Efficiency Modifications

[kobefan]

I recently bought a ’99 Mazda Protégé and I was looking to do any modifications that would increase my gas mileage. I’ve also read a number of articles saying the best way to increase gas mileage is to adjust your driving habits (ie: drive less, at the speed limit, etc). But in terms of modifications, the only recommendation I’ve gathered is to replace the stock air filter with a performance K&N filter. Are there any other modifications that are well accepted to improve mpg? Can I expect increased horsepower or performance coincidently with the mpg boost?

Thanks for your time.

[UncleBob]

keep your tires aired up to 100psi, and take the sawsall to anythign that isn't absolutely needed, and even some things that are needed to get the weight down to as little as possible.

In short, no, there's not much you can do, engine wise. The efficiency of the engine is way too cost prohibitive to make any real attempts at changing it. You're way better off buying a more efficient vehicle.

[GreyGoose006]

... and please dont inflate your tires to 100psi

although inflating them to the max listed on the sidewall will help tremendously.
typically, they are inflated a lot less by the dealer and service stations

[UncleBob]

Originally Posted by GreyGoose006

... and please dont inflate your tires to 100psi

but using the sawsall is OK?

I'll leave 'proper' tire inflation to one of the several tire threads, since its not a simple subject

[GreyGoose006]

well at least with a sawzall you are in control of what is being removed
with 100 psi in your tires, you would probably loose the whole car in one fell swoop if you tried to turn

[INF3RN0666]

Do not buy a K&N filter man. That's a performance filter that clearly states "HIGH FLOW FILTER" on the box. High air flow = more fuel in cylinder in order to get proper combustion. In the end, more fuel burnt per stroke = less fuel efficient. Unless you're trying to squeeze out power, high flow filters are useless.

[Sute]

to improve MPG you need to set a lean mixture in the cyliders, to get high performance you need to set a rich mixture, even though with modern electronic control system, its still hard to converge two points perfectly.

[2.2 Straight six]

no, you need a 14.7:1 air/fuel ratio. it doesn't matter what state of tune your engine is, 14.7: is the optimum A/F ratio.

running lean can cause pre-detonation and can damage pistons/valves/heads/etc. running too rich can cause cylinder wall washing and increased wear.

[Sute]

Stoichiometric value is the best value for good efficiency of catalyst, but to get the MAX power, its better to set a mixture ratio slightly less than 14,7

[2.2 Straight six]

yes, for maximum power a slightly lean mixture provides better burn.

the downside being that you can't do that too much because of the temperatures involved. many race cars run slightly rich because the extra fuel in the mix lowers combustion chamber temps.

[Sute]

detonation can be solved by ECU, reducing the ignition advance

[Sute]

<14,7 should mean rich.....i suppose...

[UncleBob]

Originally Posted by Sute

<14,7 should mean rich.....i suppose...

yes. Max power is traditionally between 12.8 and 13.0 AFR

[Stale Trooper]

Originally Posted by INF3RN0666

Do not buy a K&N filter man. That's a performance filter that clearly states "HIGH FLOW FILTER" on the box. High air flow = more fuel in cylinder in order to get proper combustion. In the end, more fuel burnt per stroke = less fuel efficient. Unless you're trying to squeeze out power, high flow filters are useless.

Just my , but If you can't get it out, you can't stuff more in; Any low restriction air intake/filter is useless until & unless you also make changes to the exhaust. Headers, Low restriction mufflers, and oversized pipes are the cheapest mods for power/performance, or economy. I've been tuning both ends of the scale for almost 50 years, depending on the need and expected use of the vehicle. Trust me, I've tried just about everything, and achieving a good air flow through the engine is the whole secret, no matter what your target is.... Power, or ECONOMY.

[curtis73]

Originally Posted by Sute

detonation can be solved by ECU, reducing the ignition advance

Yes, but retarding the ignition will most certainly hurt MPG and HC emissions.

Keep properly inflated tires, drive like a grandma, and enjoy. There really isn't much else you can do. Most factory fuel curves are one step on the rich side to prevent detonation and reduce NOx (at the expense of HC) emissions. Having someone reprogram for a little less fuel might save you a half of one mpg, but it might cost $300 to do the work. Compare the cost versus what you save and see how long it will take to recover.

Other things you can do; run thinner tires. Contrary to popular belief, tire width does not affect how much rubber is contacting the road, it simply affects the shape of the contact patch. A long skinny contact patch provides less rolling resistance than a short fat one. Also select touring-type tires instead of performance tires. The smaller treadblocks not only help wet and noise performance, they offer less rolling resistance.

Avoid fuel additives or high octane fuel. Wastes of money.