limited slip diff
#47
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.
#51
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.
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.
#52
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).
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).
#53
GT3 player par excellence
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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.
the tranny does overheat a bit.
#54
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, 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
#55
Originally Posted by 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, 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
#56
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
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
#58
Originally Posted by Premier Motorsp
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.
#60
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
http://www.villacorte.org/miata/mult...-greyhound.mp4
Jack
Last edited by pedsurg; 01-01-2006 at 12:04 PM. Reason: spelling