Before I bought this car, I did some web browsing and found an excellent website that listed all the specs - from height, width, length, weight to performance details horsepower, 0-60, top speed etc etc. I can't find it now. Anyone got any suggestions?

Silly question, I know: if I am just touching 3000 rpm at 110mph, why am I not doing 220mph when it hits the red at 6000 rpm?
AFAIK, there is no slippage in the mechanical link from engine to wheels and the gearbox is a fixed ratio. What's wrong with my logic?

Regards

 

You are not factoring in areodynamic drag in a vacuum like say space that would work. It gets into physics more than i feel like talking about or ever thinking about again and plus it would take alot of background knnowledge to fully understand and i havent had a physics class in over a year and i might end up streering u wrong.

 

Drag is the biggest factor, but gear ratios and engine power play a big part as well. My Corvette has a 6-speed manual. It will go faster in 5th gear than 6th gear. If I go as fast as it will go in 5th gear, then shift to 6th, it will slow down. It doesn't have enough power to turn the second overdrive gear (6th) at that high of a speed. If I floor the gas pedal at 100 mph in 6th gear, it will go up to about 135mph or so and just won't go any faster. If I put it in 5th gear, it will go to about 172 mph (I think that's where the limiter is set).

 

I don't think it's to do with drag, wind resistance, gear ratios or engine power.
All of these will sap your power and stop you going faster, yes.

But if you are in the same gear, the ratio is set.

We can easily calculate what the ratio is:
3000 rpm equates to 110mph. The wheel is 26" diameter, which is 82" circumference.
110 mph is 7m inches per hour or 116,000 inches per minute, so at 110mph, the wheels are turning 1416 times per minute, while the engine is turning 3000 times, so the ratio is: 2.12 turns of the engine = 1 turn of the wheels.

At 3,500 engine revs in the same gear, the wheels must be doing 1650 rpm and the car must be doing 128mph
OK, drag/wind resistance mean it is harder for the car to do this, but if the car is powerful enough to get the engine to turn 3500 revs in that gear, the car must be doing 128 unless something is slipping. Could be the wheels on the road, but I doubt it, you'd lose a lot of rubber that way, could be the clutches in the gearbox, again I doubt it.

Now the car won't do 220mph, fair enough, but if it is powerful enough to get the engine up to 6000 revs, why is it only doing 155, not 220?

Suppose now you are driving against a heavy 50mph head wind or up a steep hill. You really have to floor the gas to get the car up to 110, but although the engine is straining harder to get there, it's still only doing 3000 revs and it won't get to 6000, there isn't enough power. Then drive the opposite way, you barely have to touch the gas to get to 110, but the tach is still rock steady on 3000 and it'll do 155 without trying too hard, but the tach will still be on 6000 won't it?

Must be a simple explanation, but it's a mystery to me.
Regards

 

good question.[sm=gears.gif]

 

Yes, it has everything to do with those things. Drag and friction. The faster you go, the greater the forces against the car, slowing the car. The forces are proportional relative to speed. They are not static. It takes more hp to do the same work as you go faster. Your numbers only work in a vacuum where drag and friction are not factors.

 

I still disagree with part of what you say.

The faster you go, the greater the forces against the car, slowing the car. Yes
The forces are proportional relative to speed. Yes
They are not static. It takes more hp to do the same work as you go faster. Yes
Your numbers only work in a vacuum where drag and friction are not factors. No

My numbers work on the road in the real world.
My examples about head winds and tail winds, uphill and downhill are real life examples and are proxies for increased and decreased drag. I mentioned in previous that of course it takes more hp (more stress, more gas, foot further down on the throttle) to get the same result* against wind/hill/drag and less when those forces are working with you, but at a given engine speed (revs) in the same gear, the wheels still go round a fixed number of times per minute.

*"The same result" meaning: to get the engine to achieve 3000rpm or any other number

[IMG]local://upfiles/11097/884F008218BA4537A9BE62DBE59693FD.jpg[/IMG]

 

there must be an answer for this. 155m/h is too slow for 6000rpm.[sm=rolleyes.gif]

 

It is due to the torque convertor. The torque convertor works much the same way a a clutch yet it lets the engine and transmission turn at differnt speeds. This is why in an automatic transmission car the car can be at a complete stop with the transmission still in gear. However, in a manual transmission car is if u while in gear with out the clutch disengaged then the car will stall.

 

I have nothing else to add to the physics part.

If you're looking for something mechanical to chase down, you could check the torque converter (TC). It should be locked at high speeds, but maybe yours is slipping. If you do a lot of driving at high speeds and the TC slips all the time, the trans fluid should stink enough to gag you. Take a whiff of the dipstick.

Did you buy the car used? If so, the previous owner may have installed a non-locking, high-stall TC.