I've done some testing, but would like input on the 'tuning' part
01-07-2013, 04:59 PM
#31
Rennlist Member
Jack,
I remember when you were working with the rear diffuser and had some good/bad results with it. I actually did similar work over the summer, but took a different approach to the back. You really need a smooth bottom to the entire chassis to get good results from a diffuser and the most important function is for it return airflow to the same velocity as the air around it on exit. This avoids big disturbances of the rear attached flow. I started with the front and integrated the bottom panel into the front splitter then continued to the rear (3 sections totals). The under-tray removes from each section in a couple of minutes by using inserts a flush underside allen bolts. I made the bottom exit much more gradual using accepted minimal angles and also made it adjustable from 0 to 15 degrees. I followed guidelines from a bit of race car aero articles centered around GT cars. Air-cooled cars are a concern of course so you also need some deflectors and or removable vents depending on operating temperatures.
I remember when you were working with the rear diffuser and had some good/bad results with it. I actually did similar work over the summer, but took a different approach to the back. You really need a smooth bottom to the entire chassis to get good results from a diffuser and the most important function is for it return airflow to the same velocity as the air around it on exit. This avoids big disturbances of the rear attached flow. I started with the front and integrated the bottom panel into the front splitter then continued to the rear (3 sections totals). The under-tray removes from each section in a couple of minutes by using inserts a flush underside allen bolts. I made the bottom exit much more gradual using accepted minimal angles and also made it adjustable from 0 to 15 degrees. I followed guidelines from a bit of race car aero articles centered around GT cars. Air-cooled cars are a concern of course so you also need some deflectors and or removable vents depending on operating temperatures.
01-08-2013, 10:43 PM
#32
Former Vendor
Original post said start off at 6 lbs less pressure in front...seems backwards if the rears are getting hotter THAN the fronts? In other words, the fronts ought to start off with MORE pressure...unless I am missing something? Seems like you'd end up with the fronts WAY higher than the rears -
01-08-2013, 11:05 PM
#33
If the rear tires are getting hotter than the fronts, less air in the fronts will get them hotter. They will get hotter faster with less pressure. More tire flex means more heat.....
Scott
Scott
01-09-2013, 05:38 PM
#34
Race Car
Thread Starter
bobt993, I've got a smooth undercarriage from the nose to the rear swaybar. The problem I had with the rear diffuser (and engine cover) was that it gave me lots of help in a straight line -- where I didn't need it -- and then became unpredictable in corners, since even with 600# springs the car had enough body roll to change the relationship between the diffuser and the track.
At least, that's what I concluded. Maybe more testing and tweaking would have proved its worth. But I was worried about cylinder head temps becoming dangerous with all of the restriction I was putting in and didn't want to cook my engine. The pieces were also a pain in the neck to put on and take off -- one of the downsides to trying to have it both ways with a street/track car.
At least, that's what I concluded. Maybe more testing and tweaking would have proved its worth. But I was worried about cylinder head temps becoming dangerous with all of the restriction I was putting in and didn't want to cook my engine. The pieces were also a pain in the neck to put on and take off -- one of the downsides to trying to have it both ways with a street/track car.
01-10-2013, 01:28 PM
#35
Three Wheelin'
You are welcome. I figured you already knew Cayr E., or maybe I just remembered from some past interactions and/or thread(s). And of course I know that Tyson did the work. I know Tyson but I have not seen him for a while. So say hello to him.
That underscores my point about the platform. All of this and yet you feel that there is another 3 seconds, based only on tweaking what you have (no different parts or tires), and no driver improvement. In my experience, that is a lot of time given those constants. A lot.
I might try to zero in on what the real number is... is it really 3 seconds? Do Cary and Tyson and other experts agree that you can tweak a few things and get there? Again, assuming no parts or tire changes and no driver work.
I might also check my notes to see if I wandered in a non-productive way from where I started with set-up. I have seen a well-known Spec 911 racer chase his tail a bit in this way. I am sure part of it was fun, and part of it was frustrating.
What I have found in the last 25 years is that experts can get many of these old 911 car configs. to within a second or two of max pretty easily. I am pretty familiar with your car and to me there is nothing too out of the ordinary about it. It is harder with newer cars (IMHO) because there are more pots to tweak.
I have also seen that drivers plateau pretty easily, especially when they are not competing. Racing is a form of competition that can help. But also time trial driving. Sometimes these activities help you identify small tweaks that allow the driver to better operate the platform to its max. So the "solutions" are more of an amalgam of car and driver as opposed to just a tad more rake or tire pressure.
Of course none of that should stop you from tweaking.
Just throw some good slicks on and I think you will see your times improve.
Or do some simple data acq. with a good coach for benchmarking and the same might be true.
That underscores my point about the platform. All of this and yet you feel that there is another 3 seconds, based only on tweaking what you have (no different parts or tires), and no driver improvement. In my experience, that is a lot of time given those constants. A lot.
I might try to zero in on what the real number is... is it really 3 seconds? Do Cary and Tyson and other experts agree that you can tweak a few things and get there? Again, assuming no parts or tire changes and no driver work.
I might also check my notes to see if I wandered in a non-productive way from where I started with set-up. I have seen a well-known Spec 911 racer chase his tail a bit in this way. I am sure part of it was fun, and part of it was frustrating.
What I have found in the last 25 years is that experts can get many of these old 911 car configs. to within a second or two of max pretty easily. I am pretty familiar with your car and to me there is nothing too out of the ordinary about it. It is harder with newer cars (IMHO) because there are more pots to tweak.
I have also seen that drivers plateau pretty easily, especially when they are not competing. Racing is a form of competition that can help. But also time trial driving. Sometimes these activities help you identify small tweaks that allow the driver to better operate the platform to its max. So the "solutions" are more of an amalgam of car and driver as opposed to just a tad more rake or tire pressure.
Of course none of that should stop you from tweaking.
Just throw some good slicks on and I think you will see your times improve.
Or do some simple data acq. with a good coach for benchmarking and the same might be true.
Last edited by Mahler9th; 01-11-2013 at 04:59 PM.
01-11-2013, 01:31 AM
#36
Race Car
Thread Starter
I wasn't clear enough in what I wrote. I think the car's got a 1:24 in it with stickier tires. But I'd hate to spend a bunch of money on a set of A6s and still be leaving something on the table like rake, or other cheap aero mods I can do, or that sort of thing.
In my mind, if I can get one more second out of more driver focus and maybe some cheap car mods, then Hoosiers might conceivably give me another couple of seconds at this track. I could be wrong about that. But the Puhn book came today, so I'm going to jump into that.
In my mind, if I can get one more second out of more driver focus and maybe some cheap car mods, then Hoosiers might conceivably give me another couple of seconds at this track. I could be wrong about that. But the Puhn book came today, so I'm going to jump into that.
01-26-2013, 11:24 AM
#38
Race Car
Thread Starter
Thanks, Matt!
I was worried I'd come across as a jackass when they edited it all together, but I like it a lot.
Something for my kids to see one day.
I was worried I'd come across as a jackass when they edited it all together, but I like it a lot.
Something for my kids to see one day.
01-26-2013, 02:12 PM
#39
Rennlist Member
^^^^ Actually Jack I think you did some good PR towards the image of Porsche owners. I hope my wife does not see the garage picts because I will have a ton of work to do on mine.
