276wtq and 210 whp......only 13psi (wastegate pressure).

still really fun in 1st, 2nd and 3rd....probably too fun for me still, but gorman is rough enough.

my 'baseline' at WG pressure was 280wtq/280whp.

I still need to see how different the car is now that I upgraded to that 20kg center diff, so the first few stages will be realllllll easy.

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Jon Burke - KI6LSW
Blog: http://psgrallywrx.blogspot.com/

So the baseline was pre restrictor? Thats the only way I can understand why the torque stayed pretty much the same but the whp dropped...

Right?

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Welcome to the cult of JVL drink the koolaid or be banned.

yes....'unrestricted' was 280/280 at 13psi...so the 'new' numbers are a bit lower torque and minus 70whp.

last year, on this same setup, I was at 325wtq/320whp at 17psi tapering down...so I expect WTQ to eventually get above 300, and whp to get to around 260 if/when we start turning up the boost.

oh, this is on a Blouch 20g turbo w/a td-05 turbine...spools very fast for its size.

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Jon Burke - KI6LSW
Blog: http://psgrallywrx.blogspot.com/

you lost me once you started talking about the particular turbo. I know nothing about them

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Welcome to the cult of JVL drink the koolaid or be banned.

That sounds about right. I think that's right around where all the Subaru's around here are on the restrictor.
The fun car is Dave Kern's Evo. 315 whp, 450 or so ft lbs, with restrictor. Hopefully he makes it to Rally Colorado.

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Grant Hughes

Not bad numbers for 13 PSI.

You'll find that upping the boost ain't going to get you much HP, but more torque.

I was around 320 wtq and 260whp....with a super flat torque curve. But judging by the state of the rings/bores after my tear down, i got reason to believe it was way down on compression...So we'll see.

The difference between 10-12 PSI and 20+ psi was like 10whp, but like a zillion ft-lbs.

What kinda fuel?




I still say the 20kg diff completely changes are car. You are going to have to work at getting the car turned a bit more. But just LFB and don't be affraid to really PUSH the car. If you drive like a grandma, you are not going to like it, and you'll think it's an understeering POS. If you toss the thing into corners and treat the steering wheel as an accessory, and not your #1 mode of turning.

Don't be affraid to stand on that skinny pedal....HARD!

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Chris

What's the rest of the units on the 20 kg diff?
I assume 20 kg/m breakaway, which is like 13.5 lbs/ft. But no clue.

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Grant Hughes

20kgf-m/100rpm

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Chris

I have no clue what that means Chris.

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Grant Hughes

NoCoast Wrote:
-------------------------------------------------------
> I have no clue what that means Chris.
>
> Grant Hughes
> www.nocoastmotorsports.net
> Denver, CO

ditto...


for reference, I know the stock WRX center diff is 4kg...the stock STI center diff is 12kg....so this one >3x stock, and almost 2x the sti.

What I'm still trying to figure out is exactly what it does besides puts more power to the rear(obviously). what I've found is, on tight corners (usually just parking the car), my front tires rub a little bit...when that rubbing starts, the center diff does something because the car pretty much comes to a halt unless you get back on the gas...no 'coasting' into parking spaces or whatever.

on tight corners my rear diff locks up too, I can hear/feel the tires chirping a little. I'm sure my stock viscous LSD will be burned up soon, lol.


if anyone has any more insight, I'd love to hear it.

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Jon Burke - KI6LSW
Blog: http://psgrallywrx.blogspot.com/

All the diffs in question are visous diffs.

Basically.... the diffs have a viscous "puck" which works as an LSD.

http://auto.howstuffworks.com/differential5.htm


Stock Subaru is 4KG (this is any Subaru)

STI offered 2 upgraded diffs 12kg and 20kg.

They all make the center diff closer to "locked" and 50/50 power/torque distribution.

It feels like it's more power to the rear, because in a tight turn (into a parking spot) the rear axle needs to turn less than the front. Normally the stock diff allows this. However the 20KG diff is keeping them locked together "tighter". So the rears need to break traction some how.

Why i say you need to "drive" or "pitch" the car, is because if you drive like a wuss, the rear end is going to push the front through the corners....trying to spin the same amount. When you pitch the car so the car is sliding and drifting, the rear tires can spin, and you get through the corner way quicker.

You will not get as much "terminal understeer" followed by "terminal oversteer". This happens because the stock diff is weak, and can and will put alot of torque to either the front/rear axle.

The 20KG diff does a better job at keeping it locked.

With the stock 4kg diff, you get into a drift, and it will put power where it is easiest, and often straighten out. It's going to be easier to spin the fronts, so it will and you'll go straight. With the 20kg, it will stay closer to locked up, and not allow as huge differences in axle speeds. You'll keep that drift going perfect!

The 20KG diff will help you when accellerating...you won't just light up the front tires on a launch, or when coming out of a corner. you'll have close to a 50/50 torque split and you'll launch like an animal, and have some nice throttle on oversteer coming out of corners.

the 20KG diff will also help alot under braking. With the stock diff, there can be a big speed differential between the front/rear axles, and this can happen under braking as well. The 20kg diff will let you use the rear brakes to slow down the fronts as well!


What burns up the stock viscous, or any viscous diff is getting the fluid hot and it breaks down (it's grease basically). The diff burns up because it is a weaker link between axles, and allows more speed difference....creating more heat.



regardless...you will love it...just keep your damn foot planted on the gas!

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Chris

Chris...thx for that. what you said about braking, I assume the same for throttle-off over steer? In rallyX, I use that alot instead of braking because its all 1st gear crap...I've gotten very good at 'throttle off into corner, power through corner, and then either throttle off snap-steering (for connected corners) or just keep my foot planted into whatever comes next.

I have a feeling my driving style will do well with this diff, I just need to get used to higher speeds. I do know my current suspension setup oversteers a little at higher speeds on dirt, so that might help. I've removed both sway bars for Gorman.

This weekend is going to be a blast.

I'll be sure to replace my rear diff fluid right afterwards too.

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Jon Burke - KI6LSW
Blog: http://psgrallywrx.blogspot.com/

So there's not really a breakaway torque at which time it starts to slip like a clutch type diff since it's viscous.
There's a super tight (ie high breakaway torque) clutch type center locally that I'm trying to get Mark to put in his car. It acts more like a locked diff though, which I think would go well with his driving style.

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Grant Hughes

I believe there probably is a break away torque on these things as well....
They are locked up pretty hard, until they slip.


I've driven with both welded, stock, and the 20KG diff, and it is byfar my favorite.

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Chris

this explains the Subaru Viscous unit better

http://www.mrtrally.com.au/performance/viscous_coupling.htm

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Chris