FAQs

Question:
How do we fit the crankshaft sensor? We cant see anything to attach a bracket to so we can fit it so it points upwards.
Alternatively, is it possible to rotate the trigger wheel either to one of the other possible positions around the pulley to enable us to mount it elsewhere?

Answer:
We mount the crank sensor at 6 o’clock on the engine is for a several of reasons;
1. Because we like to run everything dry sump for motorsport, we simply put an extra lug on the front of the sump pan and you have the ideal mounting position for a crank sensor.
2. This part of the engine being furthest forwards makes a nice stable position for the shortest possible mount which keeps the sensor stable. If the bracket gets longer, it would become a bit like a ruler being pinged over the edge of a desk and the bracket and stabiliser required to prevent this becomes very hefty. I have seen brackets on some engines over 13mm thick vibrate just like a ruler at specific rpms, which causes the ECU to miscount the time between teeth on the trigger wheel.
3. You don’t necessarily have to move the trigger wheel, you just instruct the ECU of the new position of the sensor. The only problem with this is that you have to calculate it carefully and then check it with a strobe.
4. The problem with mounting the sensor anywhere else in the 360-degree circle of the crank trigger wheel is where do you mount it as you have to miss cambelts, alternator belts and potentially oil fittings, then you also have the length of the bracket which we have already gone into. All of which adds to the complication.

For those engines that have to be wet sump due to regulations, we always used the tin sump pans. We fabricated two steel plates which were welded to the sump vertically and spread apart sufficiently to bolt and alloy block between them that would hold the crank sensor in the same way it does on the dry sump version. We would always make the block slightly too close so that the sensor could be shimmed away from the trigger wheel to give the optimum setting rather than aiming for the optimal gap and potentially ending up with something that was too big. Unfortunately these were only ever fabricated in the workshop and no drawings were ever done or photos taken because it was over 25 years ago.

Please see our Technical Support Section for free technical advice about crank sensors.

Question:

I have a Caterham with a Cosworth engine, is there anything special about this calibration with respect to TPS, as it relates to voltage sweep?

Answer:

For some reason, Cosworth in their wisdom decided to wire their throttle position sensors backwards. The voltage actually descends as the throttle is open instead of increasing. MBE wrote some special software to invert the input voltage. You need to add a panel called ‘Throttle Angle Increasing’. The throttle sensor would output a voltage of just under 5v when the throttle is closed and approximately 0.5v at WOT, this value then hits the input pin of the ECU and the setup in the ECU has been set up to invert it, so the voltage rises as the throttle opens. This corrected voltage, which is throttle angle increasing should always show the voltage rising as the throttle is opened. The only time the throttle angle increasing would show the wrong value is if the direction of the throttle pot within the software is set up the wrong way round for the wiring that has been used on your particular application.

Question:
How do we fit the crankshaft sensor? We cant see anything to attach a bracket to so we can fit it so it points upwards.
Alternatively, is it possible to rotate the trigger wheel either to one of the other possible positions around the pulley to enable us to mount it elsewhere?

Answer:
We mount the crank sensor at 6 o’clock on the engine is for a several of reasons;
1. Because we like to run everything dry sump for motorsport, we simply put an extra lug on the front of the sump pan and you have the ideal mounting position for a crank sensor.
2. This part of the engine being furthest forwards makes a nice stable position for the shortest possible mount which keeps the sensor stable. If the bracket gets longer, it would become a bit like a ruler being pinged over the edge of a desk and the bracket and stabiliser required to prevent this becomes very hefty. I have seen brackets on some engines over 13mm thick vibrate just like a ruler at specific rpms, which causes the ECU to miscount the time between teeth on the trigger wheel.
3. You don’t necessarily have to move the trigger wheel, you just instruct the ECU of the new position of the sensor. The only problem with this is that you have to calculate it carefully and then check it with a strobe.
4. The problem with mounting the sensor anywhere else in the 360-degree circle of the crank trigger wheel is where do you mount it as you have to miss cambelts, alternator belts and potentially oil fittings, then you also have the length of the bracket which we have already gone into. All of which adds to the complication.

For those engines that have to be wet sump due to regulations, we always used the tin sump pans. We fabricated two steel plates which were welded to the sump vertically and spread apart sufficiently to bolt and alloy block between them that would hold the crank sensor in the same way it does on the dry sump version. We would always make the block slightly too close so that the sensor could be shimmed away from the trigger wheel to give the optimum setting rather than aiming for the optimal gap and potentially ending up with something that was too big. Unfortunately these were only ever fabricated in the workshop and no drawings were ever done or photos taken because it was over 25 years ago.

Please see our Technical Support Section for free technical advice about crank sensors.