949 Racing project car - Blub

[949 Racing]

Quick update from Sonoma 86 Drive Challenge May 24-25, 2019:

Today (Friday) is a test day. Competition is Saturday. I'm at the shop, Sonny and Ed are there. Prelim feedback from revalve Xida protos is great. Sonny tells me they are unaffected by the kerbs there. The extreme nervousness it had on the stock shocks and RCE springs is gone. Indeed, it's very stable, progressive and easy to drive now. Some early session lap times. Keep in mind Sonny is still dialing in the setup (pressures, shocks settings, ride height, rake). It should get a bit faster as he gets pyrometer readings, can look at data and the track warms up.

1st session Friday
1:51.4 Nankang AR-1 255/40R17
1:52.2 Toyo R888R 255/40R17

I think it will dip under 1:50 by tomorrow afternoon. That's really quick for a stock block N/A anything on street tires.

245/40 Nexen's in the pic are for Ed (or sales manager) to drive on. Fastest tires are for Sonny and A/B tire testing while we are collecting data on the shocks.

[Clutch Dog]

Color me shocked by that grip of the nankang

[949 Racing]

Originally Posted by Clutch Dog

Color me shocked by that grip of the nankang

About what we expected. Delta came down to about 1s average after the AR-1 had a few heat cycles. Sonoma is a relatively short course so roughly 1.2s on a more typical 2:00 / 2.5 mile course.
_________

Sonny tells me the car was good right off the trailer. Just took pyrometer readings to dial in pressures on each tire but didn't touch spoiler, shock settings, sway bar, rake or ride height. Soaking up kerb hits with impunity. Huge difference to OEM there. Stable, easy to drive and balanced. We did the baseline tuning here at the shop and a few local roads. Made some significant changes to shock valving since we ran the first protos about a month ago. Track is a different environment though so always a bit nervous to see how our calcs will resolve at speed. Looks like we nailed it.

Today was open practice. Competition is tomorrow. We have a set of 245/40 A7's with a few heat cycles on them that should be 1~2s or so faster than the AR-1's. Hoping we can nip under 1:50. Next week we'll run it at Streets of Willow with the softer spring pack.

Spring packs not finalized yet but so far it's looking like 250/250 for the "GT" setup for slightly taller ride heights and either 500/500 or 550/550 for the "Race" spring pack. The Race spring pack will be able to tolerate slightly lower ride heights than the GT of course. Exact ride height recommendations/range TBD.

[949 Racing]

Final results after we equalized the number of heat cycles on each tire, back to back with same track conditions/car/driver/set up
Sonoma Raceway 5/24/19 ambient temps ~68°
Both 255/40R17 on 17x9 6UL +40

1:51.716 Nankang AR-1
1:52.974 Toyo R888R

Before you ask pressures, understand that we set each individual tire pressure based on pyrometer readings. So each tire is likely different than the others on the car. Ambient temp changes, pressures change. Take a passenger, pressures change. Sun goes behind clouds, pressures change.

The R888R has a relatively soft sidewall. This made for very vague steering. Probably the most vague steering I have ever experienced in a 100tw "race" tire. This also allowed more yaw angle when the rear would finally step out. In contrast, the AR-1 steered much more crisply. Perhaps not as crisp as an RE71R, but close. When the AR-1 did let go, it would yaw less and be more controllable.

No real data on how the AR-1 cycles or how long it might last yet as this is only our first day on them. Reports from other testers indicate it may not be a particularly long lasting tire for a 100. RC-1 usually wins that contest anyway. What the AR-1 appears to be, is the fastest current 100tw tire sold in North America, which is why we will run them. 86 Cup TT rules favor a 100tw over the faster "Super200" tires like the A052, RE71R and Rival-S.

[extrashaky]

But the real question on everyone's mind:

How'd that steering spacer work out?

[Clutch Dog]

Originally Posted by 949 Racing

A
Spring packs not finalized yet but so far it's looking like 250/250 for the "GT" setup for slightly taller ride heights and either 500/500 or 550/550 for the "Race" spring pack. The Race spring pack will be able to tolerate slightly lower ride heights than the GT of course. Exact ride height recommendations/range TBD.

If i have any vote on ride height, id ask for lower than stock but only just so..

with the swift lowering springs and the sti lip im suddenly super concerned with the roads and getting into driveways.

Also about the rates I am interested as to the reason for even rates. personally I opted for the swift spec -r due to the off the shelf nature and having a slightly higher rear spring rate. of course this harkens back to the intended use which is auto-x so you want a more "squirrely'' rear to get the car to rotate more, which is the exact opposite of whats better for open track days. You want a car to be easier to drive or "more comfortable"

so far Im liking what you are putting out also.. that wing is awesome

[949 Racing]

Originally Posted by Clutch Dog

If i have any vote on ride height, id ask for lower than stock but only just so..

Also about the rates I am interested as to the reason for even rates.

The OEM shocks have very limited bump travel even on stock springs. This is why most aftermarket lowering springs are so prone to bottoming if they are say, 1.5" below OEM. Many OTS (Off The Shelf) coilover kits we have seen also have less bump travel than OEM. The RCE yellow springs resist bottoming by being a tad higher rate and taller than other kits while also including shorter bump stops. Managing bump travel and behavior is absolutely critical for best performance on track and ride quality on the street. No matter how nice the damping or perfect the spring rates, bad bottoming behavior make for an unpredictable and uncomfortable car.

The Xidas are not exactly OEM length but match OEM stroke. Both front and rear are adjustable for effective length so they can be fine tuned to get every last mm of available bump travel without sacrificing stroke. We don't recommend running really low ride heights though. Being a strut front, the RC (Roll Center) drops too low when the car is slammed. The rear, being a multi link, drops RC less for the same ride height change. So running a strut/ multi-link cars too low adds significant rake to the RCA (Roll Center Axis). This is a bad thing. We run the Whiteline front RC correction kit to keep the RCA as close to OEM as possible and also limit how low we run in general. At Sonoma, I think we were about 25mm lower than stock, which might appear lower because of the taller-than-OEM tires filling the wheel wells a bit more.

Most track rats will run 255/40R17 which are much taller and wider than OEM, meaning even less bump travel available.

Every individual daily driver has a speed bump or driveway they need to negotiate. Those specific obstacles will dictate the "perfect" ride height for them. On track, ride height becomes a question of the RM (Roll Moment) generated from tire grip vs weight with driver vs track surface and kerbs. So there is no "perfect" ride height for everyone and every track.

In summary, we are engineering a total ride height adjustment range based solely on functionality. Some folks have steep driveways on stock size tires, others run Hoosiers with 400whp and trailer their cars to the track.

You ask for reasoning behind our spring rate selection. My answer is that, as stated earlier, the rates we are testing now are preliminary. Not final. But in the end, we simply use what works best in testing.

[Pat]

Why does tire size determine how much bump travel is available?

[949 Racing]

Originally Posted by Pat

Why does tire size determine how much bump travel is available?

Height and width. Taller tire hits stuff sooner than shorter tire. Wider tire hits different stuff sooner.
If the shock has optimized bump travel for the taller, wider tire, then it will have unused travel on shorter or narrower tire.

Other factor is camber. The driver that runs a 300tw 225/45R17 on a 17x8 isn't running race camber. More like -1.5°. The other driver with 255/40R17 on 17x9 might be running -3.5° camber. Inner clearance totally different. Shock package needs to accommodate both drivers.

[86_IT]

After riding with Sonny on Sunday I can confidently say that the Xidas are well on their way to being (if not already) the nicest track suspension I've felt for the platform. The way they soak up the kerbs, control lateral body movements in transitional corners and ride like a Cadillac on the straights has me thoroughly impressed. I and many of our competitors in 86DRIVE Challenge currently run Tein SRCs and, if pricing is similar to the Miata stuff, these are half the price for a very impressive package. I cant wait to see the final results of the testing! These will be tough to beat.

[SonnyMod]

I will give a proper debrief back to 949 Racing tomorrow about the new settings with tire testing and 86 XIDA protoypes, but here's the video for now.

New 86Drive Challenge Touring class record. I also set a new N/A 86 record on Friday 5/24, 1:51.4 with the Nankang AR-1 not optimized (1st guess), with similar ambient temps as Saturday competition, but calm winds and cloudy skies.

[ame]https://www.youtube.com/watch?v=S6y5M-43iug[/ame]

Notes post-data analysis of video:

Session 2, lap 2 (1:51.546) is the fastest competition lap for both SpeedSF S3 class and 86Drive Challenge. Lap 6 was on pace for potential 1:51.1 up to T10. A bobble at the apex, brief throttle lift, and two wheels off in the exit cost 0.2s; traffic at T11 cost another 0.2s.

[AngelGT86Racer]

Originally Posted by 949 Racing

The Xidas are not exactly OEM length but match OEM stroke. Both front and rear are adjustable for effective length so they can be fine tuned to get every last mm of available bump travel without sacrificing stroke.

Interesting. If I'm understanding correctly, the rear shock bodies will have some length adjustment as well? From the first image from a month or so ago it was clear the front has the adjustable strut flange, but the rear looked like the standard SLA style shock with a fixed length.

[949 Racing]

Originally Posted by AngelGT86Racer

Interesting. If I'm understanding correctly, the rear shock bodies will have some length adjustment as well? From the first image from a month or so ago it was clear the front has the adjustable strut flange, but the rear looked like the standard SLA style shock with a fixed length.

Rear 86 shock is fixed length. My mistake.

We are developing shocks for the S550 Mustang at the same time. Those have a proprietary body mount that has several mounting heights. I got the two projects mixed up.

Bump travel in the rear of the 86 is more limited by control arm kinematics and brake hardware than tire clearance. So we can use a fixed length that will work for a variety of tire heights/ widths. Up front, tire clearance is primary limiting factor, thus the special effort to provide some length adjustment.

As a side note from development, we have gained some really useful bump travel up front. Even with only 250# front springs, it's near impossible to bottom the front suspension unless you basically jump the car or ram it into a huge drainage dip. This at 150mm front pinch weld height, which is fairly low. Still dialing in rear springs rates and bump stops to get the ride quality we want for street use. It's funny, setting up for track is relatively easy. Getting some plushness for daily driving on skinny tires is always challenging when we develop a Xida package.

[AngelGT86Racer]

Yeah the S550 rear geometry is quite different from my observation(separate shock/spring, inboard spring, outboard shock). From my recollection the 5/6th gen Camaros are similar.


As for the 86, bump travel is definitely at a premium which was why I refrained from getting lowering springs. Even on stock springs and PP shocks, I still get a decent amount of vertical oscillation on long sweepers like Riverside where it's bumpy. My main complaint, though, is that like with many Japanese cars, the shocks feel overdamped on smaller/medium imperfections and quite busy. Having the ability to calm down the high speed a little bit would be great for that.

My friend's NB with 550/350 Xidas definitely has a nicer ride quality.


I've no doubt you guys will come up with a competent package for dual duty use.