Is torque really relevant?

[Welshbeef]

Fastdruid said:

Welshbeef said:

Fastdruid said:

The TDCI140 and the 2.5T make the same torque no? So exactly the same kind of comparison.

You've picked equal _power_ because it suits you. So why not pick equal torque instead and see where that gets you?

No I didn’t “pick it” it’s simply one car we have and the other car is friends of ours and we happened To be driving in convoy - interesting given the same power output.

Not sure I’ve ever considered cloning up cars with the same max torque in which case you might see a bus against a Veyron.

You picked it to compare though.

If your friend had one that left you for dead would you have brought it up?

Ok can we now all (oddly) start to compare cars which have similar peak torque and ignore max power due to Fastdruids view of things.

[Ron99]

Fastdruid said:

Welshbeef said:

Fastdruid said:

Apples with oranges try against someone in an SMax 2.5T and see how well you can keep up.

So you shouldn’t compare the exact same car with the exact same max power but one is turbo petrol the other is turbo diesel

You like to compare a 240bhp petrol Smax vs a 140bhp diesel?
Why not compare the top of the range diesel against the petrol so that’s 220bhp v 240bhp, naturally the 240bhp should win (don’t know if it does or doesn’t)

The TDCI140 and the 2.5T make the same torque no? So exactly the same kind of comparison.

You've picked equal _power_ because it suits you. So why not pick equal torque instead and see where that gets you?

Taking a mainstream, unremarkable manufacturer as an example.....

When the Vauxhall Insignia launched around 12 years ago, excluding the VXR version, the top diesel was 2L with 350Nm and the top petrol was 2L with 350Nm. Both same capacity and same torque.
The diesel's torque peaked 1750-2500rpm while the petrol's torque peaked 2000-4000rpm.
The diesel topped-out at 160hp at 4000rpm while the petrol topped-out at 220hp at 5300rpm, and at 4000rpm where the diesel made its peak power of 160hp, the petrol had around 195hp.

For the mid-life 'facelift', the diesel went up to 400Nm and 170hp while the petrol also went up to 400Nm with 250hp.

So a turbo-petrol seems perfectly capable of being manufactured to give approximately the same torque as a turbo-diesel.

Edited by Ron99 on Wednesday 8th July 19:07

[Fastdruid]

fido said:

Turbo petrols are a better match for diesels but they still lack grunt / throttle response at the low-end due to a lower compression ratio and less efficient combustion that diesels. Electrically-assisted hybrid turbos that fill in at low revs and new combustion technologies (Mazda SPCCI and Ferrrari/Maserati's pre-combustion tech) will make diesels even less attractive.

They don't though. They have better grunt and better "throttle response" at low end because off-boost diesels are dire and massively laggy. Far more so than petrols. Once the diesel gets "on boost" though there is no throttle which means you don't need to get rid of boost when you close it and there is no hanging around waiting for boost to build and so they respond with power quicker to the throttle than an FI petrol as all they do is inject fuel. That is a definite advantage to turbo diesels. It is also a part of why they are more economic, having to work against that closed or partly open throttle costs the petrol engine energy. It is the idea behind the Fiat TwinAir engine where they reckon it costs 10% of the input energy...

Although when people say "throttle response" that's not really what they mean... They mean how long it takes for the power to arrive. You can have a petrol car with instant throttle _response_ yet laggy as hell as it takes ages for the power to come in.

[Equus]

ddom said:

It’s not incorrect at all

you said:

If you had driven smaller engined modern diesel cars you’d be better placed to understand torque, and this topic.

Your assumption was that I had not driven smaller engined modern diesel cars.

You were entirely incorrect.

[Equus]

Ron99 said:

So a turbo-petrol seems perfectly capable of being manufactured to give approximately the same peak torque as a turbo-diesel.

EFA

There are a lot of people on this thread thinking in two dimensions, when they need to think in three.

As I've repeatedly stated, it's the area under the torque curve that's important: ie. the spread, not just the peak.

[RobM77]

Fastdruid said:

fido said:

Turbo petrols are a better match for diesels but they still lack grunt / throttle response at the low-end due to a lower compression ratio and less efficient combustion that diesels. Electrically-assisted hybrid turbos that fill in at low revs and new combustion technologies (Mazda SPCCI and Ferrrari/Maserati's pre-combustion tech) will make diesels even less attractive.

They don't though. They have better grunt and better "throttle response" at low end because off-boost diesels are dire and massively laggy. Far more so than petrols. Once the diesel gets "on boost" though there is no throttle which means you don't need to get rid of boost when you close it and there is no hanging around waiting for boost to build and so they respond with power quicker to the throttle than an FI petrol as all they do is inject fuel. That is a definite advantage to turbo diesels. It is also a part of why they are more economic, having to work against that closed or partly open throttle costs the petrol engine energy. It is the idea behind the Fiat TwinAir engine where they reckon it costs 10% of the input energy...

Although when people say "throttle response" that's not really what they mean... They mean how long it takes for the power to arrive. You can have a petrol car with instant throttle _response_ yet laggy as hell as it takes ages for the power to come in.

There are two types of throttle response:

1) Top of the pedal lag. Petrols lose this one instantly; they’re utterly appalling.

2) Turbo lag. I’m on my third BMW diesel and yes, I’m certain situations the lag is horrendous. However, you don’t normally experience the lag as it only happens if you’ve been off the power for ages. If you’re doing something interesting, like cornering on a B road with the revs up or driving quickly, there’s no turbo lag at all.

[ddom]

Equus said:

Your assumption was that I had not driven smaller engined modern diesel cars.

You were entirely incorrect.

Yeah ok genius, like I said i've no need to compromise and personally buy something boring, for a daily or otherwise.

But keep digging.

[ddom]

RobM77 said:

There are two types of throttle response:

1) Top of the pedal lag. Petrols lose this one instantly; they’re utterly appalling.

2) Turbo lag. I’m on my third BMW diesel and yes, I’m certain situations the lag is horrendous. However, you don’t normally experience the lag as it only happens if you’ve been off the power for ages. If you’re doing something interesting, like cornering on a B road with the revs up or driving quickly, there’s no turbo lag at all.

What about the strange floaty over-run on modern petrol cars, is that due to fueling or basic mechanical design?

[Equus]

ddom said:

like I said i've no need to compromise and personally buy something boring, for a daily or otherwise.

Yeah, so you keep telling us - what was it? Your car ownership is 'too important' to share?

[ddom]

Equus said:

Yeah, so you keep telling us - what was it? Your car ownership is 'too important' to share?

Not 'us', you. Get used to the idea, it'll be easier that way.

Now, if you want to talk about engine characteristics I am all ears. Care to debate why the average FI diesel car has a power curve like a turtle shell?

[Equus]

ddom said:

Care to debate why the average FI diesel car has a power curve like a turtle shell?

Not with some fantasist with the same level of credibility as your average 11-year old, no thanks.

You've already demonstrated that you can't even grasp the concept of how a gearbox works. Why would I even bother wasting my time?

[RobM77]

ddom said:

RobM77 said:

There are two types of throttle response:

1) Top of the pedal lag. Petrols lose this one instantly; they’re utterly appalling.

2) Turbo lag. I’m on my third BMW diesel and yes, I’m certain situations the lag is horrendous. However, you don’t normally experience the lag as it only happens if you’ve been off the power for ages. If you’re doing something interesting, like cornering on a B road with the revs up or driving quickly, there’s no turbo lag at all.

What about the strange floaty over-run on modern petrol cars, is that due to fueling or basic mechanical design?

Horrible isn’t it? They don’t all do that though. It’s programmed in so people who are very slow at changing gear don’t get lurching upshifts. Vauxhalls do it, as do Fords and Peugeots. Plenty don’t though.

[ddom]

Equus said:

Not with some fantasist with the same level of credibility as your average 11-year old, no thanks.

You've already demonstrated that you can't even grasp the concept of how a gearbox works. Why would I even bother wasting my time?

Great, I'll add you to the list to ignore

[Equus]

ddom said:

Great, I'll add you to the list to ignore

Glad you recognised that the description applied to you.

[ddom]

Equus said:

Glad you recognised that the description applied to you.

It's ok, life must be awful driving such dull things. However, I am sure your amazing home build will change the landscape

[Equus]

ddom said:

life must be awful driving such dull things.

ddom said:

Equus said:

Are you going to tell us what you're basing your experience on, or is it still a state secret?

In this instance dozens of hire cars. All modern diesels.

[Fastdruid]

RobM77 said:

ddom said:

RobM77 said:

There are two types of throttle response:

1) Top of the pedal lag. Petrols lose this one instantly; they’re utterly appalling.

2) Turbo lag. I’m on my third BMW diesel and yes, I’m certain situations the lag is horrendous. However, you don’t normally experience the lag as it only happens if you’ve been off the power for ages. If you’re doing something interesting, like cornering on a B road with the revs up or driving quickly, there’s no turbo lag at all.

What about the strange floaty over-run on modern petrol cars, is that due to fueling or basic mechanical design?

Horrible isn’t it? They don’t all do that though. It’s programmed in so people who are very slow at changing gear don’t get lurching upshifts. Vauxhalls do it, as do Fords and Peugeots. Plenty don’t though.

No it's not that. It is emissions.

Basically chopping the throttle shut is horrific for emissions.

https://www.carthrottle.com/post/rev-hang-explaine...

[ddom]

Fastdruid said:

No it's not that. It is emissions.

Basically chopping the throttle shut is horrific for emissions.

https://www.carthrottle.com/post/rev-hang-explaine...

So it's actually helping emissions, shame as it makes them really annoying to drive

[RobM77]

Fastdruid said:

RobM77 said:

ddom said:

RobM77 said:

There are two types of throttle response:

1) Top of the pedal lag. Petrols lose this one instantly; they’re utterly appalling.

2) Turbo lag. I’m on my third BMW diesel and yes, I’m certain situations the lag is horrendous. However, you don’t normally experience the lag as it only happens if you’ve been off the power for ages. If you’re doing something interesting, like cornering on a B road with the revs up or driving quickly, there’s no turbo lag at all.

What about the strange floaty over-run on modern petrol cars, is that due to fueling or basic mechanical design?

Horrible isn’t it? They don’t all do that though. It’s programmed in so people who are very slow at changing gear don’t get lurching upshifts. Vauxhalls do it, as do Fords and Peugeots. Plenty don’t though.

No it's not that. It is emissions.

Basically chopping the throttle shut is horrific for emissions.

https://www.carthrottle.com/post/rev-hang-explaine...

Thanks. I’ve always hated this, but just assumed it was just how numpties liked their cars to drive!

[Welshbeef]

ddom said:

So it's actually helping emissions, shame as it makes them really annoying to drive

In all my years I’ve owned a lot of cars driven plenty of hire cars on holiday and rental vans when moving and on the odd occasion driven friends & family members cars. They are all sorts of cars power trains weight output but I didn’t find any annoying go drive. They are all simply a tool to get from A to B in safety.

There are many of those cars I’ve driven I personally wouldn’t buy but that said I want specific things from a vehicle - if it’s the family wagon safety space kit, for me fast road car plenty of ability to prod and go plus needs to be an auto given the commute (I had pre covid).

What do you currently drive?