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  1. #201
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    Hi Ron,
    Thanks for the input. My tonneau cover folds up and with a wickerbill on it, it can not fold properly, so mounting it to the top of the tail gate is the best option for me.

    Right now, the front of the truck is a mess aerodynamically, there's extra holes in the grill and the core support is all chopped up from my cooling experimentation. I plan to block off the whole front, and experiment with hood vents and air dams in the near future. Will that have enough affect on the rear to negate any testing I do before fixing it, or should i clean up the front before any rear spoiler experimentation?

    For quantifying results, I planned to datalog VSS and do neutral decels from about 75 to 55 mph, once each direction on the same road per change. Using the time it takes to decel, with longer times being better was what I thought would be a good measure of the effectiveness of drag reduction. Does this make sense to you?

    Right now the truck will spin the tires at 100mph in 4th gear, so aside from better tires, I would like to add *some* down force. Do you think making a longer, flatter spoiler will work, or just standing up a short one closer to 90? I am also considering adding airtabs to the cover about 12" in front of the spoiler.

    thanks again
    Dave Strum



  2. #202
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    Hi Dave,

    Quote Originally Posted by TrendSetter View Post
    Hi Ron,
    Thanks for the input. My tonneau cover folds up and with a wickerbill on it, it can not fold properly, so mounting it to the top of the tail gate is the best option for me.
    Gotcha. For optimum for airflow control, shaping the spoiler or wickerbill mounting so it ends up at the height of the top of the tonneau cover will work best.

    Right now, the front of the truck is a mess aerodynamically, there's extra holes in the grill and the core support is all chopped up from my cooling experimentation. I plan to block off the whole front, and experiment with hood vents and air dams in the near future. Will that have enough affect on the rear to negate any testing I do before fixing it, or should i clean up the front before any rear spoiler experimentation?
    That's hard to say for certain. What some people consider a mess, may not cause any issues with the airflow over & around the cab ... and of course many things can. But if you're planning to block off the grill, I assure you that will make a big impact on the airflow to & over the cab. So yes, I'd do that before experimenting with the rear spoiler.

    For quantifying results, I planned to datalog VSS and do neutral decels from about 75 to 55 mph, once each direction on the same road per change. Using the time it takes to decel, with longer times being better was what I thought would be a good measure of the effectiveness of drag reduction. Does this make sense to you?
    It does. I've heard of guys doing that, but haven't done it myself. All I would suggest is making 2 runs each way & averaging the data.

    Right now the truck will spin the tires at 100mph in 4th gear, so aside from better tires, I would like to add *some* down force. Do you think making a longer, flatter spoiler will work, or just standing up a short one closer to 90?
    It all depends on your goals. The basic principles to remember are:
    A. Short wickerbills help the airflow separate easier, cleaner & better ... reducing turbulence & drag behind the truck.
    B. Typical high angle spoilers (45°-70°) will provide high degrees of high downforce by acting like a large wickerbill & turning the bed into the downforce surface. But high angle spoilers create the most turbulence & drag behind the vehicle.
    C. Long (10-14"), lower angle spoilers (0°-20°) with short wickerbills (1/2") at 45°-90° angles provide moderate downforce increases with very low drag. (Less than you have now with nothing to help the air separate.)
    D. Long (10-14"), lower angle spoilers (0°-20°) with tall wickerbills (1.5"-2") at a 45° angle provide significant downforce increases with moderate drag. (Much less than running a high angle spoiler.)


    I am also considering adding airtabs to the cover about 12" in front of the spoiler.

    thanks again
    Dave Strum

    The airtabs will help the airflow in two ways ... increasing the effectiveness of whatever downforce measures you choose to use ... and better airflow separation off the spoiler or wicker.

    Show us what you're doing on here when you get to it. Ttake care !




    Feel free to chime in or ask technical questions. I am here to help where I can.

    Ron Sutton

    Ron Sutton Race Technology
    Your One Stop, Turn & Go Fast, Car Building Resource Center for Autocross, Track, Road Racing & Triple Duty Pro-Touring Cars

    Check out our 400 Page Car Building Catalog HERE

    Features: Suspension, Chassis, Cages, Brakes, Rear Ends, Engines, Transmisssions, Aero & Much, Much More!

  3. #203
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    found some interesting software that seems relevant for this thread.

    modeling software:
    http://geuz.org/gmsh/

    CFD software:
    http://openfoam.org/

    both are freeware/open source and pretty powerful.

  4. #204
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    Quote Originally Posted by HellPhish89 View Post
    found some interesting software that seems relevant for this thread.

    modeling software:
    http://geuz.org/gmsh/

    CFD software:
    http://openfoam.org/

    both are freeware/open source and pretty powerful.
    Nice! Thanks for sharing.
    Feel free to chime in or ask technical questions. I am here to help where I can.

    Ron Sutton

    Ron Sutton Race Technology
    Your One Stop, Turn & Go Fast, Car Building Resource Center for Autocross, Track, Road Racing & Triple Duty Pro-Touring Cars

    Check out our 400 Page Car Building Catalog HERE

    Features: Suspension, Chassis, Cages, Brakes, Rear Ends, Engines, Transmisssions, Aero & Much, Much More!

  5. #205
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  6. #206
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    Feb 2011
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    Ron-

    I just finished reading the whole thread. Thanks for sharing your knowledge!

    I'm in need of some aero work on my duster. I've got a significant amount of front end lift at speed and need to settle it down. I have one of the Mopar 'go wings' on the car, which apparently does provide some downforce as it has dented the decklid. I'll probably still swap it out for a 0-15* design up to 12" with .5-2.0" wicker bill design as you have described.

    The front is where I really need the work. I'm considering employing a car of tomorrow type front splitter and air dam. Plan is to trace the leading edge of the front bumper for the splitter, and then copy the car of tomorrow recessed air dam even with my radiator crossmember.

    Questions:
    -what effects does the recessed air dam have on aero? Good bad or otherwise.
    -will the splitter length be more sensitive to its length in front of the air dam, or in relation to the leading edge of the bumper?
    -what are good material options for:
    Front Splitter
    Air dam
    Belly pan
    Side splitter
    Rear diffuser
    Rear spoiler
    Side hood vents

    Also, if you have another direction you suggest, I'm open to it. Including losing the hood scoop.

    Car at rest:


    Car at 135 mph:


    The car is used for road course track days, standing mile, and big bend open road race. Looking to go faster in all of the above.

    Thank you,
    Wade Koehl

  7. #207
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    Ron or anyone, last week I spectated at a open track day event for PT cars. Course had a 100+ mph lefthand flat dog leg, that I happened to be close by and watching. Corner has inside generous curbing. A car that looked to be well sorted out and driven all day, caught the inside curb fairly well. Driver, according to numerous live action pics i took, was counter steering, what seemed to be needed. However as car slowed it never seemed to correct itself from about 15? degree of counterclockwise rotation/yaw, from its direction of travel. Car had what looked to be a well design rear wing, albeit at a very shallow angle ( it was a HS track) and car had 8? VG of a large size located what seemed to be the correct location. They were mounted in a slight radial pattern, with the outside ones mirrored imaged almost at a 20? Deg off center line. I mentioned this following idea to the driver, after watching his go Pro in the pits, shortly after the off track excursion. He at that time commented the rear end would not come back in line. So my thought is, with proper counter steer, without heavy throttle, if the rear has traction and no other forces are in effect, the rear should at some point begin to follow the front. This did not appear to happen. So My first thought is, why no rear traction? Could the front left tire hitting a curb change the rear wing shallow angle enough to lose enough DF to have the rear end step out, and/or do VG's then go completely turbulent at a combined direction to air flow at 35?Deg, completely disrupting any rear wing effects and then all rear wing DF is lost, and car stays yawed, especially if driver is understandably getting on the brakes because of lack of rear end control, making rear further unstable?
    Last edited by j-c-c; 06-03-2014 at 06:41 PM. Reason: spelling

  8. #208
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    ^ since this was me let me clarify a few things...

    It was a high speed left hand kink - 130ish, 4th gear, tap of the brakes - Rolex 4 at Daytona

    While the curbing is "generous" is is also very low and usable. Regardless the car was stepping out before the curbing came in to play so while I may have "caught" the curbing it had no influence on the chain of events

    I was counter steering like a son-of-a-gun

    Way more that 15 degrees of rotation as the poop hit the fan

    Wing is dynamic - it was approximately 14 - 16 degrees (need to look at notes) under braking and possibly close to stalling - but it was the 40th lap of the day in that configuration. It is, however, quite shallow appearing at high speeds.

    There are eight agent 47 vortex generators mounted per their instructions and while this was the first outing using them it was not the first lap.

    All if that notwithstanding... In watching the video (and having relived it on more than one occasion over the last 10 days) I can safely say the following:

    A. I got through Rolex 3 very well and was perhaps carrying more speed than normal
    B. I was perhaps slightly off my normal line approaching CE but probably not by more than a foot (I know)
    C. Under/just after braking the car appears to bounce a bit although it looks like rough track not and not the car
    D. The car is stepping out just prior to the apex and curbing
    E. While I was counter steering the front wheels are in dirt almost immediately
    F. While counter steering I did, in fact, arrest the rotation until the wall ultimately impeded my progress at a point which corresponded with a side access road

    Bottom line - there was something on the track, I got in to it at a high rate of speed, the back end came around and once the front wheels got off the pavement there was minimal room to deal with it. I can provide the supposition that I was fast in to the corner and perhaps was off line. I can second guess things and wonder if I may have lifted as I approached the apex after braking in an attempt to scrub a touch more speed. I can safely say that there were no significant aero changes from previous laps.

    As far as getting on the brakes... When faced with an infinite length of Armco lit up by my own headlights there were limited practical options. Allowing the car to rotate further would have guaranteed permanent damage beyond the front sheet metal. While ugly ... nosing he car in was preferable to going in sideways or backwards.

    It was a racing deal - aero had minimal influence on the events beyond the norm. Video, in fact, shows the AOA is more than ample throughout the spin. If I had to question the influence, I would wonder if the fact that the wing was in split mode during the spin - i.e. The inside was at a greater AOA than the outside - had more bearing on events. But in fairness... This wasn't the first time I was driving sideways...
    Last edited by James OLC; 06-04-2014 at 03:48 AM.
    James
    1967 Camaro RS - The OLC
    1989 Camaro 1LE - The CMC Car
    1989 Camaro 1LE R7U - The Players Car

  9. #209
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    ANy video you are willing to share James? I feel for you on that deal and am glad it wasnt uglier...

  10. #210
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    Quote Originally Posted by Uhcoog1 View Post
    Ron-

    I just finished reading the whole thread. Thanks for sharing your knowledge!
    You're welcome. I enjoy helping.

    I'm in need of some aero work on my duster. I've got a significant amount of front end lift at speed and need to settle it down. I have one of the Mopar 'go wings' on the car, which apparently does provide some downforce as it has dented the decklid. I'll probably still swap it out for a 0-15* design up to 12" with .5-2.0" wicker bill design as you have described.
    Gotcha.

    The front is where I really need the work.
    Yes it does. There is a TON of air going under your car. This needs to be reduced.

    I'm considering employing a car of tomorrow type front splitter and air dam. Plan is to trace the leading edge of the front bumper for the splitter, and then copy the car of tomorrow recessed air dam even with my radiator crossmember.
    Great plan.

    Questions:
    -what effects does the recessed air dam have on aero? Good bad or otherwise.
    It creates more downforce on the splitter than compared to running a splitter under a 90° vertical airdam that was flush with nose. Just make sure to provide this airflow a smooth transition around the nose & off the ends.

    -will the splitter length be more sensitive to its length in front of the air dam, or in relation to the leading edge of the bumper?
    The effective splitter length is measured from the airdam.

    -what are good material options for:
    Front Splitter
    Carbon fiber, ABS plastic, thick aluminum, fiberglass, etc.

    Air dam
    Any body material, fiberglass, carbon fiber, sheetmetal, etc.


    Belly pan
    Aluminum sheetmetal, smooth fiberglass or carbon fiber sheets.

    Side splitter
    Aluminum sheetmetal, smooth fiberglass or carbon fiber sheets. But ... this needs to be thicker than the belly pan.

    Rear diffuser
    Same as belly pan ... aluminum sheetmetal, smooth fiberglass or carbon fiber sheets.

    Rear spoiler
    Aluminum sheetmetal, fiberglass or carbon fiber.

    Side hood vents
    Aluminum sheetmetal, fiberglass or carbon fiber will work, but I typically come up with a shape and have it maed with fiberglass or carbon.


    Also, if you have another direction you suggest, I'm open to it. Including losing the hood scoop.
    That hood scoop is very disruptive to the airflow over the hood & roof, but I feel it is also a style statement. I feel strongly that in the sport of ProTouring, each of us need to make our own personal style decisions for the overall look of the car. If we didn't care about looks at all, we wouldn't be using musclecars. So go with what makes you happy, just be clear that scoop has a lot of turbulence to it. The least turbulent is an open cowl intake, like stock cars. The second least turbulent would be smooth cowl style hood scoops.

    The car is used for road course track days, standing mile, and big bend open road race. Looking to go faster in all of the above.

    Thank you,
    Wade Koehl
    Wade, reducing the airflow under your car will provide much more downforce, more tire grip & more driving stability. For the high speeds of road courses & standing mile runs ... you will need to balance the downforce front-to-rear. The car will most likely have different needs on sweeping high speed 120-130+ mph corners of road courses versus standing mile runs.

    Sweeping corners often require more rear wing/spoiler angle to create adequate rear downforce. So this should be your priority. Once you have the car "aero balanced" for road courses, you will probably have more rear downforce than you need for the same speed on straight runs. BUT ... as the speed increases ... to 150- 175+ ... the downforce on the front nose will increase at a higher rate than the downforce on the rear spoiler. So the additional downforce from your road race set-up would be a good starting point.

    You didn't say what kind of speeds you run in the standing mile, but once you have a splitter & airdam on the front, and you're making runs ... pay VERY CLOSE attention to the feel of the car at speeds above 140 mph. If the rear starts to feel light, ease out of the throttle, finish your run & add more rear downforce before the next run. On the other hand, if you have more rear downforce than you need, you can "trim" the rear downforce a small step at a time to increase top speed. "Trim" is a racing term meaning to make changes to reduce the rear downforce. I can't say strong enough to sneak up on this.


    Best wishes, & please keep us apprised of your project's aero progress.

    Feel free to chime in or ask technical questions. I am here to help where I can.

    Ron Sutton

    Ron Sutton Race Technology
    Your One Stop, Turn & Go Fast, Car Building Resource Center for Autocross, Track, Road Racing & Triple Duty Pro-Touring Cars

    Check out our 400 Page Car Building Catalog HERE

    Features: Suspension, Chassis, Cages, Brakes, Rear Ends, Engines, Transmisssions, Aero & Much, Much More!

  11. #211
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    Feb 2011
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    Thanks for the advice, Ron! I'll get to work on it and circle back with the progress.

    Standing mile: 146 mph. Goal: 180 mph
    BBORR: 125-140 class. next year: 135-168 class.

  12. #212
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    Quote Originally Posted by j-c-c View Post
    Ron or anyone, last week I spectated at a open track day event for PT cars. Course had a 100+ mph lefthand flat dog leg, that I happened to be close by and watching. Corner has inside generous curbing. A car that looked to be well sorted out and driven all day, caught the inside curb fairly well. Driver, according to numerous live action pics i took, was counter steering, what seemed to be needed. However as car slowed it never seemed to correct itself from about 15? degree of counterclockwise rotation/yaw, from its direction of travel. Car had what looked to be a well design rear wing, albeit at a very shallow angle ( it was a HS track) and car had 8? VG of a large size located what seemed to be the correct location. They were mounted in a slight radial pattern, with the outside ones mirrored imaged almost at a 20? Deg off center line. I mentioned this following idea to the driver, after watching his go Pro in the pits, shortly after the off track excursion. He at that time commented the rear end would not come back in line. So my thought is, with proper counter steer, without heavy throttle, if the rear has traction and no other forces are in effect, the rear should at some point begin to follow the front. This did not appear to happen. So My first thought is, why no rear traction? Could the front left tire hitting a curb change the rear wing shallow angle enough to lose enough DF to have the rear end step out, and/or do VG's then go completely turbulent at a combined direction to air flow at 35?Deg, completely disrupting any rear wing effects and then all rear wing DF is lost, and car stays yawed, especially if driver is understandably getting on the brakes because of lack of rear end control, making rear further unstable?


    Quote Originally Posted by James OLC View Post
    ^ since this was me let me clarify a few things...

    It was a high speed left hand kink - 130ish, 4th gear, tap of the brakes - Rolex 4 at Daytona

    While the curbing is "generous" is is also very low and usable. Regardless the car was stepping out before the curbing came in to play so while I may have "caught" the curbing it had no influence on the chain of events

    I was counter steering like a son-of-a-gun

    Way more that 15 degrees of rotation as the poop hit the fan

    Wing is dynamic - it was approximately 14 - 16 degrees (need to look at notes) under braking and possibly close to stalling - but it was the 40th lap of the day in that configuration. It is, however, quite shallow appearing at high speeds.

    There are eight agent 47 vortex generators mounted per their instructions and while this was the first outing using them it was not the first lap.

    All if that notwithstanding... In watching the video (and having relived it on more than one occasion over the last 10 days) I can safely say the following:

    A. I got through Rolex 3 very well and was perhaps carrying more speed than normal
    B. I was perhaps slightly off my normal line approaching CE but probably not by more than a foot (I know)
    C. Under/just after braking the car appears to bounce a bit although it looks like rough track not and not the car
    D. The car is stepping out just prior to the apex and curbing
    E. While I was counter steering the front wheels are in dirt almost immediately
    F. While counter steering I did, in fact, arrest the rotation until the wall ultimately impeded my progress at a point which corresponded with a side access road

    Bottom line - there was something on the track, I got in to it at a high rate of speed, the back end came around and once the front wheels got off the pavement there was minimal room to deal with it. I can provide the supposition that I was fast in to the corner and perhaps was off line. I can second guess things and wonder if I may have lifted as I approached the apex after braking in an attempt to scrub a touch more speed. I can safely say that there were no significant aero changes from previous laps.

    As far as getting on the brakes... When faced with an infinite length of Armco lit up by my own headlights there were limited practical options. Allowing the car to rotate further would have guaranteed permanent damage beyond the front sheet metal. While ugly ... nosing he car in was preferable to going in sideways or backwards.

    It was a racing deal - aero had minimal influence on the events beyond the norm. Video, in fact, shows the AOA is more than ample throughout the spin. If I had to question the influence, I would wonder if the fact that the wing was in split mode during the spin - i.e. The inside was at a greater AOA than the outside - had more bearing on events. But in fairness... This wasn't the first time I was driving sideways...

    Hi Guys,
    Sorry to hear about your car James.
    I hope you get it back together the way you want it.

    First, I'm sure everyone understands it can tricky to accurately diagnose an issue from a forum conversation or any conversation. I'm not magic, just experienced. But I'll do my best to lead the conversation where it needs to go. James, thanks so much for chiming in with details. Otherwise this would be a wild goose chase. I have suspicions ... which is a fancy way of saying I "think" I know the causes ... but in reality there could be other factors not brought to light so far.

    I'm going to lay this out in a "preview-detail-summery" fashion.

    Preview:

    1. We should consider whether the car lacks adequate mechanical rear grip for high speed corners ... tends to be loose in fast sweeping corners ... and the aero grip from the rear wing downforce is critical to the car's handling in fast sweeping corners ... regardless of events in this specific corner.
    2. Once the car was past 10-15° yaw angle, the wing becomes substantially less effective.


    Detail:
    In working out the handling of a car, both mechanical grip & aero grip combine to define the handling characteristics. Mechancial grip is the grip we achieve with the suspension. Aero grip is of course from downforce (or lift).

    Let's start with mechanical grip. One of the first things I look at in tuning road course cars is how does the car handle in low speed corners versus the high speed corners. These two are ALWAYS a compromise when driven to the limits. I am often tuning to the either the driver's preference or the compromise providing the best lap time. While we can make a car pull high G's in the tighter corners, the car will see the highest G's in high speed corners and therefore the car's roll angle will be the highest there.

    A quick tutorial for everyone following along: If a car is awesome in the low speed corners & loose in high speed corners ... the car is rolling too much. If a car is awesome in the high speed corners & loose in low speed corners ... the car is rolling too little. (By rolling, I mean roll angle).

    It is not uncommon for a car's suspension to be tuned to be optimum for lower speed corners ... making it loose in high speed corners. Adding aero downforce in the rear with a some combination of spoiler/wing/wicker can help. The aero does little at low speeds, so the low speed handling stays balanced ... and as speeds increase & the aero starts being more & more effective, the additional rear downforce helps make the car better balanced in the high speed corners. Of course if the rear mechanical grip isn't strong at high corner speeds ... the spoiler or wing has to do the majority of the work providing rear grip. That makes the car very aero dependent ... and very aero sensitive.

    If ... and I don't know this for sure because I'm not there with you hands-on & involved ... if the car didn't have quite enough aero grip for this track, this day, this corner ... and you got the car in yaw ... the car lost a lot of the rear grip it had. Once the car went into a 15°+ state of yaw ... the aero downforce reduced substantially ... so a car that could be very aero dependent ... suddenly lost a lot of aero downforce.

    Summary:
    If my assessment is correct. You will want to increase rear grip at high speeds.

    You could do it with more aero. If you go this route, I wouldn't run more AOA (Angle of Attack) ... because you would be too close to the stall angle ... plus high wing angles cause turbulence & drag. I would run a larger wing. Frankly, in racing we have to tune this for every track & changing track & weather conditions, so I like having a bit more wing or spoiler surface area than I need, so I can run less attack angle. But if you fix it this way, the car will still be aero dependent & aero sensitive. Anytime you get the car in yaw, you will still lose downforce.

    So if it were me, I would build in more rear mechanical grip, so the car is less aero dependent & sensitive. I would still run the wing ... for sure. I might even make it larger so you could run less angle. Wings are a great tool to add high speed grip. I just wouldn't make it do so much of the work.

    Rear mechanical grip is a factor of roll centers, CG height, track widths, track ratio, spring rates, sway bar rates & shock valving.

    I would start by running the calcs & see where your FLLD/RLLD percentages are ... compared to the car's front-to-rear weight bias. That will tell you if you need something specific to the front or rear suspension. For short tracks, autocross & road courses with priority on tight corners ... I typically start around 5% more FLLD % than front weight bias and fine tune from there. For tracks with faster corners I typically start around 6% more FLLD % (with a bigger sway bar) ... and fine tune from there.

    If your FLLD/RLLD percentages check out, then you simply need to increase the TRS Total Roll Stiffness ... and maintain the proper FLLD/RLLD percentages. There are a hundred combinations to do this & a thousand opinions on which way is best & why. I tend to utilize larger sway bars in the front & a balance of spring & sway bar rate in the rear ... both with low dynamic roll centers.

    On a separate note, there are a lot of things we can do to increase rear tire grip with shock valving, that doesn't show up in any of the calcs. I have a new client with a 69 Camaro track car that was always loose on corner entries. I had custom rear shocks built for him with what I call high grip properties that use super low rod pressure & soft low speed piston valving combined with stiffer mid-speed valving. Now it has excellent rear grip & we didn't touch any of the normal tuning items.

    James, if you'd like my help in calculating the current suspension package & working out an optimum set-up ... and if you're open to doing it on a forum thread so others can learn too ... I'd be happy to help. We'd just start a separate thread focused on this objective.



    Last edited by Ron Sutton; 06-04-2014 at 01:59 PM.
    Feel free to chime in or ask technical questions. I am here to help where I can.

    Ron Sutton

    Ron Sutton Race Technology
    Your One Stop, Turn & Go Fast, Car Building Resource Center for Autocross, Track, Road Racing & Triple Duty Pro-Touring Cars

    Check out our 400 Page Car Building Catalog HERE

    Features: Suspension, Chassis, Cages, Brakes, Rear Ends, Engines, Transmisssions, Aero & Much, Much More!

  13. #213
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    Quote Originally Posted by Uhcoog1 View Post
    Thanks for the advice, Ron! I'll get to work on it and circle back with the progress.
    Cool. Please do.

    Standing mile: 146 mph. Goal: 180 mph
    BBORR: 125-140 class. next year: 135-168 class.
    Sweet. Show us your progress.



    Feel free to chime in or ask technical questions. I am here to help where I can.

    Ron Sutton

    Ron Sutton Race Technology
    Your One Stop, Turn & Go Fast, Car Building Resource Center for Autocross, Track, Road Racing & Triple Duty Pro-Touring Cars

    Check out our 400 Page Car Building Catalog HERE

    Features: Suspension, Chassis, Cages, Brakes, Rear Ends, Engines, Transmisssions, Aero & Much, Much More!

  14. #214
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    Quote Originally Posted by Ron Sutton View Post
    Hi Guys,
    Sorry to hear about your car James. I hope you get it back together the way you want it.
    It's the nature of the beast. We all say it will never happen to us but eventually, given enough time, it will. I was fortunate that it hit how and where it did. We will have the car back together for Road America (I hope) in some form or another. A permanent fix will have to wait. It's in good hands now.

    James, if you'd like my help in calculating the current suspension package & working out an optimum set-up ... and if you're open to doing it on a forum thread so others can learn too ... I'd be happy to help. We'd just start a separate thread focused on this objective.
    I'm game to try provided the work can be done within the confines of my existing relationship with RideTech. And with the caveat that I am getting old, stubborn, and forgetful.
    James
    1967 Camaro RS - The OLC
    1989 Camaro 1LE - The CMC Car
    1989 Camaro 1LE R7U - The Players Car

  15. #215
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    I'm looking forward to the new thread on this. Btw, what does FLLD/RLLD mean?
    67 Camaro CAM/C-prepared autocross Project
    72 Nova Street/Drag Car Project

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    Ucoog1:

    I would think what Ron is thinking on the hood scoop issues has merit. But not clear if that is simply a drag issue, but would likely carry all the way back to the rear wing, and/or a contributor to your suspected front end lift observation. I completely understand the form/function aspect. If it was me I would first do some highest speed possible go-pro yarn tests in the whole area. And maybe consider a single purpose flat FG hood for high speed (100+mph) events, if alternative easy engine air intake options exist. Then you could do some multiple coast down tests back to back and gain some more info with little effort/expense.

  17. #217
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    Quote Originally Posted by bergers59 View Post
    I'm looking forward to the new thread on this. Btw, what does FLLD/RLLD mean?

    When I am designing a baseline suspension set-up, I use FLLD calculations. FLLD stands for Front Lateral Load Distribution. But hey … we’re car guys. I like to think of FLLD percentage calculations as simply a way of quantifying a car’s front roll resistance. There is of course a RLLD for the rear … as a way of quantifying a car’s rear roll resistance. Remember, more roll resistance = less roll angle.

    Please don’t confuse these terms … FLLD, RLLD or Lateral Load Distribution with “roll couple.” They are similar in meaning but different in accuracy. FLLD/RLLD calculations are more accurate in determining the front & rear roll angles of cars … simply because they take into account all the factors that “roll couple” does not.

    A quick primer …
    FLLD/RLLD are stated in percentages, not pounds. The two always add up to 100% as they are comparing front to rear roll resistance split. Knowing the percentages alone, will not provide clarity as to how much the car will roll … just how the front & rear roll in comparison to each other. If the FLLD % is higher than the RLLD % … that means the front suspension has a higher resistance to roll than the rear suspension ... and therefore the front of the car runs flatter than the rear of the suspension … which is the goal.

    The term “Total Roll Stiffness” is expressed in foot-pounds per degree of roll angle … and it does guide us on how much roll angle the car will achieve when cornering, as long as g-forces are known or can be calculated.

    So you pick suspension spring rates & shock valving* … and choose geometry settings like track width & roll center to achieve:
    Less roll resistance for the end of the car you want to roll more.
    More roll resistance for the end of the car you want to roll less.
    * Shocks do not factor into FLLD or RLLD calculations, but do play a real world role in the rate the car rolls.

    We typically want slightly more roll angle in the rear & less roll angle in the front of the car … and therefore need lower roll resistance in the rear & higher roll resistance in the front, but you need to account for the car’s front to rear weight bias. When I design a car, my baseline is to have 5% higher FLLD% than the car’s front weight percentage for tight tracks & 6% higher FLLD for high speed tracks.

    So, for example ...
    * For a front heavy car with 53%/47% front/rear weight bias ... we start with 58-59% front roll resistance (FLLD).
    * For a balanced car with 50%/50% front/rear weight bias ... we start with 55-56% front roll resistance (FLLD).
    * For a rear heavy car with 46%/54% front/rear weight bias ... we start with 51-52% front roll resistance (FLLD).

    Now that’s a starting point. As a tuning guide only, because there are several “exceptions” … so TYPICALLY:
    a. Decreasing the front roll resistance (FLLD) … increases the front roll angle … and loosens the car during corner entry & middle.
    b. Increasing the rear roll resistance (RLLD) … decreases the rear roll angle … and loosens the car during corner entry & middle.
    c. Increasing the front roll resistance (FLLD) … decreases the front roll angle … and tightens the car during corner entry & middle.
    d. Decreasing the rear roll resistance (RLLD) … increases the rear roll angle … and tightens the car during corner entry & middle.

    Make sense?


    Feel free to chime in or ask technical questions. I am here to help where I can.

    Ron Sutton

    Ron Sutton Race Technology
    Your One Stop, Turn & Go Fast, Car Building Resource Center for Autocross, Track, Road Racing & Triple Duty Pro-Touring Cars

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  18. #218
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    makes sense, but how do you find those percentages out accurately? is there an equation involving spring rate, sway bar stiffness, and corner weights?
    67 Camaro CAM/C-prepared autocross Project
    72 Nova Street/Drag Car Project

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    Last night killing time I thumbed thru a 5/14 Racecar Engineeriing on the magazine rack. It had FWIW, an 8? page article by Aerodynamist Simon McBeath? on wings and yaw angles, including differing sideplates. Worth reading. Quick synopsis, DF drops off slowly until approx 15Deg, then heads downhill quickly, larger end plates worsen DF loss in yaw, BUT they start adding a slightly increasing sideforce.

  20. #220
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    Quote Originally Posted by bergers59 View Post
    makes sense, but how do you find those percentages out accurately? is there an equation involving spring rate, sway bar stiffness, and corner weights?

    It involves more data than that. It requires, car weight front & rear, roll centers, track width, CG height (estimate yours at 19") spring & sway bar rates & motion ratios ... which it calculates if you enter all the measurements. The formula is very accurate & frankly part of why I am able to work out setups for cars all over the world that I never see. Of course I need to "see" a lot of info & use my experience of what works & what doesn't on the type of tracks they're running.

    The age of computers & internet has spoiled me, so rarely do I manually calculate stuff anymore. I prefer to use & recommend Performance Trends products for a few key reasons. The TRS/FLLD/RLLD calculations come in several of their software versions.

    3 Options are:

    A.
    Get the full 3D suspension analyzer version, which is more complex to use, mainly because you have to sort through a gazillion input options you may not use. Performance Trends software is the easiest to use of the complete, 3D software brand options, but that's like saying rebuildign a manual trans is easier than an auto trans. It's still quite "involved." It costs $400 & you can see it HERE.

    B. Their basic front suspension software, called Roll Center Calculator, which I highly recommend for car guys working out their roll center, camber gain, dive evaluations, etc. BUT ... does not include TRS/FLLD/RLLD. It is $79. Go HERE.

    C.
    The best value is their "Roll Center Calculator PLUS" for $129 that includes complete front & rear suspension work ups & overall handling calculations, including TRS/FLLD/RLLD, which I find to be critical in working out handling balance. This is a pretty good full suspension program for only $129. Go HERE.

    The FLLD calculation in the "Plus" is worth the price of the software all by itself, because you can work out combinations of roll center, track width changes, spring rates & sway bar rates and KNOW how balanced the car will be.





    Feel free to chime in or ask technical questions. I am here to help where I can.

    Ron Sutton

    Ron Sutton Race Technology
    Your One Stop, Turn & Go Fast, Car Building Resource Center for Autocross, Track, Road Racing & Triple Duty Pro-Touring Cars

    Check out our 400 Page Car Building Catalog HERE

    Features: Suspension, Chassis, Cages, Brakes, Rear Ends, Engines, Transmisssions, Aero & Much, Much More!

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