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I have seen a few posts in the forum about the 'hot air mod' to apparently fool the engine management system into lean fuel burn mode more often or constantly(?). As an old school ASE Master Tech, to me this kinda flies in the face of the 'old thought' of supplying cold air to the combustion chambers (after warm-up) which is why turbo charged cars of quality have the intercooler feature to cool the air after it gets hot from being compressed into the system by the turbo.
:?:
The hot air mod does apparently get these folks a milage boost. However, how long have these mods been installed vs. long term engine life at these super hot intake temps? Any data available on that?
:idea:
The normal air intake horn is neatly placed in the coolest stream of air available when the Insight is going down the highway, right there in the gap between the ac condenser and the hood. With just some creative work with plastic / fiberglass / sheet metal (pick your favorite to work with ) one could construct a nice ram air intake by making a funnel-like horn placed between the hood and the bumper and connect / induct it into the air horn and get a moderate little boost of cool air while at highway speed.
Concerns of rainwater / debris from the road making it into the air box would be taken care of by a couple of small holes installed in the bottom edge of the intake horn. Even without drain holes, it would take a real monsoon rain at speed on the highway to get it into the air box with the shape of the intake. The other hose attached from the lower chassis would have to be disconnected and that port blocked off for the 'ram air' effect to work, otherwise the pressure would merely go down that hose instead of into the airbox. Or to increase the effect even more, one could re-route that hose to the front and funnel it also. Since the engine management only seems to want to know the ambient air temperature, I don't see any flags about a little pressurized air.

What y'all think? I'm going to try it on mine after I get rid of some of the performance detractions I'm currently working on, like the steady speed shudder (EGR valve from posted experiences and I agree), new spark plugs at 104K miles, and the needed recalls ( headlight switch fire hazard and the parking brake button hangup ) for the 2000 5 speed.

Let the feedback begin! :)
 

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The hot air intake allows lean burn easier (high air to fuel ratio) which is good for fuel economy. The cold air intakes you spoke of are for more power instead. In regards to time my car got its hot air intake in 2001 and as far as I know it hasn't hurt anything. Have fun, Rick
 

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Hello Wayne,

I did create an auto adjusting ram air and warm air intake about a year ago.
Here is the link: http://www.insightcentral.net/forum/viewtopic.php?t=1769.

Since then I have made a larger opening for more ram air. (I should
take more pictures to update the link.) A preset bi-metal vacuum
valve and gate decides what air flow the engine will get based upon
current temperature. The warm air mod works well in the winter and
the ram air seems to work well on the highway but I have also modified
the muffler for more flow as well....Good flow in and out...

JoeCVT - Just your average CVT owner
 

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Ram air intakes don't really do anything until you get some part of the airflow approaching supersonic speeds. At the low speeds used by street cars, the air can flow around bends and edges so quickly that there's no point to having a scoop or forward-pointing intake.
 

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Dougie said:
Ram air intakes don't really do anything until you get some part of the airflow approaching supersonic speeds. At the low speeds used by street cars, the air can flow around bends and edges so quickly that there's no point to having a scoop or forward-pointing intake.
You mean the Insight can't go as fast as the SR71 (ram jet engines)?

I know I won't get the boost in PSI like a turbo achieves but you are
trying to tell me that I don't get any (even a small) increase in air
flow (at highway speeds) by having the air scoop in front?...

Are you sure about that?.... Are you saying that cars that have them
installed (even factory installation) are just a gimmick because there
is no difference at all?...

JoeCVT - Just your average CVT owner
 

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So called "ram air" is nearly totally pointless. I did the calculations a few years ago during an argument on the RX-7 Club website to prove how futile it really is. I forget the exact numbers now, but in order to create even 1 PSI of boost you need to bet travelling something like 600 MPH.

Certainly, most "ram air" setups are great in that they allow fresh, cold air into the engine. However, in the Insight, this is a bad thing (in the winter anyway) as the ECM wants to see warm air (much less dense) to obtain ideal ratios under lean burn.
 

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Hot air is less dense, cold air is more dense. Feed hot air into your engine and it just like decreasing the displacement(ie. size) while cold air is like increasing the displacement. The ECM has an intake air temperatures sensor so that the proper ratio of air molecules to gasoline molecules is maintained not matter what the temperature.

It's the same deal with "Ram Air", just another way to shove more air molecules into the engine so you can add more gas and make more power.

Which do you want? high MPG and less power or lower MPG and more power?

Why a small displacement engine is more efficent than a large displacement engine will left as a homework assignment. :wink:
 

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Discussion Starter #8
Stick your hand out

Ever put your hand out the window with the palm forward at about 50 or so? Yeah, it ain't no ramjet, but you can feel the pressure on your hand. That same pressure is going down the pipe. Just a little extra edge over stock, that's all.
 

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Wayne, I tried it. I made a really great looking job of it and had high hopes for it. After seeing that it did not seem to make any difference, I asked myself why. Better to ask first. :wink: The engine can deal with the extra presure, sure, but most of the time you don't drive with the throttle wide open. The speed of the vehicle is maintained by limiting the air flow into the engine. Increasing the presure means you have to back off on the throttle to maintain a given speed. This creates a vacuum that negates the increase in pressure. Net gain zero! It looked cool and I hated to take it off seeing as I had done such a great job of it, but how could I tell folk it was a really great mod? :oops: I'm working on a really great looking hot air mod with a selector valve. :D

Kip
 

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flunkysama said:
Hot air is less dense, cold air is more dense. Feed hot air into your engine and it just like decreasing the displacement(ie. size) while cold air is like increasing the displacement. The ECM has an intake air temperatures sensor so that the proper ratio of air molecules to gasoline molecules is maintained not matter what the temperature.

It's the same deal with "Ram Air", just another way to shove more air molecules into the engine so you can add more gas and make more power.

Which do you want? high MPG and less power or lower MPG and more power?

<snip>
All true in regard to _power_ and except for Honda's lean-burn system would have little effect on MPG. However, with the lean-burn system hotter apparently improves fuel vaporization to a significant degree. And thus further widening this lean-burn window making hyper MPG available should you choose to drive within the window.

As Kip wrote since the throttle plate limits intake air, except at WOT a ram air will have almost no measurable effect MPG or otherwise.

HTH! :)
 

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Just when I thought I was starting to understand, this new information has me a bit confused once again.
After observing intake air temperatures >110 deg. F, I've temporarily disconnected the warm air inlet (source from behind the catalytic converter shield) for the mid-summer months.
(I've also removed the partial radiator block for the summer.)
While all of the information about optimum temperatures and diminishing returns is probably contained in other threads on the forum, it may be helpful here to get a brief confirmation and clarification in one message.

Thanks in advance!
 

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I see my IAT's reach the mid 130's with my Hot air mod. Rick Reece probably has the most experience with hot air mods and has reported he sees little MPG improvement with IAT above 110F (AFAI remember). But considering the amount of heat that is "stored" in a gas (air) vs. a liquid (gasoline) the amount of heat that is believed to help improve vaporization will be much more dependent on fuel temperature. Hence the winter MPG fall off regardless of IAT. Rick had a 150F HOT ( :!: ) air mod that he has apparently deemed of little MPG value and removed.

Stated another way hot air cannot transfer enough heat in the limited time allotted if the fuel is cold. Before anyone asks heating the fuel is a very tricky proposition and for more than the obvious reasons of FIRE :!:

Clarified :?: :)

HTH! :)
 

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Thanks John. That's very helpful information. As a result, I'll probably keep the WAI disconnected until September, after which I'm considering a simple bi-metal device that will control the intake proximity to the cat. shield as a function of engine compartment temperature.

With regard to the inefficiencies of low fuel temperatures, particularly in the colder climates in winter, it would seem that in addition to having/building a contiguous garage, :wink: some type of "safe" fuel pre-heating might be possible?
If I'm not mistaken, some of the bio-diesel modified vehicles use an engine coolant based heat exchanger to pre-heat the vegetable oil, and consequently, no additives are required. The down side is that they can't switch to from conventional diesel fuel to "grease" until the engine is warmed up.

As fuel prices continue to rise, it'll be interesting to see if auto manufacturers will consider some type of "safe" fuel pre-heating for gasoline powered vehicles.
 

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John, the gas in a car must get hot when it is parked all day in the summer sun on an asphalt lot. Do you have any data for when Vapour lock or roasting the engine occur? Not that I want to toast my air filter. :lol: I suppose that painting the wings of an aeroplane black would be a really bad idea.
 

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In my opinion heating the air does help but only to a certain point. Anything above 110F or so shows little improvement in mpg however the delta between ambient air temp and 110F will vary throughout the year. Last winter I used a setup that would add +60-70F to the air temp on the highway and more in city driving. As things warmed up I gradually removed portions to keep me above 100 but not too hot.
I agree that fuel temp is also important as even with warm air intake temps winter will lower your fuel economy (Air density, tire temps and fuel temp etc). I am no mechanic and would defer to John's knowledge but don't think the fuel temp is the dominant factor. I say this because the air to fuel ratio is 22 or so to 1 and the fuel is injected to disperse it admist the air. I guess the question is wheather the air to fuel ratio is a volume ratio, a molecule ratio or something else.
Have fun, Rick
 

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nemystic said:
Thanks John. That's very helpful information.

<snip>

With regard to the inefficiencies of low fuel temperatures, particularly in the colder climates in winter, it would seem that in addition to having/building a contiguous garage, :wink: some type of "safe" fuel pre-heating might be possible?
If I'm not mistaken, some of the bio-diesel modified vehicles use an engine coolant based heat exchanger to pre-heat the vegetable oil, and consequently, no additives are required. The down side is that they can't switch to from conventional diesel fuel to "grease" until the engine is warmed up.

<snip>
Your welcome, but

Well,

Were just really "guessing" at the many reasons for the major difference in attainable MPG in warm vs. cold weather. Even after a long warm-up is allowed hyper MPG is much lower in the winter.

Warming diesel or "grease' ;) is a much different proposition than gasoline :!: And except for a car like the Insight the benefit would be much more limited (if we are correct in our assumptions).

HTH! :)
 

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b1shmu63 said:
John, the gas in a car must get hot when it is parked all day in the summer sun on an asphalt lot. Do you have any data for when Vapour lock or roasting the engine occur?

<snip>

Vapor lock can occur at a high enough temperature. But in most newer fuel injection cars the higher fuel pressure in the lines further suppress the fuel's ability to "boil". The point will vary with summer blend vs. winter blend fuels too ( its one of the things that must be accounted for) and ethanol will further reduce most fuels ability to resist vapor lock.

Specific data :?: You'd have to ask your fuel supplier.

HTH! :)
 

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Rick Reece said:
<snip>

I agree that fuel temp is also important as even with warm air intake temps winter will lower your fuel economy (Air density, tire temps and fuel temp etc). I am no mechanic and would defer to John's knowledge but don't think the fuel temp is the dominant factor. I say this because the air to fuel ratio is 22 or so to 1 and the fuel is injected to disperse it admist the air. I guess the question is wheather
the air to fuel ratio is a volume ratio, a molecule ratio or something else.
Have fun, Rick
Thanks for the deferment, but I'm really shooting from the hip here. ;) Especially since the only data we have is Temperature, MPG, and some rough calculations of aero drag as it relates to temperature.

The ratio is the chemically stoichiometric ratio on the molecular level. Which _generally_ translates to a mass ratio in this case.

In addition to all the other good physical properties that you listed which inhibit hyper MPG I think its a fuel vaporization issue. And that the small droplets that an injector sprays into the intake stream just ahead of the intake valve vaporize significantly better above a temperature threshold. Thus more complete combustion and the lean-burn systems better ability to approach its limit. Which results in the big jump in the hyper MPG potential seen in warmer weather.

I don't know where to get the factors to calculate the difference in rolling resistance of a pneumatic tire based on temperature.

Anybody else see another temperature factor we are leaving out :?:

HTH! :)
 

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i had a hot air mod from around the cat converter. i put a pc with odb2 software and on a drive down the 405, in june, (ambient around 75F) the IAT (inlet air temp) got up to 127F. i think if the air gets too hot (or thin) then power is also reduced, and you step into the throttle a little more, using more gas. i did notice morning startup was noticeably faster. probably 30% less distance traveled before autostop kicked in and operating temp was reached.
 

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effect of hot air mod on emissions

Does anyone else worry about the effect of a hot air mod on emissions? Doesn't it cool the catalytic converter as much as it heats the air? Possibly in steady-state in moderate temperatures that's fine, but insofar as it helps the car warm up faster, doesn't it also prevent the catalytic from warming up fast? And isn't a cold catalytic in the first few miles a major source of emissions?

Charlie
 
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