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Went out for a Miata scoot and more shakedown. So far everything is working perfectly. The brakes felt soft for a little while but they’ve bedded in again. I plan to take it to work this week and maybe iron out some small issues with the throttles sticking again, but it’s so minor I may leave it alone and focus on the Stealth and Jeep for a while. Next time attack is in two weeks
This past Saturday was Motoroland Fest Round 8. During the week I had time to drive the car in the mountains and around town a good bit and I was confident the CHUB project was finished. Initially the brakes felt soft, but after some drives they started to come back. The tires are starting to look well wore and I fear they may not make it to the last two events (one time attack, one autocross). At any rate, I ran through the usual checks, rotated the tires with the fresher looking ones on the right side, and loaded up Scooter for event.
The day started around 65F, but it was windy, which was throwing dirt all over the track. Nate brought his friend, Logan, that was recently inducted to the hair dresser ranks, and he wanted a ride along in Scooter. He rode on the first session where I usually go out and get a grip on how the track feels and if the car is behaving well. I got stuck behind two slower cars for all hot laps and decided to go full send in the cooldown, which ended being a 1:33.xx . I was ok with that, if a bit frustrated about the traffic, but Logan had a fun time which was the most important part. The car felt pretty good, and notably with stronger brakes (i.e easy to lockup). I believe the brakes felt stronger because I was experiencing pad knock back before, and the CHUBs may have fixed it?
On the second session track temps were near perfect. I had the tires at 22psi cold (24-25psi warm) all around and immediately the traction levels felt much higher than in session 1. There were a couple of instances where the rear lost traction unexpectedly mid corner, and that caused me to play it a bit safer. Overall landed a 1:32.7x, over a second slower than my PB. It was a fun time. Scooter felt pretty good, and I'm very happy with the brakes, even if I have to re-calibrate my lead foot ...
Flatspot successfull. Foot recalibration required
Calibration finished
Session 2 times
That was the end of the event for Scooter. I decided to call it good after those unexpected grip loses, the track getting slower in the heat, and I also had to help my friend trailer his car to a shop, return and load to go home. Overall a decent day and got to ride with Nate in his 10AE and had a blast with the top down.
Mint. Low miles. Never tracked
Before the event I got to play with the throttle cable adjuster hoping to fix the throttle hang at idle and also the sticking the first 1% of movement. Aside from the bolt-style adjuster it also has 3 major positions you can select. I had been using the furthest position, which makes the cable as "short" as possible, so I went on and changed it to the middle setting to increase the effective length of the cable and adjust from there. You can see how it was in this picture:
That initially seemed to work very well, and I was excited, but I found during the event that it would still hang at 0.4% open after small throttle application in the pits once the engine was properly hot. The throttles don't stick anymore though, so that's cool. Like before, giving it a hard blip would close them back to 0, so I'm back to thinking the cable is hanging somehwere, maybe in the housing or on the slot it has eaten into the aluminum adjuster. It's getting annoying though. I may contact Borla as well and see if they recommend something else, or making a new adjuster of a different material.
My face when the idle is still hanging ...
Onwards to the next event now. Round 9 will be the last points event of the year, and there will be an autocross after that which should be good fun too!
Great work last weekend man, as always! Was a good time hanging out with the crew. Thanks for giving the homie a ridealong, he's getting amped to get out on track and I'm psyched to see it.
Thank you dudes. It's not fun getting flatspots, but at least the smoke is amusing haha.
Haven't driven Scooter since the trackday because I'm avoiding dealing with the throttle cable. I'm also dealing with dead injectors and throttle cable issues in the Jeep now . Another trackday is coming up in two weeks and one autocross after that. Should be a fun end to the season.
Don’t know the extent of the damage yet, but 1 nut and 3 washers that held intake trumpets are unaccounted for. Not how I envisioned to end the season. The culprit is a new set of trumpets I 3D printed that shrunk more than expected and I failed to recheck and retighten this morning
If it is any consolation, my high revving high compression BP race engine swallowed three butterfly screws over a year or two before I wised up and replaced the stock TBs with a Junk2. I found an indent on a piston, matching indent on bottom of CC otherwise nothing adverse happened. Three bullets dodged, I don't recommend it though.
I expect that nut is firmly imprinted into the head and the piston is tapping it each revolution. That's my guess, at least. Maybe the washers went straight thru. Ha.
I don't think it gouged the cylinders since it doesn't smoke. It seems to fire RIGHT up and have good compression so I think the valves are intact.
That said a lot of hardware probably ran thru the motor so I agree, not holding my breath either.
Fingers crossed! My old roommates throttlebody sent a screw into his piston - enough to leave a nice indent of a phillips head - and he drove something like 6+ hours and did a trackday the next weekend without issue, so there's hope.
Also, while I assume 3d printed parts aren't at the top of your list right now, if you want to print some seals for those COPs I've got a file for you here. Mine have been on the car for about a year, printed in TPU. I couldn't tell if you had any seals from the video. https://www.thingiverse.com/thing:69.../thing:6922139
Ooooof, that's a bummer dude. Sorry to add to the echo chamber but I hope it's easily repairable in the least intrusive way possible.
If it's any consolation, we had a 3.5 EcoBoost Raptor roll into the shop last week that just had a timing job done elsewhere. Really bad misfire on cylinder 3 that would come and go while driving and worsen at idle. Ended up pulling the intake manifold and found a whole *** M6x30 bolt stuck in the port, intermittently wedging between one of the valve seats and sticking it open.
Miraculously, we pulled the bolt out and cylinder 3 compression went back to perfectly matching the other cylinders. Somehow it didn't wedge between the actual sealing surfaces of the valve seat and face. Afterwards, the engine ran fine and you wouldn't know it had been chewing on a bolt for a while. We're still replacing the head, but I found the results pretty surprising. Maybe (hopefully) you run into a similar weird situation with your top end...
Fingers crossed for ya. If the worst does happen, I know a guy with one or sixteen BP engines sitting in his garage that's probably willing to lend a hand (Nate. It's Nate).
Thank you all for the words. It sucks and I'm still shocked about it. A borescope is on the way to inspect the cylinders before I go in deep with disassembly.
Zak, that's a heck of a story! I did look through the throttles and didn't see anything on the intake tract or valves. The missing washers and nut are very small, so they likely did sneak into the cylinder. We'll see what the camera finds.
On the positive end, the engine did give me one last full session and felt strong. Had a minor hiccup at 5-5.5k RPM, and only started tapping in the pits. With my wife as passenger we did a 1:32.25 which was good for first place in D class, and cemented first place for the season. Exciting and awesome if not for the engine failure.
If the worst has happened, I plan to rebuild it with JDM pistons, Carrillo A beams and deck the block for a bit more compression. Maruha 252 cams, and light-double springs with SUBs and port/polish the head. If someone has a lead on a CNC BP6D head, let me know.
On the positive end, the engine did give me one last full session and felt strong. Had a minor hiccup at 5-5.5k RPM, and only started tapping in the pits. With my wife as passenger we did a 1:32.25 which was good for first place in D class, and cemented first place for the season. Exciting and awesome if not for the engine failure.
Borescope arrived and Cylinder 2 and 4 have signs of damage, with 4 being the clear winner. Cylinder 4’s spark plug also has signs of getting smacked by something. Unfortunately I got swindled on the mirror and magnet attachments so I can’t see the bottom of the head. No matter, as it’ll have to come out anyways. At least it seems the cylinder walls are in good shape with a mirror finish and crosshatching.
Cylinder 2 Cylinder 4 Cylinder 4
got a quote from an engine builder today and it’s much more than I expected but I’ll push forward. It just means some parts will have to change. They want to inspect the block first so the sooner I can make time for removal, the better. Cams and supporting head parts are getting ordered soon.
The garage got very dusty and some got in my eyes, so I’m going call it good and chill out.
Dang, that's a bummer. I'm trying to figure out how the piston would even contact the spark plug like that, assuming that's what happened.
Am I wrong, or is there a hole in the piston in the lower left corner on piston 2? Is that just a camera artifact?
I don’t think the piston touched the plug, instead whatever was flying around in there did. If the piston had done it, I would expect the plug to be crushed, plus some other heavy damage to the piston hitting the head?
The images are darker than I saw on the camera. Whatever it is, it is shiny, so I think it’s a piece of a washer. Could be a gouge in the piston too. Don’t know really.
I thought the same when I saw the pics, but the way the motor ran I'm pretty confident there's no way it has a hole in it. There would have been crazy blowby.
I told him he could probably get away with running that bottom end, but scooter is a nice car and deserves better. In my seat time rat I'd def give it a whirl tho. lol.
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. Another trackday is coming up in two weeks and one autocross after that. Should be a fun end to the season.
