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malibuguy
malibuguy New Reader
11/13/17 9:30 p.m.

no budget for an LSD, I am running a 23mm front (I dont have a measurement for the stock one) and a 19mm rear sway bar on my Yaris sedan.

Its a DD I like to play with, stiffest lowering springs, tokico blues, poly bushings up front.

Corner exit with any sort of trailing cornering results in just inside wheel spin.  Car is also very tailhappy, which works well in with carrying speed deeper into corners.

removing the front sway bar is a PITA since its above the subframe..should I  just remove the links and see what happens?  the rear is a sinch...2 bolts...

mad_machine
mad_machine MegaDork
11/13/17 9:34 p.m.

can't hurt to remove the links and see you can zip tie it up out of the way to find out how that helps your handling.

I removed the bar from a 1988 Hyundai Excel. This was a car with terminal understeer even when not doing anything stupid or illegal. I once put it straight up on a kerb at 20mph because the car just went straight in the rain when I tried to turn. Removing the front bar made it a slightly tailhappy good handling little econobox, even on the crappy tyres it was sitting on

Pete Gossett
Pete Gossett MegaDork
11/13/17 9:37 p.m.

In reply to malibuguy :

Yes, unhooking one end link will have the same effect as removing the bar. Depending on your spring rates, you may end up with too much body roll, and thus too much camber loss - or it could work out well.

The other thing you can try is to LFB as you roll onto the throttle at corner exit. If you have significant forward bias you may be able to drag the inside/spinning wheel enough to transfer torque to the outside wheel. 

rslifkin
rslifkin SuperDork
11/14/17 7:55 a.m.

If you can keep scrub radius reasonable (might be easy if you've already added camber with camber plates) and make the tires fit under the body, add wheel spacers (at least up front).  The wider front track will reduce weight transfer off the inside front wheel, giving a bit more weight / traction on the inside front coming out of a corner under power.  It'll likely make the car a bit more tail happy at the limit though (unless you widen the rear by an equal amount).  

pinchvalve
pinchvalve MegaDork
11/14/17 8:13 a.m.

The Front bar on the Fiesta ST is above the subframe as well, and it is a PITA to swap out.  Remove one link and the bar is useless and won't flop around.

GameboyRMH
GameboyRMH MegaDork
11/14/17 8:21 a.m.

Unlinking or removing the front sway bar will improve corner exit traction, but you'll get increased body roll and less responsive steering. Save up for the LSD. It's a problem I know well.

Driven5
Driven5 SuperDork
11/14/17 9:51 a.m.

No budget for an LSD?  No problem.  Lincoln locker to the rescue. devil

KyAllroad (Jeremy)
KyAllroad (Jeremy) PowerDork
11/14/17 10:42 a.m.

Is the rear bar stiffer than stock?  That has always been what I've been told is the hot ticket for FWD autocrossers: huge rear bar.

Can you fit more rubber on the front end?  More is better laugh

Stefan
Stefan MegaDork
11/14/17 11:06 a.m.
GameboyRMH said:

Unlinking or removing the front sway bar will improve corner exit traction, but you'll get increased body roll and less responsive steering. Save up for the LSD. It's a problem I know well.

To get the responsiveness back, increase the spring and damper rate accordingly.  There are ways to calculate the effective spring rate of a sway bar and usually for strut equipped cars the effective spring rate is 1:1.

The unlinked bar will reduce (not eliminate) the tendency for the inside tire to lift thanks to the lack of the bar. 

The increased spring rate will reduce body roll and increase transient response.

The drawback is that this can make the car less pleasant to drive on the street.

Proper damper tuning will make a huge difference in how the car feels on rough pavement, which is rarely inexpensive or easy.

NEALSMO
NEALSMO UberDork
11/14/17 11:19 a.m.

No front bar and big rear bar was the hot ticket on my MKII GTI.  YMMV

Trackmouse
Trackmouse SuperDork
11/14/17 12:10 p.m.

What is your front spring rate? Softening that might allow you to use the left foot braking technique to transfer weight back down on the tire. 

Robbie
Robbie PowerDork
11/14/17 3:25 p.m.

What about using air pressure difference from one side to the other? I have never tried it but it may help.

All autoxes and tracks turn predominantly one way (even though yes they do go both ways). Maybe sacrificing the turn in one direction is worth it for a gain in the other direction.

fanfoy
fanfoy Dork
11/14/17 3:32 p.m.

One answer: front axle fiddle brakes...

Always wanted someone to try that out.

Robbie
Robbie PowerDork
11/14/17 3:43 p.m.
fanfoy said:

One answer: front axle fiddle brakes...

Always wanted someone to try that out.

Another is to repurpose the abs wheel speed sensors and brake control unit to make a diy electronic LSD (use an Arduino to compare the front wheels speeds and if they differ by greater than x% then apply brakes to the faster wheel).

I might actually have to try that...

Knurled.
Knurled. MegaDork
11/14/17 4:47 p.m.
malibuguy said:

no budget for an LSD, I am running a 23mm front (I dont have a measurement for the stock one) and a 19mm rear sway bar on my Yaris sedan.

Its a DD I like to play with, stiffest lowering springs, tokico blues, poly bushings up front.

Corner exit with any sort of trailing cornering results in just inside wheel spin.  Car is also very tailhappy, which works well in with carrying speed deeper into corners.

removing the front sway bar is a PITA since its above the subframe..should I  just remove the links and see what happens?  the rear is a sinch...2 bolts...

The best thing I ever did to my Golf (A2 chassis) was lower the rear two inches.  It looked stupid, but the front end was PLANTED on corner exit.  Car had the GTI front sway bar and a plated rear beam, so basically "19mm front and almost infinite rear".  I de-plated the bar after lowering and it still had corner exit grip like you wouldn't believe.

This on a twist beam vehicle.  One of the nice things about twist beams is that the roll center is at ground level.  Changing ride height doesn't make the suspension geometry do wonky things laterally.  So, lowering the rear that much made the rear CG lower, which reduced the roll torque against the suspension, which made it actually corner on four wheels and not three, so the rear end wasn't flopping over and unloading the inside FRONT, so the thing would accelerate out of corners like some sort of mutant.

Adding rear bar on a twist beam is usually pointless.  Removing front bar is also usually pointless.  Both mostly dictate how far off the ground the inside rear is more than anything.  If you're on three wheels, ADDING more front bar will often increase front grip because you're losing less camber due to body roll.  But the real key is doing something about keeping the car down on all four wheels to begin with.  Once one end is off the ground, that end has 100% weight transfer, and trying to alter roll stiffness distribution has no effect.

malibuguy
malibuguy New Reader
11/14/17 5:08 p.m.

all valid suggestions.

this is car is used for an event here called the "refrigerator bowl" which is basically a closed off section of a road course and ran like an AutoCross.  Its hella fun and this car is really good at it.  Since it loves to dance and rotate its a friggen hoot!  BUT it just cannot put down its whopping 107/110 WHP/WTQ down on corner exit & I feel Im loosing a bunch in those areas.

I was running my DZ102 tires (195/50-16) at 27/24psi by the end of the day this past sunday.

I have some old 225/45-15 r6 tires and 205/50 a6 tires.  I'm thinking of setting up my Koseis with the 225s up front and 205s out back.  The rear tires do not get to generate much heat, so I think the a6 would work perfect back there. 

Knurled.
Knurled. MegaDork
11/14/17 5:47 p.m.

FWIW, I learned about the "make the back end as low as possible" idea from Improved Touring racers.  Limited slips hurt turn-in and mid-corner grip, you see, so some people just don't like them.

 

Oddly enough it also works on multilink rear cars that aren't as tall as a bus.  Dropping the back of Teh Volvo and softening the rear shocks to their minimum noticably improved corner exit grip.  Don't disturb the front suspension while it's trying to work, is the general idea.

malibuguy
malibuguy New Reader
11/14/17 9:29 p.m.

Maybe I could get some spare stock rear springs and chop em a little??

Robbie
Robbie PowerDork
11/14/17 9:56 p.m.

In reply to Knurled. :

That is interesting. I'm going to have to try it.

nutherjrfan
nutherjrfan Dork
11/15/17 12:05 a.m.

Corner entry fwd specific is also important. Don't ask me though. I'm just remembering an old CCC supplement.smiley

GameboyRMH
GameboyRMH MegaDork
11/15/17 9:19 a.m.
Knurled. said:

FWIW, I learned about the "make the back end as low as possible" idea from Improved Touring racers.  Limited slips hurt turn-in and mid-corner grip, you see, so some people just don't like them.

Depends what kind, a helical gear type LSD has no negative handling effects, but they also don't limit slip a whole lot, which is always the tradeoff. There's a whole spectrum between handling and forward traction that goes like this: Open diff, helical gear, e-diff, viscous, 1-way clutch-type, 2-way clutch type, 2.5-way clutch type, cam-and-pawl, Detroit locker, no diff (spool/welded). The first 5 have very little to no negative handling effect (with mild settings, where applicable).

malibuguy
malibuguy New Reader
11/15/17 10:59 a.m.

I had a TRD unit in my old tercel that served track duty and it was a helical unit.  It was excellent 

Knurled.
Knurled. MegaDork
11/16/17 5:43 a.m.
Robbie said:
fanfoy said:

One answer: front axle fiddle brakes...

Always wanted someone to try that out.

Another is to repurpose the abs wheel speed sensors and brake control unit to make a diy electronic LSD (use an Arduino to compare the front wheels speeds and if they differ by greater than x% then apply brakes to the faster wheel).

I might actually have to try that...

One of the compelling reasons to buy a Focus ST.

 

SAAB and Volvo do/did their traction control by comparing front ABS signals.  If both wheels are spinning equally, traction control won't cut in.  So if both tires are spinning at the same rate, the electronics will happily let you do a rolling burnout...

 

But this is different than pre-emptively applying one brake to alter cornering.   I don't know if any of the common ABS modules are hacked.  PCM hacking is a thing in part because the code manages to get slipped out (social engineering is way more effective than reverse engineering) but it seems that ABS code is locked down super tight for liability reasons.  If you mess up tuning your engine or transmission, you break it.  If you mess up your braking algorithms, you might crash into someone.

TED_fiestaHP
TED_fiestaHP Reader
11/16/17 6:55 a.m.

  Wheel spin with front drive is reduced by not letting the inside front wheel lift.   One way use stiff front springs and no front sway bar.  The stiff front springs basically provide front sway resistance but don't lift the inside front wheel.   You do want a rear sway bar.  Set up right it will corner on 3 wheels, it should lift the inside rear wheel.

     But without a limited slip diff you can still get some wheel spin.

GameboyRMH
GameboyRMH MegaDork
11/16/17 6:56 a.m.
Knurled. said:

But this is different than pre-emptively applying one brake to alter cornering.   I don't know if any of the common ABS modules are hacked.  PCM hacking is a thing in part because the code manages to get slipped out (social engineering is way more effective than reverse engineering) but it seems that ABS code is locked down super tight for liability reasons.  If you mess up tuning your engine or transmission, you break it.  If you mess up your braking algorithms, you might crash into someone.

I don't know of any "open" ABS modules. The only ones I know of that are configurable at all are mad-money high-end racing units.

Applying one brake to alter cornering is called active yaw control, the FiST/FoST/FoRS have this as well. Electric cars with individual wheel motors can apply regen on one side and power on the other to get a similar effect.

Using the ABS system to keep wheelspin in check with the brakes is called an e-diff or e-LSD and it's very common on modern cars. The big downside of that system is greatly accelerated brake wear.

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