cars struggling up hills

Team Banana Spokesman

I got an old ford puma for cheap and got my mate to boost the power a bit.

we did a test in his garage and i worked out that the power to weight ratio is 94.7 w/kg

a good climber will have 4-6 w/kg or more with drugs. think i'm around 2.8

BUT

when out on the bike I can go up 20% hills and cars much better than my puma struggle and make horrible noises. a merc stalled on a 15% today.

???

Ben6899

It's to do with gear ratios and engine revolutions... 15% is one heck of a hill so I guess the merc may have been in 2nd gear at very low revs. If those revs drop too near to idle, then the car will stall.

EDIT: a cyclist stalls at 0rpm, whereas 4 stroke combustion engine is much less tolerant and will stall at ~750-1100rpm.

Team Banana Spokesman

ah.

you mean the lowest gears are not low enough? if contador had only a 53 x 11 on a hill he would stall yes?

can you tweak cars to give them 'granny gears''??

Steve_b77

You can but it'll probably cost more than a cheap puma is worth.

New gear box or ooodles more power/torque is the only way to cope with big hills.

See Pikes Peak race cars for how to get up a hill quickly.

bompington

As previous poster said, car engines stall at much higher revs than bikes (I'm sure most of us at some time have started pedalling from negative revs, i.e. going backwards) and the power/torque of any internal combustion engine at stalling speed is very low, that's what stalling means, it's when the torque is insufficient to overcome resistance.
So any car stalling is down to driver error.
Modern cars can climb hills with great ease, I drove up to Glenshee the other day, the last bit is about 200m climb in 2km, my car (Skoda, 2 litre diesel) was quite comfortable in 6th gear

Heckler1974

bompington wrote:

the other day, the last bit is about 200m climb in 2km, my car (Skoda, 2 litre diesel) was quite comfortable in 6th gear

You don't say how comfortable the people pushing your car were though :P

bompington

Heckler1974 wrote:

bompington wrote:

the other day, the last bit is about 200m climb in 2km, my car (Skoda, 2 litre diesel) was quite comfortable in 6th gear

You don't say how comfortable the people pushing your car were though :P

Ahh, all the old Skoda jokes! I can tell you who's laughing now, whenever I see an Audi Quattro (see Clarkson's verdict) and I smugly think about how I'm driving more or less the same car at half the price

northernneil

i hear what you are saying ... but ...

.. I am guessing you ride a carrera ?

bompington

northernneil wrote:

i hear what you are saying ... but ...

.. I am guessing you ride a carrera ?

No, Raleigh actually, and most of my cycle clothing comes from Aldi and Lidl.

rake

maybe the cheap ford pooma not in good hea;lth.

nwallace

It's on hills where I notice the quality of petrol.
Difference between Shell and Tesco is needing to shift down to overtake on the Drumochter dual carriageway.going North when using Tesco.