Master list of 65+ proven mods for increasing MPG

[stonebreaker]

You guys are barely touching engine mods. Coming from a hotrodder background, there are a lot of mods the rodders do specifically to increase the efficiency of their engines - and by that I mean get more power out of a pound of fuel. The difference is, they do it so they can go faster, you guys do it to go further. OEM's often can't afford these mods due to the expense of putting them in millions of cars, but I just have to do it to one car.

Many racing classes allow the "rollerizing" of the engine. They replace all engine bearings with roller bearings to cut internal friction. While this is prohibitively expensive for most folks, what a lot of us do is replace the OEM rockers with roller bearing versions. This is good for a peak 5hp gain all by itself, simply by cutting internal friction. I don't know what that translates to at highway speeds, but many of my friends see mileage even better than stock when using a fairly mild cam.

Exhaust: OEM's have to meet strict noise standards. Hotrodders replace their exhaust partly to improve the sound of their car, but also because the stock exhaust has a lot of backpressure. Swapping the stock exhaust on a V8 to a performance exhaust can pick up over 20 peak horsepower, simply through the reduction of pumping losses. Again, I can't say what kind of improvement you'd see at eco speeds, but at least your car will sound cool!

Intakes work the same way. Going with a K&N or some other low restriction intake can reduce engine pumping losses. We have recorded as much as a 10 peak hp increase simply by swapping the air filter.

Matching fuel injectors: The fuel injectors from the factory have flows to within +/- 10% of rated flow. The tune on the stock computer has to be able to account for this. Installing a set of flow matched injectors, which are within +/- 1% of each other, will allow a tuner to clean that slop out of the stock tune. This will allow more precise fuel metering and more spark advance, and the tuner can get real aggressive with the tune if you have the car tuned on a dyno.

[Formula413]

It seems that the consensus on freer flowing air intakes is that it will only increase peak power but not improve FE, because unless the engine is at WOT there will necessarily be a restriction somewhere in the intact tract, and whether it is from the intake itself or the throttle plate is irrelevant.

[stonebreaker]

Oh yeah, one other mod that might work in an economy situation: crankcase vacuum. A line is run from the valve cover to the exhaust; the exhaust rushing past creates a vacuum via Bernoulli's principle, reducing pressure underneath the pistons. The idea is to reduce pumping losses in the engine. The older your engine is, and the more blowby the piston rings allow, the better this mod will work for you.

[Frank Lee]

We are aware of the hot rod mods. Biggest problem is, much of the hot rod stuff makes more power by moving the rpm range higher. We can't utilize that for greater fe. The other stuff that doesn't necessarily raise the rpm range has been investigated and found in some cases to do something good and in some cases not, but nothing really gives a radical improvement.

[Christ]

Extending what Frank had just laid out -

If it doesn't make an improvement on par with the cost to implement, it's just not really going to be worth it on an economics scale. We're always searching for the "low hanging fruit" because you're already burning more calories than an apple provides when you eat it... why burn thrice as many getting to the apple, when there's one on the stem right in front of you?

[stonebreaker]

Originally Posted by Christ

Extending what Frank had just laid out -

If it doesn't make an improvement on par with the cost to implement, it's just not really going to be worth it on an economics scale. We're always searching for the "low hanging fruit" because you're already burning more calories than an apple provides when you eat it...

You mean that sculpting a full boattail for my car out of fiberglass is going to give me a full return on my investment? Does the mileage of a hybrid justify the up front cost?

Originally Posted by Christ

why burn thrice as many getting to the apple, when there's one on the stem right in front of you?

That's an easy one to answer: TO WIN!! Hotrodders are sprinters, ecomodders are marathon runners... but they're basically the same other than that. Hotrodders want to go as fast as they can, ecomodders want to go as far as they can, each one doing what he can afford (money and time) to his/her car.

[stonebreaker]

Originally Posted by Frank Lee

We are aware of the hot rod mods. Biggest problem is, much of the hot rod stuff makes more power by moving the rpm range higher. We can't utilize that for greater fe. The other stuff that doesn't necessarily raise the rpm range has been investigated and found in some cases to do something good and in some cases not, but nothing really gives a radical improvement.

I wouldn't think you'd get a radical improvement since the main focus of the OEM's has been meeting the CAFE regs. You just worry about the ounces and the pounds will take care of themselves. However, let's face it, 90% of engine advancements came from racers, not car manufacturers (forced induction, fuel injection, roller cams, etc) and more recently, GM has adopted the aforementioned roller rockers as stock on their LSx engines.

I would think one thing you can do is to improve the precision of your engine. Install flow matched injectors and tune the slop out of the stock program, for example. Something else you might think about is using smaller injectors - smaller injectors would provide more homogenous air/fuel mixture at part throttle speeds. You might need to put some sort of restriction in your air intake, or tune your computer to a lower redline maybe, to keep from going lean at wide open throttle, though.

Maybe porting your heads. Not the intake so much, but optimizing the exhaust port for max low lift flow would help reduce pumping losses.

OEM's have to meet a price point. But many folks are looking for high mileage regardless of cost - anyone who buys a hybrid, for example, fits that description. So if you look at this the same way a hotrodder looks at going fast, that is, he who improves his mileage the most wins, there are lots of things you can do to improve mileage that don't necessarily make economic sense (boat tail).

[Christ]

Originally Posted by stonebreaker

I wouldn't think you'd get a radical improvement since the main focus of the OEM's has been meeting the CAFE regs.

If only this were true....

Regarding mods paying for themselves, yes, a boat tail, in time, will pay for itself. It depends on your build technique as to how long.

Most new vehicles do not justify themselves in cost. Why would you ask that?

Why not ask basjoos how many times his $400 or so worth of mods has paid for itself compared to EPA ratings for his car?

Why not ask Darin if his FireFly EV conversion on a beer budget has paid for itself in fuel costs for the miles he's used it?

If you learn to do things in a fiscally responsible way, they can be made to pay for themselves in very short order.

Also remember that even though one mod may not have a fast payoff time, most of the mods that you'll find are supportive of further modding, so the payoff percentage increases with more mods, to a given extent.

[stonebreaker]

Originally Posted by Christ

If only this were true....

Regarding mods paying for themselves, yes, a boat tail, in time, will pay for itself. It depends on your build technique as to how long.

Most new vehicles do not justify themselves in cost. Why would you ask that?

I wasn't questioning new vehicles... just hybrids. Hybrids are a marketing scam. Compare the cost of the hybrid option on any vehicle that can be had with or without it... I did it a couple of years ago on a toyota highlander, and you'll never recover the $6500 up front cost (not to mention the additional interest on your loan, and added sales tax) of the hybrid option with fuel savings... you'll never even get close to break-even before you have to replace the batteries, no matter how long you keep the car.

Originally Posted by Christ

Why not ask basjoos how many times his $400 or so worth of mods has paid for itself compared to EPA ratings for his car?

I doubt that. He mentions in this post that he spent over 250 hours modding the car. Assuming an hourly shop rate of $50 (it's a cheap shop), that's still $12,500 in labor charges. And knowing how hotrodders like to tweak, I suspect he's seriously underestimated the amount of time he's spent on that boattail. The point being, that he did it to achieve a goal, which was to raise his mpg and lower his OPERATING costs, not so much to save costs in an absolute sense. And that's no dig against him - on the contrary, that's classic gearhead logic and I admire his dedication to his vision.

Originally Posted by Christ

Why not ask Darin if his FireFly EV conversion on a beer budget has paid for itself in fuel costs for the miles he's used it?

Same argument.

Originally Posted by Christ

If you learn to do things in a fiscally responsible way, they can be made to pay for themselves in very short order.

Some things, yes, but major mods like a boattail, no, not when you include R&D time. The only time something like that would pay off in real world terms would be if there were a commercially available kit.

Originally Posted by Christ

Also remember that even though one mod may not have a fast payoff time, most of the mods that you'll find are supportive of further modding, so the payoff percentage increases with more mods, to a given extent.

You know, there are two types of modders - those that have money to throw at the car and those that don't. If you have two guys, one who spent tens of thousands of dollars to make his car run 12's in the quarter mile, say, and you have another guy who only spent a couple of thousand to make an identical car run 12's, if you factor in the hours each guy spent tweaking and adjusting to get his car to that level, the guy with the fewer parts almost always ends up investing more in terms of time and effort than the other guy spent in dollars on his car. Yet the one that commands the most respect from other racers is the guy who used his noodle, rather than his wallet, to go fast.

Guys like Basjoos and Darin are classic gearheads. And that's a good thing. They and others like them are the innovators, the ones that the other 99% of people emulate.

[Christ]

I think we're going to have to agree to disagree on the mods paying for themselves. It's nothing personal, but I'll never agree that even some of the major mods can be done cheaply enough to pay for themselves in a short period of time.