Autocross discussion #2 - 986 Boxster S in C Street versus the ND Miata?

I am still looking at the G Street Cobalt SS/SC, but I found a local car that might work for this hypothetical. The 986 generation Boxster S got sent all the way down to C Street, this is the car that won Super Street in what, 99 or 00? The ND Miata is basically the spec CS car, but I think the 986S might have a shot and here's why.

The ND is super light at 2332 lbs with 155HP but the 986S is 2855 lbs with 250HP. The Boxster out-accelerates the ND in 0-30 (2.0 vs 2.1) and 0-60 (5.7 vs 6.3) and let's remember that those tests were done on 2000 tires, not the sticky stuff we have in 2018. The vintage 986S road tests quote a 0.94G skid pad and 68.1 MPH through the slalom (0.93 G and 68.5 MPH for the ND). 

All well and good, but let's apply that to Street class autocross rule sets and courses. The Boxster could be individually optioned with 18x7.5/18x9 wheels (code 415 or 413) allowing a lot more tire than the Miata's 17x7. The Boxster came with a very large and heavy "can" rear muffler/exhaust that aftermarket versions commonly take 25Lbs off of and there's other weight savings available as almost every option was individual. The 030 or X74 option package featured 10mm shorter suspension with stiffer springs and shocks and larger sway bars. I think a "base" 986S with those 2 options only could actually be a competitive car based on power/acceleration and tire patch/grip. The Boxster should also out-brake the ND (318/299mm vented discs with 4-pot calipers f&r versus 280/280 vent/solid with 2-pot/1-pot). The ND will probably transition better and steady-state at a higher speed because of the weight, width, and shorter turning circle. 

Could a 986S actually give the ND a run for it's money? Thoughts? Better or worse idea than the Cobalt SS/SC in G Street? 

I've been curious about this also.

Now, factor in the new higher redline and power level of the 2019 ND...

What's the tire situation for those Boxster wheels? (I know that I should know this, but we're about to sit down for dinner.)

Keith Tanner said:

Now, factor in the new higher redline and power level of the 2019 ND...

Didn't the SEB recommend to not class the ND2 Miata for 2019? The letters focused on sending it up to B Street.

David S. Wallens said:

What's the tire situation for those Boxster wheels? (I know that I should know this, but we're about to sit down for dinner.)

Well the "best" tire (Bridgestone RE-71R) is available in the stock 225/40 and 265/35 sizes. There is also a 235/40 and 255/35 for the front and 275/35 and 285/30 for the rears sticking with ~25" height and 18" wheels. I think the ND guys are maxing out at 245/40 on 17's because of the 24" height and 7" width wheel.

I think Danny Shields lost his crazy win streak last weekend by .1 of a sec in the florida state champs to a ND miata, he was driving a Boxster S I recall.

Javelin said:

Keith Tanner said:

Now, factor in the new higher redline and power level of the 2019 ND...

Didn't the SEB recommend to not class the ND2 Miata for 2019? The letters focused on sending it up to B Street.

IIRC it stayed in CS, but I'll let others confirm. 

Keith Tanner said:

Javelin said:

Keith Tanner said:

Now, factor in the new higher redline and power level of the 2019 ND...

Didn't the SEB recommend to not class the ND2 Miata for 2019? The letters focused on sending it up to B Street.

IIRC it stayed in CS, but I'll let others confirm. 

Well crap. The 10/4/18 SoloMatters reported that the SEB declined classing the ND2 in Street Touring. It is classed in C Street for 2019. That is a tougher hill to climb, though all the power is up top and the 986S doesn't fuel cut until 7200 RPMs itself...

It's not just a higher redline and "more power up top", it's more power right in the middle of autox speeds. The ND1 redline with 245/40-17s is 56.6 mph, the ND2 is 64.3 - and it's building power the entire time between those two speeds.

What is the weight distribution of the two cars?  I think the mid-engine car will transition much more quickly.  Also, the Boxster will be able to apply power earlier on corner exit.

Keith Tanner said:

It's not just a higher redline and "more power up top", it's more power right in the middle of autox speeds. The ND1 redline with 245/40-17s is 56.6 mph, the ND2 is 64.3 - and it's building power the entire time between those two speeds.

Wow, the SCCA really screwed the ND1 guys by not putting the ND2 in BS. That being said, the 986S tops out at 71 MPH in 2nd. (2.20 trans gear, 3.444:1 final drive, 265/30/18 tire, 7200RPM redline)

Have we actually confirmed that the ND2 is wailing on the ND1? On paper it should matter more the longer and more nationally the courses are, but I'm not 100% convinced it really matters to the small local lot guys. 

I can guarantee that the 986s doesn’t have a chance against the nd2. Simply because there is no way the Scca would have classed an old p car competitively in a class that is packed full of miatas. 

mazdeuce - Seth said:

Have we actually confirmed that the ND2 is wailing on the ND1? On paper it should matter more the longer and more nationally the courses are, but I'm not 100% convinced it really matters to the small local lot guys. 

That's the same reasoning the CS FB group keeps coming up with so they don't have to buy new cars  The way I look at it is: the ND2 will never be slower than the ND1, and if you get a chance to get over 51 mph (where the ND1 power starts to fall off and the dyno graphs separate), it'll be faster.

I can see how the Boxster would have an advantage getting its butt off the corners. It has a significant weight disadvantage, though. What's the torque curve look like?

Keith Tanner said:

I can see how the Boxster would have an advantage getting its butt off the corners. It has a significant weight disadvantage, though. What's the torque curve look like?

Porsche says "85% of peak torque by 2000 RPM" in the ad copy, and it's official rating is 225 FtLbs @4500 RPM, so carry the 1...  and we get 191 FtLbs @2000 RPM, which is significant. The ad copy also states a 47/53 weight distribution. I'm not so sure the weight disadvantage is as big as it seems on paper. There's basically no weight to lose out of the ND's 2332 Lbs, yet the Boxster can take out the big spare tire from the nose, all of the factory carpet floor mats and trunk mats, and has a huge and heavy muffler that can be replaced in CS trim. I keep trying to find info from people who have actually weighed their Boxsters and there's not much out there. There's this guy with mods at 2786 minus driver with a 1/4 tank of gas. Take out his roll bar, LSD, and Accusump and that might be close to real racing curb weight, so maybe 2750 in the real world?

I can't speak for the performance of the Miata but I did seriously autocross a 2004 Base Boxster for a few years. My wife and I had some great results in A-stock at Nationals in 2009, beating out a lot of S2000's and 350Z then the car was moved to C-Stock in 2010 where I was in the trophies and my wife lost CSL by .001 seconds over 2 days. That was on R-comps and we always wished there was a good street tire class for the car because it actually was a better performer on street tires. On R-Comps it pulled so many G's on those 285 section tires (on all 4 corners) that it could lift and spin the inside rear tire. On street tires this was never an issue and we could accelerate so hard off the line and out of corners that we routinely got FTD at local events on Bridgestone RE-11's. It was a Base Boxster, I imagine an S would be even better. The 996 GT-3 front sway bar bolts right on and helps keep the rear tires planted.

I think it's a great idea. Do it and show us how it's done.

In reply to loosecannon :

Dude, thank you! That's the kind of super-valuable info that's hard to find.

dculberson said:

I think it's a great idea. Do it and show us how it's done.

I'm looking at a local one. 138K miles but new transaxle and clutch @133K, IMS has been done, and it has records for all of it. Already has the optional 18's and nearly no other options at all. It's cheaper to buy than to fix all the crap wrong with the Cobra to make it autocross well. (I won the regional season championship in CAM over Dennis Healy but only because his car was broken more than mine, I got hammered at the ProSolo.)

I started typing and missed you found the fastrack where they classed the ND2 in CS, but figured i'd also add what went out in an email in october ahead of the fastrack. 

ND2 was put into CS for 2019, but held from ST classes for at least 12 months. SEB/SAC reasoning being that 3 years is a normal cycle for cars to get updated in and protecting the ND1 is not a good reason to put the ND2 in BS. STAC wants to monitor the car and see what the potential is of the motor is before shoving it in STR, the class just got royally screwed by the ND1 as it is. STAC wants to avoid the constant turmoil that lives in street class. 

ND2 vs ND1, I'm in the same C street group Keith is and I agree with the thoughts of people there. If you run big wide open national level/size courses, the extra revs matter, but if people only play on a local level only and/or on only smaller courses, that they should stick with their ND1 for now and not focus on moving to the ND2 immediately unless they really want to. 

on the 986 Porsche... don't these cars have really limited front camber? the 500 lb weight disadvantage is also killer, The thing to remember as well is that you have to do a full option package conversion. So if you want to run the crazy wide wheels from a package, you have to find or build one to the letter of the whole package. and then be able to prove it. 

Also, the 986 have been running in BS before against the S2000, and the s2000 is also in CS starting in 2019... which I don't believe will dethrone the ND2 as it is. 

So like the Cobalt, run it if it's fun for you, but don't be the guinea pig to try building a nationally competitive car.

I had a whole story of what a buddy of mine went through building a "not competitive by the book car" for autox and the money he burned in the process. Basically, there's a hive mind of autocrossers who have STUPID amounts of money they throw into the sport. 

I had a buddy spend over $40k over the summer building a car that just got put into a competitive class and this buddy wants a national championship jacket. These are the kind of people you're going up against. Same friend also wrote a check for a brake new new C7 Z06 a few years back when his other car broke 2 days ahead of an event. People like him and Andy Hollis are all over the sport. 

Javelin said:

In reply to loosecannon :

Dude, thank you! That's the kind of super-valuable info that's hard to find.

The Boxster is IMO a serious contender in a street tire class. They had as an available option some very wide 18" wheels (11' wide rear, 9.5" wide front) and the M030 suspension is really, really good and available as a package for cheap from Suncoast Porsche. The Suncoast kit is all Porsche parts but uses the Rest Of World springs which ride lower than the USA springs. I dunno how the C-Street rules are (I run Mod now) but back then you weren't allowed to be lower than stock so we used USA-spec springs with the Suncoast kit and were CS legal. If you loosen up all the suspension bushings then suck the car down and tighten up all the bolts, the car will sit lower. The stock M030 shocks are so good that I was told several top drivers had tried Penskes and Motons and went back to the Porsche dampers. You can launch the car from redline and get crazy acceleration but keep checking the drivers side CV bolts because they come loose. In the rear and max out the camber and run 0 toe and whatever you get in the back, add 1 degree negative to the front (example: if you get -.7 in the rear, run -1.7 in the front) and slight toe out in the front. Wait, maybe I have that backwards? I can't remember, either the front or the rear is camber limited. This is a great race set up but it will wander on public roads. Get rid of the exhaust from the cats back, it is very heavy. The car will pass sound with straight pipes (at least our 2.7 L did). 

In reply to spacecadet :

That's the beauty of Porsche, nearly everything is available stand-alone "ala cart", including the wider wheels, and can be proved. A cheap Porsche race car can't be more expensive than a CAM car, can it?!?

How is the torque curve in a 986 Boxster S?

Are you familiar with Kansas?

Interesting question

Javelin said:

In reply to spacecadet :

A cheap Porsche race car can't be more expensive than a CAM car, can it?!?

They don’t call it the P-tax for nothing. I think your tire budget may be slightly lower than with your Cobra, but I don’t see this being a cost-saving move.