Mo Mia

Hi Guys,

Hoping someone could help on possibly a silly question. My 1979 930t has got slats on the front end of the rear fenders allowing air to flow through. I was told that this was some 400HP body conversion. My confusion is that the air that goes through the slats is not guided to anywhere specific when inside the fender. Is this how it is supposed to be or should there be some type of piping to the calipers or engine bay thus having more directed improved cooling preferably in the engine area?

thanks and cheers
Mo

911rudy

Mo,
Usually this conversion is for rear brake cooling and not for engine cooling. It sounds like your car was converted for looks rather than true cooling. I am putting the vents on my 930 and they came with air ducts that direct the air flow to the rear brake rotors. I'll try to add a picture for you. Sorry, I could not get the attachment button to function. I'll try again later.

Geoffrey

"Usually this conversion is for rear brake cooling and not for engine cooling."

Actually that is incorrect. On the US factory 911 Slant nose conversions there is not enough room for the fender mounted oil cooler. It is moved to the right side rear, directly behind the "slats" which are used to direct cooling through the cooler. The Euro cars have an additional cooler in the front under the 930S front spoiler that we did not get. The left side goes to nothing.

kens911

It's my understading though that with the fender vents they do tend to run cooler, and I believe the euro version did not have a back oil cooler in the vent just the one up front in the spoiler. I have a friend that ran a 930 at the track a lot and he said it ran much cooler after he put in the vents. when he got rid of it and started running another 930 this time he used the later model rockers with the brake holes in them instead of cutting and welding in the fender vents, this helps also acording to him.

911rudy

I know the right side had an oil cooler in it but the ducting takes the air directly to the slots int the edge of the rotor. I don't see how anyone could say that they were there for show or oil cooling only. The duct is almost exactly the same width as the rotoe and is only inches from it, and it is obviously designed to match up with the rotor. In many offical articles by Porsche, they are refered to as rear brake cooling vents.

kens911

yes they are for cooling the brakes but it also lowers the temp around the rest of the back of the car

Mo Mia

Thanks for all your responces guys. Much appreciated. Rudy, my vents / slats look pretty much like your pic.

My reason for enquiring was becuase I feel i need more engine cooling. I originally had the trambone cooling system in front right fender. With increased track time this was insufficient so I replaced this with a front mounted oil cooler. This allows me approx 20 min track time befor she is close to red temp line. Is this normal? I'd like to stay out longer so was looking to see how I can improve the cooling. Any ideas?
Cheers
Mo

jetskied

It is normal for them to run hot with that trabone cooler. Not to say its good for the engine. You do need to consider to change your cooler to a radiator type such as the one B&B sells, but being under the front fender it may still not get enough air for track work. There are some devices that removes the right front signal light that gets more air, but I don't know how it works. Performance prodcut sell these scoops. Your best bet is a front oil cooler with a 930S style or Ruf front spoiler. The down side is the cost of the cooler and the new spoiler. I have used a front cooler and it never gets above 220F averages about 190F. I would have to say if you're running hot with a front cooler you may have a problem with the thermostat that lets oil go to the front or your engine is mistuned. If the timing is off or the fuel mixture is too lean will cause the engine to run hot. I would talk to your mechanic.

911rudy

I was under the old girl today and decided to take a few pics and one of them is the right rear fender vent from inside the wheel well. I took it ridectly over the top of the rotor so you can see that the air flow is right into the slots. There had been some comments that indicated that the vents did not cool the brakes but as you can see thats what they are designed to do. Also included is the altered turbo bracket that takes the weight and stress off of the header flange. I tack welded it with the wire gun and then TIG welded it and painted it with bar-b-que heat paint. And lastly I had to fix my shop because my wife said it looke like hell and she wanted it to look nice. I got these neat vinyl tiles which are really four squares on one big tile for 96 cents a square foot at Lowes. They are self stick and are real easy to clean up. Maybe I'll get lucky tonight!

SoCal Mike

Rudy, doesn't the wheel/tire cover the rotor vents. I'm sure the vents help to bring lots of fresh air into the area but the slantnoses with right rear oil coolers seem to benefit the most from this set-up.

TrackDays247.com

Keep in mind that the brake rotors are cooled radially; ie the air starts from the center section of the rotor and radiates outward through the center of the rotor and out the edge via the vanes -

kens911

and the vent blows that heat out of the fenderwell

TrackDays247.com

It'll help a tiny bit, but to be honest......it is mainly for looks.