brooklynkid

hi Rennlisters
im looking into purchasing a cayenne 04-05. I wanted to know what if any differences between the S and TT engines. They are both 4.5 L and obviously the TT has the turbos but what about the engine itself. My 996TT had the same displacement as a 996 carrera but the engines were very different . the turbo being a split case design and the carerra a single case. The carerra had some IMS and bearing failure issues where as the turbo was much more dependable.
Ill be towing a 20 ft malibu ski boat approx 4,000 lbs with trailer, do you think the S will have enough torque? Or should i just look for a turbo?
Ive seen the common issues with coolant pipes and cardin shaft etc, anything
else i should look out for considering my towing goals?
thx in advance
brooklynkid

Jeroen Pipelers

I think both'll fine do for towing. TT comes standard with a lot of nice options the S doesn't have. Go drive both, i would be more concerned about the A/T then alu coolant pipes and cardan shaft. Coolant pipes most have had by now and cardan will go bad again and again.

mtnrat

Look for air suspension if you get an S, Standard on the turbo. It self levels for towing. I would get the turbo. More features, more power, more fun and a great tow vehicle. I might be a bit biased though.

J'sWorld

I would stay away from the S model. For the money IMO, the turbo is a steal. You will be very limited in mods for the S and they have more incidence of cylinder scoring. Do you want a leather dash/everything or a plastic dash?

wrinkledpants

Agreed. The scoring issue seems to be common enough to be a general concern. Plus, you can guy a turbo for only a few grand more than an S.

Coolant pipes are a 1-time fix. Cardan shaft and control arms are wear items like they are on any other car. I've never had a german based high performance car go much longer than 100K on control arms.

The valve body in the tranny is the only real major "issue." The early 04 and 05's had a VB that tends to give rough shifts after awhile. A rebuilt unit is about 800 total if you do the labor yourself. It, too, is kind of a 1-time deal if you change the tranny fluid more often (like 50K miles).

Other than that - they're pretty solid cars, all things considered.

Dennis C

The Cayenne S has plenty of power to tow a large trailer, and you can find them with nice option packages. However, you'll have to look harder to find a Cayenne S from that generation with full leather interior, air suspension, etc. The turbos had these things as standard. If there was a huge price differential between an S and a turbo, then I would tell you that you should consider an S. However, the prices aren't that far apart. Based on that, you should get a turbo.

Dilberto

I'm now in the same boat. Should I trade my '05 S with 70k/mi(coolant tubes/Cardan, etc) for a '04 TT with 130k/mi(coolant pipes + non-airbag front collision)?

DWPC

The power loss from elevation is about 3% per 1000 ft for any naturally aspirated engine. If you live in Albuquerque, an S will nominally be down over 15% from its sea level ratings while for the turbo, the loss is nil. So the net difference in performance at 5000 ft is huge. I'm always surprised how this seems overlooked by those in the mountain states. Even at sea level, the price differential vs. performance makes a 955 turbo vs any other 955 a dead nuts bargain.

wrinkledpants

Turbos still lose power, just not as much. The ECU will cut boost above 7K ft, IIRC, to prevent an overspeed of the turbos. That's on top of slower spool times and less overall power at any elevation. All turbo cars work on gauge pressure, not absolute pressure.

To get an idea - just look at the correction factors at a dyno day. Turbo cars still use have them, but they just aren't as big as the NA cars.

69gaugeman

Air suspension is a MUST for me. I tow a 7000lb boat. Did just fine with a V8 treg and finer with the turbo.

Dennis C

Air suspension is really nice in the Cayenne. I had that option on my Cayenne S. I'm guessing that less than 25% of the S models are equipped with this option.

endless_corners

When I was hunting for a CS a few years ago.. Only 2-3% had PASM. Given the market now.. There is little reason to choose an S over a turbo.

DWPC

Got numbers? I'd like to see dyno figures at sea level and at 7000 ft for a TT vs an S. Though the air gets thinner, once the turbo spins up, the wastegate is still dumping excess air so there's plenty for the fuel except perhaps at ski resort altitudes.

I live at 4500 ft and very frequently drive above 7500 ft for shopping and business, and don't feel much difference with the CTT performance beyond a bit more lag. 0-60 may be a few tenths off. On grades, there's no significant difference in engine revs or gear used. When I take our truck, a NA V8, the power difference and performance at high elevation is very apparent; higher revs, usually a lower gear.

dasams

Are you excluding 06?
I'll be surprised if there's even 10% with air.
Agreed

wrinkledpants

You're welcome to google it. I used to log performance data with my twin turbo Audi, and elevation always played a roll. It's why CTT's here in Denver run terrible quarter mile times (5300 ft). The car isn't making absolute boost. The car is comparing the pressure in the charge pipe compared to the ambient pressure. So, as you lose ambient pressure, you're effectively reducing the boost pressure. This is why boost gauges always read zero when the car is shutoff at any altitude. It's also why they pull less vac, and depending on the turbo efficiency, why they won't make full boost at really high altitudes. You could spin the turbos fast enough to make sea level type power, but you'll drastically shorted the turbo's life.

My CTT feels slower here in Denver compared to being at sea level. And when I'm driving around 12K ft, it'd definitely much slower.


From Porsche:

"These turbochargers are designed for a maximum speed of 160,000 RPM (continuous operation). So that the maximum RPM is not exceeded, the DME control module reduces boost pressure as needed above an altitude of 2,200 meters."