MPG and HP
5th Gear Member
Joined: Mar 2005
Posts: 3,566
From: Marquette Mi
RE: MPG and HP
Well an engine that makes more torque at a lower RPM will get better mileage than one that makes less torque at the same RPM. If the engine doesnt have to work very hard to get to speed and maintain that speed, assuming its correctly tuned, it will get better mileage than one that is working harder to maintain speed.
Also gearing and vehicle weight play a part in addition to tuning and power production. If you build a 351W to make peak torque around 2800-3000 rpm it will have plenty down low and be able to maintain cruise speed easier than a 302 with a torque peak of 3500-4000 rpm.
With older vehicles with carbs think of it this way. You want to cover more distance for each revolution of the engine, so that equals either lower numberically gears or adding an overdrive. Using a car I used to drive long distances and daily as an example. It had a 403 ci engine with 2.73 gears and 28" tall tires. It would get 21 mpg on long trips and around 10-15 in town. How did it do that with a big engine? Well it was set upefficiently, with a mild aftermarket cam, headers, and the gears allowed it to cruise at a low rpm and have more than enough torque to maintain speed with a slight throttle opening.
Another car with a 350ci 2 barrrel engine and 3.08 gears was quite a bit slower, made considerably less power and was lucky to get 10mpg even when tuned quite well. It just didnt make enough power to move the car and no amount of tuning would change that. A cam swap, a 4 barrel Qjet intake, headers, and dual exhuast allowed it to make more useable power where it needed it most. Once I did that it was getting around 14-16mpg on highway and was alot more fun to drive.
If you can make torque in the right rpm range with a 302 you can get great mileage with sensible driving. An overdrive helps, but you can also get decent mileage with a 351ci engine if its set up right. After 5.0L it seems more like where and how much power it makes than what size it is.
If you have 2.5-3.23 gears and arent getting over 15mpg then you need to make some changes inside the engine or under your foot..lol
Also gearing and vehicle weight play a part in addition to tuning and power production. If you build a 351W to make peak torque around 2800-3000 rpm it will have plenty down low and be able to maintain cruise speed easier than a 302 with a torque peak of 3500-4000 rpm.
With older vehicles with carbs think of it this way. You want to cover more distance for each revolution of the engine, so that equals either lower numberically gears or adding an overdrive. Using a car I used to drive long distances and daily as an example. It had a 403 ci engine with 2.73 gears and 28" tall tires. It would get 21 mpg on long trips and around 10-15 in town. How did it do that with a big engine? Well it was set upefficiently, with a mild aftermarket cam, headers, and the gears allowed it to cruise at a low rpm and have more than enough torque to maintain speed with a slight throttle opening.
Another car with a 350ci 2 barrrel engine and 3.08 gears was quite a bit slower, made considerably less power and was lucky to get 10mpg even when tuned quite well. It just didnt make enough power to move the car and no amount of tuning would change that. A cam swap, a 4 barrel Qjet intake, headers, and dual exhuast allowed it to make more useable power where it needed it most. Once I did that it was getting around 14-16mpg on highway and was alot more fun to drive.
If you can make torque in the right rpm range with a 302 you can get great mileage with sensible driving. An overdrive helps, but you can also get decent mileage with a 351ci engine if its set up right. After 5.0L it seems more like where and how much power it makes than what size it is.
If you have 2.5-3.23 gears and arent getting over 15mpg then you need to make some changes inside the engine or under your foot..lol
I ♥ Acer
Joined: Oct 2004
Posts: 17,565
From:
RE: MPG and HP
Internet terminology, a troll is someone who comes into an established community such as an online discussion forum, and posts inflammatory, rude or offensive messages designed to intentionally annoy and antagonize the existing members or disrupt the flow of discussion as their only purpose. Obviously, this is not one. However, I have seen these kinds of troll questions erupt into inflamatory remarks, and the troller never returns with a follow-up post. Again, this is not one of those. Just keeping the house clean guys.
5th Gear Member
Joined: Jul 2004
Posts: 3,645
From:
RE: MPG and HP
yep. We had a few jokers come here and try that crap a few months ago. It was when Glen was gone, and it was really starting to **** off some of the members. me included, but our good buddy booze and hotrods fixed us up.
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