ICEngineering Subjects

Thursday, November 29, 2012

STX RX-8: 2012 Season Overview

Long absence as I don’t really have the attention span to do more than one thing at a time. I’ve been concentrating pretty hard on autocrossing this season without much time to do anything else.

Last winter, I did a bunch of work with very poor hours-of-labor to seconds-on-course ratios.
First was dropping the rear subframe to replace the bushings with UHMW polyethylene. This should reduce subframe movement which probably causes understeer-inducing toe change under load. The STX rules don’t allow metal, so acetal (delrin) or UHMW are about as good as it gets. UHMW is really cheap, and its suitability for subframe bushings is about the same as delrin so that’s what I went with. Both are ridiculously easy to machine:

The worst part of this task is definitely dealing with the subframe when all of your fasteners are rusty from having been too careless with the car in crappy conditions. I could also use a transmission jack or something a little bigger (or another person I guess):

I burned/sawed out the old bushings, pressed in the new ones and gave the subframe a good cleaning and a new coat of paint:

Bolting that back up was approximately equal in pain-in-the-ass-ness to removing it, but at least everything was clean.

Next on the list was spherical bearings at the ends of the dampers. The RX-8's dampers (like just about every other production car's) are mounted on squishy rubber bushings for good NVH. However, they do lots of twisting and pivoting around to keep from bending the damper, so I wanted to replace them with spherical bearings with no slop and less friction. While I was at it, I also modified my spring perches so that I could lower the car more. Of course I'm still using my dirt cheap Koni Yellow dampers that I've had for the last 5 years, so the sphericals cost about 1/3 of what the dampers cost. I'm still not sure what I think of that fact.

The rear shock bushings need to do a lot more twisting and bending than the fronts because of how they're mounted, so I did those first. And then the season started and I never really got around to doing the fronts. Oops. First, I made a carrier sleeve to weld into the lower shock eye that would take the spherical bearing and a retaining ring to hold it in:

You can see in that picture how I have my coilover spring perches sitting as low as they'll go, so I cut off the factory spring perch to leave a little lip and bored a step into the coilover sleeve so it could slide down lower but still be retained by that lip. I also welded in that spherical housing:

I did the same thing up front with the spring perches. However, the lower mount of the front shock has a clevis that attaches to a bushing in the control arm, so I'm unsure of the legality of replacing that with a spherical.

Up top, I lopped off the top of the shock mount and welded in another spherical housing, this time with a bolted plate to retain the bearing. I see now that I don't have pictures of's not very interesting anyway.

The last thing I had planned was a new exhaust. I knew of a local guy (Brian McNamara) running an aluminum exhaust on his FSP Civic, and I thought that might be a good fit for me because it's light and aluminum is a lot cheaper than stainless steel. I also planned to package more than one muffler, hoping that would make it quieter than my current single straight-through Borla setup (it's definitely louder). So I bought a pair of Vibrant aluminum mufflers and a bunch of bends and tubing, meanwhile convincing friend and local STX competitor Eric Shin to do the same on his WRX Wagon. We built his first because it was a heck of a lot easier:

This one weighs about 7 lbs

Mine was complicated because it needed to go through two holes in the bumper and package two mufflers. We were up pretty late getting this thing finished up:

Mine was 11 lbs

Eric's exhaust worked awesome with no signs of damage for the entire year except for a slight dent from a stray cone. Unfortunately, the fact that I don't have any heat-extracting turbocharging devices in my exhaust stream coupled with the fact that rotaries have pretty extreme exhaust temperatures to begin with meant that mine ended up cracking and falling off while autocrossing in Nebraska. That made for a long, loud drive home. I ended up reattaching the old Borla single-exit exhaust to use for the rest of the season.

Those were the winter projects. When the season finally started, the car was AWFUL! I was kept up at night during the week between events worrying about how I could possibly run a national-ish campaign with the car being so terrible. It was extremely sensitive to throttle inputs and would start sliding uncontrollably on every corner exit. I changed everything; spring rates, damping, new sway bars, ride heights, tire pressures, toe, camber...everything. But the car was suspiciously unaffected. I started looking for bind; I used a load cell to measure linearity of force to travel due to bushing compliance and to see where I contacted the bumpstops and how non-linear they were and I couldn't find anything. It was amazingly frustrating. 

Eventually, the new Hankook tires that my co-driver had ordered came in (they were on back-order) one week before we were to go to Lincoln for "Spring Nationals" and everything was fixed! In fact, it was really dumb of me to not just try new tires at some point. We didn't know that it was all better until we got to Lincoln though, so it was a crazy risk to take. The car was suddenly just incredible. I got my second ever national trophy at the Lincoln National Tour, but the greatest reward was the relief that I felt that I wasn't just unbelievably awful at putting a car together.

Following that fiasco, this was by far the best autocross season that I've had. I had a great competitive STX class to run with back at home, and I was regularly winning the class and achieving top 10 indexed results, right in the mix with some of the best drivers in the region:

Then, something totally unexpected happened. In July, I went into the Toledo Pro Solo hoping to trophy in the biggest class at the event, but somehow I managed to actually win it outright! After my winning set of runs, I got out of the car and almost fell over because I just couldn't believe it.

I went on to take 2nd in the Peru National Tour just one week later, which confirmed to me that the car was awesome and incredibly easy for me to drive fast. I was really excited for Nationals.

However, Nationals didn't go quite as well. My tires were looking almost like slicks by the time September rolled around, but anecdotal evidence about the Hankooks indicated that they are good until they cord, so I just left them. That was definitely a mistake. They had enough life to get me 3rd place in the Pro Solo Finale, though their breakaway characteristics had definitely gotten less predictable so I was sitting on one incredible left-side run and a downright terrible right-side run.

For the National Championship, the car had become very difficult to drive. It was great for the first run only, so both I and my co-driver ended up way at the back of the pack. A huge letdown for the end of a great season.

The one good thing that came out of that week in Lincoln was that my 3rd place finish in the Pro Solo Finale netted me a 2nd place overall in the season points for Pro Solo. Good for a nice trophy and a bunch of contingency money from Mazda.

Well, if that isn't just the worst photo ever...
I wrapped up the season with just a few local events, including a drive in my co-driver's new BR-Z on Hoosiers the weekend after Nationals (it's great in case you're wondering).

Overall, the season was not perfect but it was MUCH better than expected (trophies in 4 of 6 national events attended), and I learned a lot of things so I'm really looking forward to next season. I'm also looking forward to a break from racing over the winter so look for some progress on the Starlet in the coming months. I'll also be making some major improvements to the RX-8, so maybe I'll update on those things in smaller and more frequent posts.

Saturday, November 24, 2012

Civic Cat Introduction

That's a 1990 Civic DX, and a '97 Arctic Cat Thundercat 900.  By combining the two, I hope to build the first SCCA Rallycross M2 car to the extent of the rules that I know of.  I'm sure at this point some other people somewhere are working on similar projects.

At first glance, this may seem like a bad idea.  But hear me out:
Project Goals
1) Build a vehicle significantly (~1sec/40 second course) faster than current M2 competitor cars
2) Win M2 class at rallycross nationals
3) Do this for under $3000
4) Possible $2014 challenge car (but I haven't actually read those rules yet)

Target Specs:
a) 1500lbs with me sitting in it
b) 160hp, available (after drivetrain ineffeciencies) from 20-60mph with CVT
c) ... frt/rear weight distribution (Still deciding - thinking 60/40)

Current condition:

Current plan:
-9:1 reduction after CVT secondary accomplished with two differentials (sealing, durability).  
-2nd differential, between front wheels, will be limited slip
-Extensively modified subframe to support new drivetrain
-Complete stripping of Civic - no interior, dash, engine, trans, electrical, fuel tank+pump, doors, rear glass, rear hatch, bumpers, trim, wipers, hvac, functional passenger door, etc....
-Use snomobile wire harness (~3 wires, awesome), pull start, mikuni fuel pump+3 gallon cell, no-assist brakes.  Will have enough amperage to run illuminated gauges, brake light, and 2 HID's forward with snomobile generator
-13" wheels, autograss racing tires
-May require roll hoop, or bars for belts pending investigating door and stock belt construction
-Fabricated 2-stroke expansion chambers (3x)
-AN brake lines run in car, 50/50 frt/rear before rear brake bias adjuster.  Rear drums OK

I have multiple ideas for engine and CVT layouts which should package, one which mounts the engine in the passenger seat area.  All layouts will require elimination of passenger seat area at least to package the 3 large expansion pipes.  Too bad nobody will be able to ride along!

The stock car should weigh about 2000lbs.  Replacing the stock engine and trans should save over 100lbs right off the there another 500lbs to be removed? I will corner weigh the shell when fully stripped to decide on engine and trans layout.  I will plan on testing with floor-mounted ballast to consider vehicle weight vs CG advantages, and hope to learn what's fastest.  I could potentially run ballast on some events, and none in others after seeing what sort of risk there is of traction rolling.

So how heavy will it actually be?  Will a CVT respond quickly enough and will the car actually be fast?  Will I be able to spin the tires through 30mph like I hope? Have I forgotten things I should consider (like cutting brakes...)?