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Aero and Suspension Tuning With True Type Coilovers

So I have been doing some research on adding a rear diffuser to my current setup when I ran across an article/blog on the Professional Awesome Racing website https://professionalawesome.com .

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Old 07-04-2019, 12:53 PM   #1 (permalink)
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Default Aero and Suspension Tuning With True Type Coilovers

So I have been doing some research on adding a rear diffuser to my current setup when I ran across an article/blog on the Professional Awesome Racing website https://professionalawesome.com. After read their article on aero and downforce I decide to shoot them an email to see if their splitter diffuser would be a good addition to my front aero. Long story longer we have exchange sever emails regarding my aero and suspension most significantly my spring rates and the owner Dan O'Donnell provide me with the following information:

So you have a “true type” rear, meaning the spring is directly on the damper body, not in the stock bucket. This has the effect of dramatically increasing the “wheel rate” or effective spring rate at the wheel, if you are using the same spring rate you use previously. If you are running 14k front 12k rear or 800lbs front 700lbs rear, the car will oversteer badly. I just had a long discussion with Savanna Little and Kevin Parlett. They are using a “true type” design as well on similar chassis designs and no suspension manufacture compensates properly for the change.

With your rear wing, I think you can safely add our diffusers and vents, but I would really, really want you to change spring rates to a proper setup. Your system is borderline unsafe in my opinion. Let me know if you want to do the calculations to get the right springs in there. Quick math is lettings me like if you have 14k front springs, you need to be around 5-6k in the rear.

So I am prepared to pay for the his consulting fee as this a steep learning curve for me and at my soon to be power level I don't want to be wadding my car up or possibly hurting anyone else. Here is where I need some help as he needs some information from me to dial the best spring rates for the rear coilovers. I need to provide him with corner weights for the car and obviously right now I have no way to do so. He doesn't need to have actual numbers but just need to be in the ballpark. My car weighs about 3440 with me in it and I am 210 lbs. If any of you have corner weight numbers and your car is of similar weight I would greatly appreciate you providing them to me.

Thank you in advance and go check out the Professional Awesome Racing!

Cheers,
Bob
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Old 07-04-2019, 01:08 PM   #2 (permalink)
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That's my corner weights I have the stillen charger with the topgunz cooler up front

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Old 07-04-2019, 01:10 PM   #3 (permalink)
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This was my car, after SPL arms and true type rear conversion, with driver a driver between 120lbs to 140lbs, and maybe half tank of gas. Stock motor, no bolt on power mods. 265/35/19 in front instead of the 245/40/19.

https://vorshlag.smugmug.com/Custome...ed/i-ktQMxz4/A
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Old 07-04-2019, 01:43 PM   #4 (permalink)
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Quote:
Originally Posted by nic370 View Post
That's my corner weights I have the stillen charger with the topgunz cooler up front

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Quote:
Originally Posted by cv129 View Post
This was my car, after SPL arms and true type rear conversion, with driver a driver between 120lbs to 140lbs, and maybe half tank of gas. Stock motor, no bolt on power mods. 265/35/19 in front instead of the 245/40/19.

https://vorshlag.smugmug.com/Custome...ed/i-ktQMxz4/A
Thanks for the info!!!
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Old 07-04-2019, 01:52 PM   #5 (permalink)
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No problem hope it helps

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Old 07-04-2019, 01:57 PM   #6 (permalink)
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Keep them coming!

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Old 07-04-2019, 07:52 PM   #7 (permalink)
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I went through their downforce guide and it is very helpful, I got convinced into getting only front splitter and rear wing for my planned aero, as they are the most simple and effective way to gain more/cleaner downforce.



and here is my car weight, very close to your car weight, but I think with half fuel tank.



Also, about spring rates, this is something I noticed when I got my mca reds, there was a big difference in front and rear, 21k/7k, when I had my rear height higher than fronts by around an inch, the car was nearly neutral, but when I tried with lower rear, around 0.5 inch higher, the car understeered at exit but my turn in was great. Many factors could affect understeer/oversteer, it could be adjusted easily unless it is undrivable.
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Old 07-05-2019, 12:42 AM   #8 (permalink)
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Originally Posted by AlWakRa View Post
I went through their downforce guide and it is very helpful, I got convinced into getting only front splitter and rear wing for my planned aero, as they are the most simple and effective way to gain more/cleaner downforce.



and here is my car weight, very close to your car weight, but I think with half fuel tank.

( Click to show/hide )


Also, about spring rates, this is something I noticed when I got my mca reds, there was a big difference in front and rear, 21k/7k, when I had my rear height higher than fronts by around an inch, the car was nearly neutral, but when I tried with lower rear, around 0.5 inch higher, the car understeered at exit but my turn in was great. Many factors could affect understeer/oversteer, it could be adjusted easily unless it is undrivable.
Thanks for the information and yes Dan has been really helpful. I was only able to get one track day really with the true coilovers and it was kind of scary as I had two offs due oversteer. I could not trail brake because the rear end wanted to pass the front end as well. I don't know if I will end up as stiff as you are up front but probably pretty close to where you are in the rear. I generally run 0.5" of rake. It seems to work pretty well for me when go low with my ride height.
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Old 07-05-2019, 05:39 AM   #9 (permalink)
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http://www.the370z.com/members/2011-...e-install.html
~190 Driver. Full list of mods.

Best of luck to you! After reading a few books on suspension tuning and car setup I realized I was out of my league and would waste track time getting it right on my own and hired a professional shop for race cars.

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Old 07-05-2019, 08:21 AM   #10 (permalink)
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Quote:
Originally Posted by Hotrodz View Post
So I have been doing some research on adding a rear diffuser to my current setup when I ran across an article/blog on the Professional Awesome Racing website https://professionalawesome.com. After read their article on aero and downforce I decide to shoot them an email to see if their splitter diffuser would be a good addition to my front aero. Long story longer we have exchange sever emails regarding my aero and suspension most significantly my spring rates and the owner Dan O'Donnell provide me with the following information:

So you have a “true type” rear, meaning the spring is directly on the damper body, not in the stock bucket. This has the effect of dramatically increasing the “wheel rate” or effective spring rate at the wheel, if you are using the same spring rate you use previously. If you are running 14k front 12k rear or 800lbs front 700lbs rear, the car will oversteer badly. I just had a long discussion with Savanna Little and Kevin Parlett. They are using a “true type” design as well on similar chassis designs and no suspension manufacture compensates properly for the change.

With your rear wing, I think you can safely add our diffusers and vents, but I would really, really want you to change spring rates to a proper setup. Your system is borderline unsafe in my opinion. Let me know if you want to do the calculations to get the right springs in there. Quick math is lettings me like if you have 14k front springs, you need to be around 5-6k in the rear.

So I am prepared to pay for the his consulting fee as this a steep learning curve for me and at my soon to be power level I don't want to be wadding my car up or possibly hurting anyone else. Here is where I need some help as he needs some information from me to dial the best spring rates for the rear coilovers. I need to provide him with corner weights for the car and obviously right now I have no way to do so. He doesn't need to have actual numbers but just need to be in the ballpark. My car weighs about 3440 with me in it and I am 210 lbs. If any of you have corner weight numbers and your car is of similar weight I would greatly appreciate you providing them to me.

Thank you in advance and go check out the Professional Awesome Racing!

Cheers,
Bob

Legend. Thank you Bob for all your wisdom, and insight. The devil's in the details, and aero balance in our naturally neutral / oversteery cars is critical to safely turning quality laps.

Oscar
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Old 07-05-2019, 08:32 AM   #11 (permalink)
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With a true type rear suspension, it makes the motion ratio very close to 1 to 1. If you ran a 750lb/13k rear with the divorced set-up, that would put you at a natural frequency of about 2.00 hertz. If you were to then run that same spring with a true type rear, that bumps things up to over 3.00 hertz. Based on my calculator, you would need to go back down to 7-5k or 400lb to 300lb spring range if you wanted the rear to feel the same as when you were running the divorced set-up with 13k/750lb springs. I don't know how aero effects this as I have been focused on autocross, but I imagine you need to run on the stiffer end of the range since you have a force pushing down on the car.

I would love to see what he comes up with. Have my math checked so to speak.
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Old 07-05-2019, 08:49 AM   #12 (permalink)
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Quote:
Originally Posted by 2011 Nismo#91 View Post
http://www.the370z.com/members/2011-...e-install.html
~190 Driver. Full list of mods.

Best of luck to you! After reading a few books on suspension tuning and car setup I realized I was out of my league and would waste track time getting it right on my own and hired a professional shop for race cars.

Thanks bro I really appreciate your input. You have been very helpful here on the forum. I have found that I have reached my limit as well and there just are so many variables with suspension and aero once you move beyond the basic bolt ons.
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Old 07-05-2019, 09:01 AM   #13 (permalink)
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Originally Posted by Brendan View Post
With a true type rear suspension, it makes the motion ratio very close to 1 to 1. If you ran a 750lb/13k rear with the divorced set-up, that would put you at a natural frequency of about 2.00 hertz. If you were to then run that same spring with a true type rear, that bumps things up to over 3.00 hertz. Based on my calculator, you would need to go back down to 7-5k or 400lb to 300lb spring range if you wanted the rear to feel the same as when you were running the divorced set-up with 13k/750lb springs. I don't know how aero effects this as I have been focused on autocross, but I imagine you need to run on the stiffer end of the range since you have a force pushing down on the car.

I would love to see what he comes up with. Have my math checked so to speak.
Thanks you input as my friend as there is a lot experience on here singularly and collectively. I want to respect Dan's consulting and so I will let you know what he provides me given our agreement once I give him all the data he has requested. I will tell you this! Your calculations are totally in line with his rough estimate..."Quick math is lettings me like if you have 14k front springs, you need to be around 5-6k in the rear."

Cheers!
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Old 07-05-2019, 12:58 PM   #14 (permalink)
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Old 07-05-2019, 08:16 PM   #15 (permalink)
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I have that same book. Tell you how long that book has been around. I used it to set up my TransAm's back in the late 70's. Still have it.
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