Why don't cars have high and low range transfer cases? It would be expensive because a another clutch and could be required (for shifting while driving right?) but I can see such a thing being of benefit in a high end luxury or sports car. Instead of 150mph at 5000rpm, it could be done at 3500rpm, with improved efficiency. And the lower range could be lower than it otherwise would be, so performance++.
High and low range transfer case in a car
- Thread starter WinkOsmosis
- Start date
You are assuming that the car's engine could actually produce enough torque to move the car 150MPH @3500 RPM, this is generally not the case.
Remember that at that speed most almost all of the available power produced is used to overcome wind resistance as opposed to actually moving the vehicle.
From Tom & Ray Magliozzi's column in Friday's newspaper:
Wind resistance increases as a square of your speed. So believe it or not, at 65MPH your wind resistance is more than double what it is at 45MPH (e.g.,65 squared vs. 45 squared)
This is why in auto racing, where speeds are typically over 100 MPH, NASCAR, CART etc., aerodynamics play such a huge role.
Well in a V12 luxury car that can do 180mph, I think 150 could be possible at 3500... but that is pure speculation.
In any case, I'd like to be able to go 80mph at 2500rpm instead of 3500.
Then maybe you should buy something with a v8 in it. Most of those probably turn less than 2500rpms at 80mph if they have an overdrive. A 4 banger wouldn't have enough power to keep the car at 80mph at 2500rpms
.I should have said and not a truck . They usually turn a little higher rpm than cars because well they are geared like a truck.
. They usually turn a little higher rpm than cars because well they are geared like a truck.
I can almost do that w/ 3.73 gears in my car (based on the calculator I used, it hits 80 at 2661rpm). If the car had stock gears in it, it'd do 80mph at 1950rpm. You just need a better car.
Better?!
It's not exactly a cruising machine. That would be the 300zx. Now if only I had the resources to swap in a 3.0 or 3.5L Nissan engine.
I believe my differential is 4.77. Maybe I should swap in a LSD from a J30. I believe it is 3.8x, and it works for many 240sx owners.
The thing with the V8 powered cars is that you still get much better performance from a higher ratio transmission, hence the differential swaps to higher ratios on Mustangs and such. So why not have BOTH a 2.86 and 3.87 or whatever the actual ratios are?
Too much of a pain in the ass. That's why camaros and corvettes and the new mustang cobra have 6 speeds in them.
If you ever go to the drag races you will see such a thing happen before your very eyes. The slicks on the top fuel cars do exactly that. They are short and fat in effect making a low (high numerically) rear end ratio off the starting line, as the car speeds down the track the centrifugal force causes the tires to become taller, effectively making a higher (lower numerically) rear end ratio which increases top speed at the end of the track.
Pretty cool huh?
Seriously? A tire couldn't possibly "stretch" more than an inch or two due to centrifical force..... Seems kinda hoaky to me, although it probably does play some role.
Originally posted by: notfred
That's not really the purpose of those tires, though
More of a pleasant side effect.
Look closely at the back tire
Notice the amount of tire above the rim vs. the amount of tire below the rim.
pic at beginning of run
pic at end of run OK not really the end of a run, more the end of a burnout, but same thing happens
Different cars, but you get the idea.
The real reason why the tires can do that...wrinkle sidewalls:
Drag Racing Tires (or more commonly called "Slicks") are a special type of tire used in drag racing where maximum acceleration in a straight line is essential. They are made of a soft compound of rubber, which affords better traction, but they tend to wear out very quickly (around 100 miles). The sidewalls of slicks are designed for straight-line performance, rather than cornering. In fact, as they are perfectly smooth with no tread pattern, they provide almost no traction in turns and thus are not street legal. Slicks are made of a soft compound, which are designed to give way to any stresses. The are also known as "Wrinklewalls", as they actually deform when you stomp on the accelerator. The power from the engine goes through the transmission and rear-end components, through the axles, and is applied to the rear tires. The slicks try to rotate, but are resisted by the friction of the ground. The tire ends up spinning faster at the center of the wheel than at the outer edge near the ground, which results in the tire wrinkling around a portion of the bottom of the tire. The physics behind the wrinkle is this: when the slick wrinkles, the tire creates a larger contact patch with the ground, or area where the surface of the tire and the ground are in contact. Looking at it from the ground's perspective, you would see the original contact patch, and then when power is applied, you hold onto what you had, and the tire forces more of itself down onto the ground on the front. In simple terms, the tire does flatten out, creating a larger contact patch, and thus better traction. What if that first application of power is too much for the ground's friction to hold onto, though? Well, that's simple too: the tires spin, and you lose.
TRENDING THREADS
-
Discussion Zen 5 Speculation (EPYC Turin and Strix Point/Granite Ridge - Ryzen 9000)- Started by DisEnchantment
- Replies: 25K
-
Discussion Intel Meteor, Arrow, Lunar & Panther Lakes + WCL Discussion Threads
- Started by Tigerick
- Replies: 24K
-
Discussion Intel current and future Lakes & Rapids thread- Started by TheF34RChannel
- Replies: 23K
-
-
Facebook
Twitter