Jake's Epic BMW 135i Build Thread! (5+ Years of Ownership)
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Well, this was huge news for the N54 community yesterday. We've been plagued with shift bog issues for years that no tuner has been able to figure out. The more power you add, the more noticeable the lag/bog is. It's hard to notice in videos, but very noticeable when you're in the car. It feels like the car hits a wall of bricks post-shift, then takes forever to get back into power. During a race, I lose a lot of ground during shifts.
I've tried a handful of suggested "shift bog fixes", but none of them really worked. So, when this was announced, I didn't have high expectations. I loaded it up yesterday and tried it on my way to work this morning. Well, it actually works! I had the biggest shit-eating grin on my face. The car actually responds to fast shifts and feels like it should.
The only problem... it works so good that I found my Spec Stage 3+ clutch slipping after a hard shift. It wouldn't grab at all in the next gear, just revved to the moon. Kind of disappointing considering the clutch has between 3-5k miles on it (hard miles, none-the-less). I'm sure it doesn't help that I have the drag radials on the car right now, meaning it's gripping very well. The car would never spin or chirp tire between the 1-2 shift or 2-3 shift and I'm sure it will now once I address the clutch. Other people have reported snapped axles between shifts at high power this morning. At this point, I don't care about the potential damages... the manual transmission has finally been unlocked.
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Well, this was huge news for the N54 community yesterday. We've been plagued with shift bog issues for years that no tuner has been able to figure out. The more power you add, the more noticeable the lag/bog is. It's hard to notice in videos, but very noticeable when you're in the car. It feels like the car hits a wall of bricks post-shift, then takes forever to get back into power. During a race, I lose a lot of ground during shifts.
I've tried a handful of suggested "shift bog fixes", but none of them really worked. So, when this was announced, I didn't have high expectations. I loaded it up yesterday and tried it on my way to work this morning. Well, it actually works! I had the biggest shit-eating grin on my face. The car actually responds to fast shifts and feels like it should.
The only problem... it works so good that I found my Spec Stage 3+ clutch slipping after a hard shift. It wouldn't grab at all in the next gear, just revved to the moon. Kind of disappointing considering the clutch has between 3-5k miles on it (hard miles, none-the-less). I'm sure it doesn't help that I have the drag radials on the car right now, meaning it's gripping very well. The car would never spin or chirp tire between the 1-2 shift or 2-3 shift and I'm sure it will now once I address the clutch. Other people have reported snapped axles between shifts at high power this morning. At this point, I don't care about the potential damages... the manual transmission has finally been unlocked.
I need a ride.
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It's cool that this finally got figured out!Ā
Quick thoughts on your clutch slipping thing.
Clutches work on static friction, but use kinetic friction to overload to that point, and kinetic friction has less resistance than static friction (mue). With the shift bog / slower shifts you are giving the clutch a second to lock down and become static before applying full power again. When you eliminate that buffer zone you're going to have much less time for the clutch to lock down to the flywheel and then you're throwing gobs of power through it. I know it's not the long term goal, but ease up slightly on the shift speed (especially with those tires) and I'm sure it'll hold.ĀHow much torque is that clutch rated for? From a quick glance it shows 670tq, which would be crank measured, and you're far above that!Ā
^that's assuming the stock dia flywheel though. -
It's cool that this finally got figured out!Ā
Quick thoughts on your clutch slipping thing.
Clutches work on static friction, but use kinetic friction to overload to that point, and kinetic friction has less resistance than static friction (mue). With the shift bog / slower shifts you are giving the clutch a second to lock down and become static before applying full power again. When you eliminate that buffer zone you're going to have much less time for the clutch to lock down to the flywheel and then you're throwing gobs of power through it. I know it's not the long term goal, but ease up slightly on the shift speed (especially with those tires) and I'm sure it'll hold.ĀHow much torque is that clutch rated for? From a quick glance it shows 670tq, which would be crank measured, and you're far above that!Ā
^that's assuming the stock dia flywheel though.ĀI've read about other Spec Stage 3+ single turbo guys dealing with clutch slip before this shift bog fix, so I figured it wouldn't last forever. Considering almost ALL of those 3-5k miles have been low RPM dyno pulls, 1/2 mile pulls, 1/4 mile launches, Road America laps and general hooning/racing on the street... I was just waiting for it to start slipping. You're correct, it's rated at 670 crank torque and I'm at 691 to the wheels. I still have a stock diameter flywheel.
I'm thinking this winter the car will get a twin disc clutch, upgraded axles, an LSD and some bushings. Maybe a new transmission to ditch my 1-2 syncho issue. Should have no problem running 10s next year...
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I've read about other Spec Stage 3+ single turbo guys dealing with clutch slip before this shift bog fix, so I figured it wouldn't last forever. Considering almost ALL of those 3-5k miles have been low RPM dyno pulls, 1/2 mile pulls, 1/4 mile launches, Road America laps and general hooning/racing on the street... I was just waiting for it to start slipping. You're correct, it's rated at 670 crank torque and I'm at 691 to the wheels. I still have a stock diameter flywheel.
I'm thinking this winter the car will get a twin disc clutch, upgraded axles, an LSD and some bushings. Maybe a new transmission to ditch my 1-2 syncho issue. Should have no problem running 10s next year...
I'm actually impressed that it's holding 690 at the wheels then, only being rated for 670 crank. With a 15% drivetrain loss it means that clutch is withstanding about 770 ft/lbs of torque, or 15% more than rated.Ā
Are larger dia. flywheels an option? I don't know if they were specific issues to the application, but I've heard that twin discs don't last long at all.
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I'm actually impressed that it's holding 690 at the wheels then, only being rated for 670 crank. With a 15% drivetrain loss it means that clutch is withstanding about 770 ft/lbs of torque, or 15% more than rated.Ā
Are larger dia. flywheels an option? I don't know if they were specific issues to the application, but I've heard that twin discs don't last long at all.Ā
I haven't heard of larger flywheels for N54. A lot of people use twin discs are this power level though because there aren't a lot of proven clutch options out there. I'm not looking to get a Spec Stage 5 because I read the driveability sucks.
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Well, the clutch holds the 3-4 shift but doesn't hold up as well on the 2-3 shift. Since the 3-4 shift is fine, I wanted to test my 60-130 time again.
This was my best time BEFORE the shift bog fix.
This is my first try AFTER the shift bog fix.
As you can see, I knocked off 0.3 sec with the fix alone! You can also see the blue line has much less lag in the middle (3-4 shift). The best part about thisĀ is that my 3rd gear was actually stronger in the "before" pull as you can see by the 60-70, 60-80, 60-90, 60-100 times. This means I picked up all of the 0.3 difference with the faster shift, and that there is even more on the table. I think with some fine tuning, I'll be able to get a very low 6 second pass on a cold night with a low tank of gas.
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It's almost time for hibernation... but I'm still driving this beast.
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It's almost time for hibernation... but I'm still driving this beast.
Any plans for visual changes?
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Any plans for visual changes?
I have a lot of ideas floating around in my head, some visual, some mechanical.
- Seibon carbon fiber hood - $775
- Seibon carbon fiber trunk - $650
- Carbon fiber sunroof panel - $399
- NRG race seats with VAC floor mounts - $380 + $380
- Braille B2015 battery - $200
- Completely gut the rear and trunk interior - FREE!
All of these things should shed some noticeable weight from the car. Not sure how many of them I'll do right away because it's an expensive list.Ā At this point, I want to stay at the same power level but remove weight to go faster. I added a considerable amount of weight when I installed the single turbo kit, intake manifold and full exhaust.
I'd also like a 1M replica front bumper. I removed the splitter from my front bumper because I wanted to see if I was hindering my 1/2 mile trap speeds. I'm up in the air about reinstalling it.
As far as mechanical upgrades, I'd like to do the following:
- Motiv twin disc clutch (current Spec Stage 3+ is slipping with less than 5k miles) - $1950
- New-to-me used transmission (mine grinds going into 2nd gear when WOT) - $650
- Stoptech pads and rotors all around - $680
- Solid rear subframeĀ bushings -Ā $300
- Rouge Engineering adjustable rear toe arms - $290
- M3 front suspension upgrade kit - $700
- LSD and upgraded axles - $3000-$5000
- Torn between MFactory LSD and DSS axles or complete E9X M3 rear subframe swap or Ford 9" conversion
- Phenolic intake manifold spacer - $100
- Bias ply tires so I can run a 10 sec 1/4 mile - $500
Again, not sure how many of these things I'll get done right away because this whole post is easily over $10kĀ
Ā but it's a good spot for me to reference as it comes time to buy stuff.It's good boosting temperature, but poor traction temperature...
I was driving it last night and it was spinning in 4th on only 17psi lol. Fun, but scary.
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Just catching up a bit on this thread.Ā Some very cool stuff.Ā You ran....a Spec?Ā Wow.Ā I'v had personal horrible experiences with their stuff in non-BMW applications and in my M5 (remember the embarrassing no-burnout vid from a gathering I was at?) and have yet to hear any good things about them.Ā Good to hear you are going in a different direction.
Lists are fun....
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Just catching up a bit on this thread.Ā Some very cool stuff.Ā You ran....a Spec?Ā Wow.Ā I'v had personal horrible experiences with their stuff in non-BMW applications and in my M5 (remember the embarrassing no-burnout vid from a gathering I was at?) and have yet to hear any good things about them.Ā Good to hear you are going in a different direction.
Lists are fun....
Yup, the Spec clutches are fairly common for these cars. I can't really blame Spec because I'm pushing a lot more power than the clutch was rated for.Ā And believe it or not, the Motiv twin disc setup that I'm eyeing up is actually manufactured by Spec...
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Yup, the Spec clutches are fairly common for these cars. I can't really blame Spec because I'm pushing a lot more power than the clutch was rated for.Ā And believe it or not, the Motiv twin disc setup that I'm eyeing up is actually manufactured by Spec...
I've found that to be common as well....other manufacturers having spec make their stuff.Ā That's how a spec ended up in the M5.Ā I just avoid them like the plague now.Ā It seems that it is a low standard of quality that bites them (and the customer) in the ass. They'll say a .378" step height, which you'll do, but their pressure plate or disk was out of spec (kinda a pun, lol) and it won't work.Ā Hopefully, if the motive is multi-disk they have put it together and checked everything.
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I finally got around to editing/uploading my track footage from Road America!
This was my first time doing anything like this and I didn't have an instructor so be easy on meĀ
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Hey, you avoided all the walls and gravel pits, so at the end of the day you did well!
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A quick 6 minute video of me installing a custom carbon fiber steering wheel. I'm not usually one for expensive aesthetic mods, especially for the interior, but I'm glad I pulled the trigger on this. I'd love to hear what you guys think!
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I think you should've put the money towards something useful like aĀ limited slip diff. I haven't seen a video on it yet so I'm assuming that's still outstanding, as are some other suspension upgrades.
Your 1er is rough around the edges and isn't a show car. This would be like if I added a CF wheel to my E46 M3.Ā Having an alcantara shift boot with factory aluminum interior trim doesn't look that great with a steering wheel that is predominately CF. The steering wheel you have there looks like an afterthought.Ā It's your money of course but the direction you have taken this car is largely about going fast. You have gobs of power now, so why aren't you spending more money to help the car put it down as best as possible?
2011 E92 M3 6MT ZCP - ESS 625 supercharged
2007 Z4MRĀ
2003 E39 M5
2002 E46 M3
2021 X5 40i -
i like carbon as much as the next guy, but that's a bit over-the-top
Dan
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I think you should've put the money towards something useful like aĀ limited slip diff. I haven't seen a video on it yet so I'm assuming that's still outstanding, as are some other suspension upgrades.
Your 1er is rough around the edges and isn't a show car. This would be like if I added a CF wheel to my E46 M3.Ā Having an alcantara shift boot with factory aluminum interior trim doesn't look that great with a steering wheel that is predominately CF. The steering wheel you have there looks like an afterthought.Ā It's your money of course but the direction you have taken this car is largely about going fast. You have gobs of power now, so why aren't you spending more money to help the car put it down as best as possible?Ā
I didn't use cash to purchase the wheel, just exchanged apparel printing services for the wheel. My margin is pretty good for printing stuff so realistically this wheel cost me less than $200. I've had itĀ since last year, just finally got around to installing it. Obviously aesthetic mods are personal preference, but I like the wheel. The carbonĀ center trim is a bit much so I might refinish my factory trim to fix the peeling paint and re-install that.
As far as spending money elsewhere, I haven't spent a dime on the car in probably 6 months. I put it away for the winter and nothing needs fixing, it's been running great. I've been enjoying the surplus of cash I never realized I could have by not throwing money at cars. And believe it or not, the car hooks with the Mickey Thompsons in every gear except for 1st. Factory e-diff has been fine so it's hard for me to upgrade a perfectly good-working part. However, an LSD, upgraded axles and a suspension refresh has been on my wish list. The idea of a built motor is becoming more of a 'want' recently as well, so I need to figure out where I want my money to go once I start spending it again.
i like carbon as much as the next guy, but that's a bit over-the-top
Lol, striking similarities!Ā Like I said above, aesthetic mods are personal preference so I appreciate the comment. It's something different, maybe I'll get sick of it once I start seeing it every day. But for now, it's a nice change of pace. It is a lot of carbon fiber, so I might swap out the trim piece for the OEM piece once I refinish it.
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