GT4 Engines and GPF

[ralphmusic]

An interesting post on a German Forum:

9A1 Motor ist ja Serie tot, allein schon, weil er keine verstellbaren Auslassnockenwellen hat, das braucht man im Prinzip für Euro 6d und deutlich höhere Einspritzdrücke mit idealerweise wie beim ab 991.2 S vertikalen Zündkerze angeordnetem Einspritzventil.
Grundmotor aber 9A1 Motor.

Die OPF Geschichte dann riesen Akt, beim 992 wird der differenzdrucküberwacht, wie bei Dieselmotoren Standard, dann sollte OPF katnah sein, damit Rußpartikel verbrennen, aber zu heiß darf OPF auch nicht werden.

War früher zu hohe Kat Temperatur auf der Rennstrecke ggfs. ein Problem, hat man dazu jetzt noch OPF Temperaturproblem, bei 950 Grad soll der am Ende sein. Im Zweifelsfall regelt DME kräftig runter.

My German is not good but I think it is saying the 9A1 engine as fitted to the 981 GT4, and presumably the same generation used in the 718 GT4 lacks certain technologies required for most efficient combustion namely camshaft adjustment and ability to run sufficiently high fuel injection pressures. It also notes the 991.2 Turbo engines have a different spark plug/injector arrangement. It also suggests latest 911 engines have pre-cat soot sensors (not sure whether this is an engine design point) as do diesel engines which enable better particulate filtering.

On cats, I think it says the 9A1 runs high cat temperatures which cause issues on track (BGB report race Clubsports requiring regular cat replacements) although I can’t really fathom that point.

Perhaps this and Porsche's issues with 4-way cat system and restarting development on a 3-way cat design also goes some way to explaining why Porsche made the late (October Weissach meeting) decision to keep the 3.8L engine in the Clubsport.

If we have any German speaking engine experts on here, it would be interesting to get an informed view on this. If these points are valid, it would seem that Porsche are unlikely to invest in a new generation engine so 718 in cooking and GT form continue as is/soon to be for another 4 years.

 

[Motorhead]

Thanks for that Ralph.

Unfortunately I can't help with the translation nor can I claim any expert knowledge on combustion issues, but I think your interperetaion is about right. While the latest F-4 and F-6 turbo engines have variable timing and lift on both inlet and exhaust camshafts the 9A1 has it only on the inlet camshaft, which presumably has an impact on emissions/particulates, as do higher injection pressures and the latest (diesel technology!) piezo-injectors introduced on the 992 engine.

I always thought that cats were meant to run at very high temperatures but presumably there's a limit to what they will tolerate in terms of continuous high-speed running such as that encountered on a race car? Although fuel economy is a consideration with a race car I doubt that they'll be running a lean mixture, so maybe cats become contaminated at a faster rate than for a road car?

In view of the fact that there haven't been any sightings of 982 replacement mules I reckon it's a given that the 718 will be around for a few years yet, I think confirmed recently by Porsche's chairman Oliver Blume, with anticipated n/a and existing turbo engines, the latter with possibly some type of hybridisation.

Jeff

 

[ralphmusic]

And I wonder whether the current GT3 engines have these features?

 

[Motorhead]

I'm not sure that the 991.2 GT3 engine featured VarioCam Plus on both inlet and exhaust cams Ralph, but since its a bespoke engine I wouldn't think it would be too difficult to incorporate it and maybe some of the other 992 engine features such as the piezo-injectors and revised injector/sparking plug placement, if applicable.

The 991.2 was rushed into production to avoid WLTP but the 992 GT3 will have to meet the new standards, which means including a GPF. Surely the powertrain engineers will have learnt quite a bit from the protracted GT4 engine development process? That's assuming of course that AP is still sticking to his mantra that GT cars will have n/a engines..!

Jeff

 

[ralphmusic]

Having hacked around various German forums it seems as though the 718 GT4 engine will incorporate some of the 992 engine technologies, at least the variable exhaust camshaft and higher pressure and central fuel injectors.

It will also have the 'new' RSW coating which is a grey cast iron layer applied by a plasma spray process. This layer has the propensity to rust on vehicles that are used for short distances (never reaching full operating temperature), similar to the 981 lining which could form aluminium oxide on the cylinder liner.

Easy to worry so bottom line, drive them regularly and not for short trips (what's new?)

 

[Motorhead]

All much as you'd expect Ralph, given the experience gained by Porsche in engine development over the past few years.

Jeff

 

[Peter_Bull]

Below is the Google translation of German to English if it helps.

9A1 engine is dead series, alone, because he has no adjustable exhaust camshafts, which one needs in principle for Euro 6d and significantly higher injection pressures with ideally as in the case of 991.2 S vertical spark plug arranged injection valve. Basic engine but 9A1 engine. The OPF story then huge act, the 992 is the differential pressure monitored, as standard diesel engines, then OPF should be katnah, so burn soot particles, but too hot OPF may not be. Was in the past too high Kat temperature on the racetrack if necessary. A problem, one has now still OPF temperature problem, at 950 degrees should be the end. In case of doubt DME regulates down strong.

 

[Motorhead]

Yes, I think that both Ralph and myself have already been there Peter.

Not a great help and looks more like the sort of translation you find on ebay from a Far Eastern seller..!

Jeff