McLaren Life banner

1 - 20 of 53 Posts

·
Owner
Joined
·
544 Posts
Discussion Starter #1
A friend of mine runs a GTR and i am always amazed at how well he can keep up with me, despite his car having only 480bhp. When however you compare the torque of both cars, they are very similar (around 440lbs). So why doesn't the 12c have more torque? Is it restricted by the engine size?
 

·
Registered
Joined
·
11,177 Posts
A friend of mine runs a GTR and i am always amazed at how well he can keep up with me, despite his car having only 480bhp. When however you compare the torque of both cars, they are very similar (around 440lbs). So why doesn't the 12c have more torque? Is it restricted by the engine size?
It is probably down to the low pressure turbo;s that are tuned for longevity,as the acceleration is almost second to none,so they probably thought they didn't need more,i bet if you floored it in auto track,he would be left behind though:D
 

·
Registered
Joined
·
964 Posts
I always think the same when out with my Porsche friends, the 997TurboS leaves me hanging on until I can stretch the 12C legs, mid range it then catches- but in fairness the numbers are all very similar when up in this spec of car.
Where the 12C amazed was through the wider twisty bends where it was inspirational and was crawling all over the back of the 911.
I posted a video and you can see how easy it was to close up or drop back.
I had one of the owners in with me and they felt that the 12C was slower and that it didn't give you that Turbo rush, this could be down to lack of lag or it just doesn't give the feel as much.

0-60 I find the 12C disappointing, however that's certainly not what I bought the car for.:)
 

·
Registered
Joined
·
4,325 Posts
Gearing as well probably has something to do with it rather than just torque as far as accelerating in a straight line is concerned.
 

·
Registered
Joined
·
218 Posts
the mclaren engine runs like an NA engine being that it is a high revving turbo engine (8500rpm) so there is so much more power on mid-top range, rather than low-mid. the porsche turbo engine redlines at 6500rpm while the GTR is 7000rpm. it really is surprising how much more power is up top with the mclaren whereas the other turbo cars die out when reaching the rev limiter.
 

·
Registered
Joined
·
1,459 Posts
I always think the same when out with my Porsche friends, the 997TurboS leaves me hanging on until I can stretch the 12C legs, mid range it then catches- but in fairness the numbers are all very similar when up in this spec of car.
Where the 12C amazed was through the wider twisty bends where it was inspirational and was crawling all over the back of the 911.
I posted a video and you can see how easy it was to close up or drop back.
I had one of the owners in with me and they felt that the 12C was slower and that it didn't give you that Turbo rush, this could be down to lack of lag or it just doesn't give the feel as much.

0-60 I find the 12C disappointing, however that's certainly not what I bought the car for.:)
Fiskegt HELP. have you seen his 0-60 n quarter mi times:eek:
 

·
Registered
Joined
·
6,889 Posts
I thought bore and stroke configuration had something to do with it, no? i.e. a 6 cyl with larger diameter cylinder and shorter piston travel is better for low-end torque. Off base?
 

·
Owner
Joined
·
544 Posts
Discussion Starter #10
I thought bore and stroke configuration had something to do with it, no? i.e. a 6 cyl with larger diameter cylinder and shorter piston travel is better for low-end torque. Off base?
I too thought that it had something to do with the fact that its only a 3.8 litre and the GTR is 3.7 litres, whereas these monster AMG engines with 6.2 litres have so much torque
 

·
Registered
Joined
·
4,325 Posts
I thought bore and stroke configuration had something to do with it, no? i.e. a 6 cyl with larger diameter cylinder and shorter piston travel is better for low-end torque. Off base?
Some proper engineer will correct me here I am sure but for a normally aspirated engine, I think torque is directly a function of capacity so all things being equal a larger capacity engine will always produce more torque than a smaller one. Forced induction generates loads more torque generally but I would assume the principle stands that a large capacity FI engine would be more easily tuned to produce high torque numbers than a smaller capacity one....
 

·
Registered
Joined
·
1,523 Posts
All I know is that I gave my friend a ride this weekend. His neck is still sore! ;) No need for more torque IMO, but if I was given more, I certainly would not turn it down.
 

·
Registered
Joined
·
14 Posts
I always think the same when out with my Porsche friends, the 997TurboS leaves me hanging on until I can stretch the 12C legs, mid range it then catches- but in fairness the numbers are all very similar when up in this spec of car.
Where the 12C amazed was through the wider twisty bends where it was inspirational and was crawling all over the back of the 911.
I posted a video and you can see how easy it was to close up or drop back.
I had one of the owners in with me and they felt that the 12C was slower and that it didn't give you that Turbo rush, this could be down to lack of lag or it just doesn't give the feel as much.

0-60 I find the 12C disappointing, however that's certainly not what I bought the car for.:)
3.0 secs is disappointing to you?
 

·
Registered
Joined
·
98 Posts
A friend of mine runs a GTR and i am always amazed at how well he can keep up with me, despite his car having only 480bhp. When however you compare the torque of both cars, they are very similar (around 440lbs). So why doesn't the 12c have more torque? Is it restricted by the engine size?
Yeah, but the McLaren revs to 8250 rpm, vs about 7000 in the GTR. Geared down to equal maximum speeds the McLaren would be ~525 lbft of peak torque vs the ~451 in the GTR, and looking at the dynos from customer cars it seems McLaren understate torque by about 30-40 lbft.

The GTR does well against more powerful cars because of it's AWD torque-vectoring system.
 

·
Registered
Joined
·
367 Posts
I thought long stroke = high torque (and rpm then is limited by piston speed).
That's why tractor/trailers are I-6. Fewer moving parts too, though issues with the diesel aren't identical to petrol.
 

·
Registered
Joined
·
98 Posts
I thought bore and stroke configuration had something to do with it, no? i.e. a 6 cyl with larger diameter cylinder and shorter piston travel is better for low-end torque. Off base?
Torque is generally a function of volumetric efficiency x displacement - losses. Volumetric efficiency is how much air they can fill the cylinders with. At peak torque, a four-valve engine with tuned intake harmonics can get around 100% of it's cylinders filled. Boosted cars can exceed 100% of bar. Better Low end torque comes from optimizing the camshaft/valves for lower rev ranges. If you have an engine that revs to 7000 and torque peaks at ~3500, it'll likely have roughly equal low and high end torque. In sports engines they push the torque peak higher so they can get more torque at higher revs, since torque x rpm = power.

With turbo engines this gets a little more complicated as you're dealing with centrifugal compressor flow charts on top of valve optimization for intake and exhaust flow. Better low end torque in turbo cars comes from turbos that are optimized for the exhaust flows of a certain rev range.

Stroke length is shortened to allow higher RPM ranges, and therefore more power for a given displacement since RPMxTorque=power. Generally speaking, and engine with a 2 inch stroke will be able to rev twice as high as an engine with a 4 inch stroke. A nice rule of thumb to use is multiply stroke(in mm) x RPM and you should get somewhere around 600000-700000. i.e. the 12C: 69.9x8500=594150
 

·
Registered
Joined
·
98 Posts
I thought long stroke = high torque (and rpm then is limited by piston speed).
That's why tractor/trailers are I-6. Fewer moving parts too, though issues with the diesel aren't identical to petrol.
Diesels use long strokes (overstroked) because they have much higher compression ratios(20+:1) and it's easier to design such with the geometry of reciprocating engines.
 

·
Registered
Joined
·
367 Posts
Diesels use long strokes (overstroked) because they have much higher compression ratios(20+:1) and it's easier to design such with the geometry of reciprocating engines.
Understood. Perhaps the BMW petrol I-6 better illustrates the point. Or have I confused peak torque and low end torque?
 
1 - 20 of 53 Posts
Top