Newbie questions
 

Well Im new to the whole eco tuning, and im weaning off of performance tuning. I just bought a ford focus 2.0l zetech with a 5 speed. I bought this car because the engine has solid lifters so I can really lug it around at low rpms. Now im not hardcore about mileage, I still go full throttle on a regular basis BUT I drive to hours each way for my weekend commute and I will be driving 80 miles per day to school next year.

Here's my question- do cold air intakes really improve my mileage? And what about a less restrictive exhaust or headers? Basically, I want to mod my car in a way that won't effect the looks or hurt performance (if it makes it faster thats fine by me, but give me a 10-15% increase in mileage. My first mod will be a block heater.

Also, what do you guys think of those pulse plugs? (the spark plugs with capacitors) they run $50 a piece, so if they are a scam I would like to know lol.

Cold air intakes hurt mileage, if anything. Intake restriction does not matter at part throttle. Backpressure does hurt economy, but if your system does not choke at full power, it is probably fine in the economy range. There's a pulse plug thread around here somewhere, and lots of other good advice about how to drive for economy. Welcome to the lighter side of life.

ChillyBear -

Welcome to EM! I agree with Bob. Here is info on the pulse plugs :

http://ecomodder.com/forum/showthrea...work-4020.html (no)

I sent a set to another Saturn S-Series owner, and they *fell apart* on him in less than a mile.

CarloSW2

How so?

So you're weaning off of performance tuning, but still feel the urge to gun it every once in a while, eh? That's me, too. It's interesting to note that the engine can withstand that kind of acceleration. SRI/CAI's are said to reduce pumping losses that are common in mass produced stock airboxes of the restrictive sort. Don't know about the percent of increase that your car will experience, but basically a larger diameter exhaust pipe (Depending on your car and application. On a naturally aspirated, mostly stock engine you don't want to go too big.) than your current one, granted that it's restrictive by design, can yield MPG gains through exhaust scavenging. This also reduces pumping losses (like a CAI or SRI) so that the engine doesn't have to work as hard to remove exhaust gasses (on top of everything else) that might've recirculated due to a high backpressure. I would look into the header, but only if you have enough money and patience to tune it soon after. I'm sure there's a way to have it biased towards fuel-effeciency rather than raw power with a stand-alone engine management system. But anyway, there are guys here who make it their goal to attain the highest MPG's possible. They'll be able to give you more insight on how to reach your goals. My info is from a more performance-oriented outlook.

A cold air intake only helps you get more air into your engine at wide open throttle, at cruising speed it is going to give the engine more air then it needs and thus the engine is going to dump in more gas then it needs.

Your exhaust pipe and muffler are not a duct to get the exhaust to the back of the car, larger is not better, people who say it's best to go a step bigger are bad at math as the exhaust flow in your exhaust system is coming out of the engine in pulses, there for the exhaust system needs to be tuned for those pulses, again if you are running wide open all the time that is going to shift to a larger pipe but at normal driving speeds to large of an exhaust pipe is going to de-tune your engine and make it work harder.

For your long drives you might look in to smoothing out the underside of your car.

Buy a scangage-2, it will teach you how to get more mpg, i promise! then as said, a bellypan, next tire change go with a low rolling resistance tire, look at mirror delete/reductions, exaust velocity is higher with a smaller pipe (better for low rpm where the mpg's are, if manul trans shist at 2000 rpm, time traffic lights, coast when possible, stay under 60mph, tap the tremendous resorces on this site, there are people that are expert at almost every aspect of a vehicle, and wecome.

Ah, so what you're telling me is that the car will add more fuel to the air ratio to even it out and consume more gas? I don't think the amount would be significant enough to cause a drop in fuel-efficiency. Plus, I mentioned pumping losses as an explanation for the alleged increase in MPG's that performance companies claim from their products. "Work is work," so if the engine has to "work" to get the air in, it's going to have to rev higher to do so. Don't you want to make it easier for it to do it's job?

Since you're calling me out on my math by saying that, I'm gonna call you out on your spelling. (And logic.) An engine is literally an air pump, so your first line is completely wrong. The exhaust is the medium through which gasses flow out into the atmosphere, unless of course you have an open-header setup, which is very polluting and illegal. These "pulses" are an expression of the lapses between the release of gasses from the exhaust valves. A slightly larger diameter pipe will create a more free-flowing outlet for the exhaust charge that helps scavange those gasses after each "pulse." (The opening of the exhaust valves) While the valves are closed, a vacuum of sorts is created, keeping the stream steady and constant. So to "tune" your exhaust system, that would mean upsizing the piping. The stock pipes are made restrictive for several reasons, but as it pertains to this discussion, their design is done with cost-effectiveness and mass production first, rather than top engine performance. As I said in my previous post, a restrictive exhaust system forces the engine to do extra work. High backpressure can cause recirculation of freshly released gasses, which is not a good thing. As mentioned above, (Not my post) the velocity will be higher in a smaller pipe, but it's a constant battle to keep the charge continually flowing through because it's such a small outlet. Bump the pipe sizing up liberally and the exhaust will flow freer in both the open and closing cycles of the valves more efficiently. For the record, I make WOT runs with a stylish factory exhaust all the time and know dudes with aftermarket exhausts that aim for top MPGs. "Detuning" the engine is only possible through a standalone engine management system which could potentially cause that, if you make a mistake. I guess what you're referring to is the guys with exhausts too big for their cars. That's also a bad thing, because there's simply too much room to create a significant charge in the exhaust stream, leading to less flow. If only they knew.

That's a novel idea, but what can you use that'll go under there?

BTW, this is off-topic, I'm sorry, but that's a really cool profile pic you've got there.

"Ah, so what you're telling me is that the car will add more fuel to the air ratio to even it out and consume more gas? I don't think the amount would be significant enough to cause a drop in fuel-efficiency. Plus, I mentioned pumping losses as an explanation for the alleged increase in MPG's that performance companies claim from their products. "Work is work," so if the engine has to "work" to get the air in, it's going to have to rev higher to do so. Don't you want to make it easier for it to do it's job?"

The air pump can't tell the difference between manifold restrictions and throttle butterfly. At part throttle, their relative percentages are irrelevant. Real ecomodding is a lot cheaper than performance work in some areas. What's the length of a tuned exhaust at maximum mileage? Can pulses get through the close-coupled cat, anyway?

If warm air can carry enough oxygen in for the power required, it will flow easier, and vaporize the gasoline better. Presumably, except in open-loop, near wide open throttle, the injectors will keep the mix lean, just enough for good ignition. See the "warm air intake" threads. (WAI)

I'm pretty sure that's exactly what he was referring to.

This discussion is basically endless, no matter where you go. There's always a bunch of people who heard from someone else who was told by some other guy that this way or that way was better, and very few of them have any background or math/science to back any of it up.

While it's refreshing to see that someone else understands the difference between "bigger" and "too big", it's also a burden to see, yet again, the term "back pressure" come into play.