Automatic cars

from_atozinc

Which of these cars would an automatic transmission be best suited too :

1 ) A 2 litre turbo DIESEL car that's 160 BHP

2 ) A 2 litre turbo PETROL car that's 160 BHP.

_Kaiser_

from_atozinc wrote: »

Which of these cars would an automatic transmission be best suited too :

1 ) A 2 litre turbo DIESEL car that's 160 BHP

2 ) A 2 litre turbo PETROL car that's 160 BHP.

I'd imagine it'll completely vary depending on the car and type of auto gearbox in it (multitronic/tiptronic)

Stinicker

Diesel has more torgue and would be better suited

Matt Simis

Stinicker wrote: »

Diesel has more torgue and would be better suited

What complementary phrasing you use!


The Diesel likely has less axle torque, much shorter usable rev band near peak torque therefore requires more shifting making it more suited to the Automatic.
Diesels do well with Automatics, the more gears the better (ie 7 and 8), as they allow the engine to provide consistent power throughout a given accelerative duration (until the number of gears run out). A manual would be a chore and require too many gears to churn by the driver.

In my experience it's overall power that makes the difference.

A small petrol or diesel engine will most likely mean you have to drive the car harder than the engine with more power, so the auto box will drop gears much earlier and possibly 2-3 gears when you put your foot down because it thinks you wan't to go faster or harder than you actually do.

That's in automatic mode.

The dsg/stronic in vw/audi/seat/skoda and the multitronics in the Audi have a tiptronic mode and will allow you to solve the above by changing to manual, or semi auto.

Senecio

Either will be perfectly fine provided the manufacturer has done a good job of calibrating the auto gearbox to the engine. Most modern cars with 5 or more ratios are usually fine.

Anyone remember the old 3 speed autos with overdrive?

I think actually the more torque the engine has the better simply because the box won't be swapping gears all the time, though that would apply to lower HP engines I think.

At 160+ hp, I don't think it matters as much.

ffocused

Senecio wrote: »

Anyone remember the old 3 speed autos with overdrive?

Ahh memories!
My very first car had one, a 1L monster that was flat out at 75mph.
1987 Nissan Micra in a lovely beige colour.

unkel

Senecio wrote: »

Anyone remember the old 3 speed autos with overdrive?

Some Japanese and other backwards car manufacturers still made those into the 90s

Honda automatics only had 2 speeds in the 70s, called hondamatic, LOL!

Not sure why Japanese manufacturers insist on using ancient automatic transmission technology even now...

My own car is 10 years old this month but it uses a relatively modern intelligent 6 speed ZF (German) automatic steptronic gearbox. It works very well.

colm_mcm

Examples?

Popoutman

Matt Simis wrote: »

The Diesel likely has less axle torque, much shorter usable rev band near peak torque therefore requires more shifting making it more suited to the Automatic.
Diesels do well with Automatics, the more gears the better (ie 7 and 8), as they allow the engine to provide consistent power throughout a given accelerative duration (until the number of gears run out). A manual would be a chore and require too many gears to churn by the driver.

Incorrect regarding the torque outputs. The resulting axle torque will likely be the same at the road-tire interface, if the cars have the same peak power and the same top speed, all other things being equal.

The diesel will likely have 50% or more engine torque than the petrol, as it can't rev as high as the petrol likely would. After all, Power = torque x speed.
The petrol generally would have a fairly flat torque curve, with a power curve peaking near peak engine speed. The diesel would have a hill-shaped torque curve, with a flatter power curve, peaking slightly just below the max engine speed. The diesel will have more area under the torque curve than the petrol at all stages, suggesting that there is a lot more "flexibility" to that engine for use by an automatic gearbox. For most driving conditions off full throttle, the diesel will need to shift less, and will generally give a more comfortable ride given the sounds heard inside are (generally) lower at the same engine speed as the petrols.

In short, with a well-designed gearbox with intelligent programming, the diesel is a better suit to the automatic gearbox.

Popoutman

Popoutman wrote: »

The diesel will have more area under the torque curve than the petrol at all stages, suggesting that there is a lot more "flexibility" to that engine for use by an automatic gearbox. For most driving conditions off full throttle, the diesel will need to shift less, and will generally give a more comfortable ride given the sounds heard inside are (generally) lower at the same engine speed as the petrols.

In short, with a well-designed gearbox with intelligent programming, the diesel is a better suit to the automatic gearbox.

I would agree with the above but only with low power engines, if the car has enough power then it will need to shift less or in the case of the twin clutches "hunt" for gears. Or in the case of the Multitronics the revs wouldn't need to be as high and the torque converter auto's wouldn't change down 2 gears at the slightest touch of the accelerator.

So the torque of a 75-100 hp diesel would be better than the much less torque of a 75-100 hp petrol. Because we tend not to drive the bejesus out of the car all the time torque at lower speeds is what matters most.

But at 150 hp as the op mentioned I don't think it would matter much because both cars will have enough overall power to keep the auto box happy and move the cars with less revs or less pressure on the throttle so the auto box ecu will not think you want to drop gears as much.

Jesus.

Are there many new N/A petrol cars these days or are they all turbo/supercharged lads?

jimgoose

I have long been of the view that automatic transmissions, and the more gears the better, are the way forward with diesels, and never more so than now when power/torque bands are getting ever narrower and appearing in quare places in the rev-range.

unkel wrote: »

Some Japanese and other backwards car manufacturers still made those into the 90s

Honda automatics only had 2 speeds in the 70s, called hondamatic, LOL!..l.

Sounds rather like the old Buick Dynaflow from around 1960. Those had only two gears per sé, and a 2.1:1 ratio in the fluid coupling, making it a true "torque converter" and explaining why they tended to crap themselves as the whale-oil or whatever passed for ATF that time struggled under the unbelievable abuse!

P.S. Interestingly enough, those strange old Yank 'boxes tend to live long and prosper with a fill of good-quality synthetic ATF every year or so.

jimgoose

Jesus. wrote: »

Are there many new N/A petrol cars these days or are they all turbo/supercharged lads?

AFAIK they're nearly all N/A, save for these new Ford Ecoboost thingies?

Max Power1

jimgoose wrote: »

AFAIK they're nearly all N/A, save for these new Ford Ecoboost thingies?

Id say mostly correct, apart from the ford and vag turbos, the vast majority of petrols are still NA.

Lets see how long that lasts!

Zubeneschamali

Jesus. wrote: »

Are there many new N/A petrol cars these days or are they all turbo/supercharged lads?

Turbos are increasingly popular - Ford has Ecoboost 1.0 from to 2.0 motors. Fiat has 1.0 and 1.4 Multair, VW now uses a 1.2 and 1.4 turbo in Golf and Passat, BMW is using turbos even in M cars now.

Mini Cooper S is no longer supercharged, and I think the MB Kompressor is gone. Only Jaguar still using superchargers?

Matt Simis

Popoutman wrote: »

Incorrect regarding the torque outputs. The resulting axle torque will likely be the same at the road-tire interface, if the cars have the same peak power and the same top speed, all other things being equal.

I have a Excel chart with the torque, gearing and Final drive that says otherwise, based on the Swedish national testing groups dyno tests.

Popoutman wrote: »

The diesel will likely have 50% or more engine torque than the petrol, as it can't rev as high as the petrol likely would. After all, Power = torque x speed.

A diesel engine having "50% more torque" is not due to the fact it cannot rev as high. Im not sure the point you are trying to make. Also a Turbo petrol will not have 50% less torque than a TDI.

Popoutman wrote: »

For most driving conditions off full throttle, the diesel will need to shift less, and will generally give a more comfortable ride given the sounds heard inside are (generally) lower at the same engine speed as the petrols.

In my experience of performance petrols and diesels, this is completely incorrect. Logically of course its incorrect as all ICE need to be in their peak Rev range to make good power, diesels Rev range is tiny, has to be shifted more

Jesus.

jimgoose wrote: »

AFAIK they're nearly all N/A, save for these new Ford Ecoboost thingies?

Don't the likes of VW's TSI's have turbos on 'em?

Forgive the ignorance lads, but what's the reason all modern diesels are turbo'd up but petrol's aren't?

Max Power1

Jesus. wrote: »

Don't the likes of VW's TSI's have turbos on 'em?

Forgive the ignorance lads, but what's the reason all modern diesels are turbo'd up but petrol's aren't?

Power to weight ratio, emissions and fuel consumption I would guess.

When "they" figured out that petrols could be turbod, this is the reason for their adoption. Like being able to have a 1.0T focus, whereas previously a 1.4 n/a petrol was underpowered.

I don't really remember any n/a diesels aside from the vag SDI lump, which I figured was a legacy hangover from an age gone by.

jimgoose

Jesus. wrote: »

Don't the likes of VW's TSI's have turbos on 'em?

Forgive the ignorance lads, but what's the reason all modern diesels are turbo'd up but petrol's aren't?

Smaller speed-range than the equivalent petrol, thus alleviating turbo-lag a bit. Detonation or "pinking" isn't a problem on diesels either, because of the way the injection is timed, so they can run big compression under boost and reap the associated efficiency and torque gains.

jimgoose

Max Power1 wrote: »

Power to weight ratio, emissions and fuel consumption I would guess.

When "they" figured out that petrols could be turbod, this is the reason for their adoption. Like being able to have a 1.0T focus, whereas previously a 1.4 n/a petrol was underpowered.

I don't really remember any n/a diesels aside from the vag SDI lump, which I figured was a legacy hangover from an age gone by.

Superchargers were more du jour on petrol engines, until everyone caught The Ghey!

Jesus.

jimgoose wrote: »

Smaller speed-range than the equivalent petrol, thus alleviating turbo-lag a bit. Detonation or "pinking" isn't a problem on diesels either, because of the way the injection is timed, so they can run big compression under boost and reap the associated efficiency and torque gains.

What about the TSI? Ain't that turbocharged?

jimgoose

Jesus. wrote: »

What about the TSI? Ain't that turbocharged?

'Tis - TSI is "Turbocharged Stratified Injection". The VAG TSI unit is an example of "Twincharging", using both a supercharger and a turbo. The idea is that one cancels out the weaknesses of the other.

colm_mcm

Of course you have TSI with supercharger (as in most of them)

Jesus.

jimgoose wrote: »

'Tis - TSI is "Turbocharged Stratified Injection". The VAG TSI unit is an example of "Twincharging", using both a supercharger and a turbo. The idea is that one cancels out the weaknesses of the other.

colm_mcm wrote: »

Of course you have TSI with supercharger (as in most of them)

So there are are turbocharged petrol's sold then?

Sorry gents but I'm a tad confused

colm_mcm

Yes they are available, but most people will go diesel. Rented a polo TSI a few months ago and it was very good on petrol.

Turbod petrols in regular cars are still relatively rare.

Nissan do a supercharged micra that nobody buys and a 1.6 turbo juke