TD5 top speed challenge

TalkTorque · Jan 16, 2019

Every time I find the Disco struggling into a strong wind, I keep thinking about this...

Let’s say the TD5’s top speed is 100 mph.

What’s its top speed from a standing start into a 100 mph wind?

Or look at it from another angle. You're zipping along in your TD5 at top speed, 100 mph. Suddenly, you hit a 100 mph headwind. You try to maintain the highest speed possible. What is it?

Beats me. Might be easier to move somewhere with 100 mph winds and try it for real.

TT

sierrafery · Jan 16, 2019

This can vary from one vehicle to another depending on weight, engine power(cos you'll not find two Td5s to run the same) and other elements which can affect aerodynamics for example roof rack, liftings, etc ... though i doubt that you'll be in the mood to drive around when there is 100mph wind cos that's equivalent of a cathegory 2 hurricane so you'll have other worries then https://www.nhc.noaa.gov/aboutsshws.php

JUKE179r · Jan 16, 2019

I'll race you in my V8!

Shimsteriom · Jan 16, 2019

JUKE179r said:
I'll race you in my V8!

You'll have to keep stopping a petrol stations!

JUKE179r · Jan 16, 2019

Shimsteriom said:
You'll have to keep stopping a petrol stations!

touché... lol

raywin · Jan 16, 2019

TalkTorque said:
Every time I find the Disco struggling into a strong wind, I keep thinking about this...

Let’s say the TD5’s top speed is 100 mph.

What’s its top speed from a standing start into a 100 mph wind?

Or look at it from another angle. You're zipping along in your TD5 at top speed, 100 mph. Suddenly, you hit a 100 mph headwind. You try to maintain the highest speed possible. What is it?

Beats me. Might be easier to move somewhere with 100 mph winds and try it for real.

TT

You know I keep wondering if you were traveling at the speed of light and you switched on the headlamps would anything happen?

Shimsteriom · Jan 16, 2019

It would get light.

JUKE179r · Jan 16, 2019

raywin said:
You know I keep wondering if you were traveling at the speed of light and you switched on the headlamps would anything happen?

You'd leak more oil...

MJI · Jan 16, 2019

JUKE179r said:
I'll race you in my V8!

Don't worry most of us have remaps.

Driven a V8 D1 and my D2 TD5 is quicker.

MJI · Jan 16, 2019

TalkTorque said:
Every time I find the Disco struggling into a strong wind, I keep thinking about this...

Let’s say the TD5’s top speed is 100 mph.

What’s its top speed from a standing start into a 100 mph wind?

Or look at it from another angle. You're zipping along in your TD5 at top speed, 100 mph. Suddenly, you hit a 100 mph headwind. You try to maintain the highest speed possible. What is it?

Beats me. Might be easier to move somewhere with 100 mph winds and try it for real.

TT

Probably around 60 to 70 as would be in a lower gear so more force to push it forwards.

joojar · Jan 16, 2019

Reasonable to assume:

physics of this problem will be vastly dominated by turbulent aerodynamics -> resisting force based on square of "air speed"
we're aiming for same total power output in both situations
work rate is resisting force times "ground speed"

So if x is the answer you're looking for (in mph), solve this cubic:

x * (100+x)^2 = 100^3

joojar · Jan 16, 2019

I make it 47mph, or thereabouts

MJI · Jan 16, 2019

joojar said:
Reasonable to assume:

physics of this problem will be vastly dominated by turbulent aerodynamics -> resisting force based on square of "air speed"

we're aiming for same total power output in both situations

work rate is resisting force times "ground speed"

So if x is the answer you're looking for (in mph), solve this cubic:

x * (100+x)^2 = 100^3

mid 40s then

MJI · Jan 16, 2019

joojar said:
I make it 47mph, or thereabouts

You brute forced that didn't you?

joojar · Jan 16, 2019

MJI said:
You brute forced that didn't you?

Done this in me head whilst driving -
40mph ->78.4% of 100^3
50mph -> 112.5% of 100^3
Answer must be about 2/3 between the two unless we're in an "unlucky" part of the cubic. That's all I done, honest!

MJI · Jan 16, 2019

joojar said:
Done this in me head whilst driving -
40mph ->78.4% of 100^3
50mph -> 112.5% of 100^3
Answer must be about 2/3 between the two unless we're in an "unlucky" part of the cubic. That's all I done, honest!

So you did then?

I will admit I did as well

joojar · Jan 16, 2019

MJI said:
So you did then?

I will admit I did as well

Well if it comes to court, I'm going to claim it was one iteration of linear interpolation, and no bugger will get me tosay any different

Feathers McGraw · Jan 16, 2019

joojar said:
I make it 47mph, or thereabouts

That's a pain. I hate it when circumstances made it impossible to lock up the torque convertor.

MJI · Jan 16, 2019

Feathers McGraw said:
That's a pain. I hate it when circumstances made it impossible to lock up the torque convertor.

It would in 3rd

Feathers McGraw · Jan 17, 2019

MJI said:
It would in 3rd

True. But when I'm just short of that magic 52ish mph I start swearing under my breath at the dawdling car in front.

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