Torque vs kW

[Naks]

Actually - good question.

I've never driven a turbo car and should be collecting one today or tomorrow. So other than the idling after driving - anything else I should watch out for?

TurboDiesel or TurboPetrol? Big difference in driving styles and maintenance care required.

I can only comment on TD:

1. Regular oil changes. If your maintenance plan says service intervals at 15Kkm, change the engine oil every 7.5Kkm. Find out what oil they use and stick to it.

2. Always let your turbo spool down after a long/hard run by letting the engine idle for a few minutes.

how many of us drive long distance for the summer holidays, need to pee and pull into a petrol station and switch off to run to the loo? Don't

3. Fit an EGT if you can to prolong the engine.

4. Use low sulphur diesel

5. Remove the catalytic converter and/or middle silencer box and replace with a straight through pipe.

This will help reduce EGT, turbo will spool up faster and performance will increase.

best bang for buck performance upgrade on any TD

 

[Dolby]

Oh - turbo petrol ...

I'll google :/

 

[Dolby]

how many of us drive long distance for the summer holidays, need to pee and pull into a petrol station and switch off to run to the loo? Don't

You live in South Africa too, right?

 

[Naks]

You live in South Africa too, right?

hehe, indeed.

The reason I say don't is because of this:

In december 06 SWAMBO and I were driving from Grahamstown to JHB in her Freelander Td4. We both needed to pee really badly. So we pulled into the Shell outside Colesberg and ran to the loo without idling the car. Ambient temperature that day was around 38C.

When we got to Alberton later that day, we stopped to see some friends. When we restarted the car... *poof* went the turbo. We didn't notice because it was already dark. She took me to the airport the next morning and there were black clouds of diesel pouring out of the exhaust.

sold the Freelander and got an Audi A3

 

[ALFAHOLIC]

yep...oil and turbo seals...just spoke to mate now he has S3...he's is smoking on pullaway, he did a copmression test so its not rings or seals, but if it persists it might be turbo seals...aparently R5000!

 

[scotty777]

you guys understand that KW= the POWER of the car, or, is just means that amount of energy the car(engine) makes. So higher KW means you produce more ENERGY, thus car goes faster.

Toque is the about of leverage the car's engine makes, or how much it "pulls". More torque means more pulling power, almost means that you can muscle through more resistance.

 

[Paul_S]

Torque (Nm) is the amount of twisting force that the engine puts out via the crankshaft.
Power (kW) is torque at a given RPM
Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488

A vehicle that has an engine that puts out 250nM of torque can still get thrashed by a vehicle with an engine that puts out 150nM of torque if can rev high enough.
A torquey engine is a lot more pleasant to drive because you don't have to rev it much but a low torque high reving engine can still win in terms of performance.

Example:
A Polo 1.9 TDI puts out maximum power of 96kW at 4000 RPM.
That means the engine is producing 229.17 Nm at 4000 RPM (far from it's maximum of 310Nm at 1800-2400rpm)
Let say that 3rd gear at 4000RPM = 100km/h

Along comes Mr Boksburg with his tuned NA screamer that puts at 150Nm at the 8000RPM redline. His engine is putting out 125.67kW
Let say that his 3rd gear at 8000RPM = 100km/h

Assuming an equal tire size of 2 meter circumference that means that the final gearbox ratio of the TDI is 4.8:1 and the Boksburg special 9.6:1

Assuming no losses in the drive chain:
The torque at the wheels of the TDI : 1100 Nm
The torque at the wheels of the screamer : 1440 Nm

The screamer will drop the TDI because it it generating more power (which the gearbox is converting into more torque) at a higher RPM.

At the end of the day it's the amount of power (kW) that an engine can deliver that makes the difference because the gearbox is essentially just a torque converter.

 

[LCBXX]

Exhaust Gas Temperature

A diesel pushes out EGT at far higher temps than a petrol engine. It is not uncommon for the EGT on a TD to be pushing close to 750C after a 'spirited' drive uphill.

You can get EGT monitors from various places like Autostyle, but I would recommend you get one fitted by an experienced TD mechanic. I have one of these in my landy: http://www.landyonline.co.za/workshop/engine_instruments/egt_gauges.html.

Some people fit the EGT probes & gauges from avionics shops.

The EGT of a petrol engined car is FAR higher than that of a diesel. Diesel combustion is cooler but releases more energy per volume of fuel. Even a high-boost turbodiesel like a BMW has a cooler EGT than a 1300 petrol engined car.
http://www.tdiclub.com/TDIFAQ/TDiFAQ-6.html#e15

 

[Dolby]

I'm Mr Boksburg in that example

Paul S - do you have an ST?

 

[alpine]

you guys understand that KW= the POWER of the car, or, is just means that amount of energy the car(engine) makes. So higher KW means you produce more ENERGY, thus car goes faster.

Toque is the about of leverage the car's engine makes, or how much it "pulls". More torque means more pulling power, almost means that you can muscle through more resistance.

so in human terms kw= kj(energy) torque = muscle(strength)

 

[Gnome]

@Paul_S: Good explanation!

Also another thing that many people don't consider is that shifting makes a huge difference. Take a car that has a red-line of 9000rpm, the guy in the the standard TDi has most likely shifted twice already at the limiter before the 9000rever shifts once. Each time you shift it means precious loss of torque while the shifting is being done (they are working on transmission that have no loss of torque while you shift).

Lastly many Diesel guys claim that they like it because it's faster off the block but it's not generally my observation of things, which is also backed by the relatively slow 0-100 times of Turbo Diesels in comparison with Turbo Petrol or high-revving Petrol N/A.

The reason is once again that the gearbox is a torque converter, guy X has a 9000rpm revver and in 1st he revved to 9000rpm, that car made a hell of a lot of power, in 2nd he made it once again to 9000rpm at which point he is probably at 100km/h or close to it. If you've ever driven a high-revving performance petrol car you'll know that they rev incredibly quickly, it's nothing like a diesel that's slow to rev. You can test it for yourself by putting a diesel in neutral and revving it then compare it to a high-revving petrol. Then also remember the fact that the petrol engine has a close ratio gearbox so it's a no brainer which is faster off the block.

And in case of Turbo Petrol, the newer Turbo Petrol engines generally make maximum torque from around 1500-2000rpm all the way very close to peak power where on the other hand Turbo Diesels make peak Torque low in the range, usually also 1500 - 2000rpm for a inline 4 but after that the torque drops off as the engine approaches peak power.

Because a Turbo Diesel has a rev limit of around 5000rpm their peak power is usually very low in the range (say 4000rpm), and I don't know if I need to mention this but peak power is by definition after peak torque not before. My point? The Turbo Diesel had a huge peak torque early on but it quickly dropped off, the Turbo Petrol had it just as early but torque was less, upside is it kept that torque for almost twice as long as the Turbo Diesel's had long since dropped off.

N/A Petrol generally make their peak torque very high in the range, like 5000-6000rpm but I'd also like to point out that those engines generally make a large amount of torque, once again because at 5000rpm the engine is flowing a very large amount of air. Turbo Diesels have trouble keeping up with them never mind N/A Diesel (which I think it is fair to mention as those Petrol engines don't have Turbos)

 

[ALFAHOLIC]

Yep...mate has a modified Nord engine that revs to 7500rpm...a bloody 1600!!!

It gets from 1000 to 7500 rpm SOOO Quickely its unbelievable!

 

[Gnome]

Yep that's the on thing the Torque figure can't tell you, ok sure the car makes X torque at Y RPM. Problem is how long does it take to get there, even if there is no load on the engine. On diesels it generally revs very slowly.

Turbo Petrol rev very quickly and especially N/A Petrol engines running ITB's but I won't bring those up it's not fair to the diesel guys

You have to look at the 0-100 time and the peak torque/power. Any one of those figures alone don't tell the tale.

Btw. smaller displacement engines generally rev higher with much more ease than high displacement so it's not really a surprise that a 1600 could do that. If you look at the Super 1600 you'll see just how those engines rev. For example Opel EcoTec 1600 generally rev to 9000rpm with some hitting 10 000rpm with the standard crankshaft.

 

[Dolby]

I have a Toyota RunX RSI which redlines at 8200rpm - has 141KW and 180nm. Also on the reef (1.8km above sea level)

Generally most turbo diesel cars jump me on pull off by around a car length or so - but after that initial few seconds, I'm generally pulling away. You have no idea how many arguments I've had with people saying I'd never take a Polo 1.9TDI :/

My previous Corolla RSI was a 1600 demon at 115KW and about 140nm torque. I had to drive the car hard, but it got awesome results for a 1.6 ...

 

[xrapidx]

Torque (Nm) is the amount of twisting force that the engine puts out via the crankshaft.
Power (kW) is torque at a given RPM
Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488

A vehicle that has an engine that puts out 250nM of torque can still get thrashed by a vehicle with an engine that puts out 150nM of torque if can rev high enough.
A torquey engine is a lot more pleasant to drive because you don't have to rev it much but a low torque high reving engine can still win in terms of performance.

Example:
A Polo 1.9 TDI puts out maximum power of 96kW at 4000 RPM.
That means the engine is producing 229.17 Nm at 4000 RPM (far from it's maximum of 310Nm at 1800-2400rpm)
Let say that 3rd gear at 4000RPM = 100km/h

Along comes Mr Boksburg with his tuned NA screamer that puts at 150Nm at the 8000RPM redline. His engine is putting out 125.67kW
Let say that his 3rd gear at 8000RPM = 100km/h

Assuming an equal tire size of 2 meter circumference that means that the final gearbox ratio of the TDI is 4.8:1 and the Boksburg special 9.6:1

Assuming no losses in the drive chain:
The torque at the wheels of the TDI : 1100 Nm
The torque at the wheels of the screamer : 1440 Nm

The screamer will drop the TDI because it it generating more power (which the gearbox is converting into more torque) at a higher RPM.

At the end of the day it's the amount of power (kW) that an engine can deliver that makes the difference because the gearbox is essentially just a torque converter.

I have a very little torque na car

 

[blaaislaai]

Just to add,

A car's weight will also depend how fast you will be able to accelerate. Having high torque in a big / heavy car won't always mean it can accelerate fast.

 

[4cer]

ya love the guys with there 1.9tdi polo's they feel faster then they are !

sure they pull off the mark quick but thats it, a High Kw 1.6 will beat them to 100 and most 2l will destroy them.

and best thing is being behind them on the highway, once they hit about 165 they have like no acceleration at all.

but ya anyway a car can have 1000 torques and still be slowish so its the mixture explained above about when torque peak is reached and KW etc.

 

[MR.C]

google this "Audi R8 e-Tron" for a massive torque figure.

 

[alpine]

@Paul_S: Good explanation!

Also another thing that many people don't consider is that shifting makes a huge difference. Take a car that has a red-line of 9000rpm, the guy in the the standard TDi has most likely shifted twice already at the limiter before the 9000rever shifts once. Each time you shift it means precious loss of torque while the shifting is being done (they are working on transmission that have no loss of torque while you shift).

Lastly many Diesel guys claim that they like it because it's faster off the block but it's not generally my observation of things, which is also backed by the relatively slow 0-100 times of Turbo Diesels in comparison with Turbo Petrol or high-revving Petrol N/A.

The reason is once again that the gearbox is a torque converter, guy X has a 9000rpm revver and in 1st he revved to 9000rpm, that car made a hell of a lot of power, in 2nd he made it once again to 9000rpm at which point he is probably at 100km/h or close to it. If you've ever driven a high-revving performance petrol car you'll know that they rev incredibly quickly, it's nothing like a diesel that's slow to rev. You can test it for yourself by putting a diesel in neutral and revving it then compare it to a high-revving petrol. Then also remember the fact that the petrol engine has a close ratio gearbox so it's a no brainer which is faster off the block.

And in case of Turbo Petrol, the newer Turbo Petrol engines generally make maximum torque from around 1500-2000rpm all the way very close to peak power where on the other hand Turbo Diesels make peak Torque low in the range, usually also 1500 - 2000rpm for a inline 4 but after that the torque drops off as the engine approaches peak power.

Because a Turbo Diesel has a rev limit of around 5000rpm their peak power is usually very low in the range (say 4000rpm), and I don't know if I need to mention this but peak power is by definition after peak torque not before. My point? The Turbo Diesel had a huge peak torque early on but it quickly dropped off, the Turbo Petrol had it just as early but torque was less, upside is it kept that torque for almost twice as long as the Turbo Diesel's had long since dropped off.

N/A Petrol generally make their peak torque very high in the range, like 5000-6000rpm but I'd also like to point out that those engines generally make a large amount of torque, once again because at 5000rpm the engine is flowing a very large amount of air. Turbo Diesels have trouble keeping up with them never mind N/A Diesel (which I think it is fair to mention as those Petrol engines don't have Turbos)

So you think its all about revs huh
http://www.autoexpress.co.uk/carreviews/grouptests/226926/mercedes_cclass.html

 

[JK8]

@Paul_S: Good explanation!

Also another thing that many people don't consider is that shifting makes a huge difference. Take a car that has a red-line of 9000rpm, the guy in the the standard TDi has most likely shifted twice already at the limiter before the 9000rever shifts once. Each time you shift it means precious loss of torque while the shifting is being done (they are working on transmission that have no loss of torque while you shift).

Lastly many Diesel guys claim that they like it because it's faster off the block but it's not generally my observation of things, which is also backed by the relatively slow 0-100 times of Turbo Diesels in comparison with Turbo Petrol or high-revving Petrol N/A.

The reason is once again that the gearbox is a torque converter, guy X has a 9000rpm revver and in 1st he revved to 9000rpm, that car made a hell of a lot of power, in 2nd he made it once again to 9000rpm at which point he is probably at 100km/h or close to it. If you've ever driven a high-revving performance petrol car you'll know that they rev incredibly quickly, it's nothing like a diesel that's slow to rev. You can test it for yourself by putting a diesel in neutral and revving it then compare it to a high-revving petrol. Then also remember the fact that the petrol engine has a close ratio gearbox so it's a no brainer which is faster off the block.

And in case of Turbo Petrol, the newer Turbo Petrol engines generally make maximum torque from around 1500-2000rpm all the way very close to peak power where on the other hand Turbo Diesels make peak Torque low in the range, usually also 1500 - 2000rpm for a inline 4 but after that the torque drops off as the engine approaches peak power.

Because a Turbo Diesel has a rev limit of around 5000rpm their peak power is usually very low in the range (say 4000rpm), and I don't know if I need to mention this but peak power is by definition after peak torque not before. My point? The Turbo Diesel had a huge peak torque early on but it quickly dropped off, the Turbo Petrol had it just as early but torque was less, upside is it kept that torque for almost twice as long as the Turbo Diesel's had long since dropped off.

N/A Petrol generally make their peak torque very high in the range, like 5000-6000rpm but I'd also like to point out that those engines generally make a large amount of torque, once again because at 5000rpm the engine is flowing a very large amount of air. Turbo Diesels have trouble keeping up with them never mind N/A Diesel (which I think it is fair to mention as those Petrol engines don't have Turbos)

I like this explanation, relating it to the gears as well.
For example a 132kw MK4 Gti feels so much faster than my car when you drive it, but if you race the 2, the Polo wins, didnt make sense until I realised the 132kw had 6 gears!

You know alot about the inner workings of cars even in another thread about the cluth, you a mech?