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.