Experimental data for Cold air intake

[kach22i]

You have to admire function, if it works well let's hope they put a sleek case cover on it. Right now it looks like hot and cold water or plumbing vents - have to start somewhere.

[Oh Haha]

George,
Looks like you opened up an old topic in posting the yellow Turbo.

[kach22i]

Originally posted by Oh Haha
George,
Looks like you opened up an old topic in posting the yellow Turbo.

I know, however it looks like I've only seen a few of the many threads on the topic - and I've been on the board for three years.

[DJC911]

This is interesting...two thoughts for the water issue:

1. Why not put a small plastic duct on top of the grill (outside the engine bay), facing to the rear of the car. The motor would still pull in the cold air, though you would lose the ram effect.

2. How about a custom hose with a small drain hose running off of the bottom of the cold air intake to the outside (left rear well). The idea being to allow the heavier water to drain out the bottom through the small hose while the air continues into the airbox. You might want a small collection up at the bottom. This should work most of the time...though I would be cautious about heading out into a heavy rainstorm. The grill would keep things from getting in that would lodge in the small hose so that the drain doesn't get clogged. The only issue I could see would be that given the speed of the passing air, it might create a siphon effect that would prevent the water from draining (i.e., air coming up the drain hose not allowing the water to go down).

I had always assumed that Porsche left the airbox opening in the car with no cold air intake from the grill because there was already enough cold air coming in and Porsche didn't want the grill opening blocked because it would prevent vital cold air from getting into the engine bay to cool the motor.

I wonder how much water gets into the engine bay through the grill when (a) the car is sitting outside in a rainstorm and (b) when the car is in motion?

[Brother]

Why not just take the cabin air via a duct through the rear shelf? Then your A/C would be making power and not loosing it. It would sound cool. I wonder if it would make your ears pop with the pressure changes.

[JP911]

I recently saw a stripped out 911 racecar (SC with a 993 body) that had the intake routed to the passenger compartment. I looked funny to see the large cone filter sticking through the rear deck, but apparently it's quite effective.

[Brother]

I wonder if it would stink after a while.

[Jack Olsen]

I posted this a while ago for another Cold Air intake thread:

"I did an experiment where I isolated the intake with an aluminum box that didn't restrict airflow, but allowed the intake to only draw air from outside the engine compartment. Then I suspended temperature sensors on both sides, to see the gap between intake temps and engine compartment temps with the 'isolator' in place. The results seemed compelling. Like Tbitz, I saw about a 25 degree (F) gap between ambient temps and engine compartment temps.

But there's a factor I think Tbitz missed, and I think it also explains why an ambient air intake doesn't improve horsepower when you test it on a dyno. In order to get repeatable results, the guy doing the testing tries to set up a repeatable, static set of conditions. Both Tbitz and I did it the same way. You take a stretch of road with a certain ambient temperature, and you run the car at a more-or-less constant speed. Sure enough, you see a nice big gap in temps, and the ambient-temp intake idea seems like it must be helping.

In my case, I set everything up and monitored the temperatures for an 8-hour drive from Los Angeles to Thunderhill, a track in northern California. When I got to the track, I left the system intact, since it was apparently reducing intake temps by anywhere from 15 to 30 degrees.

But when I took the car out and raced it, I honestly didn't feel any difference. So later in the day, I set up the thermometer displays again, and made an effort to look at the readouts while I was actually driving on the track. Surprisingly, the ambient/engine-compartment difference disappeared almost completely (0-3 degrees) when I was racing. The difference? Well, the part that hit me was that I wasn't running the engine at a steady speed anymore. And instead of 3-4K rpm, I was running it from idle to redline repeatedly. It's probably not too big a leap to say the efficiency of the main blower goes up dramatically at higher rpms, sucking all of the warm air out of the engine compartment faster than the engine can re-heat it.

And of course, it's under these kinds of conditions that you actually want to see a horsepower increase. Cruising at 3500 rpms, horsepower isn't a big deal. Flooring the gas is when we want the power, and it's also when the 911's design guarantees loads of ambient-temp air to the intake.

Still, isn't a 0-3 degree improvement worth something? I'd say yes, so long as there aren't any other trade-offs. But I would guess that any kind of long neck tube to bring cool air to the intake is also increasing the resistance/interference/obstruction (whichever it is, I'm no engineer) along the path the air has to travel. It seems counterproductive to restrict the intake at all rpms in order to cool the air only for steady state low rpm use, doesn't it?"

[Brother]

Has anyone taken pressure readings?

Interesting stuff, Jack. I thought horsepower was still lost on 911's as it heated up. Certainly dynos would pick this up even though the car is still.

[911pcars]

Race cars have more flexibility as to the placement of engine accoutrements. A typical air intake setup uses smallish NACA ducts in each rear quarter window (plexi) which lead directly into an airbox/air filter in the engine compartment or a remote air filter box in the rear seat area, then to the engine intake.

In my limited testing with my Fluke meter and thermocouple, the air temperature inside my filter housing is about the same as ambient temperatures .... at speed.

Arrow points to thermocouple wire:


When the car is idling, the engine compartment temperature rises due to reduced air flow into the engine compartment.

Sherwood

[kdubb]

In conclusion...is it better to draw cool air, or couter productive? Is the pipe set up worth the $20?

Kevin

[masraum]

Originally posted by kdubb
In conclusion...is it better to draw cool air, or couter productive? Is the pipe set up worth the $20?

Kevin

Well, Tbitz found a 7* drop in oil temps and a 15-35* drop in intake air temps when tooling around. If you do much tooling around in your car because it's a daily driver or you take it for cruises, then it might be worth it to you. Shoot, 7* is actually a fair amount in the grand scheme.

I believe that Jack discovered that on the track when the engine is constantly revving up and down and you are changing gears that he saw a minimal difference in intake air temps, and so on the track it seems not really worth it.

[Jim Smolka]

One thing about testing on a single variable experiment, if only two tests are done on each variable (i.e. once on, once off), then one does not know the inherent variability of system. In short, what is the standard deviation of the experiment? Mathematically, this can be represented as

Individual Result = Average + Main Effect of A + Standard Deviation.

If the standard deviation is larger than the one variable’s main effect, then many other factors are at play.

The best test results, the “On & Off” should happen several times and in a random fashion (i.e. On, Off, Off, Off, On, Off, On, On, Off, On). Of course the more samples the better. Then the data can be statistically analyzed to determine the magnitude of the single variable and the magnitude of the inherent variability of the system before any conclusions can be drawn.

[911pcars]

"Well, Tbitz found a 7* drop in oil temps and a 15-35* drop in intake air temps when tooling around."

I don't remember Tbitz's claim of a 7ºF drop in oil temps. Maybe I missed it.

While I applaud Tbitz's effort, I would feel more warm and fuzzy if a more accurate thermometer was used for these tests since it will influence many a DIYer's future project list. A $10 Walmart thermometer may not be as accurate when measuring higher than Death Valley-type air temps inside a vibrating machine.

Per my admittedly limited testing, I didn't experience much of any ambient vs intake air temperature diffference. One theory for the disparity is that given the amount of exposed engine metal in late model engine compartments (CIS and DME intake manifold, throttle body, fuel accumulator, engine blower, etc.), radiant heat would affect engine compartment temperatures and intake air temp. more than in earlier 911s.

The fabricated air box (link) is an interesting solution. However, it'd be better if the final version was fabricated from plastic, FG or less conductive material. Aluminum, having a high thermal conductivity value, absorbs heat and will transfer a portion of that heat to the air passing through. Don't know, but FG is probably the end plan anyway.

Current OEM intake manifolds, filter boxes and intake air tubes are made of plastic. One advantage is that plastic insulates the intake air better. Being a realist, this is probably more than offset by the advantages of cost, ease of casting accurate shapes, cost, weight and cost.

The effect of ram air is negligible unless the vehicle is beyond triple digit speeds. Even then, the shape of the ram air intake box must take the air flow into account. Pointing an open hole into the airstream by itself isn't going to cut it.

Sherwood

[Brother]

Plastic would also be better because it is less weight up higher.

[Miguel Antonett]

I believe the less restrictions on air flow creating a laminar flow (least turbulance) before combustion, would allow more and better air flow into the air intake My2C. And agreee with Jack, on the track, going up and down in RPM's the engine air flow changes so much that what you need is more air rather than temp changes... Keep in mind that an IC engine is just an air pump = more air more power. [url]http://forums.pelicanparts.com/uploads8/930+K+N+air+filter1159135094.jpg[/img]

[rnln]

Better then stock but you are still picking up hot air from the engine on aceleration from idling. I think it's better if you can make some kind of seal panels to pick up air only from the out side.
I can not think of a way for my P yet but I made one for my BMW in the past. I am not sure how much this will gain you but consider it's a fun project. I used thin sheet of metal. In the inner side, I spray several thin layers of undercoat. On the engine side, I spray undercoats, then dynamat with thin aluminum sheets. On the top, I used weather strip and made it just meet with the hood. The air-box seals the cone almost completely from the engine. There was only a small area (on the strut tower) to let air escape for air flow.

... but anyone done anymore test to prove if this really gain anything on 911?

Originally Posted by widebody911

This solution worked well with the Big A$$ Wing:



And the one I built for Jack

[movin]

How do you keep the rain/water from getting onto the filter or intake?