WAI on Civic NOT good - Free WAI GOOD :)
 

Well I've been playing around with the intake on my 2000 Civic DX, and found some interesting results.

The WAI I originally made for the car which consisted of a 3" dryer vent tube fastened to the intake filter lid and tucked under the exhaust header wound up looking great in design, but turned out to be a little TOO much heat for the car to enjoy. I wound up getting a lifetime low of 40mpg with it attached. However when I took off the WAI, and just had the stock intake out of the car (the tube attached to the intake lid, and the giant intake box looking thing?) and just ran the filter with the lid in place, I got higher mileage than I did with the stock intake intact. It's been getting great mileage ever since, too! :) I think the way it sits it pulls in warmer air from the top of the engine bay, but isn't pulling in so much heated air that it kills it. I'm going to be playing around to try to find a sweet spot where I can get the hottest air in the engine to increase my mpg's.

I just wanted to post this up there for others who may have overlooked their intakes, to take a look at it. See if you can remove some of the stock intake to get more/warmer air into the engine. In my car I only had to remove 2 bolts, and voila! better mileage! :D

(I'll try to get some pics to better explain what I mean :thumbup:)

Are you certain it is not just the fact that the intake can suck more freely?
Some manufacturers restrict the intake severely to quiten them down.

I always heard that having a free-er flowing intake, or a larger intake would only make any kind of noticeable difference at WOT, and my car stays at very, VERY low rpm's. Although it could be a bit of door #1, and a little bit of door #2, I'm not a scientist :)

Also, the intake tube part I took off is roughly the same size throughout, and the same size as the opening on the car now, but it pointed towards the front passenger side of the engine bay, away from the heat of the engine.

Intake flow restriction only is really a problem at peak horsepower (WOT and high rpms). Since we don't drive like that, restrictions in the intake (and exhaust too) usually don't effect mileage for us unless they are huge.

I agree that it is mainly for WOT and boy does it make a difference from 4,400 upward in my car but, if induction noise is any indication low revs with any more than say 1/4 throttle ie. hills it has to help to a degree.
My engine is a small high performance 4 cylinder. YMMV

Do you know the approximate temp? For my "B18", IATs in the 90-110 range have been tested as most efficient (although it's hard to keep it under 120 in the summer). Perhaps the D-series engines of the same era share common ECU tendencies for intake air...

RH77

No, sorry. I don't have any instrumentation to read the IAT.... or anything else for that matter :( I'm guessing I got it too warm, and I heard that the ECU starts to retard timing, or advance timing, or something like that to prevent any kind of catastrophic engine failure.

I tried the same thing recently and the gains were tiny. Intake air temp was 140 F when driving at night and 170 F during the day. Bloody hot! It seemed to stay in lean burn more but my commute is rolling hills and i need to get to work in a reasonable time so it had to go. I was having to give it more throttle to get anywhere. So now the intake snorkel is pointing in, towards the engine but is all stock. Intake temps are now 90 F and things are running ok. I got a temp probe with an lcd display and drilled a 3mm hole in the filter housing before the filter. Stuck the probe in there and have the display on the dash. Engine is up to temp in about 2 to 3 minutes in the 50 F weather we are having now. It used to warm up a good bit faster with the hot air intake. Suppose we had a heat exchanger on the exhaust to be the HAI but had a valve to switch away from that to a WAI when up to temp. Then we'd have the best of both worlds, no?

ollie

I always thought that would be a great idea. I was thinking about rigging one up some how and just run an old throttle cable or manual choke cable somewhere inside the car so you can switch it from HAI to Warmer-air whenever you see fit :) Would be a great little write-up if someone actually goes through with it :D

ok ok i can take a hint!:p