Spec Boxster Build

[Greg Holmberg]

The PCA rules say: no urethane suspension bushings, all bushings must remain stock.

[thstone]

Parasitic power draw.

I typically don't drive the Boxster very often in between racing events so it can sit for up to 60 days without being driven. I've never used a battery tender and so I have always worried a little that the battery might run down while sitting for that long.

So, this evening I decided to figure out how long the battery should maintain enough charge to start the car.

I started by measuring the parasitic draw on the battery by placing a multimeter in series with the battery negative terminal (disconnect neg battery cable and place the positive probe on the neg battery terminal and the negative probe on the neg battery cable). This will measure the amount of current being drawn by the car. Car should be off with key removed and doors closed and so on - just like it would be if it were parked and locked.

I measured around 2mA and converted this to 0.002 Amps (x1000)

Then I looked up the "C10" capacity of my battery online which was 27Ah (amp hours). C10 means the "10-hour rating". Then I multiplied the 27Ah capacity by 30% to get 8.1Ah. This is how much battery capacity could be used by the car over time and still leave 70% of the battery capacity to ensure that the car will start.

Last, I divided 8.1 Ah of capacity by 0.002A to get 4,050 hours. This is how long it will take the car to draw down 30% of the battery capacity. Then I divided 4,050 hours by 24 hour/day to get 169 days.

Even if I am wrong by a factor of 100% (due to battery capacity variation with temperature, age of battery, poor battery cable resistance, etc), the battery should still start the car even after 84 days (169 divided by 2).

This is consistent with my experience that the car has always started in between events of up to 60 days.

Important Note: I measured 2mA for a Boxster that has been stripped of most electronic components. The only components in the car that might use power are the ECU and immobilizer. Thus, I would expect this value to be much higher for a stock Boxster.

And yes, this is what I do in my spare time after getting home from a 10-hour work day.

[Chuck W.]

My God... You lost me at, "I started by measuring the parasitic draw". Just get a Battery Tender and hook her up!!

[thstone]

Installed an Odyssey PC680 this morning!

Thanks to everyone for all of the advice about batteries. In the near term, I'll pull the battery disconnect after use and carry a portable jump station with me just to be sure.

PC680 (left) and PC925 (right) side by side. Quite a size and weight difference...


I found this mount for the PC680 online for $80. All of the parts are polished to a shiny chrome finish so I gave the top piece a couple of quick coats of black plastic-dip to minimize the bling factor (see pictures below)...


Removed the battery tray and attached the new mount by drilling appropriate holes and bolting from the bottom. The bolts that come with the mounting kit weren't long enough to reach thru both tray and mount. Problem easily solved with a quick run to the hardware store for a pair of longer bolts.


Mounted and ready for install...


Here is the final install...

[Greg Holmberg]

I found that hold-down here for $80.

There's also the aluminum box style for $26.

[thstone]

** Weight Update #6 **

Spec Boxster minimum weight with driver and fuel is 2,650 lbs. My goal is to be able to manage the weight of the car by adjusting the fuel load at the start of a race so I am near the min weight at the end of a race (with some margin for error).

At Laguna Seca, the total weight was 2,683 lbs with a 1/4 tank of gas. Subtracting 24 lbs for fuel (6 lbs/gallon x 4 gallons), says that the car/driver weighs 2,658 lbs.

With the battery change (-12 lbs) and a few other items (-5 lbs), the car should be down another 17lbs for a total car/driver weight of 2,641.

For now, I don't plan any more weight reduction until I get a weight check at the next race (POC AutoClub Speedway Sept 10-11).

[CrisZenithBlue]

Hi guys! Sorry to hijack the thread but who else than a knowledgeable group like you to help me with my little issue. I am the proud owner of a set of cloth GT3 seats for my Boxster (alien ones) and the Velcro on the seat base is worn and would not hold the cushion under the thigh in place. I see that the original Velcro strip is sown on so I am trying to figure out how can I replace it. Maybe some of you have had a similar issue and can help with some advice. Thanks! I can find sticky Velcro but that sticky part prob won't last long in cloth.

[steved0x]

Originally Posted by CrisZenithBlue

Hi guys! Sorry to hijack the thread but who else than a knowledgeable group like you to help me with my little issue. I am the proud owner of a set of cloth GT3 seats for my Boxster (alien ones) and the Velcro on the seat base is worn and would not hold the cushion under the thigh in place. I see that the original Velcro strip is sown on so I am trying to figure out how can I replace it. Maybe some of you have had a similar issue and can help with some advice. Thanks! I can find sticky Velcro but that sticky part prob won't last long in cloth.

On my driver seat (I have cloth Recaro seats too, not the GT3 seats but similar) the bottom of the seat cushion is worn where it attaches to the seat base Velcro, and when I have the sub belt running under that cushion and out the front of the seat, the seat cushion slips on the Velcro, because the cloth is worn where it sticks to the Velcro. In your case, if it is the driver seat, maybe swapping the driver and passenger seat cushion may provide some immediate relief.

The Velcro on the seat bottom is unfortunately not part of the removable seat cover:

Gt3 Bucket Seat Cover Perlon Velour

Hopefully some of this will give you some ideas...

[CrisZenithBlue]

Originally Posted by steved0x

On my driver seat (I have cloth Recaro seats too, not the GT3 seats but similar) the bottom of the seat cushion is worn where it attaches to the seat base Velcro, and when I have the sub belt running under that cushion and out the front of the seat, the seat cushion slips on the Velcro, because the cloth is worn where it sticks to the Velcro. In your case, if it is the driver seat, maybe swapping the driver and passenger seat cushion may provide some immediate relief.

The Velcro on the seat bottom is unfortunately not part of the removable seat cover:

Gt3 Bucket Seat Cover Perlon Velour

Hopefully some of this will give you some ideas...

Yeah I have exactly the same issue especially with the sub belt that came included. I think it's a combination of the Velcro and the cushion being worn and I already swapped the drivers seat but both are bad. Maybe there's something I can do about the Velcro but is ther any way to recondition the cushion cloth and not having to buy a new one?

[steved0x]

Originally Posted by CrisZenithBlue

Yeah I have exactly the same issue especially with the sub belt that came included. I think it's a combination of the Velcro and the cushion being worn and I already swapped the drivers seat but both are bad. Maybe there's something I can do about the Velcro but is ther any way to recondition the cushion cloth and not having to buy a new one?

I think the seat cushions (at least mine) have a Velcro flap so you can remove the foam cushion from inside. You could remove the cushion and then sew a piece of Velcro onto the seat cover that lines up with the Velcro on the seat base. I am looking into that because I don't want to swap my seat cushion (one seat is newer than the other and I want to keep the new cushion on the new seat )

If you do (or I do) we should make a DIY thread We have probably hijacked on this thread enough

[CrisZenithBlue]

That's is EXACTLY what I'm gonna do! Thanks Steve!

Sorry Tom

[thstone]

Originally Posted by CrisZenithBlue

Sorry Tom

No worry! I'm glad that people come here and ask other questions beyond what I post. At the end of the day, its all about the Boxster community!

[thstone]

New color for my second set of wheels!

[Need_for_speed]

Nice yellow! Not too garish. Will look great on a blue box. Plastidip?
Let us know how you like the Toyo's.

[thstone]

Originally Posted by Need_for_speed

Nice yellow! Not too garish. Will look great on a blue box. Plastidip?
Let us know how you like the Toyo's.

Professionally painted, not PlastiDip, so its somewhat of a commitment. I hope that I like the color on the car!

The Toyo RR's are the spec tire for Spec Boxster racing. Overall, I'd say that they are a good compromise between grip and longevity. Compared to a street tire, tons more grip but that comes at a price in longevity and they do fall off a bit after a number of heat cycles so most of the drivers at the front of the pack are running a new set every race weekend.

[thstone]

"Racing is life".

There is a lot of truth in that statement. Here are the ups and downs of racing last weekend;

On Friday, I attended the High Performance Driving University (HPDU) event as a practice day in prep for the weekend races and paid extra for professional coaching. HPDU keeps attendance low (40 or so drivers) and has open track all day (7 hours) so there are no run groups or sessions; you can go out as often and for as long as you like.

I did four 30 min sessions and reviewed video with the driving coach in-between sessions. The coaching was excellent! I often get to a point where I am not sure exactly what to try next to improve my lap times.

The coach worked with me to find three corners where he made suggestions on how to approach them differently with the ultimate goal of taking 0.3 sec off my time per corner. Three corners at 0.3 sec improvement would yield an overall improvement of about a second per lap.

Of course, this didn't happen in one day, I will have to continue to work at the new approach and perfect it - then it will hopefully yield the results that I am looking for.

I have video but I'm not going to post it quite yet for competitive reasons. Let's move onto Saturday...

[thstone]

Saturday started out great! I scrubbed in a set of new tires in the morning practice and then went out and qualified 2nd! I had a lot of anticipation for a good race.

Then I screwed up.

The weather was fairly hot in the afternoon so I set up my cool shirt system and when I filled the reservoir with ice and water, it seems that I forgot to strap it down. Fast forward a bit and when I hit the brakes for the first time on the out lap (before the race start), the cool shirt reservoir shoots across the passenger side like a rocket.

Oh crap. I can't start the race with the reservoir flying around every time that I accelerate, brake, or turn, so I pull off just before the start and hastily strap it down in the infield parking lot. While doing this, I hear the race start - and I'm not in it.

At this point, I'd like to reach around and kick myself in the ass, but you gotta let these things go and move on or you'll never get your head straight for the rest of the day. So, I pull back into the garage to wait for the second race on Saturday...

[thstone]

I have everything ready and double checked for the second race. Good to go.

I start dead last since I finished last in the first race. As we come to the starting line, I judge the timing right and get an awesome jump. As we go down the front straight and around the NASCAR banking, I pass almost all of the Boxsters. Then I carry that momentum into the infield where I pass a few more cars.

Then I screwed up.

At the Turn 9 buttonhook, the rear end loses traction and I don't catch it in time and and spin around. I don't hit anyone but I am looking at 1/2 of the field coming straight at me! Oh crap. Kudos to my competitors as they all swerve around me and get by safely. Now I am back in very last place.

I spin the car around in the right direction and give chase. Over the next 14 or so laps, I catch and pass 5 out of class cars and 2 Boxster's. I stayed focused and I think that might have been the best series of 14 laps that I have ever driven.

While I should have been down on myself for all of the self-inflicted mistakes, I felt good about hanging in there and recovering as best I could.

Onto Sunday...

[thstone]

I wake early at 3am on Sunday with a splitting headache, sore throat, and I'm sweating like I've just run a marathon despite it being 72F in my house. I'm sick.

I realize that there won't be any racing for me that day, so I turn off the alarm for 7am and sleep in until 9am. I spent all day Sunday and today either sleeping or laying on the couch feeling like crap.

What a weekend! Lots of ups and downs. I see moments of brilliance interspersed with major mistakes. I'll take the ups and work on eliminating the mistakes and be ready for the next race.

[thstone]

*** Weight Update #7 ***

After the race on Saturday, the total weight was 2,679 lbs - 29 lbs over the min weight of 2,650 lbs.

Subtracting 15 lbs for the cool shirt system, gives me 14 lbs over the min weight with 1/8 tank of fuel.

I am still working on losing 5 lbs more myself and another 5 lbs from the car. That will put me within 5lbs of the min weight with 1/8 tank of fuel at the end of a race. Perfect.