codrus

Yeah, I agree it's probably not the source of the vibration. It *is* something I need to fix though. What did you do to fix it with your 245s?

I think the exhaust hitting the motor mount is a likely candidate. There's maybe 3mm between the WG tube and the corner of the "cup" on the mount.

--Ian

icantlearn

I went in with a dremel and cut out as much as I could. Then I took pliers and bent the edge down so that if there is contact it wont cut the tires, it will just polish the tab or tire if that makes sense.

The WG dump probably isn't the source either TBH. My downpipe was rubbing on the tub for a while before I found exactly where and the vibration wasn't enough for me to stop driving the car. Granted, I have no idea how bad your vibration is so

Both should still be fixed tho.

codrus

I'm tired of breaking Miata transmissions, so I bought a BMW transmission swap this evening. It's also a BMW ABS swap.





--Ian

18psi

iTrader: (76)

Such an elegant car.

curly

iTrader: (25)

Oh god. Have fun with that one! Too much experience with the E46 m3s, specifically the S54. We have 5 at the shop right now. 4 of which still have the s54...

18psi

iTrader: (76)

Better check them main/rod bearings right?
And rear subframe....and like 100 other things.

codrus

Rear subframe has already been done, as has the VANOS. Rod bearing replacement is on the list of things to do before it gets turned into a caged track/race car.

This one is an SMG, the plan is to convert it to an E36 5-speed and sell the SMG. This path was recommended to me by TC Design because the 5-speed is less prone to synchro wear, I'll never use 6th gear on the track, and the SMG cars are cheaper to buy (more so because the SMG parts in good working order can be sold for decent money). So, yes, my BMW needs a BMW transmission swap.

--Ian

codrus

So the M3 will be taking over track car duties, but I've got an event next week, and you can't drive BMWs at Miatas@WRLS, so I still need to fix the track vibration problems on the Miata.

Today I pulled the downpipe out, took off the driver's side motor mount, and cut a big chunk of metal off the corner of the "cup" where the exhaust had been hammering it. That's a very strong candidate for the vibration I was feeling at the track. No photos, sorry.

--Ian

codrus

So I took the Miata to Thunderhill last week. Parked next to a cool Norma sports racer with a K20 motor in it. Apparently it does low 1:20s at Laguna, yow.



This was my second time towing with the new truck. Milage is still terrible -- 9.2 mpg on the way up, with the cruise set at 65 the whole way. On the previous trip I had a bunch of stop-and-go traffic I could blame, but not this time, so I don't know why it's turning in lower mpg with the same trailer than the old truck did. Also, despite spending a bunch of money replacing almost everything in the steering system, it's still got some slop/binding in there that makes for kinda sketchy stability around moderate bends on the freeway when towing. Grr. Ah well, at least it climbs hills better than the old one.



So how did the car do? Not so great. It was fine out on track, but idling for cooldown in the paddock had some issues. After the first session it started spontaneously stalling while idling -- I was pretty sure I knew what this was, so I swapped out the cam sensor and that problem was cured. Yay.

On a positive note, the cutting on the motor mount has fixed the vibration from the last couple events.



Went out for my second session, again it was fine, but idling in the paddock it started spewing coolant out the overflow tank. Looking at the datalogs suggested that the coolant temperature sender was acting weird, but I wasn't sure if that was cause or effect and didn't have the parts to try to debug it there in the paddock so I towed it home. That's 2 track days in 2 weeks with only 3 sessions between them.

Pulled it apart for diagnosis when I got home, put the sensor in a pan of boiling water and sure enough the ECU is reporting a temperature that's too low by about 30-40F near boiling and 5-10F around ambient. Bad sensor? I ran over to my FLAPS and bought a new one ($34), but it did the same thing, argh! Pulled out the megasquirt, started checking the bias resistor, voltage supply on the board, resistance at the back of the connector, etc. Somewhere in that diagnosis it spontaneously fixed itself. So there was a loose connection in the wiring somewhere that got fixed by plugging and unplugging things, with no guarantee it won't happen again. ****.

I'm really frustrated with the car, which reinforces the BMW decision. On that note, I had the local BMW shop swap the rod bearings in it, because apparently they wear quickly on S54 motors and I didn't feel like DIYing it. No kidding they wear quickly, 90K on this car and the rod bearings were through to the copper! None too soon on this replacement.



--Ian

curly

iTrader: (25)

icantlearn

did Edge do it? BTM? BRR?

codrus

Bavarian Motorsport | Bavarian Motorsport BMW Service and Repair in the Bay Area since 2002

--Ian

codrus

Took the M3 for a drive in the mountains and brought the nice camera along. Serendipitous timing on this shot, right as another black M3 (OK, mine is technically very dark blue) went by:



--Ian

codrus

There's a saying about doing the same thing over and over and expecting a different result, right?

Loaded up for the GGLC day at Laguna Seca tomorrow. Let's see what breaks this time.



--Ian

icantlearn

I don't wanna jinx it, but I feel like its gonna hold up this time around. (knock on wood)

sonofthehill

iTrader: (1)

Wishing you good luck!

Scaxx

Good luck out there today!

codrus

Well, I did six sessions and the car seems to have survived with nothing but minor issues.

It's still doing the "incorrect reading on the MS coolant temp sensor" thing. I had an old coolant temp sensor installed that I used to use for a gauge (before the dash display project), so I hooked that up to the Arduino, and wrote some code to monitor it, compare to the value it's getting from the MS over CANbus, and set an LED if they differed by more than 5 degrees. That LED was on a lot, which suggests that the wandering coolant temp sensor value is continuing. As a band-aid fix for that I tweaked the MS config so that it basically always has the fan on when the engine is running. Further investigation into this is warranted.

The vibration on lefthanders is back, although nowhere close to as bad as it used to be. Took a quick look under the car when I got home and yeah, it's starting to run the downpipe on the motor mount again. Looks like I need to take a bit more off.

It's got a strange creaking/squeaking noise when driving over bumps now. No idea what that is, but doesn't appear to actually be hurting anything.

More bump travel in the Xidas means it shredded the fender liners. I pulled those out and noticed that the 4 sessions had got the (brand new that morning) pads tapered down to nothing on the driver side (passenger side wasn't as bad for some reason). I yanked them out and swapped in the used set form the Thunderhill event (had only done 2 sessions there, barely any wear).

I'll grab some data and video off of it later.

--Ian

icantlearn

sticking caliper?

codrus

It doesn't appear to be dragging. Might be the oilite sleeves in the new poly bushings making noise -- they're not supposed to do that, but it is a new part so it's possible.

Also, one other thing I've been hunting on the car for a while is a tendency to jump sideways when getting on the brakes at high speed. Swapped out the FM PowerLite rear calipers and went back to a set of stock calipers on M-tuned brackets with the same sport rotors and now it's much more stable.

--Ian