The 'Maverick' Classic Porsche Forum and Classic Porsche Club for Porsche 356, Aircooled Porsche 911, Porsche 912, Porsche 914 & Porsche Replicas. 'We join for the cars but stay for the people'
What an interesting catch-up.
When I installed the dreaded Clewett twin plug system on the Lola's 3.2 many told me the leads had to be spaced apart everywhere.
This proved impossible, but i tried very hard to keep the lead off the engine.
I used another supplier that Magnacore. They were very hard work, so moved to another UK specialist at a fraction of the cost.
Still, you are all done now.
I hear very good reports of Mike Champion, I think he is a continuation of Bob Watson.
Always been reluctant to go to CG due to the cost, but never read a bad thing about them.
73T 911 Coupe, road/hillclimber 3.2L
Lola t 492 / 3.2 hillclimb racer
Boxster 987 Gen II 2.9
911hillclimber wrote: ↑Sun Jan 22, 2023 9:46 am
What an interesting catch-up.
When I installed the dreaded Clewett twin plug system on the Lola's 3.2 many told me the leads had to be spaced apart everywhere.
This proved impossible, but i tried very hard to keep the lead off the engine.
I used another supplier that Magnacore. They were very hard work, so moved to another UK specialist at a fraction of the cost.
Still, you are all done now.
I hear very good reports of Mike Champion, I think he is a continuation of Bob Watson.
Always been reluctant to go to CG due to the cost, but never read a bad thing about them.
Thanks for the contribution Graham. Agree that spacing the plug leads on a twin plug is impossible hence adopting larger diameter leads with more 'sheathing' around them. Mike did make some changes with respect to the loops and captives to guide the leads but essentially no change to the original routing.
As for CG they charge a fixed cost plus any consumables. Yes more expensive than you would normally expect but you are paying for the expertise.
All my clewett leads are clumped together and have been for the past 10 years or so. Saying that, clewett do recommend replacing all leads every 3 years , which I have still yet to do !
hot66 wrote: ↑Sun Jan 22, 2023 12:26 pm
All my clewett leads are clumped together and have been for the past 10 years or so. Saying that, clewett do recommend replacing all leads every 3 years , which I have still yet to do !
James, is your engine twin plug? According to MCE that is where potential issues occur rather than on single plug set ups. I also run Classic Retrofit spark boxes which may or may not make a contribution to the cross talk with its generous spark. For clarity the issue was only on the right hand cylinders where the plug leads are both longer and lack separation as they travel over the fan housing and through guide loops.
Yep, twin plug for years now and no apparent problems. It’s more the lower cables bundled into 3 on each side as they pass through the twin ware / seal .
My coil packs are mounted above the flywheel and cables fed from there
hot66 wrote: ↑Sun Jan 22, 2023 1:39 pm
Yep, twin plug for years now and no apparent problems. It’s more the lower cables bundled into 3 on each side as they pass through the twin ware / seal .
My coil packs are mounted above the flywheel and cables fed from there
Different routing to mine as I have the distributor
obviously where all the leads come from with six cables running over the fan housing crammed together. Your set up may be better at avoiding cross talk. You have a different manufacturer for the leads and possibly they are better insulated than the Magnacor offering?
911hillclimber wrote: ↑Wed Jan 25, 2023 4:19 pm
No cross sparking on mine despite all this spaghetti.
You simply cannot separate all the cables.
My cables are 8mm, and there are over 40 separaters on the engine...
Graham,
I originally had 7mm ignition leads and have now moved to 8.5mm. Agree it is impossible to have complete separation of ignition leads but MCE got the issue sorted with a larger diameter leads and some revision to the cable runs.
Firstly, thanks for the excellent summary of the recent works, Kirk, and glad to have been able to help out.
Regards the differences in sensitivity to 'spark jumping' when comparing these different types of ignition set-up, and to provide some additional context to Graham and James' experiences: I believe the Clewett system is a wasted spark system, therefore already firing plugs on the exhaust stroke as well as at compression. Depending on where in the firing sequence the potential for cross-talk occurs, this can render the issue of spark jumping from cylinder to cylinder non-problematic, as it's already giving additional unnecessary sparks 'by design', and if the leads allow it, may be able to afford to literally waste (or more accurately, inadvertently supplement) spark energy where a conventional distributed system can't. Double this up to twin-plug, wasted spark, and there is plenty of spare spark to go around.
Also worth noting that whereas a single-plug distributed system on a 6-cyl engine has no spare sparks to give away, a twin-plug system (distributor or wasted-spark) can afford some redundancy in the low-load/low-speed region, and I've seen a few (mainly road duty) twin-plug engines with failed plugs or faulty plug leads that have gone completely undetected, with one plug doing all the work in the cylinder. The shortfall only being discovered when going through ignition optimisation for peak power or, as in Kirk's case, hunting down insufficient part-load fuel burn issues.
Possibly even more relevant is that looking at Graham's pics and judging by those coil packs, it appears that Clewett uses an inductive system to generate spark energy, not capacitive discharge (CDi). Inductive systems tend to run at slightly lower HT voltages, so unless you've got an enormous spark plug electrode gap trying to be bridged, there's less energy being carried, so less propensity to try and 'take an alternative route', therefore less sensitivity to HT sheathing thickness.
Hope this helps put some detail behind the difference in the systems and the ways in which they get the spark to the plug, and I should emphasise that we're musing over potential failure modes here, not the system 'normal' healthy state. In most cases, leads are doing their job, and their insulation is working as intended, so regardless of which hardware is in play, spark goes nowhere but to the intended cylinders, and the potential failure modes described above are rare occurrences.
A basic layman's test is to look at your engine running in the dark - can be quite illuminating! The area around number 1 cylinder can be quite prone to stray sparks.
Sorry if this reads 'off-topic' but I had exhaustive emails with Clewett during my issues with the system they sold me a year ago.
During all the words Clewett demanded that the location of the parts and the lead routes and separation were focused on and this led me to re-locate all manner of components from my original locations that got the heavy parts mid ships on this car.
He expressed that such miss-locations were responsible for failure of the control unit which was the root of the problems...
But all is well now. These systems are not the easiest to fault find when you really do not like electrics!
Responses like Mike's above sure help.
Have to say now sorted my 3.2 is a belter!
73T 911 Coupe, road/hillclimber 3.2L
Lola t 492 / 3.2 hillclimb racer
Boxster 987 Gen II 2.9
Feels like a long time since an update. Factually it is a long time.Look away now if you are hoping for a trail of problems with the ST or personal mishaps you might find amusing. Ownership of the car has become a little boring of late. Some of that is probably due to the fact it has been in storage for around 14 months. Out of harm's way.
I have been busy since last May with a house refurbishment, extensions and hard landscaping. Moved to a rental property for a year which was 'interesting' due to a lunatic neighbour. I have not participated in the actual work on the house project but limited myself to the design and supervision of works. You see I am older than 911hillclimber and he often tells us his age prevents him from doing certain things. The house is finished and hard landscaping will be done soon.
So the last two outings in 2023 were to 'Unstock' and Classics at the Club House. The former was a PCGB ( no boos from the back please) modified register affair held at a Porsche workshop which involved a round trip of 70 miles. The usual trepidation in the journey but in the end the only thing of note was the rain. The weather seem to ensure a poor turn out of around 30 cars; some water-cooled and some air cooled and all modified to a greater or lesser extent.
Whilst not brimming with confidence that the car would behave the next outing was to Classics at the Club House ( air cooled edition) which is a lovely laid back and uncommercial event in the grounds of a golf club. A good range of VWs, Porsche and the occasional odd ball all of course air cooled. Nice sunny day and a meet up with a few mates. Simple but excellent day out. The above involved a round trip of about 80 miles and I started to relax a little as the car performed perfectly. Two trips and no first world trauma to experience. Was I bonding with the devil at last? Not on your nelly.
The car was then put in store happy in the knowledge that all was well with the ST.
A month later I got a phone call. There is " a small pool of oil under your car". Bugger. Lulled into a false sense of security. Months later Autofarm got around to looking at the problem. A failed gasket somewhere and can't remember where. I can remember the bill at the end though.
Just before the DDK event of the millennium the car was pulled out of store, given a light wash and a few quids worth of fuel and brought home. It can now be stored in the garage as the building materials have bern evicted from half of the tandem space. The rear half still contains period furniture from our last house which we left in September 2021. Anyone want an Oak Geogian corner cupboard (free) or a chest of drawers also in Oak? Of course we have, in faintly modern parlance "downsized" except we have, with the building work, "up sized" a little which included the extension of the garage. Once I can clear the back half of the garage the 1970 S can come home too. I am looking forward to being able to go for a drive whenever the mood takes. Except at the moment the ST is forcibly restrained by a skip in front of the garage doors.
The neighbours have commented that the ST is back. Not that they have seen it but more like heared it on start up.
The journey to the DDK event at C&M was along mostly minor roads and I started to enjoy actually driving the car rather than listening for the untoward noise or contemplating a potential problem. Another trouble free journey. Was I dreaming or have I imbibed an illegal substance? Nope. All is well. But as I am something of a cynic I am expecting something to go wrong. Once the skip gets shifted we will find out.
The DDK event was really very good indeed as was Megaphonics. Thank you to Spit for organising. Unfortunately, I missed Clive's speech, as I did not stay at the 'hotel', which I understand may be an entry for the Guiness book of Records as so long ( interminable?) that Bootsy ( aka the handsome hunk) had to cut his speech down to a couple of sentences.
