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You can determine downforce through other means of measurements as well. We used computer simulations to determine the ball park range on what downforce we should be making. With out suspension pots how ever or a wind tunnel we can't get these numbers in real time. we never installed those vents in the fenders because we are waiting on Trackspec Motorsports to send us some more refined louvers and bigger. We also have a new splitter/hood ducting that should create two time the amount of downforce in the front of the car. Determining different diffusers are all done in CAD. You want the splitter as low as possible but you do not want it touching the ground at all. it loses all its effectiveness when that happens.
Did you have a CFD program and a solid model of the S2000 to do the computer simulations?
The swan neck Voltex Type 7. And a great selection on the shocks...other than many be some of the special F1 shocks and Ohlins TTRs, probably the most advanced shocks on the market. Are you ordering them with digressive valving and/or a blow-off piston? Their only drawback seems to be needing a shock vacuum to bleed them. Are you also planning on testing different camber angles? Lot's of people on the forum seemed to stop at around -3.5°. Hoosier is recommending -4.0° for Spec Racer Ford fronts. Roger Caddell at AIM Sports has said that they found the limit on negative caster being an improvement was when the car was hard to stop on a Mustang in a semi-pro series.
On topic, the downforce from a good splitter and wing plus the questionable geometry in lowered S2ks are reasons I was curious if people were running stiffer springs.
Regular Type 7, not the Swan mount. I got a good deal on this one.
Digressive, They were built by PSI in california. I have had them for a while. Camber is something I will be playing with, Most guys do stop around 3.5* as you said. I will probably stay close to that for now till I can get real temp data (not the in the pits measured cause that doesnt really tell you anything). All with time, first thing is to get the basics done, lots left to do.
Regular Type 7, not the Swan mount. I got a good deal on this one.
Digressive, They were built by PSI in california. I have had them for a while. Camber is something I will be playing with, Most guys do stop around 3.5* as you said. I will probably stay close to that for now till I can get real temp data (not the in the pits measured cause that doesnt really tell you anything). All with time, first thing is to get the basics done, lots left to do.
From what has been posted, most people are running their wings with very little angle, so getting rear downforce isn't the issue. Of course, the issue is probably not having enough front downforce. In that case, the swan neck would be mainly a drag issue. In the front, have you decided on an endplate design?
Temp data may not tell the full story on camber angle. With temps, the goal was even carcass temps across the tire. IR sensors give the dynamic temps, but even then lap times are the real test. This is a video of an S2000 at VIR with temps across the tire dynamically:
With the ride height sensors you should be able to determine downforce and how effective your spring rates are in handling chassis movement. You indicated you had a spreadsheet that determined lateral g's. What tire model it use? How did it determine the mechanical contribution to roll and pitch resistance?
J's runs very high rates on their dedicated track cars. 22kg/mm F 26kg/mm R I think on one of their cars when testing at Suzuka. This is a car with full wide body aero treatment and sequential transmission. Japanese tracks are generally very smooth.
In the front, have you decided on an endplate design?
Temp data may not tell the full story on camber angle. With temps, the goal was even carcass temps across the tire. IR sensors give the dynamic temps, but even then lap times are the real test. This is a video of an S2000 at VIR with temps across the tire dynamically:
With the ride height sensors you should be able to determine downforce and how effective your spring rates are in handling chassis movement. You indicated you had a spreadsheet that determined lateral g's. What tire model it use? How did it determine the mechanical contribution to roll and pitch resistance?
No endplates for front. Class doesnt allow it. But, I can do this and most likely will.
I work in the tire industry and have a few tricks for makes IR data work and how to analyze it, I just need a system for personal use to do it.
As for the spreadsheet, its uses a scale of Force and Moment data from a Trans-Am Hoosier based on tire size. It gives rough numbers but the balance/weight transfer part is right. I have a general idea of what the Lat G steady state will be so I can iterate around that.
No endplates for front. Class doesnt allow it. But, I can do this and most likely will.
I work in the tire industry and have a few tricks for makes IR data work and how to analyze it, I just need a system for personal use to do it.
As for the spreadsheet, its uses a scale of Force and Moment data from a Trans-Am Hoosier based on tire size. It gives rough numbers but the balance/weight transfer part is right. I have a general idea of what the Lat G steady state will be so I can iterate around that.
The picture isn't visible. What class are you running in?
Are you doing a force-based model in computing the force contribution from the geometry?
The sensor in the video are very inexpensive, very compact, and using a CAN bus are setup to use either an AIM or Motec display or AutosportLabs RaceCapture Mark II to record the output. Even with an acquisition unit, it could be installed for under $1500. He has really expanded into a variety of related sensors available or in the works. A load one using strain gages may capture something we don't otherwise have. Potentially a shock dyno in the car.
The picture isn't visible. What class are you running in?
Are you doing a force-based model in computing the force contribution from the geometry?
The sensor in the video are very inexpensive, very compact, and using a CAN bus are setup to use either an AIM or Motec display or AutosportLabs RaceCapture Mark II to record the output. Even with an acquisition unit, it could be installed for under $1500. He has really expanded into a variety of related sensors available or in the works. A load one using strain gages may capture something we don't otherwise have. Potentially a shock dyno in the car.
Originally Posted by Tougefactory
Working on CFD actually, We do have a pretty good model of the S2000. I'll have to share it on here sometime.
That would be great! I have planning to build a model in OnShape or TurboCAD and model in in OpenFOAM. I don't have a clue how to setup the road vs. the car though and it is doubtful I'll have the time to do more than simple modeling.
Originally Posted by andrewhake
J's runs very high rates on their dedicated track cars. 22kg/mm F 26kg/mm R I think on one of their cars when testing at Suzuka. This is a car with full wide body aero treatment and sequential transmission. Japanese tracks are generally very smooth.
A lot of oval cars have tripled their effective spring rate because of aero. Because they have a ride height rule, this is done with bump springs, a very soft primary spring, and pull-down shocks. For example, they may have had a 325 lbf/in 12-in tall front spring 20 years ago. Now they may have a 100 lbf/in 16-in tall 'barrel" spring with a 1000 lbf/in or 1200 lbf/in bump spring shimmed to hold the front airdam 1" off the racing surface. Effectively they are riding on much stiffer springs.
Originally Posted by No.Division
No endplates for front. Class doesnt allow it. But, I can do this and most likely will.
I work in the tire industry and have a few tricks for makes IR data work and how to analyze it, I just need a system for personal use to do it.
As for the spreadsheet, its uses a scale of Force and Moment data from a Trans-Am Hoosier based on tire size. It gives rough numbers but the balance/weight transfer part is right. I have a general idea of what the Lat G steady state will be so I can iterate around that.
Picture is now visible. That car has a dam and a significant splitter. Interestingly, that Miata doesn't seem to have a wing to balance it but does have a huge hood exit for flow through the radiator. Does it have a flat bottom and rear diffuser? No fender vents. It seems to be an example of a car where spring rates probably need to be chosen to manage the aero package.
A good CFD question would be how high the lip between the splitter and the radiator entry should be or if there should be one. I think most sports racers don't have one.
02-06-2017, 12:58 PM
