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[CateraMV6]

HAI = Hot Air Intake.
CAI = Cold Air Intake.
Optimal Air Temp ~50-60deg

CAI works well in the summer when the outside temp is above 70deg.
HAI works the other way around by bumping the engine intake temp closer to that ideal temp for fuel combustion.

My observations for summer use go as follows.

OEM Summer City MPG ~18
OEM Summer Hwy MPG ~24.5

OEM Setup returned MPGs much lower then the OEM Specs with outside air at 32deg.

OEM Winter City MPG ~14.5
OEM Winter Hwy MPG ~21

Thats a drop of around 4mpg on either driving conditions.

Improvements with the HAI Have been as follows:

HAI City ~17.4
HAI Hwy ~23


Other noticeble differences have been the difference in air temp and intake temp wtih OEM and HAI set ups.

OEM is always 10deg above outside ambient temp.
HAI returns around 30deg hotter intake air then outside temp.
Example: at 32deg outside air temp the two intakes reveal the followign readings.

OEM IAT 42deg
HAI IAT 65deg

Also note that when moving cold air rushes under the hood and often the IAT drops below 60deg but in general the air receives warmer air and the following results occur.

Conclusions:
Engine warms up 30-40% faster due to air filter pulling air from above the right bank exhaust manifold.
Air temps have never been above 68deg even at idle, which is close to the underhood temps.
MPGs have been improved across the range.
HAI Set up cost me 10$ for the filter and 4$ for a 3" pipe.
Installation time took under 2min.
No Issues with clearance.





Pictures:

[Kevin Wood]

Optimal Air Temp ~50-60deg

I'm sorry, but I disagree. Higher intake temperatures will give you a drop in power with little or no increase in efficiency when injecting fuel into the port IME. It was a different story with carburettors or single point injection setups though. This is why the OEM ducting takes only cold air from in front of the radiator. 

I don't believe intake air will make any difference to warmup times either. It's primarily the heat of combustion and frictional losses that warms an engine up, and the intake air temperature will be insignificant in comparison.

Slower warmup is probably the main reason for increased winter fuel consumption - it takes longer to get out of warmup enrichment, which is based on coolant temperature.

Kevin

[Andy B]

....
It was a different story with carburettors  .....

My MkIII Cortina air filter intake was able to pivot to be able to take hot air from above the exhaust manifold or cooler air from towards the front of the engine bay & IIRC there was a 'winter' & 'summer' setting on the air filter housing.
My Cavalier coupe had a similar set-up, but done automatically using a stat.     

[Kevin Wood]

....
It was a different story with carburettors  .....

My MkIII Cortina air filter intake was able to pivot to be able to take hot air from above the exhaust manifold or cooler air from towards the front of the engine bay & IIRC there was a 'winter' & 'summer' setting on the air filter housing.
My Cavalier coupe had a similar set-up, but done automatically using a stat.     

Yep. Most carb and SPI setups had either a manual summer / winter setting or a valve with a bimetallic strip. My "over" 214 had a vacuum operated hot/cold air valve, an electric preheater in the intake manifold and the manifold also had a water jacket around it!

Where the intake manifold is "wet" you need to avoid the fuel condensing on the manifold walls, but on an Omega the fuel is injected onto an open inlet valve except when engine load is high so the cooler the better IMO.

Ever felt an increase in power on a cold day? (when you've got the traction to use it!)

Kevin

[CateraMV6]

Well I read a few articles that were toying with the idea of using under hood air for the intake in the winter to get better fuel consumption.

Now cold air is more dense and the ECU backs that up with more fuel and thus more power.   
With warmer air, less oxygen, and less fuel is required, of course less power too but power isnt what I am after.

I wanted the engine to warm up a bit faster and I observed that with the OEM set up the engine takes 2-3min to get to around 120deg watter temp.

The manifold starts to give off heat within few seconds after start up.

With the filter above the manifold I noticed taht I got to 120deg within 50sec after start up. 

Noticed alos the air temp is in the 50-60deg when moving and can top closer to 100deg when sitting idle at a stop light.

Also I have observed in general 2-3mpg better in general driving conditions when compared to the stock set up.

What I will do is switch back for a few days and then get some more readings, after that swtich to the HAI again and reconfirm my earlier observations.

I havent noticed drivability issues. The car seems to run no different with either set ups.   The nice thing is that it takes 30sec to reverse it to the OEM setup.

I will post further data once I gather up some more.

[Kevin Wood]

Well, fair play if it makes a difference. How cold are we talking about, BTW?

Kevin

[tunnie]

i like the cold air, more grunt, feels like its running smoother, no doubt cause of more fuel being burnt.

Noticed around a 20% drop in my mpg in this cold snap, was doing 35mpg now doing 29 

[CateraMV6]

Well last few days its been around 32-36 during the day, and at night it gets down to around 20.

We had a few days where the temp was down to 6deg... and didnt get any warmer then 15 during the day.  On those days the HAI made the biggest difference.

Other then that I would say its worth the 15$ I spent on it.

[feeutfo]

interesting. Makes a change from the usual reason people fit those filters. But maf issues are still a reason not to fit a cone filter assuming yours is oiled?

Also, i'd blow out the air box before reverting back to the stock set up. And or tape up the outlet. Its amazing how much dust gets blown around the engine bay.

Mrs G's vw polo 1.4 16valve has a spring loaded flap in the inlet to air box. I know its there as i found bits of its rubber seal in the air box itself pre filter, and traced up stream to find where it came from.

Its spring loaded, no motor or solenoid to activate it so presume its a manual thing. When flipped one way it takes ducted air from the front of the car as normal. But the other it takes air from above the exhaust manifold, presumably for this very reason.

I havent looked into its correct operation in the manual because its fallen apart, and couldn't see it making much odds anyway as even intact its not an air tight seal. Its rare we get less than 5c temp for more than a week or 2 each year anyway.(now i've said that its bound to freeze til june now)

I guess only you can judge your weather and if its worth the agro.

[CateraMV6]

Here is a cool link with a good amount of info, theories and testing of the Warm Air Intake, WAI methods for improving MPG.

All of these note that engine power will be reduced but efficiency will go up.

http://www.metrompg.com/posts/wai-test.htm

[CateraMV6]

To update on this mod, I have seen better MPG numbers around town but the problem is that the hot air kills the torque of the motor, so in most cases I find myself doing WOT just to hear the roaring sound from the intake side and as you can imagine that kills MPGs...


In general I saw 17-18mpg city, sometimes as high as 19mpg, highway was around 25 all around.

Since the thermostat went out, now the car runs at 175 city and 150-160deg highway so the motor is dumping a ton of fuel and as a result the highway mpg was 20.1 on the trip back from chicago.

Its time to do the thermostat and this weekend I will be doing exactly that.

[Marks DTM Calib]

Interesting, I would actualy expect the warm up time to be slightly improved as when you consider the volume of cold air passing through the cylinders and the cooling effect it has, it not insignificant.

And if you can get to temp quicker then the system can run at optimum efficiency sooner.

I would want it switching over once the system had warmed up though....

[CateraMV6]

I replaced my thermostat, and numbers seem to be back up again...

Warm up time is rather quick and MPGs are back on the rise.

Seems a good set up for very cold weather.

As soon as the weather gets above 40deg I am switching back to stock.