944 Wind Tunnel Testing
10-07-2012, 05:42 AM
#61
Three Wheelin'
i'm no expert in thermal management or aerodynamics but IMO the red car has some good and some bad things.
The bad thing is that the radiator is completely exposed..i think thats a cheap and bad way to fix a thermal management problem. I think that what they've gained by deleting the turn signals, the fog lights and the lower grill they've spent or even overspent on opening the mid section for the radiator like that.
It seems that they have about 50% intercooler exposure and 90% radiator exposure...why did they go with this i dont understand.
I think that nose panel openings like that or the ones the factory made are not that bad for aero for these cars. They are in a higher pressure area but not near the max pressure areas. So they will suck in some air and wont create much drag, especially if you give the air a chance to exit in a lower pressure zone
Its hard to see from that picture but it seems that the hood openings are much closer to the headlight compared to your car...i think thats a good thing. From experiments a lowered 944 front end like theirs or yours creates a low pressure zone starting at approx 100mm after the headlights...thats a very good spot to have the air from the intercooler exit
The bad thing is that the radiator is completely exposed..i think thats a cheap and bad way to fix a thermal management problem. I think that what they've gained by deleting the turn signals, the fog lights and the lower grill they've spent or even overspent on opening the mid section for the radiator like that.
It seems that they have about 50% intercooler exposure and 90% radiator exposure...why did they go with this i dont understand.
I think that nose panel openings like that or the ones the factory made are not that bad for aero for these cars. They are in a higher pressure area but not near the max pressure areas. So they will suck in some air and wont create much drag, especially if you give the air a chance to exit in a lower pressure zone
Its hard to see from that picture but it seems that the hood openings are much closer to the headlight compared to your car...i think thats a good thing. From experiments a lowered 944 front end like theirs or yours creates a low pressure zone starting at approx 100mm after the headlights...thats a very good spot to have the air from the intercooler exit
10-08-2012, 09:15 AM
#62
Rennlist Member
I've been thinking about this thread, and from a racing point of view, what really matters isn't the top speed, be it 120, 130 or 150 MPH... those are all achieved on the straight where downforce isn't going to do anything for you. What we really want is downforce while cornering - this will give us more grip, and more grip will allow us to go faster through the turns.
Corners are also always slower than straights... so, exactly what speeds are we talking about? I just did some analysis on recent data from Summit Point, Lime Rock, Mosport and Watkins Glen.
The speeds where I want more grip are really 45 - 95 MPH.
In the charts below, I wrote a formula to calculate my actual speed (via GPS, not indicated on the speedometer) when the car is at a cornering force of over 0.5 Gs. When the cornering force is less than half a G (when I'm going pretty straight), that data is omitted. This focuses on speed while cornering only.
A histogram shows a bar chart and it lumps speed ranges in "buckets" and then displays those buckets as a percent of the total lap time. On overage, about 1/2 of each lap is spent at cornering at 0.5 G or more.
Corners are also always slower than straights... so, exactly what speeds are we talking about? I just did some analysis on recent data from Summit Point, Lime Rock, Mosport and Watkins Glen.
The speeds where I want more grip are really 45 - 95 MPH.
In the charts below, I wrote a formula to calculate my actual speed (via GPS, not indicated on the speedometer) when the car is at a cornering force of over 0.5 Gs. When the cornering force is less than half a G (when I'm going pretty straight), that data is omitted. This focuses on speed while cornering only.
A histogram shows a bar chart and it lumps speed ranges in "buckets" and then displays those buckets as a percent of the total lap time. On overage, about 1/2 of each lap is spent at cornering at 0.5 G or more.
10-08-2012, 01:35 PM
#63
Rennlist Member
Well, of course you WANT down force in the corners, but with a 944 NA and a 123 rwhp, you cannot afford to give up any power to generating down force. You would be better served by concentrating on reducing drag. This would help around the whole circuit, not just on the straight-a-ways.
Unless you are Adrian Newey and know how to generate down force without losing power, you'd be better off finding ways to get through the air better.
Unless you are Adrian Newey and know how to generate down force without losing power, you'd be better off finding ways to get through the air better.
10-08-2012, 03:07 PM
#64
Rennlist Member
Well, of course you WANT down force in the corners, but with a 944 NA and a 123 rwhp, you cannot afford to give up any power to generating down force. You would be better served by concentrating on reducing drag. This would help around the whole circuit, not just on the straight-a-ways.
Unless you are Adrian Newey and know how to generate down force without losing power, you'd be better off finding ways to get through the air better.
Unless you are Adrian Newey and know how to generate down force without losing power, you'd be better off finding ways to get through the air better.
10-08-2012, 09:43 PM
#65
Herr Unmöglich
Rennlist Member
Rennlist Member
Funny you mention mirrors Van. Our rules locally say mirrors are free, so I am going to pull both and rely only on the interior rearview and a convex mirror on the driver's A-pillar. This takes both out of the wind and reduces weight at the same time. My passenger glass fell out this year and it seems stupid to buy a new one when I never use it.
I'd love to find a set of the later Cup teardrop mirrors but since they are unobtanium and I barely use external mirrors anyway, this is the next best deal.
From my Traqmate data, at several different tracks I top out at 121.x MPH (Spokane, Seattle, Portland), so it's a power/aero drag issue. The downforce at lower speeds just isn't happening, so I'd prefer minimum drag for max acceleration and top speed whenever needed.
Next up, find someone to make a cheap run of 15x7 wheels for SCCA-legal track use. Cookies are getting hard to find in straight sets.
I'd love to find a set of the later Cup teardrop mirrors but since they are unobtanium and I barely use external mirrors anyway, this is the next best deal.
From my Traqmate data, at several different tracks I top out at 121.x MPH (Spokane, Seattle, Portland), so it's a power/aero drag issue. The downforce at lower speeds just isn't happening, so I'd prefer minimum drag for max acceleration and top speed whenever needed.
Next up, find someone to make a cheap run of 15x7 wheels for SCCA-legal track use. Cookies are getting hard to find in straight sets.
10-08-2012, 11:16 PM
#66
Rennlist Member
10-09-2012, 03:46 AM
#67
Rennlist Member
Van this concurs with the winner of a recent high profile Time Attack event down here. The car, an extremely modified Evo, had massive downforce. They were quoting F1 levels. You could see it hit a wall down the straight...by that I mean an aero/drag wall. I don't think it was any faster than Sean's 3L 951 in a straight-line, but around the corners it was like a slot car. Where a fast Cup car will do 1.31 on slicks, this car did a 1:25 flat on R spec rubber!! Super soft Yokohama A050's which last about 1 lap but still very impressive.
https://www.google.com.au/search?q=n...w=1920&bih=955
https://www.google.com.au/search?q=n...w=1920&bih=955
https://www.google.com.au/search?q=n...w=1920&bih=955
https://www.google.com.au/search?q=n...w=1920&bih=955
10-09-2012, 07:54 AM
#68
10-09-2012, 10:21 AM
#69
Rennlist Member
10-09-2012, 01:41 PM
#70
Racer
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Jeff
10-09-2012, 04:38 PM
#71
Three Wheelin'
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Quote:
Originally Posted by 333pg333
Yes, and others have said this. But this was also what the factory did with the stock intercooler. Not with a much larger front mounted version. From what you're saying, it would seem that you're discussing the differences of making the opening smaller, not larger ?
Originally Posted by 333pg333
Yes, and others have said this. But this was also what the factory did with the stock intercooler. Not with a much larger front mounted version. From what you're saying, it would seem that you're discussing the differences of making the opening smaller, not larger ?
Picture shows the bottom and sides of the ducting. The top is removed for the picture. I didn't restrict my grill opening purely for asthetics.
10-09-2012, 04:46 PM
#72
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