rich_sutcliffe Posted January 27, 2022 Share Posted January 27, 2022 Hi all,I have just finished my 360R build, but when the engine was started for the first time, the rev counter was reading roughly half of what it should be reading across the rev range. Does anyone have any bright ideas please?My IVA is booked for Tuesday. There isn't time to take it to Caterham for the PBC as the final missing parts from the kit only arrived a few days ago. Eric at Millwood is in the process of checking the build for me, but if it ends up being a warranty job it will need to go to Caterham. Do you think it will pass the IVA?Many thanks,Rich Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted January 27, 2022 Member Share Posted January 27, 2022 Engine starting easily and running smoothly?And the rev counter is steady... not bouncing or flicking?All other electrics working OK?Do you have a multimeter and the appropriate wiring diagram?Jonathan Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted January 27, 2022 Member Share Posted January 27, 2022 Let's start with the easy bits.Are there any settings switches on the back of the rev counter, and if so how are they set?Check the instrument earthing point.Check the engine and ECU earths.Wiggle the ECU wires while it's running and see if that affects the rev counter display.Jonathan Link to comment Share on other sites More sharing options...
rich_sutcliffe Posted January 27, 2022 Author Share Posted January 27, 2022 Thank you, will try these things tomorrow.I have a multimeter and I know a bit about electronics, but I don't have a circuit diagram.The engine is running smoothly. The rev counter needle sweeps correctly from min to max and back when the ignition is switched on. All other electrics seem ok. The rev counter doesn't bounce - it just always reads about half of the expected value, which is why I hoped it might be a setting / mapping problem and therefore a quick fix. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted January 27, 2022 Member Share Posted January 27, 2022 Please send me a Private Message with your email address.Jonathan Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted January 27, 2022 Share Posted January 27, 2022 The Caerbont / Smiths Tachometers since 2009 have used 8 dip switches to configure them, as per this table:It is likely that switch number 2 should be on instead of off. Here is the link to the full document: https://www.caigauge.com/documents//product-instructions/tachometers/pil055-iss2-279.pdf Link to comment Share on other sites More sharing options...
rich_sutcliffe Posted January 27, 2022 Author Share Posted January 27, 2022 Very interesting thanks, will check the dip switches and report back tomorrow. Link to comment Share on other sites More sharing options...
rich_sutcliffe Posted January 27, 2022 Author Share Posted January 27, 2022 Thinking about the dip switches a bit more, if the rev counter was configured for 1 Pulse Per Revolution, but was actually receiving 2 PPR from the engine, then wouldn't it read double the correct value? So in my case maybe it is set to 4 PPR (dip switches 10100001) and it is only receiving half the number of pulses that it is expecting. Will find out tomorrow! Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted January 27, 2022 Share Posted January 27, 2022 That would be correct Rich. Switch 3 would also have to be switched off and Switch 2 switched on to drop from 4 PPR to 2 PPR. Link to comment Share on other sites More sharing options...
ChrisC Posted January 28, 2022 Share Posted January 28, 2022 Have seen this before with a US 360 kit build. Dip switches where incorrectly set. Might be able to get a picture of my dip switches at the weekend. Also had a faulty tach on my 420 build, but that was because one of the warning lights didn't work. CC sent replacement via post. Link to comment Share on other sites More sharing options...
rich_sutcliffe Posted January 28, 2022 Author Share Posted January 28, 2022 So it turns out that the dip switches were set correctly, and swapping the rev counter for a known working one still gives half the expected reading. So it's pointing towards a sensor or ECU issue. Waiting for Caterham to phone me... Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted January 28, 2022 Share Posted January 28, 2022 There isn't any sensor for the revs, Rich. It is just a feed from the ECU on Pin 34 (white wire with black stripe going to Pin 8 on the tach, if Caterham hasn't changed the wiring lately). A number of things that may cause the issue:- change in MBE ECU programming, only fixable by Caterham with a new image- poorly crimped ground wire or loose ground terminal post either for the tach or ECU- need for a pull-up resistor or a faulty pull-up resistor between the ECU feed and 12V on the tach connection (this would only be needed if either an ECU or tach change in the signal requirements have been made by either Caerbont or MBE). Link to comment Share on other sites More sharing options...
rich_sutcliffe Posted January 28, 2022 Author Share Posted January 28, 2022 Thanks for explaining. The car is now going to Williams on Monday for them to investigate the ECU. Link to comment Share on other sites More sharing options...
rich_sutcliffe Posted February 2, 2022 Author Share Posted February 2, 2022 Problem fixed - the ECU wasn't sending enough pulses to the rev counter. Not quite sure why Caterham couldn't configure it correctly in the first place - they knew what combination of engine, ECU and instruments they were supplying. Yet more QC issues...In other news my IVA was canceled yesterday as the examiner has COVID :-( Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted February 2, 2022 Member Share Posted February 2, 2022 Thanks for adding the answer.Hope you're sorted soon.Jonathan Link to comment Share on other sites More sharing options...
wild bill Posted February 2, 2022 Share Posted February 2, 2022 interested in this thread as since rebuild i have the same issue. Nothing has changed in the ECU so it may be poor earth or resistor or switch settings. Does the tach need to be removed to check the switch settings? or do i have to invert myself with a torch? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted February 2, 2022 Member Share Posted February 2, 2022 I think that it would be difficult by feel.How about a smart 'phone pointing at the back while you look at the screen? Or used to take a photo?(But the gauges are easy to release.)Jonathan Link to comment Share on other sites More sharing options...
wild bill Posted February 2, 2022 Share Posted February 2, 2022 I'll give it a try when i get a free mo and see where i get to Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted February 2, 2022 Share Posted February 2, 2022 Re #14 Rich, it sounds as though Caterham has been changing some of the ECU characteristics. The MBE ECU has a setting under "Tacho pulses per cycle" for both the number of pulses (set to 4 on my non-Caterham ECU) and "Tacho duty cycle" set to 75% on my ECU, indicating the time the pulse stays "high" (+12V).On a locked ECU you can confirm the settings using an oscilloscope on the signal line while the engine is running and Easimap is displaying the revs to be matched to the pulses. Link to comment Share on other sites More sharing options...
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