pedsurg

So is the question "Is it easier to modify the suspension of the vette or the engine of the cayman" ?

Jack

carreracup21

I don't think any of us have driven the new Z06, so the suspension might be fine. For that matter the engine on the Cayman might be sufficient as well, but no dry sump or LSD is a non starter on the track. They might have worked a little harder to cut some weight, then the engine would be less of a factor.

BiggerTwin

Am I missing something here? The Cayman S brochure on pages 26 and 84 says the motor has integrated dry-sump lubrication.

Alan

carreracup21

"integrated dry-sump" sounds like an apology for not having a real dry sump which is a seperate oil tank outside the engine.

mooble117

LSD is a halucanagenic drug.
It causes to the car to spin wildly out of control.
It's not recomended while driving

j/k i always find that funny how they have the same acronym

Gator_86_951

Integrated dry sump isn't a true dry sump.

I have a lot of track miles on my 951. No dry sump. For spring racing it is fine. But long term it is not desirable. I run out of car in about 30 minutes. The intake termps rise and you always run the risk of oil cavitation. But, I haven't heard of too many 996 motors blowing up from that.

The biggest issue is the lack of an LSD. But, like I have echoed in other threads, somebody will put the GT3 motor in this car with the gearbox which will be wicked as ****. Porsche won't make what we want. You'll just have to do it yourself. Bring your wallet.

The only place I have ever had a problem with lack of LSD is the hairpin @ sebring. But then again my 951 only has maybe if I am lucky, like 230 or 240 bhp. So, other then that.... I am sure there are sections where more linear application of paltry horsepower would be benficial.

Wait 5 years. Pick one up for pennies, put in the motor you want, strip the interior, have fun.

willr

Lack of true dry sump should be of no concern on the road.

Only GT and turbo Porsches have true dry sump nowadays, but like missing LSD it doesn't stop the vast majority of drivers getting what they need out of the cars. Plenty of non-dry-sump Porsches take to the track and are fine - stick with standard tyres (as advised in the manual) and take a break occasionally (most people wouldn't consider staying out more than 20-30 minutes at a time, anyway).

mooty

i ran a 2004 996c2 (obviously not true dry sump) with toyo RA1 R componds on track often 50 min. at a time. and several times i basically drove from a full tank to no fuel, 90 min or maybe longer, it never had oiling or starvation prob.

the tranny does overheat a bit.

Premier Motorsp

Many subjects in this thread.

GrantG, why are LSD and PSM mutually exclusive? I don't see why the PSM would have a problem with LSD.

I suspect it is only because PSM is cheap to manufacture and LSDs are not.


Chris Cervelli
Premier Motorsports

GrantG

Hi Chris - Good to hear from you -we need to get together soon The PSM relies on its ability to apply the brake to each of the four wheels independently to make understeer/oversteer compensation under a variety of situations. As you know, with a clutch-type LSD, the rears are locked together under deceleration and any brake application to one rear wheel will also slow the other rear wheel. This will confound the software that controls the PSM. A torque biasing diff may be the only alternative (not optimum for the track) and I'm not sure that adding the TBD wouldn't also confuse the PSM software?

Premier Motorsp

The way I understand it, PSM should brake the outside rear tire when understeer is occurring.

The diff shouldn't matter. The tires are going to run the same speed (neglecting the effects of the different corner radii for each tire) due to their interaction with the pavement. I am sure that PSM will not brake the outside tire to the point where it begins to slide (slip ratio >8% or so) and therefore be turning significantly slower than the inside tire since it would then lose its cornering force and cause sudden oversteer.

The diff isn't locked 100% at any time. The degree of lockup depends mainly on the input torque. The input torque on decel is pretty low (just the drag of the freewheeling engine, although that could be increased a great deal by using the e-throttle in conjunction with a fuel cut) so the degree of lock up is pretty small under decel. For sure it is enough to influence the corner entry feel, but not enough to disallow different brake pressures at each wheel.

You are probably somewhat correct though. A tight LSD would interfere with PSM. I don't think the LSD would make it nor function at all though.

There is probably much more to this. We should get Vaughn's input since he engineers PSM systems.

Chris Cervelli
Premier Motorsports

mooty

chris C,

PM sent

GrantG

Yes, the degree of locking is what determines whether PSM will be incompatible. Porsche provides PSM with a mild 25% locking LSD in the 2004 Anniversary 996 and 997S with -20mm sport suspension (RoW only). But, it has never been made to work with a more aggressive locking ratio (Carrera GT, GT2, GT3 all go without PSM and their locking ratios are closer to 60%. CGT has traction control but no PSM).

pedsurg

It will be interesting to see what combo the new gt3 will have.
Jack

pedsurg

Just received this clip. Not totally off topic since it relates to both "Top Gear" and LSDs and does mention a certain Porsche.
http://www.villacorte.org/miata/mult...-greyhound.mp4

Jack