Warm Air Intake (WAI) insanity
 

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.

just my 2c

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.

I dunno about that.....
 

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.

I give the WAI a big :thumbup: .

i have my wai on and i hate it im gonna put my stock one on asap

I haven't done a WAI in my accord yet. What is it doing to yours, hockey?

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).

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. ;)

WAI definitely improves mileage, as long as your ECU doesn't do something like richen the mixture to prevent pinging. It seems to me that you just want to get the air temp into the 100-120 degree range. Any car should be able to run at that intake temperature. It's like a hot summer day...

A WAI sounds like a good idea, *if* you are careful and make sure you don't get pinging. A lot of people here also block radiators, and do 'engine off coasting', with 'bump starts' to start again. This could be considered bad for the oil circulation in the engine :)

Restricting the air intake will save fuel compared to flooring the accelerator pedal, however, it will cause increased pumping losses. Diesels run with no throttle plate at all, one of the reasons for their much better economy!

However, as some people here get 250% of the EPA rating in their car, I suppose it is worth it if done carefully :). I actually save $400/month by driving economically, so I could probably get a lot of engine repairs done if needed!

P.S. My non-intercooler turbo air intake pipe is burning hot to the touch when driving gently anyway so I suppose I already have a warm-air intake :). I suppose this is why my ECU is programmed to enrich at 30-40% throttle too!

1bolt just wanted to say welcome to the site. I hope you hang around.

repete dont do a wai i think that it is killing my fe! It robs of low end tourque and it makes ur car louder. I want to get rid of mine bad but idk how to put the stock one back on

Not Restriction, ECU + Atomization
 

The point of the HAI/WAI is to get the intake temps up to the level the ECU needs to run leaner -- this is especially best in Winter. I've run past the 200*F mark and saw no improvement in my application. Tests have shown that for my Integra ECU, about 90*F is ideal to satisfy the leaner requirements.

Since ambient temps are getting closer to that, a switch-out of the HAI into something cooler is needed: with temps of 70*F outside, the under-hood and IAT temps are pusing 125*F at times, which will start to move things in the other direction, efficiency-wise.

Nearly all computerized cars need to warm-up both with air and coolant temps to become most efficient (that's why drawing HAI/WAI on startup is important). Tests (by yours truly) with restrictors, super-high IATs and even CAIs have yielded some good data for my application. Make no mistake that I haven't even come close to understanding the nuances of engine air management, but for my car, the data has concluded highest efficiency is attatined with a consistently "Warm" temp, free-flow, and a stock-length and diameter tube.

RH77

The best data I've seen is on Metrompg's website and he didn't see a great difference with a WAI, which he attibuted to the fact that he believed the Metro's ECU wasn't adjusting the AFR due to the intake temp. While in theory, hotter intake temperatures may reduce pumping losses, I would think any gains made from this would be offset by the loss of power, which would then result in a larger throttle setting.

yea.. my chevettes motor control flap in the snorkel (flap that controls where the air comes from either from around the exhaust manifold, or the front of the car) that flap was stuck up all the time and boy did my mpg hit the fan...im talking liek 20's froma 4banger 4speed...so i just took that temp sensor out because thats what causes the flat to go up and so its always down now...

VetteOwner, with the flap down does it draw cold air? i remember mine failing before so i just pulled the vacuum line to it. i disconnected the tube that pulls the air from in front of the rad though so its getting warmer air from the engine bay.

Ymmw
 

This is a true YMMV mod. Most Honda OBD-II vehicles like the warmer air; whereas, vehicle's like Metro's Suzuki-clones do not see a huge improvement. Personal testing of your own vehicle can only tell.

I'm pretty confident that warm air on startup helps in most cases: carbed or injected.

RH77

yea ive tried that in the winter just so it would start and be runnign and not sucking in super cold air... yes the flap is constantly down now.

rh77 has hit the nail on the head with Hondas. I use a WAI when needed. Ive taken it off right now and am on under hood air. Thats getting to warm. Saw it as high as 105f today. I will be putting my OEM CAI tube back on any day now. That will give me for the most part 70 to 90f IAT. Im going to insulate it this summer. Heat soak starts taking over. I dont need or want over 110f IAT if I can help it.

In my latist video about 3/4 thru it Im load driving up and down some very small up and down hills. At this point I try to get a close up of the SG. Its not very clear. I was get 112 to 117 mpg and my IAT was in the mid 90'sf.


psy