Manipulate the Weight Bias (Original Thread)

[Blooze]

[Edit 12/03/10 by Blooze] This is the original thread from back in Forza II days when the Wb tuning stuff was first conceived.

In fact, this is the thread over on the Daught.GNet where it really got started before we got a belly full of that place and revolted and bolted.

First Mention of Weight Bias Tooning


Well this needed to be broken out as a separate thread anyhow...  

A little more on the Charger Saga.  Last night 4 times in the top 1000 - 3 in the top 500 - 1 in the top 100.  You don't know how monumental that is for me.  I wonder what I would get if I gave up the full weight reduction for the slicks, or if I can.  It doesn't matter.  I wanted an A Class car to get the Oval out of my hair and the Charger are it.

The Charger build was quite simply a stock 55% Wb build.  I did my usual slight stiffening of the springs and ARB with a slight nod to the rear and wound up with a final bias of 54.5%   I'm serious.  It ran nice.  Better tires is all it needs.
 

I looked at the spring telemetry and it looked absolutely normal, and the thing handled bumps like a champ!  WTF!?  The rear end is practically solid at this point!

Do you suppose that there is a dummy proofing algorythm that reverts to stock parameters if the program runs across a certain level of outlandish?


I think the bone in the soup is going to be putting a 55 build on a 911 RS - I am off to do just that.  Later on I am going to finish the data sheets up and attach them to this thread.  That will be cool.

Welcome to the new digs...

 

[TheTechnobear]

doh, you really have shut up shop and moved over

ive just posted findings about weight changes and how they relate to springs...

shall i add to a separate thread, as its not really about bias, more about unsprung weight - which in itself is yet to be proved to make a difference

[Blooze]

Welcome... 

Sure, call it something about unsprung weight.

thanks

[Big Mooing Cow]

Do you suppose that there is a dummy proofing algorythm that reverts to stock parameters if the program runs across a certain level of outlandish?


I think the bone in the soup is going to be putting a 55 build on a 911 RS - I am off to do just that.  Later on I am going to finish the data sheets up and attach them to this thread.  That will be cool.

I don't think it's a safety mechanism, as it seems the changes did have progressively more effect on the car as I cranked them.  But I wouldn't be surprised if there was some sort of non-linear scaling of the effects of spring strength based on the way the car drove.  I was really surprised how it seemed like I could crank the settings all over the place and the car was still driveable.  Anyone who has driven a Miata in real life would tell you that a stiffer rear end is the LAST thing it needs!

When you tune the 911, if you aren't familiar with the car, make sure you drive it stock for a bit first to get the feel of it.  Try a track with a lot of trail braking opportunities like Sebring Club.  That car is one of the few that I could easily distinguish from any other car in the game in a double-blind.  It just FEELS different than most cars.  It really hammers home the feeling that there's a ton of weight in the rear keeping the tires hooked up.  I'm not the most observant driver, but it was pretty easy to feel that the Miata wasn't anything like the 911 with the settings I tried last night.

[TheTechnobear]

I tried a 50 build on the 911 T3.3 -  was all over the place under braking.
then tried a 63 on it, which was i thought much better (well cured the (many) problems i have with porkers ) but was too much - understeer
i reckon for me, around 57 WB is going to be around right, but will keep adjusting till i can get it.

btw, what are you guys doing with the ride height?  i figured if you were leveling the WB it could be levelled as well?
(on a different car, i noticed once i changed the WB, i also had to adjust the aero for i believe similar reasons)

if this was really WB, isnt the usual aim 50/50? but seems like we are heading for the 55~58

well, back to the track, gotta see if i can actually get to like a 911
 
update: tried 55 and then 57... 57 was actually quite good for me, actually starting to like this strange cars;)
think, even better would be 56-56.5, but think im gonna go try some other cars, to see if i can get similar results

[bimmerlovere39]

btw, what are you guys doing with the ride height?  i figured if you were leveling the WB it could be levelled as well?
(on a different car, i noticed once i changed the WB, i also had to adjust the aero for i believe similar reasons)

if this was really WB, isnt the usual aim 50/50? but seems like we are heading for the 55~58

Two really good points here. 

The ride height brings up a good point.  As does the mention of Aero.  Even without wings and the like, the stock cars have lift, which changes the weight to the ground as speed changes... and not always by the same F&R

Also, don't forget, we are wanting slightly softer rear springs to help hook up the power.

[Blooze]

The 911 RS has turned out real well, I think.  The "I think" part is that it is marginal for power in the B class.  Later, I may trade the slicks in on some DOTs and some Goodies from down to the local Speed Mart.  The handling is such that I am pretty sure I can give some back.

This time I went straight for the 54.5% build and then added the stiffeners across the board, instead of shaping them like I usually do.  I increased the ARBs by 14% and the springs/dampers by 3%.  Along with that I added a tenth of Damping agent to help the grip on exit.  It really drives nice, and did so from the start.  I tuned this to the calculator and drove it without so much as peek and it was right on right out of the box.

I may do some serious gear tweakage later on.  I have been letting a bunch of the gear work go, settling for just adjusting the FD and taking the Spreader suggestion.

[TheTechnobear]

i assume you mean 54.5% build?
"shaping like i usually do" = 
when you say you stiffened arbs by 14%, is that 14% F and R i.e. you leave the ratio at 54.5? and same with your 3% dampers?


ive tried a couple more FR cars, and getting similar issues with each (out the box) - power oversteer. i think i need to tweek the dampers a bit. in retrospec i think thats why i let the 911T be pushed to 57%,  perhaps i could have used lower, and 'cured' the oversteer instead.

[Blooze]

Yeah, I need a nap, that's for sure.  54.5% is correct.  I edited it.  Thanks.

Shaping = my term because because that is more or less how I do it in my mind.  It is modifying the springs stiffness for stiffness reasons as well as modifying what turns out to be now, the Wb.  Liike for the ARBs, I might have increased the front by 16% and the rear by 20%, or perhaps the other way around for this car.

Modifying both ends the same amount maintains the Wb ratio.

Why don't you give 54.5% a try on one of your cars, see what you think of that.

[TheTechnobear]

Yeah, I need a nap, that's for sure.  54.5% is correct.  I edited it.  Thanks.

Shaping = my term because because that is more or less how I do it in my mind.  It is modifying the springs stiffness for stiffness reasons as well as modifying what turns out to be now, the Wb.  Liike for the ARBs, I might have increased the front by 16% and the rear by 20%, or perhaps the other way around for this car.

Modifying both ends the same amount maintains the Wb ratio.

Why don't you give 54.5% a try on one of your cars, see what you think of that.

sure I'll try 54.5,

i think the comment about maintain the WB ratio, is the intresting one, i.e. you are just stiffening a components (arb, bound, damper) -  but still keeping the F/R ratio of each component to 54.5?   my assumption is that this is the 'ideal' appoach, as it keeps everything simple... but so far, as mentioned, i seem to be getting oversteer.

a couple of things that have been floating around in my head to try if the 54.5/54.5/54.5/54.5 (arb,springs,rebound,bump) isnt working are:
a) using the variance of the stock setup, to influence the new setup  (i.e. if spring rate is calculate to be 48%, and ARB 46% ... then perhaps modified should be 54.5, 52.5)
b) perhaps the springs should be 54.5, but everything could be neutral  (if you look at current setup, you are multiplying the effect of everything by 3 (ARB,Spring,Damper)
c) a bit like (b) , perhap the avg, for 4 components should be WB, i.e. 53.5/54.5/54.5/55.5 is valid
d) 54.5, is setup, and then manually adjust to get the feel right   
 
anyways, i'll try 54.5, i currently am testing on 911T (Stock), etype (B), MR-s (B) ... i think quite a tricky bunch
i need to also figure out on these what to do with ride height and aero ... i levelled them... i need to try stock
also perhaps the stiffening will help, and maintaining WB,  perhaps im just getting roll - i can imagine the 911 and etype both having quite high CoG

leaving on a postive note
whilst the 911 feels a bit different (probably due to drive train), the etype and mr-s feel very similar with same WB

btw, do you have a link to your gearing spreader? currently im just altering FD

back to the pits...


update: k, tried the MR-S with 54.5, and stiffening things up a bit, but still oversteering.
what i tried, from blooze suggestion was, +14% stiffer on ARB, +3% stiffer dampers, didnt help, so then move the ARBs to 50/50, and soften the rear bump, so its now nearer 58/42
that seemed to be heading in the righ direction - but still got some issues with oversteer.
think i will carry on adjusting, and back calculate once ive got it good.
(my sheet is now getting a bit more flexible, allows variance on total stiffness, and biasing the  WB on each component )

btw, found an interesting bug, which im gonna use for the photo competition, details later

[Blooze]

A couple notes:  3% stiffer on springs and dampers, not just dampers.

At any rate, you will come on the Wb that suits you.  54.5 seems to suit me.

How I arrived at 54.5.

I have 6 builds using this... this... somebody needs to help me with a word here... process.  Anyhow, some started at 56, and some at 55.  In order to make the car behave as I wanted it to I had to add shaped values to both the ARB and Springs.  As I have stated before, the dampers only get changed if the springs get changed.  Once the car was acting the way I wanted, I checked the Wb result of all three components, paying attention, really, to what happened with the ARB and Springs.  In 5 instances, the result was 54.5% or awful damned close.

So with the 6th build, I picked 54.5% from the get go, and stiffened the ARB and Springs as I am wont to equally to maintain the 54.5%, which in reality was no difference than the previous builds that started out something else and gravitated toward 54.5 via the tweakage method...

As I stated before, 54.5 works for me.  I don't know what your (the collective instance inferred here) driving habits are, more than likely different than mine.  You will most likely find a number that suits you.  And here are a few thoughts concerning that.

Our own generated Wb can be to whatever precision we care to make it.  Two decimal places affects the ARB and the Springs and has no affect on the Dampers.  But, for me, those are govened by the springs anyway so it doesn't matter what they do really.  I may make my car sheet reflect that now that I say it.  All I need to know about the Dampers is "what is the original Rebound."  Everything is calculated from the Wb from there on out.

Get the Wb and parts set up in a worksheet and watch what happens to the spring, and therefore the weight distribution as you alter the Wb.  I had a moment the other night when I was thinking I needed to get some more weight over the rear wheels.  I was preparing to add a shaped increase when it occurred to me that I could move some weight from the front to the back just by lowering the Wb.  So I watched what differnt values did to the weight distribution.  When I got done playing around, I found out the .5 reduction in the Wb moved 20 lbs from the front to the back for this particular car.  That seemed to solve the balance issues.  Now all I had to do is solve the "the damned thing is bottoming out too much" issues.  That was handled by adding 4% to the springs, and 20% to the ARB.   I dinked with that until I found the optimal value.  The only rule was "keep the Wb"  therefore, front and back got the same increase or reduction.

So, right now I have 54.5% as an Ideal Wb - FOR ME.  I am going to stick with that for a bit and see if it presents any problems.

You might as well know - here at BBB racing, we have bought in to this.  The task at hand now is to give "why not" a chance.  I am saying to Forza, "Prove me Wrong."

I take this position based on 6 ground up builds.  There is some missing case information.

• FF car - Mugen Civic on hand for that.
• AWD car - Peugeot 207 on hand for that.
• Existing ill behaved car - can it be brought under control - new Z06 is available for repair.
• Can an existing Good car be made better, or at least on a par with this system.  The VIS Integra in either B or A is available for that.

If those are successful, then I am going to consider this project closed in my mind.  I will do it this way.  New car, old car, good car, bad car - I will do it this way.

But first, I promised you all a data sheet - than is the next step.

The step after that is ...  HEY, BIG MOO!!  What tires and class and Hp you got on your 911 RS and were does it rank in your garage?

past that, I'm getting hungry - I may declare lunch...

$

[TheTechnobear]

gr8 summary,

my omission, yes, i added 3% to springs too...
interesting to note, that you keep springs and dampers in line with one another - and that you are sticking to wb
(i was unsure, i misinterpreted your  'dampening agent' and 'a slight nod to the rear')

as you say, it may just be how you prefer your cars, perhaps i am trying to dial out oversteer, that you actually like...
certainly, the 54.5 was not controllable, just i felt i couldnt get the power down as quickly as i might.

a couple of questions for you,
- initial settings, are you taking from a completely stock car? or are you taking the inital values are it has been upgraded (for springs this matters a bit)
- are you keeping bump at rebound/2

perhaps you could post one of your setups as an example?, then i could compare how it feels with something ive put together.


update: k, just tried the 911RS, with just ARB and Springs added - added yup, 54.5 + a bit of stiffening works a treat.
so i think that means i need to strip my other test cars back, and see if the 54.5 works stock, and then upgrade them back to 700.

update2: ok, now got the mr-s on a nice 54.4 setup, stripped it back, found it had a lack of rear end grip and the aero was not in line with new build, now can run it happily with min aero... i think my old setup just masked the more fundemental issues. i also found it needed alot of stiffening on the ARB (40%), and a touch more spring/dam (6%) from original d class settings.
now gonna try tame that etype

[Blooze]

Damping Agents...

There was an excellent post in a thread I started about Dampers once...  here is a chunck of it...

•   increase bump damping in front to increase rear grip during decel = liftoff/braking/corner entry
•   increase rear bump damping to increase grip at front during accel = corner exit
and decrease for opposite affect
•   increase front rebound to increase grip at front during accel = corner exit
•   increase rear rebound to increase rear grip during decel = liftoff/braking/corner entry
•   …and decrease for opposite affect.

Also, for side to side movement (cant think of right word (lateral)) such as going through a slalom or chicane…
•   increase both rebound and bump damping of front to increase transitional understeer
•   increase both rebound and bump damping of rear to increase transitional oversteer
•   …and decrease for opposite affect

I have created a little tool in my car sheet that allows me to make those sorts of bumps to my dampers.

I did a study long ago, similar to this and found that the dampers reflected the weight bias and were unaffected by the springs. I thought that strange.  However, I did realize that my changing the springs back then did mess with the Wb, therefore it would behoove me to keep my dampers somewhat in sync with the springs.  I may review this practice with this development though.

I don't reset the springs until I have bought all the parts and weight has settled down.

Yes, Bump = Rebound/2 + Agents

I'll try to get a setup posted later, maybe this weekend.  I find the further I go the behinder I get this week...

Interesting, the 54.5 seems to be working for you too...

I have attached the compiled sheets to this post - lets see how this works

The Wb values of the already built cars is interesting.  The ruse seems to work, if that is what it is.  None of us wandered far from the published Wb.  The one with the most are the ones that were setup with FDawgs calcuator...

[TheTechnobear]

this is gr8, every time i come back, i get a bit more insight into all of this - thxs

now the, first part of your quote - i already was using, i kinda learnt that from FD's calcs and then 'compiled' into my understanding by thinking about wegith transfer

but, then 2nd part, id not read before BUT had kind of guessed this must be the case, due to this WB discussion, because this is exactly what FM was doing with the stock cars - so its gr8 to hear it independant of this discussion - more fuel to the fire!   
(i assume this 'lateral' movement, is roll, i need to think about this, and reflect on how this is different from ARB, in feel ... , its something to do with the fact right/left dampers are independant, where ARB isnt - but what does that translate to in feel, and why you would stiffen ARB, over dampers)

intresting about bumps, and that you are using these to mod the feel - i was trying to keep bump in a fixed ratio, as well - which i dont think works, since as power increases, ive previously soften the rear bump abit, to get more weight over the back wheels to accelerate. if youve been modding this, then that also further explain my oversteer issue, which you werent having with your 54.5 builds.

initial values of springs -k, my thoughts are in makes little difference, except for depending on when you take the 'reading' will affect slightly the amount of stiffening you add, but given this  is not fixed (for me at least), its not an issue.


i know what you mean about getting behind, ive now got quite a few cars, with thier inards lying on the garage floor as part of the experimentation

btw, didnt see any attachment on your post.

[Blooze]

re the attachement...

I can't find the hook for it...  Have logged a bug report with managment

On the Dampers vs. ARB thing.  To me, the Dampers single purpose is to manage the speed with which the spring recovers.  The ARB are used to control lateral roll, as well as the springs.  The springs alone control motion front to rear.  That is how I view the suspension from 80000'...

As for the springs and when...  I am documenting the value and calculating it.  If I used the first value as input, then added all my parts, then calculated the new springs, I would be doing it with a number that was too big.  I guess when you read my stuff, you need to remember that I build the whole car in a spread sheet.  The only thing I do with Forza is transfer the numbers after I have figured out what they should be.