Engine braking

[Cock Womble 7]

How come the engine braking on "Katie" is so, well, brutal? Lift off the throttle and I seem to hit an invisible wall.

Is it the lightened flywheel, or just the fact that it's a very light car?

I swear that the engine braking on the Caterham is better than the actual braking on my old Scirocco (notoriously bad brakes).

[Mars]

Fairly high compression, lightweight and light flywheel will all work together on the overrun. Makes you conscious of the potential for spinning in the wet.

[snapper seven]

Not to mention the 'air-brake' effect a full screen has. Plays a big role in (negatively) affecting areodynamics - hence why the likes of the old Merc 300SLR had such a big air brake, the Bugatti Veyron/McLaren F1 etc all have deployable vertical wings.

I fitted brooklands aero screens to my car a while back and really noticed the difference in acceleration and throttle pick up at higher speeds because it could push through the air more easily.

Cheers
SS

[Cock Womble 7]

snapper seven said:

Not to mention the 'air-brake' effect a full screen has. Plays a big role in (negatively) affecting areodynamics

Hadn't thought of that!

[maturin23]

I read somewhere recently that the CD of the Caterham is around .9

Coming off the throttle at 70 does feel rather like deploying an airbrake..

[ewenm]

Cock Womble 7 said:

snapper seven said:

Not to mention the 'air-brake' effect a full screen has. Plays a big role in (negatively) affecting areodynamics

Hadn't thought of that!

Try it with an aeroscreen - makes a huge difference to the retardation

[Cock Womble 7]

maturin23 said:

I read somewhere recently that the CD of the Caterham is around .9

The always reliable Wikipedia suggests that the Caterham is 0.7 - worse than a Hummer H2!

[ewenm]

Cock Womble 7 said:

maturin23 said:

I read somewhere recently that the CD of the Caterham is around .9

The always reliable Wikipedia suggests that the Caterham is 0.7 - worse than a Hummer H2!

Although it is CdA that is more relevant - Cd x frontal area of the car.

[Noger]

Yes, the CdA is about the same as an Elise. Less if you ditch the screen.

I would imagine low mass would be they key, coupled with fairly high (numerical) gear ratios which increases the engine braking torque.

[edb49]

Also compared to lots of modern cars, the Caterham will stop fuelling when you come off the throttle - modern cars keep fuelling a little bit to aid smoother driving.

[fergus]

edb49 said:

Also compared to lots of modern cars, the Caterham will stop fuelling when you come off the throttle - modern cars keep fuelling a little bit to aid smoother driving.

? most modern maps will have accel and decel clamp tables in them. I'm not sure if the stock caterham map/ECU does this, but most decent aftermarket ECUs offer these adjustments.

[Murph7355]

Mars said:

...Makes you conscious of the potential for spinning in the wet.

Makes you doubly careful to match road with engine speeds

Though a bit of "rear steer" can be handy at times.