Cal Club Autocross Forums

Getting anxious while the Miata is in the shop and wanted to ask a question before I do a real comparison of the two.

What would you expect to be quicker given the following modifications:

1993 Miata with Direzza Z2 tires, koni yellows, eibach race springs, polyurethane bushings, hawk HPS brake pads, Flyin Miata frame rail braces, hard dog sport roll bar, 15x7 Kosei K1 wheels, stock sway bars, lightened fly wheel, stock 1.6L motor maybe making 100whp, Limited Slip Differential

or

2007 BMW 335i with sport package, 6 speed manual, open diff, with nothing other than pilot sports? (C&D dyno'd this car in magazine test at 285whp and they make a rated 300 tq at 1400rpm).

I'm not going to be able to run this test for another month or two and just wanted to see what the community from experience thinks would be quicker. The 335 is heavier, but has way more drive out of corners, the Miata has grip and less weight but lacks the power to carry it out of sharp corners like the BMW.

Thoughts?

The Miata for sure!

or... bring them both, we can each make a set up runs in each. Add the times together (per car), divide them by the number of runs, have an average, and compare. Then you'll have a real answer, not skewed by one driver, and having fun in the process.

SCNAX cup is coming in OCT... have more drivers, and more statistical info to base it on.

But more seriously the Miata!

Why... based upon what you posted... the BMW is not fully prepped for DS (it's SCCA Class). The Miata would be over prepped for STS (it's closest class), as the limited slip, and lightened flywheel are both illegal, and should make it even faster in theory.

For what the RTP/PAX numbers are worth...
DS has a .815 Pax
STS has a .829 Pax

That said... I believe on our big SoCal courses STC is faster than STS. Even if we took STC slightly lower .824 index, that's still faster than the DS index. Adding the under / over prepped status of the two cars. In theory the Miata should beat the BMW by about 1.5 seconds on a 60 sec course. In reality, with a lack of tires, limited slip, and shocks on the BMW, your not going to put that power down our of turns, and the Miata is going to beat it by even more.

Thanks for the input Craig, since the next autocross I'll be going to is Camarillo on the 14th I won't be able to bring both of them.

I'm planning on doing a comparison video for a car review website a friend is starting so for sure if I bring them both out you are more than welcome to have a go. I was really surprised given the open differential how well the BMW was able to put it's power down on the pilot sports. It's certainly fast for a 4 door. If you can't tell I'm really ready for my Miata to be back in my driveway.

What class would the Miata be in if I did want to compete and would it be outclassed by the cars in whatever field it would compete in?

Miata class... depends. Is the limited slip a NA 1.6 factory viscous, or a torsen, quaife etc.? and are you willing to put a factory clutch plate back in to play?

I believe it's a torsen. I would not be willing to put the stock clutch back in, but if I did where would that place me? I'll be happy if I'm driving it in the next week. Just got a call from my mechanic saying the upper shock mounts are not sized for the Konis so we're going to see if we can get spherical bearings from Flyin Miata and drill the inner diameter to 12mm from the current 10mm.

Springs don't look like they're long enough for the Konis so I'm in the process of identifying a good rate (see my other thread if you want to lend some input craig...I'd appreciate it). I'm looking at getting some custom springs made from eibach so the waiting continues. Hopefully this thing is done by the 14th when I'm supposed to be at the track

Hurry up and wait...rrrrr....

Many of is in STS installed the NB top hats to solve that, plus lowers the car a smidgen.

N/A Miatas progress from ES to STS to CSP to EP.
SCCA Class wise, Torsen alone in an NA would knock you to CSP. Same with the clutch, so going back to stock clutch, keeping the Torson would not help you. That would need to be a factory viscous or open. Change those two things... everything else you have described would put you into STS.

Oh great, so I'd get to race Schenker....!@#$!!!!

ChristoMX5 wrote:Oh great, so I'd get to race Schenker....!@#$!!!!

I'm going into ESP next season... go CSP so we can have more cars in our SP combined class!

ChristoMX5 wrote:Oh great, so I'd get to race Schenker....!@#$!!!!

Schenker runs in PAX. You'd be running SP combined.

Would it be reasonably competitive in that class?

Not exactly apples to apples, but I have a 135i, same thing as the 3'er, just a bit less flab, as well as a '90 Miata, and have driven both pretty hard. With the descriptions you've given, in terms of raw times, the Miata would spank the BMW unless it's a power course. It takes A LOT of work to get a modern non-///M car to put down decent times/not handle like a total pig. Tire:Mass ratio/grip will always favor the Miata, and stock BMW suspensions/lack of diff leaves a lot to be desired. I'm pretty sure the only reason I didn't sell my BMW after realizing the scope of the challenge to make it quick is because I must be a sadomasochist. It hurts my wallet, and by extension, me to try and get the car as quick as a stock EVO/STi, let alone a decently prepped STU car. Then again, I'm fairly useless behind the wheel so YMMV, and feel free to throw my rants and raves out the window.