Heavy-ish BMW as a track day/autocross car?

"JayZAyEighty thinks C4+3=C7" (jayzayeighty)
11/03/2014 at 16:51 • Filed to: None

This is very hypothetical. Since I may or may not be able to get a really good deal on an E89 Z4 in several years (that will probably have very low/babied miles and be well maintained), I'm wondering how much of a factor you guys think the 3,100-pound weight would be. It could be firmed up with a stiffer suspension and some chassis cross members and pull more grip with non runflat tires, and make 350 hp out of the heatsoak-immune and lightweight I6, but all of the little extra and ridiculous features in the car (especially the PRHT) make it pretty hefty for a little roadster And that's very costly stuff. I have no idea what I'll be doing in 6+ years. What do you guys think?

I like that it's a bit more interesting and maybe more eye-catching than the go-to for upper-middle-class-to-upper-class midlife crises Boxster (when new), but there's no denying that autobahn storming was more of a factor in this car's development than in the Boxster, being at the cost of perfect handling characteristics. At least its weight is rearward-biased and it has the NA engine and M-sport package...

DISCUSSION (54)

Trunk Impaired 318 > JayZAyEighty thinks C4+3=C7
11/03/2014 at 16:54

A guy who compete in my region quite often does pretty well with one, I think he ended up third overall in PAX for the season, and 3100lbs isn't that much. My car has 138hp (well at least it did when it was new) and has to lug around 2700lbs and I was reasonably close to his times and often was running times that compared with a well driven '09 or '10 WRX

Mosqvich > JayZAyEighty thinks C4+3=C7
11/03/2014 at 16:55

There are several Z4s in my local BMW Club. Most of them are used on the track and do well. The Z4 coupe is better though.

Conan > JayZAyEighty thinks C4+3=C7
11/03/2014 at 16:55

I've thought about this before too. Just never done it.

BmanUltima's car still hasn't been fixed yet, he'll get on it tomorrow, honest. > JayZAyEighty thinks C4+3=C7
11/03/2014 at 16:57

If you strip it, you can drop a lot of weight. But maybe you want it as a daily too, then not such a good idea.

JayZAyEighty thinks C4+3=C7 > Trunk Impaired 318
11/03/2014 at 16:58

Not bad at all for the Z4, but really impressive what you're keeping up with! What are you driving?

RamblinRover Luxury-Yacht > JayZAyEighty thinks C4+3=C7
11/03/2014 at 16:59

Opponaut KusabiSensei has already been using his Z4 extensively as a track car. The problem has been tire cost - even given that he's been running other tires than the original runflats. Between that, and overall risk to investment, he took the opportunity to pick up an older Audi for track days instead.

As to weight, my idea of an epic track day car is a properly equipped XJS, which is ~4100lb...

JayZAyEighty thinks C4+3=C7 > Mosqvich
11/03/2014 at 17:01

Yeah, I think that the 3.0si coupe would be amazing to have someday. I really like the styling of the E89, but the weight and rigidity of those coupes is really respectable. They are far more analog, but with a 7,100 RPM engine and 3 pedals the car in question is pretty fun.

Brian Silvestro > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:02

I'm pretty sure it's 3500 lbs. Which is a major reason I can't like this car.

Trunk Impaired 318 > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:02

1999 BMW 318ti with 115k miles, stock everything as in what it came out of the factory with, except for the swaybar brackets and bushings which are 3 years old. As for tires Im on Hankook Ventus RS3s with realistically less than 1k miles as the car is really only used for autocross. I was second in PAX for the season running in GS and next year I get moved to HS where I'll probably run away with PAX.

E92M3 > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:02

Just get a miata if it's going to be a trackday car. If you're looking for a car to drive to work durimg the week, and do autocross/trackdays on the weekend thats a different story.

Arben72 > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:05

I autox my m3 in f street. I do pretty well for being a shit driver. Some tires and kW v3 coils and that z4 would destroy the track.

JayZAyEighty thinks C4+3=C7 > BmanUltima's car still hasn't been fixed yet, he'll get on it tomorrow, honest.
11/03/2014 at 17:06

Yeah, I'm sure removal of stuff like the top mechanism and other stuff would be effective (and the GT3 cars have done very well with tons of changes), but I think that I'd want to maintain relative usability in normal driving.

JayZAyEighty thinks C4+3=C7 > RamblinRover Luxury-Yacht
11/03/2014 at 17:10

Yeah, he has (had, I guess) a neat E85. Those are a lot less cruising-oriented, though! 3,100 is really not that much when you think about it, and less than any BMW made since I believe.

KusabiSensei - Captain of the Toronto Maple Leafs > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:11

It could work. Granted, you'd have to likely figure out how to pass tech if your group requires a aftermarket roll bar for convertibles.

At least on the E85 Z4, roll bars generally require removing the top assembly. My guess is that the PRHT would similarly limit access to bolt down points. So I only go to some tracks with the convertible and now have an S4 for the party poopers (erm...roll bar rules).

Do you know what parts you could reasonably install? Because getting more power from an N52 engine generally means non-trivial work. Suspension would be easier to deal with, I think.

JayZAyEighty thinks C4+3=C7 > E92M3
11/03/2014 at 17:11

That's a good plan, but in 2020 this would probably be mixed use.

RamblinRover Luxury-Yacht > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:15

He's still got it, he's just making sacrifice to the tire gods with the Audi as far as track days go. Either it or the Boxster is costly that way. Whereas, an XJS is definitely not nimble, but is sharp *enough* and won't take as much tire sacrifice to make with the white knuckles. Also, easily obtained 15" tires.

JayZAyEighty thinks C4+3=C7 > Arben72
11/03/2014 at 17:15

An M3 must be a riot to autocross. I'd probably be a shit driver as well, but most problems could probably be solved with some coilovers and rubber!

JayZAyEighty thinks C4+3=C7 > Trunk Impaired 318
11/03/2014 at 17:17

Cool car, I think 318tis are great! It must be a good setup to get a second place finish.

JayZAyEighty thinks C4+3=C7 > RamblinRover Luxury-Yacht
11/03/2014 at 17:19

I lust after a 6.0 XJS (most issues revised over the evolution+lots of power) with a 5 speed manual. It sounds like a good idea to have a secondary autocross car.

Trunk Impaired 318 > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:22

Its a fairly easy car to drive fast, since there isn't all that much power I can just keep my right foot planted for most of a run, the only real tricky part is if the rear end starts to go, depending on how hard you push it you either get a nice slide that you don't even have to try and correct, the car will sort itself out for you, but if you push 1% past that point it'll just swap ends immediately and spit you off course

KusabiSensei - Captain of the Toronto Maple Leafs > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:24

After you burn through TWO $1000 sets of Michelin Pilot Super Sports with the ZSP staggered wheel setup on the E85, you need to find cheaper tires.

$500 Goodrich R1 R-Comps in the S4's size for the win...

JayZAyEighty thinks C4+3=C7 > KusabiSensei - Captain of the Toronto Maple Leafs
11/03/2014 at 17:26

Yeah, I thought the power retractable hard top would help me at a lot of tracks but maybe not... ESS just came out with a +80 HP supercharger, easily boosted to more, and there are a few other options although they still aren't plentiful. Still a fantastic engine. The best non-M I6 built by BMW, dare I say?

JayZAyEighty thinks C4+3=C7 > KusabiSensei - Captain of the Toronto Maple Leafs
11/03/2014 at 17:29

OUCH. Yeah, S4 sounds like a good way to go, keeping in mind safety inspections and all. I assume I'll still have the Corvette failing passage of the Z4.

JayZAyEighty thinks C4+3=C7 > Trunk Impaired 318
11/03/2014 at 17:33

Haha yep I'd probably have a bit of a love/hate relationship with that E30 rear suspension. Great for just hooning about, apparently!

KusabiSensei - Captain of the Toronto Maple Leafs > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:34

I have a good group who let me run with stock rollover bars on the Z4. If you can find a similar group that's convertible friendly, then there you go.

The S4 is cheaper until the 2.7T engine shits a gasket or the turbos.

The Audi was bought for $2900, so that's three sets of Pilot Super Sports, or about 4.5 sets of Dunlop Direzzas or similar.

My local race shop supplied the R1 R-Comps for that price since he wanted them GONE (because no one wanted that size). Normally they are more expensive than the PSS set for the Z4.

KusabiSensei - Captain of the Toronto Maple Leafs > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:38

PRHT doesn't help because it's not a single structural piece with the windshield frame. Even through it's more protection than a soft-top, it is not treated in most inspection circles as the same as a fixed coupe roof.

I'd suggest learning car control with the N/A R6. Boosted engines are harder to control.

I spun the AWD Audi at Daytona coming out of the bus stop chicane on the back straight. I was fortunate to not hit anything or anyone.

I have to chop the GoPro video down for that lap, and maybe gif-ify the spin.

JayZAyEighty thinks C4+3=C7 > KusabiSensei - Captain of the Toronto Maple Leafs
11/03/2014 at 17:41

Wow, sounds like you got a great deal on that S4. Having AWD just seems to make sense in this application because more traction and therefore no need for really expensive rubber. If I could find a convertible friendly group, that would definitely be great.

Trunk Impaired 318 > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:42

It really is great fun and very easy to handle but you just never have any warning about exceeding that 1% until its just about too late

KusabiSensei - Captain of the Toronto Maple Leafs > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:46

Torsen Center Differential based AWD is all well and good until you exceed the Torque Bias Ratio, and then the whole thing unlocks and you get an effective open diff.

Which partially explains my spin. Too much power shuttled to the front, loss of grip, loss of sensed torque on the front axle lead to the center unlocking, and power shuttling to the rear, and then when grip was regained, 4:1 torque ratio to the rear and sent the whole thing in a 180.

Granted I would have spun a RWD in the same place. but I would have spun earlier, and not have been heading towards the outside SAFER barrier.

BmanUltima's car still hasn't been fixed yet, he'll get on it tomorrow, honest. > JayZAyEighty thinks C4+3=C7
11/03/2014 at 17:49

The GT3 cars are nothing like the road cars unfortunately. See if you can get the hardtop and just fix it in place. That might work.

Arben72 > JayZAyEighty thinks C4+3=C7
11/03/2014 at 18:58

The z4 has a really sporty chassis, don't let the weight put you off of it. My m3 weighs a lot more and it's still a ton of fun. Plus they're the best looking bimmer in a while.

N51fanatic > JayZAyEighty thinks C4+3=C7
11/03/2014 at 19:26

Get a 128i M-Sport. Manual seats, no sunroof, lose the boat anchor stock rims and runflats with some Apex wheels and PSS's and you can get this thing weighing about 3050 lbs.

Kinja'd!!!

JayZAyEighty thinks C4+3=C7 > N51fanatic
11/03/2014 at 20:06

That's the ideal modern BMW, but I also like the Z4 and I'll likely get a really nice deal on it. I was able to test drive a normal 128i with a stick (not for me), and it was great. Only cost $18,000 with 30k miles. Really fun cars. At the same time, the Z4 is about as fun in Msport 30i guise. I also got to go along for a 2011 328i test drive. Gorgeous white/red, 13k miles, 6 speed, CPO. Dealer was offering it for $25,000 negotiable because it was custom ordered without the sunroof—crazy good deal! Also a couple of N54 cars, which just didn't do it in terms of feel. In the end, my mom liked the Z4 best, which is fine by me because my car is quite analog and I can appreciate the Z4 as a result; it's not as solid or smooth as the cheapest and roughest BMW of the past 20 years. Also, if that's your car, it's fantastic looking! People act like the 2 series is such a big deal... I remember optioning out a 2013 128i just like that and thinking about how it's the last time anyone will be able to do that.

N51fanatic > JayZAyEighty thinks C4+3=C7
11/03/2014 at 20:17

stock image from google. This is mine, 2011 MSport 6 sp Leather/Xenons, BMWPE, Bilstein B8's, Swift Springs, Apex Arc-8 18 x 8.5 +45 square (Anthracite),Conti ExtremeContact DW 235/40 square and have since added a CF rear lip spoiler.

Kinja'd!!!

JayZAyEighty thinks C4+3=C7 > N51fanatic
11/03/2014 at 20:20

Wow that is gorgeous. Great wheel choice, and that white is the best color for a 1 series for sure. I bet it's fantastic around the corners. The BMW PE sounds unbelievable, too. Assuming I'm not broke and can buy the Z4 in several years, those wheels would be a top consideration.

N51fanatic > JayZAyEighty thinks C4+3=C7
11/03/2014 at 20:22

its titanium silver lol

JayZAyEighty thinks C4+3=C7 > N51fanatic
11/03/2014 at 20:32

Haha it looked like that one metallic white color with my phone screen brightness turned down. It looks really nice though, nicer than white now that I see it :P

BiTurbo228 - Dr Frankenstein of Spitfires > RamblinRover Luxury-Yacht
11/04/2014 at 07:09

Great call on the XJS :)

Actually, I've bought a 4.0l AJ6 for £100 on a bit of a whim :S the plan is to try and squeeze 300-350bhp out of it. Might actually be a bit of an ask, but I'm thinking compression, head work, bundle-of-snakes header leading to a sidepipe exhaust and ITBs should get me at least close.

Then I just need to find an early (and thus lighter) 3.6l manual XJS to swap it into :)

RamblinRover Luxury-Yacht > BiTurbo228 - Dr Frankenstein of Spitfires
11/04/2014 at 08:51

Early model makes for assured old-style buttresses as well, and some of the other visual touches. Brilliant.

BiTurbo228 - Dr Frankenstein of Spitfires > RamblinRover Luxury-Yacht
11/04/2014 at 09:00

Yep :) and I'm thinking if I cut the outer face of the cill off, flip it round so it's concave rather than convex, I'll have a neat little space to run a side-pipe through :)

Oh, and cool little barrel-gauges too :) plus I won't need cats to pass emissions. Perfect :)

JayZAyEighty thinks C4+3=C7 > KusabiSensei - Captain of the Toronto Maple Leafs
11/06/2014 at 21:36

Wow, that sounds crazy. I didn't realize that Torsen LSDs would do that at the limit.

JayZAyEighty thinks C4+3=C7 > KusabiSensei - Captain of the Toronto Maple Leafs
11/06/2014 at 21:38

That makes sense. And it would be better to learn on the NA engine for sure. Some people are so power crazy without realizing it's not helping them. But that would be an amazing gif!

JayZAyEighty thinks C4+3=C7 > Brian Silvestro
11/06/2014 at 21:44

Well for a DCT 35i with all of the boxes ticked, it's close. The N52 is the absolute lightest production I6 of all time! And the Getrag 6MT saves a lot. Better rubber, some coilovers, headers, chassis stiffening, a tune, and a top mechanism delete would probably drop the weight even more, put whp around 290, and make it handle incredibly. Then once you're tired of that, supercharger+oil cooler+more tuning=100-120 more whp.

Brian Silvestro > JayZAyEighty thinks C4+3=C7
11/06/2014 at 21:46

Yeah but that sounds expensive, complicated, and unreliable.

I'd much rather have a Supra Turbo.

JayZAyEighty thinks C4+3=C7 > Brian Silvestro
11/06/2014 at 21:59

Yeah, but that's my long term plan anyways! Like, protracted out by 15+ years from now. Reliability would still be good if done right—400 reliable hp is possible from tuning, ESS supercharger, cam, and some other low-stress modifications. This is basically to get you to the performance of a BPU Supra turbo, but it's not nearly as bad as it sounds! I'm going to have to talk to a guy at the BMW shop down the street about it, then I'll post my master plan.

Brian Silvestro > JayZAyEighty thinks C4+3=C7
11/06/2014 at 22:03

SUURRRREEE

JayZAyEighty thinks C4+3=C7 > Brian Silvestro
11/06/2014 at 22:30

FFS, I'll overnight parts from Japan! But the basic plan:

E89 Z4 30i: 240 whp (dyno figure)

-E36 M3 ITBs, valvetronic on full lock, cam, new exhaust manifold, flowed head (has already been done for 335whp naturally aspirated)

~$5,000

Supporting mods for reliability and power potential (HPFP, oil cooler, higher pressure oil pump, ECU, clutch)

~$3,500

ESS supercharger: +120hp (proven to be safe at these levels for daily driving without so much as an oil cooler, tested in extreme conditions by ESS)

$4,995

E85 and tune (generally yields another 8-12% on supercharged BMW I6s, conservatively)

~$500

Because of the NA mods, I will underrate the supercharger's effect compensating for parasitic loss at 30hp.

This comes out to an average of 425whp using modifications that have tend to retain reliability. Giving myself a margin of error of 35whp, which is quite reasonable, I believe that it's more than plausible to build an N52 out to 400hp reliably. Failing that, which is unlikely, I haven't even factored taking out the engine another .2L through increased bore or stroke. An option that, despite being quite costly, gives easy access to compression increases and more robust internals. By my estimation, that would be financially ridiculous (considering options for engine swaps) but increase output by an excessive amount.

I think the stock engine is more than enough, but having those options is awesome if I am ever somewhat successful. 350hp cheaply through supercharging is the most logical route for modification. Also, cost estimation errs on the side of caution as does power speculation.

Brian Silvestro > JayZAyEighty thinks C4+3=C7
11/06/2014 at 22:33

But that still sounds pretty expensive, and you're dumping all of that time and money into a meh car. Sure it'll make it better, but there are much better cars that can be had for much less money.

KusabiSensei - Captain of the Toronto Maple Leafs > JayZAyEighty thinks C4+3=C7
11/06/2014 at 22:42

Torsens are great so long as the surface traction characteristics remain fairly constant. Tarmac -> grass -> tarmac in a short timespan (what I did) will cause you to exceed the capability of locked imbalance in the output stages, and it will effectively unlock. Not in the sense of completely unlock (it could be taken that way), but that any additional power flows to the faster output side (which is what an open differential would do).

Since it is TORque SENsing, the amount of torque that can be passed is dependent upon the amount of traction at the slipping output stage. So if one of the front wheels is on grass, that's my limiting factor for traction, and then when it regains, it has more initial torque to use with the TBR (4:1 in the case of the B5 S4). So power was flowing to the front axle (and being sent to the wheel on grass, because I was above the EDL cutoff speed), and then when it got back on tarmac, it has more traction to work with, and then the torque flows to the other axle (as I'm now within the TBR for a given amount of power being put through the center diff). So rapid power reshuffling to the rear axle while on the throttle means that it acts as if I've just given it a boot of power to a RWD car. Since I wasn't expecting this (because I've only done track driving on RWD cars), I spun.

This is why on a generation III quattro system, if you have both rear wheels and one front wheel with no traction, quattro won't be able to move the car (Open diff at front, Torsen center, manual locking rear). Gen IV quattro systems remove the locker in favor of EDL (for better or worse).

JayZAyEighty thinks C4+3=C7 > Brian Silvestro
11/06/2014 at 22:45

This is definitely more of a pipe dream , but with a little bit of work the Z4 wouldn't be a meh car at all. Out of the box, you have a very capable chassis, great interior, the best non-M straight 6, rear-biased weight distribution (to a surprising extent) and balanced handling, and great styling. I'd try to get a nice deal on the car, and do tires, coilovers, and a supercharger. That will cost under $7,000 total, make the car perform on the level of the E90 M3, and you still have a reliable and comfortable roadster that you can turn into a coupe, quiet, turn traction control on, and soften up at the touch of a button for normal driving! (Thank you, M-sport package)

Brian Silvestro > JayZAyEighty thinks C4+3=C7
11/06/2014 at 22:46

So what would the car cost you total after all of the modifications?

JayZAyEighty thinks C4+3=C7 > Brian Silvestro
11/06/2014 at 23:01

Hmm... 6 years down the road, probably with under 45k good-weather miles and warranty maintenance for 4 years, value factoring for depreciation: ~25k?

My mom said if I wanted to buy it at that point she'd take off a third of the price, so the car would probably cost me around $17,000 with taxes and fees. Assuming I spend the $7,000 to have it outperform the sdrive35is, it would probably cost $24,000 so still under used value. To have it make over 400whp and be completely nuts, it should cost me no more than $32,000 (including the price of the car) to have it basically over engineered and built by a reputable shop. So what I'm saying is that I need to have lots and lots of money to throw away by then, which is unlikely and the Z4 will probably remain stock. Either way, it works out pretty well! If I turned it into a track car (by which time it would be eligible for vintage racing because monies), I'd be able to put on a real hard top, take out the ridiculous weight adding stuff in this car, and execute Plan 400+ (That's what I'm calling the vision I have of the ultimate Z4)

Brian Silvestro > JayZAyEighty thinks C4+3=C7
11/06/2014 at 23:02

STOP WRITING SO MUCH, YOU'RE MAKING ME OBLIGATED TO REPLY

JayZAyEighty thinks C4+3=C7 > Brian Silvestro
11/06/2014 at 23:06

But plan 400+, it's taken so much research and consideration and calculation for something unrealistic and I just need someone to appreciate me does anyone like me writing writing writing so so much.