[FM2] Documenting a tune: A850 Audi RS4

[bimmerlovere39]

I'm going to try something.  Basically, I'm going to blog/keep constant notes on this build in the post.  From purchase to when I would normally post it, it'll be here.  Maybe I'll even turn it into a story.  Maybe. 

The car?  A new Audi RS4.

Note: All times are EST.

Note 2: If you don't feel like reading, the tune's in the second post.


Feb 16, 9:43pm - Heading over to the Audi dealership to buy the car, a silver (4^th color) 2006 RS4.  Taking a first drive in the car while taking her back to the shop.  Strange, I don't remember this road looking so much like Laguna Seca...

Feb 16, 9:48pm - As expected, the primary handling trait here seems to be understeer.  A little bit of trail braking helps take care of this.  The brakes are pretty good, and the engine and transmission are seriously impressive, even stock.  The car feels heavy, but not as heavy as expected.

Feb 16, 9:51pm - Well, we're at the shop.  Time to get her into A-Class racing form.  The first priority is lightening this thing up.  Race weight reduction is used, bringing the car up to an uncomfortably high 795PI - there isn't going to be alot of wiggle room with engine and tires.  Round out the chassis with full race parts.  That brings the PI to 807...

Feb 16, 9:56pm - On to tires.  Racing slicks aren't going to work here.  It looks like DOTs are the only option.  We can, however, fit nice, wide (275mm) DOTs.  I'm going with the Hoosiers.  That puts us at 846PI, just enough to add on a set of lightweight OZ Superturismo GT race wheels, bringing us to A850.  Looks like the engine is staying stock.  Off to the racetrack!

Feb 16, 10:00pm - Painted the wheels grey and the brakes red, then headed off to the track - Sebring Short.  I can immediately tell just how much more competent the car is.

Feb 16, 10:05pm - After turning a couple of laps, a couple of conclusions: the car is, like most cars, overgeared with the default ratios.  Solution: Ratios changed to match the BMW E92 M3.  I'm going to start with a 3.91 FD.  The tires are off pressure when hot: the fronts are at 34psi, the rears 33psi.  Solution:  -2psi front, -1psi rear.  Tire temps vary too much across the tire, more signifigantly up front than out back.  Solution: More negative camber (to -0.9 front, -0.7 rear)

Feb 16, 10:14pm - The previous changes have cut 1.2 seconds off fastest lap

Feb 16, 10:16pm - Car is a little slow to react, and the turn-in isn't quite where I'd like it.  Solutions:  Changed rear differential settings to 60%/45%.  Shocks stiffened up into the typical JEi range.  Rebound is now 11.5/11, bump is 8.0/8.0

Feb 16, 10:23pm - The brakes are a little dodgy, so the bias is now 49%/51%.  Pressure is at 103%.  After looking at the suspension travel telemetry, the car has way too much body roll, and is bottoming out to frequently.  Springs are changed to 600.1 lb/in units front and rear.  ARBs are taken to a more balanced 11.04 Front and Rear.

Feb 16, 10:30pm - The car feels like it is coming together now.  We've got a bit of understeer and (again) we're missing some front-end bite on turn-in, so I'm taking the front ARB down to 10.84.

Feb 16, 10:35pm - She handles quite well off-throttle now.  The biggest issue now is some on-throttle understeer.  I'm setting the center diff to 33/67 - hopefully this'll help me steer the car with the throttle more.

Feb 16, 10:38pm - That moved it in the right direction, but not quite far enough.  I'm taking the center diff to 30/70 Edit:  This gave me a nice, smooth, four-wheel drift... straight into a tire wall

Feb 16, 10:45pm - The car is handling really well now.  Only last check of tire temps reveals a need for slightly higher camber numbers, bringing camber to -1.0/-0.9

Feb 16, 10:49pm - Those camber numbers made me ~0.1 faster, but alot less consistent, and they added more understeer.  I'm reverting back to the previous settings of -0.9/-0.7

Feb 16, 10:51pm - I think I'm done with this car on Sebring for now.  I'm going to take it to Mugello Short for a couple of laps.

Feb 16, 10:57pm - Car felt pretty good - a little stiff and a little understeery, but that can be fixed.  I'll post up the tune now.

Feb 16, 11:04pm - I'm getting off the 360 for the night.  The tune is posted up, and I'll continue work on this car tomorrow.  And as a reward for reading (or just scrolling past) the above wall of text, here's a pretty picture:



Feb 17, 12:27pm - I'm taking the car out on Tsukuba for a couple of laps.  We'll see how my tune holds up the morning after...

Feb 17, 12:29pm - Well, we've still got understeer.  I'm going to try taking twenty lb/in out of the front springs.

Feb 17, 12:33pm - I'm listening to LarryCR.  Rear Toe is now at +0.1

Feb 17, 12:41pm - Larry's advice worked really well.  Tune is now updated to v1.7 and posted.

[bimmerlovere39]

2006 Audi RS4, PI: A850
Documenting a Tune, v1.7

Benchmarks
0-60: 3.856
0-100: 8.241
Top Speed: 188.6

60-0: 110.4
100-0: 291.2

g's @ 60: 1.09
g's @ 120: 1.06

Modifications
Engine and Power: Stock
Platform and Handling: Full Race with Race Weight Reduction
Wheels & Tires: 275/30R18 Hoosier DOT Compound on OZ Superturismo (Race) wheels
Aero: Stock

Settings (F/R)
Tire Pressure: 28/29

Gearing:
FD: 3.91
1st: 4.05
2nd: 2.37
3rd: 1.58
4th: 1.19
5th: 1.00
6th: 0.87

Alignment:
Camber: -0.9/-0.7
Toe: 0.0/+0.1
Caster: 5.0

Anti-Roll Bars: 10.84/11.04

Springs: 580.1/600.1

Ride Height: 5.3/5.3

Rebound Damping: 11.5/11.0
Bump Damping: 8.0/8.0

Braking Balance: 49% front
Brake Pressure: 103%

Differential:
Front Accel: 45%
Front Decel: 0%
Rear Accel: 60%
Rear Decel: 45%
Torque Split: 30/70

[larryCR]

Nice job documenting your tuning process.

Have you tried some toe out on the rear to help rotate the car?

Nice wheels, too, but I'm glad I'm not the one that has to keep the brake dust cleared out of them.

[bimmerlovere39]

I tend to shy away from toe out in the rear.  I may give it a try, but I perfer to do it with ARBs/Shocks/Diffs.

EDIT: Thanks for the complement, btw 

Hm... the springs help, but I could use a little more rotation... you're faster than me and you own one of these, so I'll take your advice.  Let's see how it works 

[larryCR]

Hm... the springs help, but I could use a little more rotation... you're faster than me and you own one of these, so I'll take your advice.  Let's see how it works 

I think the notion that I'm faster than you is arguable. Older for sure.

[bimmerlovere39]

Hm... the springs help, but I could use a little more rotation... you're faster than me and you own one of these, so I'll take your advice.  Let's see how it works 

I think the notion that I'm faster than you is arguable. Older for sure.

I think I'm the youngest on the board, so it doesn't take much to be older than me 

I tried it - it worked really, really well.  The car felt ~200lbs lighter from the toe alone. 

The tune is updated - v1.7 now.  Interestingly, the changes to the springs and toe resulted in a couple feet shorter 60-0 stopping distances, but about a foot longer in the 100-0.  Odd.  I also gained 0.01g @ 120.  Cool. 

[fndrbndr]

Nice wheels, too, but I'm glad I'm not the one that has to keep the brake dust cleared out of them.

My Chrysler comes with similar wheels stock.  I've given up on keeping them purty.  I put a lot of time into it when the car was new (to me).  Now, however, I drive twice a week, if that, and see little reason to put in the effort. 

[larryCR]

I tried it - it worked really, really well.  The car felt ~200lbs lighter from the toe alone. 

The tune is updated - v1.7 now.  Interestingly, the changes to the springs and toe resulted in a couple feet shorter 60-0 stopping distances, but about a foot longer in the 100-0.  Odd.  I also gained 0.01g @ 120.  Cool. 

Good to know. Somebody on this board talked about some toe out to get the AWD cars to manuever better. It has alway made a big difference for me too.

[larryCR]

Another car you might want to check out for A class is the '07 TT S Line from the new DLC. I took one out of the box, upgraded it to A850 (grip first then power), tweaked the toe a bit, and bested my previous time at Tsukuba (set with an Evo 9). The car still has a lot of understeer to get dialed out, but it seems to have a lot of potential.