Vtec?
- Thread starter Applemobile
- Start date
I like both but I do side more with turbo'd motors, torque makes so much difference to daily driving. I never really used my RX8 for the commute (2 or 3 times tops), just used it for ragging the **** out of on evenings and weekends.
I wouldn't say v-tec is crap but I think you're fooling yourself if you think they're a lot better than other options, the 1.8 16v in the Mk2 golf gti for instance was a superb engine, loads of poke especially considering it's old school now. All I would say is don't rush into it thinking it'll be all that, you also have to think of power to weight ratios, that makes a huge difference to the feel of the car. You'd be better looking back through some of the older threads on here at what other people have done regarding taking a 16v engine and whacking on a big turbo, I was just reading one last night and it was pretty awesome.
All this talk about torque means it's time to dust off the old lecture again.
Power(bhp)=Torque(lb-ft) x rpm/5252
If you have power, you have torque. No way around it.
Torque is a measure of the amount of push the charge in the cylinder is giving to the crankshaft. In technical terms this is BMEP (Brake Mean Effective Pressure) - a measure of the pressure generated in the cylinder head when the fuel-air charge burns. How much bang it makes, if you like.
This is why larger displacement = more "urge" at low revs, which is often erroneously called "torque", as if that were all it was. More charge = bigger bangs, you see.
The "BHp" figure on the spec sheet is found at the top end of the rev range (notice that rpm is a factor in the equation above). As long as the torque, i.e. the bang from the fuel/air mixture burning in the cylinder, is sustained, peak rpm is limited by mechanical factors, often valve bounce.
In a petrol car, rpm can be increased to ridiculous levels (20,000 or more in F1 engines) provided all the whirling bits are balanced very well, the gas flow all through the engine is good and the ignition can keep up. Increasing rpm is a prime factor in getting more rated power out of petrol engines. Of course this means you have to wring its neck to get that power and go around sounding like a banshee out of hell.
Vtec helps a small-displacement car get to a bigger max-bhp figure by changing to a power-optimised cam profile at high rpm. In order to make use of it you have to be high in the rev range, but that's true of any engine - to get that max-bhp figure you have to be revving as high as you can get.
Turbocharging increases the amount of charge in the cylinder, so making a bigger bang. It doesn't work so well at very low revs, but can be arranged to provide max torque through a large part of the rev range. An LC or LCR makes practically the same torque from 2000 rpm up to 6000 - the ECU limits the turbo boost so as not to overstress the engine. But it's the bigger bang that increases the max-bhp figure, and a turbocharged engine (or a supercharged one, for that) has the bigger bang.
By the way, Applemobile is playing at being a troll.
Power(bhp)=Torque(lb-ft) x rpm/5252
If you have power, you have torque. No way around it.
Torque is a measure of the amount of push the charge in the cylinder is giving to the crankshaft. In technical terms this is BMEP (Brake Mean Effective Pressure) - a measure of the pressure generated in the cylinder head when the fuel-air charge burns. How much bang it makes, if you like.
This is why larger displacement = more "urge" at low revs, which is often erroneously called "torque", as if that were all it was. More charge = bigger bangs, you see.
The "BHp" figure on the spec sheet is found at the top end of the rev range (notice that rpm is a factor in the equation above). As long as the torque, i.e. the bang from the fuel/air mixture burning in the cylinder, is sustained, peak rpm is limited by mechanical factors, often valve bounce.
In a petrol car, rpm can be increased to ridiculous levels (20,000 or more in F1 engines) provided all the whirling bits are balanced very well, the gas flow all through the engine is good and the ignition can keep up. Increasing rpm is a prime factor in getting more rated power out of petrol engines. Of course this means you have to wring its neck to get that power and go around sounding like a banshee out of hell.
Vtec helps a small-displacement car get to a bigger max-bhp figure by changing to a power-optimised cam profile at high rpm. In order to make use of it you have to be high in the rev range, but that's true of any engine - to get that max-bhp figure you have to be revving as high as you can get.
Turbocharging increases the amount of charge in the cylinder, so making a bigger bang. It doesn't work so well at very low revs, but can be arranged to provide max torque through a large part of the rev range. An LC or LCR makes practically the same torque from 2000 rpm up to 6000 - the ECU limits the turbo boost so as not to overstress the engine. But it's the bigger bang that increases the max-bhp figure, and a turbocharged engine (or a supercharged one, for that) has the bigger bang.
By the way, Applemobile is playing at being a troll.
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This is amazing!!! not been in here for a few days and just laughed my tits off..........................
Ive owned a Civic 1.6 vti, used my dads Civic Type R for awhile before deciding to buy my Leon.
Loved the CTR for noise and fun but for everyday driving round town for work love my Leon to bit just for the torque in and out of traffic and playin with all the posh nobs from the lights.
I have not problem with people liking vtec cars/engines(i do myself)
Ive owned a Civic 1.6 vti, used my dads Civic Type R for awhile before deciding to buy my Leon.
Loved the CTR for noise and fun but for everyday driving round town for work love my Leon to bit just for the torque in and out of traffic and playin with all the posh nobs from the lights.
I have not problem with people liking vtec cars/engines(i do myself)
Pyro
Guest
All this talk about torque means it's time to dust off the old lecture again.
Power(bhp)=Torque(lb-ft) x rpm/5252
If you have power, you have torque. No way around it.
Torque is a measure of the amount of push the charge in the cylinder is giving to the crankshaft. In technical terms this is BMEP (Brake Mean Effective Pressure) - a measure of the pressure generated in the cylinder head when the fuel-air charge burns. How much bang it makes, if you like.
This is why larger displacement = more "urge" at low revs, which is often erroneously called "torque", as if that were all it was. More charge = bigger bangs, you see.
The "BHp" figure on the spec sheet is found at the top end of the rev range (notice that rpm is a factor in the equation above). As long as the torque, i.e. the bang from the fuel/air mixture burning in the cylinder, is sustained, peak rpm is limited by mechanical factors, often valve bounce.
In a petrol car, rpm can be increased to ridiculous levels (20,000 or more in F1 engines) provided all the whirling bits are balanced very well, the gas flow all through the engine is good and the ignition can keep up. Increasing rpm is a prime factor in getting more rated power out of petrol engines. Of course this means you have to wring its neck to get that power and go around sounding like a banshee out of hell.
Vtec helps a small-displacement car get to a bigger max-bhp figure by changing to a power-optimised cam profile at high rpm. In order to make use of it you have to be high in the rev range, but that's true of any engine - to get that max-bhp figure you have to be revving as high as you can get.
Turbocharging increases the amount of charge in the cylinder, so making a bigger bang. It doesn't work so well at very low revs, but can be arranged to provide max torque through a large part of the rev range. An LC or LCR makes practically the same torque from 2000 rpm up to 6000 - the ECU limits the turbo boost so as not to overstress the engine. But it's the bigger bang that increases the max-bhp figure, and a turbocharged engine (or a supercharged one, for that) has the bigger bang.
By the way, Applemobile is playing at being a troll.
very very good copied and saved 
All this talk about torque means it's time to dust off the old lecture again.
Power(bhp)=Torque(lb-ft) x rpm/5252
If you have power, you have torque. No way around it.
Torque is a measure of the amount of push the charge in the cylinder is giving to the crankshaft. In technical terms this is BMEP (Brake Mean Effective Pressure) - a measure of the pressure generated in the cylinder head when the fuel-air charge burns. How much bang it makes, if you like.
This is why larger displacement = more "urge" at low revs, which is often erroneously called "torque", as if that were all it was. More charge = bigger bangs, you see.
The "BHp" figure on the spec sheet is found at the top end of the rev range (notice that rpm is a factor in the equation above). As long as the torque, i.e. the bang from the fuel/air mixture burning in the cylinder, is sustained, peak rpm is limited by mechanical factors, often valve bounce.
In a petrol car, rpm can be increased to ridiculous levels (20,000 or more in F1 engines) provided all the whirling bits are balanced very well, the gas flow all through the engine is good and the ignition can keep up. Increasing rpm is a prime factor in getting more rated power out of petrol engines. Of course this means you have to wring its neck to get that power and go around sounding like a banshee out of hell.
Vtec helps a small-displacement car get to a bigger max-bhp figure by changing to a power-optimised cam profile at high rpm. In order to make use of it you have to be high in the rev range, but that's true of any engine - to get that max-bhp figure you have to be revving as high as you can get.
Turbocharging increases the amount of charge in the cylinder, so making a bigger bang. It doesn't work so well at very low revs, but can be arranged to provide max torque through a large part of the rev range. An LC or LCR makes practically the same torque from 2000 rpm up to 6000 - the ECU limits the turbo boost so as not to overstress the engine. But it's the bigger bang that increases the max-bhp figure, and a turbocharged engine (or a supercharged one, for that) has the bigger bang.
By the way, Applemobile is playing at being a troll.
Power = Torque aint exactly right.
The wife had a 2008 Yaris 1.4 D4D putting out just 90bhp but 140lbs/ft or torque. The RX8 i had was putting out 231bhp but just 156lbs/ft so loads more power but not much more torque. Compared with the Cupra 20VT i had putting out 180bhp and 179lbs/ft so less power but more torque than the RX8.
Dabbalz wrote
Power = Torque aint exactly right.
For $Deitys sake, Dabblaz, read what I wrote
Power(bhp)=Torque(lb-ft) x rpm/5252
or to put it more succinctly
P=TxR/5252
where
P=Power
T=Torque
and
R=Engine RPM
Of Course Power = Torque isn't right. They aren't even measured in the same units, which should be a clue.
The wife had a 2008 Yaris 1.4 D4D putting out just 90bhp but 140lbs/ft or torque. The RX8 i had was putting out 231bhp but just 156lbs/ft so loads more power but not much more torque. Compared with the Cupra 20VT i had putting out 180bhp and 179lbs/ft so less power but more torque than the RX8.
You have completely missed the point, by leaving out the other significant parameter, engine rpm.
Yaris 1.4 D4D (a turbodiesel, so bigger bangs)
88bhp at 3800 rpm
140 lb-ft at 2000 rpm
The other part of my lecture, which I snipped as irrelevant to the VTEC argument, is about how diesels have high compression ratios (even higher with a turbocharger) so make very big bangs (high torque, from quite low down too) BUT can't be revved much past 4000 rpm, even with serious tuning, because the flame front propagation in the charge is too slow, so try to increase the revs and you start letting the bang out before it's finished - the evidence of this is the sooty trail of partly burned fuel.
The RX8 is of course a Wankel so plays by different rules. The nominal displacement is 1.3 litres but it goes bang more often than the equivalent piston engine.
Mazda RX-8
Horsepower 232 at 8500 rpm
Torque (lb-ft) 159 at 5500 rpm
You would never get a diesel to generate useful power at even 5500 rpm. The Wankel's maximum power is so high because it can spin to a much higher rpm while still providing torque.
Finally the LC
Leon Cupra Mk.1
180 bhp at 5900 rpm, by generating 160 lb-ft of torque.
173 ft-lb at 2000 rpm, generating 66 bhp
If you've studied those figures well you should be getting a clue about now.
Everybody, and their dog, and probably the fleas on the dog as well, "knows what power is" because the max bhp figure is what's always quoted to sell cars. The rpm at which that power is generated is buried in the small print, next to the torque figure, because torque is "too hard to understand". In most cases, "torque" is usually talked about in terms of acceleration away from a standing start, or at low speeds.
Engines that develop their peak power at high rpm will always feel feebler at town speeds than an engine that develops the same power at a lower rpm. The classic case is petrol vs. diesel. At 2000 rpm, my 1.9 TDI 110 develops the same torque as your LC, 173 ft-lb, so I have the same power at 2000 rpm, 66 BHP, as you do. I'll have to change gear first, though, because my engine runs out of puff at 4000 rpm and yours goes on until 6000.
A better comparison would be between my car and a normally-aspirated 1.8, say the AGN in a Leon.
AGN
125 BHP at 5900 rpm
126 lb-ft at 3500 rpm
Lets be generous and say he holds peak torque all the way down to 2000 rpm. He'd be generating 48 BHP if he could do that. In reality, it will be less.
ASV
110 BHP at 3750 rpm
173 at 2000 rpm
At 2000 rpm I'm generating 66 BHP. I've got at least 30% more power at 2000 rpm than the nominally more powerful 1.8 petrol engine.
The diesel is closer to its max power rpm at ordinary traffic speeds, that's why it feels like it has more power: - because it really does.
Power = Torque aint exactly right.
For $Deitys sake, Dabblaz, read what I wrote
Power(bhp)=Torque(lb-ft) x rpm/5252
or to put it more succinctly
P=TxR/5252
where
P=Power
T=Torque
and
R=Engine RPM
Of Course Power = Torque isn't right. They aren't even measured in the same units, which should be a clue.
The wife had a 2008 Yaris 1.4 D4D putting out just 90bhp but 140lbs/ft or torque. The RX8 i had was putting out 231bhp but just 156lbs/ft so loads more power but not much more torque. Compared with the Cupra 20VT i had putting out 180bhp and 179lbs/ft so less power but more torque than the RX8.
You have completely missed the point, by leaving out the other significant parameter, engine rpm.
Yaris 1.4 D4D (a turbodiesel, so bigger bangs)
88bhp at 3800 rpm
140 lb-ft at 2000 rpm
The other part of my lecture, which I snipped as irrelevant to the VTEC argument, is about how diesels have high compression ratios (even higher with a turbocharger) so make very big bangs (high torque, from quite low down too) BUT can't be revved much past 4000 rpm, even with serious tuning, because the flame front propagation in the charge is too slow, so try to increase the revs and you start letting the bang out before it's finished - the evidence of this is the sooty trail of partly burned fuel.
The RX8 is of course a Wankel so plays by different rules. The nominal displacement is 1.3 litres but it goes bang more often than the equivalent piston engine.
Mazda RX-8
Horsepower 232 at 8500 rpm
Torque (lb-ft) 159 at 5500 rpm
You would never get a diesel to generate useful power at even 5500 rpm. The Wankel's maximum power is so high because it can spin to a much higher rpm while still providing torque.
Finally the LC
Leon Cupra Mk.1
180 bhp at 5900 rpm, by generating 160 lb-ft of torque.
173 ft-lb at 2000 rpm, generating 66 bhp
If you've studied those figures well you should be getting a clue about now.
Everybody, and their dog, and probably the fleas on the dog as well, "knows what power is" because the max bhp figure is what's always quoted to sell cars. The rpm at which that power is generated is buried in the small print, next to the torque figure, because torque is "too hard to understand". In most cases, "torque" is usually talked about in terms of acceleration away from a standing start, or at low speeds.
Engines that develop their peak power at high rpm will always feel feebler at town speeds than an engine that develops the same power at a lower rpm. The classic case is petrol vs. diesel. At 2000 rpm, my 1.9 TDI 110 develops the same torque as your LC, 173 ft-lb, so I have the same power at 2000 rpm, 66 BHP, as you do. I'll have to change gear first, though, because my engine runs out of puff at 4000 rpm and yours goes on until 6000.
A better comparison would be between my car and a normally-aspirated 1.8, say the AGN in a Leon.
AGN
125 BHP at 5900 rpm
126 lb-ft at 3500 rpm
Lets be generous and say he holds peak torque all the way down to 2000 rpm. He'd be generating 48 BHP if he could do that. In reality, it will be less.
ASV
110 BHP at 3750 rpm
173 at 2000 rpm
At 2000 rpm I'm generating 66 BHP. I've got at least 30% more power at 2000 rpm than the nominally more powerful 1.8 petrol engine.
The diesel is closer to its max power rpm at ordinary traffic speeds, that's why it feels like it has more power: - because it really does.
I stand by everything i have said in this thread.
Pyro
Guest
just to put another factor into the equation:
A gearbox is effectively a torque converter. That is to say the torque the engine is putting out isnt what ends up being delivered to the wheels.
So an engine that can achieve high rpm, but ultimately is less powerful can actually be faster in the real world as the engine power at a set speed may be converted less via the gearbox.
A gearbox is effectively a torque converter. That is to say the torque the engine is putting out isnt what ends up being delivered to the wheels.
So an engine that can achieve high rpm, but ultimately is less powerful can actually be faster in the real world as the engine power at a set speed may be converted less via the gearbox.
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