RE: Toyota GT-86 Convertible: Revealed (sort of)
Discussion
BadBanshee said:
My point still stands.
Think about it. Changing up just before the limiter makes more of a difference to drag race times the higher in the rev range the peak torque figure appears. In a turbodiesel where peak torque is low down in the rev range, redlining it won't give you a significant acceleration advantage, in fact it could put you at an acceleration disadvantage.
Eh??Think about it. Changing up just before the limiter makes more of a difference to drag race times the higher in the rev range the peak torque figure appears. In a turbodiesel where peak torque is low down in the rev range, redlining it won't give you a significant acceleration advantage, in fact it could put you at an acceleration disadvantage.
Power is important when racing. You'd shift the same in a TD as a petrol. Remember HP= torque X rpm /5252
Meaning they are directly relevant.
300bhp/ton said:
Eh??
Power is important when racing. You'd shift the same in a TD as a petrol. Remember HP= torque X rpm /5252
Meaning they are directly relevant.
Power is important when racing? What does that even mean?Power is important when racing. You'd shift the same in a TD as a petrol. Remember HP= torque X rpm /5252
Meaning they are directly relevant.
I can only assume you mean you would redline a TD when racing aswell, as you certainly couldn't change up at the same rpm in a diesel. I'm not denying that you should redline a diesel in a drag race, if that's what you say. What I'm doubting is that it wouldn't make as much of a difference than redlining an NA petrol which has a peak torque figure that appears higher up in the rev range.
BadBanshee said:
Power is important when racing? What does that even mean?
I can only assume you mean you would redline a TD when racing aswell, as you certainly couldn't change up at the same rpm in a diesel. I'm not denying that you should redline a diesel in a drag race, if that's what you say. What I'm doubting is that it wouldn't make as much of a difference than redlining an NA petrol which has a peak torque figure that appears higher up in the rev range.
Sorry I'm a little lost on your point tbh, unless it's that a na petrol doesn't drive like a TD does??? I can only assume you mean you would redline a TD when racing aswell, as you certainly couldn't change up at the same rpm in a diesel. I'm not denying that you should redline a diesel in a drag race, if that's what you say. What I'm doubting is that it wouldn't make as much of a difference than redlining an NA petrol which has a peak torque figure that appears higher up in the rev range.
In which case you'd be correct - but can't fathom the relevance to the GT86.HP is like an expression of torque at rpms. And for a n/a 2.0 the GT86 does not lack torque vs other 2.0 litre na motors. Regardless of where peak torque is actually generated.
300bhp/ton said:
Sorry I'm a little lost on your point tbh, unless it's that a na petrol doesn't drive like a TD does??? In which case you'd be correct - but can't fathom the relevance to the GT86.
HP is like an expression of torque at rpms. And for a n/a 2.0 the GT86 does not lack torque vs other 2.0 litre na motors. Regardless of where peak torque is actually generated.
I'm not disputing anything you're saying. I'm on your side. You're totally oblivious to my intention to add an additional factor that could cause a magazine to get a better 0-60 time than the official 0-60 time. In which case you'd be correct - but can't fathom the relevance to the GT86.HP is like an expression of torque at rpms. And for a n/a 2.0 the GT86 does not lack torque vs other 2.0 litre na motors. Regardless of where peak torque is actually generated.
The peak torque figure tells you where the best slice of acceleration comes in at in the rev range, yes? If you're having a drag race, it would serve as a disadvantage if you didn't even reach that point in the rev range. Because peak torque in the GT86 comes in so high (6600rpm) it's easier to miss out and change up too early before hitting peak torque compared to, for example, an NA hot hatch with a peak torque at 4500rpm or a TD with peak torque at 2000rpm. For a sporty feel I feel this is a good thing about the GT86, IMO, as it makes chasing the redline more addictive, although I've never driven it to find out for sure.
I don't know how manufacturer's test their 0-60 times but I would guess that they're not as aggressive as they could be, which means they may not have even reached peak torque in their tests.
BadBanshee said:
I don't know how manufacturer's test their 0-60 times but I would guess that they're not as aggressive as they could be, which means they may not have even reached peak torque in their tests.
I would think manufacturers test their 0-60 times in a spectacularly aggressive manner with no mechanical sympathy at all, especially in a modestly powered, high revving car - high revs, sidestep the clutch, shift as close to the limiter as they can.BadBanshee said:
I'm not disputing anything you're saying. I'm on your side. You're totally oblivious to my intention to add an additional factor that could cause a magazine to get a better 0-60 time than the official 0-60 time.
The peak torque figure tells you where the best slice of acceleration comes in at in the rev range. If you're having a drag race, it would serve as a disadvantage if you didn't even reach that point in the rev range. Because peak torque in the GT86 comes in so high (6600rpm) it's easier to miss out and change up too early before hitting peak torque compared to, for example, an NA hot hatch with a peak torque at 4500rpm or a TD with peak torque at 2000rpm.
PEAK HP will offer maximum acceleration, but this will only be for a single rpm point. What you want is the highest average HP over your duration in gear.The peak torque figure tells you where the best slice of acceleration comes in at in the rev range. If you're having a drag race, it would serve as a disadvantage if you didn't even reach that point in the rev range. Because peak torque in the GT86 comes in so high (6600rpm) it's easier to miss out and change up too early before hitting peak torque compared to, for example, an NA hot hatch with a peak torque at 4500rpm or a TD with peak torque at 2000rpm.
Lots of torque at low revs can mean lots of HP.
Little torque at high revs can mean lots of HP.
But this is where gearing comes into it.
However just because an engine makes it's PEAK torque at high rpms doesn't mean you have to rev it to make it move.
For instance, in 1997/8 the Chevy LS1 replaced the LT1. Both 5.7 OHV V8's, but share almost no components or design.
Many people instantly jumped on the band wagon that the LS1 was gutless because it now made PEAK torque at 4400rpm instead of 2500rpm like the old LT1 did.
What these people failed to realise was, the LS1 made over 95% of it's torque at only 1500rpm and had an almost flat torque curve from 1500-5000rpm.
Also 95% of the LS1's torque was more than the LT1 could muster at PEAK, i.e. the LS1 @ 1500rpm makes more torque than the LT1 @ 2500pm PEAK. The reality is the LS1 isn't gutless compared to the LT1 but actually beats the crap out of it at any given rpm. But has the added ability to sustain the torque at higher rpm, thus makes quite a bit more PEAK HP too.
BadBanshee said:
I don't know how manufacturer's test their 0-60 times but I would guess that they're not as aggressive as they could be, which means they may not have even reached peak torque in their tests.
I would think testing procedures vary from maker to maker, and maybe even model to model. That said if you are at WOT and attain maximum rpm in gear you will make full use of the power and torque available from the engine.BadBanshee said:
300bhp/ton said:
PEAK HP will offer maximum acceleration
No it won't...So take a typical TD with peak power at 4000rpm and peak torque at 2000rpm. You're telling me acceleration will be greater at 4000rpm than at 2000rpm?
At any one speed, the car will be accelerating harder in the gear which results in it doing 4000rpm than the gear which results in it doing 2000rpm.
BadBanshee said:
No it won't...
So take a typical TD with peak power at 4000rpm and peak torque at 2000rpm. You're telling me acceleration will be greater at 4000rpm than at 2000rpm?
You are unlikely to get peak HP at 4000rpm and peak torque at 2000rpm unless it can sustain the torque curve higher up the rev range I'd have thought.So take a typical TD with peak power at 4000rpm and peak torque at 2000rpm. You're telling me acceleration will be greater at 4000rpm than at 2000rpm?
But as said, they are related to one another.
HP = torque x rpm / 5252
So lets add some figures
300lb ft x 2000rpm / 5252 = 114bhp
300lb ft x 4000rpm / 5252 = 229bhp
200lb ft x 4000rpm / 5252 = 152bhp
150lb ft x 7700rpm / 5252 = 220bhp
As a rule a diesel makes more torque at a lower rpm, more torque means more HP for a given rpm. As diesels don't rev as high and the torque curve drops off they tend to perform less well at high revs.
Torque might be the pulling force, but it's power that dictates at what speed it can do it.
300bhp/ton said:
You are unlikely to get peak HP at 4000rpm and peak torque at 2000rpm unless it can sustain the torque curve higher up the rev range I'd have thought.
But as said, they are related to one another.
HP = torque x rpm / 5252
So lets add some figures
300lb ft x 2000rpm / 5252 = 114bhp
300lb ft x 4000rpm / 5252 = 229bhp
200lb ft x 4000rpm / 5252 = 152bhp
150lb ft x 7700rpm / 5252 = 220bhp
As a rule a diesel makes more torque at a lower rpm, more torque means more HP for a given rpm. As diesels don't rev as high and the torque curve drops off they tend to perform less well at high revs.
Torque might be the pulling force, but it's power that dictates at what speed it can do it.
Example of a single-turbo diesel with peak torque at 1750-2500rpm and peak power at 4200rpm:But as said, they are related to one another.
HP = torque x rpm / 5252
So lets add some figures
300lb ft x 2000rpm / 5252 = 114bhp
300lb ft x 4000rpm / 5252 = 229bhp
200lb ft x 4000rpm / 5252 = 152bhp
150lb ft x 7700rpm / 5252 = 220bhp
As a rule a diesel makes more torque at a lower rpm, more torque means more HP for a given rpm. As diesels don't rev as high and the torque curve drops off they tend to perform less well at high revs.
Torque might be the pulling force, but it's power that dictates at what speed it can do it.
http://www.carmagazine.co.uk/Drives/Search-Results...
I was under the impression most modern turbodiesels had a peak power figure somewhere around the 4000rpm mark. I don't know why you found that hard to believe...
300bhp/ton, just entertain this thought:
Car A and Car B, both made by the same manufacturer, therefore tested by the same guys. Both have been given a 0-60 time of 8 seconds flat.
Let's say the guys who tested both cars went from 0rpm to 6500rpm in 1st gear and then reached 60mph whilst in 2nd gear at w/e rpm (I don't think it matters).
Now let's say Car A reaches peak torque at 6200rpm and Car B reaches peak torque at 6800rpm.
Then a magazine comes along to do their own 0-60 tests on these cars, but they rev to 7000rpm in 1st gear, for both cars.
Would you agree that their 0-60 time will be improved in both cars but by more in the car with peak torque at 6800rpm? Or not necessarily so?
I think a fair result may be that Car A did 0-60 in 7.6 seconds and Car B did it in 7.4 seconds perhaps?
Car A and Car B, both made by the same manufacturer, therefore tested by the same guys. Both have been given a 0-60 time of 8 seconds flat.
Let's say the guys who tested both cars went from 0rpm to 6500rpm in 1st gear and then reached 60mph whilst in 2nd gear at w/e rpm (I don't think it matters).
Now let's say Car A reaches peak torque at 6200rpm and Car B reaches peak torque at 6800rpm.
Then a magazine comes along to do their own 0-60 tests on these cars, but they rev to 7000rpm in 1st gear, for both cars.
Would you agree that their 0-60 time will be improved in both cars but by more in the car with peak torque at 6800rpm? Or not necessarily so?
I think a fair result may be that Car A did 0-60 in 7.6 seconds and Car B did it in 7.4 seconds perhaps?
The manufacturers will try to optimise their shift points and starting revs to get the best result they can.
It will never be worth shifting before peak power.
It may be worth holding on to the gear beyond peak power, depending on how quickly torque is falling away and where in the torque curve the next gear will land - essentially, a question of whether any of the lines in a chart like the one below cross:
(none of these do - in both of the cars shown below, you change up at the rev limiter in every gear for maximum performance)
It will never be worth shifting before peak power.
It may be worth holding on to the gear beyond peak power, depending on how quickly torque is falling away and where in the torque curve the next gear will land - essentially, a question of whether any of the lines in a chart like the one below cross:
(none of these do - in both of the cars shown below, you change up at the rev limiter in every gear for maximum performance)
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