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BMW 3-Series (E90 E92) Forum
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LSD or Super Sprint full exhaust?
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View Poll Results: LSD or SS full exhaust? NA section only! | |||
3.91 LSD | 24 | 88.89% | |
SS FULL exhaust | 3 | 11.11% | |
Voters: 27. You may not vote on this poll |
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01-24-2016, 03:17 PM | #23 | |
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01-25-2016, 01:11 AM | #24 | |
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1) It's a generalization. Generalizations imply absolutes. There are no such thing as absolutes. 2) More importantly, horsepower isn't everything. I could give a rat's ass about horsepower. For a street car, torque is far more relevant and important. Torque is king. Given a hypothetical engine with constant torque and variable horsepower I agree that somewhere around a 10% gain is probably what is needed for the driver to notice an improvement because speed is more difficult to gauge. Given another hypothetical engine with constant horsepower and variable torque, the amount of gain in torque before the driver can detect an improvement is going to be less. The reason is simple. Torque is what pushes you back the seat, snaps your head back, and allows wheel slip to occur. In the case of the cat back systems available for our cars, the more popular ones, PE, Flowmaster, Borla, etc. are all just variations of the OEM configuration. As a result the expectation is these systems will not provide any detectable performance gain leading to the myth perpetrated on this forum to "just buy a cat back for the sound cause there are no gains possible". The SS system, on the other hand, takes a different design approach by including elements to produce larger gains not possible within the confines of the stock or stock like system. I don't need dyno runs and timeslips to reach this conclusion, all I need to do is to evaluate the design. No placebo here.
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01-25-2016, 07:50 AM | #25 | |
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2. Bullshit
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01-25-2016, 08:58 AM | #26 | |
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You can't increase torque without increasing HP - although you can increase HP by increasing RPM and using that torque to do more work in a shorter amount of time, typically you won't significantly increase power either without an increase in torque. They are linked together, not separate entities. yeah, maybe it did gain 4whp - but it's not going to transform how the car drives like limited slip does. Mostly it just makes the car loud. When you say you care about TQ, not HP, that's basically bullshit forum talk right there. The easiest way to increase torque to the wheels would be to put in a limited slip differential with a shorter gear ratio - 25% increase is easy. Way more than a loud exhaust could ever hope to make. |
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01-25-2016, 09:04 AM | #27 |
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Yeah, power is the scalar result of the dot product (well, that's redundant...) of the torque and angular velocity vectors. Doesn't get much simpler than that. So that's torque times rpm times a scaling constant equals horsepower.
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01-25-2016, 09:34 AM | #29 |
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01-25-2016, 05:19 PM | #30 |
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To be honest, I'm going to end up doing both - I just like to space out the mods. I've had the car since birth and it didn't get to its current state over night so I don't mind patiently adding on to it. I have an X3 I can daily as well, so downtime isn't part of the issue.
The only thing that drives me a little insane is that my car basically sounds stock but isn't. Sound is part of the enjoyment of a "fun" drivers car. I've tracked the car on road course 3x and have pretty much always found the power and brakes to be the limiting factors on E9X. As a related note, I'll likely try out E46 M3 race pads this year since they do fit on our calipers (source: bimmerworld). The last time I tracked was 2011 and the car was nearly stock by today's comparison but it was fun, no less. As far as goals, I expect to do 3-4 events per year in HPDE (if that). I am not personally a fan of autocross, but will admit it is still a fun time. It is definitely intended to be my weekend "fun car" due mainly to the fact the (high number of) wear items on these non-M's is so much more reasonably priced than some M equivalents. Doing the same stuff with an E90 M3 is worthwhile I'm sure, but is easily double if not triple the cost. Weekend use will also include fairly frequent street use.
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01-27-2016, 10:39 AM | #31 |
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If you want performance, LSD (but I would say that )
If you want sound (at any speed), exhaust. This you do get tired of, and end up cranking up the stereo (which is futile in my case as my exhaust is louder than my stereo) If you want the best of both worlds, LSD + shorter ratio ring & pinion. You get the extra traction from the LSD, the extra torque to the wheels due to torque multiplication, and a louder exhaust due to higher rpm's |
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01-30-2016, 11:54 PM | #32 |
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I will be another person who puts the vote in for the LSD. MFactory is awesome by the way. When I dealt with them last year for my LSD they took care of me very well and their warranty is very trustworthy as they will straight up replace the unit if it is defective in anyway.
Driving with it for almost a year now, I can truly say that it has made the car much more fun to drive, while making it quicker. I have to watch my speeds through turns as I accelerate without much traction loss. Since it is a helical as well, you will not need to worry about maintenance (other than replacing the diff oil 1000 miles in), which is a huge plus. As far as exhaust goes, you seem to want to change the tone. So my recommendation for you would be to get an LSD and a muffler delete. The N52 with a muffler delete has a surprisingly nice tone to it. Definitely can get you through until you can save up for the SS exhaust if you are really set on it.
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01-31-2016, 12:08 AM | #33 |
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OP, one of the most important things to consider when choosing a LSD is:
Whether you want/need a Helical type LSD or Clutch type LSD. Both absolutely have their pros & cons, as the owner of both types I'd tell you to Really research what one will best fit your goals. Rob43 |
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01-31-2016, 02:18 AM | #34 | |
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02-02-2016, 01:22 PM | #35 |
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^
My experiences have been this: Helical (Gear) diffs are great as DD's because they do the job you want them to & are virtually maintenance free. My Quaife LSD is completely silent which is great for typical high performance street driving, but the moment I take it to the track I can get the inner (unloaded) wheel to spin at the apex of a turn. This of course Doesn't promote faster lap times, so for this reason Helical LSD's are only a "Fair" choice as a track diff. Clutch diffs are great for dedicated competition, companies like Diffsonline can setup the exact custom clutch type LSD for the chassis & type of competition that the car will be driven in. These types of diffs are typically the fastest on a Road Course or Auto-X Course because they won't spin the inner (Unloaded) wheel at the apex of a turn. The down side to driving a clutch type LSD on the street is they're usually noisier, require more maintenance like oil changes, & have the tenancy to feel like a locked (Welded) diff while trying to park the car. Helical = Street Clutch = Track Rob43 |
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02-02-2016, 03:26 PM | #36 | |
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Helical gears cannot lock under deceleration, clutch diffs have static lock, and ramp angles that can create lock under deceleration, which aid in rear stability under hard braking. And yes, clutch diffs are noisy, you get a very distinct gear whine with stiffer bushings. |
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02-02-2016, 03:45 PM | #37 | |
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Absolutely. Rob43 |
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02-02-2016, 05:37 PM | #38 | ||
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I guess technically by design clutches do wear, so there must be some rebuild interval, but from what I understand, for a mostly street-driven car even a clutch-type diff can be expected to last the effective life of the car. Anyway, most people who keep a car like this for 8-10 years and beyond expect to put some money into preventive maintenance. If I can get 5 years before a rebuild I'll be happy (about 8,000 miles/year w/ 10-12 AX events - I understand that regular tracking would be much more demanding). Quote:
I don't really get the noise thing, but my diff is brand new. From what I understand a noisy diff can be quieted down by either choosing a different fluid or by adding additional friction modifier to your current fluid. My builder specified Red Line 85W-140 (includes FM) and I have yet to hear a peep from the rear end. Bear in mind I haven't autocrossed with it yet, although I have felt it working on the street with aggressive cornering (40% static lock & 30/60 ramps).
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02-02-2016, 05:40 PM | #39 |
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BMWs came stock with clutch type LSDs for decades until cost cutting measures came into place. They were awesome. I don't think the maintenance is that much of an issue. I've never heard one make noise either - I suppose if you get a high lockup race build, then it could chatter a bit around corners, but the stock LSDs on older BMWs were quiet.
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02-02-2016, 05:41 PM | #40 |
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For reference, these were historically 25% static lock with 45/45 ramp angles.
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