Help with some final drive math

[hayden55]

For the most part you wanna stay in max bsfc and produce the lowest horsepower needed to propel the car at x speed.. The civic was between 1750-2150 max output per g of fuel. Even the LS1 is something like 36% efficient at 2000 rpm at 70 mph which is fantastic and why like half the ls1 cars get 30 mpg on the interstate with their 0.50 6th gears. Even the new c7 corvette went more extreme and went to a 0.40 7th speed. But yeah you can always shift down. With the civic if I went to 4th it brought the rpms up to like 3000 and you could pass like how you used to.
For the most part most 4 cylinder cars have aaaabout the same bsfc chart. Look up the thread on here to make your decision. I mean if your towing a trailer it will make a big difference. But if you aren't.... wind a gear out a lil longer.
I feel like this is the ranger club. I also had a two rangers. 99 4.0 towing pack. 06 3.0. etc...

[hayden55]

I think when I graduate I'm going to get another ranger with a clean body and a long bed to Kubota diesel swap. Have you considered a diesel swap? haha

[ProDigit]

I never calculate with gear ratios and final gear drives and tires. Too much math.

I see how much RPM per MPH, and base the result on my experience with other vehicles.

Depending on the engine size, a 1.4 liter turbo engine or 1.8liter NA engine really can't take much lower than running at 2,5k RPM at 80MPH; while this is easy for any 1.6l turbo, 2.0 liter NA or more.
Those are my preferred, and most optimal gear ratios.
2.5k RPM at 60MPH for a 1.6 liter turbo hatchback or sedan results in ~40MPG avg, 50 hwy.


I once ran a my Honda Rebel 250 motorcycle at 3k RPM at 45MPH just fine. Down from 4.5k RPM. That's a drop of 33%. For such a tiny engine it ran quite low in RPM.
If I could have, I would have ran it at a 35% lower than stock ratio, but hardware wise, I wasn't able to modify the bike to go any lower in RPM. Otherwise I'd have done it.