Two 1990 Miatas - STS Autocross, CSP Hillclimb, PR Rallycross

RedGT wrote: Have good rally-X tires already (but from 2009, not good in the wet on the street but god-dayum do they move gravel/dirt well) and I picked up a set of true hollow spokes with 1-season general altimax arctic tires for $150 so I do not die in a light drizzle before I've had my morning coffee.

Remember this? Yeah, those tires are indeed REALLY REALLY bad in the rain. On the other hand, the VLSD works as well as they ever do. One tire fire for a while and then bam! now we're fishtailing.

But it made it to work. Just like a Real Car(tm). In theory it gets inspected by noon.

The zip ties will come off the mirror once the silicone is dry. The soft top seems to keep water at bay, which is impressive for how many holes and cracks it has, but hey it was free. 'hardtop install time' was taken up by 'hey...do I need a passenger mirror for inspection? Let me cram one on there just in case'.

I think we're set for rallycross. Just need to swap the seat - threw the race seat in in a pinch and that WILL destroy my back if I run it this weekend.

Also got about 12 tires, 3 seats, A/C unit, dehumidifier, too many spare parts, etc moved to the basement so there is room to breathe in the garage again. Mostly. Need to have another tire day and get these bald ones disposed of. The utility Vibe is going away tomorrow so we'll see if I can get 8 tires in a Mazda3.

Inspection passed. Emissions exempt too, the poor thing only went 2,500 miles since I bought it last year.

I swapped in the seat that has been molded to my ass over 6 years and 4 Miatas.

And the hardtop is on.

22 people signed up for Sunday's rallycross in Kempton. The snow/rain is supposed to hold off until right around when the event ends. I am really torn on tire choice.

• The General Altimax Arctics worked OK at this site last time despite loading up with mud, and are also safe on the street. Getting a bit low on tread for snow tires. 5-6/32?

• The old Snowtrakkers have more tread depth, are proven to propel the car better in loose gravel, and ought to be better in mud with a larger spacing between tread blocks. I think. But that is unproven. And they SUCK on the street in the wet, they've just aged out at this point. I am kinda hanging onto them in case I run at a site with embedded rocks again - the sipes do not penetrate the edge of the tread block so they are much more resistant to chunking apart than the Generals.

My opinion would be bring them ALL! :) Put the Generals on for driving there & strap the others into the trunk, a la the picture below. Generals suck in the mud & the large tread gaps of the Snowtrakkers should clear the mud & turn better.

That's what i was thinking about the snowtrakkers. They are on the car now. I don't care enough to haul both sets...I have done enough hauling of 4 tires in a Miata in my life. The Generals are not as bad as I thought either, still 8-9/32. They'll go back on for street duty and I'll see how quick I can burn them off. I am picking up 3 more generals mounted to 3 more hollow spoke wheels on Saturday for $100 because...well I can't really explain why. Hope my wife doesn't ask. Ok, the reason is that lots of aggressive dry street driving seems to feather the rears quickly and cause them to vibrate a lot when run on the front. So I don't rotate the tires, I just wear out rears faster.

Today I drove it to work again. First time for this car on these tires in the dry with full power on tap (it had needed an O2 sensor when parked and was running rich). It is a damn hoot! Heck this thing at 25° ambient might have more grunt than the STS car at 80°. I guess it kinda should, it has the same parts on it except for the stock muffler and 100k extra miles. You chuck it into a corner and it settles into this awful sloppy four-wheel drift that is super easy to control with throttle. It's quiet enough that I don't feel like I am waking the dead at 7am. I think that's the most fun I have had on a drive to work in years.

There was a dent.

I fixed it! Crap. Guess it was too cold.

So I fixed it more! Body color vinyl is really handy to have around.

I figure I'll clean up the rust on this one and see how much bondo is hiding under there...seal, prime, paint as best I can and then vinyl that too

Also added this for sentimental reasons:

Event today...Such a mudfest. And not normal mud, which is bearable. This was a layer of slick/snowy frozen mud atop very solidly frozen ground, so there were only a couple of places where things eroded enough to expose 'more grip'. Tires just wouldn't bite, there were virtually no ruts. First heat started out OK while there was still grass. By the end of their 6 runs, times were 10+ sec slower than their first runs. It only got worse from there, I got 3-4 seconds slower on every single run. And then 6 seconds slower on the last run because - wait for it - the trans didn't want to go into reverse. Sigh. Looped it with a slow 180. Wasn't going to be able to get moving uphill to make a 3-point turn and stay on course. Backed up through a gate, J-turn, back on my way. On course. Won MR by 17 seconds.

Initially I thought I made the wrong choice on tires, and I may have. But people on snows didn't fare any better and I won the class, so...crap. Inconclusive. But I think I will be running the General Altimaxes unless it is so dry it is dusty. Then I'll try these snowtrakkers again. It seemed to me last November that the Generals loaded up with mud in the tread voids but still had tread blocks exposed. The trakkers filled up and caked solid around the outside to turn into slicks. No bueno.

For all that mess the car didn't even get that dirty!

On another note, I plastidipped the trunk lid. I love this stuff. It was about 23 degrees. Put the can in my pocket for 20 minutes. Shake a lot. Spray. Damn nice finish.

I'm tempted to do the whole car but the paint is OK on most of it and I'm not actually a fan of the matte look. I just couldn't stand looking at the botched polishing job the PO did on the trunk lid any longer and I had dip leftover from doing the hardtop last year.

Also...stupid weather forecast. Left the car outside overnight while the trunk dried in the garage. "0% of precipitation" my ass.

This was also the first event on the $12 shocks. They seem to have survived and the car rode very well on course IMO.

BTW the car is still PR legal. I ran in MR because there was no one else in PR. But none of the MR cars were prepped. The 2002 had a gutted interior. The Volvo lost its exhaust/cat. The Fiero had a supercharged GM 3800 V6 in it...that kind of stuff. No serious RX prep.

It's like playing whack-a-mole. Whole cooling system has been replaced except the radiator.

Yesterday I definitely had a coolant smell. Today I found a small drip from the top hose on cold start. Old hose did this too so apparently the radiator neck is screwy in some way? Whatever, I am not going to replace a radiator for that. Fixed with rescue tape.

So the car responded by leaking somewhere lower on the radiator, looks like there is a significant ding in the fins right between the two fans.

FINE. I ordered a radiator.

Going to drop it off at home just now, and it developed a rotational noise at the rear when coasting in gear, but not on throttle or in neutral. Wonder what that's going to be?!

Changed the rear diff fluid. It was nasty.

While under there, noticed that one rear shock was set to '5' and one was set to '2'. Out of 8 clicks.

Oh boy. Wonder where the fronts are set?

1. And 8. That explains a lot actually.

So I put them all at '2' and drove it partway to work. Man, this sucks. Stopped and put them all up to 6. (Yes, it is that easy to do with the car on the ground and wearing nice clothes. berkeley me for forgetting to check them entirely after throwing them on the car real quick in march.) OK now it's a little better and definitely more consistent left to right in how rotation starts, but the body roll is still impressive. I've just been spoiled by driving the 3 for the past week I guess.

Might have stumbled into a trade of my red-hardtop-plastidipped-grey for a Laguna Blue hardtop in nice shape. Worst case, I plastidip it again. But when I go to sell it I should be able to get a little more for a rare color in good shape if I play the waiting game.

Hardtop trade complete, with $50 cash my way. Cant decide whether to use half of that to re-dip the top or if I like the blue.

I did some accounting and selling of parts and the rusty car is under $1900 out of my pocket right now, $1676 by challenge rules. Not bad. I don't know how long I will keep it. Thinking of throwing all the second-tier STS parts on it come spring, bringing it to a few events and hopefully plunk it in the top 10 in PAX and put a 'For sale $3k' sign on it. Conservative partout value is right around that, and maybe it gets someone else into a competitive car for cheap. Installing all the parts real quick (and some are already on) is easier than finding and shipping to a dozen different buyers anyway.

Rallycross today. I couldn't drive but went to watch a friend beat up my car. He finished 4th overall. Would have been 2nd except for starting the day with a little too much confidence:

https://www.youtube.com/embed/pSge9f7PHno

I made it out to watch with my daughter but it was 18 degrees and I wasn't going to make her hang out for 8 hours in that with nothing to do. She's barely 4. So what happens? She had so damn much fun watching cars and playing on the nearby playground (in 18 degree temps!) that we planned to go for half an hour and ended up staying for nearly 4 hours. I was provided turn-by turn commentary on every single car around the course. Great time.

Entering the new-to-me world of 'tuning'. Here's the plan:

• install wideband, use gopro as rudimentary datalogger.
• learn what 'normal' is.
• Add new plugs and wires, the car has occasional bogs and misses and such.
• Confirm what 'normal' is.
• add overclock crystal to ECU like the STS car has.
• observe again. The above mod is "known safe" but I am curious how much if anything it leans out the mixture or alters the open loop engagament point.
• Then install straight CAI tube and begin rotating the AFM to fine tune the mixture so it is mid-12's at its leanest point in open loop.
• in spring, repeat the process on the STS car.
• For the 2018 season, add an AEM F/IC-6 and actual tuning/dyno time.

So I pulled the cat off the STS car and welded a bung on before it. beats pulling the header. Installed that on the rusty car last night.

The O2 sensor cable is, for now, routed through the nonexistant shift boot

And it turns out the awful hesitation and bog this car has right around 3500 rpm in 2nd gear is not loading up with fuel as I suspected from the rich smell and bad fuel economy, but going pretty lean in the rev-up prior to entering open loop. After that AFR's decrease linearly from ~13 down to ~10.5 so yes it is super rich up top as expected. From some light research it seems this lean behavior is a common Miata thing however, for me, right now, the open loop engagement point, as signified by the AFR ceasing to bounce rapidly between 14.0-15.0 and go to a happier 13ish, accompanied by the car taking off like a damn rocket, is ~3500 in 2nd gear.

And ~4000 in 1st gear, 3000 in 3rd gear and ~2800 in 4th gear. WTF, I guess the stock ECU does things on a load basis somehow? It doesn't know what gear the car is in. This is repeatable by applying full throttle at ~2000 rpm. I could have sworn the other Miatas I have had, this changeover point is pretty much fixed. Maybe I am remembering wrong.

And then sometimes, the bog/dead spot/lean spot just isn't there. Driving along in 3rd gear and punch it at 2500? Might bog, might not! Who knows!

So...the first thing I am curious to do is swap ECU's - I have two others lying around. If the hesitation remains then I need to find something to fix or find confirmation that this is normal.

Does anyone know what is typical for cruise AFR? Yeah, it should be about stoich. But in this case it really ping-pongs between 14.0 and 15.0, all the time. I expected to see more like 14.5/14.7/14.5/14.8/14.5/etc. Not 14 -> 15 -> 14 -> 15. The narrowband O2 the ECU is reading is only a few months old.

Pulled back the carpet to swap ECU's and found this:

Oh, this E36 M3 again. One nut came off, one had enough hex left to get a 9mm socket to jam onto the formerly 10mm bolt, hit it with an impact and shear the stud off. The third one...I separated the cover from the bracket with hammer and chisel.

I have 3 ECUs so I took back to back warmed up drives with each in turn. No clear difference. Hey, had to check. I think one has slightly better throttle response but that's probably in my head.

Rallyx pics posted.

Over the past few weeks I drove around with the wideband installed and various combinations of ECU's and AFM's and tweaking thereof. For the daily driver/rallycross car I ended up back with the stock ECU and slightly tweaked AFM as this has the best midrange power according to the butt dyno as well as the happiest AFR's right around 3500-5500 rpm where most time is spent. Still stupid rich at redline. Actually the best combination is the above plus being at the sweet spot in warmup where the engine is warm enough to beat on but the car goes open loop at full throttle anywhere rather than waiting until ~4000 rpm. But that's a small window of time, 5-10 minutes of driving in winter. This is ~400 miles on the O2 sensor. ehhhh? Expected the plugs to be just as bad (unknown age) but they weren't terrible.

Another rallycross this past weekend, with one codriver. We finished 1-2 of 7 in PR. Tried changing shock settings but the surface was so different every run it was hard to tell what worked. In some cases I THINK we made improvements based on everyone else getting 6 seconds slower on x run and we only got 4 seconds slower. :-/ Can't really make any firm decisions based on that. We did borrow an impact and disconnect the rear sway bar during lunch break so we could stiffen the rear shocks without going too backwards. Maybe better, maybe not. But it got the car to stop bottoming out so bad. It's REALLY bad. You get on the gas and the car squats immediately. Just parked in the driveway the rear is notably lower than the front which, as far as I can remember, is never the case with OEM springs on NA Miatas. And they're low-mile springs too. Can't find anything wrong. Guess I just need more rear spring rate. Here's how it squats on accel vs. a similar car. And a horrible video of the launch into orbit in the middle of a slalom at 0:04 or so. https://www.youtube.com/embed/g4iruMxXjss And lastly, after the event I started the car to go home and heard this awful squealing. Evidently a V-belt can invert and walk halfway off the pulley but still function just fine. It'd apparently been like this for a while, possibly all of the PM runs. Due to debris in the pulley, I guess? Loosened up the alternator, got it back in place, tensioned it again and drove home. That went so well I decided to buy a $2 rockauto belt rather than a $15 autozone one. I've been driving the car daily...we'll see if the new belt arrives in the mail before this one explodes. :D

So I've finally put a new belt on since I got tired of retensioning this one every 50 miles as it wore in.

Now...the weather leading up to next saturday's rallycross calls for over 1.5" of rain spread across the week and not a whole lot of sun to dry it out. Plus temperatures just below freezing overnight tend to lock the moisture in the dirt and make nasty 'glare mud' or whatever you want to call it.

I'm really tired of skating around a mud pit at this site. I also have some old tires and a harbor freight oscillating cutter.

Here's how these tires loaded up the last time I tried them:

So I did a test run. Thought about going really drastic with it:

but I don't know at what point lateral stability is too compromised and I can always cut more later. So I settled on this:

Once decisions and tools were made, it was less than 20 minutes of work per tire. Totally worth it if this improves the tire's ability to clear mud out of the tread.

Now I am intensely curious how they work, and can't test anywhere until next weekend. All my gravel and dirt farm roads have been turned into warehouse complexes in the last 5 years.

Rebalance them or don't bother?

Cut another pair for the fronts? Maybe just some of the center blocks and leave the edges intact? I also have a pair of General Altimax Arctics kicking around not really doing anything that I think might work better due to a softer overall compound but I couldn't bring myself to cut up perfectly good tires yet.

I had the same belt inversion occur on our rallycross rental Escort GT (1.8 BP). It's didn't squeal; it just quit spinning the alternator enough to charge the battery, leading to a cat that wouldn't start. We put excessive tension on the belt and haven't had an issue since.

Those tires look great. I'd suggest cutting another set the exact same way for the front. Otherwise your new found grip in the rear will overpower the front grip and you won't be able to turn at all. I race a FWD car and ended up having to get mud tires for the rear after doing just the fronts. It was like driving a drift car as the rear tires would pack and then never stay on track with the front.

I wouldn't bother balancing. You're not going to be obtaining speeds high enough for it to matter.

I'd keep your Generals intact as they make a great dry surface tire. You cut ones will no longer be good in the dry as you've given up so much surface area.

Appreciate the input. To be clear I have 7 Generals and only 4 are doing anything right now I suspect the compound in them is better than the snowtrakkers I am cutting...but one of the things that drives me nuts about rallycross is how rapidly and drastically surfaces change compared to autocross. I don't really know and can't easily test to find out.

I understand entirely. We're up to seven sets of tires for the PF SRT4, in an attempt to dial in the best selection for certain ground conditions.

In a random small world occurrence, I was googling my real name last night and stumbled across this thread. Amusingly, my local friend with a Miata was giving you suspension advice back in 2015 and referenced me (David).

Do you have any plans of coming down to compete at the East Coast Rallycross Challenge in DC? I'll be flying out to be the event chair for it.

Thanks for the reminder on suspension. I am halfway through cobbling together extended top hats for the rear and keep toying with running about 350/200 springs. Or 500/350. I have stuff lying around. It seemed too stiff. I completely forgot that thread's advice from a year ago.

I think it's getting left alone for now...double header weekend on the 4th/5th and then my rallycross season is about done except that...yes I am considering the east coast challenge. Somehow that weekend is totally free of any autocross plans. Super tempting.

Four tires cut now.

NB front sway bar installed. Rear reconnected. "Oh, hey, this is really fun on the street now!" What can I say, I haven't had a car on stock springs in so long that I forgot how much of an improvement a front bar makes.

I ordered a pair of Amazon's cheapest LED light pods for the night portion of this Saturday's event. No idea how well they work but for $14 it was worth a shot. The car ran the last one with headlights only and I am told it was 'adequate'.

Of course after being 65-70 degrees for a while, the temp on Sat morning will be 15. Not sure how valid a tire test that will be, as we know the cut ones were no good in the cold on any surface.

Anyway. The rear was still sitting funny with the driver side 1.25" lower than the passenger side.

So I pulled the shocks/springs out. First of all, here's what's left of the bump stops.

New ones installed, hopefully they hold up a little better. The DS shock does indeed seem to have lost its gas charge (I assume) as it does not rebound on its own even with the adjustor set to '1'. The PS shock rebounds slowly at '8' and notably quicker at '1'. Switched shocks + springs to the opposite side, figuring the busted one may as well be on the lightweight corner. Now the ride height is closer, more like 1/2" low on the DS. As the entire assemblies were swapped side to side and all the bushings retorqued at ride height, I am just going to assume this is 'normal'.

Installed a new intake tube.

Longer overall, with an elliptical/velocity stack profile to the opening, a longer round-square transition section as well as a longer straight shot of square profile before the AFM. And this allows the AFM to rotate. At the moment the AFM is still level until I reconnect the wideband O2 and start playing around with that once the weather is a little mroe consistent. The butt dyno on the way into work today said GAWD-DAYUM which is a little unrealistic. I think it must be out of calibration after a few 60º mornings and suddenly back to a 40º one. But as the course is wide open on Sunday I'll take all the power I can get. Not super thrilled about the solidity of this tube, it's got a few flaws so I threw it on this car. Might being a spare intake to grid this weekend, as silly as that seems. It's a 5 minute swap if this one cracks.

I, inexplicably, did not buy a $600 complete turbo kit on Monday. It sold in about 20 minutes. Sorry.

This just makes me laugh now. But they're bright as hell and only draw 3 amps!

Doubleheader weekend completed. Haven't had a chance to type anything up but sitting at home with a cold on saturday night so here goes:

The cut tires worked great. Once I was about 3 runs in I figured out how to chuck it around like a subaru driver tries to, because despite the site being the same mud pit it was last time, now I had enough grip to change direction on the fly rather than just trying to make it through the course clean. With that attitude change I went from 5-7 seconds per run behind Shawn's unicornmobile on mud rally tires to 2-3 seconds. Also, uh, hit a whole lot of cones. As I said, like a Subaru driver!

By the time the evening session rolled around, the course had dried out for about 70% of it, and then my cut snows actually had the tire advantage over the aforementioned mud rally tires. But 2-3 seconds per run was not enough to make up for the morning deficit. The surface got so dry and tacky we had dust clouds and tire squeal.

Couple pics. Finish writeup later.

My codriver was at his first rallycross and absolutely loved it, as well as the way the car handles. In the AM he was 3-4 seconds back, in the PM he was ~2 seconds back which is about where he usually runs at autocross. So he adapted to the dirt pretty quickly.

Rallycross car has been demoted to daily driver mode and will soon be demoted further to 'storage' status for most of summer. Just as soon as I put this massive pile of crap back onto the STS car:

I bummed rides this weekend in an STR NB Miata on Saturday and an ES NB Miata on Sunday. Then there's no autocrosses I can make it to until the end of April so that's when I need to have the car assembled.

Unless my friend gets his RX7 shocks back before then, in which case we're running that at a whole one event and then hauling it out to the pittsburgh match tour. Long story short, I need to drive out there in something with four seats and he is more enthusiastic about bringing his car than mine for personal reasons. Ain't my truck and trailer so I can't exactly argue with that.

Well...the plan of "no Tours/Pros this season but maybe I'll go to Nationals for the first time" lasted a whole month. Now signed up for a tour and a pro. Car is going back together.

Timing belt, water pump, crank bolt, CAS o ring, ALL hoses, radiator are done.

Shocks, springs, sway, intake, cat, shifter, console, wideband, seat, alternator, timing adjustment still to go yet.

The state of the garage these days. Sigh.

At least the engine is clean.

Take it apart....

And then put it back together. Mostly, anyway.

Didn't like how close the header runs to the hoses, and with the blanket installed it rubs a little. Plus gold is fast right?

Someone has been munching on injector wires. Based on the dirt around them, this has probably been like this for a long time, maybe before I bought the car. Which reminds me, I have new injectors that have been sitting in the bedroom for about 6 months.

Beautiful sunset last night, enough to make 'rusty' look good.

The PCV that came off the car would still rattle, but pretty unhappily and inconsistently. Hoping that explains why sometimes the car used NO oil for a month at a time yet sometimes a 2 hour highway drive would make half a quart go away. New one installed now.

I am loving how easy it is to work on with almost no rust. The only thing I had trouble with were the lower fan bolts to the radiator and ultimately they did come off and even got reused!