Torque Query

[boyley]

The following is the standard quoted figures for a VY SS Engine

Maximum power: 245 kW @ 5600 rpm
Maximum torque: 465 Nm @ 4000 rpm

When drag racing does one change gears at 4000 rpm or 5600 rpm?

[Sid447]

The following is the standard quoted figures for a VY SS Engine

Maximum power: 245 kW @ 5600 rpm
Maximum torque: 465 Nm @ 4000 rpm

When drag racing does one change gears at 4000 rpm or 5600 rpm?

Suggest you need to do a fair bit of reading about engines!

This query should be in the "General" part of the Forum

[HRT 8]

In your auto it isnt going to matter. You cant shift early without lifting your foot.

Stock values have the car changing gears between 5500 and 6000 for the first 3 gears.

The times to change gear is a tradeoff between holding too long and power tq dropping off too far and having the car select another gear too early and not being in your peak power tq area.

[boyley]

Suggest you need to do a fair bit of reading about engines!

This query should be in the "General" part of the Forum

Says who? I believe this is a technical question.


In your auto it isnt going to matter. You cant shift early without lifting your foot.

Stock values have the car changing gears between 5500 and 6000 for the first 3 gears.

The times to change gear is a tradeoff between holding too long and power tq dropping off too far and having the car select another gear too early and not being in your peak power tq area.

So basically the difference in a stock car between an experienced driver and a lamen is negligible?

[RB30X]

The following is the standard quoted figures for a VY SS Engine

Maximum power: 245 kW @ 5600 rpm
Maximum torque: 465 Nm @ 4000 rpm

When drag racing does one change gears at 4000 rpm or 5600 rpm?

They say the power band of an engine is between where it makes the most torque and where it makes its most power. If you change gears at 5600rpm your revs shouldn't drop below 4000 (I'd be worried if they did) so you're well within this range. Changing at 4000 means it will fall below this range and bog down which isn't cool when drag racing.

[nudenut]

Gearing acts as a torque multiplier - that's why you get pinned back into the seat more in 1st than 5th.

A typical ratio between gears (in the M6 anyway) is about 0.75, so after changing you're doing 75% of the revs you were doing beforehand. It also means that in the higher gear, you're only feeling 75% of the "push" you were feeling at the same revs in the lower gear.

So - you'd change at 5,333 RPM to hit peak torque (4000RPM) in the next gear. In the lower gear at 5,333RPM, though, your engine is still putting out more than 75% of peak (4000RPM) torque, so you're better off holding on for a bit longer. Exactly how long depends on the torque curve of your engine, but by the time you hit peak power, torque is dropping off pretty quickly, so it's probably not bad as a rule of thumb.

As HRT 8 said, though, in an auto it's a moot point.

[boyley]

Gearing acts as a torque multiplier - that's why you get pinned back into the seat more in 1st than 5th.

A typical ratio between gears (in the M6 anyway) is about 0.75, so after changing you're doing 75% of the revs you were doing beforehand. It also means that in the higher gear, you're only feeling 75% of the "push" you were feeling at the same revs in the lower gear.

So - you'd change at 5,333 RPM to hit peak torque (4000RPM) in the next gear. In the lower gear at 5,333RPM, though, your engine is still putting out more than 75% of peak (4000RPM) torque, so you're better off holding on for a bit longer. Exactly how long depends on the torque curve of your engine, but by the time you hit peak power, torque is dropping off pretty quickly, so it's probably not bad as a rule of thumb.

As HRT 8 said, though, in an auto it's a moot point.

So at the end of the day, its better to develope max torque higher in the rev range and horsepower is a result of torque?

[nudenut]

So at the end of the day, its better to develope max torque higher in the rev range and horsepower is a result of torque?
Horsepower = torque x engine speed, so developing your peak torque at high RPM will give maximum horsepower.

As for what's "better" - it's all a tradeoff. For real world driving, you probably want a fatter torque curve down low for instant "go" without having to rev its tits off (not that there's anything wrong with that :jester:). Down the quarter, you'd want a good torque band between redline and (roughly) 75% of redline. (Plus a reasonable spread of torque at lower RPM to help with launching.)

[boyley]

Horsepower = torque x engine speed, so developing your peak torque at high RPM will give maximum horsepower.

As for what's "better" - it's all a tradeoff. For real world driving, you probably want a fatter torque curve down low for instant "go" without having to rev its tits off (not that there's anything wrong with that :jester:). Down the quarter, you'd want a good torque band between redline and (roughly) 75% of redline. (Plus a reasonable spread of torque at lower RPM to help with launching.)


Thanks nudenut its guys like you that make forums worthwhile.