Jake's Epic BMW 135i Build Thread! (5+ Years of Ownership)
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Is that a tan 240 with a carbon fiber hood next to you in that first video? Twin turbo LS swap.ย
Yup, it's my friend Brian's Volvo. It's single turbo.
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Yup, it's my friend Brian's Volvo. It's single turbo.
Haha. I know Bryan. Bought some LM reps off him once. I thought he was going to twin turbo it. Either way, it's a super clean 240.
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Ran into some crazy cars in Canada!
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You went to Canada this time eh?
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Scary fast stuff. Crazy that evo is running 44psi, is it over 800whp?
After hearing / watching that evo I did a bit of digging.ย
There was one in CO (Elevation relevance) that was on 40psi and made 830whp.
So I'm gonna go with the on in Appleton being over 800 by a good bit. -
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!ย
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.ยHow 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!ย
^that's assuming the stock dia flywheel though. -
It's cool that this finally got figured out!ย
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.ยHow 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!ย
^that's assuming the stock dia flywheel though.ยI'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.ย
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.ย
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.ย
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 thisย 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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