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Old 02-27-2006, 01:10 PM   #1
cheapybob
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Default Modified air intake for hot air added 7.2% to mpg

That's on an increase in IAT from 37 to 90 degrees, tested on same 25 mi round trip all highway, with cruise set at 2100 rpm (60 mph) both ways, on same day with and without intake mod. Tests done with OBD II scangage.

I insulated the box and tubing today and will see if it increases the IAT and mpg further. With the standard intake I got 40.4 mpg, and with the hot air intake it went up to 42.3. I'll post again if insulating the box improves it further.
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Old 02-27-2006, 02:19 PM   #2
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Default Re: Modified air intake for hot air added 15.8% to mpg

Insulating the airbox and tube increased the IAT to about 120 degrees on the road and as high as 146 degrees in stop and go driving after the test.

Outside temp is 36 degrees, about the same as yesterday when I did the other tests. Gas mileage for the same exact round trip again with the cruise set at 2100 rpm was 46.8 mpg, which is a 15.8% increase over what I got yesterday with the stock airbox and intake. The decrease in power is noticable pulling away from a light, as I saw the TPS was up to 50, where normally it might have been 40, but given the new gas mileage numbers I'm ok with that.
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Old 02-27-2006, 02:24 PM   #3
JS593
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Default Re: Modified air intake for hot air added 7.2% to mpg

Wow, thats amazing, 46.? MPG... what did you use to insulate the intake? i wouldnt mind knowing as im trying to boost mine up a bit... however ethanol sucks here... added to all types of fuel...
...
92 SL1 SOHC TBI
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Old 02-27-2006, 02:30 PM   #4
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Default Re: Modified air intake for hot air added 7.2% to mpg

I took the resonator inlet, and filed it out to where the intake tube fit it, and extended it with dryer vent up to to the header, and drilled a hole in the airbox itself for the IAT. I used foam/foil pipe insulating tape secured with foil tape to insulate it all, leaving a couple inches near the header uninsulated. Checked after today's test and nothing had melted. Need to be careful not to have it hitting the coil packs.
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Old 02-27-2006, 02:36 PM   #5
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Default Re: Modified air intake for hot air added 7.2% to mpg

That's a significant increase!
I take it that you warm the intake flow over the exhaust manifold?
What sort of arrangement did you accomplish this?

I was reading something on the turbosaturns forum about how you can 'trick' the pcm input from the IAT sensor into thinking the air is much cooler so it increases fuel for higher performance, but the opposite may also be possible.

Since yours is OBDII, the modification was simple: two variable and two fixed resistors along with a capacitor. The original IAT sensor is disconnected. I suspect that with careful selection of components, enough adjustment range would be possible to increase fuel economy. The controls can be located in the cockpit to facilitate adjustment as needed and there may be a way to automate the controls using a piggyback pcm controller.

It may not be necessary to change the intake plumbing as ambient air temp is no longer monitored, but it is possible that in a real-world application that warmer air further increases fuel economy as it increases fuel vaporization.

Thanks for the post.
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Old 02-27-2006, 02:51 PM   #6
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Default Re: Modified air intake for hot air added 7.2% to mpg

hmm.. what about rigging a flapper valve, rigged to a manual choke cable like you can get at autozone, so you can get cold or hot air? Need performance, cold air, gas milage, hot air...
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Old 02-27-2006, 02:51 PM   #7
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Default Re: Modified air intake for hot air added 7.2% to mpg

The problem with that is that the O2 sensors will see too lean a mixture and adjust by adding fuel, I was guessing. My way the actual air temp and density really has changed and therefore the O2 sensors should be quite happy, just like driving it the desert on a hot day.

Yeah, you could rig a valve or 2 to control the flow. I was just keeping it simple. There would be no point messing with that if the theory of hotter air giving significantly better mileage didn't pan out.

Last edited by cheapybob; 02-27-2006 at 02:57 PM.
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Old 02-27-2006, 03:50 PM   #8
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Default Re: Modified air intake for hot air added 7.2% to mpg

Quote:
Originally Posted by Cheapybob
drilled a hole in the airbox itself for the IAT.
Hi Cheapybob, first of all, I have to say that your intake mod sounds awesome! From your last post it looks as if you left the IAT stock and didn't replace it with your own resistor. Is this correct?
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Old 02-27-2006, 03:59 PM   #9
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Default Re: Modified air intake for hot air added 7.2% to mpg

The sensor itself is stock, but since I removed the intake tube from the frontn and covered the hole, I had to relocate the sensor itself to the airbox near the front drivers side so the wires would still reach.

To get the system to inject less fuel per RPM, I am feeding it hot (less dense) air off the exhaust header which it matches by injecting a smaller charge of fuel. End result less power and better gas mileage.
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Old 02-27-2006, 04:06 PM   #10
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Default Re: Modified air intake for hot air added 7.2% to mpg

Here are pics of the system...
Attached Images
File Type: jpg MVC-007F.JPG (55.7 KB, 929 views)
File Type: jpg MVC-008F.JPG (58.5 KB, 834 views)
File Type: jpg MVC-009F.JPG (52.4 KB, 624 views)
File Type: jpg MVC-010F.JPG (68.3 KB, 917 views)
File Type: jpg MVC-011F.JPG (57.8 KB, 864 views)
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Old 02-27-2006, 05:11 PM   #11
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Default Re: Modified air intake for hot air added 7.2% to mpg

Everything old is new again.

I have the same setup on my 91 dodge dakota-- stock!

It sucks air from around the exhaust manifold when the intake air is cold. A little vacuum controlled door switches to cold air.

A visit to the junkyard will surely find an intake tube the approximate diameter of the saturn's.

I don't see why you can't get a vacuum solenoid that you can rig to a switch inside the car. Then you could set the cruise control on a flat level surface, flip the switch, and watch the scangauge.

This will dispell potential criticism of your technique ("oh, you must have warmed it up/changed brands of gas".... etc)
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Old 02-27-2006, 05:43 PM   #12
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Default Re: Modified air intake for hot air added 7.2% to mpg

Cool (I mean hot) idea. I've seen something similar mentioned before..involved drilling holes in the airbox.

I'll have to wreck my brain to think of something to work on the VUE..
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Old 02-27-2006, 05:49 PM   #13
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Default Re: Modified air intake for hot air added 7.2% to mpg

I've read that these WAI's work great on Honda Insights because after they warm up they switch into lean burn mode. Would a saturn tech know if the Saturn engine has this type of combustion mode built into the PCM?

BTW, Cheapybob, are you now running 87 octane gasoline or is it higher?
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Old 02-27-2006, 06:55 PM   #14
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Default Re: Modified air intake for hot air added 7.2% to mpg

Quote:
Originally Posted by eljefino
Everything old is new again.

I have the same setup on my 91 dodge dakota-- stock!

It sucks air from around the exhaust manifold when the intake air is cold. A little vacuum controlled door switches to cold air.

A visit to the junkyard will surely find an intake tube the approximate diameter of the saturn's.

I don't see why you can't get a vacuum solenoid that you can rig to a switch inside the car. Then you could set the cruise control on a flat level surface, flip the switch, and watch the scangauge.

This will dispell potential criticism of your technique ("oh, you must have warmed it up/changed brands of gas".... etc)
Same tank of gas and water temp at 179-180 degrees each time (5 mi warmup to expressway entrance). My purpose was to find a way to improve it permanently, not just for the duration of the test.

I think it would be just as easiest to rig something where when you are over 2/3 throttle it closes the hot air intake ans switches to cold, so when you need more power you get it. I'd have to get help to rig that though. I'm no mechanic, more of an experimenter making simple changes for maximum effect.
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Old 02-27-2006, 07:00 PM   #15
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Default Re: Modified air intake for hot air added 7.2% to mpg

Quote:
Originally Posted by mjo
I've read that these WAI's work great on Honda Insights because after they warm up they switch into lean burn mode. Would a saturn tech know if the Saturn engine has this type of combustion mode built into the PCM?

BTW, Cheapybob, are you now running 87 octane gasoline or is it higher?
Just cheap gas. 87 octane Mobil.
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Old 02-27-2006, 07:03 PM   #16
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Default Re: Modified air intake for hot air added 7.2% to mpg

Quote:
Originally Posted by cheapybob
I think it would be just as easiest to rig something where when you are over 2/3 throttle it closes the hot air intake ans switches to cold, so when you need more power you get it.
Something like a big PCV valve might do it.
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Old 02-27-2006, 07:25 PM   #17
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Default Re: Modified air intake for hot air added 7.2% to mpg

Quote:
Originally Posted by mjo
Something like a big PCV valve might do it.
I was thinking more like a flap valve with a return spring that would work mechanically via a cable off the throttle movement and only get to the point of opening the cold air flap when the throttle was 2/3 depressed. Probably best to find something already designed, though, even if for a different purpose.
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Old 02-27-2006, 08:18 PM   #18
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Default Re: Modified air intake for hot air added 7.2% to mpg

Those old valves like I mention on my dakota are usually vacuum activated.

At WOT= no vacuum.

I don't know which way is the "default" but when you build from scratch you'd figure it out.

There is a real gain here, not just from better fuel evaporation (admittedly pretty good stock with FI) but by cracking the throttle wider there'll be less pumping losses so you'd approach diesel-like efficiency.
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Old 02-27-2006, 08:31 PM   #19
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Default Re: Modified air intake for hot air added 7.2% to mpg

I just wonder what problems might crop up for those of us with plastic intake manifolds, and summer heat...
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Old 02-27-2006, 09:19 PM   #20
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Default Re: Modified air intake for hot air added 7.2% to mpg

what year and model car is this? manual trans?

any chance you could do some testing in the city?
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