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Reply With QuoteYeah i mean what all do they do to rally prep a car? I havent done anything and i dont know if i even will. But i do want to learn about it.
This is a discussion on E brake mods??? within the Interior Mods forums, part of the Tech & Modifying & General Repairs category; Originally Posted by BEASTmode632 Its simply to just play around. Is that not cool to you guys? It would be, ...
It would be, other than the fact the cars have center differentials in them. To put that in common tongue, an (important) component of the car must direct power to/from the front/rear wheels. If you purposely halt the rear wheels, the differential gets the short end of the stick. Especially with a parking brake that is more capable than the stock one, you could do some serious damage to your center differential in a relatively short amount of time. Your differential is not meant for it.Originally Posted by BEASTmode632
2011 STi Build Log
Resident Tuner @ WTF Tuning, LLC
-Part 1 - Reading, Data Logging, and Analyzing Data
-Part 2 - Turbocharger 101 & Basic Boost Control
-Part 3 - EcuFlash, Experimental Defintions, and a Drive By Wire Intro
Yeah i mean what all do they do to rally prep a car? I havent done anything and i dont know if i even will. But i do want to learn about it.
2010 Subaru Impreza WRX Hatch
Mods : Yakima Roof Rack, Perrin catted DP, Perrin CAI, Perrin shifter bushings, Perrin AP stage 2, Ebay/Custom 3" cat back, carbon Subaru emblems, blacked out tail lights, Cobb STS
So if the car isnt putting power to the wheels as the ebrake is pulled would it still hurt the center diff?
2010 Subaru Impreza WRX Hatch
Mods : Yakima Roof Rack, Perrin catted DP, Perrin CAI, Perrin shifter bushings, Perrin AP stage 2, Ebay/Custom 3" cat back, carbon Subaru emblems, blacked out tail lights, Cobb STS
You would need a much stronger center differential that is intended to take the abuse to start with. After that, you would probably want a few spares on hand. It varies based off of drive line and abuse. The easiest would just be to replace it if you break it. Changing the fluid frequently wouldn't be a bad idea either.
It's easy to get caught up on our center diff's breaking due to "rally" racing, but a commonly overlooked note is that the differentials take a lot of abuse on a road track as well. When turning on a road course, your wheels slide as well - at higher speeds. After my second track day, my rear differential had apparently boiled over/overflowed just from the abuse of 4x25 minute sessions. When I changed the fluid, it looked like tar. The center differential fluid was still in good shape, but I wasn't pulling the parking brake either.
2011 STi Build Log
Resident Tuner @ WTF Tuning, LLC
-Part 1 - Reading, Data Logging, and Analyzing Data
-Part 2 - Turbocharger 101 & Basic Boost Control
-Part 3 - EcuFlash, Experimental Defintions, and a Drive By Wire Intro
In the STIs they have that knob that moves power towards the front or rear. How exactly does work and can we make it happen on the wrxs with our transmissions?
2010 Subaru Impreza WRX Hatch
Mods : Yakima Roof Rack, Perrin catted DP, Perrin CAI, Perrin shifter bushings, Perrin AP stage 2, Ebay/Custom 3" cat back, carbon Subaru emblems, blacked out tail lights, Cobb STS
DCCD Explained
may be helpful
Marky Mark
2002 Stage 2.3 PSM Bugeye tuned by Matty at WTFtuning
Bugeye Mafia #397, High Mileage Club, WTF Tuning Intern
My bugeye build
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First Mods and other useful info!
GM EBCS/ Hallman MBC Hybrid boost setup diagram
No. That's one of the special features you pay the premium price for. The STI has an electrionically-controlled center differential, which is very different from the relatively archaic (but highly functional) viscous coupling used in the WRX. The design is totally different between the two.
Isaac -- 2003 WRX sedan Stg II
Proud owner of a N.E.R.D, Member 1.38×10-23
He who shall be last, shall be sideways and smiling... - Jeremy Clarkson
I'm fairly certain that it would be more cost effective to just sell your wrx and buy a sti.
- William
First Mods: What to do and what not to do
2012 WRB WRX base hatchback - Stage 1 with a meaty area under the curve thanks to Mattypants @ WTF Tuning, LLC
Previous Cars: 2004 RSX-S, 1998 Grand Prix GTP
"Isn't it amazing how smart you feel when you just aren't being stupid?"
Bit hazy on this stuff, for the record.
It controls the tendency for the center differential to lock, despite the common marketing ploy. The STi transmisison varies from a fully open differential (60% torque rear, 40% torque front) for performance reasons to a fully locked differential (50/50 to help get traction if a wheel starts spinning too much - think of it like a mechanical linkage). When the e-brake is pulled in the STi, the car automatically opens the differential to help prevent the differential from locking and fighting itself. While this does reduce the strain on the differential, it is still hard on it.
A WRX has an entirely different center differential. I believe it is a viscous differential. While it acts like an open differential for the most part, it uses a series of disks inside of a fluid. As the fluid heats up, the discs engage or disengage. Hence, stressing the differential isn't the best idea in the world.
Simple google search kicks this up : Differential FAQ: Consolidated and made relevant for Legacy owners - Subaru Legacy Forums
Not bad reading.
2011 STi Build Log
Resident Tuner @ WTF Tuning, LLC
-Part 1 - Reading, Data Logging, and Analyzing Data
-Part 2 - Turbocharger 101 & Basic Boost Control
-Part 3 - EcuFlash, Experimental Defintions, and a Drive By Wire Intro
A fly off handbrake with a switch-disengage center is used, if and only if the rules allow it. If the rules don't or the parts are not homologated, they run whatever is homologated and replace what breaks before park ferme and/or between events.
The short answer is yes, but with $. Do the math and see what's cheapest.
WRX Info Links, Courtesy TheJ
I'm mixing the barley with the grape again. Rory Gallagher
Själen är större än världen. Ricky Bruch
Let the liquor do the thinking. Jim Lahey
DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.
Do you have a extra ~$500k laying around to be like a rally prepped car?
Here's an excellent video (albeit a bit old) describing fluid couplings. Although the video is mostly speaking in terms of automatic transmissions, and viscous coupling designs have largely evolved past this exact design, the same concepts can be applied to the viscous center differential in the WRX. Since the system uses fluid dynamics alone to operate, it can't adjust dynamically to one side of the coupling suddenly locking (as it would if you pulled the ebake suddenly). In this instance, the internal oil is pumped against the coupling blades, but cannot turn them, causing extreme shear stress against the coupling blades or disks and rapidly heating the oil beyond it's useful operating temperature. This scenario can and does snap the internal disks, destroying the coupling.
The STI's differential, on the otherhand is not purely bound by the fluid dynamics and coupling design, using a more convential clutch design (I believe) to control torque front and rear. Although it too is stressed by locking the parking brake, it is more able to cope with this stress by allowing the front wheels more torque. That said, locking both rear wheels isn't something to make a habit of in any AWD car, unless you are doing such in a motorsports scenario with the understanding that parts will fail, and a budget to support that.
Last edited by Rambo; 03-12-2013 at 10:35 AM.
Isaac -- 2003 WRX sedan Stg II
Proud owner of a N.E.R.D, Member 1.38×10-23
He who shall be last, shall be sideways and smiling... - Jeremy Clarkson
Now thats the helpful information i was looking for. i really appreciate every ones serious input. ill be reading up on those posts when i get more time.
2010 Subaru Impreza WRX Hatch
Mods : Yakima Roof Rack, Perrin catted DP, Perrin CAI, Perrin shifter bushings, Perrin AP stage 2, Ebay/Custom 3" cat back, carbon Subaru emblems, blacked out tail lights, Cobb STS
Wow, great video! It's older than I am!
--Ray
Grandfather of the Bugeye Mafia
Proud owner of a N.E.R.D.
LooI believe in rally cars, when they pull the hand brake, it also somehow disengages the rear wheels from the center diff.
edit:
Here is a video of tanner faust taking about his fiesta, at about a minute in he briefly talks about the hand brake. Also talks about some other pretty interesting things about a rally car!
https://www.youtube.com/watch?v=IpDz...e_gdata_player
Last edited by RichD514; 03-12-2013 at 11:29 AM.
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