TopGear8

iTrader: (3)

What events do you plan on doing this year? Any National Tour's or Pro's before the Championships in September?

Modified Dave

ganseg, thanks for that. We were wondering about the tach while dyno testing it, since we noticed it was reading a good 400 rpm higher than the dyno was indicating. Looking at dyno graphs for healthy STX 8's like GeorgeH's, assuming I can make mine similarly healthy, I will definitely shift at around 8 to 8.5k rpm since there doesn't appear to be any reason to rev it higher than that. Might stretch it to 9k when the course layout requires it.

TopGear8, I'll definitely be at the Seneca Lake, NY National Tour event in July (though the car won't be fully STX maxed out by then, I don't think). I'm putting together a little posse of fellow Canucks to come down with me. We'll bring maple syrup and back bacon to pay off the tech inspectors and highway patrol :p Other than that, I'll take it to a bunch of local autocrosses and time attack events to get the 8 dialled in to my liking (and to have some fun). Might take it to the NASA weekend at BeaveRun at the end of June since I love that little track and it's not too bad a drive from where I live (close to Niagara Falls).

chiketkd

iTrader: (5)

I'm thinking of doing either the Finger lakes NT or the Peru NT. Haven't decided which one at this point. If I do attend FL, I'll be sure to say hi in grid.

Modified Dave

Would be great to meet you, chiketkd. We can paddock together for the double gray RX-8 effect

Actually, I'll see if I can some 255/40-17 RE-11s in time for this event so I can test them against the 265/35-18s like we talked about earlier in this thread. I have a buddy with some 17x9 RPF1's, so should be g2g on the wheels. Just need Bridgestone to play ball, which I think they will.

Modified Dave

Hey Chris, I'm going to be at the SoloSprint events at Toronto Motorsports Park on June 19th and 20th competing in the RX-8 in GT3. Might be there on the 18th as well for some testing and tuning.

Alrib

Dave, I'm the organizer for the Sunday SoloSprint event on behalf of TAC and HADA is the organizer for the Saturday SoloSprint event. Looking forward to seeing your 8!

Modified Dave

Thanks Alrib! What class are you running in?

Alrib

GT3, since I'll be on used Grand Am Hoosier tires.

Modified Dave

Grand Am Hoosiers? Nice! We'll have quite an interesting comparo of street tires + coilovers vs r-comps + stock suspension. Should be fun! Guess I'll have to install some fresh ignition coils to make sure the old Renesis is in tip top shape for this epic battle at TMP

timeforthrottle

I've also heard this Grand Am Hoosiers.. I think it will be a lot of fun!

ganseg

iTrader: (5)

Anything new on the suspension geometry relative to lowering? I went with only the 1" drop up front based on strong advice from here. But now I have a decision to make - my car is understeering and it seems to me lowering the front more would give me more grip. I hate raising the rear or increasing the rear sway bar, since it seems to me that is just lowering grip at the rear to make up for my problem.

I could go to zero toe in the rear, but that is hard having come from BMW which have enough give with stock busings to go to toe-out under compression. I don't want that much oversteer on a high speed track.

GeorgeH

iTrader: (2)

In my experience, your instincts are correct - drop the front a little and you should get more front grip. With the KWs, you can go more than a 1" drop without having bump-stop issues, and IMO the geometry can handle it as well. Just drop it one or two turns - you'd be surprised what that will get you.

And, I'd stay away from zero rear toe. You'll probably just end up with corner-exit oversteer.

[edit] I should add that my comments are relative to SOLO use. I've no experience setting up an RX-8 for high-speed track use. If that is your application, it is possible that going lower in the front will result in objectionable amounts of bump-steer.

Charles R. Hill

iTrader: (7)

Dave, I would suggest starting your pulls at as lower RPM (like 2,000 or so). That way, we can verify the SSV opening as well as the other valves. At 6,250 and 7,250 we can see the APV and whatever the HELL the other one is called (I can never remember, LOL) as that is where we see slight dips in torque during the transitions. I would also suggest using less smoothing on the printout so we can look at more detail. Even brand-new OEM coils will create a "picket-fence"above 7,000 RPMs, which the BHR Ignition System will cure.

Modified Dave

Thanks Charles, will revise our dyno technique as suggested and looking forward to getting rid of that picket fence!

ganseg, I haven't done a bump steer or roll center analysis yet but will do so in the next few weeks. I just installed a set of BC coilovers last night and I'm doing a string box alignment right now, prepping it for the track tomorrow. I'll let you know how the car behaves at the track along with my ride height and alignment settings, as we dial both in during testing tomorrow. I have no idea what to expect from the BC dampers both in terms of overall performance and adjustability, but only one way to find out. Given how inexpensive these coilovers are, I'll have to keep my expectations realistic. They ain't going to outperform the Motons on my racecar, of that I'm fairly certain.

MazdaManiac

iTrader: (3)

Bump-steer? Really?

Unless your RX-8 is drastically lowered (negative rate on the lower control arm), the RX-8 doesn't exhibit bump-steer.
The geometry of the front suspension is setup to negate any changes that happen in toe from compression.

Modified Dave

Good to know, thanks Jeff! My buddy has a bump steer rig, so we'll test it anyway, just so we've got some data to show off.

The general consensus among the RX8 Solo/Race guys here seems to be not to go lower than 13 1/2'' to 13 1/4'' ride height (strangely, the convention here seems to be to measure from the center of the wheel to the fender lip, though I prefer to measure from the ground to the chassis sill since those are easier to consistently measure from), but I may try running a little lower than that to see if the car exhibits any strange behaviour. Maybe the primary concern is running out of bump travel on the dampers, rather than bump steer or other geometry problems coming into play.

MazdaManiac

iTrader: (3)

The problem with measuring to the ground is you are adding the tire to the equation. 2 PSI in the tire can change your measurement by 1/4"!
Center of hub to fender is a know quantity and doesn't change with temperature/wear/pressure/etc.

ganseg

iTrader: (5)

I hope this doesn't indicate a problem - my ride height changes by 1/2 inch between times I measure it. I would notice one side of the rear of the car was lower, next time it wouldn't be. I think the front does this too.

Modified Dave

That's a good point, Jeff. I always make sure my tire pressures are the same when measuring ride height, but tread wear could certainly contribute to changes if I was monitoring ride height regularly (which I don't tend to). I just find it hard to accurately and repeatably find the center of the hub, whereas I can always find the ground Plus I'm not sure the fender is really always in the same place. My fenders are already kinda beat up.

Anyway, I'm just using ride height to establish a reasonable starting point from which to corner balance the car (after which the ride height will be a little different at each corner, obviously).

Modified Dave

Alrid, sorry I wasn't able to make it out this weekend. My pregnant wife was sick and I had to stay home to take care of her. I should be at event 5 at Mosport in a few weeks.

ganseg

iTrader: (5)

Which issue is likely to have the first article? I'll be picking it up!

Modified Dave

ganseg, first story is in the September issue and then there will be regular (more or less monthly) stories from that point on. Was planning on going to the Finger Lakes National Solo Tour event this weekend and doing an upcoming story on it, but my wife is still in rough shape so I'll be at home taking care of her. I did sneak away last Saturday for a local SoloSprint (Time Attack) event, where I was able to get some good testing in with the BC coilovers. For an inexpensive street coilover kit they stood up to track abuse pretty well but for track days stiffer springs would definitely help (I was getting onto the bump stops a fair bit). I haven't looked at the official results yet but I think I finished 2nd in class behind a well-driven and prepped S2000.

ganseg, to go back to your comment about your ride height changing, that sounds to me like maybe you're taking measurements on uneven ground, though your springs will settle a bit after being installed and over time will sag a bit. I've found that if I take ride height measurements in different spots on my smooth and level concrete garage floor the numbers will still vary, so I've put down tape so that I'm taking my measurements in the same place every time. Helps a bit with consistency.

Here are a few pics from the SoloSprint event (including one of a nicely prepped Pettit supercharged 8...not sure if the owner is a member here or not):

ganseg

iTrader: (5)

Very cool - thanks for the pics!

That red car sits higher than mine. He must come from the only drop the front 1".

I measure my car in the same spot in my garage. It only has a little slant to help water drain. There is another guy with KW3s that noticed the same issue.

Modified Dave

On the ride height measurements, have you tried bouncing each corner of the suspension before taking the measurements, to encourage the suspension to fully settle? I find if I have the e-brake on and I don't give the car a bit of a bounce on each corner, the ride heights can be a little less consistent. If you have any binding of suspension bushings or swaybar endlinks, this could also contribute to changing ride height readings.

I think the red RX-8 is running 17'' wheels and tires, so that may be tricking the eye a bit in terms of ride height/fender gap. He definitely hasn't lowered it too aggressively though, which I'm sure is a good thing given how the front double wishbone gains camber actively during roll anyway. Definitely no point in going too low with these cars. My ride height is now at 13.5 all around and I may go up a 1/4'' to see how that affects handling. But first I'm going to try stiffer springs at this ride height.

HaydonGS

iTrader: (1)

Read the tire article in Modified and 4 seconds is very impressive, It's nice to see the RX-8 finally getting some proper coverage and being modified in the proper way. Can't wait to follow the build!