PBIR coilover suspension testing

[Siestarider]

Track: Palm Beach International
Organizer: Hooked on Driving
Date: 1/8/17
Weather: 60's, fair sky, wind N at 25 (coldest day of year so far)

Of Interest: This trackday started at noon and went into evening, part of an event I had not previously attended called Supercar Week. I ran intermediate group, next slowest car was a Cayman S in racing trim. 30 min sessions. Giving a point by to a Porsche 918 spyder was a new experience. So was getting one from a brand new 911 S. Mercedes AMG and Rennsports like litter. Italia, R8, a C-7 corvette that looked out of place, and me. I have never tracked with that much new car value around me. Really rich folks are not that fun to chat with when a Fiesta is keeping up with them on track. Even on track. I gave the 918 a second point by on front straight during 3rd session and he was so desperate to get by me and back on racing line he overcooked the approach to Turn 1 and had to run the escape road. Honestly I did not think I needed to lift for a 918.

Enough gossip.

I ran this day to test MeisterR GT 1 coils on 5/3 springs. Almost 1" lowered from stock, front camber -1.5 was most I could get until alignment and notching strut towers to get -2.3, which is what I ran. Since I have laps recorded on BFG SC-2, I used same tires but in 17" instead of 16", even worn similarly. Only other change in car from comparison laps reported here is I changed out the MBRP 3" for a Mountune 2.5". Otherwise, same. So its as fair an OEM to coils comparison I could achieve.

Per Jerrick I started with -5 clicks from full hard and dropped -7 front and -5 rear each session. Had to remove hydraulic fluid reservoir to reach left side damper adjustment, rest were reachable. Cold tire pressures 37 F and 34 R. I should have started at 35/32. Also, these tests run on 205/40/17 tires.

I have looked at all the hot laps (36) and broken down by lap time and sector time per damper setting.

Initial setting -5 F and -5 Rear: best lap 1:45.9 Best virtual lap that session 1:44.6
-12 F and -10 R: best lap 1:44.0 Best virtual lap that session 1:44.0
-19 F and -15 R: best lap 1:44.1 Best virtual lap that session 1:43.6

Personal best on BFG SC-2 205/45/16 1:43.1.

I would normally have reduced hot tire pressures (as high as 47 psi) by about 5 lbs but that would have been another variable, did not want to change anything else.

My observations are: temps across tires became more stable as I reduced damper settings, too much data to post, and I could not get off track and into pits fast enough to get pyrometer data better than just comparisons across tire tread (inside, middle, outside).

First session with hardest dampers car presented excessive oversteer. That calmed down as settings were reduced. Note final settings were about 60% from hard F and 75% from hard R.

I could have run one more session after dark, but decided it was not worth waiting 2 hours for.

I admit being surprised the $2300 in dampers springs and alignment did not make a measurable improvement on track compared to OEM on same tires. Part is me, I would have reduced tire pressures and made larger steps in damper adjustment were it not a controlled experiment. So I have no doubt I could break 1:43 with this setup. But silver bullet? No, not for me.

 

[milkman42]

looking forward to the report. you should note that you're not using the ZRD+ (IIRC)

 

[Siestarider]

looking forward to the report. you should note that you're not using the ZRD+ (IIRC)

I just edited the thread to include as much data as I could reasonably post.

Now that I have a couple days perspective, plus notes reviewed, plus clean shorts, I would add couple observations.

As I reduced damper stiffness I gained "happier" tires as measured by temps across tread and hot pressures. Again, what surprised me was how good the OEM suspension is on track keeping tires relatively happy, I have lots of data on stock suspension.

My last lap of third session, I went full throttle from apex of turn 5 onto line into 6. With OEM suspension I had no problem with this, done it many times. With more front traction (dusk, outside edge of track not very visible looking west into the sunset) I drifted outside wheels barely into dirt on runout from 5.

Result was a horrifying snap spin, the concrete wall inside turn 5 flashed across view and one thought: This is going to hurt. Then both feet in.

I ended up facing traffic on the inside of track less than 6' from wall, having backed along inside green lane about 150' from point I lost it. Harry's LT says I was doing about 65 when I dropped the rear wheel off track.

Memo to me is to be more cautious at dusk. I know better. But for all of us, as tires get happier they put you into new situations because you have more traction, and best to be more cautious than I was. Special note: FWD cars punish you when you are drifting and lift, called lift oversteer. I did not lift, but dropping a rear wheel off pavement apparently does the same thing only faster.

Only damage was both rim/tire beads full of grass on drivers side. I made it home but tires leaked down over night. Probably used up the whole seasons' worth of good luck.

 

[Crooked Letta]

Depending where your limits are is where you will gain the most. A damper change won't give the same results as a tire change, but if you are running on something like R comps it can be a decent bump. You kind of went a little technical in your reviews which is good, but the primary purpose of a damper is control. I would love to here more about how it made the car feel? Was it more controllable? Did it handle bumps or curbs better? It sounds like you need to work out a little fine tuning as your still finding the sweet spot though.

 

[Siestarider]

Depending where your limits are is where you will gain the most. A damper change won't give the same results as a tire change, but if you are running on something like R comps it can be a decent bump. You kind of went a little technical in your reviews which is good, but the primary purpose of a damper is control. I would love to here more about how it made the car feel? Was it more controllable? Did it handle bumps or curbs better? It sounds like you need to work out a little fine tuning as your still finding the sweet spot though.

Car rides better on the 5/3 springs, which seems strange to me given these are stiffer than OEM. I am generally running on the high side of desirable slip angle on track, just love to drift. I agree my post is too technical.

I put the report together to get an objective comparison between OEM and coilovers using lap times at the limit as the metric. I just do not trust my butt dyno to tell me the truth.

My general impression is on this particular track, which is very smooth, even less damping may decrease lap times further. However, I need more time to feel out where traction is being maximized at expense of control.

Sebring will be a different experiment. The three most important turns there are on concrete remnants of WWII air base. Rough. My notes from first day there two years ago say I would not want stiffer suspension than OEM. Next trip there I will use 205/45/16 Rival S. Rivals are about 2 sec a lap quicker than SC-2's at PBIR on OEM suspension. I have found it difficult to get a clean lap at Sebring, too many cars and not enough point by's. It can even be tough to get a clean sector time.

 

[Brick]

Thanks [MENTION=1391]Siestarider[/MENTION] for the detailed report. Love the analysis. Interesting that you didn't see better lap times.

 

[Siestarider]

Thanks [MENTION=1391]Siestarider[/MENTION] for the detailed report. Love the analysis. Interesting that you didn't see better lap times.

Car "felt" better except on hardest dampers with excess oversteer. It also feels better on street. Lap times don't have feelings, or know how much money was spent.

I am confident I could set a new PB with these coils, but Crookedleta said, tires are the cost-effective way to lower lap times when you know how to drive. That said, there are some finer points of driving to learn with new coils, and I did not give myself a chance to learn them because of the experimental changes every session.

 

[MeisterR]

Just saw this and I'll note in the reason.

One of the reason was because the damper is setup for a different springs rate.
Under request, the damper was setup for 6kg/mm front, 4kg/mm rear.

What that mean is when you go full stiff on those damper, you are over dampening the system.
This stop the suspension from moving within it's natural frequency, and chances are taking away grip.
That is why on that full stiff setting, the car don't want to behave.

Once you dial it down a bit more, the car should become much better behave as the suspension will start to move and allow the tires to find grip.

Again, I am here both as a provider as well as technical support.
If you have a questions, just drop me a message. I am always happy to help.

Jerrick