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owly · 06-11-2019, 11:44 PM

There is no place for failure stories here, but they are as valuable as success stories. How else are we to know what doesn't work? T

I put a hot air intake on my 2010 Subaru Outback. The method was to use an automotive heater core... a fairly large one from a full size pickup. The heater core was mounted beneath the air cleaner by cutting the intake resonator or whatever it is called, that Teed off beneath the air cleaner housing on the dirty side, and bonding the core to the cut end. The inner fender needed to be removed to do this. I then installed a butterfly valve where hose that is supposed to bring fresh air from the grill goes..(which I removed). Initially this was an automotive throttle body, but I found it too restrictive, resulting in an inability to reduce the intake air temp below about 130F. I then removed that, and built a large aluminum flap that was hinged. This was operated by a vacuum cylinder built from a Clippard air cyliinder, but with a spring installed inside it. I played with spring tension to try to achieve a useful result of high temp at high vacuum, and low temp at low vacuum... it sort of worked to a degree, but I was never able to tune it to work the way I wanted it to. I then rigged a vacuum switch which was adjustable, with the idea of having two settings..... a low power high temp setting, and a high power low temp setting. The switch worked the same cylinder, but with a light spring, and vacuum from a reserve tank with a check valve. I was able to get temps ranging from about 10 deg above ambient to about 145 - 150 F.
It all worked quite well in the final iteration.........but it gained me no appreciable mileage. My observations are subjective, based on scangauge readings while on long trips of many hundreds of miles

One could say the whole thing was a colossal waste of time.... I don't look at it that way. I look at it as a learning experience that may save someone else from following the same path.

The only way I can up the mileage on this car is by manually driving, as opposed to cruise control. A absolutely hate the CVT transmission! I'm a standard transmission guy, and even with an automatic, I can resort to pulse and glide or allowing the car to lose speed on the up hill and use Georgia Overdrive on the down side. These CVTs will not tolerate being put back into gear when moving at any speed, so I only coast when coming up to a stop.

I still feel that a hot air intake can gain mileage by increasing effective cylinder pressure at low throttle settings, mimicking a higher compression engine. Essentially throttling with heat, which eliminates some throttle drag, and the fuel should burn more efficiently. Unfortunately the programming on this ECU, I suspect makes compensations that cancel out any gains. Some of that is in engine timing.

The 2010 Subaru is a fairly heavy car, and my normal driving strategies give me about a 30 mpg year round average over all. I do no "city driving" to speak of except when visiting relatives, and then I piss all the other jack rabbits off by conserving momentum so I don't have to stop.... they just do not get it that roaring from light to light and sitting at idle waiting for it gains no time and costs gas... "citiots". Rush Rush Rush, and never gain anything.

H.W.

06-11-2019, 11:44 PM	#1 (permalink)
owly EcoModding Lurker Join Date: Jan 2010 Location: Montana Posts: 33 Thanks: 0 Thanked 26 Times in 10 Posts	Hot Air Intake ....failure.... There is no place for failure stories here, but they are as valuable as success stories. How else are we to know what doesn't work? T I put a hot air intake on my 2010 Subaru Outback. The method was to use an automotive heater core... a fairly large one from a full size pickup. The heater core was mounted beneath the air cleaner by cutting the intake resonator or whatever it is called, that Teed off beneath the air cleaner housing on the dirty side, and bonding the core to the cut end. The inner fender needed to be removed to do this. I then installed a butterfly valve where hose that is supposed to bring fresh air from the grill goes..(which I removed). Initially this was an automotive throttle body, but I found it too restrictive, resulting in an inability to reduce the intake air temp below about 130F. I then removed that, and built a large aluminum flap that was hinged. This was operated by a vacuum cylinder built from a Clippard air cyliinder, but with a spring installed inside it. I played with spring tension to try to achieve a useful result of high temp at high vacuum, and low temp at low vacuum... it sort of worked to a degree, but I was never able to tune it to work the way I wanted it to. I then rigged a vacuum switch which was adjustable, with the idea of having two settings..... a low power high temp setting, and a high power low temp setting. The switch worked the same cylinder, but with a light spring, and vacuum from a reserve tank with a check valve. I was able to get temps ranging from about 10 deg above ambient to about 145 - 150 F. It all worked quite well in the final iteration.........but it gained me no appreciable mileage. My observations are subjective, based on scangauge readings while on long trips of many hundreds of miles One could say the whole thing was a colossal waste of time.... I don't look at it that way. I look at it as a learning experience that may save someone else from following the same path. The only way I can up the mileage on this car is by manually driving, as opposed to cruise control. A absolutely hate the CVT transmission! I'm a standard transmission guy, and even with an automatic, I can resort to pulse and glide or allowing the car to lose speed on the up hill and use Georgia Overdrive on the down side. These CVTs will not tolerate being put back into gear when moving at any speed, so I only coast when coming up to a stop. I still feel that a hot air intake can gain mileage by increasing effective cylinder pressure at low throttle settings, mimicking a higher compression engine. Essentially throttling with heat, which eliminates some throttle drag, and the fuel should burn more efficiently. Unfortunately the programming on this ECU, I suspect makes compensations that cancel out any gains. Some of that is in engine timing. The 2010 Subaru is a fairly heavy car, and my normal driving strategies give me about a 30 mpg year round average over all. I do no "city driving" to speak of except when visiting relatives, and then I piss all the other jack rabbits off by conserving momentum so I don't have to stop.... they just do not get it that roaring from light to light and sitting at idle waiting for it gains no time and costs gas... "citiots". Rush Rush Rush, and never gain anything. H.W.