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Powerful Plus Mileage
The main thing that I have discovered through research is that whenever someone talks about a vehicle with good fuel mileage, they generally are talking about a low horsepower small displacement engine. The real change I hope to achieve is to bring back ideas of using large powerful engines and still get reasonable mileage. I plan to post my report on as many auto discussion groups as I can and pray that an auto designer can hear what I have to say.
Typically, a good mileage vehicle is a foreign 4-cylinder car, which uses a low consumption engine to provide the owner with mileage that is affordable with $3.00 a gallon gas. I have found these vehicles to be slow and displeasing to work on and maintain. However, I believe I have found a solution to the problem.
All present day vehicles have a similar transmission set up with similar gear ratios. I may not know specifics , but first gear (on 4T60E)is generally a 1.12:1 ratio, 2nd is generally 1:1 drive is 0.89:1 and over drive is 0.84:1. This means that in order to achieve a certain speed, all motors use the same revolutions of the crankshaft (rpm) to reach that speed.
Now, to keep this simple, I will use the 1:1 ratio to do explanation. Older cars never had an overdrive anyways (this is part of why, even though old cars usually had plenty of power, they had poor mileage). To achieve 60 mph in drive all cars must go between 2000 and 3000 rpm, no matter the engine size. At this rpm a 100 horsepower 4 cylinder engine uses ¼ the fuel that a 400 horsepower V8 would. The V8 would have to go 500 rpm to consume the same amount of fuel as a four cylinder would at 2000.
With the invention of the over drive great mileage could be achieved, but the average over drive only lowers rpm slightly, making it ideal for smaller engines, because with low torque, the motor will stall if rpms are brought down too much, so if a motor with 4 times as much power was used a gear reduction that is greater can be used without stalling.
The vehicle that I think would be a great test car to attempt a gear ratio change would be an LS1 corvette (I know that they are expensive but they are light and have powerful engines with 6 speed transmissions). On a corvette, gear 5 is the drive gear and gear 6 is over drive. The reason that it has the same gear ratios in gears 5 and 6 as a regular car is so that it can speed up quicker by keeping the motor in the power band (The Corvette is obviously a performance car).
Now, if you were to change the corvette’s gearing, it could become an awesome mileage machine. Say you were to give it a different rear axel gearing (perhaps a 1.5:1 ratio) instead of the 3.5:1(est?)that it has sixth gear would be a 500-rpm gear at 60 mph instead of 2000; this would cause a great increase in mileage. You could also maintain the same performance as the original corvette by giving it one or two more over drives (7th, and 8th gears) acceleration would not be changed as the first 6 gears would be the same, and you would still bring down the rpm enough to increase mileage. You could potentially increase top speed also.
The change of the rear axel could be the best solution for cost efficiency you would simply have to find new gears instead of designing a new transmission; you could also substitute a Corvette for a Camaro similar motor and same transmission. Mileage could be increased even more if you put the same motor and transmission into and even smaller car (Malibu, Cobalt, Ect.) However, all of these things could be done and financed by someone with a slightly larger budget.
This plan is not a guarantee, I am not an expert, just a high school student, but I hate slow cars, but I also hate bad mileage, and with this plan, I think something good could happen. Thanks for Your few minutes of time and have a good day.
Name: Joshua Ambrose
Address: Windom Area Schools
PO Box C-177
Windom MN 56101
Contact: 507-831-6910 x 122
Typically, a good mileage vehicle is a foreign 4-cylinder car, which uses a low consumption engine to provide the owner with mileage that is affordable with $3.00 a gallon gas. I have found these vehicles to be slow and displeasing to work on and maintain. However, I believe I have found a solution to the problem.
All present day vehicles have a similar transmission set up with similar gear ratios. I may not know specifics , but first gear (on 4T60E)is generally a 1.12:1 ratio, 2nd is generally 1:1 drive is 0.89:1 and over drive is 0.84:1. This means that in order to achieve a certain speed, all motors use the same revolutions of the crankshaft (rpm) to reach that speed.
Now, to keep this simple, I will use the 1:1 ratio to do explanation. Older cars never had an overdrive anyways (this is part of why, even though old cars usually had plenty of power, they had poor mileage). To achieve 60 mph in drive all cars must go between 2000 and 3000 rpm, no matter the engine size. At this rpm a 100 horsepower 4 cylinder engine uses ¼ the fuel that a 400 horsepower V8 would. The V8 would have to go 500 rpm to consume the same amount of fuel as a four cylinder would at 2000.
With the invention of the over drive great mileage could be achieved, but the average over drive only lowers rpm slightly, making it ideal for smaller engines, because with low torque, the motor will stall if rpms are brought down too much, so if a motor with 4 times as much power was used a gear reduction that is greater can be used without stalling.
The vehicle that I think would be a great test car to attempt a gear ratio change would be an LS1 corvette (I know that they are expensive but they are light and have powerful engines with 6 speed transmissions). On a corvette, gear 5 is the drive gear and gear 6 is over drive. The reason that it has the same gear ratios in gears 5 and 6 as a regular car is so that it can speed up quicker by keeping the motor in the power band (The Corvette is obviously a performance car).
Now, if you were to change the corvette’s gearing, it could become an awesome mileage machine. Say you were to give it a different rear axel gearing (perhaps a 1.5:1 ratio) instead of the 3.5:1(est?)that it has sixth gear would be a 500-rpm gear at 60 mph instead of 2000; this would cause a great increase in mileage. You could also maintain the same performance as the original corvette by giving it one or two more over drives (7th, and 8th gears) acceleration would not be changed as the first 6 gears would be the same, and you would still bring down the rpm enough to increase mileage. You could potentially increase top speed also.
The change of the rear axel could be the best solution for cost efficiency you would simply have to find new gears instead of designing a new transmission; you could also substitute a Corvette for a Camaro similar motor and same transmission. Mileage could be increased even more if you put the same motor and transmission into and even smaller car (Malibu, Cobalt, Ect.) However, all of these things could be done and financed by someone with a slightly larger budget.
This plan is not a guarantee, I am not an expert, just a high school student, but I hate slow cars, but I also hate bad mileage, and with this plan, I think something good could happen. Thanks for Your few minutes of time and have a good day.
Name: Joshua Ambrose
Address: Windom Area Schools
PO Box C-177
Windom MN 56101
Contact: 507-831-6910 x 122
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