I guess I'm a skeptic about this. Here are my reasons.

1. Cooler inlet air? Maybe a little. I doubt that at speed, the air inside the engine bay is much warmer than outside air. The air intake opening is about 2 inches from the grill, and between the grill and that big 11 bladed exhaust fan.

2. Denser colder air = more HP? That would be true if you have a mass flow system, but carbs, and CSI systems can't compensate for air density. So denser air will result in a leaner mixture. This could result in more HP, if you were rich to begin with. So getting more air into the engine only helps if you can also get more fuel in.

3. Adding any length of hose or tubing to the intake will restrict intake at the time that you will need it most (stopped or slow speeds) in exchange for more air when you need it least (high speed).

4. Why does Pontiac advertise "RAM AIR INJECTION"? Cause it's a cute thing to stick on the the side of their hood scoops.




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Bill Krause
'79 911SC Euro

I have restored and owned vw bugs for years and I was thinking about trying out a trick on my 911 that we sometimes do to bugs. Both engines have heater ducts. I would remove the heater hoses and reroute them to a rigged air cleaner. Since carburated, there might be a problem with running lean but the fan that is suppling the volume of air is relative to that of the engine rpm. I certainly noticed a difference on the bugs although I also agree it isnt the best method but hell, I rather have the air be pushed than sucked into the carb. I have carbs on my 911 with the K&N independant air cleaners. I am thinking of returning to the original air cleaner and connecting a heater blower hose to the small inlet. I see these cars as learning experiances so if it doesn't work simply take it off.This idea almost has to give you benfits. It sounds logical. If it doesn't work at least it will look like something out of mad max!!!

Those of you who follow motorcycle RR will know about Yoshimura's GSXR goodies. I know even back in 87 they had cold air scoops that went from the front of the fairing to the carb area. They also had a heat sheild between the carbs and head and insulated the fuel tank to keep the gas temps down some. They also made side shields to enclose the carb area like a make shift air box around the bug suckers (velocity stacks).

For Poski. I have been using thermotec tape on my bike for years. The tuner theory is to keep the heat up in the exhaust prevent it from slowwing down. The side benefit is not cooking my feet or my fancy Alpine Star boots. The stuff does do a pretty good job of insulating and I have to think it works a little. I had to richen up the jetting after wrapping the pipe, and it did seem a little stronger on the top.
I have to think Rarly is on to something. I want to up grade intercoolers but why let the air heat up in the first place? I am thinking a GT 2 wing is the way to go.
david 89 turbo cab

I still think this is an intriguing idea, but I still do not believe that the result is cooler intake air. Denser maybe.

The cooling fan is evacuating the air in the engine compartment at the rate of probably five or six (or more) engine-compartment-fulls of air EACH SECOND. This is just my very valuable and accurate opinion. Oh, and humble too.

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'83 SC

Old Skul,
I searched the board and Scott Matre said he had the Eram set up on his car, he said it made a difference, Scott are you out there?? Also, I think the power increase for the cold weather was maybe two fold for me, yes theres the colder denser air, but that was also the first day in ages that the AC was off. This would also eliminate the AC compressor drag and the pre-heating effect of the condensor on the air coming in to the engine compartment.

wckrause,

#2 seems to be a good point. I don't know enough about CIS though, to comment intelligently on it.

Carbs, however, should send more fuel in there, since the fuel is drawn in due to the air moving through the carb (venturi effect). More air = more gas.

As for #4, Cars.com tells us the following: "The [2000] Firebird is again available in five models - a Base, Formula and Trans AM coupe, as well as a Base and Trans AM convertible....Standard on the Formula and Trans Am is a 5.7L 305-hp engine, which improves to 320-hp when equipped with the Ram Air Performance and Handling Package."

My contact at GM tells me with respect to Pontiac ram-air: "BTW, they do have mass air flow sensors."

Supes, the easy way to find out is empirically: install temp sensors, one inside the engine bay (or intake, even) and one outside. Let us know your results. http://www.pelicanparts.com/ultimate/smile.gif

blue

[This message has been edited by BlueSkyJaunte (edited 09-27-2000).]

Hell!! lets put some 220 mains and 210 airs and add a vw rabbit vent blower motors to each velocity stack making a total of six electric motors (now they put out volume). Since the mains dont kick in until around 3000rpm, have an rpm activated switch running the electric motors, that way you dont run lean below 3000rpm. Hold on because either you will be blowing by cars or your motor will. Yeah Baby!!!!

I tried to remain silent but, I can't take it anymore!

Generally, cold air DEFINITELY makes a difference. I respect the skeptics, being one myself, but you can't argue with reality.

I am by no means the Yoda of horsepower, but I can safely say that AT LEAST 90% of engines will produce more horsepower with colder intake air and no other modifications or adjustments regardless of engine type (fuel injected, carbureted, supercharged, turbo charged, intercooled, . . . ) or vehicle type (car, motorcycle, . . . ). For the smart asses out there, I'm sure there are exceptions, although they are rare, but that's why I said "at least 90%". http://www.pelicanparts.com/ultimate/smile.gif No, your engine is probably not one of the 10%.

FYI: At Indy (the 500, not the Super Cup race http://www.pelicanparts.com/ultimate/smile.gif ), they refer to the last hour of practice and qualifying as "happy hour" (between 5:00 pm and 6:00 pm). This is because it's the coldest time of day, and they get the most power and fastest lap times. Actually, you could probably ask any hardcore racer about this phenomenom. I mean someone (driver, mechanic, etc.) that has spent alot of time at a track trying to shave down their lap times, not someone who is a hobbyist who isn't fighting for time. This phenomenom is pretty much common knowledge, or so I thought.

Also FYI: The rule of thumb I've heard is that there is a 1% increase in horsepower for every 10 degree farenheit drop in temperature. Don't bother aguing with me on this because I know it's obviously not that accurate.

You skeptics may want to try driving around on a hot, humid (humidity displaces oxygen --> also less power), sunny day and then drive around late that night when things cool off. Maybe something like an 85 degree day and 65 degree night. I'm confident that you'll feel the difference regardless of vehicle or engine type.

b-man


[This message has been edited by b-man (edited 09-27-2000).]

This discussion is starting to sound a lot like the discussion on Honda/Acura websites. Those Riceboys have been sticking 'Cold air intake cone filters' onto their Civics and Integras. Their arguments for and against sounds exactly like this thread. They seem to have analyzed this issue thoroughly and some intake manufacturers have HP stats.

Definitely, the location of the airbox intake on a 911 is not in an ideal location.


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DW

89 Targa

I agree 100% that cold denser air will yeild more horsepower as long as the mixture is kept correct. CSI systems, and DME's with the barn door determine mixture based upon air volume, not air mass. The proper mixture is a ratio between fuel and air mass. That is why Mass Flow injection systems are superior to older systems, they can compensate for different air mass caused by either lower air temperatures or by higher pressures (either altitude, turbo, or ram air induced).
If your mixture is set properly to run at colder temperatures, you will get more HP at colder temperatures, but if you're running lean, you will run leaner at colder temperatures.



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Bill Krause
'79 911SC Euro

Lets see if we can look at this from another perspective and see if we can determine if hp increases as temperature drops.

Without getting too technical, the amount of combustion air that is pulled into an engine (not a ram air system), is is affected by the humidity in the air. Humidity (grams of moisture) takes up space in air. More humidity, less air, less combustion. Less humidity, more air, more combustion.

Lets assume that the air temp is 30F with a 100% moisture content. If air is than warmed to a temp of 75F (hypothetical situation of course) with no moisture added, than the humidity be 18.3%. There would be more air going to each cylinder, less moisture, which in turn would allow for better combustion - more power.

IF the air at 75F has a moisture content of 85% humidity and entered the engine at the same temp, than there would be no change in the humidity and the amount of combustion air would remain the same.

Hope this info helps.

As stated above, it is a well known and universally accepted principle, in performance circles, that cooler air gives better performance. Again, as stated above, Indy qualifiers know that the fastest qualifying times will occur between sundown and track closure. Happy Hour.

And I suspect that mixture changes are minimal. My CIS system is fairly simple, but it still seems to me that cooler, denser air will tend ot displace the Air Flow Sensor Plate further, richening the mixture.

And finally, adding fans to blow air into carburetors is pretty dicey. First, when you add air pressure, you might change the (venturi) vacuum that draws gasoline through the jets. Also, the fans would have to operate at a higher volume than the engine in order to create a positive pressure - the fans would ideally change volume as engine speed changes. As you all know, when these fans are run from exhaust pressure, we call this "turbocharging" and when they are turned by the engine itself, we call this "supercharging." I don't know about using electric fans. Perhaps the F-1 teams have overlooked.......

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'83 SC

As a Canadian I think I have to speak up about cold temp. performance. Lately we have been having daytime highs of about 70-75 F and are about 35-40 F in the late evenings. I love going out at night because it feels about like the car lost about 150lbs. The throttle response is considerably chrisper then during the day. I've never timed it but I'm sure that I knock at least 2/10th of a second off if not more. One of these days I'll have to do a proper test.

Anybody ever try the G-Tech Pros? Are they accurate?

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'76 911S

'80 924 M471

stormcrow,
air temperature not only affects rel. humidity but also air density ie. for a given volume, warm air has less air molecules than cold air.

I live on the equator where temperstures go up to 90+ degrees and humidity is at 90+ % as well. When it rains, my 964 feels as perkier - same effect as driving with and without airconditioning...that's more than a 1% difference. On really hot crazy days (100+ degrees), my C4 feels unbelievably sluggish like some over weight sedan with 3 cylinders

Gary, I have a G-tech, and it's fairly accurate. All I've really done with it is measure 0-60 times so far, but I can say it's a worthwhile thing to have around if you maintain or modify your own car.

I think I'm going to try the E-ram sometime soon. I have to get my valves adjusted first...after that project, we'll check this out.

There's some dyno sheets posted at the E-ram site for a 1984 911, with pics, so I have faith that works.

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Mark Szabo
1986 911 Targa 3.2

Browsed their web site...that is definitely worth looking into, I'll say that.

Dyno tests at the rear wheels are obviously a helluva a lot more convincing that flywheel numbers.... For those looking for the site:
http://www.electricsupercharger.com/www-electricsupercharger-com/autoprod.htm

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Kurt B
1984 911 Carrera Cabriolet
75 914 1.8

Any forced induction system with carbs is quite tricky. The thing to remember is the emulsion tubes and in fact all the systems of the carbs must see the Ram effect to work; if not the fuel/air could go the wrong way! Just look at the difficulties with turbo charging VW's and the carb boxes that are required for the blow through systems! I would love a few more horses; but I have enough trouble keeping my Webers running right with out trying to put 1 psi of Ram air through them and to all the air vents on the carbs! With a good stock air box and over rich main jets any low pressure Ram air system will work well though ; just look at the early 308 Ferrari's with that big side scoop and huge air box encasing the four small duel webers, quite slick, and it works to! not bad engineering, especially for the Italian's; and to think the German engineers put the 911 intake in a vacuum; how embarrassing, glad I have a 914 with one of those cool MR2 rice monster scoops http://www.pelicanparts.com/ultimate/biggrin.gif just kidding http://www.pelicanparts.com/ultimate/wink.gif