Ryan's 2012 128i MSport STX / Daily Driver Escapades

[Kgolf31]

I'd like to know where this sold Y-Pipe is at? Lol

[Taskmaster]

Originally Posted by Kgolf31

I'd like to know where this sold Y-Pipe is at? Lol

Sorry, I sold it to someone else with a -z4si and a 135i on here. My brain is scrambled a bit.

[RyanDavies]

Originally Posted by chris82

I didn't say it was bad, just high. I'm all for the high springs lol.

The wheel rate for the front is 0.960, and the wheel rate for the rear is around .6, where is the 1/4 coming from? An 850 lb/inch spring translates to more than 250lb/inch at the wheel.

fwiw, the Mitchum Motorsports 128i which competed in Grand Am and other races, runs a singe pipe exhaust all the way back.

Wheel rate = spring rate * motion ratio squared. The front MR is .954 (so the wheel rate = spring rate * .91 (approx). The rear MR is .567, so the wheel rate = spring rate * .32 (so 1/3, sorry). Basically, a spring change at the front has *3x* the effect it does on the rear.

For reference, my STR car, which was absolutely perfect on balance, ran suspension frequencies (no rear bar, big front bar, I hate rear bars for a number of reasons) of 2.14hz front, 2.37rear. Way better way to compare setups between cars than rates, because they include the actual corner weights of the car.

At STX weights, here are the ride frequencies of different spring rates on the car. Keeping a .2 or so split between front and rear is ideal for a number of reasons that are beyond the scope of this thread, but I'll debate putting a blog together on it. For what it's worth, I actually like soft cars a lot in roll, which I believe my car is.

300 1.99
350 2.15
400 2.3
450 2.44

Rear
700 1.92
750 1.98
800 2.05
850 2.11
900 2.17
950 2.23
1000 2.29
1100 2.4
1200 2.51


I've talked at length to a couple GA teams who have run N52 cars. They disagree heavily with what homeboy above has posted.

As an aside, I don't care about low-end torque too much (and I doubt Kyle does either). A histogram plot of National Solo course speeds will show that, after the initial first gear shift, 90% of the run occurs at speeds above 3500RPM (33MPH in a 128 running 255/40/R17 RE71Rs, with a 25in diameter (unshaved). The vast majority happens between 40MPH-50MPH, with bursts above. In a sense, I really only care about the 4000RPM+ powerband. Not a lot below that. In addition, in the speeds sub-40, you're usually combining your acceleration on exit with lateral use of the tire, so you're traction limited, not power limited.

Sadly, I can't find the thread you're referencing. I did, however come across some interesting posts where you were debating running an intentionally illegal car in STX, and told Kyle that 200lbs was irrelevant in Solo Performance (for reference, 200lbs will affect a thrust curve more than even 10whp will), and one asking for help installing an intake.

[Taskmaster]

Originally Posted by RyanDavies

Wheel rate = spring rate * motion ratio squared. The front MR is .954 (so the wheel rate = spring rate * .91 (approx). The rear MR is .567, so the wheel rate = spring rate * .32 (so 1/3, sorry). Basically, a spring change at the front has *3x* the effect it does on the rear.

For reference, my STR car, which was absolutely perfect on balance, ran suspension frequencies (no rear bar, big front bar, I hate rear bars for a number of reasons) of 2.14hz front, 2.37rear. Way better way to compare setups between cars than rates, because they include the actual corner weights of the car.

At STX weights, here are the ride frequencies of different spring rates on the car. Keeping a .2 or so split between front and rear is ideal for a number of reasons that are beyond the scope of this thread, but I'll debate putting a blog together on it. For what it's worth, I actually like soft cars a lot in roll, which I believe my car is.

300 1.99
350 2.15
400 2.3
450 2.44

Rear
700 1.92
750 1.98
800 2.05
850 2.11
900 2.17
950 2.23
1000 2.29
1100 2.4
1200 2.51


I've talked at length to a couple GA teams who have run N52 cars. They disagree heavily with what homeboy above has posted.

As an aside, I don't care about low-end torque too much (and I doubt Kyle does either). A histogram plot of National Solo course speeds will show that, after the initial first gear shift, 90% of the run occurs at speeds above 3500RPM (33MPH in a 128 running 255/40/R17 RE71Rs, with a 25in diameter (unshaved). The vast majority happens between 40MPH-50MPH, with bursts above. In a sense, I really only care about the 4000RPM+ powerband. Not a lot below that. In addition, in the speeds sub-40, you're usually combining your acceleration on exit with lateral use of the tire, so you're traction limited, not power limited.

Sadly, I can't find the thread you're referencing. I did, however come across some interesting posts where you were debating running an intentionally illegal car in STX, and told Kyle that 200lbs was irrelevant in Solo Performance (for reference, 200lbs will affect a thrust curve more than even 10whp will), and one asking for help installing an intake.

Hey dude, do as you please. I already gave you the exact reason why you wouldn't make any more power and lose low end torque.

But hey, you know more than me because you read a thread where I asked how to remove my bumper, hack my airbox to install the Dinan intake, and run my STX* car in a PRIVATE autocross club where the rules don't matter.

But you're right, 200lbs would have a greater effect on acceration, and it's so obvious that I never asked for an opinion on the matter.

But have fun trying to reinvent the wheel and failing at it.

[RyanDavies]

Who was your tuner? Out of curiosity. None of the common tuners have a 3in pipe base map available, so just curious if there's anyone doing fully custom dyno tunes other than Epic.

[Taskmaster]

For eveyone else reading this thread, please don't follow in OP's footsteps. Placing the collector too close to the manifold like he proposes will cause the exhaust gasses to back up into the combustion chamber at lower rpm when scavaging and exhaust gas speeds are lower. It's called exhaust reversion, and race teams don't care much about it considering they don't spend any time on the street.

Just to be sure, I'll post a few examples:

http://www.r3vlimited.com/board/showthread.php?t=317505

Exhaust from run 3 notice the x-pipe is closer to the engine



Run 3 to run 4 was a cam timing change (advanced 8 degrees). i did a cam belt change at the same time and thought maybe the timing shifted a few degrees. while i found good gains the shape of the torque curves shows that this was not the problem. the real problem is the relocation of the x-pipe

Originally Posted by Loftygoals

So I posted my dyno a few weeks ago:

http://www.m3forum.net/m3forum/showp...&postcount=949

On the suggestion of some of the forum members, I reworked my 3.5" exhaust.

Original Config:
eBay Headers
4" of 2.25 Dual Pipes
Merge to 3.5"
3.5" Resonator
3.5" Race Muffler

New Config:
eBay Headers
40" of 2.5" Dual Pipe
Dual 2.5" Resonators
Merge to 3.5"
3.5" Resonator

Basically, I moved the merge back to just before the rear subframe on my MZ3 Coupe. This forced me to change to dual resonators before the merge.

The other modification I made was I switched from the stock water pump setup to an electric pump.

The results, we awesome:



Sorry for the lack of Torque readings, but the dyno wasn't picking up RPMs for my base line pulls. But you can clearly see there is a lot more power down low. Up top didn't change, despite the electric pump. This leads me to believe either the readings were a little varied from the last time I was on the dyno, or that the exhaust changes zapped a little top end power, but the electric water pump made up for it.

Then I did a little playing with the ECU settings and tune. I wanted to richen it up a bit up top:


This compares my dyno from a few weeks ago to my exhaust changes and a little tuning.

I'm happy overall, but I think with some better tuning that I can pick up a lot more power up top.

3.5 race exhausr vs stock collector placement 3.5" exhaust

[RyanDavies]

Bringing this back on topic, last night made some additional progress:




Got the Brides in the car, on Sparco bases. Haven't made sure the seat belt receptacles are plugged in correctly yet, and will need to get the airbag light coded out, but that should happen this week. These are the best-fitting aftermarket seats I've had in any car. I've got a small waist (32/32 jeans are a little loose on me), but big quads, and they fit great. Hold me in very, very well, along with the codriver, so we're good. Lots of shoulder clearance, too.

Also test fitted my 17x9 rear with 255 RE71R. It's at the limit of what one could do with stock camber (unadjusted) and no roll. Lots of inner clearance. Would definitely go with a 55 if I were going to switch to the 265s (which is likely by the end of the year).

[RyanDavies]

.

STX RX8, STX BRZ, STX 328 based on full-prep dynos. STX 128 dyno based on an 80% prep dyno (likely between 8-10ft/lbs down across the board, maybe more..)

[chris82]

Originally Posted by RyanDavies

Wheel rate = spring rate * motion ratio squared. The front MR is .954 (so the wheel rate = spring rate * .91 (approx). The rear MR is .567, so the wheel rate = spring rate * .32 (so 1/3, sorry). Basically, a spring change at the front has *3x* the effect it does on the rear.

For reference, my STR car, which was absolutely perfect on balance, ran suspension frequencies (no rear bar, big front bar, I hate rear bars for a number of reasons) of 2.14hz front, 2.37rear. Way better way to compare setups between cars than rates, because they include the actual corner weights of the car.

At STX weights, here are the ride frequencies of different spring rates on the car. Keeping a .2 or so split between front and rear is ideal for a number of reasons that are beyond the scope of this thread, but I'll debate putting a blog together on it. For what it's worth, I actually like soft cars a lot in roll, which I believe my car is.

300 1.99
350 2.15
400 2.3
450 2.44

Rear
700 1.92
750 1.98
800 2.05
850 2.11
900 2.17
950 2.23
1000 2.29
1100 2.4
1200 2.51


I've talked at length to a couple GA teams who have run N52 cars. They disagree heavily with what homeboy above has posted.

As an aside, I don't care about low-end torque too much (and I doubt Kyle does either). A histogram plot of National Solo course speeds will show that, after the initial first gear shift, 90% of the run occurs at speeds above 3500RPM (33MPH in a 128 running 255/40/R17 RE71Rs, with a 25in diameter (unshaved). The vast majority happens between 40MPH-50MPH, with bursts above. In a sense, I really only care about the 4000RPM+ powerband. Not a lot below that. In addition, in the speeds sub-40, you're usually combining your acceleration on exit with lateral use of the tire, so you're traction limited, not power limited.

Sadly, I can't find the thread you're referencing. I did, however come across some interesting posts where you were debating running an intentionally illegal car in STX, and told Kyle that 200lbs was irrelevant in Solo Performance (for reference, 200lbs will affect a thrust curve more than even 10whp will), and one asking for help installing an intake.

Are we actually resorting to name calling? "Homeboy"? Really?

[RyanDavies]

Sent you an FB message, but no .

[3002 tii]

Originally Posted by TheAxiom

Lol, I'll say this once and take my leave because I don't care to get into a pissing match.

You're wrong. I sold Kyle that Ypipe that I bought from Burns stainless, I orginally planned to do a full single from the header back to save weight and maximize power. The problem was is the Y pipe placed that close will lose power, and I'm not asking, I'm telling you.

I made a whole thread (and you're welcome to check it out) dedicate to figuring out how to gain extra power out of the exhaust, spent countless hours reading, asking questions and recounting my own experience helping design an exhaust for a friend. The conclusion is that the stock placement is best and moving it where you want will cause significant reduction in low end torque for the exact reason I gave to Kyle.

You guys are both right. Replacing as much of the stock with single 3" (i.e. moving the Y merge as far up, closer to headers) will shave most weight and increase top end / peak hp. The issue is however you sacrifice low and mid range torque, below 4500 rpm or so. Your decision to where to place the merge has to be a conscious decision.

For example the Bimmerworld 3" race exhaust for the s54 places the merge right by the headers. This is marketed towards race cars where you're doing most of your driving in the higher rev range. Rogue's Diablo exhaust however places the merge after section 1 as to not sacrifice the torque and would be better suited for street or dual duty cars.

End of day, just make sure you go mandrel with least number of sharp bends as possible and exit with a high flowing muffler.

[Taskmaster]

Originally Posted by 3002 tii

You guys are both right. Replacing as much of the stock with single 3" (i.e. moving the Y merge as far up, closer to headers) will shave most weight and increase top end / peak hp. The issue is however you sacrifice low and mid range torque, below 4500 rpm or so. Your decision to where to place the merge has to be a conscious decision.

For example the Bimmerworld 3" race exhaust for the s54 places the merge right by the headers. This is marketed towards race cars where you're doing most of your driving in the higher rev range. Rogue's Diablo exhaust however places the merge after section 1 as to not sacrifice the torque and would be better suited for street or dual duty cars.

End of day, just make sure you go mandrel with least number of sharp bends as possible and exit with a high flowing muffler.

Thanks for chiming in, I was going to tag you, but it wasn't worth the pissing match. But the Y placement is why you felt some low end loss on your build, and it's also why Supersprint keeps the placement essentially unchanged on their system.

[RyanDavies]

Yeah, the lack of concern about low-end power is precisely why I posted the information that I did.

I can probably count the number of times I've been full-throttle below 30mph (save for ProSolo) on one hand, in maybe 3 years, and none of them happened at events where the result was very important (usually on local lots with very tight turnarounds and the like).

Kyle, do you have SoloStorm histogram plots for speed for Nationals / Pro Finale 2015? That'd be useful data for this conversation. I don't on hand (cleared out a majority of my STR S2000 logs).

Make sure you trim start/stop points so you don't have the low-end filled up with the coast post-finish, etc.

[3002 tii]

Originally Posted by TheAxiom

Thanks for chiming in, I was going to tag you, but it wasn't worth the pissing match. But the Y placement is why you felt some low end loss on your build, and it's also why Supersprint keeps the placement essentially unchanged on their system.

Yea mine was that among other things. Once I resolved an exhaust leak and replaced out my solenoid (got tired of cleaning every 10k), the car felt much better. The increase in top end puts a huge smile on my face, but driving around town you do notice the dip in torque at 3k.

Agree on your comment re SS design. I think the SS exhaust is marketed more towards the masses. Before I realized this, I thought best practice was to copy BW and Vorshlag's design. Again, different design for different goals/purpose.



I'm actually in the process of tweaking my exhaust. I need to raise it a bit but while I'm at it I'm considering moving the Burns Y collector a little further back and slapping on a high flow cat.

[Taskmaster]

Originally Posted by 3002 tii

Yea mine was that among other things. Once I resolved an exhaust leak and replaced out my solenoid (got tired of cleaning every 10k), the car felt much better. The increase in top end puts a huge smile on my face, but driving around town you do notice the dip in torque at 3k.

Agree on your comment re SS design. I think the SS exhaust is marketed more towards the masses. Before I realized this, I thought best practice was to copy BW and Vorshlag's design. Again, different design for different goals/purpose.

I'm actually in the process of tweaking my exhaust. I need to raise it a bit but while I'm at it I'm considering moving the Burns Y collector a little further back and slapping on a high flow cat.

You won't lose any high rpm power as long as you don't move it too far back.

I really want to see what you eventually put down, I bet it rips!

[Kgolf31]

Originally Posted by RyanDavies

Yeah, the lack of concern about low-end power is precisely why I posted the information that I did.

I can probably count the number of times I've been full-throttle below 30mph (save for ProSolo) on one hand, in maybe 3 years, and none of them happened at events where the result was very important (usually on local lots with very tight turnarounds and the like).

Kyle, do you have SoloStorm histogram plots for speed for Nationals / Pro Finale 2015? That'd be useful data for this conversation. I don't on hand (cleared out a majority of my STR S2000 logs).

Make sure you trim start/stop points so you don't have the low-end filled up with the coast post-finish, etc.

Well considering I didn't know I could do histogram plots, I'll have to make some up.

I still have the logs so that won't be an issue. Expect them tonight or tomorrow.

[RyanDavies]

It was part of a post-season SoloStorm update. I came across them when poking through some logs to confirm a thought.

[3002 tii]

Originally Posted by TheAxiom

You won't lose any high rpm power as long as you don't move it too far back.

I really want to see what you eventually put down, I bet it rips!

Probably not that high since I'll be slapping a race cat on. Back on topic, sorry OP!

[RyanDavies]

Okay, finally got some big stuff done today.

AKG Front Endlinks, JRZs + Camber plates on. Front ride height set, rear needs to come down a bit after the fenders are rolled (which is why my front wheels are stockies now, too.



Frustratingly, the front adjusters don't fit exactly right when the plates are being used at max camber, so I'll likely be just using an 8mm wrench. No prob!



The car rides STOCK with front shocks at 5/12 compression, 12/22 rebound, and rear 5/12 compression, 9/22 rebound. Silly amazing really. Pumped all the dampers up to 220psi, as well.

Fenders rolled tomorrow, and the christmas-lights on the dash being disabled, along with all the brake coding and e-diff crap, in preparation for the diff + AKG bushings going in on Wednesday, along with an alignment. First event will be a test-and-tune next weekend in Danville, VA. Not expecting much with the car this far overweight and down on power, but it'll be good to see where it sits.

I also realized I need to re-install my front sway bar, as it is *very* bound up with the bushings Eibach provides, so going to sand those down so they aren't so compressed by the bracket.

[RyanDavies]

Drove on RE71Rs in a couple inches of snow this morning to the shop that's rolling my fenders and performing some of the coding for me. Not nearly as bad as I was expecting.

[Kgolf31]

Jesus tires in the wet, and snow.

[RyanDavies]

Don't think I'll be getting 265s on the front . Have to lower the rear a bit before alignment, but that'll be easier to do on a lift tomorrow when the diff + bushings go in. Car finally looks decent though, but man is it in need of a detail.