KnifeySpoony Posted January 3, 2022 Share Posted January 3, 2022 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 Link to comment Share on other sites More sharing options...
sf4018 Posted January 3, 2022 Share Posted January 3, 2022 No, but I have a spare stock Caterham 420R ECU (2018) if you want to borrow it to see if the ECU is the issue or not. Link to comment Share on other sites More sharing options...
KnifeySpoony Posted January 4, 2022 Author Share Posted January 4, 2022 I hadn't considered that the ECU hardware itself could be faulty. Caterham mentioned me sending the tach itself back... Link to comment Share on other sites More sharing options...
Pokey Posted January 4, 2022 Share Posted January 4, 2022 (edited) 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 January 4, 2022 by Pokey Link to comment Share on other sites More sharing options...
KnifeySpoony Posted January 4, 2022 Author Share Posted January 4, 2022 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. Link to comment Share on other sites More sharing options...
sf4018 Posted January 4, 2022 Share Posted January 4, 2022 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. Link to comment Share on other sites More sharing options...
JohnCh Posted January 4, 2022 Share Posted January 4, 2022 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 Link to comment Share on other sites More sharing options...
KnifeySpoony Posted January 4, 2022 Author Share Posted January 4, 2022 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. Link to comment Share on other sites More sharing options...
sf4018 Posted January 5, 2022 Share Posted January 5, 2022 This is one reason I swapped out the ECU. Link to comment Share on other sites More sharing options...
KnifeySpoony Posted January 5, 2022 Author Share Posted January 5, 2022 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. Link to comment Share on other sites More sharing options...
KnifeySpoony Posted January 28, 2022 Author Share Posted January 28, 2022 I just became aware of this document: https://www.caigauge.com/documents//product-instructions/tachometers/pil055-iss2-279.pdf I thought that new Caterhams don't have the switches but a recent thread on blatchat suggests they do: https://www.caterhamlotus7.club/forum/techtalk/360-rev-counter-reading-approx-half-actual-rpm Can anyone confirm the proper dipswitch settings? Link to comment Share on other sites More sharing options...
BlakeJ Posted January 29, 2022 Share Posted January 29, 2022 I had the low-reading tach issue, tried changing the dip switches, didnt work,and ultimately had to have the ECU reprogrammed, after which all was well. Link to comment Share on other sites More sharing options...
KnifeySpoony Posted January 29, 2022 Author Share Posted January 29, 2022 3 hours ago, BlakeJ said: I had the low-reading tach issue, tried changing the dip switches, didnt work,and ultimately had to have the ECU reprogrammed, after which all was well. Do you recall what the proper dipswitch settings are? Link to comment Share on other sites More sharing options...
BlakeJ Posted January 29, 2022 Share Posted January 29, 2022 Switches 1 and 2 on, 3 through 7 off, and 8 on, if I recall correctly. Link to comment Share on other sites More sharing options...
BlakeJ Posted January 29, 2022 Share Posted January 29, 2022 (edited) Here's a link to the manufacturer of the tach,with instructions. http://www.caigauge.com/product-instructions Edited January 29, 2022 by BlakeJ Link to comment Share on other sites More sharing options...
KnifeySpoony Posted January 30, 2022 Author Share Posted January 30, 2022 Thanks! I will play around and see if I can fix it. Link to comment Share on other sites More sharing options...
KnifeySpoony Posted January 30, 2022 Author Share Posted January 30, 2022 OK, did your settings and it seems to have fixed it actually. Maybe reading just a couple percent high compared to numbers in easimap. I can't believe that Caterham is unaware of the dipswitch settings. They had me purchase the easimap cable in order to change ECU tunes when it wasn't necessary at all. SMH. Link to comment Share on other sites More sharing options...
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