RPM VS road speed

[Henzy]

This has come about after someone I know got a 7 day ban for being caught at 101 in a 70 (on an A road) in his supercharged V8 F-Type.
I'ts obviously a very refined car but he states "at a hundred it was just over tick over at 2K". WTF? Seriously? thats nuts!

So naturally, the next day I check my Alfa with its busso v6 and I was sitting in 6th at 4.5k.

Over to you.

[paintman]

Don't forget to post a link to youtube so we can all check your speedometer & tachometer readings. You'll also need to include the time, date & which road you were on.

[Xerstead]

Quite believable. We have Jaguar XJ limousines (Diesel V6,) at work and they run at ~1550 rpm at 70mph.
I'm fairly sure they have an 8 speed gearbox which will help.

[Henzy]

paintman said:

Don't forget to post a link to youtube so we can all check your speedometer & tachometer readings. You'll also need to include the time, date & which road you were on.

I'll make sure my number plate is in shot too.

Obviously I achieved this on brabham straight. I would suggest everyone else goes to their nearest circuit. Don't want anyone getting a 7 day ban and a fine now.

[MrTickle]

F-Type supercharged auto would be 2,165RPM @ 101MPH in 8th gear.

Because modern gearbox's have so many ratios (my Merc diesel has 9!) the top gear can be very long.

[paintman]

Henzy said:

paintman said:

Don't forget to post a link to youtube so we can all check your speedometer & tachometer readings. You'll also need to include the time, date & which road you were on.

I'll make sure my number plate is in shot too.

Obviously I achieved this on brabham straight. I would suggest everyone else goes to their nearest circuit. Don't want anyone getting a 7 day ban and a fine now.

Damn! I knew I'd missed something

[Henzy]

MrTickle said:

F-Type supercharged auto would be 2,165RPM @ 101MPH in 8th gear.

Because modern gearbox's have so many ratios (my Merc diesel has 9!) the top gear can be very long.

Wow! So how do these cars ever get up to temperature? you could be at motorway speeds ticking over and with the wind speed that must take forever.

[Foliage]

Henzy said:

MrTickle said:

F-Type supercharged auto would be 2,165RPM @ 101MPH in 8th gear.

Because modern gearbox's have so many ratios (my Merc diesel has 9!) the top gear can be very long.

Wow! So how do these cars ever get up to temperature? you could be at motorway speeds ticking over and with the wind speed that must take forever.

How do these cars get up to temperature? well when metal rubs against metal it gets warm rather easily, its still 2000 revolutions per minute, 33 revolutions per second at the crank, other parts of the engine/drive train are moving at different speeds but its still metal on metal, they haven't started using mag lev bearings just yet in road cars, all the coolant does is spread the heat out, distribute it and get the engine to a uniform temperature, then regulate the temperature down.

My diesel merc has 7 gears, cruising at 70 is just over 1800 revs iirc, which is how I can get over 50mpg out of a 3ltr engine. cruising at 50 on a motorway with roadworks, it feels like the fuel gauge is going up as the engine is running at pretty much idle.

[paintman]

Efficient thermostat in the cooling system. Keeps the engine at correct temp & only allows coolant flow into the rad if the temp rises above its opening temp so allowing the dispersal of excess heat.
If your car takes a long time to get the engine to temp - or doesn't - you've likely got a defective thermostat which has failed in the open position. Not unusual for the unscrupulous to remove the thermostat to try & mask an overheating problem when selling a car!
I had a thermostat fail some years ago on the RRC, the gauge stayed at the cold end & the heater was cool resulting in a very cold winter journey from MK to Leicester.

Edited by paintman on Wednesday 4th November 09:49

[anonymous-user]

Foliage said:

Henzy said:

MrTickle said:

F-Type supercharged auto would be 2,165RPM @ 101MPH in 8th gear.

Because modern gearbox's have so many ratios (my Merc diesel has 9!) the top gear can be very long.

Wow! So how do these cars ever get up to temperature? you could be at motorway speeds ticking over and with the wind speed that must take forever.

How do these cars get up to temperature? well when metal rubs against metal it gets warm rather easily, its still 2000 revolutions per minute, 33 revolutions per second at the crank, other parts of the engine/drive train are moving at different speeds but its still metal on metal, they haven't started using mag lev bearings just yet in road cars, all the coolant does is spread the heat out, distribute it and get the engine to a uniform temperature, then regulate the temperature down.

My diesel merc has 7 gears, cruising at 70 is just over 1800 revs iirc, which is how I can get over 50mpg out of a 3ltr engine. cruising at 50 on a motorway with roadworks, it feels like the fuel gauge is going up as the engine is running at pretty much idle.

Yes, when metal rubs against metal it gets hot but that doesnt happen in a car engine, unless you don't put any oil in it of course.

The heat is from the combustion process, compressing air and burning fuel.

[Foliage]

I was trying to keep the explanation simple...

[Spoof]

4.4 TDV8 FFRR.

50mph in 8th is 1k rpm, 100mph obviously then 2k rpm. ever so slightly longer geared than the Jags with the ZF8.

[Henzy]

REALIST123 said:

Foliage said:

Henzy said:

MrTickle said:

F-Type supercharged auto would be 2,165RPM @ 101MPH in 8th gear.

Because modern gearbox's have so many ratios (my Merc diesel has 9!) the top gear can be very long.

Wow! So how do these cars ever get up to temperature? you could be at motorway speeds ticking over and with the wind speed that must take forever.

How do these cars get up to temperature? well when metal rubs against metal it gets warm rather easily, its still 2000 revolutions per minute, 33 revolutions per second at the crank, other parts of the engine/drive train are moving at different speeds but its still metal on metal, they haven't started using mag lev bearings just yet in road cars, all the coolant does is spread the heat out, distribute it and get the engine to a uniform temperature, then regulate the temperature down.

My diesel merc has 7 gears, cruising at 70 is just over 1800 revs iirc, which is how I can get over 50mpg out of a 3ltr engine. cruising at 50 on a motorway with roadworks, it feels like the fuel gauge is going up as the engine is running at pretty much idle.

Yes, when metal rubs against metal it gets hot but that doesnt happen in a car engine, unless you don't put any oil in it of course.

The heat is from the combustion process, compressing air and burning fuel.

Yeah friction and combustion. Okay stupid question

[MrBarry123]

REALIST123 said:

Yes, when metal rubs against metal it gets hot but that doesnt happen in a car engine, unless you don't put any oil in it of course.

The heat is from the combustion process, compressing air and burning fuel.

A post befitting your username.

[300bhp/ton]

doogz said:

REALIST123 said:

Yes, when metal rubs against metal it gets hot but that doesnt happen in a car engine, unless you don't put any oil in it of course.

The heat is from the combustion process, compressing air and burning fuel.

Remove the spark plugs from your engine, and find a way to turn it over at a few thousand rpm for a few minutes, see if it stays the same temperature.

Or a simpler test for them, saw or drill a bit of metal and see if it changes temperature.

[300bhp/ton]

Henzy said:

This has come about after someone I know got a 7 day ban for being caught at 101 in a 70 (on an A road) in his supercharged V8 F-Type.
I'ts obviously a very refined car but he states "at a hundred it was just over tick over at 2K". WTF? Seriously? thats nuts!

So naturally, the next day I check my Alfa with its busso v6 and I was sitting in 6th at 4.5k.

Over to you.

Tall gearing in top. With lots of gears it would be silly to have it spinning over at high rpm in top. Not when the engine makes bucket loads of power at low rpm.

My Camaro manages 40mph per 1000rpm in top with only 4 gears. So 100mph is a sedate 2500rpm. It's no excuse though, a 100mph is 100mph. And it's friggin obvious you are doing that speed, no matter what car it is.

[MrTickle]

Interestingly - the longest geared car I know is the A8 4.2TDi

In top that is listed as 53.1MPH per 1K RPM!

So at a 100MPH you are doing less than 1900RPM

[kambites]

doogz said:

Has the lock up clutch activated by 1900rpm?

Surely it would be crazy from an economy point of view if the clutch wasn't locked at a constant cruise of anything over about 70mph? I assume these things are in top gear when cruising at 70?

[DS197]

What's with all the posts with diesels in them? Obviously they aren't going to be at high rpms at 100

[Ghost91]

I don't fancy ever going 101 mph in my swift sport, the RPM would be so high my ears would bleed!