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Tach misreading on 420R.


KnifeySpoony
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My 2021 build 420R still has a misreading tachometer. Apparently there are 2 possible calibrations, according to Caterham. Unfortunately, one reads high, and one reads low. With one calibration, the tach reads high by about 50%. With the other calibration, the tach reads low by about 1/3 (ie with actual RPMs at 3000, tach shows 1000). I have read about older Caterham tachs having internal dipswitches, but my understanding is the newer ones don't. I am still working this issue out with Caterham, but has anyone heard of this issue?

 

Thanks

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12 hours ago, KnifeySpoony said:

I hadn't considered that the ECU hardware itself could be faulty. Caterham mentioned me sending the tach itself back...

 

When I read your first post I assumed you were getting the engine speed from the ECU and that is how you knew that the tach was wrong.  Maybe get a copy of Easimap and the proprietary cable and see what the ECU is reporting compared to the tach?

Edited by Pokey
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30 minutes ago, Pokey said:

 

 

When I read your first post I assumed you were getting the engine speed from the ECU and that is how you knew that the tach was wrong.  Maybe get a copy of Easimap and the proprietary cable and see what the ECU is reporting compared to the tach?

The "real" engine numbers I am quoting are from easimap.

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If the ECU is internally showing the correct RPM on easymap it sure sounds like the pulses per RPM setting for the tach output in the ECU is off. I had the same issue a few months ago when I swapped out the Caterham ECU for SBD one - the default setting for the tach output was 1 pulse per RPM and the tach was showing 25% of the RPM. It was fixed by changing the setting to 4 pulses per RPM. Not sure what can be done with what you have.

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Does Easimap allow you to see all the ECU settings or just a subset?  If you have full read access it would be good to verify the tach output setting was configured correctly at the factory.

 

-John

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I am aware of the 1:4 pulse issue - I have been told that there are only 2 possible settings for this (from Caterham), and i have tried both of these settings. However, neither are correct. It seems my tach is off by a different factor (ie not 1/2 or 4x the correct reading). RE: easimap - it does show a bunch of different sensor info, but I don't have full access to each setting. I can update the ECU software but it just replaces the entire software file with ones provided by Caterham. 

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If Caterham can't resolve this issue, then that will probably be what I will do. I was already considering going to an unlocked ECU so I could do a proper dyno tune, as I've heard that might unleash some more potential in the engine. However, it runs great and pulls hard, so haven't been motivated to do so.

 

 

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