Cam chain broken
Discussion
Track day at Bedford yesterday. Had a few problems with engine misfiring above about 5000 rpm caused by the connector into the ECU not being completely pushed into the socket.
Did 5 or so excellent sessions with no problems at all and then whilst decelerating the engine suddenly went completely dead. No warning, misfiring, surging or anything - just dead as though someone had switched the ignition off.
My first thoughts were that the ECU socket had come out completely, but it was fine. Checked for fuel and sparks, both present and correct. Lots of head scratching and a phone call to Ted at Powertec and it turns out that the valves are not moving at all when the engine is turned over
This is apparently because the cam chain has broken (a rare event according to Ted).
I do wonder whether the lap I did with the engine misfiring/backfiring in the morning may have done some damage to the chain that took the rest of the day to become a complete failure.
So, car back on trailer and drove up to Peterborough to drop the car off for him to look at. Chances are that when Powertec open up the engine there will be damage to valves, pistons and possibly the cylinder head. Bollocks!!!
Signs are that Radical ownership is going to be an expensive business. Guess that after two years of track days with Caterham 7's without a single serious mechanical failure I was probably due to have something like this happen.
Did 5 or so excellent sessions with no problems at all and then whilst decelerating the engine suddenly went completely dead. No warning, misfiring, surging or anything - just dead as though someone had switched the ignition off.
My first thoughts were that the ECU socket had come out completely, but it was fine. Checked for fuel and sparks, both present and correct. Lots of head scratching and a phone call to Ted at Powertec and it turns out that the valves are not moving at all when the engine is turned over
This is apparently because the cam chain has broken (a rare event according to Ted). I do wonder whether the lap I did with the engine misfiring/backfiring in the morning may have done some damage to the chain that took the rest of the day to become a complete failure.
So, car back on trailer and drove up to Peterborough to drop the car off for him to look at. Chances are that when Powertec open up the engine there will be damage to valves, pistons and possibly the cylinder head. Bollocks!!!
Signs are that Radical ownership is going to be an expensive business. Guess that after two years of track days with Caterham 7's without a single serious mechanical failure I was probably due to have something like this happen.
I managed to get my DL90 data logger to register RPM and used it for my last 3 sessions prior to the cam chain breaking. Went through this last night and during the 3 sessions the highest rpm recorded was about 7,600. in the last second prior of the final session the rpm leapt up to 15,000 virtually instantaneously for about a second and then just stopped. I assume that this must have been the cam chain 'letting go' as I was decelerating when the engine died on me. I just hope that the 15,000 recorded engine speed (if it really did run up that fast) did not do any damage. I expect that I will know by the end of this week and will keep you posted.
Andrew, thanks for your comments. I have my fingers firmly crossed too!
Andrew, thanks for your comments. I have my fingers firmly crossed too!
Andrew, I assume because your highest recorded rpm was only 7600rpm in the previous 3 sessions that you were still running it in ?
I,ve had my sr3 ( std 1300cc ) for nearly a year now and its completed 14 trackdays with the engine untouch apart from oil changes and a couple of sets of spark plugs, and thats been using the red shift light ( 10000 rpm ) most of the time.
I have since broken a timing chain in Spa a couple of weeks ago in my 1500 cc engine, which let go whilst flat in sixth, bent valves, pistons, cylinder head and block all badly damaged.
I was just wondering wether yours was a std 1300cc or did you go for the 1500cc ?
Is it possible that the peak 15000 rpm prior to it letting go was due to an early downshift causing the engine to over rev ?
>> Edited by daved6 on Saturday 24th May 10:16
I,ve had my sr3 ( std 1300cc ) for nearly a year now and its completed 14 trackdays with the engine untouch apart from oil changes and a couple of sets of spark plugs, and thats been using the red shift light ( 10000 rpm ) most of the time.
I have since broken a timing chain in Spa a couple of weeks ago in my 1500 cc engine, which let go whilst flat in sixth, bent valves, pistons, cylinder head and block all badly damaged.
I was just wondering wether yours was a std 1300cc or did you go for the 1500cc ?
Is it possible that the peak 15000 rpm prior to it letting go was due to an early downshift causing the engine to over rev ?
>> Edited by daved6 on Saturday 24th May 10:16
Dave,
I was rather surprised when I saw the data log showing max revs so low. I have tended to change up on the last light before green. As I am using the car for track days I try to be a lot easier on the engine than if I was racing, so short shift generally. If the data from the logger is correct then this would seem to be quite a bit earlier than it needs to be! I am not running the engine in by the way.
I am afraid that I really cannot think of any other reason for the revs apparently shooting up to 15k than me inadvertantly buzzing the engine with a change down too many. I must say that I am rather baffled by this because I certainly was not aware of the engine overevving - just stopping suddenly. But if the cam chain has broken then the indication of 15,000 rpm must have happened (I think) just before the chain broke. So I am inclined to think that this is the only possible explanation for what happened.
By the way, my engine is the 1300cc one.
I should hear from Radical next week. Just hope that I have not done as much damage as you experienced!
>> Edited by abailey on Saturday 24th May 18:03
I was rather surprised when I saw the data log showing max revs so low. I have tended to change up on the last light before green. As I am using the car for track days I try to be a lot easier on the engine than if I was racing, so short shift generally. If the data from the logger is correct then this would seem to be quite a bit earlier than it needs to be! I am not running the engine in by the way.
I am afraid that I really cannot think of any other reason for the revs apparently shooting up to 15k than me inadvertantly buzzing the engine with a change down too many. I must say that I am rather baffled by this because I certainly was not aware of the engine overevving - just stopping suddenly. But if the cam chain has broken then the indication of 15,000 rpm must have happened (I think) just before the chain broke. So I am inclined to think that this is the only possible explanation for what happened.
By the way, my engine is the 1300cc one.
I should hear from Radical next week. Just hope that I have not done as much damage as you experienced!
>> Edited by abailey on Saturday 24th May 18:03
Andrew,
Lets hope you get away lightly, to be fair my 1500cc wasn't built by Ted anyway, it was a second hand unit out of a written off bike which had done a warranted 1400 miles only, prior to me having it rebuilt and converting into a 1500cc.
I have heard from a number of people though, that the cam chain tensioner is the weak link in the engine.
Still I hope your enjoying the car anyway
Lets hope you get away lightly, to be fair my 1500cc wasn't built by Ted anyway, it was a second hand unit out of a written off bike which had done a warranted 1400 miles only, prior to me having it rebuilt and converting into a 1500cc.
I have heard from a number of people though, that the cam chain tensioner is the weak link in the engine.
Still I hope your enjoying the car anyway
Dave, thanks for your post. Fingers firmly crossed.
I have spent a couple of hours this evening looking at the the data analysis and more particularly reading the documentation for the DL90 Analysis Software. It looks as though the results I saw before had been screwed up by some parameters and filters being incorrect. I have now set these up properly and the results look much more sensible.
The 3 runs that I logged (around 15 mins each)indicated that I was consistently peaking revs at around the 9500 to 10500 mark. However, in run 1 and 2 I went over 10,500rpm once on each run. Run one had 3 seconds over 10,000rpm with the peak at 12,200rpm. Run two had 1.6 seconds over 10,000rpm with the peak at 13,200rpm. Both of these were during deceleration/braking.
On run 3 I did not exceed 10,560 rpm at all during the 13 min run. In the couple of seconds before the cam chain let go the rpm was climbing at normal rate from 1200rpm and then output stopped dead at 8000rpm.
So, it doesn't look as though an over rev in the last session was the cause of the cam chain failure. However, I guess that the chain may have been damaged either by buzzing the engine on each of the previous runs or possibly by the misfinring and backfiring caused by the ECU plug being slightly adrift when I first took the car out that day.
I must say that based upon my motorcycling experience I would have thought that the engine would be strong enough to deal with the very brief over revving that I described above. Or am I being unrealistic? I certainly feel that I will need to be very much more careful not to allow it to rev over the limit in future!
Do any of you have a feeling (or better still data) for how often (if at all) you take your engine over the limit and by how much? Did I get unlucky or is such a failure probable given that I took it so far over the limit?
I have spent a couple of hours this evening looking at the the data analysis and more particularly reading the documentation for the DL90 Analysis Software. It looks as though the results I saw before had been screwed up by some parameters and filters being incorrect. I have now set these up properly and the results look much more sensible.
The 3 runs that I logged (around 15 mins each)indicated that I was consistently peaking revs at around the 9500 to 10500 mark. However, in run 1 and 2 I went over 10,500rpm once on each run. Run one had 3 seconds over 10,000rpm with the peak at 12,200rpm. Run two had 1.6 seconds over 10,000rpm with the peak at 13,200rpm. Both of these were during deceleration/braking.
On run 3 I did not exceed 10,560 rpm at all during the 13 min run. In the couple of seconds before the cam chain let go the rpm was climbing at normal rate from 1200rpm and then output stopped dead at 8000rpm.
So, it doesn't look as though an over rev in the last session was the cause of the cam chain failure. However, I guess that the chain may have been damaged either by buzzing the engine on each of the previous runs or possibly by the misfinring and backfiring caused by the ECU plug being slightly adrift when I first took the car out that day.
I must say that based upon my motorcycling experience I would have thought that the engine would be strong enough to deal with the very brief over revving that I described above. Or am I being unrealistic? I certainly feel that I will need to be very much more careful not to allow it to rev over the limit in future!
Do any of you have a feeling (or better still data) for how often (if at all) you take your engine over the limit and by how much? Did I get unlucky or is such a failure probable given that I took it so far over the limit?
Andrew,
We would not normally expect to see peak RPM on downshift as high as you have experienced.
Certainly we would identify and draw the driver's attention to any over-rev above 11,000 RPM, and try and avoid its repetition.
The general pattern is for a maximum of 10,500 on downshift. We tend to aim for an upchange upper limit of 10,000, peak power deliver coming around 9,500.
Without seeing the RPM trace it is hard to tell 'how bad' your overrev was, but Run One sounds the worst, and would have caused some anxiety if we had experienced it.
I have no doubt that Ted will shed some more light on things, I have always found him to be very thorough, fair and helpful.
On a general note I would comment that the bike engine configuration of a Radical undoubtedly needs to be treated with more care than some conventional powerplants, but I would say that the most important area of care is the gearbox, hurried downchanges, and clutchless / flatshifting do damage the box.
We run some of the quickest drivers in the Radical championship, and they always use the clutch, preferring to conserve machinery rather than extract that last tenth.
I hope this is helpful.
Kind regards,
Alec.
We would not normally expect to see peak RPM on downshift as high as you have experienced.
Certainly we would identify and draw the driver's attention to any over-rev above 11,000 RPM, and try and avoid its repetition.
The general pattern is for a maximum of 10,500 on downshift. We tend to aim for an upchange upper limit of 10,000, peak power deliver coming around 9,500.
Without seeing the RPM trace it is hard to tell 'how bad' your overrev was, but Run One sounds the worst, and would have caused some anxiety if we had experienced it.
I have no doubt that Ted will shed some more light on things, I have always found him to be very thorough, fair and helpful.
On a general note I would comment that the bike engine configuration of a Radical undoubtedly needs to be treated with more care than some conventional powerplants, but I would say that the most important area of care is the gearbox, hurried downchanges, and clutchless / flatshifting do damage the box.
We run some of the quickest drivers in the Radical championship, and they always use the clutch, preferring to conserve machinery rather than extract that last tenth.
I hope this is helpful.
Kind regards,
Alec.
Alec, yes thanks, your feedback is very helpful indeed. Seems as though I will need to be much more careful to avoid the same sort of situation happening again!
I guess that it is just down to practice, technique and self control. I always use the clutch, change down one gear at a time and heel/toe each change. Think I may have to change my technique to brake hard to reduce speed before changing down at all.
I guess that it is just down to practice, technique and self control. I always use the clutch, change down one gear at a time and heel/toe each change. Think I may have to change my technique to brake hard to reduce speed before changing down at all.
Just spoke to Ted and the news is not great. Cam chain was broken and there is damage to around 6 valves, valve guides and the cylinder head. I have posted pdf's of the engine rpm for the last three runs. If anyone is interested you can download the reports at [url]www.ocula.com/radical[/url]
Picked my car up today. Ted reckoned that there were two chain link plates that had come adrift some time before the chain broke. These had scored the inside of the chain cover as they went around.
It also explains the high pitched 'tinkling' noise my engine made at idle which I assumed to be normal. The rebuilt engine does not make the same noise so I reckon that these plates were almost certainly adrift before I bought the car and it was only a matter of time (helped by me buzzing the engine) before the cam chain let go completely.
Anyway the invoice was not quite as big as I thought it would be (around £1,400 with the labour) so I cheered myself up by asking them to fit a rear undertray to keep help everything clean at the back and maybe buy me a 1/10th or so on the track!
Good to have the car back in the garage though. Having it 'signed up' and will be doing a corporate day next Tuesday with it. Can't wait to get it back out on the track.
It also explains the high pitched 'tinkling' noise my engine made at idle which I assumed to be normal. The rebuilt engine does not make the same noise so I reckon that these plates were almost certainly adrift before I bought the car and it was only a matter of time (helped by me buzzing the engine) before the cam chain let go completely.
Anyway the invoice was not quite as big as I thought it would be (around £1,400 with the labour) so I cheered myself up by asking them to fit a rear undertray to keep help everything clean at the back and maybe buy me a 1/10th or so on the track!
Good to have the car back in the garage though. Having it 'signed up' and will be doing a corporate day next Tuesday with it. Can't wait to get it back out on the track.
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