Smooth/low rolling - resistance cars

[flatso]

Not sure if this is the proper subforum but my question is about car models where there was a design and engineering effort to make all the chassis internals as low resistance as possible leading to a smooth coasting and rolling result.

[CraigyMc]

flatso said:

Not sure if this is the proper subforum but my question is about car models where there was a design and engineering effort to make all the chassis internals as low resistance as possible leading to a smooth coasting and rolling result.

E90 BMW 3 series EfficientDynamics.

Low rolling resistance tyres, small wheels with large amounts of flat surface (BMW style 306), large sidewalls, low ride-height, soft suspension springs and dampers, soft bushings, avoidance of large toe in or out angles (although it's still a BMW so runs a fair bit of rear camber), long final drive with no mechanical diff, brakes that actively control the float distance of the pad to disc.

The thing coasts and coasts, it catches people out who aren't used to that happening.

[Scrump]

Maybe something like the VW XL1

Why do you ask?

[OverSteery]

CraigyMc said:

E90 BMW 3 series EfficientDynamics.

Low rolling resistance tyres, small wheels with large amounts of flat surface (BMW style 306), large sidewalls, low ride-height, soft suspension springs and dampers, soft bushings, avoidance of large toe in or out angles (although it's still a BMW so runs a fair bit of rear camber), long final drive with no mechanical diff, brakes that actively control the float distance of the pad to disc.

The thing coasts and coasts, it catches people out who aren't used to that happening.

I'm interested in the "no mechanical diff", how did that work and what was the benefit?

[POIDH]

Rolling resistance or/and low friction engine and drivetrain or/and lower drag?

[hidetheelephants]

The Honda Insight Mk1 was optimised for very low drag and rolling resistance and can achieve impressive fuel consumption.

[CraigyMc]

OverSteery said:

CraigyMc said:

E90 BMW 3 series EfficientDynamics.

Low rolling resistance tyres, small wheels with large amounts of flat surface (BMW style 306), large sidewalls, low ride-height, soft suspension springs and dampers, soft bushings, avoidance of large toe in or out angles (although it's still a BMW so runs a fair bit of rear camber), long final drive with no mechanical diff, brakes that actively control the float distance of the pad to disc.

The thing coasts and coasts, it catches people out who aren't used to that happening.

I'm interested in the "no mechanical diff", how did that work and what was the benefit?

Ah. I'm only talking about the lack of a limited slip diff, rather than no diff at all!

[2xChevrons]

One of Vincenzo Lancia's (many) personal insistences was that his cars had as low rolling resistance as possible in the drivetrain - he was almost fanatical about eliminating any binding or drag in the gearbox, axle or wheel bearings since they wasted effort on the part of the engine. The bearings of vintage Lancia's are especially finely-engineered.

As demonstrated in this video of a Belna/Augusta:

https://youtu.be/HTRPtz5Eb2A?si=IX_LtQEDorVqFO04&a...

(start at 06:22 if the timecode doesn't work)

[hersh]

The A40 Farina was way ahead in its day for aerodynamics..

OK, it was in the early '70s

[Truckosaurus]

One of them old SAABs that had a freewheel must be the winner.

(Also, Toyota/Lexus hybrids that are all about coasting along with the engine at idle)

[unsprung]

2xChevrons said:

One of Vincenzo Lancia's (many) personal insistences was that his cars had as low rolling resistance as possible in the drivetrain - he was almost fanatical about eliminating any binding or drag in the gearbox, axle or wheel bearings since they wasted effort on the part of the engine. The bearings of vintage Lancia's are especially finely-engineered.

As demonstrated in this video of a Belna/Augusta:

https://youtu.be/HTRPtz5Eb2A?si=IX_LtQEDorVqFO04&a...

(start at 06:22 if the timecode doesn't work)

Out. Standing.

At the time this devotion to efficiency would have been a notable difference to the engineering of some other marques.

Love the drive thereafter. including shots on the floor with pedals and shifting.

[Sebring440]

hersh said:

The A40 Farina was way ahead in its day for aerodynamics..

OK, it was in the early '70s

I'm not familiar with the early '70s A40 Farina. Have you got a pic?

[donkmeister]

hersh said:

The A40 Farina was way ahead in its day for aerodynamics..

OK, it was in the early '70s

I think OP is after cars engineered for low mechanical drag rather than low aero drag.


Interesting stuff about the BMW. Ford did a super-efficient Focus around the same time (a friend owned one and found it frustrating!). I know it had longer gearing and low rolling resistance tyres to eek out even more MPG from a small diesel engine but no idea if they went any further than that.

Wrt SAAB and the freewheels, that was simply a measure to avoid knackered 2-strokes starved of lubrication on long downhills. However... Roverdrive. That was a freewheel intended to save fuel. Available on the P4.

If we're going to stretch to cars with just low rolling resistance tyres, notable mention for the Toyota GR86 with the Prius tyres.

[GeniusOfLove]

I imagine everything these days, when you're adding things like motorised radiator slats to reduce drag it's fair to say you've already taken all the low hanging fruit like mechanical drag.

[RicksAlfas]

CraigyMc said:

E90 BMW 3 series EfficientDynamics.

Low rolling resistance tyres, small wheels with large amounts of flat surface (BMW style 306), large sidewalls, low ride-height, soft suspension springs and dampers, soft bushings, avoidance of large toe in or out angles (although it's still a BMW so runs a fair bit of rear camber), long final drive with no mechanical diff, brakes that actively control the float distance of the pad to disc.

The thing coasts and coasts, it catches people out who aren't used to that happening.

I had one of these. The other thing about the small wheels/suspension was it could flow down a bumpy back road really well. A pal had a 330i at the time with the usual M-Sport setup and the difference in composure down the same road was night and day. He was quite miffed!

[hersh]

Sebring440 said:

hersh said:

The A40 Farina was way ahead in its day for aerodynamics..

OK, it was in the early '70s

I'm not familiar with the early '70s A40 Farina. Have you got a pic?

[CKY]

hersh said:

Sebring440 said:

hersh said:

The A40 Farina was way ahead in its day for aerodynamics..

OK, it was in the early '70s

I'm not familiar with the early '70s A40 Farina. Have you got a pic?

Didn't they come out in 1958?

[Truckosaurus]

donkmeister said:

...SAAB and the freewheels, that was simply a measure to avoid knackered 2-strokes starved of lubrication on long downhills....

Good knowledge. I was trying to recall what the reason was but was drawing a blank.

[legless]

RicksAlfas said:

I had one of these. The other thing about the small wheels/suspension was it could flow down a bumpy back road really well. A pal had a 330i at the time with the usual M-Sport setup and the difference in composure down the same road was night and day. He was quite miffed!

When I used to work in vehicle development, it was amusing to see that an SE-spec BMW or Audi could consistently set better laptimes than the equivalent M-sport/S-line model around our 'public road' circuit (a circuit specifically designed to be as similar to UK A- and B-roads as possible in terms of surface/features)

But Joe Public thinks stiff springs = good handling, so there you go.

[Jordie Barretts sock]

hersh said:

Sebring440 said:

hersh said:

The A40 Farina was way ahead in its day for aerodynamics..

OK, it was in the early '70s

I'm not familiar with the early '70s A40 Farina. Have you got a pic?

70s? Do you mean the Austin/Morris/VdP 1100/1300?