can think of. Let me know if I have missed any important information.

thanks

Steve

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Hi Steve and welcome to Ratsun.

 

I can't help much with this other than to say I thought to get around the rev limiter problem you needed a #11 ECU from an automatic car. Others will join in I'm sure.

 

Try the search function. I input KA rev limiter and got these.

 

http://community.ratsun.net/topic/17831-ka-ecu/

 

 

 

http://community.ratsun.net/topic/51924-ka24e-acceleration-cutoff-issue/ 

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