Timeo

Can someone enlighten me on the what the major differences are between 996 and 2007-2008 997? Obviously the 997 has a revised interior and no fried eggs but what about the engine, basically the same as 996?

Thx

T10Chris

Different intake tract from the airbox through the intake manifolds... VNT turbochargers... many little things that may or may not make any difference.

Road King

both have the funky coolant lines, but only the 997.1 has issues with the cams...

Timeo

Yes, I was aware of the cam issue. Was that fixed in 997.2? Is 997.2 still a Mezger engine?

T10Chris

997.2 is not a Mezger, it is a 9A1

Carlo_Carrera

The one interesting thing with the 997.1 TT is that its electronically controlled suspension can be modified from reactive to proactive via a software upgrade and the fitting of an aftermarket control module. Proactive suspension is the bomb.

Macster

The 997 turbos are water-cooled. The 996 Turbo turbos are just oil (and "air" -- exhaust gas "air") cooled. Thus the guideline in the 996 Turbo owner manual to let the engine idle 2 minutes before shutting off the engine to give the turbos time to cool down. T10Chris mentioned the VNT aspect. Very cool technology. My 2002 VW Golf TDi had this feature and the level of boost control was amazing.

And the 997 has the better AWD system. No more viscous coupling. The transfer case (?) is a multi-plate wet clutch. The amount of engagement is controlled by the DME.

Under a hard launch the 997 AWD system can actually transfer considerable torque to the front tires.

I have no idea what if any restrictions there are on the 997 Turbo front and rear wheel/tire diameter ratios.

docboy

Be careful with the cam issue. Not to say all 997.1tt's have the cam issue, but if it rears its ugly head, it's a VERY costly fix.

Timeo

I thought the cam issue was $3-$4k fix?

docboy

https://rennlist.com/forums/997-turbo-forum/847001-spun-camshaft.html

/\ That's the thread that kind of spooked me out. OP had $7k fix via Fidelity warranty....

Road King

I believe the 997 AWD cars are free of the tire height restrictions we face and can run a taller back tire. I'm sure there are some recommended sizes, but since all the 997s seem to run 19s they have a lot more choices.

Carlo_Carrera

The 997 can use a wider range of tire sizes but there is limit, mostly due to the PSM programming.

996tnz

Engine's basically the same (variable vane turbos aside), though some of Porsche's historic incremental improvement shows in some parts like oil pickups I think (Kevin of UMW listed these once). Same incrementalism applied to various bushes, mounts, suspension elements, cooling ducts etc.

The same systems can now be fitted to a 996T too (and back to the 993/964 http://www.dscsport.com/porsche/#996) but you need to buy the shocks to go with it. The factory 997.1 (damptronics?) don't have anywhere near the same reaction speeds as the dedicated shocks that come with the system so even on a 997.1 those dedicated ones may be tempting.

That 2 minute cool down is what I'd most like to change on the 996T. I have a manual roller door on my garage as it gives me a good excuse to leave my loud exhaust rattling the windows for a minute or so of cool down when she comes home hot. At track she gets well over two minutes.

The 996T transfers considerable torque forwards too, but with what looks to be about 0.2s (car hot) to 0.5s (car cold) delay. So the 997.1 AWD system helps launch them a bit faster.

I read somewhere that the improved efficiency of the 997.1 AWD system is also it's downside, as it is said to be more intrusive (less progressive and predictable on the limit) during very spirited driving on road or track. For the 997.2 generation, Porsche reportedly retuned the electronic contol unit to operate the electronic AWD clutches in such a way as to more closely replicate the behavior of the 996T's viscous unit. Take from that what you will.

As for other differences, I think steering became variable ratio on moving to 997.1 and some feel was lost (as seems to happen pretty much every generation). Thankfully (Porsche already lost it on the Cayenne back in 2003) the 997 still has a proper handbrake though.

Rrussval

Does that mean that the 9a1 engine never had the infamous spun camshaft problem?

Carlo_Carrera

9A1 engine does not have the spun camshaft problem.

As far as I can tell the only issue with 9A1 engines, and I stress it is a very rare issue, is with cylinder scoring if the engine is repeatedly driven very hard without properly being warmed up.