Rennteam 2.0 - EN - Forum - Re: GT3 115 bhp/L - Page1

Sep 21, 2006 11:04:11 AM

Alex_997TT: Rennteam Master; Loc: Reading , United Kingdom; Posts: 3320, Gallery; Registered on: Nov 20, 2005

GT3 115 bhp/L

Stupid question I'm sure, but can anyone please explain to a layman like me why a GT3 with a 3.6L engine can produce 415bhp (115bhp/L) and a Carrera S with a 3.8L engine can only push out 355bhp (92bhp/L). Even with the Porsche Powerkit the Carrera S only goes up to 99bhp/L.

So what 'magic' has Porsche used to achieve this in the GT3?

By the same measure a 3.8L GT3 should push out 440bhp given the same 115bhp/L. Makes me feel very short changed on my 355bhp 3.8L Carrera S!

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Sep 21, 2006 11:15:08 AM

Alex_997TT: Rennteam Master; Loc: Reading , United Kingdom; Posts: 3320, Gallery; Registered on: Nov 20, 2005; Reply to: Alex_997TT

Re: GT3 115 bhp/L

BTW - my Audi S3 (1.8L 250bhp) pushes out 140bhp/L so I'm sure the Turbo has a lot of tuning headroom too!

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Sep 21, 2006 11:48:40 AM

MrBonus: Junior; Loc: Delaware; Posts: 97, Gallery; Registered on: Oct 4, 2004; Reply to: Alex_997TT

Re: GT3 115 bhp/L

More aggressive cam profiles, better flowing heads, etc.

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Sep 21, 2006 12:26:05 PM

bstew: Expert; Loc: NC, USA; Posts: 1797, Gallery; Registered on: Oct 11, 2005; Reply to: MrBonus

Re: GT3 115 bhp/L

I think what this shows is that Porsche is designing to a market. If Porsche wanted more hp out of the CS then I'm sure they could do it. Really what we all want it for every model to have more hp then anything and everything else out there. As we all know this is not Porsche's thing....

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Sep 21, 2006 1:18:16 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: Alex_997TT

Re: GT3 115 bhp/L

Quote:
Alex (UK) said:
So what 'magic' has Porsche used to achieve this in the GT3?

The way to do that (other than forced induction) is with revs. GT3 revs to 8,400 and has the necessary hardware (like Titanium conrods) to do it. Carrera/S only revs to 7,200...

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Sep 21, 2006 1:26:41 PM

W8MM: Rennteam Master; Loc: Cincinnati, OH , United States; Posts: 3993, Gallery; Registered on: Aug 8, 2003; Reply to: bstew

Re: GT3 115 bhp/L

Quote:
bstew said:
I think what this shows is that Porsche is designing to a market.

Of course they are!

Getting more peak HP out of a given normally aspirated motor ordinarily means giving up some low-end torque.

If the low-end torque goes away, one will have to "row the gear box" harder to take full advantage of any increased power. It changes he personality of the car, making it more peaky and less "luxurious" to drive.

Unless one likes to shift as a hobby, the extra peak power doesn't always translate into increased performance. One has to integrate the area under the torque curve between the shift points in RPM to see how much velocity will be gained in a given gear.

It's easily possible for an engine with a broad torque curve (and lower peak power) to out accelerate another with a peaky torque characteristic if the shift points or the transmission gearing are not perfectly suited to the situation.

All these BHP/liter comparisons are great entertainment for bench racers, but the real world is so much more complicated.

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Sep 21, 2006 1:29:40 PM

Alex_997TT: Rennteam Master; Loc: Reading , United Kingdom; Posts: 3320, Gallery; Registered on: Nov 20, 2005; Reply to: Grant

Re: GT3 115 bhp/L

Quote:
Grant said:
The way to do that (other than forced induction) is with revs. GT3 revs to 8,400 and has the necessary hardware (like Titanium conrods) to do it. Carrera only revs to 7,200...

So does that mean the 997 GT3 revs much higher than the old 996 GT3 given that produced 381bhp?

I guess it's a big combination of things if not...

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Sep 21, 2006 1:33:28 PM

Scotty A: Senior; Loc: New Jersey; Posts: 606, Gallery; Registered on: May 31, 2006; Reply to: Alex_997TT

Re: GT3 115 bhp/L

Actually, your table clearly shows that Porsche is offering lots of choices to the market on how much power, and in what configuration, you want.

You want more power, you pay more money.

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Sep 21, 2006 2:56:31 PM

Alex_997TT: Rennteam Master; Loc: Reading , United Kingdom; Posts: 3320, Gallery; Registered on: Nov 20, 2005; Reply to: Scotty A

Re: GT3 115 bhp/L

I realize bhp/L is not the best measure of how tuned a car is (especially for non-normally-aspirated cars) but just for my own curiosity I looked up some others for comparison:

I have greyed out the Turbo cars as they don't really count...

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Sep 21, 2006 2:56:59 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: Alex_997TT

Re: GT3 115 bhp/L

Quote:
Alex (UK) said:
Quote:
Grant said:
The way to do that (other than forced induction) is with revs. GT3 revs to 8,400 and has the necessary hardware (like Titanium conrods) to do it. Carrera only revs to 7,200...

So does that mean the 997 GT3 revs much higher than the old 996 GT3 given that produced 381bhp?

I guess it's a big combination of things if not...

Yes, the original GT3 (99-01) revved to 7,600 or 7,800 (don't remember) for 360hp and the MkII revved to 8,200 for 380hp and the 997 revs to 8,400 for 415hp. Certainly, there are other improvements, but since they kept the displacement the same, the revs are the biggest improvement (along with more compression and better breathing).

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Sep 21, 2006 3:08:58 PM

Alex_997TT: Rennteam Master; Loc: Reading , United Kingdom; Posts: 3320, Gallery; Registered on: Nov 20, 2005; Reply to: Grant

Re: GT3 115 bhp/L

Interesting thanks Grant

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Sep 21, 2006 3:18:14 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: Alex_997TT

Re: GT3 115 bhp/L

Quote:
Alex (UK) said:
Interesting thanks Grant

No problem. Also, it should be noted that getting more power out of a motor like a GT3 is not as simple as raising the electronic rev limit.

Revs create alot of stress in a motor. I believe that the forces created are related to the moving mass times the square of the speed of its parts (a motor that revs twice as high will have 4 times the stress, assuming everything else is equal). So, the engineers need to make large strides in reducing the mass of the moving parts to accommodate the higher piston speeds without causing additional stress (and shorter engine life).

So, if you want to raise engine speed 40%, you need to cut the moving mass in half to keep the same forces on the bearings, rods, etc...(square root of 2 is about 1.4)

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Sep 21, 2006 3:27:21 PM

Jeannot: Expert; Loc: Currently in Hong-Kong , Switzerland; Posts: 1745, Gallery; Registered on: Feb 13, 2005; Reply to: Grant

Re: GT3 115 bhp/L

F1: 3.0L . 800hp+ :-)

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Sep 21, 2006 3:35:24 PM

Scotty A: Senior; Loc: New Jersey; Posts: 606, Gallery; Registered on: May 31, 2006; Reply to: Grant

Re: GT3 115 bhp/L

Quote:
Grant said:
Quote:
Alex (UK) said:
Interesting thanks Grant

No problem. Also, it should be noted that getting more power out of a motor like a GT3 is not as simple as raising the electronic rev limit.

Revs create alot of stress in a motor. I believe that the forces created are related to the moving mass times the square of the speed of its parts (a motor that revs twice as high will have 4 times the stress, assuming everything else is equal). So, the engineers need to make large strides in reducing the mass of the moving parts to accommodate the higher piston speeds without causing additional stress (and shorter engine life).

So, if you want to raise engine speed 40%, you need to cut the moving mass in half to keep the same forces on the bearings, rods, etc...(square root of 2 is about 1.4)

... and then, since you'll have to reinforce the bearings, rods, etc. anyway because you can't actually get there, you once again INCREASE the mass - creating more stress.

Engineering is actually hard

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Sep 21, 2006 3:35:28 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: Jeannot

Re: GT3 115 bhp/L

Quote:
Jeannot said:
F1: 3.0L . 800hp+ :-)

Yes, and about 20,000rpm

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Sep 21, 2006 3:37:24 PM

Hurst: Veteran; Loc: Potomac, MD; Posts: 1255, Gallery; Registered on: Apr 15, 2005; Reply to: Alex_997TT

Re: GT3 115 bhp/L

The 997 GT3 invested most of its "upgrades" over the 996 in terms of lowering moveable mass to allow for the engine to rev much higher...

Most of the cars on that list need to be driven hard to extract that juice (as W8MM said). If you take two comperably powerful cars, one with low displacement and the other with more displacement, the higher bhp/l car will beat the other on a track, but for daily driving, you better be ready to either downshift a lot or keep the revs real high (GT3, Lotus, S2000)...

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Sep 21, 2006 3:38:00 PM

jackg: Newbie; Loc:; Posts: 33, Gallery; Registered on: Jan 28, 2004; Reply to: Jeannot

Re: GT3 115 bhp/L

It's worth noting that the Carrera/S have a totally different engine to thye GT3. More interesting though, Suzuki GSXR1000 has 185bhp from 1ltr without a hair dryer. Even better though, the BMW FI turbo cars had 1500 Bhp from 1.5ltrs with the boost wound up for qualifing!!! They were however hand grenades with the pins out!

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Sep 21, 2006 8:28:00 PM

Mithras: Expert; Loc: Toronto, Canada , Canada; Posts: 1981, Gallery; Registered on: Mar 16, 2005; Reply to: jackg

Re: GT3 115 bhp/L

My dad's 3.0ltr RSR clone makes 385 hp (128 hp/ltr) at 8350 rpm and redline is set at 9100 rpm. It also has Ti con rods, Ti valves, very trick heads, a hot hot cam, high stacks, electronic fuel injection with individual injectors and the case is polished almost to a mirror finish. The engine also only lasts 45-50 hours between refreshes... I guess low stress equals long life, and a production motor can't have too much stress, what with warrantees and all. 415hp out of a 3.6ltr engine and reliability is quite a feat IMHO. Remember a Viper engine at 500 cubic inches is an 8.2 liter engine and still only makes 500hp!

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Sep 21, 2006 8:31:53 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: Mithras

Re: GT3 115 bhp/L

Quote:
Mithras said:
My dad's 3.0ltr RSR clone makes 385 hp (128 hp/ltr) at 8350 rpm and redline is set at 9100 rpm. It also has Ti con rods, Ti valves, very trick heads, a hot hot cam, high stacks, electronic fuel injection with individual injectors and the case is polished almost to a mirror finish. The engine also only lasts 45-50 hours between refreshes...

Please post photos

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Sep 21, 2006 8:45:17 PM

rhino: Rennteam Pro; Loc: Island , Saint Lucia; Posts: 2866, Gallery; Registered on: Jan 26, 2006; Reply to: Mithras

Re: GT3 115 bhp/L

Quote:
Mithras said:
My dad's 3.0ltr RSR clone makes 385 hp (128 hp/ltr) at 8350 rpm and redline is set at 9100 rpm. It also has Ti con rods, Ti valves, very trick heads, a hot hot cam, high stacks, electronic fuel injection with individual injectors and the case is polished almost to a mirror finish. The engine also only lasts 45-50 hours between refreshes... I guess low stress equals long life, and a production motor can't have too much stress, what with warrantees and all. 415hp out of a 3.6ltr engine and reliability is quite a feat IMHO. Remember a Viper engine at 500 cubic inches is an 8.2 liter engine and still only makes 500hp!

Yes please some photos!!!

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Sep 21, 2006 8:46:53 PM

rhino: Rennteam Pro; Loc: Island , Saint Lucia; Posts: 2866, Gallery; Registered on: Jan 26, 2006; Reply to: Grant

Re: GT3 115 bhp/L

Grant, I know you have posted pics from your beauty before but would you mind putting the link to them again?

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Sep 21, 2006 9:13:49 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: rhino

Re: GT3 115 bhp/L

Quote:
rhino said:
Grant, I know you have posted pics from your beauty before but would you mind putting the link to them again?

Well, twist my arm

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Sep 21, 2006 9:14:21 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: Grant

Re: GT3 115 bhp/L

inside

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Sep 21, 2006 9:14:58 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: Grant

Re: GT3 115 bhp/L

engine

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Sep 21, 2006 9:15:30 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: Grant

Re: GT3 115 bhp/L

trunk

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Sep 21, 2006 9:17:16 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: Grant

Re: GT3 115 bhp/L

gearbox through rear window

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Sep 21, 2006 9:22:50 PM

Mithras: Expert; Loc: Toronto, Canada , Canada; Posts: 1981, Gallery; Registered on: Mar 16, 2005; Reply to: Grant

Re: GT3 115 bhp/L

Quote:
Grant said:
Quote:
Mithras said:
My dad's 3.0ltr RSR clone makes 385 hp (128 hp/ltr) at 8350 rpm and redline is set at 9100 rpm. It also has Ti con rods, Ti valves, very trick heads, a hot hot cam, high stacks, electronic fuel injection with individual injectors and the case is polished almost to a mirror finish. The engine also only lasts 45-50 hours between refreshes...

Please post photos

Sorry, no pictures of the engine at my office, but here are a couple of it running. Though it's a little different now, we had the head aerodynamisist from Multi-matic go through the car and it's a bit wider in the front and much more streamlined. Looks like a beast now (and will still hit 172mph going into the bus-stop at the Glen)

/uploads/270998-PorscheSebring.bmp

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Sep 21, 2006 9:24:48 PM

Mithras: Expert; Loc: Toronto, Canada , Canada; Posts: 1981, Gallery; Registered on: Mar 16, 2005; Reply to: Mithras

Re: GT3 115 bhp/L

more

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Sep 21, 2006 9:25:28 PM

Mithras: Expert; Loc: Toronto, Canada , Canada; Posts: 1981, Gallery; Registered on: Mar 16, 2005; Reply to: Mithras

Re: GT3 115 bhp/L

last

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Sep 21, 2006 9:26:15 PM

Grant: Rennteam VIP; Loc: Denver, CO , United States; Posts: 12586, Gallery; Registered on: Aug 21, 2002; Reply to: Mithras

Re: GT3 115 bhp/L

Nice! Please post engine photos too when possible - much appreciated!

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