RX-8 rear stability at track events
 

Ran a track event this past weekend at Hallett, Ok in the DD 8. The car is mildly modified, stock shocks, Eibach springs, MazdaSpeed swaybars front and rear, Azenis on stock wheels (38# hot pressure), Carbotech pads (8's and 10's), MS intake, RB race pipe, HKS single side exhaust and custom tune. The rear end is very light at corner entry and and has very low grip. It tried to come around on me a few times but I was able to save it. Any advice on adjustments I could make for some more rear grip at corner entry? This shows up after straightline braking and as I'm beginning my turn in. I'm thinking some more camber (didn't have time for an alignment) but don't know what else to try, less rear bar maybe?

Also, had fuel starvation in extended high g LH turns anytime the tank was about 3 gallons from FULL. Any CONFIRMED reports that the 2009 pump is solving this?

Thanks,
Michael

i dont know of any confirmed reports on the 09 pump. but there are confirmed reports on this walbro pump:

http://blackhaloracing.com/products-...ce-fuel-pump9/

Advice from the new guy.
 

If I understand, suspension is stock except for sways and springs.

If I compare what you are looking at to my whopping 2 track events, I can tell you I have not seen this. There are better folks out there, and I am not familiar with that track, but I can turn right at 80 MPH into turn 1 at Roebling, and the car behaves well, it rolls like a son of a bitch, but stays planted. I have the G-Force Plus tires at about 34 cold, 38/39 hot. I also, due to the stock, and old (70,000 miles) shocks, need to give the rear a chance to settle before the turn. If I did not do that, I would expect a very light rear end to try to pass the front end on the outside of the turn.

Best I got right now.

Mike

Do you know where your alignment is at since you lowered the car? I don't know what has to be taken apart to lower the car, but it may have been reassembled with rear toe out. This could give you a handful on the track.

Lowering tends to add camber, so you may actually have a little too much if you were more aggressive before lowering.

Another possibility is the factory shocks. They may not be able to dampen the higher spring rate properly, and have worn out. Depending on how you're turning it, you may be compressing the outside rear all the way. When you get to the bumpstop - wham, spring rate goes essentially to the moon, and that could be causing your looseness.

Three possibilities I can think of, I would put money on the first or third before too much camber.

It was doing the same to me on cold tires, I've never had that problem until I added the set of sway bars, I have a hotchkis set, front on the stiffest setting, rear on the middle, I was considering switching back putting the front on the middle setting and the rear on the softest.
I'm not ruling out my driving technique (or lack there of), maybe I should have been on the brakes sooner and let off smoother before turning in.
Oddly I didn't have this problem once the tires were warmed up, and it only happens when I come down a straight, hit the brakes hard for a sharp turn, the backend always got a little light, but it's never tried to come around on my until the sways.

mines been pretty stable around the 90mph sweepers at buttonwillow. Im on tein s-tech and koni yellows, and potenza re-01r tires at 35#s, i would also like to add that im not using any front lips or rear wings. Once the car is settled into the turn it stays true to the line.

I think an alignment will really help in your case since dropping the car probably has messed up the geometry. When i got my first initial alignment after the spring/shocks one of my rear corners had postive camber lol

a) you're on factory shocks

b) the OE fuel pump is likely fubar, sometime they come this way new even

c) some rear toe-in and rear camber may help, but until you get some decent shocks you'll be chasing your tail in circles. Some more front bar might help too.


....

I've done five or six track days in my MY09. The only time I've hit fuel starvation is when I got below a quarter tank of fuel.

Thanks for the help so far. The Koni's arrived today. We'll see what that does. Toe plates should arrive later this week and after that I can do a real alignment. THe fuel cut is really hurting the lap times though. The car has about 35k miles (2005 model). Maybe I'll swap for the '09 model and report back afterwards.

Be careful with the toe plates. You have to start with a square alignment and adjust both sides equaly otherwise the chassis will crab. It can be done though, just takes care and determination. :)

And so not worth it ;)

Nothing is easier than a nice 4 wheel laser alignment rack :)

WTF does that mean? The experts on here are so vague its stupid sometimes.
Sounds impressive tho. LMAO

He's at Hallett having fun, not a comp racer like you.

Which Hallett event were you at?

We have a thread for that ya know?? ;)

https://www.rx8club.com/gulf-rx-8-forum-32/2010-hallett-motor-racing-circuit-high-speed-touring-193524/

PS -- i've had fuel starvation before but not at Hallett. I wonder what you're doing differently?

um, it means that if you're not careful, you can end up with the total toe you want but it might be uneven side-to-side...that will result in the car basically crabbing sideways. what is so hard to figure out? :dunno: maybe spend less time making snarky comments and more time thinking.

My car doesn't lose it in the corners Mr Snarky. hehe
Guess what I should say is , so many over spring, under shock,over sway bar, to much stagger on wheels and tires, no realignment, not enuff brakes, then wonder why it doesn't handle as well as it did stock with good tires.
A definitive thread on how to set up a good suspension for full race, HPT, Autocross would be very beneificial to all. Instead of comments that have no bearing except to the class they are racing. My apologies if that, was unintended. Then there is the power upgrades to go with it. WHEW

One last item, How many RX8 buyers are young, have driven Mustangs and Trucks and never knew ya had to align the rear wheels too? :)

Who exactly is having the problem here, you or the OP?
Secondly, if you want help, you had better be kinder to those that reply.

WOW...;)

Typical

So vague it's stupid or so stupid that it seems vague? You decide ..... :lol:

I have a set of laser toe plates. Pretty amazing to have adjusted toe numerous times then eventually put it on the rack for a double check to find out the car is within 1/16" of a perfect alignment. The key is to measure total toe, adjust one side only and get it where you want it (1/2 delta), then adjust the other side to match. It may take several attemps of adjusting, settling the car, and remeasuring.

To reduce oversteer, less rear bar. I run the MS front bar and the stock rear bar with new holes drilled 3/4" inboard of the original holes. This is assuming you have a proper rear alignment which means just a bit of toe-in and just a smidgen more camber than the front. (-2.0 F, -2.1 R for me.)

I have factory shocks with MS springs and PT sways and I didn't experience any rear end looseness during the track day I just did on friday.

though I did have an alignment done a few weeks ago.

I ran Hallett this past Sunday.

I'll be working on the alignment and will post some updates after the next event.

I would suggest using the stock rear sway bar and I have had a lot of luck with the 09 pump upgrade.

On the subject of toe plates and issue of crabbing, I just use a string from rears out to front to avoid crabbing. I tied a loop in my string to hook on the rear muffler tip. Don't laugh! really works. Hook the string around muffler tip; pull across rear tire up to front. holding string taut at the front tire, move inward until string touches front of rear tire and check where you are relative to front tire. Of course you want to be even both sides.
Sounds cheesy but its faster and cheaper than running to a laser shop everytime you tweak something. Did this for years in rally. Start with a rack alignment, then can try some things this way.
(OK so I'm cheap! Also too many idiots running the laser racks.... rather do it m'self ... more fun too.)

love it!!! My kinda guy!
OD

Are your sway bars adjustable? Less rear bar or more front if they are. When I was playing around with the adjustments on my Progress sway bars I felt what you described when I reduced the front bar and increased the rear. Reducing the front to the softest and the rear stiff gave me your problem. I ended up with the front on the middle of 3 positions and the rear on the stiff. The car is well controlled now.

How much negative camber do you have in the front and rear?

this is how I am set up currently, front on middle and rear on stiffy hole.

I'm new to RX-8's (just took mine on its maiden track voyage last week) but I've been racing for over 20 years and have worked as a driving instructor at a number of different schools up here in Canada. To me the problem sounds like a combination of setup (I like the suggestion of a softer rear bar since it's very easy to disconnect the rear bar to test its impact on handling balance) and driving.

Based on your description of your driving technique coming into a corner, it sounds to me like you're unintentionally doing something called trail braking, where you continue to apply some brakes during the initial turn-in. This will always induce oversteer (or reduce understeer, so can be a very effective technique if you have an understeering car). To avoid this, try to get your braking done a bit earlier and make sure you're back on the gas at turn-in, with the objective of being at wide open throttle no later than the apex of the turn. This "slow in, fast out" approach is usually quickest and is always safest. Once you get the car's setup sorted out a bit better, then maybe start to play around with a bit of intentional trail braking to see how it changes the car's attitude on turn-in. You can also use a bit of throttle modulation or "drop throttle" technique to transfer a bit of weight forward in order to reduce understeer or induce oversteer.

Anyway, I've often seen newcomers to the track chase apparent setup problems when the real problem is actually driving technique. Perhaps you can have an instructor or experienced racer jump in the car with you and check to see if you're inadvertently inducing the oversteer with trail braking. Easy fix if that's the case.

Good luck and have fun!

ROFLMAO
At least that got someones attention and ye had some decent feedback

Thanks for the replies (at least some of them). I think I may be trailbraking too much into the corner as someone suggested. I'm bad to try and late brake every corner and that may be where the problem is. My other racecar is a front wheel drive so I do usually use trailbraking to get it set up for some of the corners so that it rotates. Shocks and alignement is still to come, I know these steps will only help.

That's an easy habit to adopt I think. Picture any corner...the typical tendency is to brake hard and maybe really late going into a corner, feather (and perhaps trailbrake) as the apex approaches or just feather and wait for the apex to pass and then... back on the gas. I't certainly feels safe waiting that way.

I find a much more efficient path is to brake hard stright line a bit earlier, perhaps a bit of trailbrake (esp. if the straight curves in and doesn't lead directly to the apex)....but.... then be immediately ready and (possibly feed in the throttle even before the apex if the track layout makes it practical to do so), be sure to get back on the throttle hard just before or at the very latest, at the apex. I find it an easy way to pick up time others leave on the table being more cautious and waiting until after apex to accelerate. More importantly, some valueable speed can be added to your car coming out of corner if you're heading into a straight. And that's where it counts, both for the straight speed to come, and to get the weight back to the rear wheels by accelerating early.

As to having you ass end coming around, that's certainly a trait of the stock suspension. Once you get your shocks, I'd try softening the rear sways, giving you more rear grip, maybe adjust rear tire pressure too (typically a bit higher for more grip). Do it slowly and check for result.

Personally, in my car, I found the addition of AutoExe 4pt strut braces front and rear helped the issue of tail-happiness along with a bit of lowering thru coilovers. My feeling is that the rear is a bit of a compromise design, causing Mazda to have put the stock strut brace in (behind the rear seats is a metal brace). While adequate for street use, a back end that is held even more tightly by the use of the a substantial 4pt brace, is much more stable under track stress.

Ok, I have the gist of how to build this string alingment dude. Someone please expound on HOW you set it up each time. I am assuming you take measurements off of the string to the front and back of each rim. How do you get the drop arms that the strings are attached to in the right place each time so that you know you're square? Does that make sense?

I guess I'm lucky...I have a buddy that has an alignment shop with three laser racks......

It's all parallel lines. First step is to adjust the height of the strings to go through the centerline of the wheel.

The strings have to be the exact with apart front and back. Usually the cross bars are grooved identically to make this part easy.

Then you shift the bars L&R and measure to the wheel centers to square the strings to the car. Note track may be different F&R.

Then, just as you suspected, you measure the distance from the string to the front and rear of the wheel rim, than take the difference.

For best results, put your equivalent weight in ballast in the drivers seat, and rock the car back and forth a few times after each adjustment.

NASCAR setup guys still use this method and swear it is more accurate than lasers.

I am glad to hear someone say this because I have had two stock RX-8s and both were tail happy. It was not trail braking because I would have it in the last half of the corner too. I think it related to speed; my examples were at higher speed about 60. May also be related to Torsen, but i know my M3 limited slip didn't lead to oversteer this easily and that car had more torque.

I have now added coilovers where the front springs increased in stiffness more than the rears. Now the rear is more planted. That works for higher speed corners, but is not as fun on the street or as effective in autocross. I haven't added aftermarket sway bars and think I have plenty to play with before i would. I can change hieght, camber, toe, dampening, tire pressures.

increase front stiffness should definately help, im kind of reluctant to play with sway bars also, since it seems sways will dramatically affect my overall setup, which i feel pretty comfortable with right now. My other plan is to add some aero for highspeed stability, a decent sized rear wing and a front splitter should help with highspeed sweepers also

^ Don't be afraid of adding some extra sway bar stiffness...it's probably the cheapest easiest mod you can do to the car ... but beyond that it has immediate and very noticeable positive effects on handling. I'd go for adjustables, because you can actually tune your car to your own style, but regardless...

Remember more front bar gives a more planted rear - more front bar keeps your ass end from jacking up due to the lessening of body lean in corners - keeping better tire to road contact, increasing rear stickiness. There's virtually nothing bad more sway stiffness can do to your stock car's handling on track.

Hi. Apart from the correct camber and toe-in in the back, nothing can give you more information on what is happening with your suspension than taking the tire temperatures and air pressure after every heat you run. Invest in a good pyrometer and preassure gauge and that should help you decide your next step. It also can help someone with more experience help you in what adjustments you shoul try.

Good luck.

those are the problems.