Brake upgrade for non-S

[MNBoxster]

Originally Posted by pecivil

of course hp has nothing to do with how a car stops....

but it has a LOT to do with how fast the car is going when it tries to stop, 'eh?

so as a cars TOP speed increases, the braking capacity needs to increase to be able to stop in a reasonable distance, correct?

so if my boxster, or twin turbo 911, or whatever stops from 60mph, yes the same brakes will work just dandy

However if my boxster is stopping from 150mph, BUT my 911 twin turbo is stopping from 185mph, then we need better brakes on the turbo, if it is to slow down in the same distance as the boxster. The key is stopping in the same (or lesser) distance.

Stopping DISTANCE is the key here, Jim. I could easily stop my twin turbo with my stock boxster brakes, cept it may take a bit longer to do it.

so, what we end up with is:

a higher hp car needs bigger brakes

exactly what I said in the beginning, and exactly what car makers tend to do with their sports cars.

Hi,

Again, HP has nothing to do (relatively speaking) with the top speed of a car, it has to do with how fast you attain that top speed. Most cars are aerodynamically limited, not power limited, to how fast they can go. You're never gonna hit 150 MPH in a Boxster unless the Top is Up anyway.

Your arguement about the Boxster at 150 MPH vs the TT at 185 MPH is illogical, you're comparing apples to oranges.

For a street driven Boxster, how often (if ever) do you go 150MPH or even 100MPH? And, assuming there are times which you do, how often are you gonna need to panic Brake at that speed? And who says that the Brake upgrade will be sufficient?

The differences in Stopping Distance are really negligible, less than 10% between the two Brake setups. Given the cost and such, I just don't believe it's worth it. I think most doing the upgrade are going for the Bling of it all and justifying it with arguements like yours.

The value to the Brake upgrade is on the Track where the smaller Brakes will fade more readily. On the Street, where you don't have a constant application of the Brakes without a cooling period in-between, they don't offer that much advantage...

Happy Motoring!... Jim'99

[Paul]

Hey, I agree with Jim on this one, except the part about horsepower and top speed a 2001 Boxster and 2001 996 have the same front end (therefore the same drag) , guess which one goes faster?

[MNBoxster]

Originally Posted by Paul

Hey, I agree with Jim on this one, except the part about horsepower and top speed a 2001 Boxster and 2001 996 have the same front end (therefore the same drag) , guess which one goes faster?

Hi,

I know what you're saying, but Frontal Area is just one component of Drag. The 911 (especially the coupe) is cleaner in overall drag than the Boxster. Yes, I agree, HP allows the 911 to exceed the Boxster purely because of the power which is available to overcome the drag which is the square of the car's speed. But, it's also more efficient. Put the same 3.4L into the Boxster and you won't match the 911's Top Speed, you'd need even more HP to do that, 100 HP more by my calculations...

Happy Motoring!... Jim'99

[Paul]

BTW my major at Penn State was Aerospace engineering, want to talk about Reynolds number, stagnation pressure, force equations for deformable bodies???

0.29 - Porsche Boxster, 2005
0.29 - Chevrolet Corvette, 2005
0.29 - Mazda RX-7 FC3S Aero Package, 1986-91
0.29 - Lancia Dedra, 1990-1998
0.29 - Honda Accord Hybrid, 2005
0.29 - Lotus Elite, 1958
0.29 - Mercedes-Benz W203 C-Class Coupe, 2001 - 2007
0.28 - Toyota Camry and sister model Lexus ES, 2005
0.28 - Porsche 997, 2004


.29 for a boxster, .28 for a 997?????

[MNBoxster]

Originally Posted by Paul

BTW my major at Penn State was Aerospace engineering, want to talk about Reynolds number, stagnation pressure, force equations for deformable bodies???

0.29 - Porsche Boxster, 2005
0.29 - Chevrolet Corvette, 2005
0.29 - Mazda RX-7 FC3S Aero Package, 1986-91
0.29 - Lancia Dedra, 1990-1998
0.29 - Honda Accord Hybrid, 2005
0.29 - Lotus Elite, 1958
0.29 - Mercedes-Benz W203 C-Class Coupe, 2001 - 2007
0.28 - Toyota Camry and sister model Lexus ES, 2005
0.28 - Porsche 997, 2004


.29 for a boxster, .28 for a 997?????

Hi,

Well, if we're comparing resume's, I have a BS in Aeronautical Engineering and a BS in Materials Science from the University of Minnesota and an MS in Aeronautical Engineering from M.I.T (courtesy of the US Navy), Certified Test Pilot - (USNTPS) US Navy Flight Test Center - Naval Air Station, Patuxent River.

Now that that's out of the way, you make my point for me - the Boxster is clean, the 996 is cleaner...

Happy Motoring!... Jim'99

[Paul]

Congrats!

I was going to make the Air Force a career (ROTC) but in 1969 my draft number was 324 and a lot of my classmates were just back from Vietnam (GI Bill) and told me I was crazy.

I did go on to get a private license and an instrument rating and bought a Piper, but I envy your flight experience, since I've always wanted to push the throttles on a fighter!!! I have shot approaches several times at Patuxent.... My brother is stationed at Mountain Home (a lifer).

But I still doubt that the Boxster would need to have 100 more hp than a 996 to have the same drag limited top speed.

[MNBoxster]

Originally Posted by Paul

Congrats!

I was going to make the Air Force a career (ROTC) but in 1969 my draft number was 324 and a lot of my classmates were just back from Vietnam (GI Bill) and told me I was crazy.

I did go on to get a private license and an instrument rating and bought a Piper, but I envy your flight experience, since I've always wanted to push the throttles on a fighter!!! I have shot approaches several times at Patuxent.... My brother is stationed at Mountain Home (a lifer).

But I still doubt that the Boxster would need to have 100 more hp than a 996 to have the same drag limited top speed.

Hi,

I hear ya, my Draft Number came up #12! So I ran to the NROTC Office, raised my right hand, and signed up (I had been in JrROTC in HS) as a Naval Flight Officer. This allowed me to complete school before reporting, but my intention had always been NAVY AIR.

Then, I passed the Flight Exams (got my Private License at 17) and was off to NAS Pensacola for Basic Flight Training (T-34C Turbomentor). Then to NAS Beeville,TX for Advanced Jet Training (AF-9F). Luckily, I graduated high enough to get a coveted 'fleet seat' and was off to NAS Miramar.

RAG (Replacement Air Group) VF-121 for training and certification in the F-4 PhantomII, this included Air-to-Air (NAS Miramar), Gunnery (NAWS China Lake), then back to Miramar for Seaquals.

Finally, I was assigned to VF-142, the "Ghostriders", on the USS Midway and did 8 WestPacs, mostly MigCap, ResCap, but also some IronHand. Two tours on Yankee Station (Gulf of Tonkin) and one on Dixie Station (Mekong River Delta - South China Sea). Got my 3,000 Flight Hours and shot at a few times.

Then Graduate School and off to Pax River for Test Pilot School and 3 years in the Navy Flight Test Center flying nearly everything in the inventory - F-8, A-4, F-4, F-14, F/A-18, F-16 (yes, this was originally spec'd for the Navy and still carries it's Tailhook today). It was fun - I got to fly REALLY fast airplanes and spend copius amounts of the Taxpayer's Money - for Pay!...

Happy Motoring!... Jim'99

[insite]

Originally Posted by Paul

But I still doubt that the Boxster would need to have 100 more hp than a 996 to have the same drag limited top speed.

jim - i think you're off by a decimal point. i get 10HP more to go the same top speed.

Hey Doc,

I'm no scientist but this is what i was told. The Boxster brakes on the base are amazing. No need to buy S brakes.

If you ask me, they only put those brakes on the S to make it different from the base model. Meaning that they needed to justify an S model, so they gave you red S brakes, a new bumper, 6speed and so on. So pretty much it's a waste of money to put the S brakes on a base.

If you plan to drive the car at 150mph and come to a complete stop everytime that you drive, then yes get the S brakes.

I'm under the impression that the big brakes just make the car stop faster / better / closer ?

n for that matter, the base brakes are pretty big. I painted mine yellow, and they are pretty big.

[Tool Pants]

Originally Posted by Paul

Hey, I agree with Jim on this one, except the part about horsepower and top speed a 2001 Boxster and 2001 996 have the same front end (therefore the same drag) , guess which one goes faster?

Boy, this is an oldie that came back to life.

I think the one that Porsche wants to go faster is the one that Porsche charges more money for.

[insite]

Originally Posted by MNBoxster

Again, HP has nothing to do (relatively speaking) with the top speed of a car, it has to do with how fast you attain that top speed. Most cars are aerodynamically limited, not power limited, to how fast they can go. You're never gonna hit 150 MPH in a Boxster unless the Top is Up anyway.

cars are drag-limited at a given power output. terminal velocity is reached when the power required to overcome drag for a given vehicle equals the maximum power output of the motor. for a vehicle of a given frontal area and cd, increasing the power output will increase the top speed capability.

Originally Posted by MNBoxster

The value to the Brake upgrade is on the Track where the smaller Brakes will fade more readily. On the Street, where you don't have a constant application of the Brakes without a cooling period in-between, they don't offer that much advantage...

agreed. pecivil's point, however, is still valid for track scenarios. a higher HP car will see higher average speeds around a track (given equal chassis). accordingly, the kinetic energy the brakes will have to shed increases. this will increase heat. as a brake system essentially changes kinetic energy to thermal energy, the job of a brake rotor is to get rid of that heat, hence the larger system. on the road, this makes almost no difference. on the track, it makes a LOT of difference.

[MNBoxster]

Originally Posted by insite

cars are drag-limited at a given power output. terminal velocity is reached when the power required to overcome drag for a given vehicle equals the maximum power output of the motor. for a vehicle of a given frontal area and cd, increasing the power output will increase the top speed capability.







agreed. pecivil's point, however, is still valid for track scenarios. a higher HP car will see higher average speeds around a track (given equal chassis). accordingly, the kinetic energy the brakes will have to shed increases. this will increase heat. as a brake system essentially changes kinetic energy to thermal energy, the job of a brake rotor is to get rid of that heat, hence the larger system. on the road, this makes almost no difference. on the track, it makes a LOT of difference.

Hi,

No disagreement here...

Happy Motoring!... Jim'99