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914World.com _ The Paddock _ At what speed is aero a good idea?
Posted by: Jetsetsurfshop Oct 3 2016, 06:12 PM
Hey Paddock People,
My car sustained some pretty good front end damaged and the 916 front bumper is destroyed. Thinking this is a good time to change things up. Good news is that already bought the bumper half with the oil cooler cut out. Now I need the bottom half to finish it off.
The thought is should I run a splitter type valance? What is the speed where these cars want downforce? My car's top speed at Sebring is 115mph. I see a lot of HSR 914-6's that don't have a splitter and I know there are faster then I am.
Another thought is that I'm not the only driver of the car and when we have an off track experience, will the splitter still be there??
Posted by: Cracker Oct 3 2016, 07:53 PM
You don't need a splitter...it would mainly just slow you down.
Tony
Posted by: wndsrfr Oct 3 2016, 08:12 PM
My /6 gets to about 130 at VIR & WG, almost 125 at Sebring. Here's the original front valance & the car did get dodgy above about 120 sometimes.
I went with Roger Sheridan's front spoiler, listed as the "Performance Spoiler" from Automotion (no affiliation)--http://www.automotion.com/performance-spoiler-with-brake-duct-openings-for-914-porsche-1970-1976.html
--It helped settle the car--actually topped 150 at Daytona with good stability, so I can definitely recommend it.
Posted by: Cracker Oct 4 2016, 08:30 AM
John - An airdam I'm not against for Shane's application and speed. I use the same airdam myself but I thought he was talking about an actual splitter. Here is a pic of my car with the same Airdam you pictured but with a 4" splitter. This slows my car down...thus my advice. The "tipping point", speed wise, to answer your question would be at about 130 mph; based upon my on-track experience. I actually lost my splitter in June and the car drove (pushed like Hell) but that was over 160. In summary - airdam would be ok.
Tony
Posted by: ThePaintedMan Oct 4 2016, 08:48 AM
I really like that spoiler that John and Tony have too. I've considered it for my car too, once I ever get it over 100 mph, lol. I wouldn't go much more though for Chumpcar, as the off track excursions just happen too frequently and the resulting damage can be far worse with too low of a spoiler. When I went mowing out in the 15-16 complex at Sebring with mine (an LE air dam) I was sure I tore that thing off. But apparently not. I think with something much lower though it would have definitely caught the grass/concrete transition.
https://www.youtube.com/watch?v=W0jrz7WjIxU
Posted by: campbellcj Oct 4 2016, 08:56 AM
I have that Sheridan spoiler as well and it's a great choice. Agree these cars get sketchy somewhere around 115-125 and mine gears-out around 133-135; for me, it was turn 8 at WSIR that got me thinking about at least a ducktail rear spoiler as well. So I have Roger's front and rear.
Note I found a significant reduction in brake cooling with this deep spoiler without hooking up cooling ducts so be cautious there. In fact a few times I switched back to a shallower one for this reason (also high curbs and ruts are an issue at some tracks). This month I'm going to try a true duct setup I never finished installing and it should solve that.
Posted by: Cracker Oct 4 2016, 09:16 AM
So Chris - You are running without cooling ducts to your rotors? Wow. Mine would die an early death if I did that (if I understand you correctly).
...and good save George.
T
Posted by: campbellcj Oct 4 2016, 10:04 AM
So Chris - You are running without cooling ducts to your rotors? Wow. Mine would die an early death if I did that (if I understand you correctly).
...and good save George.
T
Yes I have been - but not with that deep spoiler at most tracks. It has pretty beefy brakes for a 914, vented rotors F+R and pagid pads and a partial Smart Racing cooling setup, just not plumbed to the front spoiler yet. That should be a huge improvement but I still won't use this spoiler everywhere due to ground clearance.
Posted by: Cracker Oct 4 2016, 10:19 AM
Ok. It can be hard to keep the duct hose on the provision on the GT spoiler...I have two CF units that I have not instaled as of yet and had them make the snout 2" longer than normal because of this. Another idea which is done on my car is to use a pvc middle coupler. It is penetrated by te A-arm but allows the duct a hard point fore and aft, to connect to. Although it is a little unorthodox, it has proven to work very well. In the picture below you can see it if you look past the brakes. Best of luck.
PS: Chris - Ground clearance isn't any issue so long as you don't leave the track! 
Tony
Posted by: brant Oct 4 2016, 12:13 PM
sorry if this is getting off topic (spoilers)
but just another data point for brake temps.
lots of variables
so mine are:
stock valance, not a low spoiler
less weight than some cars
much less speed... 125 is probably all I hit on short-ish tracks
vented front 911 rotors, KFP carbon pads
I ran temperature paint on my brakes front and rear
I found that my front brakes with the smart scoops, and hub block off plate were running too cool for the operating range of my front brake pads
I had multiple conversations with the engineers at KFP
they verified all of my data, and also thought my pad compound choice was wrong
I re tested after removing the air ducts (smart scoops... not true air ducts to a front spoiler) Still too cool for operating range
Next I softened my front torsion bars from 22mm to 21mm in hopes of more weight transfer and better brake temperatures as a result. Still too cool for operating range
next I went up one grade of pad compound to a softer pad, for lighter cars
still too cool for operating range
finally I went up a second grade of pad compound for yet softer pads
Now I'm in the operating range
my rears are solid rotors and still run much hotter than the fronts
but I'm in the operating range and my brakes are better than they were both by seat of the pants, and also by traqmate data. I am convinced that I still have a tiny bit too much cooling, but am already running the softest pad made for my "S" caliper in the KFP brand. (I really have had great results running KFP's for 20 years)
granted I'm running a 2.0 motor
I'm not running Tony's kind of HP!
but you can have too much brake cooling also guys
brant
Posted by: Cracker Oct 4 2016, 02:51 PM
Brant - So true. I've had to block off the brake ducts on my old Vette because I wasn't getting enough heat in the pads. Ultimately, a driver will know if they are over-heating their brakes (pad wear, fade, warped rotors, etc, etc.). Good info to share - thanks!
Tony
Posted by: brant Oct 4 2016, 06:13 PM
At my speeds I have too much brake
I'm running the same rotors for 11 seasons. KFP pads are nice to rotors.....
heck all they do is slow you down
Posted by: ThePaintedMan Oct 4 2016, 06:29 PM
That's awesome information Brant. I've found the same thing with Porterfields - really kind to rotors and I'm running the absolute lowest heat pads they have, which are the Vintage compound. Not like Hawks - those pads, even their street compounds just chew up rotors on everything I've ever seen them on.
Question - what are smart scoops? Got any pictures? 
Posted by: Cracker Oct 4 2016, 06:37 PM
LOL. Add 400 hp and go to a big track with huge speed - you'll need the brakes! At Road America, my car should see 170+ at three different places - each time around. 
11 years on the same rotors!!!!!!! Crazy Brant.
Tony
At my speeds I have too much brake
I'm running the same rotors for 11 seasons. KFP pads are nice to rotors.....
heck all they do is slow you down
Posted by: Jetsetsurfshop Oct 4 2016, 06:55 PM
I took a day off from checking this post and you all took it over!
The tipping point was what I was after. I don't feel my car needs a splitter/wing combo yet. Was looking for what you all thought was the speed when a 914 gets squirrelly.
I think I'll just do the valance like Brant's. Chumpcars do have an occasional off here and there. An air damn splitter combo sounds like a problem waiting to happen.
As far as Brant's off topic post. I never thought my brakes were too cool. Never experienced brake fade in my car after I went 5 lug. I was running Hawk DTC-70s and we never got the rotors hot enough for those. Now I have Porterfields endurance pads because we didn't want to swap pads during a race. Not sure if those are in the optimum temps, but I think I like these more. Stopping didn't fill drastically different form one to the other and there kinder to the rotors.
Thanks for the help.
Anyone have a suggestion on how to buy the valance from?
Posted by: brant Oct 5 2016, 10:28 AM
I took a day off from checking this post and you all took it over!
The tipping point was what I was after. I don't feel my car needs a splitter/wing combo yet. Was looking for what you all thought was the speed when a 914 gets squirrelly.
I think I'll just do the valance like Brant's. Chumpcars do have an occasional off here and there. An air damn splitter combo sounds like a problem waiting to happen.
As far as Brant's off topic post. I never thought my brakes were too cool. Never experienced brake fade in my car after I went 5 lug. I was running Hawk DTC-70s and we never got the rotors hot enough for those. Now I have Porterfields endurance pads because we didn't want to swap pads during a race. Not sure if those are in the optimum temps, but I think I like these more. Stopping didn't fill drastically different form one to the other and there kinder to the rotors.
Thanks for the help.
Anyone have a suggestion on how to buy the valance from?
Shane,
Regarding the valance
they have probably gotten more pricey than they used to be (like all of these parts)
back when I was building the vintage car in 03-04, it wasn't cost effective to go fiberglass given that the weight savings was minimal. I used a formula at the time to calculate how many pounds would be saved at what cost. The fiberglass valance isn't a ton lighter. I don't remember any more how much... but it was only a few pounds at the time and didn't past my $/lb formula
of course it might be more cost effective now
the valances are still not expensive but if you have to ship one that will add a bit
I think the usual sources, GT, etc all have the Fiberglass ones
every now and then I will have an off or ding my metal one and appreciate that I can pull it out (often without removing it from the car) and don't have to do any fiberglass work on it when that happens.
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