Yesterday John Speake (
www.jdsporsche.com) performed a custom EZK (ignition brain) tune on my S4 using his newly-released Sharktuner 2 product.
Apologies if this is teaching granny to suck eggs, but I'll briefly outline the theory of what goes on. If I garble any of it I hope John and/or listers will correct me! If you know more than I do about engines (not difficult) just skip the next few paragraphs.
The idea behind varying the timing of ignition on a car engine is that the fuel should be ignited prior to the piston reaching the top of its compression stroke, so that maximum pressure is imparted to the piston on the power stroke just after it reaches the top of compression stroke.
As revs go up, and things move faster, the spark has to be earlier (ignition advanced) to give the fuel more time to burn.
When the engine load goes up, and throttle is opened wider, you need less advance because the fuel burns faster with more air.
Temperature comes into it as well, with lower temperature allowing more advance. The octane rating of the fuel, and the air/fuel ratio, also govern the ideal ignition advance.
So a lot of dynamic factors control how the advance should be varied as these parameters change in normal driving. The EZK ignition brain carries all this information in the form of a 'map', which lets the brain read off the correct advance to apply for a given set of parameters, and signal the coil to send a spark to the plug at the right time.
You can't alter the values in the map so normally there's no scope for changing the advance curve. That's why modern ecu-controlled ignition doesn't need tuning, and as a consequence doesn't actually allow tuning.
Enter the Sharktuner, which does let you make changes to the timing map.
Why would you want to do that you may ask? Must admit that's what I asked John in my naivety! Well the fact is that the standard 928 S4 map is very conservative. It delays the ignition time (retards it) so that there's very little risk of 'knock' occurring. In fact it leaves too much leeway, so that the car can feel sluggish (the whole point of ignition advance is to get maximum power for given revs and load). Moreover if it does detect knock occurring via the knock sensors, it will increase the retard and only allow it to return to the default value unnecessarily slowly. During this knock recovery period power and response is reduced.
The Sharktuner takes out this 'slack' by replacing the standard map with one you can define. But it's a very safe process. As the ignition map is altered, the Sharktuner will monitor any knocks on a per cylinder basis, and the values adjusted accordingly to eliminate the knock and retain an adequate safety margin. It's a bespoke process - there's no 'one size fits all' map because every engine differs in the point at which knocking can be provoked, and in which cylinder this occurs. The Sharktuner lets you tailor the optimum ignition map to your car.
Theory over, time to start creating the new map.
This is the fun part. John squeezed himself into my passenger seat clutching his laptop, and avoiding stepping on various gear sitting in the footwell including the Sharktuner, my EZK detached from the mounting plate and now interfaced with the tuner, interface box, and various plumbing to allow live measurement of the manifold vacuum taken via the fuel damper vac feed. The amount of kit and cabling made it look like my 928 was auditioning for a remake of Back To The Future, understudying the DeLorean role. John would naturally play Doc Brown.
We started test runs using the standard map. Checking for knock events required a number of full-throttle bursts along Canbridgeshire's roads - fortunately John is as familiar with the local plod's favourite hide-outs as he is with Bosch's circuit diagrams. After each run John would take out some of the retard amount of the standard map, and then we would do another run to check that we hadn't moved too close to knock territory. It was fascinating to see all the data from each run recorded on the computer screen - in fact the tuner had picked up that the wide-open position of my throttle position switch was faulty but that's another job for future intake refurb. After a number of such runs and a final double-check, John pronounced himself satisfied with the new map he had tailored to my engine and we returned to his lab.
Now out of the car John programmed a new memory chip with the new map data, then substituted this memory chip for the original chip in the EZK. The original chip and its contents are unchanged, so for whatever reason this can always be replaced in the EZK and the whole thing returned to original condition. We bolted the EZK back into the car reconnected it, and John confirmed that confirmed the EZK would still 'talk' to his 'Spanner' diagnostic tool (I have one of these but had somehow missed the WOT switch fault when I'd last run the tests).
The customized EZK is frankly a revelation. I had a drive back of around 100 miles on very varied roads, so could appreciate any difference. I would sum it up by saying that whereas before my S4 auto felt like a lazy cruiser, it now felt much more like a sports car. Throttle response was much crisper throughout the range. Kick-down feels much snappier - maybe it's my imagination but at high revs the engine now makes more of a snarl. Around town pick up from low speeds in top gear is now noticeably more eager, and the car feels less ponderous. I'm really pleased.
I believe John is planning to offer this as a new service alongside his famous MAF and LH refurbs which are so highly regarded in 928 circles. No idea what it will cost as John asked if he could use my car as a test bed for the idea of customising. Whatever the cost bear in mind that I could see a big difference in my car's performance and I don't even drive it hard, and consider also that you're getting a new EZK map precisely tailored to your car (and tailored by the guru when it comes to 928 electronics), not some off-the-shelf chip. This goes beyond getting components back to factory spec - it has enhanced the performance of my auto S4.
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