Hi Everyone,
Just thought that I would update you on the 911T and the ignition issues I described in my earlier posts.
We removed the MSD 6AL CDI box and matching blaster coil, which we believe caused rusting of the contact breaker points which in turn snapped and caused ....the car to stop running...and me to get to know the recovery truck drivers on first name terms.
The original Porsche CDI was refurbished and fitted to the car along with a new matching stock coil. The car started easily and ran well. Performance was unremarkable, but solid. Predictable but not exciting. Porsche have accepted the the stock CDI box failed to produce a strong and consistent spark at higher revs. The car is a 911T of course and was not designed to be the fastest car in the range. This proved the car was performing as it should as base line for comparison.
We then fitted a new Permatune CDI box ( generation 6 ) , matching coil and new Permatune contactless distributor ( no points...so no rusting ...and no 'bounce' at higher revs ) . New HT leads, spark plug boots and spark plugs also fitted along with an new ignition wiring harness. Alternator checked and new voltage regulator fitted and bench tested OK. All main earth grounds checked and new earth ground straps fitted to negative of the battery, engine and relay panel in engine compartment.
First thing to say, is that all the Permatune parts are really true to the original look and maintain the engine bay to 'original ' look very well. Permatune have realised that the way the kit looks is as important as the way it works.
We quickly realised that the 'Permatune' distributor is actually a 123 Ignition systems distributor, which is fully programable for ignition advance via an app on a tablet or mobile phone. This allows you to adjust the timing curve as required. A super facility, which is really easy to use. It also incorporates an anti-theft device where you can use your mobile phone app to turn the ignition off when parked. ( Permatune did not declare this overtly, branding the distributor as Permatune. We realised it was 123 Ignition kit when we began to work on programming the timing.)
All the new kit was installed according to Permatune's instructions, which I must say were not the best. Short and 'punchy' - yes. Detailed and exhaustive - No.
The spark plug gap was set to 0.065" as per Permatune recommendations, which is pretty much double the normal recommended gap. A timing curve was installed into the distributor similar to that found in a stock Marelli / Bosch distributor. The result was outstanding. Easy starting both cold and hot. A real boost in power and torque and altogether a much improved drive. More responsive and now an exciting drive. BUT.....there is always a BUT....those of you who know Paschen's Law will know that the voltage required to create a spark in a gas is proportional to the spark plug gap and the pressure of the cylinder ( approximately )
So this substantial boost in power, created by the much larger spark plug gap and hence bigger spark and faster burn, required a huge uplift in voltage which created 'crossfire' and 'tracking', which lead to 'kickback' at cranking....and variable performance once the car was running, particularly at lower revs . A really difficult problem to solve and which lead us to check just about the whole electrical ignition system. Looking back, it is pretty clear that the increased voltage caused by the increase in spark plug gap, would find its way to ground using whatever route it could. Mostly that voltage found its was to the plugs...which gave the bigger spark and the faster burn....but in some cases ...some voltage went elsewhere causing issues.
After much testing and head scratching we concluded that by reducing the spark plug gap to 0.040" the 'kickback' stopped, and the car still ran very well. We seem to have 80% of the potential uplift in power and torque with none of the side effects such as 'kickback' at starting....or variable running at lower revs. Finding this balanced setting took lots of time and patience ( and money given the hours of Porsche Tech time) and Permatune could certainly have helped if they had advised us of potential issues and possible routes to solutions. In reality, their goal of aiming for maximum gain caused us lots of grief in testing, adjusting and re-testing. That said, we got there, eventually and we are very pleased with the results.
Conclusions (thus far) :
1. We still need to test the Permatune system over a long spring /summer season covering say 3000 miles, in order to be able to give firm conclusions....please see below conclusions reached thus far...
2. Starting both hot and cold is much easier with Permatune than with MSD or the stock ignition systems.
3. The car is much more fun to drive with the Permatune kit than with stock. Increased power and torque...feels more responsive...builds revs quicker etc.
4. The car runs noticeably cooler, say 185 degrees vs previously 200 degrees.
5. While the Permatune recommended spark plug gap of 0.065" gives maximum power and torque improvements, it brings with it some issues. They may be OK for track or race, but are not good for a road car. 'Kickback' at cranking ....and variable running at lower revs...being the main issues.
6. Permatune, we feel, should provide much more by way of instructions and should make clear that there are various options for the kit. i.e. - maximum improvements in power and torque WILL give side effects, which may be acceptable for track and race, where starting is normally only required once....and the cars will spend most of their time at 4000 revs plus. .. but which are likely to be unacceptable for a road car. A compromise between reliability and increase power and torque is likely to be the best choice for most road cars...and we feel Permatune should make that clear. In our communications with Permatune, Lonnie was always available and ready to offer help and ideas, however, he only ever outlined one route to success....which was 'use our settings...and all will be well'. We did....and it wasn't. When we reduced the spark plug gap to 0.040", the result was great all round.
7. Programmable timing via the 123 Ignition systems distributor is superb. Next step is to test out different timing curves to reach an optimum situation for both power and reliability. We have changed CDI system, coil, spark plug gap, size of idle jets, size of idle air correction jets, air filters on the carburettors...and so it is unlikely the stock timing curve is suitable. I am hoping for yet more power improvement as we find a more suitable timing curve.
8. I have no idea how the changes have affected fuel economy...and am not concerned in the slightest .
Time will tell...but thus far....Permatune has given the car a new lease of life. ....Really looking forward to the new season.
As to reliability over time.....I will report back in the new year.
Anyone who would like more on Permatune etc , please feel free to e-mail me on - robertlpeck54@btinternet.com
Thank you to all who responded to my original post.
Regards
Robert Peck
