tomwood

Right, finally got to the bottom of this one and now I feel like a right numpty. i checked all relays and all were fine. Thought I’d do another check of all the fuses, something I thought I fully checked first time round and would you believe it I found a blown one. I can only assume I pulled every fuse apart from the one that mattered!! anyhow, fuse swapped and switch re-attached and it’s all good again. interestingly, having had a good look over the wiring diagrams and fuse layout for my car in the handbook, I can confirm that the fuse layout is completely different on mine to what is shown in the handbook. I also have 6 relays when the handbook says I should have 5. A bit of a mystery! thanks for the help, Tom

Hi Chris, I’ve found it and have sent you a PM, regards Tom

I agree, your logic sounds good to me. It probably is the sender but would be good to know that before you have to fork out for a replacement. i replaced mine for a manual OPG a few months back. Pretty sure I still have the sender and pretty sure it’s the same as the one you’ve posted. I’ll take a look tomorrow for you and let you know. You’d be welcome to try it out if I’ve still got it and work out if it’s that or something else. Tom

Hi Charles, indeed, I’ve checked that either supplying a direct live feed from the battery or sending a live feed from the battery down the wiring from the switch results in the horn sounding so I just have no power coming to the switch. i will aim to test that at the weekend and see if I can trace the issue. Tom

Here’s the other end of that purple/yellow wire where it attaches to the horns. This is the only wire running to them so it looks as if the switch simply supplies a single 12v live to them both.

Ok, so have narrowed it down a bit. have confirmed that the horns are not faulty. If I connect a positive feed from the battery directly to them then they both sound. i have also checked the wiring that runs from the back of the switch to the horns for continuity. In the image above, the top wire (purple / yellow) runs all the way to the horns. If I connect this direct to the battery then the horns also sound so that wire is good. The other wire (solid purple) is, I assume, the positive feed coming from the relays? regarding the relays, I pulled all of the ones that sit behind the fuses in the passenger foot well and re-plugged them in again. I assume this is all of the relays? Any idea which one is used by the horn? I defo have some battery problems as well. It would appear my second banner in 5 years needs to be replaced again as it was unable to start the car despite having been on a conditioner. That said I don’t think it’s that given I could get the horn to sound when connected directly unless... low voltage/current would stop the relays from working correctly, could that be a factor? Tom

Thanks guys, great suggestions. Will investigate and report back, Tom

Did it feel like it was kangarooing when you had your foot to the floor? i had something similar happen on my duratec shortly after I bought it. Turned out to the HT leads. I disconnected each cylinder, disconnected every other connector I could find and reconnected it all. Never had a problem since. Worth a go. Tom

Hi all, car went in recently for its MOT and, to my annoyance, it was found that the horn had stopped working and needs sorting. things I have already ruled out: - the switch - I disconnected and completed the circuit with some improvised wiring - still nothing - fuses - pulled them all out and they are all fine my banner battery has been playing up recently and is clearly in need of replacement which I will be doing later, this might solve it but doubt it. what else could I check or do to help diagnose the issue. What’s the quickest way of checking that the horn itself isn’t faulty? any assistance much appreciated, Tom

Try an ester synthetic 5w40. I have been using Fuchs pro S in that spec for 5 years and it’s been great. Same engine spec as yours.

iPhone 7 with an app called ‘Soundcheck’

I thought I would resurrect this thread as a previous poster. Since my last messages on this, I have managed to source (thanks James) a carbon Track day air filter and am also now in possession of a new 750mm Raceco silencer which came pre-packed with filling. Recap on car config = R400d, RBTB's, Raceco 750mm exhaust + Decat pipe I was at Silverstone yesterday which thankfully had barely any noise restrictions so it was a nice chance to try out the various configurations without fear of getting black flagged. Unfortunately they weren't bothering to do any static tests so was unable to get a reading for this. For those that know the circuit, the configuration is such that as you round the last corner coming onto the pit straight you are at full throttle and conveniently my passengerfor the day was able to stand right at the point at which I was hitting max revs in 3rd and looking to change into 4th. We took the opportunity to do some basic measurements using an app on his phone and whilst hardly scientific, it gives some basic evidence as to the effectiveness of the track day air box versus the open air filter it replaces. He was standing on the pit wall, probably about 20m distance from where I was passing him. Admittedly the wall itself probably means the sound is reflected off the wall somewhat so the reading may be slightly higher than would be detected by a typical noise meter. We also have to consider the accuracy of his iPhone App which I suspect may have been over-reading by a few DB but nonetheless, some info below. Here are the results and also my perceptions from within the car on what was an extremely hot day (30 degrees Celsius and bright sunshine): Track day airbox was a little quieter (about 1db) as measured on his phone. 103DB drive-by recorded with open filter, 102BD recorded with Track Day Air box The tone of the exhaust note is a little more aggressive with the open filter in place but marginally so. Whilst the tone is somewhat different and noticeable from within the car, noise levels do feel very similar which seems to back-up the data as taken on the phone In terms of performance I was unable to detect any discernable reduction in performance after I switched from the open filter to the track day one. Bearing in mind that it was about as hot as it's likely to get here in the UK I think that bodes well for the track day air box. My suspicion is that there is considerable air movement within the engine bay when you are traveling at speed which probably negates some of the concerns in terms of this configuration sucking in hotter air from inside the engine bay in comparison to ambient air temps but that's just a guess on my part. I would be very interested to see a dyno plot comparison of the 2. The performance hit could well be there and I was simply unable to notice out on trackTom

Thanks for the replies gents and sorry for the slow response, I was fortunate enough to be at Silverstone yesterday so a good chance to get some sample data whilst running on the GP circuit with, lets face it, some of the hottest temperatures we are likely to get here in good old Blighty. After 30 mins of running, the oil temp peaked at a steady 90 degrees as indicated on the gauge. It held firm there and didn't rise over this level. I was physically melting under the conditions but the car held-up brilliantly. I hadn't appreciated until Scott mentioned it that this temperature reading, as taken from the tank, is post-cooling so an allowance needs to be made as suggested. If 15 - 20 degrees should be added then this suggests I'd have been running in the 105 - 110 degree range in terms of oil exiting the engine. So I think the gauge is probably working exactly as it should, I simply hadn't realised it was taking the reading after the oil is cooled. Regards Tom

Am interested to find out what other people are measuring their oil temps to be on cars with a similar setup. Spec is R400d with roller barrels and dry sump. I have an oil cooler fitted as well as the standard ford modine. i have recently carried out the tried and tested switch mod that allows me to switch between water/oil temp using the existing coolant temp gauge. My oil temp sender is in the dry sump tank and was fitted by Caterham so assumed to be the standard temp sender that they sell. since doing this mod, even in warm conditions such as we had yesterday I’ve yet to measure more than 80 degrees or so and this was after a 2hr drive up the M40 so fully warmed up. Does that sound correct? interested to hear what others are getting: - under normal road driving - while out on track on a hot day Essentially I’m trying to work out if the reading I’m getting on the gauge is accurate and representative or whether the actual oil temp is likely higher than is being indicated on the gauge. Tom

It’s either in the block itself or in the filter housing, can’t remember which but it’s not remotely fitted in a hose. mines 5 years old and has never given me any issues. Tom

Hi Shane, Mines a supersport R but same configuration as yours and I can confirm that is the sender that I just took off mine and indeed it’s located where you suggested, next to oil filter. My sender was working great when I removed it, I’ve simply decided to switch to a mechanical oil pressure gauge instead which are more accurate, faster reading and generally considered to be more reliable. if you haven’t already bought a new sender from CC then perhaps consider going for a mechanical one instead? Price wise a new sender from CC looks to be about £85 which is about the same as going for a mechanical gauge / sender combination from someone like Think Automotive. Having made the switch I’m really pleased with it and its defo better than original setup. Alternatively, if you want to stick with your current sender arrangement then send me a PM if you’ve not bought a new one already. We can perhaps work out a deal on my old one if you’d like. regards, Tom

Interesting, I’ve always put Fuchs Pro S into mine which is also a full Ester synthetic oil. 5w40 has always been my choice and I’ve found it to be excellent. As you say they seem to be more heat tolerant which arguably makes them more forgiving for track use. Are you implying that the nanodrive oils are more special (extra BHP) than other ester synthetics or merely that they are better than the cheaper synthetic oils, which, as you suggest are quite often mineral oils with additives then marketed as synthetic? Tom

Hi Peter, I went through this thought process myself recently. I’m not familiar with the 620 gauges but there’s a chance you can apply that outlined below on yours too. I took out the digital oil pressure gauge completely and swapped it for a mechanical one + associated sender. Straightforward to swap. I bought all the parts from Think Automotive. I now have a faster acting more accurate gauge for oil pressure. for oil temperature I went with the tried and tested approach of using the existing coolant gauge, rewiring it with a switch so that I can flick between coolant temp / oil temp depending on which way I’ve flicked the switch. It’s an elegant solution and requires little rewiring once you’ve worked out how to do it. suggest you read this previous forum topic for more background reading but specifically the last post from me which was a follow-up to the discussion after I finished the modification and confirms how to wire it up complete with a diagram that can be followed. If it’s too small (our club server resized it) drop me a private mail and I’ll send you the original. https://www.lotus7.club/forum/techtalk/water-oil-temp-gauge-switch-mod-advice-needed regards, Tom

Still on the hunt if anyone knows of one for sale anywhere? thanks Tom

Hi all, if anyone has either of the carbon air boxes for a duratec car that they’d be willing to sell i’d be very interested. This is to cover the standard Caterham roller barrels. I’d consider either of the types available, open or under bonnet type. Thanks Tom

I've been running with -2.5 on mine for the last few years. Just switched over from CR500 to ZZS. Can't speak for the ZZS yet as its too soon but I wore out the CR500s from new with that configuration and I found the wear to be reasonably even. It's been a great setup on the track and I can't say I've found it an issue on the road. How have people got their tracking configured to go with it? I'd have to go back and check the paper work but pretty sure I set mine up to be ever so slightly toe out. 0.5 degrees or thereabouts if I remember correctly. Turn in on track is good and I've never had problems with understeer. Tom

Very interesting, thanks James. It seems the plot thickens then. have you had your car mapped at any point James? i was thinking I was going to have to go for the under bonnet one on my r400d but given what you've now said I may re-evaluate. One would also imagine mine would be a bit quieter than yours anyway given it doesn't Rev out quite as much as your r500. Tom

Ah ok, interesting. Thanks for clarifying. so in which case we know that in all likelihood, if you were to switch to the other air box arrangement then you'd get the noise down to an acceptable limit but at the expense of some performance. I suppose the big question is, which is likely to reduce performance less, the revised under bonnet air box or an extended exhaust. ive not seen the exhaust arrangement you've described, sounds novel! I had envisaged that you'd meant extending the pipe work and running an extra (smaller) back box at the rear of the car rather than over the top of the raceco. i guess the issue you'll have with that is that, although it's £240 for the extra silencer, you'll have to have some custom fabrication work to join the new silencer to the raceco which will probably double the cost and make it more expensive than switching the air box over. Furthermore, I assume you'd have to cut off the rolled edge that's on the end of the raceco exhaust at the moment which might make it look a little odd when you're not running the additional silencer. its hard to know which is least likely to reduce the performance. I'm inclined to think the additional silencer may be least damaging to performance but that's just a guess. the 620r runs that extra silencer successfully enough although I guess that's forced induction so we aren't exactly comparing apples with apples I suppose. what diameter raceco did you end up getting? Is it the 63mm or 70mm inlet? i wonder what diameter the pipework is on the extra silencer you refer to. Tom

Ah, I stand corrected, I found it. James/Chris, are you both using this type of air box then? https://caterhamparts.co.uk/other/2812-air-filter-cover-race.html?search_query=Carbon+race+intake&results=346 Tom

James, am I right in thinking you don't have this style one then? https://caterhamparts.co.uk/other/4649-track-day-airbox-r500-duratec-2008.html?search_query=Airbox&results=21 i know Caterham used to sell one that they referred to as the 'race type' but I can't seem to find it on the parts site anymore. That one exited the bonnet and simply had a slit around the circumference of the oval that came out of the bonnet. I assume it's that one you've got? again, question for James. Has yours been remapped at any point? I do wonder if that's worth considering in Chris's case. I suspect that the lovely pops and bangs on the overrun don't help with noise. I wonder if some of this can be dialled out by running a customised map rather than the generic Caterham one? Tom