Modern car like Rx8 & S2000 without EBS, really Handelful

 

Cute story

 

Sounds like a pain in the butt to race this platform in that series having to keep the renesis and the inability to shed the weight.

 

Story of race

I think most issue is No EBS ABS !!!
This is what separate modern cAr and old school race car ......
Come from Rx7 race car background I was very impress Rx8 brake performance

 

Evil oversteer at the limit. Yep. That matches my experience. You have to keep it unusually high, and it wants a lot of rear spring, plus 1.5x that in the front. Agreed on all points.

 

pretty much the opposite what most people are doing and it’s a exponential calculation function so a simple linear multiplier is the absolutely wrong way to address it. I’m only aware of one person on this forum proposing high rates overall, especially in the rear.

 

it's pretty much common knowledge that if you disable the ABS on any car, you'd need to add some type of proportional valving to control bias. nothing new there, i would never attempt to drive a car on track with a disabled ABS, unless it was properly converted to non ABS. a lack of rear wing for his class probably didnt help with the oversteer. to me, a stiffer rear end should make a car rotate more. maybe there's some weird geometry going on under rear compression that add a lot of bump steer. i haven't experiment with changing rear setup around. Eric Meyer told me that he used to run the rear ride height much lower than the front. i havent tried that yet neither. my car currently has a slight push at high speed corner entry, and neutral at exit. i can do some trail braking to remedy that. i can also add a splitter but then i would have to take out some power or add weight. in low speed corners, the car does rotate nicely on entry, which sets the car up for a good exit. the OSG diff rotate the car very good on corner exit.

i opened the stock diff last week and was surprise that it's just an open diff with a spring in the middle to give some resistance between the sun gears. i thought it was going to be torsen diff but it wasn't. that might help in snow or wet condition but that's about it. any type of performance driving in the dry and it's useless.

 

Stock Rx8 LSD
Is call super lsd
Mazda change the design at end of NB Miata
From Torsen lsd
This type of some pre lock like clutch type
So act like clutch type can lock the wheel even one is on air
But only 20% torque bias ratio ,
Stock Torsen LSD from Rx7 offer much better lock ratio 40%+ but can be hever
I swap it stock one to Rx7 when I change ton4.777

 

Nope, not a Torsen. Been discussed here before.

Same for the ABS delete.

While ok for a street car, those OE LSDs are not that great of a design, especially for track use. An OS Giken will be a much better choice. Some people are running it as a 1-way similar to OE, but I still haven’t seen any need to do that. Not saying it’s wrong though, just a different way to skin the setup cat.

 

I've experienced the evil oversteer. It took me about a year to regain my confidence after I fixed it. I believe it is related to running out of shock travel, which kinda correlates to the need of running higher than expected spring rates in the rear.

 

What shock/coilover setup were you running when you experienced the evil oversteer?

 

He has the inverted Koni 2812 setup, which is a true coilover in the rear.

Which I also had similar, but am now transitioning to inverted rear MCS setup.

.

 

As Team said, inverted Koni 2812LB in the rear. "Ziptie-around-the-shaft" confirmed I was running out of shock travel. I don't have solid mounts in the rear, so I made a thin poly bushing set that effectively moves the shock up.

 

Sounds like I need to make two sets of modified rear mounts then. That bushing setup has to be side loading the piston/shaft/shaft seal. Thin stiff bushings only make it worse.

you might potentially be running too low of ride height also. The rear starts getting some really crazy camber gain past a certain point. I seem to recall it was at about 10” or 10.5” from the axle center to fender lip height that it doesn’t make sense to go beyond.

 

Curious what spring rates you run.
i was thinking my 700/500 choice was good from using calculators. The dude in this video sounds like he's running about the same rate front/rear.

​​​​​​

 

Last setup I used was 600/450 on 225/45/17 Hoosier R7

 

Sounds about right for skinny, track compound tires likely no aero either

It’s not a “one size fits all” situation. Those can be considered semi-stiff street rates in some instances. More details are needed. For me 700/500 is a bit too much gap, but it just depends.

 

Was just trying to keep the bounce frequency down.
Once I get my post count up I'll start a thread on my car.

Interesting info and good video though

 

That’s for a luxury car. No need to care about that with what you’re doing. You’d have to run even way softer than that in the rear to have any meaningful BF effect. In the other thread you posted 700/550 which is closer to the 13k/10k rate I’d think of in that range for a typical Renesis setup, but you’ll have the V6 in there instead. I think you made a good choice on the MCS shocks too.

 

225/45/17 R7 tread width is 9.3”... my mistake was using 17x8” wheels.

 

MCS is good stuff, I thought about going with feal as a cheaper option but was worried I'd end up getting MCs anyways and wasting money.

I read from multiple sources that are probably dated now but they advocated 2.5hz in the rear and 10th less in the front unless aero was involved is a very good starting point. I was still working around that for a starting point.

 

Oh ok, your BF terminology through me off because most engineers are not referring to that using the term bounce, though there is an archaic method for determining it by physically bouncing an undamped chassis. The actual line on where to draw that is opinion based and relative to many factors. If you study the history of it you’ll see that it was developed back when street tires weren’t necessarily as advance in structure or grip as they are now, but of course nobody ever considers that sort of thing. They just read it as gospel.

Which some people advocate running that same type of tire up in the higher 2.x range. There are many variables including your skill and overall setup, track conditions, and so on. My own experience on this chassis is that the f/r rate ratio is in general going to be closer together on the low end of the range and then starting spreading apart at higher rates. If you don’t want to exceed 500 lb/in in the rear you need to consider bringing your front rate down, and then balance it out with the ARBs.

In general though, as you get closer to that line of maximum grip, how finely tuned both your skill level and setup are will come into play. Because sloppy inputs and bad setups are going to show up more readily then and can be interpreted as too much spring when that’s not actually the case. Stated frankly, in that situation mediocre optimization may be better suited to mediocre skill and setup.