Hello all. I am a few events into my 3rd year in BRR SCCA solo II. I have several questions pertaining to the set-up of my '90 DA integra. I've searched through the SCCA forum site, and I've only found a select few coming close to success in SM class, and perhaps regional FTD in FWD.

My current hardware configuration is: B20vtec, (SK2 mani, i/h/e, ctr cams), ys1 close ratio trans (open diff), wilwood 4 piston brakes, 275/45/R16 R3S04 hoosiers, 16x8 +0 offset wheels, MOMO Start race seat, 5 pt. harness, tokico HP blues, Eibach springs I believe 475 rear 275 front, battery relocated to cabin, Eibach front and rear anti-roll bars, neuspeed front strut tower bar, OEM steering rack with powersteering retained...as well as other stuff.

Alignment specs are:
-1.5 deg front camber
-1.7 deg rear camber
0 degree toe front and rear
stock caster angle plus perhaps 1/2 degree.
Tire psi press: 32 front, 30 rear
Front anti-roll bar set to its most effective position.

My success with this set-up has been less than impressive, and I've talked with a number of other FWD autocrossers but haven't really found it to be too helpful. If someone could review my set-up as a whole, and provide constructive criticisms that would be greatly appreciated. Mind you, this is not a daily driven car, and compromises have been made accordingly.

My problems are having snap oversteer on corner entry, power-on understeer mid corner upon vtec transition, and power on understeer on slow corner exits. The 275 hoosiers take a very long time to heat up, and when I finally have some heat in the tires at the last corner, I'm already crossing the timing lights.


What my revised plan of attack for this car is, is to increase the static front and rear negative camber angles to perhaps -4 degrees front and -3 degrees rear, and increase the spring rates to 300 front and 600 rear, pick-up an ITR LSD or KAAZ LSD, and replace radius rod bushings (as well as the LCA to chassis bushings) with spherical bearings and increase the caster angle, as well as bring the chassis to within 3 inches of the of the ground. Mind you these are not all cost effective solutions, and the change to LSD may be delayed.


I would also like to have some input as to the battery relocation. It was previously located behind the rear axles in the cabin, although after consulting with my Mechanical Engineering professors, the increase my moment of inertia may have detrimental effects. Currently the battery sits behind the front passenger seat, and weighs about 30 lbs or so. What is the trade off to having a lower polar moment of inertia, versus locating the C of G closer to the mid point between the front and rear tires?


I apologize for my ignorance, but how do I post pictures on the threads here on Honda-Tech? The insert image button gives me the [IMG][/IMG] brackets, and I don't want to post a weblink. (I'd like to post pictures of Hoosier tire wear so it can be discussed in conjunction with static negative camber.)


Thanks guys,

-Andrew

 

1. To post the pics, insert the link between the ['img]http://x[/img'], like the "x" (ignore the ' ' that's just to get the text to appear).

2. Tokico Blues suck. If you're having handling problems (and it sounds like you are) that's probably a good place to start throwing money.

3. With the power you're probably making (220whp or so I'm guessing), an LSD is pretty necessary. You know this, I'm just reaffirming it. You should be having power-on understeer like crazy.

4. I know there are differences, and I'm not too familiar with DAs but your spring rates sound awfully soft to me. That with those junk shocks could be a recipe for failure in itself.

5. Your alignment is just weird, and I think is another major contributing factor to your handling woes. Increase that front camber a bunch for starters. Again, you seem to know this already.

6. I don't know too much about your battery situation BUT...possible alternative:
-Lighter battery in the original location. You'll save weight (battery + weight of those heavy gauge battery lines), and will have more weight on the front. You want something like 60/40 weight distribution, not 50/50. Unless you're way front-heavy, moving it more towards the rear is not necessarily a good thing.

I don't know how much help that is, but maybe it'll be enough to give you some ideas/direction.

 

Thanks for the quick reply, the Koni yellows funding is coming along, as is the LSD funding. I've read your past posts on numerous threads Stinkycheezmonky, and they have been helpful.

My reasoning for the soft suspension is that surfaces of which the BRR SCCA holds their events are often very bumpy, and often have rubble. With stiffer springs, I'm afraid the rear of the car will become even more nervous and skittish. Also, in terms of braking, a light rear and heavier front has spun me into the weeds countless times, as I spun the car under the brakes a few weeks ago at the last event, spinning a little more than 180 degrees while negotiating a quick left-right. It appears the combination of the 275 width tires, coupled with the 12.2" wilwood 4 pot kit in front, has caused a significant change in my brake bias. Prop-valve?

From what I have gathered, operating under static friction during braking, the car will oversteer very easily, until I reach lock-up, and then the car will understeer. I would assume given the cantilevered engine over the front wheels, an increase of the normal force acting on the front tires would induce even more oversteer under the brakes.

I was thinking of going with 800 rear, and 600 front, and reducing the compliance of the rear bushings, and making more efforts to reduce the longitudinal rearward weight transfer. Although, I simply cannot justify the stiff front since a decreased front roll angle would induce more understeer on corner entry.

Or perhaps I have the front spring rate, and anti-roll all wrong? It seems like a more effective front anti-roll bar would have conflicting affects in terms of increasing oversteer or increasing understeer.

Van Valkenburgh put it, "...in FWD a big front bar has conflicting effects: it still increases understeer by overloading a front tire, but conversely it decreases understeer because the more heavily loaded tire is now driving instead of dragging" (Valkenburgh, RCEM, pg. 159).

I am assuming Valkenburgh is referring to thrust effects generated by the outside wheel, and "sucking the front" of the LSD or locked diff equiped car into the corner.

Does said front bar create a greater yaw moment when the tire is operating under static friction, and induce understeer under kinetic friction conditions?


Thanks for your help guys, and I'll try to elaborate more on my questions if they're poorly phrased.


-Andrew


Modified by PseudoScience at 12:25 PM 4/26/2008


Modified by PseudoScience at 12:27 PM 4/26/2008

 

Just curius how did you get those 275/45 wheels to fitt? Have any pictures of the fenders?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PseudoScience &raquo;</TD></TR><TR><TD CLASS="quote">I've read your past posts on numerous threads Stinkycheezmonky, and they have been helpful.
</TD></TR></TABLE>

Glad to be of help

Are you setting your sights primarily on local competition then, rather than national level stuff? If so, suiting your suspension to that lot isn't a bad idea. The shocks are still garbage one way or the other though.

For the braking issue, since you haven't said otherwise I'm going to assume you have 275s front AND rear. If that's the case and you're still having oversteer issues under braking it sounds like either a proportioning problem, or a problem with your braking technique. What's your rear setup? What pads are you running front and rear? And how are you braking? Are you braking and turning at the same time?

I think one problem you're having is getting a little too theoretical. It's good that you're considering as many angles to all this as you can, but you're doing that with a sub-optimal setup. Given that, you're going to have other issues fighting your "theory." This isn't a crack on you or anything, but what kind of driving experience do you have? Like with the correct vehicle setup, your driving ability needs to be "there" to make use of these ideas. If your ability is "there" then you should really focus on the car.

Along the same lines, you're thinking too hard about the front bar. I suggest this:
Step 1: disconnect bar, do a few runs, see how things feel.
Step 2: advance from there
Still though, there's this Valkenburgh idea. To me, that sounds applicable only to LSD-equipped cars. For your car, yes, you'll overload the front tires more. But if you're already spinning the inside wheel, more load on either tire isn't really going to help you. That's the way I see it anyway.

Unfortunately, it sounds like you have a better grasp of the technical terminology here than I do (yaw moment, for example). Nate (solo-x) or a few others can probably answer those questions much better than I can.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PseudoScience &raquo;</TD></TR><TR><TD CLASS="quote">
I was thinking of going with 800 rear, and 600 front, and reducing the compliance of the rear bushings, and making more efforts to reduce the longitudinal rearward weight transfer. Although, I simply cannot justify the stiff front since a decreased front roll angle would induce more understeer on corner entry.</TD></TR></TABLE>

I don't know that you're thinking about that correctly. At least in my experience, that hasn't been the case (although I think I understand the concept you're considering there). Consider the change in front to rear ratio rather than just an increase in front stiffness.

 

im new to this aswell but from what i have seen in autox the suspension setup is the most important part. so i would suggest upgrading to better shocks and maybe stiffer springs. though i have the eibach springs too i am hoping with better shocks the eibachs will work on the da.

 

Thanks for the replies guys! This is really appreciated. In terms of my driving ability, I still have alot of room to improve. At the same time, if I focus, I can transition the lateral and longitudinal weight pretty smoothly, while being close to the point where the tires will operate under kinetic friction, and on my best days I've beaten 66 out of 100 cars overall, pulling better times than supercharged M3's, porsche boxsters, subaru sti's, which were on R-comps, and I was on street street tires. My best day was 4th out of 11 in SM class. Although whichever way I look at it there are still countless areas for me to improve, as well as for my co-driver to improve. (Perhaps in the 2009 year my co-driver and I would have learned the car well-enough, and be on warm tires, that we may have a chance at doing well.)

I agree completely with the Tokico shocks being garbage. I have no counterpoint here. I perhaps am thinking too hard about the front anti-roll bar, and I have a tendancy to really look too far into something, that I lose track of the bigger picture--and this is where you guys come in!

And yes Stinkycheezmonky, I am trying to optimize a sub-optimal car set-up with a less than ideal budget. If it was truely optimal, I would be autocrossing the BAR Honda F1 car. I think what I am asking is how can I further tune the car in an effective manner so I can be more competetive? And doing so, how can I make changes which have the best cost to performance ratio? And yes, I do mean 275's front and rear. In regards to the prop-valve, how do you propose I go about tuning it, with a considerably front heavy set-up, given I can lift the rear up pretty easily already? Perhaps bias more to the rear, so I can have a rear that will work more, before the front brakes begin to lift the rear? BTW, I am running Hawk HPS rear pads, with Wilwood street type compound in the front.

I believe I have an understanding of wheel rates, and how spring rates do not coincide directly proportionally to wheel rates. Please correct me if I am mistaken, as I believe wheel rates to be a mechanical leverage which acts on the spring. Again quoting Valkenburghe, "the force ratio between the tire and the spring is the inverse of the displacement ratio. Say for example, that when the wheel is deflected 2 inches, the spring deflects 1 inch. The displacement ratio between the spring and wheel is 1:2 and the force ratio is 2:1. [note] the spring rate in pounds per inch will be four times the wheel rate, since both force and displacement change by a factor of two" (Valkenburghe, RCEM pg. 33).

I am assume here, that we are truely interested in the force of which the tire exerts on the ground at some given wheel displacement, given that a 500 lb spring will not extert the same force on the ground, if the spring is located 7" from the tire center, or if the spring is located 14" from the tire's center.


Also, stinkycheesemonkey, can you explain what you mean by "front to rear ratio?"

Overall, from what I've gathered I need:
-more seat time (I think I'm already doing this.)
-more negative camber
-LSD
-Koni shocks (i.e., more dampening)
-stiffer springs


I suppose this is why they have nicknamed this SCCA class "$M."
-------------------------------------------
Here are links to pics of the car:
http://www.g2ic.com/forums/sho...age=2

The car is the black DA after you scroll 1/2 way down the page. The car looks like a monster truck.
---------------------------------------------
I was able to get the 275's to fit by cutting the fenders and grinding down the lower rear sections of the front wheel wells, and using 16x8 +0 offset wheels.

Believe it or not, the day the picture was taken, it was 40 degrees out, and the car spun right through 1st and 2nd gear, because the tires were ICE cold. I'm praying for warmer days in the future.

I would like to first succeed to some degree in my regional area, and atleast try to come close to FTD in one of the events, and perhaps attempt to win SM overall next year. (This most likely won't happen this year, since I'm still sorting out the car.)


Thanks alot guys for your input, as I'm looking for assistance, and ideas.

 

I can completely understand a budget car, as I'm on a pretty tight budget myself. Only problems with that in your case are that you want to be competitive and in a more expensive class. That whole, "Racing costs money, how fast do you want to go?" thing is very appropriate for this. That being said, let's analyze some things here:

-You have the right tires, but not the right suspension or alignment. You can't maximize the potential of these tires without those two things being at least "ok". Right now they're "no good." Shocks are on your list, good. How about alignment? I'm guessing you can't lower the car more than it already is without the fender cutting into the tire, right? Maybe consider some cheapish adjustable camber arms, Skunk2s or something (something that will allow a decent amount of adjustment, since your ride height is limited). You might also want to consider changing toe front or rear to try and help with some of that too. Your zero rear toe sounds like (from some other reading) that it'll make the car a little oversteery. Maybe consider a little toe-in, as the back end will toe-out when it gets light under braking. Might help that entry stability a little. Overall, this whole paragraph is speaking more to how competitive the car can be, rather than addressing specific problems (sort of).

-Your brakes sound ok. That's a good thing, because it means you're probably not locking the rears up before the fronts. I'd look at alignment for this again. In addition, to my knowledge proportioning valves (the adjustable variety) work only to DECREASE rear braking. Its been a long time since I read up on them though, so I might be wrong.

Spring rates are directly involved with wheel rate, but not with motion ratio.
WR (wheel rate) = SR (spring rate) * MR (motion ratio)^2 (squared).
I'm not super experienced with understanding the numbers behind these measurements, but I do understand that its a more accurate portrayal of how the thing is going to behave in comparison to other vehicles. Since I'm unfamiliar with the DA stuff, I'm trying to get an idea of how it compares to DC Integras and EG Civics.

When I say front to rear ratio, I'm talking about the difference in magnitude between front and rear wheel rates (my own terminology, because I don't know a proper way of describing it). For example, DC5 Integra/RSX might have 1000lb/1300lb springs front/rear. That winds up being a front-biased setup despite the higher rear spring rate because of the suspension design and resulting wheel rates. DCs/EGs are different, where that would be a rear-biased setup. For YOUR situation, let's just briefly assume your motion ratios are about the same as for a DC Integra. That would mean you're starting with a front-biased setup (higher wheel rate in the front), with plans to change to a rear-biased setup.

All that explained, you're talking about "decreased front roll angle inducing more oversteer", when you're going to have all sorts of other changed behaviors just from the change in front to rear bias. I think that would make a bigger, more noticeable difference in how the car behaves than any change in roll angle. Again, that's going solely off my own experience. I do know that on a roadracing car, higher rear rates like that do NOT have any noticeable increased understeer for any reason.

Your conclusions seem pretty spot-on for right now, with an optional addition of general alignment changes (toe something or other).

 

Holy F'in tire. You have to be a member to see those pics btw.

But IMO, there is a balance between suspension and tire size. Just having a huge tire will only require more suspension, or else your not really using it to it's full potential.

Have you done any slolom or skid pad testing? I'd highly reccomend it to get the setup fully dialed in.

 

Thanks for the help with sorting out my suspension stinkycheesemonkey. Although I don't think I completely understand the motion ratios. Can you further explain this? I'm understanding this as in, since there is a greater vertical displacement of the front wheel in respect to the rear wheel during lateral accelerations, therefore the car has a greater front motion ratio, despite the lower front spring rate. Is this an accurate understanding?

BTW, I said, decreasing the front roll angle will increase oversteer, when I meant to say understeer. So, I'm sorry for any confusion. I agree with the point that stiffer rear springs does not increase understeer in any form, although I would say it would give the car better initial turn in, and lift throttle oversteer.


Also, when you say the, "difference in magnitude between front and rear wheel rates," what exactly does this mean? In regards to magnitude, do you mean absolute values of the front vertical wheel displacement, minus the rears' value?

In regards to the toe, I think I'll start with 1/16 toe out in the front, and zero rear. In terms of making "use" of the wider tires, I don't believe there is a such thing as having too much tire, although there is such a thing as too much rotational mass, which is obviously detrimental.

Thanks for your help guys! I'll take all of these ideas into consideration within reason.


Modified by PseudoScience at 7:47 PM 4/27/2008

 

your car doesnt seem to be sorted out to well, you dont have a very good susp setup, and youv got these huge tires and super low offset rims, i mean why do you have 275 wide tires on a car like that

can i ask your reasoning behind these?

these seem like there hindering you, and hiding/covering up some bad driving, you should have a better susp setup, with alot smaller rims/tires

15x8 +30ish with like 225/50's whould be better

 

the absolute first thing you need to do is get better tires!
You're running 275/45-16's with a diameter of 25.6" - you should probably run a staggered 275/35-15 front and 225/45-15 rear (or all around) with ~23" diameter. and you want the new A6 compound, not the 4 year old road-race RS304 compound.
you'll need a pretty stiff suspension to handle that much grip as well.

 

http://e46m3performance.com/tech/wheel_rate/

That's for a BMW, but the theory and math can be applied to anything. He can say it better than I can, I think. If that's still giving you trouble just let me know and I'll dig out my Fred Puhn book You have the basic idea down though, yes.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PseudoScience &raquo;</TD></TR><TR><TD CLASS="quote">I agree with the point that stiffer rear springs does not increase understeer in any form, although I would say it would give the car better initial turn in, and lift throttle oversteer.</TD></TR></TABLE>

You're correct. When I said it wouldn't increase understeer, that's a good thing I'm curious too, you say you're oversteering under braking and at the beginning of a corner. Are you lift throttle oversteering? That would be completely independent from any suspension issues. I'm guessing no, but just thought I'd clear that from contention.

The difference in magnitude, yes, you have it correct. Again, it's just another way to look at things. If you ignore all that jazz and just look at spring rates, a heavier front spring would seem to be a front-biased car, right?

Try that toe adjustment, I'm interested in the results. Turn-in will be good, as long as the ***-end can stay where it needs to be.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 01-0720 &raquo;</TD></TR><TR><TD CLASS="quote">i mean why do you have 275 wide tires on a car like that
</TD></TR></TABLE>

Because if you want to win SM in a FWD, you need a 275. Look at the other top-running FWD cars, they also have 275s. A number of these guys have done front-to-back testing between them and the 225s and found time.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 01-0720 &raquo;</TD></TR><TR><TD CLASS="quote">15x8 +30ish with like 225/50's whould be better</TD></TR></TABLE>

Again, for SM there are better options than this. That's all fine and good on a street car, but we're not talking about a street car.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tronic &raquo;</TD></TR><TR><TD CLASS="quote">the absolute first thing you need to do is get better tires!
You're running 275/45-16's with a diameter of 25.6" - you should probably run a staggered 275/35-15 front and 225/45-15 rear (or all around) with ~23" diameter. and you want the new A6 compound, not the 4 year old road-race RS304 compound.</TD></TR></TABLE>

This is legitimate, but it will only be making him slower, not creating handling problems. Also, he said he's running A4s, not R3S04s. They were still being manufactured as recently as early last year I think.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PseudoScience &raquo;</TD></TR><TR><TD CLASS="quote">


In regards to the prop-valve, how do you propose I go about tuning it, with a considerably front heavy set-up, given I can lift the rear up pretty easily already? Perhaps bias more to the rear, so I can have a rear that will work more, before the front brakes begin to lift the rear? BTW, I am running Hawk HPS rear pads, with Wilwood street type compound in the front.

I believe I have an understanding of wheel rates, and how spring rates do not coincide directly proportionally to wheel rates. Please correct me if I am mistaken, as I believe wheel rates to be a mechanical leverage which acts on the spring. Again quoting Valkenburghe, "the force ratio between the tire and the spring is the inverse of the displacement ratio. Say for example, that when the wheel is deflected 2 inches, the spring deflects 1 inch. The displacement ratio between the spring and wheel is 1:2 and the force ratio is 2:1. [note] the spring rate in pounds per inch will be four times the wheel rate, since both force and displacement change by a factor of two" (Valkenburghe, RCEM pg. 33).


</TD></TR></TABLE>

Regarding brake bias: You might want to search what others have suggested, but I would think that in general, the more grip you have, the more you want to bias the brakes towards the front. That's because the more grip you have, the more weight shift you create, which means the lighter the rear wheels get. If you have entry oversteer due to trail braking, you might have too much rear brake bias.

Also, never mind about that wheel rate and "front vs rear bias" stuff. It's kind of relative, so just think in terms of needing stiffer or softer rear springs. But before you go around changing spring rates, you first need to ask:
Is the damping set properly?
Am I lifting the rear wheel just a little or a lot?
Am I bottoming out the suspension and hitting a bump stop?

As for battery location, I would think that as far to the rear as possible would be good. First, this improves weight distribution. Second, it increases polar moment, as you say, which makes the car spin out slower. The benefit of having it behind the passenger seat is that you can place it lower. Mine is located inside the spare tire well.

As for camber, you might want to get an infrared temperature gun to measure tire temperature before you tweak the camber too much. Too much front camber can give you entry oversteer and exit understeer.

Read this web page

http://farnorthracing.com/autocross_secrets.html

 

Great stuff guys! Very much appreciated. I will try to clarify cars' behavior under braking. At about 30% braking the car is pretty neutral. At 60% or so, the car is seems more eager to turn. 90% the back is quite sensitive to steering inputs, and trail braking at this point has often turned the car 180 degrees. 99-100%, the car locks and understeers. Obviously I often try to finish the major braking before the turn, and in the turn, I try to gradually transition off of the brakes (while dragging the brakes, and keeping the chassis set), and feed in more steering angle.


The tire temperature issue was what I wanted to discuss next. I don't remember the particular values, but I recall higher temperatures on the tread closer towards the edge sidewall, and from looking at the tread, its obvious the outside has been doing most of the work. From the pictures taken of the car during hard cornering, the LCA bushing deflections appear to be causing positive camber. (So, I think atleast -3 deg is a good start.) Mind you, I don't have dynamic camber angle data acquisition instruments, as I would have to gather this data indirectly from tire wear and lateral temp readings across the tread, and event pictures.


Thanks for the farnorth link. I already read his articles. Caroll Smith would be flattered at the format if he was alive. By the way, does anyone know where I can find Front Wheel Drive race car dynamics literature? There are miles of web page blogs all over the internet, but so far, I have not found anything quite as substantial as Caroll Smiths' Tune to Win, Engineer to Win, Drive to Win books, or Valkenburgh's books--all of which deal more with RWD applications. I've got these books, as well as Ancas, Kojima, and few others, but nothing as indepth as Smith which deals with FWD race car applications.


As for the tire sizing, I would agree the overall diameter is a bit tall. Although when I was autocrossing on 225/45-16 tires, I would find myself right on the redline at second gear during the fast sections of the courses, and wished for a taller 2nd. The '92-'93 GSR YS1 cable transmission final drive, and gear ratios I found to be a bit too short. Shifting to 3rd gear will be a waste of time on the course, while 2nd gear is already puts the engine at redline. Nevertheless, my future plan might be to sell the 12.2" 4 piston Wilwood kit, and put on civic brakes with Cobalt friction spec-B pads, and oem civic rotors, and run 13x10 diamond steel wheels, and 11 or 12 inch wide Hoosiers. You may think my braking would deteriorate, and it would slightly. But has anyone here ever TRIED the cobalt friction spec-B pads? They are absolutly astonishing! (I think they're still making these.) (Although, mind you, they are only good for about two months or so, cost $150 for just the front pads, and they will create a deep lip and groove in the rotors, and eat rotors very quickly, and make tons of brake dust and fumes, and noise.)


In regards to the battery relocation, Stinkycheesemonkey, would you care to explain your reasons for locating it in the engine bay? I've been thinking about this in terms of front and rear, and mid locations pro's and cons:

Front battery location:
Pro:
*decreased polar moment
*quicker transitions whilst changing directions
*Greater normal force acting on drive wheels (i.e., better acceleration)

Con:
-center of gravity placed further forward
-rear tires are under utilized
-less absolute lateral acceleration
-more front weight causes more understeer

Rear Battery location:
Pro:
*center of gravity placed closer to the midpoint between the front and rear tires
*more absolute lateral acceleration
*improved braking, since rear tires can now do more work

Con:
-Increased polar moment of intertia
-increased sprung mass due to relocation kit
-less normal force acting on drive wheels


Mid battery location:
Still causes front bias, although perhaps strikes a middle ground in terms of the behaviors is creates from its' positioning.


I could be off on some these conclusions, and if you feel I am mistaken, explain why. It appears to me, there does not seem to be an ideal location under all circumstances, but rather, ideally the battery should be changing positions in the car when cornering, braking and accelerating!



Modified by PseudoScience at 9:22 AM 4/28/2008

 

Yep, outside tire wear and higher temps = needs more camber.

Unfortunately, I don't know of any good FWD-specific chassis books. I guess because FWD is considered inferior in the grand scheme of vehicles, not many people have really bothered to waste time and money getting stuff published. I'd look to the higher levels of FWD racing (SWC for starters) for good examples.

I wondered about the gearing/sizing thing. What are you redlining at?

I don't believe Cobalt makes the Spec B's anymore. They do have a number of other good pads though. I'd imagine their current GT-Sports would be good for autoxing, as they have great initial bite and relatively low warmup temps.

For the battery stuff, you make good points all around. My view is based on a bunch of stuff I read years ago, and it was all material that I didn't experiment with to discover on my own. That information covered this:
-Battery relocation involves decent lengths of heavy gauge cable, adding overall weight.
-A FWD car WANTS a 60/40 weight distribution, regardless of anything else. A great front distribution will put too much load on the front tires, and a greater rear distribution will make the thing handle like poop. That's all based on a few simulations and at least one real-world test of a 50/50 FWD vehicle, which wound up being a devil to drive. Knowing what we do about FWD dynamics, it does make sense. Without enough weight on the front tires, the car has all kinds of problems.
-CoG, sure. But you can create a positive effect on that just by replacing the original battery with a lighter dry-cell one. It won't be quite the same, but I can't imagine it's anything more that you could actually "feel".

IMO, the rear tires on a FWD car aren't doing much anyway, so I'm not going to focus on utilizing them too much. I want them there enough to keep the car under control, but that's about it. That's my opinion, yours may vary.

The best compromise to me is a dry-cell in the stock location. It gives the desired distribution, minimizes overall weight for that particular system, and reduces wiring complexity compared to relocation.

 

for the battery you can try running a small odyssey mounted to the frame rail to distribute the weight lower up front if it matters

 

Say...in the DAs is the battery way in the front of the engine bay? I'm used to DCs and EGs where it's back against the firewall, but now I'm trying to remember my old DA's bay... That would make a little difference in some of the stuff I said.

 

There is room to mount a small 16 lb odessy battery on the low, and ontop of the front crossmember, at about the same height as the transmission.

 

As someone already mentioned the R3S04 is not the right tire for autocross. That tire is a road race tire, and needs some time to reach operating temperature. That issue is exacerbated by cold ambient temperatures. You should consider the Hoosier A6. This tire is designed specifically for autocross, and though will also suffer some from cold ambients, will perform much much better in all situations.

If you're stuck with 16" wheels because of your brakes, you'll still gain substantial performance by switching to the 245/45-16 A6 tire. If you can make the switch to 15" wheels, since your car is already "clearanced" for the wide 275 tire, go with the 275/35-15 A6 tire. You'll be back to the issues of the short gearing in your YS1 tranny, but the gains from the better stick of the tires will far outweigh the need for a shift to 3rd gear.

Your spring rates in the front are too soft. Your corner entry oversteer is likely being caused by your trail braking, and the mid corner understeer is either a result of the soft spring rate loading up the front bar, or the bottoming of the front suspension from the cornering loading leading to the infinite spring rate that results, or possibly by the attempted application of too much power.

Have a look around here for info on AutoX suspension setups. There is tons of it, and most of it involves much higher spring rates, both front and rear, as well as large stiff rear sway bars with little to no front bar. Also, your shocks are holding you back. Those shocks are pretty limited in the spring rates that they will support. I think you're pretty close to the limit as you stand and you have no options for adjusting the damping rates.


Modified by Jaker at 3:31 AM 4/29/2008

 

you have to be a member to see the pics. can you get the link from the actual pic and post it here?

 

Wow. I've never seen someone over-analyze such little issues so much, then completely miss such larger ones. No offense to the OP, but to put so much thought into such a minor thing as battery placement only to completely miss the tire situation tells me that you need to start back at ground zero and look at what will improve times the best.

As was said, these are the key points:

1) Get on autox specific compound tires. Also, get on tires that aren't so tall.

2) Buy real shocks (Koni Yellows).

3) Revise your springrates to something that's proven to work.

And I'd bet money that your spinning problem is a combination of lack of heat in the rear tire, driving style and crappy shocks/alignment settings. Don't start messing with anything else until you correct the top 3 items posted.

Also, as was again suggested, you don't need such huge brakes for an autox car. This only forces you to run a large diameter wheel, which will limit your tire choices.

 

Thanks for the replies guys. The tires I do have are the R3S04's, and the temperature issue was what I was afraid of. I suppose I didn't know it would be this bad. (Maybe on a hot 107 degree Virginia day after the 7th run on a long autoX course, they may hook-up?) Nevertheless, I will look into the A6.
My plan with the shocks are already underway, as in Koni Yellow DC front shocks, (I've already picked up DC front shock forks), Koni Yellow EF civic rear shocks and perhaps 600 lbs front, 800 lbs rear springs.

In terms of the wheels and tires, it appears the guys doing very well are running 13" wheels on A6's in the 10" to 11" widths. What do you guys think about 13x10 or 13x9 wheels, and converting the front brakes to use civic calipers? (Unless Wilwood/fastbrakes makes a caliper bracket and small rotor that would fit under a 13" wheel.)
If I go this route, I suppose I'll just need to practice shifting front 2nd to 3rd gear quicker.

 

I have a Civic with an Integra brake swap and I test fitted a test of 13 Panasport C8. They were from a Miata so the centerbore didn't fit on the rear for some reason but the wheels fit fine over the front brakes. My bleeder screw was just touching the wheel weight but that's a fairly easy problem to correct.

 

94-01 Integra brakes (all except ITR)...you can fit certain 13" wheels over them.

But why add the weight of braking components (when you don't need to) for an autox only car??? You only need good pads and a tight system, because you are, at most, coming to a stop from 60-70MPH, not 130. And only in a span of ~60 seconds at a time.