Kahdmus

In driving around town, the spoiler can seemingly be going up and down like a yo-yo. I remember a post by garrett where he talks about keeping a careful eye on the speedometer to ensure the spoiler was not deployed to save on the constant up-and-down - I can relate to this!

Andy Roe

..but, isn't the spoiler supposed to go up at ~50mph to also aid cooling, as well as handling?

garrett376

Hi guys - I did this for two reasons. The main reason is exactly what Howard said - my drive to the office in the morning is only about 8 minutes, during which I hit about 10-15 stop lights all with 35-45 mph speed limits. If I drove as fast as everyone else, I'd be doing about 50 from one light to another - I bet that the spoiler will be going up and down about 10 times before I get to my destination! I doubt there is any aerodynamic advantage, or cooling advantage in this type of situation!

Even then, considering how aerodynamic stuff usually works, the spoiler on the rear of the 964 likely does very little for the car's handling when speeds are below 80mph. For that reason, in my usual driving (which is almost always below that speed) I'd rather just keep it down until I go on the freeway and go faster than 50-60mph. The freeways here require absolutely zero handling capabilities ( given that three cylinder Geo Metros go about 80mph on their bike tires without crashing! ), so the rear wing likely does zero for me on the freeway, even if I'm going 100mph!! Plus, traffic is always so bad that the flow of traffic goes from 0-70mph-0 every couple miles! Again the spoiler isn't helping much but shortening the life of the motor and spoiler wall - which I need to replace on the cabrio because it broke recently!

Now the second reason I wanted to do this was for my coupe which I race. The spoiler was actually working intermittently in this car - it would come up at speed sometimes, and not others. The control unit would click all the time when driving on the freeway which was annoying - it no longer does this now that the speed input is removed! The function of the spoiler is just something I don't want to worry about because when I'm racing I want the spoiler up the whole time - and some times it is up, sometimes it won't go up and the warning light would appear and I have to raise it manually, cancel the Central Warning, all while trying to get in the right spot on the pace lap!!

Now it works just how I want - I'm in control of it!!!

garrett376

Hi Andy,
My car's oil temp has never varied on my street driven C4 whether the lid is up or down - have you noticed any difference? Then again, I live in a very temperate area - always around 60-70 degrees here. I am not sure if there is any evidence that cooling is improved - after all, if the engine needs more air to cool itself at high running speeds, it will be sucking it harder due to the fan at higher RPM. I don't know if the raised spoiler would truly force air into opening in the decklid, and that forced air would then be forced into the fan shroud where it will increase cooling. That's the only way I can see it would help, other than there being less resistance to airflow by moving the spoiler grille out of the way so more air can be fed in more easily, but it seems the fan itself will pull as much air as it can, regardless if it's "force-fed" from the decklid.

My feeling is that the spoiler does more to reduce rear end lift at really high speeds, than to increase cooling. But that's just a feeling! And if I lived in a really hot place, things might be different! What do you guys think?

leosayer

Just one thought, not sure if it applies. If you were involved in an accident, the investigators may focus on the fact that your spoiler wasn't working.

Christer

I think regardless of whether you drive only below 80mph, do drag racing between traffic lights or just want to have something different I personally feel that this sort of thing is not worth worrying about. If you did forget to raise the spoiler just once when you needed it then the mod is just not worth it to save a little on the 'up/down mechanism'. If I really had got to the stage where I could think about nothing except the poor mechanism then I would do the RUF mod as I am sure I would forget to raise occasionally.....

DarrylH

Would it make sense just to raise the spoiler at the beginning of your commute, and just leave it up until you reach your destination? That would be just one up / down cycle per trip. Any additional cooling, even if negligible, can't hurt, and there's no fear of forgetting. I've often thought the default behaviour of the spoiler ought to be "up once moving, then not down until key off" but maybe I'm just nuts.

Smokin

How about a fixed spoiler!?

Marc Shaw

Garrett - your rationale makes sense in your situation - I hope you did not think I thought it was a waste of time or just a mod for the sake of "let's see if it can be done"

The point of the electrically activated spoiler though was in response to marketing concerns that Porsche wanted to move away from the extroverted Whale-tail of the 80's with the stock-brokers in their yellow "power ties" and those who bought the cars as a a status symbol, not as true enthusiasts.

If you don't crave the clean look of the spoiler-less back end (and don't want to get airborne at high speed due to inadequate rear downforce like early Audi TT's), then why not just go to a fixed spoiler as has been suggested?

Marc

Cupcar

An added benefit of changing to a fixed spoiler is potentially less lift at the rear with a larger spoiler.

Reading Frere's aerodynamic data on the 911, I find:

On "A" type body 65-73

No Spoilers
Front lift=183 pounds
Rear lift=255 pounds

Front Spoiler Lip + Ducktail Rear Spoiler
Front lift= 77.3 pounds
Rear lift= 93 pounds

On "G" type body 74-89

Front Spoiler Lip + "Tray" Type Rear Spoiler
Front lift= ~11 pounds
Rear Lifft= ~36.5 pounds

I suspect that the stock 964 spoiler is like the Ducktail and the RSA spoiler is like the tray so a similar comparison could be drawn between them and installing an RSA type fixed spoiler would reduce lift.

garrett376

I prefer the spoiler-less appearance, actually! Probably because I had my 65 911 for so long and prefer the old style shape.

I must admit, that today driving to the office, I didn't have to look down once to be sure I was staying under 49mph to keep the spoiler in! Loved it!

Although now I am more likely to get a speeding ticket!

garrett376

It's not that I was primarily worried about the mechanism - I'd just rather control the spoiler myself! Now I can!

I don't know if I would ever need the spoiler on my drive to work - afterall, in a convertible 911, aren't the aerodynamics gone to crap when the top is down anyways?! I can raise my hand out the roof and maybe do a better job!

Marc Shaw

Garrett - did you ever just wire this up to a dashboard switch?

I was considering doing this and putting a dash switch where the headlight raise switch is supposed to go to allow making the spoiler speed or no-speed acitvated.

Marc

garrett376

Hi Marc, I found that I prefer to have the spoiler work ONLY via the switch, not speed mediated. In order to switch between speed, or no-speed activated, all you would need to do is buy a 4-pole switch that bridges two circuits and simply solder in a "bypass" wire for each of the two wires that I have un-done as described above. You will just need to cut the wires, splice in your long wires to the dash switch. Then you could hit the switch to deactivate the speed sensing ability of the spoiler, or switch it back to turn it back to normal. Very sneaky that would be!

Marc Shaw

That is exactly what I was thinking of doing - so with a 1991 like mine, the control unit is likely under the passenger seat, yes?

Thanks...........Marc