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Last Post 08 Oct 2013 04:24 PM by  MilesJ
Which car would you pick for STX
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splash
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21 Dec 2011 10:18 AM
It should be close. The 2.5 has taller gearing, but a lower limiter. The % of a course you can cover "on turbo" should be about the same, but the 2.5 will make a bunch more torque during that time.
lowside67
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21 Dec 2011 11:38 AM
I am a little surprised that the 128i is not included in the list for STX... were they just thinking nobody would ever campaign one or is there a competitive reason it should be excluded?
IntrigueGX
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21 Dec 2011 11:53 AM

The 3-series weren't listed the first few times, so the 128i was probably just forgotten. I don't think it would be competitive. It can still run in STC regionally.

Haru
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21 Dec 2011 12:03 PM

I worked out the gearing calc when it was announced that the new WRX's were going to be joining us. The speeds in each gear for both versions of the car are near identical. The taller gearing compensates for the 2.0 higher rev-limit. However, because of the taller gearing the torque doesn't really kick in as early as every one thinks for the 2.5's (if you're looking strictly at speed anyway). Due to the taller gears, even though peak torque is achieved 600 rpms earlier... it's more like 2mph sooner... not that big a deal. What I care about is how usable second gear is... and both cars are virtually identical.

There are a couple more things to look at. Can 2.0 cars even tune for boost creep? My understanding is the 2.5's can't due to the plastic IC. Is that right ? If that were the case the 2.0's could make more peak power than the 2.5's, weigh less, and look better...;)

With that being said, I'll be in a 2.0.

Andy Hollis
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21 Dec 2011 12:48 PM
lowside67 wrote:
I am a little surprised that the 128i is not included in the list for STX... were they just thinking nobody would ever campaign one or is there a competitive reason it should be excluded?

Watch FastTrack. Letters have come in and been responded to.

--Andy

murph1379
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21 Dec 2011 12:54 PM
I'm sure the 128i will be in STX, it's very similar to my ZHP, except it can't fit as much tire, can get less camber, and has a bit more power.
splash
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21 Dec 2011 01:23 PM
Haru, I know the '08 cars have the plastic IC tanks, but I don't know if the '06/'07 cars do too. I have experienced an '09 popping its stock IC tanks off with a little less than 1psi surge with stock boost maps and no creeping. They are very intolerant little IC's...
TeamRX8
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21 Dec 2011 08:21 PM
StreetTireStock wrote:
TeamRX8 wrote:
if a 2.5 outperforms a 2.0 the first thing that needs to be done is to tear down their turbo to inspect and measure the components

I forsee a great year racing with you. If an RX-8 is faster than a WRX, I recommend tearing down the Mazda engine and measuring it's pistons.

That's OK, I didn't need to foresee a knee jerk response from certain people. I do appreciate that some other people were familiar enough with the topic to understand where I was coming from. So to them I say, thanks.

I can only wish there were some extra cans bouncing up &amp; down in there, lol. If I get close to, let alone tie or beat, the WRX to 60 ft then maybe you should be concerned ...

dmitrik4
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22 Dec 2011 11:02 AM
murph1379 wrote:
I'm sure the 128i will be in STX, it's very similar to my ZHP, except it can't fit as much tire, can get less camber, and has a bit more power.

is the 128 in the same boat as the 135 when it comes to the diff, or does it have an easier replacement option?

murph1379
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22 Dec 2011 11:41 AM
Tough to tell, I see a lot of diffs advertised for the 135, but not the 128. I'm not sure if 128i owners just aren't buying diffs, or if they're actually different carriers and the 135 units don't work with the 128. I'm sure SOMEONE can make something work. A *good* diff for any car is going to be $2-3k, and you'll need to really maximize a 128 to make it competitive, so I'm not sure that it matters much that there's no factory option.
mrazny
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22 Dec 2011 11:57 AM

Since I've been trying to sell my diff off my 135, I can chime in a bit, but not definitively. I believe the transmissions are different between the 135 and 128 for the manuals as well. The automatic transmissions are entirely different, the 128 has a GM auto with the 135 having a ZF made one. All four (128/135 A/T-M/T) have different part numbers for the diff assembly. IIRC, the 128 also has a welded final ring gear, but in any case it's different. For me, i was an idiot and got the steptronic 135, BUT, the entire diff pumpkin can be swapped between the step and the manual for the 135 but not for the 128. To do the Step/Manual swap is a new final drive ratio so for autocross that's an ST killer. Even if the 128 doesn't have a welded final ring gear, you're dealing with the BMW tool company, the necessary special tool for the Diff install is something like 5G's, so you're dealing with BMW specialists for the install (though I think HP Autowerks in California will let you rent the tool). If you're willing to settle for a Wavetrac or Quaife a few vendors have core swaps available, but you're still paying freight. Basically, it's a money storm (but that's not new, it's BMW).


For the 135, I had clearance issues with the rear sway bar for the lowering i wanted to get to. I either had an ass-high setup with some serious snap, or a no sway push monster. Putting the power down with the no sway though was nice. My actual setup talent and budget ran out before I could give it a full go, I'm stepping away from the STU gig for now. The 135 also simply CAN'T fit more than 265, and that's still full of compromise. Even if the 128 isn't quite up to STX snuff, it's probably closer to STX competitive than the 135 is to STU competitive.

The 128 tune though is easily accessible and dirt cheap for a first go. Same front tires, 100 pounds less, lose 80 wtq that the car struggles to use effectively in autocross anyway?

mrazny
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22 Dec 2011 12:00 PM

I was told the unit itself is the same across the 4 if say you went with an OS Giken, it's just the diff pumpkin itself that's barely different between the 4 transmissions. And actually the OS Giken diff that works for the 135 works for some of the e46's, at least that's what the part number story seems to tell. I'm not sure what the diffsonline type solution would end up being.

dmitrik4
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22 Dec 2011 03:42 PM
murph1379 wrote:
Tough to tell, I see a lot of diffs advertised for the 135, but not the 128. I'm not sure if 128i owners just aren't buying diffs, or if they're actually different carriers and the 135 units don't work with the 128. I'm sure SOMEONE can make something work. A *good* diff for any car is going to be $2-3k, and you'll need to really maximize a 128 to make it competitive, so I'm not sure that it matters much that there's no factory option.

I wasn't referring to a factory option, but more to the welded ring gear issue on the 135, which seems to be a real PITA. While I can get a good diff for most cars for $2-3k, can you do the same for a 1-series? No dog; just curious.

mrazny
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22 Dec 2011 04:14 PM
I went with a super-lock OS Giken. Got the unit for 1800, and really a bargain basement cost-cutting deal for the install to be $900 (chicago prices are ridiculous as well as BMW premium pricing). If you believe AR Design, they sell a tool that let's you do the DIY route for $65, but i didn't have to mess with the welded final ring gear. You *can* get a core exchange and Quiafe unit that would be something like 2600 plus freight costs.
murph1379
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23 Dec 2011 02:28 PM
Sounds like diffsonline could probably put the OS Giken in a 128i diff carrier ready to go for $3k or so, provided it actually fits. Not much more expensive than any of the other diff options. Then it's a simple bolt-on install.
murph1379
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27 Dec 2011 01:33 PM
Dan says $2700 for a 3-disc clutch, or $3100 for an OS Giken, sounds about normal for BMW diffs.

He also mentioned the 128i has a 3.23 final drive, which favorably compares to the 3.15 in an E36 325, the 3.07 in my ZHP, or the 2.93 in an E36 328. That is, if it can rev, not sure if it handles the revs better than an M54...
GotCone?
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27 Dec 2011 02:52 PM

since we're exploring STX newcomers... What about a Lexus IS 300?

Initially a little bit heavier than a E36 328is by about 100-130 lbs, but with more power (215) and torque (218) in stock form. I know nothing about their suspension potential (double wishbone front/rear), power potential, aftermarket support, or ability to fit STX sized wheels/tires. The only initial obvious limitation I see is running out at 56mph in 2nd gear at the stock rev limiter on 255/40-17s. But that should make for good grunt off corners and is only an issue on rare occasions. A small raise of the limit could safely yield a couple more mph.


I see this car as a similar approach to an E46 really, yet it a bit shorter and skinnier package dimensions wise. They share very similar performance numbers and specs.


Discuss. Anyone w/ specific IS300 knowledge care to comment?
jzr
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27 Dec 2011 04:13 PM
IS300 is a good car, there's a thread on them elsewhere on the forum. Ran one in STU in 2005. Suspension is good, same as the Supra.

I made a mistake in that other thread, saying it could fit 265s up front - I was mistaken, was only running 235s. Handled well for its weight (~3250, lots on the nose).
murph1379
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27 Dec 2011 04:24 PM
jzr - is 235 all that would fit? Rolled fenders? Lots of camber?

I seem to recall the big limiters for the IS300 in stock class were fender room and wheel width. It could only get 225 A6s under there, vs. 245s for the 330. Not sure if that can be addressed with fender rolling...
jzr
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27 Dec 2011 04:34 PM
Yes, fenders were rolled (actually bought an extra pair so as to not mess up the stock ones), and it had lots of camber - Cusco makes/made adjustable upper arms for it. It seemed to me that you might be able to fit a 245 using the offset bushing allowance against your favor in the lower control arm, then custom fabricating an even shorter upper arm, to bring the hub mounting plane further inboard. Pretty sure I was running a 9" wheel though, 10" in the rear with a 265 fit fine.
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