let's talk downforce
#31
Rennlist Member
Actually, the downforce would only compress the springs ever so slightly (you know how much the car moves down with 200lbs in the trunk) it's like weight , without the weight. actually, there is some damping that happens with only aero down force as well.... the spring rate stays the same unless you have progressive springs, but the downforce will not really exacerbate your soft springs unless you are hitting the bump stops, which won really happen just with a wing. actually, it will make thigns a little better. But yes, the right thing to do is upgrade it all if you can
#32
Addict
Rennlist Member
Rennlist Member
More specifically, I'm looking for more down force to help settle the car better over bumpy straights (T1->T2 at Palmer), more aero to help take fast corners with more speed/throttle (T2 @ Palmer, T2&T10 @WGI, Downhill @LRP etc.) and more grip on initial braking on long straights.
Last edited by Jake951; 10-08-2016 at 03:26 PM.
#33
Rennlist Member
I may already have a buyer, but I will be selling my used jrz rs pro shock package in a month or so. I'm converting my 06 cs to spec cayman which needs a different package. PM me if you are potentially interested.
Last edited by mannym5; 10-08-2016 at 08:24 AM.
#34
Rennlist Member
I carry coils with rates that vary from 400 lbs to 1000 lbs. They are easy to change out.
#35
Rennlist Member
FYI while the rear wing may have a 10:1 L/D ratio, data typically provided is for the clean wing without a car. Total drag on the car can be quite different as the wing is not in clean air and it impacts flow all over the rear of the car, not just local to the wing. If the L/D ratio is test data from the wing installed on a reasonably similar car so be it, but otherwise I would take that number with a grain of salt and expect worse on drag.
#36
Rennlist Member
FYI while the rear wing may have a 10:1 L/D ratio, data typically provided is for the clean wing without a car. Total drag on the car can be quite different as the wing is not in clean air and it impacts flow all over the rear of the car, not just local to the wing. If the L/D ratio is test data from the wing installed on a reasonably similar car so be it, but otherwise I would take that number with a grain of salt and expect worse on drag.
#37
Rennlist Member
Erik - I don't have a Cayman (as you know) but in the GT3 I found it helps to soften the shocks a bit to deal with the bumpy straights at Palmer, especially coming into T1. You need to have some suspension compliance do cope with bumps. I have Ohlins coilovers that have fairly stiff springs (515#F/800#R) but the shocks have a wide range of adjustability. I adjust the shocks differently for each track I do (softest at NHMS, stiffest at WGI, and in between everywhere else).
And keep a notebook where you record these settings for each track, along with tire pressures, etc. Then IMO you can focus on your driving rather than constantly chasing the car...
#38
Registered User
Check out the thread "Windtunnel testing" You may get a understanding of what downforce is and can be achieved. Real testing will get you were you what with out "guessing". We have the equipment to check and set up Aero. Please note the rear wing location is not where it ended up. Also in the tunnel you can actually make the the bottom of the car turn "on" , create downforce when there was NONE. Search on the web for Full scale windtunnel testing 350Z video. I coached the team to achieve front down force when it came in it had ZERO. WE just published a paper with SAE this summer, pier reviewed. Mantissport has raced this Cayman S since 2006, PCA, PWC,NASA,CTCC,ITC.
#40
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www.peterkrause.net
www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
#41
Registered User
Hi All, here it is, 4 years of testing in the tunnel.we started of using my scale pads for the first session. I used the scale pads to show how we could get downforce numbers and effects of changes made to my PWC Cayman and SP 3 944. I could show relative numbers of change. The tunnel was not setup with flush mount 3 axis scale pads. 2-3 years of research the group, staff,students and Brion Charters, myself developed in house a system of scale pads built into the floor of the tunnel.
The tunnel now can test for downforce drag, temperature, air flow underneath the chassis, also all in yaw, right or left.
SAE paper 2016-01-1588 published 04/05/2016
Mantisspot is ready to test your car, $1,400 per hr, coaching available. We can set up in 15 minutes and do a base run. If you have all your tunable parts ready within 1-2 hrs we can get the car tuned. Now , more time is nice, but in 2 hrs we can get pretty close for a first time in the tunnel. We also have a shaker table. The pictures is clear the Cayman is going through its paces.
The paper is only part of a 85 page report we put together with all my testing of 4 cars SP2 944, SP3 944 S2 , PWC Cayman and a GTB-1 Cayman. Over 100 hrs has been devoted to the project in the tunnel time alone.
The tunnel now can test for downforce drag, temperature, air flow underneath the chassis, also all in yaw, right or left.
SAE paper 2016-01-1588 published 04/05/2016
Mantisspot is ready to test your car, $1,400 per hr, coaching available. We can set up in 15 minutes and do a base run. If you have all your tunable parts ready within 1-2 hrs we can get the car tuned. Now , more time is nice, but in 2 hrs we can get pretty close for a first time in the tunnel. We also have a shaker table. The pictures is clear the Cayman is going through its paces.
The paper is only part of a 85 page report we put together with all my testing of 4 cars SP2 944, SP3 944 S2 , PWC Cayman and a GTB-1 Cayman. Over 100 hrs has been devoted to the project in the tunnel time alone.
#42
Rennlist Member
Hi All, here it is, 4 years of testing in the tunnel.we started of using my scale pads for the first session. I used the scale pads to show how we could get downforce numbers and effects of changes made to my PWC Cayman and SP 3 944. I could show relative numbers of change. The tunnel was not setup with flush mount 3 axis scale pads. 2-3 years of research the group, staff,students and Brion Charters, myself developed in house a system of scale pads built into the floor of the tunnel.
The tunnel now can test for downforce drag, temperature, air flow underneath the chassis, also all in yaw, right or left.
SAE paper 2016-01-1588 published 04/05/2016
Mantisspot is ready to test your car, $1,400 per hr, coaching available. We can set up in 15 minutes and do a base run. If you have all your tunable parts ready within 1-2 hrs we can get the car tuned. Now , more time is nice, but in 2 hrs we can get pretty close for a first time in the tunnel. We also have a shaker table. The pictures is clear the Cayman is going through its paces.
The paper is only part of a 85 page report we put together with all my testing of 4 cars SP2 944, SP3 944 S2 , PWC Cayman and a GTB-1 Cayman. Over 100 hrs has been devoted to the project in the tunnel time alone.
The tunnel now can test for downforce drag, temperature, air flow underneath the chassis, also all in yaw, right or left.
SAE paper 2016-01-1588 published 04/05/2016
Mantisspot is ready to test your car, $1,400 per hr, coaching available. We can set up in 15 minutes and do a base run. If you have all your tunable parts ready within 1-2 hrs we can get the car tuned. Now , more time is nice, but in 2 hrs we can get pretty close for a first time in the tunnel. We also have a shaker table. The pictures is clear the Cayman is going through its paces.
The paper is only part of a 85 page report we put together with all my testing of 4 cars SP2 944, SP3 944 S2 , PWC Cayman and a GTB-1 Cayman. Over 100 hrs has been devoted to the project in the tunnel time alone.
Ive also wondered about the the effects of the "rolling road" windtunnels vs static.. that must be a pretty big factor in determining or creating underbody downforce. is there a conversion factor for not having it. I would think more would be indicated without it. true? (on coming air flow to static car and road vs rolling road and static car)
Last edited by mark kibort; 10-09-2016 at 02:16 PM.
#43
To the OP - the guidance here re: spring rates, damping, etc. is the right place to start with a DE car. As folks have pointed out - wings, etc. really don't add as much DF as many think and will potentially create more issues than they corrects if not sufficiently tune-able (e.g., wing angle, splitter length, etc.).
We have been playing with Aero on our Cayman for a number of years and have what seems to be a decent package. We have had guidance from a leading automotive aero expert with previous F1 experience, but we do not have any tunnel data to support the design.
One example of creating an issue - when we added the diffuser we did see drag reductions and modest DF gains (if decent balance F and R), however the car became unstable in yaw over bumps as the airflow under the car was disrupted. We installed modified RSR rockers to attempt to seal the flow better - it worked. And then we found the next problem with the diffuser - using a straight lipped splitter the splitter would seal to the track under braking robbing the diffuser of airflow and abruptly altering rear DF (not nice). Modification of the splitter to allow for airflow under the car during braking stabilized the car - and seems to have improved the aero balance and stability overall.
Finally, the theory behind the dive planes is that they work more by diverting the airflow over the wheel openings and allowing the air in the wheel wells to exit more easily.
Would enjoy putting the car in the tunnel, but it is not likely:
We have been playing with Aero on our Cayman for a number of years and have what seems to be a decent package. We have had guidance from a leading automotive aero expert with previous F1 experience, but we do not have any tunnel data to support the design.
One example of creating an issue - when we added the diffuser we did see drag reductions and modest DF gains (if decent balance F and R), however the car became unstable in yaw over bumps as the airflow under the car was disrupted. We installed modified RSR rockers to attempt to seal the flow better - it worked. And then we found the next problem with the diffuser - using a straight lipped splitter the splitter would seal to the track under braking robbing the diffuser of airflow and abruptly altering rear DF (not nice). Modification of the splitter to allow for airflow under the car during braking stabilized the car - and seems to have improved the aero balance and stability overall.
Finally, the theory behind the dive planes is that they work more by diverting the airflow over the wheel openings and allowing the air in the wheel wells to exit more easily.
Would enjoy putting the car in the tunnel, but it is not likely:
#44
Race Car
http://www.formula1-dictionary.net/canards.html
#45
Rennlist Member
The dive planes, also called canards, have to primary functions. Look here:
http://www.formula1-dictionary.net/canards.html
http://www.formula1-dictionary.net/canards.html
however, to create a lower pressure area behind it far enough to effect the the flow out of the wheel (i suppose with goals of improving braking cooling flow), that would be a challenge due to the speeds and calculated "wake" that the dive plane would cause.
To the OP - the guidance here re: spring rates, damping, etc. is the right place to start with a DE car. As folks have pointed out - wings, etc. really don't add as much DF as many think and will potentially create more issues than they corrects if not sufficiently tune-able (e.g., wing angle, splitter length, etc.).
We have been playing with Aero on our Cayman for a number of years and have what seems to be a decent package. We have had guidance from a leading automotive aero expert with previous F1 experience, but we do not have any tunnel data to support the design.
One example of creating an issue - when we added the diffuser we did see drag reductions and modest DF gains (if decent balance F and R), however the car became unstable in yaw over bumps as the airflow under the car was disrupted. We installed modified RSR rockers to attempt to seal the flow better - it worked. And then we found the next problem with the diffuser - using a straight lipped splitter the splitter would seal to the track under braking robbing the diffuser of airflow and abruptly altering rear DF (not nice). Modification of the splitter to allow for airflow under the car during braking stabilized the car - and seems to have improved the aero balance and stability overall.
Finally, the theory behind the dive planes is that they work more by diverting the airflow over the wheel openings and allowing the air in the wheel wells to exit more easily.
Would enjoy putting the car in the tunnel, but it is not likely:
We have been playing with Aero on our Cayman for a number of years and have what seems to be a decent package. We have had guidance from a leading automotive aero expert with previous F1 experience, but we do not have any tunnel data to support the design.
One example of creating an issue - when we added the diffuser we did see drag reductions and modest DF gains (if decent balance F and R), however the car became unstable in yaw over bumps as the airflow under the car was disrupted. We installed modified RSR rockers to attempt to seal the flow better - it worked. And then we found the next problem with the diffuser - using a straight lipped splitter the splitter would seal to the track under braking robbing the diffuser of airflow and abruptly altering rear DF (not nice). Modification of the splitter to allow for airflow under the car during braking stabilized the car - and seems to have improved the aero balance and stability overall.
Finally, the theory behind the dive planes is that they work more by diverting the airflow over the wheel openings and allowing the air in the wheel wells to exit more easily.
Would enjoy putting the car in the tunnel, but it is not likely:
Interesting that you were not mounting a flat splitter up front... do you have venturi tunnels under the car, because if you dont, you really cant "rob" the defuser, as its main functiion is drag reduction by smoothing flow from under the car. if you have tunnels, then those high speed areas are use to create low pressure zones and that effectively creates more downforce delta. however, if you dont have tunnels, the flow is just ambient pressure as ive found in my pressure testing on the track and at high speeds. whatever the reason, the car (and you ) are super fast at fast tracks, so its working!