DW199

I torque to 85Nm before a track day, then ensure they are at 75Nm when hot after coming off the track. What is the reason for the lower torque when hot?

I see your point. I had assumed the change in resistance with temperature was more linear. It would be useful to log the temperatures to see how far below 60C they go in normal operation. If only a few degrees of faked increase was required, then a 5 -10K resistor might be sufficient without affecting the cold end of the curve too much. If it was mine I would probably do a few experiments.

Would it be possible to connect a resistor in parallel with the temperature sender? This would have the effect of raising the temperature that the ecu is "seeing" so keeping it running in closed loop mode even if water temp is a few degrees lower than 60C. It would be considerably cheaper than the plumbing mod.

It would be useful to know if the car is reaching normal operating temperatures. Assuming it has an MBE ecu, do you have access to easimap? I purchased the adapter to try to sort out my poor running problems and set the tps correctly. You are welcome to use mine if you fancy a trip to the south coast.

What is the impedance of your injectors and what is specified for the ecu? I know of one person who fried an MBE ecu on a Westfield by using low impedance injectors when the ecu was expecting high impedance.

You are correct. I have just checked on the car and the recent set are indeed LP507 CP FG. I have done one track day with them fitted and they seemed fine.

#11 That's interesting. What do they supply? The Caterham parts website still lists them and the photo is of 507CC pads. I purchased mine about 6 months ago but only fitted them recently.

One thing to bear in mind when changing brake pads is the requirement for pads to be E marked for road use. It is possible that using non E marked pads could cause problems with insurance in the event of an incident, although I have never heard of a case so probably a theoretical rather than real risk. My car is ex Academy and had Mintex 1144 on the front and Delphi LP507 on the rear. Since the brakes seem to work perfectly cold or hot, when I replaced pads recently I decided to stick with the E marked solution that Caterham offer as an option for my car. The Delphi pads from Caterham are marked CC whereas from other sources they seem to come marked as CP. I have no idea whether there is a difference between them.

Bear in mind that I have a Sigma engine with a single throttle body so the problem and solution for Jenvey throttle bodies may be different. I believe Oilyhands is Dave Andrews so I would definitely follow his advice. if you take a look at his web site http://www.dvapower.co.uk/ the section on fitting Jenvey throttle bodies shows an M6 washer on each side between the tps and throttle body to avoid binding.

I have just tried it again using some thick strong flat washers under the screw heads to spread the load. However hard I tried I couldn't cause the binding. I removed the washers, tightened the assembly again and the binding returned. I am therefore reasonably confident that the cause of the problem was distortion of the tps body as a result of the screw heads bending the cover plate when overtightened.

I don't think it is necessarily that simple. I have just performed an experiment with the tps that I removed from the car. I assembled the tps on the bench sandwiched between the cover plate and spacer. I used some flat washers to spread the load on the spacer and then tightened the whole thing up using a 6cm long 3mm allen key. At light to moderate tightness, rotation of the tps remained free. As I increased the tightness, it started binding at the full throttle end of travel. Increasing tightness more caused stiffness throughout the range of travel similar to what I was feeling when the tps was mounted on the car. I think what is happening is that the relatively weak cover plate is being bent by the screw heads as they tighten up. This seems to distort the body of the tps causing the binding. One way to potentially prevent that from happening would be to assemble the tps with the spacer between the cover plate and body of the potentiometer. This would spread the load better and would hopefully prevent the binding. There is another experiment that needs to be done.

That's an interesting observation. The Jenvey TP1 kit included a spacer and cover plate. Do you fit the spacer between the tps and throttle body or between the tps and cover plate? I didn't fit the spacer that was supplied with the kit as one hadn't been used originally.

To be fair to them, they did replace the catalyst and the throttle stiffness was quite subtle. I can't be absolutely certain which of my changes solved the problem. Possibly more than one could have contributed. I was contemplating spending money on a rolling road session and re-map, so decided to fix all the simple things that could be the source of the issue before going to that expense. It was also an interesting educational exercise to use easimap and log the engine data.

To update this thread, Caterham replaced the cat and air filter and I collected the car. It seemed the same on the road but I had a track day booked at Goodwood so took it there for more thorough testing. It was possibly slightly better but still rough at light to moderate throttle around 3 - 4000 rpm. I was a bit disillusioned with it and Caterham at this point and contemplated selling the car. It would have to go to a dealer as I couldn't sell the car privately in this state with a clear conscience. Then I spoke to Steve Greenald of Two Steves fame. He seemed interested in the problem and after I had purchased the MBE can adapter and installed easimap on my laptop provided me with an ec2 setup file that was appropriate for the 959 ecu fitted to my car. He looked at the log files and made a few suggestions. It was at this stage when I was operating the throttle pedal by hand, crouched over the side of the car peering at my laptop, that I realised the throttle was quite stiff and "sticky". I disconnected the cable and operated the mechanism at the throttle body, which was very stiff. I loosened the tps and the action of the throttle suddenly felt free and normal. Clearly the tps had been overtightened or misaligned. The cover plate had been bent by the screw heads. I fitted a new tps, being very careful to get correct alignment and not overtighten. New spark plugs went in, I sealed the leak at the 4:1 collector with Permatex Ultra Copper sensor safe sealant and replaced the lambda sensor. I checked for vacuum leaks on the induction side but couldn't find any. I then spent ages setting up the throttle stop and tps position. On the road the car has been transformed. It now works as I would expect. There is no hint of the rough running, the kangaroo effect has gone, idle is steady and overall I am really pleased with it. It is a shame it didn't run like this when I bought it. I said at the time that I couldn't believe they all ran this badly but I was assured that they do. It's not true. I am glad I persevered. **** Notes Caterham were out of stock of the tps, plugs and lambda sensor so I purchased from alternative sources for around half the price. Plugs NGK TR5B-13 from Euro car parts £12.36 for the set. TPS came in a bag labelled Jenvey TP1. It is a Colvern CP17 and appears identical to the original. The lambda sensor was a problem. The Bosch catalogue doesn't include 0258006600 which is the type no on the original sensor. I fitted a Bosch 0258006155 This has a similar body to the 600 but slightly fewer larger holes at the business end. The strain relief is slightly different, the lead is about 2cm longer but the wiring and connector are the same. It was about 1/3 of the cost of the Caterham specified part and seems to work.

An engine needs compression, fuel and a spark to run. Sudden compression loss in a previously running engine could be caused by cam belt failure. I don't think it is common on the Sigma for this to happen but very easy to rule out. To check, remove the oil filler cap and whilst turning the engine on the starter the camshaft should be seen to be turning. Fuel is unlikely to be the cause as you say the plugs are wet. Can you hear the fuel pump priming when you switch the ignition on? Spark sounds the most likely culprit. I have an old school, very dim, neon timing light which I purchased in the mid 70s which I use as a spark checker. There are specific spark testers available. Halfords will probably stock one for around £10. You just connect it between one of the plug leads and sparking plug and see whether it flashes when the engine is cranking. It is worth having something to perform this simple check as it can save hours of fruitless fiddling when an engine won't start.

I found this installation manual quite helpful Schroth installation manual

CC have no cats or decat pipes in stock and don't know when they will receive any. Apparently it is not totally unheard of for a cat to fail in a race/ex-race car due to 'hard use'. They will look for any underlying cause when the car has a properly functioning exhaust system. All a bit frustrating.

You are right, cats aren't cheap looking at the price on the Caterham parts site. I'm glad they have agreed to cover this under warranty. The car did the Academy followed by a few track days so I think the mileage is about right. I don't know whether the cat is the original. I will ask CC the relevant questions when they confirm the availability or otherwise of a replacement.

The car went back to Caterham Gatwick under warranty last week. Apparently the problem is due to the catalytic converter breaking up. The car has only done 3.5k miles so I am slightly surprised. It will be interesting to see how it runs after the cat is replaced.

Fuel system status can be displayed in real time on the phone. I'm not sure whether the software I am using (Car Scanner ELM OBD2 for ios) allows this to be logged. The right hand side of the lower trace where the revs are held constant at around 2500 shows an odd shaped trace for the O2 volts and trim. I am reasonably confident this is a sampling frequency artefact. The car is going to be returned to Caterham Gatwick next week for investigation and fix under warranty. Previously they couldn't replicate the fault and I didn't realise that so much useful information was available and could be logged with cheap OBD tools. At least I now have some objective evidence of a fault rather than it being caused by my incompetent driving.

Tom_Arundel - The excessive driveline shunt that afflicts these cars certainly exacerbates the fault but I don't think it is the root cause. I was careful to brace firmly against the side of the footwell to minimise that effect. The tps has been reset several times by Caterham Gatwick which solved the poor idling and immediate off idle progression problem. I think this is a different fault. GulfSeven - That's interesting. There is a slight hum from under the dash when the ignition is on. I will investigate further. The collector seems to be an interference fit. I can't see any evidence of sealant. aerobod - The thing that is puzzling me is that the short term fuel trim does not seem to have responded to the low lambda voltage. Is that what you would expect with a faulty lambda sensor/exhaust leak? StevehS3 - I have a tube on order!

Sigma engine in 2019 Academy car. The car runs very poorly on light throttle at around 3500 rpm. It has done this ever since I bought it but during my last track day at Goodwood, in the wet the car was almost impossible to drive. It feels as though the throttle is pressed and released once or twice a second. The traces above are from an OBD scanner and logged on my phone. In the centre of the trace the lambda sensor voltage goes low without any obvious fuel trim response. The tps position seems quite noisy. Is this behaviour as expected when the rpm is betweem 3200 and 3800? There is a very slight exhaust leak at the 4-1 collector. Could that account for the behaviour? Any suggestions welcome. Chart below shows the traces with the car stationary at different rpms

Yes please pm sent

That seems quite likely. An MBE 9A9 ECU has a connector with pins A001 - A081 and B082 - B121 which matches the A and B series in your clip. I very much doubt it is a 9A9 though as they cost £2.5k from SBD.

How important is ECE Regulation 90 compliance if the car is to be used on the road? Does it still apply in the UK and if so, does it apply to Caterhams?