WAI vs CAI test results

[MetroMPG]

Originally Posted by Matt Timion

I used SPSS to get my results.

i remember using that prog in a stats course i took.

don't worry about sending me a copy. you've confirmed that the key is to be able to figure out the standard deviation and standard error and from there you can figure the margin of error (2x standard error). if the difference between the 2 sets of data is smaller than the margin of error, it's not statistically significant.

i double checked excel, and it does give the same calculation as SPSS did for you (i made a typo when i reported the standard error was .18 further up this thread. i meant to round to .17 but accidentally made hit '8'. excel wasn't the problem, it was me.)

so this is good. it's nice to be using proper stats analysis on these tests. i'll go back to my aero tests and my k&n filter test and update them with proper margin of error info (i had it partly correct for the aero test, but not completely)

[Matt Timion]

Originally Posted by MetroMPG

so this is good. it's nice to be using proper stats analysis on these tests. i'll go back to my aero tests and my k&n filter test and update them with proper margin of error info (i had it partly correct for the aero test, but not completely)

Feel free to post results for anything you've done here. I would love to install wheel covers if it helps, as well as the K&N filter.

Now here is something I've been thinking about. We just saw that the WAI didn't help too much. Let's assume that something else you install doesn't help too much either (wheel skirts, etc.) statistically speaking do you think it might be possible for the two items combined to provide a significant improvement? My gut tells me no, but part of me thinks it might be possible.

okay, done rambling now.

[MetroMPG]

Originally Posted by Matt Timion

Let's assume that something else you install doesn't help too much either (wheel skirts, etc.)

i'm sure i've mentioned this already, but wheel skirts work. i've tested them on my car and they improved mileage by 2.8%. under controlled conditions, like today.



the k&n made no difference to steady speed fuel economy. i was so disappointed (because i blew 80 bucks on it), i actually ran a second test just to make sure (once at 80 km/h, once at 95). nada. not statistically significant. if only i knew then what i know now..

[SVOboy]

the k&n made no difference to steady speed fuel economy. i was so disappointed (because i blew 80 bucks on it), i actually ran a second test just to make sure (once at 80 km/h, once at 95). nada. not statistically significant. if only i knew then what i know now..

And matt and I were gonna go out and buy them though...But I'm still doing WAI because I know the crx adjusts fuel based on IAT and not timing, so I figure I won't run into ecu errors.

[Matt Timion]

Originally Posted by MetroMPG

the k&n made no difference to steady speed fuel economy. i was so disappointed (because i blew 80 bucks on it), i actually ran a second test just to make sure (once at 80 km/h, once at 95). nada. not statistically significant. if only i knew then what i know now..

Let's talk about cost then. How many regular air filters will you have to buy in order to break even on the K&N? Since they are good for life that has to account for SOMETHING, doesn't it?

Oh, and I think the K&N air filters are only like $40-50 for my car, so that's a plus.

[MetroMPG]

despite the test today, i think it's still reasonable to state that the WAI probably improves fuel economy on my car. just maybe not at constant speeds, as tested on a warmed vehicle.

but as matt pointed out elsewhere, WAI will cause the engine to warm up faster. warmed up engines get better mileage than cold ones. fact.

unfortunately, (1) i have no way to reliably measure this, and (2) it's probably just a tiny improvement anyway, hard to measure.

i went back into the insight forums tonight, and the primary reason they do it is because the car won't go into lean burn until the IAT sees a certain temp. everyone there claims WAI makes a measurable difference (though I never saw any talk of controlled tests - maybe the improvement is so obvious on an insight that they're not needed).

as for k&n, already figured it out: it will take 125,000 km for mine to pay for itself.

i actually considered selling it on the teamswift site, but kept it partly because it's reusable, and partly because my test was only for mpg at a constant speed (throttle opening). the filter may still offer performance and/or mpg benefits under variable throttle conditions (i.e. wider), which of course i can't test reliably.

having said that, k&n would probably not be very happy if this report was widely distributed.



"Filter efficiency is a measure of the filters overall ability to capture dirt."

much more in that link.

[rh77]

Originally Posted by Matt Timion

Let's talk about cost then. How many regular air filters will you have to buy in order to break even on the K&N? Since they are good for life that has to account for SOMETHING, doesn't it?

Oh, and I think the K&N air filters are only like $40-50 for my car, so that's a plus.

If it's any consolation, I just washed and re-oiled mine with 50,000 miles on it, and it can go a LOT longer. Air flow is increased, and top end has to be improved, although, more air can mean more fuel consumption, unless your're at cruise, then a small percentage in economy can be realized. But the kicker is that fuel IN-efficient vehicles are tested for the results and benefit the most. Pleated filters can be restrictive at high air flow rates (larger displacement engines benefit as more air is moved).

RH77

RH77

[MetroMPG]

here's another thing...

in reading some more at insightcentral.net, i discovered the claim that using a WAI in warm conditions doesn't increase mpg above "normal"; it only helps raise winter mpg up closer to the summer values.

the temps yesterday were pretty mild - the coldest CAI measurement was 53.5F and ambient was 39F.

i think i should do a second test when it's much colder to see if it reveals a larger difference between WAI and CAI.

the problem with cold weather testing is it takes the car so long to get to normal operating temp. when it's really cold, long after the engine temp has stabilized, i can watch the mpg continue to climb steadily for half an hour or more until the transaxle, cv joints, tires, bearings, etc, all reach stable temps.

makes it more difficult to do a controlled test.

[Matt Timion]

MetroMPG,

There is a guy on insightcentral that built the coolest WAI I've ever seen. I think I posted a link to it once, but I'll do it again.

http://www.insightcentral.net/forum/viewtopic.php?t=1769

Basically it's a variable temperature intake. If the temperature drops below, say, 60 degrees a butterfly opens and lets the warm air into the intake. If it's a normal summer/spring day the butterfly remains closed and only lets the cold air in.

This would be an AWESOME "how to" if you could get it working.

[rh77]

Originally Posted by MetroMPG

"Filter efficiency is a measure of the filters overall ability to capture dirt."

I'm not sure about that. Filter efficiency is the amount of air resistance required to force a volume of air through the filter. It takes less force to get air through a K&N, but that doesn't mean that it won't pick up dust and dirt particles in its oil-laden sponge.

I have used K&Ns for many years, and it has its pluses and minuses. It's very efficient -- I like like that -- the engine takes less engergy on the intake stroke to draw air in (using the principle that the engine is basically a big air pump).

After 50,000 miles, I ran a q-tip and paper towel around the inside of the intake, after the filter. It's surgically clean, so it has to be doing its job. Now I don't come across fine, sandy particles, nor have I over-oiled the filter at the last cleaning (to ruin the MAF sensor, etc.) I have a conventional pleated filter in the TL, since I don't plan on keeping it very much longer, and it's also clean.

I think if you're moving a lot of air (like in a big-block Chevy), you'll probably see big differences in power or economy with a change to a low-resistance filter.

RH77