I've never registered for a forum just to reply to a thread I found web searching (or a couple threads here to be more precise). So I can guess how this "first post" will go over but I have to point out a couple things for those doing "warm air intakes" hopefully before they pre-ignite holes in their pistons.
1) If you're bent on causing your engine to run at sub optimal performance, then the correct way to lower the amount of air getting into your engine is with an artificial restriction.
It's completely baffling that anyone would force heat into their intake path to reduce air density when simply restricting the normal intake tubing will do a MUCH better job of it, up to a complete 100% lack of air at full blockage.
Whats more blocking the intake path is FAR more predictable, and is less likely to cause your engine to detonate itself into the road beneath your vehicle.
2) heated air outside the design parameters of your ECU is a fast way to pre-ignition and/or detonation either of which WILL KILL your MPG's and shortly their after your engine.
3) The need to use 93 octane to compensate for the hellish pinging and detonation you're causing should be a huge red neon flashing warning sign. MOST "ping" happens before and after you actually HEAR it. Most of what you HEAR when your engine is pinging is generally a result of your valve train "complaining" (so to speak), when the valves are being hammered by explosions that aren't supposed to happen at that time (or that quickly).
WAI is just so wrong on so many different levels. Never mind all of the above; unless your commute is dead flat; the decreased power will cause you to compensate by putting your foot down further and longer, slowing down and losing momentum will cause the need to speed up more often and you all surely know that acceleration is bad for economy.
Lugging up hills and when loaded, will cause knock which will force most ECU's to retard the timing, which will further cut your fuel efficiency AND performance.
So before you peen your engine into an early demise, consider: Engines cost much MUCH more than what you will save with a 1 or 2 MPG increase. Even over a few years.
While I'm not sold that a WAI is a good idea, restricting the intake seems silly. That's what the throttle is for. A 100% blockage of air will certainly improve your mileage, you won't get out of the driveway.
I switched back to my stock intake in the Geo weeks ago. I would think it makes mechanics scratch their heads when they see it and until someone comes up with solid data on FE increases on the Metro model, I see no point to WAI actually.
It all depends on the stock computers tune. A metro will get much worse mileage with air over maybe 80-90 degrees since the stock computer sucks. It depends on how the car compensates for the hot air, if the timing retards a little bit and the car gets closer to ideal timing then it can improve mileage, if its timing retards more or less than optimal then it will get worse mileage. Either way it is not the hot air actually doing anything other than making the computer do something to offset the warmer air. A car perfectly tuned will run exactly the same with hot or cold air, it will just have more power with cold air and take less throttle to do the same things as hot air.
The WAI works on cars with an Intake Air Temperature sensor. The IAT sensor tells the ECU the incoming air is hot and the ECU compensates by sending less fuel through the fuel injectors. I agree that if your car gets detonation or you have to use a higher octane gas, then a WAI is not the way to go. I don't think that an air diffuser would do anything other than hurt performance unless the O2 sensor compensates for less air.
All I know is what I have found from experience. I installed a PVC CAI on my '97 civic HX and FE went down to ~42mpg. I installed a WAI and FE went up to 45mpg. I drove for 2 months with the CAI. The WAI seems to work for me and I don't get detonation or anything. It is slower though.
On my saturn hot air seemed to help the automatic tranny shift at a lower rpm.
Using smaller diameter tubing in an air intake system seems to help fuel economy at lower RPMs. On my previous car I used slightly smaller tubing for the air intake and that seemed to help at lower rpm too (I believe this is why the civic VX has smaller intake tubing then a normal civic).
2008 EPA adjusted:
Distance traveled by bicycle in 2007= 1,830ish miles
Average commute speed=25mph (yes, that's in a car)
The VX likely has a different intake manifold with a smaller inner diameter to match the intake. This would increase the intake velocity at lower rpms. Just changing the intake to a smaller diameter would probably just lower the peak power.
A WAI can ideally increase the intake charge temperature and reduce pumping losses. A hotter intake charge means more pressure in the cylinder, so the difference between cylinder and crankcase pressure is less. It's pretty much the same thing as EGR, except due to way more heat coming from the exhaust, EGR can't be run very well at low load. A WAI should be most effective during winter and whatnot. If the engine can't compensate for a slightly increased intake temperature, the darn thing's probably gonna blow up when the driver hits a 5-10% grade.
Originally Posted by FormulaTwo
I think if i could get that type of FE i would have no problem driving a dildo shaped car.