"Ram air" anyone?

[curtisr]

One of the most appealing parts of my '82 928 is the attempt to make the air intake a bit like a "ram air" affair. OK, so there is no direct connection to the outside but the attempt seems sincere. And when I look at the air intake setup on a '77 924 a not-so-very-different system exists to assist with cooling. So, me wonders, why didn't the later 924s employ a similar system for intake? I know that space appears to be an issue but given the alternative--a system that sucked water and required an eye-patch (as it were) fix along with the cutouts just waiting for a hose and, well, there it is.

My question then is: has anyone ever moved their intake the top of the rad like the 928? I know that K&N has been a popular replacement but that's not ram air and isn't ram air a good thing?

[Catamax944]

The 944S2 has the filter behind the nose panel but it's not an open filter . I'm not sure if the nose panel is a high pressure area anyway for it to work as ram air.
I did a working ram air setup on my n/a last year , over 80 mph it made some difference and i got 5mph more to my top speed.
Then i encountered the biggest problem with such a setup ,rain , the ram air is like a vacuum cleaner ,sucks in everything including water. I went to a 944 meet ,300 mile round trip , rained all day ,when i got home i found water in the air filter housing and in the oil ,got milkshake , god knows how it got all the way in the oil. Fortunately the engine didn't suffer any damage , 2 oil flushes later everything was ok.
Of course i disabled the ram air intake after that mishap.

[Catamax944]

Here are pics of my setup

[teknow]

If you are referring to the air duct that runs to the back of the alternator then I recently read this was not introduced on the 924 for cooling, but to blow road salt clear of the alternator on European roads as the alternator is so low down.

That was written in a few road tests of the era, all remarkably similar and I reckon Porsche provided the data to all the journalists who copied it and added their opinions around it!

[flash968]

ram air can be effective, but it all comes down to positive and negative pressure zones, and temperature. if you can increase the pressure at the entry, and reduce the pressure at the exit, and more importantly, do that while lowering intake temps, you will gain power. on the 968, we gained almost 11hp by merely opening up the airbox, and using a better filter. ram devices show even more when used in conjunction with that.

the key to effectiveness is reducing turbulence. the accordion hose in the pic produce turbulence. that will cost. the length is also an issue. i would fabricate a mandrel bent pipe to handle most of that, and just use couplers where needed. the entry also needs to be smoother. i would get the hose to go over the plastic funnel, and not inside it. the funnel is doing very little if the hose is not connected to it and sealing off the edges.

[solex3274]

Interesting subject. I have added a 924 turbo hood and header panel to my 924S simply because it looks good, but have wondered if it could be made functional. The problem with the turbo duct is that it is on the wrong side of the hood and would require a pipe with too many bends. The header panel provides four small vents of air, but difficult to tap into. Therefore I have been using a cone style air filter which provide a nice sound, but that's all.

[AaronM]

Pure ram-air does not have any meaningful affect until you get above about 75 mph (~120 kph). At legal speeds it's really not going to do anything.

Now, getting cooler air from outside the engine compartment can make a measurable improvement at all speeds, but whether this is noticeable is debatable. The general rule is that there needs to be at least a 10% increase in power before there are measurable changes in a car's performance. Going from, say, 160 hp to 170 hp really won't make much of a difference at all in the everyday world (on a track it might be good for a tenth, which can be important, but on a street car it's really pretty pointless).

As a practical matter for a street car, the juice isn't worth the squeeze.

[rick13]

good idea...i would put some sort of screen on that inlet. very cool though.

[curtisr]

Originally Posted by solex3274

Interesting subject. I have added a 924 turbo hood and header panel to my 924S simply because it looks good, but have wondered if it could be made functional. The problem with the turbo duct is that it is on the wrong side of the hood and would require a pipe with too many bends. The header panel provides four small vents of air, but difficult to tap into.

Sol, I too have thought that with a change in place for the scoop this could be the answer. And then I saw these hoods: (I don't believe the placement shown in these pictures is above the IC.)




By the way, it turns out this idea was tackled as far back as 2007 http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/358970-its-hood-scoop-time.html

The same concerns were expressed back then about water/bug/foreign object intake. And the same defense was offered: what about the cars that have ram air? Barracudas? Mustangs? Is water really an issue? Certainly when we drive in 100 percent humidity you know that a large part of what enters the motor is water and yet we manage. My next stop was at a number of muscle car forums where this issue was addressed time and time again. The verdict? Most said water was not an issue. They did advise owners to use a washable filter, however.

Still others have talked about pressure differential, turbulence and more. It's here I'm stumped. Truth is, I don't feel an overwhelming desire one way or another but, if I got a few extra horsepower, why not?

With this nose panel, should one not have a cone in the engine bay???

[curtisr]

Catamax,

A similar setup tested and measured had some nice results. You can read it at Ram Air Project

[Catamax944]

Originally Posted by curtisr

Catamax,

A similar setup tested and measured had some nice results. You can read it at Ram Air Project

That article is complete nonsense , those results are not possible, don't believe everything you read.
Also he probably saw an mpg increase because the engine was running lean , that's just asking for it .
Like i said it worked for me to some degree but the gain wasn't worth destroying my engine. I'm sure it sucked in about half a liter of water in about 6 hours of driving in pouring rain,a glass full was in the air box and i had milkshake in the oil.
You wont see more than 5hp from this on a 8v n/a and that is over 80-100mph.

Originally Posted by flash968

the key to effectiveness is reducing turbulence. the accordion hose in the pic produce turbulence. that will cost. the length is also an issue. i would fabricate a mandrel bent pipe to handle most of that, and just use couplers where needed. the entry also needs to be smoother. i would get the hose to go over the plastic funnel, and not inside it. the funnel is doing very little if the hose is not connected to it and sealing off the edges.

Don't judge what you can't see . I won't disagree on the turbulence issue but the connections were perfect ,hose is over the funnel and is air tight on both ends sealed with heat shrink connections on both ends ,also the air box is completely sealed and pressure tight .The length of the hose you see is before it was cu to size and sealed on the funnel side.

[flash968]

i'm looking at the 3rd picture and it clearly shows the hose going inside what looks to be the funnel, with a rather large gap. if that's not it, and the hose makes an entry to the funnel that does not present any edge to catch air, then fine. the funnel will then help the air get in. it won't be as effective as a velocity stack, but it will help.

as long as the hose was cut, and not just compressed, then you will minimize the turbulence inside. a mandrel bent pipe would still flow better.

the thing to do next is to measure the intake temp change. you get about 2hp for every 15 degrees of intake temp dropped.

a manometer would then be the next thing to use to see if the pressure change resulted in better flow.

as for gains, ram air systems get their power from both increased flow, and reduced temperature. as such, they can have gains from idle up, though the most significant increases are at road speed.

regarding water, you have to use your head here. if you submarine the intake, you'll mess things up. however, i have yet to see anybody pick up any water from a location like that during non-immersive driving and send it uphill into the engine to the extent of doing any damage. the filter would stop it anyway.

[ernie9944]

[QUOTE=flash968;7240471]ram air can be effective, but it all comes down to positive and negative pressure zones, and temperature. if you can increase the pressure at the entry, and reduce the pressure at the exit, and more importantly, do that while lowering intake temps, you will gain power. on the 968, we gained almost 11hp by merely opening up the airbox, and using a better filter. ram devices show even more when used in conjunction with that.______+1


My 968 air box opening mode,& reinstall after removing the restrictive snorkel.Filter is K&N plus chip.

--Once the trims are reinstall hard to see that any mods as been done to it.

[Catamax944]

Originally Posted by flash968

i'm looking at the 3rd picture and it clearly shows the hose going inside what looks to be the funnel, with a rather large gap. if that's not it, and the hose makes an entry to the funnel that does not present any edge to catch air, then fine. the funnel will then help the air get in. it won't be as effective as a velocity stack, but it will help.

as long as the hose was cut, and not just compressed, then you will minimize the turbulence inside. a mandrel bent pipe would still flow better.

the thing to do next is to measure the intake temp change. you get about 2hp for every 15 degrees of intake temp dropped.

a manometer would then be the next thing to use to see if the pressure change resulted in better flow.

as for gains, ram air systems get their power from both increased flow, and reduced temperature. as such, they can have gains from idle up, though the most significant increases are at road speed.

regarding water, you have to use your head here. if you submarine the intake, you'll mess things up. however, i have yet to see anybody pick up any water from a location like that during non-immersive driving and send it uphill into the engine to the extent of doing any damage. the filter would stop it anyway.

Maybe i'm missing something. The only edge present is from the fog light opening to the funnel but i'm not going to ruin my valance in order to make a perfect intake .I'm not saying it was a very good setup but i actually got good results from it and have come to the conclusion that is not worth it.
Regarding the water ingress i wish you best of luck with your theory ,when you get to actually test that get back to me.
Anyway non of this is relevant anymore as i removed the hose after the water incident last year.

[flash968]

i'm talking about the pic showing the hose from underneath and rear. is that just the valance part, and not the funnel?

as for water, it's no theory. unless you immerse the inlet, it is almost impossible to get enough water past the filter to do anything. merely driving in rain would introduce no more water than a water injection system, and even then, the filter will stop it. if you're dumb enough to immerse your inlet, then you get what you deserve. i see idiots on the news all the time trying to drive through flooded streets. of course they get stuck. they deserve to get stuck. social darwinism at work.

ernie - you could improve things a bit by installing the curved edge trim rings. they act like velocity stacks, and smooth the flow. the abrupt edge you have there costs you flow. you can actually hear the difference with the right ports.

[ernie9944]

Originally Posted by flash968

ernie - you could improve things a bit by installing the curved edge trim rings. they act like velocity stacks, and smooth the flow. the abrupt edge you have there costs you flow. you can actually hear the difference with the right ports.

It's done Flash didn't have them on hand when I first did the mod,hard to find little SOB they are.

[J1NX3D]

Originally Posted by flash968

i'm talking about the pic showing the hose from underneath and rear. is that just the valance part, and not the funnel?

yes its the back of the valence. pic 3 as you indicated shows the hose over the top of the back of the scoop with something like heatshrink to seal the two.

[J1NX3D]

this idea goes back way further than 2007!

Originally Posted by solex3274

Interesting subject. I have added a 924 turbo hood and header panel to my 924S simply because it looks good, but have wondered if it could be made functional. The problem with the turbo duct is that it is on the wrong side of the hood and would require a pipe with too many bends. The header panel provides four small vents of air, but difficult to tap into. Therefore I have been using a cone style air filter which provide a nice sound, but that's all.

Originally Posted by curtisr

Sol, I too have thought that with a change in place for the scoop this could be the answer. And then I saw these hoods: (I don't believe the placement shown in these pictures is above the IC.)

By the way, it turns out this idea was tackled as far back as 2007 http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/358970-its-hood-scoop-time.html

Still others have talked about pressure differential, turbulence and more. It's here I'm stumped. Truth is, I don't feel an overwhelming desire one way or another but, if I got a few extra horsepower, why not?

With this nose panel, should one not have a cone in the engine bay???

not sure about the 2nd pic but the other 2 pics are of 924GTR's. The IC is in the nose like a 951 and likewise the turbo is on the coldside, most likely under those scoops.

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The basic 924 turbo had a log style exhaust header with the turbo on the hotside. This is what the NACA duct is for on the 924 turbo, to help cool the exhaust manifold. I've got a porsche brochure saved on my external that explains it. It doesnt just work at speed but also lets heat escape at a stand still.

re: the 924 turbo nose vents, I added a pod filter to my 924 turbo and noted an increase in intake noise and a decrease in performance. The factory added those vents to aid engine bay cooling. iirc the sheetmetal under the panel is not setup to direct air to any one point, ie to a filter. My stepfather later had a 924 turbo racecar with a 951 i/c and pod filter. As soon as I saw it I told him to get rid of it.



Even with those vents my old 932's airbox draws air from behind the headlight.


All the pod filter did was save the weight of the airbox and free up some space.

imho the 944's factory airbox with the snorkel into the wheel well is a better solution than any backyard attempt i've seen, and those backyard attempts have no imperical evidence to prove otherwise.

The only tried and true mods I've seen on these boards with data to back them are the 968 airbox mod Ernie and Flash are talking about and this 952 setup:


Without proper development and testing I think you're just wasting time, money and body panels, messing with airflow and air pressure differentials for the novelty of a different look.

[Catamax944]

Originally Posted by J1NX3D

yes its the back of the valence. pic 3 as you indicated shows the hose over the top of the back of the scoop with something like heatshrink to seal the two.

exactly

Originally Posted by flash968

i'm talking about the pic showing the hose from underneath and rear. is that just the valance part, and not the funnel?

as for water, it's no theory. unless you immerse the inlet, it is almost impossible to get enough water past the filter to do anything. merely driving in rain would introduce no more water than a water injection system, and even then, the filter will stop it. if you're dumb enough to immerse your inlet, then you get what you deserve. i see idiots on the news all the time trying to drive through flooded streets. of course they get stuck. they deserve to get stuck. social darwinism at work.

It is a theory because it's clear you are not talking from experience.
When it happened 95% of my driving was on highways ,there weren't even puddles . Water does get past the filter and very easily i might add.
The suction created by the engine alone is enough to suck in small objects, at speed the air flow gets much more powerful ,enough to easily suck up water.
Think of all the water you get on your windshield,same principal except the surface area is much smaller but is also low so you also get a huge amount of spray from leading cars.
Of course if you live in a dry climate or the setup is for a track car all of this is not relevant.

You said you never heard of this happening , now you did and you choose to dismiss the fact of it being true ; maybe it's not even the first time.

[mueller944s2]

That's what I did too, drilling the airbox made it sound much better as well

[QUOTE=ernie9944;7241900]

Originally Posted by flash968

ram air can be effective, but it all comes down to positive and negative pressure zones, and temperature. if you can increase the pressure at the entry, and reduce the pressure at the exit, and more importantly, do that while lowering intake temps, you will gain power. on the 968, we gained almost 11hp by merely opening up the airbox, and using a better filter. ram devices show even more when used in conjunction with that.______+1


My 968 air box opening mode,& reinstall after removing the restrictive snorkel.Filter is K&N plus chip.

--Once the trims are reinstall hard to see that any mods as been done to it.