Driving Impressions: Lower Stress Bar

[insite]

Originally Posted by BobMarley1

how do I order one?

their website is here: http://www.mantissport.ca/

you can't order online, though. call them at 905.844.6219 and ask for stan. btw, any prices listed on their site are canadian.

[insite]

for those interested, here is a graph of my fastest lap showing lateral acceleration derived two different ways:

1. on board accelerometers (red line)
2. calculated from GPS polling data (green line)

the RacePak polls gps several times a second. there is some latency and interpolation. this is why the green line lags the red line by a little bit. magnitude, though, is very comparable between the two. the data is accurate.

[racer_d]

Interesting discovery. Reminds me of the problems I had with my 914 experiencing trailing arm flex under high g loading (expecially with wide sticky tires, compared to the then stock, skinny, non grippy ones )

I'll have to keep this mod in mind. Wonder how SCCA/PCA allows it for, say, Autocrossing?

[insite]

Originally Posted by racer_d

I'll have to keep this mod in mind. Wonder how SCCA/PCA allows it for, say, Autocrossing?

good question. i bet it falls into the same category as a strut tower brace. probably would bump you from showroom stock to production, but not from production to improved. just a guess.

[John V]

Magazines measure maximum lateral acceleration around a flat skidpad. They drive the car at a known radius and then measure time to complete a lap (or multiple laps). Then they calculate the lateral g's generated.

The maximum g's that a car can develop steady-state around a 200' skidpad is different than what it can generate around a banked corner. Or a corner that requires less steering lock. Or at high speeds. There are too many variables, which is why magazine test numbers are for the most part useless metrics.

Another discrepancy can come as a result of the leaning of the car, which induces a false lateral acceleration component. Fortunately, the more sophisticated data acquisition systems account for this with multiple accelerometers.

In other words - I believe your numbers. We see similar numbers in our DL1 data - peaks of up to 1.4g lateral but more imporantly, around 1.2g steady state. This is a stock-class Boxster S with (really old) Kumho V710 competition tires.

[chaudanova]

Insite, any updates on your lower stress bar, in terms of how its been holding up, any changes/updates on driving impressions on both street/track?

Thanks bud...

[insite]

it's still awesome. unnoticable under normal driving conditions. very noticable when you push the car, especially over bumps. without the bar, the car will lose camber over bumps, causing oversteer conditions. with the bar, things are much more tidy. i really recommend this.

[Topless]

Nice work Insite,

You patiently seek out leading edge performance upgrades, act as test pilot, verify your impressions with instrumentation and lap times and share your findings with all of us. Bravo!

This is not bolt on fluff, but tested and verified with results. 2.5 sec on a track you already have wired is pretty good stuff. Just for kicks, if you had not made these improvements to your suspension and braking and focused only on the motor, how much HP increase would you need to get the same lap times? 50? 80? Interesting question don't you think? I suspect you are already outrunning most of the 987's in your area with a stock 2.5 motor.

Thank you again for sharing your findings.

[insite]

Originally Posted by Topless

Nice work Insite,

You patiently seek out leading edge performance upgrades, act as test pilot, verify your impressions with instrumentation and lap times and share your findings with all of us. Bravo!

This is not bolt on fluff, but tested and verified with results. 2.5 sec on a track you already have wired is pretty good stuff. Just for kicks, if you had not made these improvements to your suspension and braking and focused only on the motor, how much HP increase would you need to get the same lap times? 50? 80? Interesting question don't you think? I suspect you are already outrunning most of the 987's in your area with a stock 2.5 motor.

thanks for the kind words. for those reading this, i'd say that maybe .75 seconds was from the stress bar. another .75 was shocks. the final second was all brakes. either way, measurable gains.

to put the lap times in perspective, this was faster than the other boxsters, 996, a 928 race car (2700lb / 400HP), a 928 twin-screw (550HP), etc. i have a buddy with a tricked out '99 box that has a 3.2 in it. on street tires, he ran a 1:14.5. on race tires, he ran a 1:11.7. with my stock motor, i ran a 1:12.7 on street tires. not bad!

this chassis is really getting well developed. it's retarded, stupid fast in corners now. with the brakes, it's just patently absurd. now i need just a LITTLE power......

[MartinJ]

Installed mine on Sunday, and took a spirited ride on some twisty Northern CA Mountain roads (they are very empty this time of year) that I am very familiar with. I did not drive the way I drive at an AutoX or on the track but I was able to tell the difference on some fast turns. On my spirited runs I usually push the car enough to get a little “rear end hop” as I accelerate out of a tight turn, driving the same way Sunday the car did not hop and definitely felt more planted. Of course there are many other variables at work (temps in the low 50s…) but I expect that track and AutoX experience will improve. Looking at the rear tires afterwards I could tell that they did not get as far over onto the edges as usual so I expect that I will be able to lower the tire pressure 1 or 2 lbs on the track and AutoX to get a little more grip (I will need to get the chalk out). I run PS2s on 19s” with 36psi in back and 34psi in front.

I have a 987S (the brace is 3mm shorter than the 986 version, so make sure you get the right one) the install is very simple (just follow the instructions), I did not need to remove or loosen anything other than the bolts that hold it in place, the longest part of the process was jacking up the car and putting it up on jack stands! The brace was well made and fitted perfectly – Thanks Pedro