AWD and LSD or spools - discuss !

When it comes to condiments, when you get more Jam, you also tend to get more HP Sauce.*




*Artistic License# AL-C-MB-640504-10.32

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First Rally: 2001
Driver (7), Co-Driver (44)
Drivers (16)
Clerk (10), Official (7), Volunteer (4)
Cars Built (1), Engines Built (0) Cages Built (0)
Last Updated, January 4, 2015

Quote
john vanlandingham
Blame is for idiots. losers.

Edited 1 time(s). Last edit at 07/30/2014 07:35PM by Morison.

Quote
Morison
When it comes to condiments, when you get more Jam, you also tend to get more HP Sauce.

Lol!

Yes, with twice the power your sti will do things your rally car won't simply because of power.

Of course you can initiate the drift in exactly the same way in both cars, but the Sti has the jam to keep the tires spinning and continue all that sideways motion you just created. The rally car won't have the power to keep them spinning and will straighten up.

Where diffs come in, is with the weak center different in the rally car, once you get it into the turn and on the power, most of the power will be put down through the front tires (specifically inside front) because it is the most unloaded and easiest wheel to spin. Car will straighten up just like a fun car. With a tight center more of the power (5 times the power with a 20k diff) will stay rear ward and hopefully keep the rear tires spinning to continue the drift.

Technically speaking, under full throttle there is little difference between the Dccd and 20kg diff. The difference as the Dccd will open up under turn in, and they also have a mechanical rearward bias.

One benefit which has also not been discussed is braking. Braking performance is greatly improved with a tighter diff. It actually let's the rear brakes do much more work, and slow down the front end. Good Dccd programming will also lock the diff under heavy braking.

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Chris

Quote
Do It Sidewayz

Quote
Morison
When it comes to condiments, when you get more Jam, you also tend to get more HP Sauce.

Lol!

Yes, with twice the power your sti will do things your rally car won't simply because of power.

Of course you can initiate the drift in exactly the same way in both cars, but the Sti has the jam to keep the tires spinning and continue all that sideways motion you just created. The rally car won't have the power to keep them spinning and will straighten up.

Where diffs come in, is with the weak center different in the rally car, once you get it into the turn and on the power, most of the power will be put down through the front tires (specifically inside front) because it is the most unloaded and easiest wheel to spin. Car will straighten up just like a fun car. With a tight center more of the power (5 times the power with a 20k diff) will stay rear ward and hopefully keep the rear tires spinning to continue the drift.

Technically speaking, under full throttle there is little difference between the Dccd and 20kg diff. The difference as the Dccd will open up under turn in, and they also have a mechanical rearward bias.

One benefit which has also not been discussed is braking. Braking performance is greatly improved with a tighter diff. It actually let's the rear brakes do much more work, and slow down the front end. Good Dccd programming will also lock the diff under heavy braking.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Very good explanation of the 20kg , life, and everything..... "42"


now why didn't i ask this sooner ?? WHY? lol spent $370 on a front and $200 on a rear that could have gone towards a center. lol ... live and learn how dumb you were i guess ..

I definitely need to call those bara motor sports folks if they can "Re-set" a stock center for the same cost, they might be able to come up with a better setup that may allow slightly more rpm difference between the 2 ends.

I was thinking about this (way to much) last night ..
a 195/65/R15 does ~~ 833 revolutions per mile . If you are doing 60 mph , then its 833 RPM (minute)

if you are using a 4.44 Final drive then your rear drive shaft and your front (which is internal to the transmision) are both spinning at 3700 RPM . and the diff is gonna fight speed differences of 100 rpms

if your fronts stay at 60 , but your rear wants to do 58 that's going to be more than a 100 rpm difference on the output shafts (from the center diff) and will start to lock up .

http://www.idsc.ethz.ch/Courses/vehicle_dynamics_and_design/11_0_0_Steering_Theroy.pdf



it should be possible to figure out how many rpms difference i want to allow , based up on a given Arc or turn.

but this is probably past the point where i'm going to be able to drill down to a "good" answer .. let alone perfect..

so going with the default of 100, from someone who probably looked at all of this for a subaru .. is probably the wise move ? hehehe

Do you have a job?

I am actually impressed with the amount of thought you put into this idea though. Would you be blessed with the title of "piled high and deeper" by chance? :p (I am keeding around here! )

Sr dev 2 . gotta do something while programs compile, or while waiting for oracle to return results from my query ... hehehe

Quote
A1337STI
Very good explanation of the 20kg , life, and everything..... "42"


now why didn't i ask this sooner ?? WHY? lol spent $370 on a front and $200 on a rear that could have gone towards a center. lol ... live and learn how dumb you were i guess ..

I definitely need to call those bara motor sports folks if they can "Re-set" a stock center for the same cost, they might be able to come up with a better setup that may allow slightly more rpm difference between the 2 ends.

I was thinking about this (way to much) last night ..
a 195/65/R15 does ~~ 833 revolutions per mile . If you are doing 60 mph , then its 833 RPM (minute)

if you are using a 4.44 Final drive then your rear drive shaft and your front (which is internal to the transmision) are both spinning at 3700 RPM . and the diff is gonna fight speed differences of 100 rpms

if your fronts stay at 60 , but your rear wants to do 58 that's going to be more than a 100 rpm difference on the output shafts (from the center diff) and will start to lock up .

http://www.idsc.ethz.ch/Courses/vehicle_dynamics_and_design/11_0_0_Steering_Theroy.pdf



it should be possible to figure out how many rpms difference i want to allow , based up on a given Arc or turn.

but this is probably past the point where i'm going to be able to drill down to a "good" answer .. let alone perfect..

so going with the default of 100, from someone who probably looked at all of this for a subaru .. is probably the wise move ? hehehe

See where you gone wrong is where many go wrong: mistaking paper for reality.. Your RPM is one thing, your revs per mile is based on an ass-umption of a given diameter..

Is your tire inflated to 160 Pea Ess Eyes?
Is the tire made of steel and a perfect circle 650mm in diameter ALWAYS like O?

Or is it made of rubber? And is it actually infklated to 24 PSI and then does it look like this --tilted over--D ?
What is the diameter of D when on the gas? What is the diameter of the rear tire on hard braking vs the diameter of the front? Front D (tilted over) and rear O?
How many Em Ems difference..
See?
You can't calculate all that and it is significant...

So no point in wasting any calories thinking about it.

(Further, will THINKING about it result in any more control? Or better placing? No. Obviously)

In my Ford the OEM 4x4 ratio front and rear is 3.62:1
The rear diff is a 7" unit with the XXXmm dia CVs and xxmm dia half-shafts

I have a nice 7.5" 2wd rear diff with BIGGER bitchiner CVs (930 Porsche size) and bigger manlier halfsahafts but the ratio is 3.64:1....
that's a whopping 0,6% difference

Oh Noez!

I call folks who ran Ford's Group N program and ask: Answer "fuckit, run it, makes no difference in the real work"

No further thought. (Until I discovered one of my spare front diffs was 3,9 and i have some nice Supra diffs laying around with 3.9 ratio and a nice clutch plate diff... Hmmmmmmm pumped up center, and 3.9 front and rear...Hmmmmmmmmmmm..
Fuckit. Sell the whole 4x4 mess and fling that yummie T5 I have and stick a 4.3 diff in.
Result: a much quicker car where I want it to be quick: 3rd and 4th.)
3 diffs and all the problems all solved.
Less is more.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Perhaps more to the point... if the car's going to just sit in the driveway or back yard, the gear ratios don't have to be bang on the money either.

IIRC, one of the 'cheats' in the PGT subarus was to use a different drop gear in the transmission than normal. That meant the front and rear tires were turning at different speeds as a static condition. I think the idea was to slow down the back end, so you are slightly dragging the back end around, making it swing easier...

Dave Clark MKI, any thoughts on this?

---

First Rally: 2001
Driver (7), Co-Driver (44)
Drivers (16)
Clerk (10), Official (7), Volunteer (4)
Cars Built (1), Engines Built (0) Cages Built (0)
Last Updated, January 4, 2015

Quote
john vanlandingham
Blame is for idiots. losers.

Quote
Morison
Perhaps more to the point... if the car's going to just sit in the driveway or back yard, the gear ratios don't have to be bang on the money either.

IIRC, one of the 'cheats' in the PGT subarus was to use a different drop gear in the transmission than normal. That meant the front and rear tires were turning at different speeds as a static condition. I think the idea was to slow down the back end, so you are slightly dragging the back end around, making it swing easier...

Dave Clark MKI, any thoughts on this?

Yeah, never heard of that. Certain years of the WRX had 1.1:1 transfer gears and used a 3.90 front R&P ratio and a 3.54 rear R&P ratio (with the 1.1:1 transfer gears) to make a 3.90 final drive ratio. If you used the same R&P ratio with the 1.1:1 drop gears or a 1:1 center diff with the stock WRX front and rear ratios you would just cook the center viscous. With a 20kg center diff and a good rear LSD you can swing the car around just fine, no need for bizarre shenanigans.

Quote
Doivi Clarkinen

Quote
Morison
Perhaps more to the point... if the car's going to just sit in the driveway or back yard, the gear ratios don't have to be bang on the money either.

IIRC, one of the 'cheats' in the PGT subarus was to use a different drop gear in the transmission than normal. That meant the front and rear tires were turning at different speeds as a static condition. I think the idea was to slow down the back end, so you are slightly dragging the back end around, making it swing easier...

Dave Clark MKI, any thoughts on this?

Yeah, never heard of that. Certain years of the WRX had 1.1:1 transfer gears and used a 3.90 front R&P ratio and a 3.54 rear R&P ratio (with the 1.1:1 transfer gears) to make a 3.90 final drive ratio. If you used the same R&P ratio with the 1.1:1 drop gears or a 1:1 center diff with the stock WRX front and rear ratios you would just cook the center viscous. With a 20kg center diff and a good rear LSD you can swing the car around just fine, no need for bizarre shenanigans.

Wait Dave! What would all the Blue Subie drivers have to discuss why they didn't win THE BIG RALLYRACE! if they can't talk about which combo if diffs and diff controlers and programs and advanced left threshold momentum driving tricks is the secret trick that leads to fame? And FORTUNE?

And instead if they just got in buckled up, shut up and gassed it like hell

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
john vanlandingham
And instead if they just got in buckled up, shut up and gassed it like hell

Something that could apply to 95% of the field, of not 100%. It ain't a Subaru thing by any stretch.

I heard about the drop gear thing from a couple of good sources. I won't say who, just to piss John off. I know we got checked for it in the mid 2000s.

---

First Rally: 2001
Driver (7), Co-Driver (44)
Drivers (16)
Clerk (10), Official (7), Volunteer (4)
Cars Built (1), Engines Built (0) Cages Built (0)
Last Updated, January 4, 2015

Quote
john vanlandingham
Blame is for idiots. losers.

Quote
Morison

Quote
john vanlandingham
And instead if they just got in buckled up, shut up and gassed it like hell

Something that could apply to 95% of the field, of not 100%. It ain't a Subaru thing by any stretch.

I heard about the drop gear thing from a couple of good sources. I won't say who, just to piss John off. I know we got checked for it in the mid 2000s.

I don't care if you don't say, it sounds stupid, Dave Clark was being polite and it makes zero sense..so who the fuck cares---in any case with you there is a huge probability that you did not understand--ya know all that techo-gobbilygook---which THEY probably didn't understand really.

Of course it applies to all...............but for many that means just buy one diff and then get in sit down shut up and go...

For those others "Whaaaaaaaaaaaaaaaaaaaaaaa! This diff is too stiff, and tjhis diff is tooooo soft, but this diff is juuuuuust right. Which diff should I buy, so many choices, what's a girl to do?"

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Leave the front, 20kg center, grind the ramp angles on the rear. Done
GpA driving style is fun. No e brake is only minus

Quote
john vanlandingham
For those others "Whaaaaaaaaaaaaaaaaaaaaaaa! This diff is too stiff, and tjhis diff is tooooo soft, but this diff is juuuuuust right. Which diff should I buy, so many choices, what's a girl to do?"

Yah, because that never happens in the 2wd world... lol

---

First Rally: 2001
Driver (7), Co-Driver (44)
Drivers (16)
Clerk (10), Official (7), Volunteer (4)
Cars Built (1), Engines Built (0) Cages Built (0)
Last Updated, January 4, 2015

Quote
john vanlandingham
Blame is for idiots. losers.

Quote
Morison

Quote
john vanlandingham
For those others "Whaaaaaaaaaaaaaaaaaaaaaaa! This diff is too stiff, and tjhis diff is tooooo soft, but this diff is juuuuuust right. Which diff should I buy, so many choices, what's a girl to do?"

Yah, because that never happens in the 2wd world... lol

Yep, never once heard a 2wd guy whining about what he should do for controlling his center diff and the diff for the other end than the one that drives the car..
Pretty obvious to me why they don't.
But I'm sure things are different in the circles you travel in..

Wonder what pithy solutions you have for them.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.