Porsche Enthusiasts Club Forum

I also suspect, the turbo technics kit, from memory, was the same kit of parts, and the part they can't get anymore is the Montego MG Turbo PCV valve.

The very best solution is a aircraft inspired exhaust venturi that plumbs into the middle of the exhaust system (if the system is a nice big bore) and then connects to a catch can, with the other side connected to the crankcase breather, as long as your exhaust is not heavily choked at full boost, this system supplies a vacuum to the catch can at all idle and boost situations, as well as venting the blowby gasses into the exhaust rather than through the engine, which in any kit will leave some oil vapour in the intake, and therefore oil residue and contamination to the whole intake and combustion and intake track.

The other alternative would be an atmospheric venting system via a catch can, which is cheap, but dirty and less than ideal.

Negative crankcase pressure is a wonderful thing, and can bring additional power to any engine under any opperating conditions, some of the benefits include..

* Turbocharger oil drain back flow improvement (sometimes worth playing with this and possibly restricting oil flow to tune it)
* Defoaming of engine oil (negative pressure causes forceful extraction of air from the oil)
* Less lower crankcase pumping losses (the denser the gas in the crankcase, the harder it is for pistons to move)
* Improved piston ring spread, especially at lower rpm and better sealing on the intake stroke throughout)
* Improved valve guide and stem seal sealing
* better oil flow throughout the engine
* less likely for even a poor seal or gasket to leak
* Less crankcase windage due to reduced aerodynamic vortex generation

All of which, to be honest, are the holy grail of a fast car, which is why Porsche used this system in Le Mans cars in the 80's

The downside is a single one... Unless your doing the work yourself, its not cheap and your engine needs to have good seals and gaskets to make sure it is efficient.

Ooops.. I just gave away a trick... Oh well, following my health scares, I don't want some of this stuff to be lost, so better in the public domain than being lost.

Steve there's also the MSD programmable ignition in this tutorial:-

http://www.924board.org/viewtopic.php?t=37897&postdays=0&postorder=asc&start=0

No problem Wes, I don't mind exposing the odd secret, although I am actually thinking of putting together a series of books on the subjects of tuning each Porsche model.

Health is getting there now.. A few more months of medication and physio, then I should be 100% again.

Steve, that distributor looks really interesting, I might have to do some more investigations into that one.

1.2 Bar should not be a problem, I know that from experience on the 924 turbo engines, however I would only worry if your piston crown design might have an impact on the detonation tenancies of the combustion chamber. In theory, 1.4 bar should not be out of the question... But for that you might need my electronic control pressure modifier

Dear Steven,

every modification you mentioned sounds good, especially the high compression ratio. Along with a programmable ignition, it provides a perfect torque curve plus a very good fuel efficiency plus insurance against knocking. That was the big difference to series II, that they raised the compression ratio, decreased the turbine and advanced the ignition timing aggressively under partial load in order to make the engine smoother and quicker accelerate. Since they could regard the boost with the ignition control unit, and control the timing accordingly, it was easy to achieve this good characteristic.
The new distributor, what is based on the original case to remain the authentic look, combines the possibility to advance normally while revving up the engine and retard accordingly depending on the boost. You can program the advance at pressures under atmospheric pressure (1 bar), what is typical at partial load/ cruising and retard at pressures above 1 bar up to 2 bar absolute (1,0 bar of boost). For high performance engines we have another special distributor what can regard pressures up to3 bar (2,0 bar boost). We run a 924 GTS in a German race series what provides 343 hp and it unfortunately needed indeed another ignition timing between 1,3, 1,4 and 1,5 bar of boost. Up to 1,3 bar of boost it never was necessary to further retard. For example, these engines can run with 40 – 45 degrees under partial load and only 25 degrees with boost.
If you will adjust it on a dyno, it is fine as you can do it while running the engine with a laptop on your knees (the distributor has a mini USB port). If you want a basic curve what already has been tested by us, we can of course provide you with such. If you wish we can even load it already in the distributor before we ship it. The distributor only needs a coil, nothing else anymore. Additionally, it has a second wire what can be connected to a switch in your dashboard or wherever, with which you can switch to a second curve you programmed in advance. It can be used similar to the original control unit for lower octane fuel, just by activating one switch.
But I guess, if you want to run 1,2 bar of boost, what I see absolutely uncritical, you will have so much power that the fuel distributor will not provide enough fuel anymore. I see the limit at approximately 250 hp. But however, I guess you will watch the AFR and adjust the boost up to the limit of running out of fuel.

If you need any help, just let me know. We are very well equipped with performance parts for the 924 Turbo. We even have developed CAD designed ported heads, flow bench developed and proven, what are 5-axis CNC machined, race pistons, forged lightweight rods, high efficient intercoolers, high performance turbo chargers, GTS manifolds and many, many more special GT and GTS parts.

Freundliche Grüße / best regards

Michael Wittke