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Master_Scythe

Member Since 10 Sep 2008
Offline Last Active Mar 22 2017 06:21 PM
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Posts I've Made

In Topic: What car do you drive?

21 March 2017 - 12:48 PM

 why arent friction and slippage ever-present problems?

 

They are. That's what we've been discussing.


In Topic: What car do you drive?

21 March 2017 - 12:19 PM

 

CVT is mostly unheard of outside small vehicles, and for good reason.

 

The idea behind it of course is great but I've got doubts there'll ever be a decent implementation.

Given that autos with mad amounts of ratios are becoming common, there seems not much reason to pursue improvements.

 

Stupidly Subaru have gone with a CVT even on the 3.6R Outback whereas previously it was only on the 2.5.

 

A decent 8 speed would have been a much better choice.

 

 

I "drove" a Levorg around a.... "privately owned mountain course"..... with the CVT in aggressive mode.

That turbo really makes a CVT shine!

I was actually impressed. But it was also near brand new....

 

Just because they feel great now, they'll need another 5+ years to prove they're reliable before we trust 'their design'.


In Topic: What car do you drive?

21 March 2017 - 09:11 AM


The main limitation of the CVT is the belt, the stronger the belt, the more torque you can transmit. As time goes on, I don't doubt they can improve the belts.

Ideally, given a properly engineered belt and software, the CVT would be the perfect transmission. But there are still engineering hurdles to jump.

 

138 years they've been trying.

Ever since saw mills first started using them, and quickly went back to fixed speed belts.

1920's-ish was the first decent car attempt (there had been some before that).

 

And 1970-something was the modern wet band style implimentation IIRC....

I suppose it's only been 47 years they've been trying with the modern design.

Maybe they'll perfect it just in time for hub driven electric motors to take over?


In Topic: What car do you drive?

21 March 2017 - 08:44 AM

 

The idea behind it of course is great but I've got doubts there'll ever be a decent implementation.


Since the idea behind CVT is to keep the engine at max torque regardless of output shaft velocity (ie: vehicle speed), yes that's brilliant. Which makes me wonder what in hell MS was on about back there.

 

 

But it doesn't for two reasons.

 

1. technically, most are tuned for max EFFICIENCY, which while in theory is where max torque is, if you lead-foot the gas in an emergency situation, it'll still rise above the, say, 3000rpm.

2. There is always a climb from no torque, to max torque every acceleration. (from 600rpm idle to 3000rpm), so this is where you feel shudder.

 

Bonus 3. They give drivers flappy paddles to 'limit' the gearbox manually if wanted (bad idea).

 

Lets not even look at the problems with running an engine at near the exact same RPM for its entire life. No visits to redline at all must mean hella amounts of carbon.


In Topic: What car do you drive?

20 March 2017 - 06:47 PM

how is it experienced? in the case of the stretched belt, is it like a sluggishness that is felt constantly, or briefly whenever there is rapid acceleration, or what?

 

Shudder is the best description.

Usually in instances of high torque. So taking off from lights or low speed up hills.

Most commonly, it feels like a really minor "Lugging" of the engine; that jolty feeling you get when an inexpereinced manual driver doesn't quite give enough gas, but also doesn't stall it.

 

If its particularly worn I'd imagine you could feel it like a constant sluggishness. It'd be turning engine power into heat.