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Does anyone know if LSD can be added to 08 WRX, I autocross in the STU class and it would help to be on par with the STI's that I compete against.
 

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i think that the drivetrain is the same as older ones, so any lsd's made for older wrx's should work. not positive though.
 

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you could possibly add a front or rear lsd but you would have to find some way to permanently turn off the VDC. there is actually alot to it. i found alot of interesting info over on nasioc written up by the "unabomber" himself. do the research yourself to find out what exactly has got to go into it before you buy the wrong parts on someone elses suggestion. anyone can just say... "yes it will fit" BUT a LSD is around $500- 600 and when your VDC kicks in and tries to slow a spinning wheel it will put braking forces on all of the drivetrain. if you do install an lsd it will cause a lot of stress on the center diff if the VDC is not permanently disabled. just like how we wrx owners should never do parking brake turns because it puts excessive forces on the center diff. fact is.. our cars are only 2 wheel drives. 1 wheel up front and one in the back. you will not engage an all wheel spin in our cars because we have open diffs both front and back. good luck and let us know how you make out if you go this route. :)
 

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you could possibly add a front or rear lsd but you would have to find some way to permanently turn off the VDC. there is actually alot to it. i found alot of interesting info over on nasioc written up by the "unabomber" himself. do the research yourself to find out what exactly has got to go into it before you buy the wrong parts on someone elses suggestion. anyone can just say... "yes it will fit" BUT a LSD is around 0- 600 and when your VDC kicks in and tries to slow a spinning wheel it will put braking forces on all of the drivetrain. if you do install an lsd it will cause a lot of stress on the center diff if the VDC is not permanently disabled. just like how we wrx owners should never do parking brake turns because it puts excessive forces on the center diff. fact is.. our cars are only 2 wheel drives. 1 wheel up front and one in the back. you will not engage an all wheel spin in our cars because we have open diffs both front and back. good luck and let us know how you make out if you go this route. :)




isn't our front diff a locking one? that why is you use the spare tire it must go on the back
 

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Does anyone know if LSD can be added to 08 WRX, I autocross in the STU class and it would help to be on par with the STI's that I compete against.
You aren't Roy, by any chance.. are you? :)

You should be able to add any of the diff options that were available for the WRX from '02-'07. In order of importance (or rather, bang for the buck) you would replace the front, middle and rear. The rear doesn't really do much.. the front inside tire is the one that always lacks traction.

The big issue is that you won't be in STU once you swap or modify a diff.. you'll be in E Street Prepared... and that's a whole new ballgame.

The good news is that there is still hope for us to do an '09 turbo swap under the Street Prepared update/backdate rules. We'll need to wait for someone to verify that the '09 engine is the same otherwise (we'd have to swap out the entire engine/turbo if there are major differences).

If you want an idea of what it takes to be competitive in ESP, check out this thread over at "the other place".
 

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Here are some things to think about before you go dumping a ton of money into your car... I've been into autox since 1996 and run a few different cars...

Learn to drive. It takes YEARS to really get good at this sport. You don't NEED the fancy diffs yet. In fact, you will go faster in the long run if you learn to drive with a handicap such as open diffs. You will also learn to go faster if you're in a slower car.

Case in point... the car I autocrossed for six years was a BSP 1986 Corvette. I bought the car as a car never taken care of, and turned it into a race car. When I was done, it was a nationally-competitive car. The reason I sold it was because I wasn't willing to spend $7500 on the fancy triple-adjustable shocks the _really_ fast people were using. My custom-built double-adjustable Konis were "only" $2200.

The car was fast. For only 275 hp (from an L98 -- torque monster), it was still very fast. I was consistently mid-pack, and I ran with a lot of nationally-competitive people (SF Bay Area). I placed mid-pack at Nationals in 2000 (22nd out of 42).

I was out of it for a few years, then I got my current WRX. I ran it completely stock and very quickly realized this thing is a completely different animal. No longer could I just stick it in 2nd and forget about it. I had to time my 1-2 shift because of the turbo. I also am learning to left-foot-brake so I can keep the turbo spooled for tight corners.

But the first thing I noticed was how the open diffs cause the inside wheels to spin. So to work around that, I've simply adjusted how I attack corners. I run very wide, carry a lot more speed into them, brake HARD, get the car turned, the wheel straight, and back on the gas as fast as humanly possible. It's working, because on the stock crappy all-season tires I still placed third in ESP, behind two older STIs on race rubber (there were eight in the class on that day).

So again, the moral of the story is this... don't be so eager to throw money at your car until you're able to make use of it. Yeah it might make you a little faster now, but I don't think it's a cost-effective way if you really want to compete.

Frankly, if you're intent on making autox a fulltime hobby, you probably want another car anyway... and run in a STOCK class so you can concentrate on driving and less on buying parts. If I was going to do it again, I would run either a Miata, or a C5-Z06.

Rob
 

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Learn to drive. It takes YEARS to really get good at this sport. You don't NEED the fancy diffs yet. In fact, you will go faster in the long run if you learn to drive with a handicap such as open diffs. You will also learn to go faster if you're in a slower car.
+1 very very good point. a diff might net you 0.3s at autox (a complete guess..), but skill will net you 4 or 5 seconds. i went from almost last place in my class when i first started and now i often win my class (i've got wheels and tires and an exhaust for the noise and that's it). i run stock class and i don't have a front sway and no adjustable shocks. get yourself some good tires and learn to drive :)
 

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i'd like an lsd just so i can have some fun in the rain :(

i have fun in the rain. power slides like crazy. surprise i havent blew anything up yet. even on dry you can get some nice donuts going.
with a stock wrx? NO WAY. i can't even get cyclones down in the rain. no lsd sucks

yes way. roughly 600 miles on it and got my first semi-donut then slid for quite a bit then my g/f procedded to smack me. its called a little e brake and some clutch kicks. your not gonna get it out of raw power on a stock wrx but once i was stage 2 she was easier to convince into doing some slides and such
 

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if i'm in the rain, i can get some power slides, but as soon as i try to do a cyclone my cars rear end goes to 1 wheel drive and I sit stationary, it really sucks :(

One thing i loved about my 02 wrx was the ability to have fun in wet parking lots
 

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you could possibly add a front or rear lsd but you would have to find some way to permanently turn off the VDC. there is actually alot to it. i found alot of interesting info over on nasioc written up by the "unabomber" himself. do the research yourself to find out what exactly has got to go into it before you buy the wrong parts on someone elses suggestion. anyone can just say... "yes it will fit" BUT a LSD is around 0- 600 and when your VDC kicks in and tries to slow a spinning wheel it will put braking forces on all of the drivetrain. if you do install an lsd it will cause a lot of stress on the center diff if the VDC is not permanently disabled. just like how we wrx owners should never do parking brake turns because it puts excessive forces on the center diff. fact is.. our cars are only 2 wheel drives. 1 wheel up front and one in the back. you will not engage an all wheel spin in our cars because we have open diffs both front and back. good luck and let us know how you make out if you go this route. :)


From what I know, that is not true. The LSD is more proactive and works before the VDC would ever do anything, the VDC is more reactive but tries to perform similar function as the LSD among other things (ie. keeping the wheels turning at the same speed, and transferring power away from the wheel that loses traction). Simply put, if a front wheel is not spinning independent of the other (which a LSD will keep it from doing), the VDC will not try to slow it down. A number of the 7th gen accord 6mt guys add LSD's to their cars, and they have VSA, and there is no problem.

The only possible thing that I could think of that could potentially cause a problem VDC-wise is if the car rotates and the VDC tries to correct the rotation by braking one wheel, however VDC doesn't cause the brakes to clamp down and lock up and really wouldn't cause any more stress on the differential than the forces of the rotation already would.

A front LSD shouldn't put any extra stress on the center diff. There is a huge difference between a handbrake, which will try to halt both rear wheels while the center diff is trying to keep them moving, and a front or rear limited slip which will only change the rotation of one wheel relative to the other wheel on the same end, but not at all keeping out from being transferred to that end.
 

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I agree with chanke's assessment. The reason the rear LSD was dropped from the WRX was because (A it was useless 99% of the time (unless doing donuts in a parking lot is a high priority for most people) and B) it was viscous and the cause of much instability in slippery conditions.. it would have worked against the VDC. A proper helical front diff would actually work to make the car more stable.. as would an uprated viscous center diff (20kg rally diff).
 

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Based on my understanding of how open and lim slip diffs work, VDC would not be impacted at all. I think you'd be fine adding a diff.

Center diff is stressed with diff in speed/load from front to rear, not side to side (which is why you need diffs on each axle as well). Yes, handbrake stopping both rear wheels while the center diff is trying to turn them adds stress to the center diff, but the factory unit is viscous, not mechanical, so prob not a big issue.
The VDC will still function the same regardless of front/rear axle diffs...if it senses wheel slip, it will selectively and mildly brake one wheel to transfer force (which benefits the mechanical function of an open diff simulating a limited slip power transfer). I believe in the case of a limited slip at the axle, VDC would not be triggered to 1 wheel because both wheels would slip together and the VDC would apply brake to both. Actually, VDC on that axle would be triggered less overall from the traction gained mechanically.

Overall, redundancy in this case would not hurt daily driving. The benefit would be retaining limited slip function while driving at the limit....for which most drivers disable VDC effectively losing this function.

EDIT: This is diff theory...I am a Toyota engineer, not Subaru so I can't say how the Subaru VDC is set up specifically although many are the same. You blow it up, your fault :)
 

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The VDC in my wrx doesn't act vastly different from any other VDC system I've ever used. It's a pretty basic system relatively speaking.
 

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hehe so you like my disclaimer 8) I agree, very simple system.
 
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