iloveporsches

Take 1kg of liquid water at 20° C and 75 Bar, and you'll have a volume of .000995 m3. Increase the pressure to 100 Bar while holding the temperature constant and you'll have a volume of 0009972m3. It didn't change much, but it is slightly compressed under higher pressure (force/area). That said, the rods will break long before you compressed a cylinder full of water.


You'll need a thermocouple, a way to mount the thermocouple (could probably just drill a hole and epoxy it in), and a device to read the output from the thermocouple. I can't remember off the top of my head, but I know we have one in our FSAE dyno room that we use to measure EGT. I'll probably be down there tomorrow and could let you know then.

joseph mitro

in response to pressurizing the airbox - this does not make any intuitive sense at all.

correct me if i'm wrong, but you don't pressurize the airbox. you create a vacuum from the intake which draws air into the airbox, thus you don't loose any pressure by drilling holes through the airbox.
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but what do i know? we all know everything there is about cars on this board, don't we? at least everybody, including myself, think they do......

iloveporsches

I think that's correct joseph. The piston moving downward "sucks" the air in, otherwise there would be a vacuum in the cylinder. there may be other detrimental affects (slightly increased intake temp, water injestion), but I don't think pressure comes into play.

L8 APEKS

I don't think there's any harm at all to come from this mod, personally. At least...I haven't seen ANY evidence of any negative effects from a swiss-cheesed airbox, on ANY car.

Interesting that Porsche provides a swiss-cheesed airbox as an option for that "sound package" someone mentioned.

So many naysayers, so little proof! It does "tune" the intake note a little bit. Some people think that the sound alone is worth the 20 minutes it takes to do this. Different strokes for different folks. If you're so sure it "hurts performance," then don't do it. Or better yet...show us proof! Meanwhile, let the others enjoy their low budget mods. Lord knows that's about all I can afford anyway. lol.

Re-animator

Found cool pressurized airbox info on Yamaha snow mobiles.

"The benefits of forced-air induction are increased engine power by forcing the air to the airbox. From the beginning, this was never meant to be a direct induction INTO the airbox. C’mon, get real! Have you ever tried to run your sled without the airbox on a cold day with snowdust in the air? The first time you do, you’ll know it; that sled will squeak so tight so fast, you’ll wonder what happened. Even a filter or foam protection would be useless, as it would be plugged instantly.

Yamaha designed a way to force air to the airbox without the risk of also injecting snow. The only way to do this is to pressurize the underhood area with forced air. The vents along the headlight draw in air - under higher speeds – on each side of the airbox to create this pressure. The pressurized air is forced into the top of the airbox through a slot in the hood behind the headlight. If the forced air includes snowdust, ice chunks, dust or debris, it cannot make the sharp turn needed to go straight up and then back down again to enter the airbox. The air is then forced down into the bottom of the belly pan, which pressurizes the hood with clean air. This forced air system acts somewhat as a filtration system as the air entering the airbox is pre-cleaned by the pressure.

In addition, the float bowls of the carbs are vented into the airbox. This reduces the pressure during a holeshot, which enriches the fuel mixture and prevents bogging. Under higher speeds the pressure rises, creating the force. Pressurized air increases the fuel flow and adds horsepower and reduces the jetting sensitivity. Yamaha tests confirm that the pressure can add approximately 3HP under the right circumstances."

Ram air has been around in hot rodding for 4 decades.

944CS

how does pressurizing the intake not make any sense at all??that is what you do with turbochargers, and that is what you try to do with n/a's....you try to help the air keep as much velocity as possible, and when you drill holes, you are letting air escape into the engine compartment...try this, take the air filter out and turn on ur car...then rev it up with the throttle cam.....hear that? its the noise you hear when u drill the holes, only muffled by the air filter.
once again i'm not saying there is anything wrong with drilling the holes, its your car/your work of art

SoCal Driver

Porsche does not option a swiss cheeze airbox for the 944's.

However Porsche does have a factory bulliten to remove the vent hose from the belt housing to the air filter box on the NA's and cut the intake "snorkle" short because of water ingestion damage. So the answer is YES you can get enough water into the engine through the soggy paper filter to cause damage. Even more when the airfilter is closer to the front of the car.

It's your car. If you want to change things then have at it. Personally I can't see ruining good parts just so it sounds "different".

L8 APEKS

I never said it was for a 944. Earlier in this thread (page 2?) someone metioned that they did this to 993s/996s (?) or something. The point was, if it's such a horrible thing to do, they wouldn't do it.

Though I do understand not wanting to "fix what isn't broken."

I don't think water is a concern AT ALL, unless one makes a habit of speeding through 6"-8" puddles at over 30 mph, repeatedly, on a regular basis. My last Corrado had a very aggressive induction system (to match the 22psi blower, race ported head and 3" exhaust). I was going for sheer volume of air. Anyway...I ran a HUGE 3" cone filter down in front of one of the front tires. I drove the car in two pretty bad rainstorms with this setup, frequently checking the filter and taking apart the intake plumbing to check for water. Sure enough...not a drop anywhere in the system.

If that setup didn't ingest water on flooded streets, I find it hard to believe that an airbox lid with a few holes drilled in it poses any risk...unless he drives it into a swimming pool.

944CS

i don't think he meant the drilling imposed risks, he just wanted to point out that the water blowing up motors was the reason porsche recalled the snorkel in the 80's

L8 APEKS

Ahhh, 10-4.

wombat7

So here's my question... I can get the same sound from just taking the snorkel off of the car, now since Porsche put that bulletin out about the snorkel, how short should I cut it off or can I just leave it off totally??

Peckster

Don't cut it , just leave it off.

Like the doctor's oath: First, do no harm.

Or if you really must do harm, don't chit chat about it on a forum for enthusiasts.

wombat7

but wouldn't taking it off create the same intake temp problems cause by swiss cheesing your airbox

j/k

nickhance

It definately adds at least 38 horsepower.

joseph mitro

OMG, this is getting ridiculous.

a turbo pressurizes the intake to create POSITIVE intake pressure. without a turbo or supercharger there is NEGATIVE pressure (vacuum) created in the intake. air is being SUCKED IN through the holes in the airbox, not forced out.

this is a far cry from the hippocratic oath. for those that know the hippocratic oath, you know sometimes you must do harm for a greater good......

i swear i'm not replying anymore to this thread