How do the plastic air foils that mount under the car, infront of the engine, help cooling? Are they worth adding?

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They are helpful. Use them! They mix the air up so air can be picked up better otherwise the air is is ducted through under the car.

My guess is that they are worth having installed since the factory installed them for some reason. They mount on the bottom of the back edge of the firewall by 3 or 4 6mm screws, if I recall correctly. Do a search here as there were some recent post including a pic of the flaps installed.

yes yes yes.

They were mounted with 3 7mm? bolts on each side. If the car came equipped with them, there should be weld nuts on the rear body pan lip. You can easily drill and use regualar fastners ... no biggie.

As I remember, the are spaced about 15" apart from the centerline of the engine or car (There is a diagram in some manual that I have or try Pelican Parts tech section).

Purpose is to create lo pressure area under the cylinders to help suck air and aid in cooling (they do work well).

They cause a vacume to occur under the engine @ speed so as to help draw cold air in from the top & through the engine.

Engineers sit in meetings with accountants and argue for inclusion. The accountants in most cases have a lot of pull because the bottom line depends on them. You can bet your bippy (random Laugh-In reference) that these wouldn't be there if they didn't help.

pic

They induce turbulence which helps throw air along the underside of the engine as well.

Like Johny says above....
Actually they create a low pressure area behind them at speed and which helps draw down the air across they cylinders. Some of the race cars with big air dams actually remove the rear bumpers to help draw the cooling air out.

That is the reason the 914-GT didn't have a rear valence.

Are these "YEAR SPECIFIC" installs, or just certain years had these introduced?

thanks,

Fern

Okay, I'll have to goof on myself here, had a stupid moment and asked the same question twice.

Just wanted to know if it was year specific cause I don't recall predrilled holes on my 72, but then again I wasn't looking for them.

Thanks,

They were introduced on the 73 model year, and were on all 914s after that.

ever fitted on a six?

Not from the factory, but they do make a difference with retrofitted. I didn't put them on my 73 conversion at first, but when I did, the oil temp dropped.

Interesting....I have the flaps but no mounting holes. I'll have to look at fitting them again.

Part Number??? Did not see it on PET

Not sure but I think they are NLA

There is a set for sale on ebay

If all you want is the functionality it would be easy to make a set from something other than plastic.

Can we have the link please?



Aluminium perhaps? Will go that way if I cant find a set.
Would appreciate if someone would provide dimensions...

My head temp went down almost 20 degrees on the freeway after adding these.

You would have to put some kind of hinge and return spring if made out of aluminum. They were made to be flexible for a very obvious reason.

They are installed 385mm apart (15.5") to the tip of the wide bottom part or 7 3/4" from the centerline of the car.

Why not make these out of plastic? It wouldn't be too hard to extrude a profile similar (but slightly thicker). As these Have the XXX on the back of them to add reinforcement. If there's enough interest I could do these. I'ld guess about $15 a set. As far as aluminum, I could do that pretty easily on the brake, but I think it'ld get boogered up, and If you back over something it would be less forgiving than the plastic.

No good reason not to make them out of plastic... if you can extrude a similar profile in plastic. Most of us don't have that ability in our garages. Sounds like a new product opportunity Mark!

Would it make a difference if the air foil went all the way across the bottom , or would this hurt more than help ?? Just curious since the idea of the foil is to create a low preasure area under the engine to help scavenge the air coming in from the top through the fan blowing over the cylinders ??.....Just a thought

Jaxdream

Just looking at the design I would say there is a reason they do not go all the way across. Besides the flaps creating a lo pressure area beneath the cylinders, that gap between them is a "venturi" so to speak, increases the speed air moving through creating it's own "suction" to draw away expelled hot air to the center line of the car.

Hey, after two cups of coffee I can come up with all sorts of things.

I'm just working on my second cup . Ok , the venturi effect , wouldn't it increase the velocity of the air moving underneath ?? when the idea was to create a lower preasure area , or was it just for the ,let's say alleys of air in the general vicinity of the two paths ??

Jaxdream

Lo pressure behind the flaps ... higher speed air thru the center would also create a suction effect on the pool of hot air behind the flaps to take the hot air away.

Next!

If I extrude the same profile, we could play with how they're cut, but my first thought is to make it pretty close to the same shape, they spent a bunch of effort to make these the way they did. I know that they were a molded part instead of extruded, they may have done this as it was cheaper for them in large quantity. I know there was someone that was modeling aerodynamics for the 914, I would be curious to see if this was addressed, I know there was allot of conversation about tails, and some body effects. Anyone remember who that was?

I f there is enough interest and I do make these, it would be nice to see if we could tweak it to make it even more efficient.

and slits is correct the air has to move faster to get over the top creating a low pressure behind (venturi effect).

Sounds like we need some wind tunnel testing.

Ron might volunteer for that task too. A can of beans and him in a garage should work.

Dave

Might be tough to turn that 'wind' off once it gets going. Better have an exit strategy.

Soon there will not be anything that Mark does not make for a 914!



Yeah, watch out for Ron's windtunnel...keep away from an open flame!

Shouldn't that be an exhaust strategy ??

Jaxdream

Couldn't you use a diffuser method to achieve the same result?

I made a set from AL duct stuff from the hardware store and tin snips, easy as pie, only downside was they were sharp! Cut myself twice on them while under the car.

Ferg