Ram air intake vs. hot air intake

Wayne M · 07-07-2005, 08:36 PM

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?

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!

Rick Reece · 07-07-2005, 09:17 PM

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

joecvt · 07-07-2005, 09:46 PM

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/...pic.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

Dougie · 07-08-2005, 12:20 AM

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.

joecvt · 07-08-2005, 08:20 AM

Quote:

Originally Posted by Dougie

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

Aaron Cake · 07-08-2005, 09:08 AM

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.

flunkysama · 07-08-2005, 03:04 PM

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.

Wayne M · 07-08-2005, 04:47 PM

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.

b1shmu63 · 07-09-2005, 12:39 AM

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.

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?

I'm working on a really great looking hot air mod with a selector valve.

Kip

Insightful Trekker · 07-10-2005, 08:33 AM

Quote:

Originally Posted by flunkysama

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!