ParkingLotLust

What exactly is meant by "clamping" the RPM signal?

ericgibbs

hi,
IIRC this circuit was posted on the forum a few weeks ago, if its the same circuit, all it does is limit the high end range of the RPM sensor voltage, before it goes into the ECU.

Do you have the circuit diagram.?

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Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

ParkingLotLust

No I dont, the quote is from nc.org, a forum for Celica's. It just talks about how you would go about raising your rev-limiter using a piggyback or standalone ECU, and I was wondering how the ECU would "clamp" the signal, or what exactly it does (rather than just saying it clamps it).

ericgibbs

Hi,
I have searched back thru the forum I cannot find it again.

The voltage output from the RPM sensor was connected to the input of a OPA wired as a non inverting buffer, the output of the buffer went to the ECU via a 680R resistor.
The second half of the OPA had its output connected to the ECU side of the 680R.
The second half of the OPA was wired with a diode across it so it limited the voltage going to the ECU.
The point where the clamp operated was set by a reference voltage input to the second half of the OPA.

Operation: Upto near full RPM the sensor voltage was passed as normal to the ECU, near full RPM the clamp starts to limit the voltage going to the ECU, so the ECU 'thinks' the RPM is lower than it actually is,,,

Hope you followed this OK.?

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

ParkingLotLust

Ahh, that makes perfect sense. Thanks

Roff

Check out this thread.

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Ron