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Wow. What a fun weekend racing with the 24 Hours of Lemons at Sonoma. The Ecotec has a good balance of power for the Miata. We basically went from my garage straight to the race. The car had never been driven or tested.
The good:
- Car is fun, has a good balance of power, and is easy to drive
- We were on track about 50% of the time Saturday, and all day (when available) on Sunday
- 3 out of 4 of us set our best lap time at the track, this is after 7 years racing our previous Volvo wagon with lots of development
- With our seat setup that raised as we moved forward, everyone was able to see and find a driving position
- The engine with the stock E67 ECM was easy to start when cold (< 50F) and provided smooth power, really good torque
- Car stayed cool, but it was also cold at the track
- Untuned MK60e5 ABS worked amazing
The bad:
- Car came with a welded diff. It is awful in the paddock causing the rear end to bind, making horrible noises, suspension to flex, and wheels to hop. On track it worked okay, but it pushed a little in corners, the rear subframe bolts loosened, the bolts between PPF and diff backed out, and one fell out.
- We blew a front bearing as the hub was installed with the machined washer flipped incorrectly.
- The E67 was a stock '06 Chevy HHR tune with VATS and a lot of the CEL options disabled. We had to do some mods to it to get it working at the track such as disabling VSS (which normally comes from something that no longer exists) and adjusting max RPM in park/neutral which was limited to 4000 RPM
- The suspension is not optimal, the only setting we tweaked was toe. It is Bilsteins with 8 7” 700/400# springs. It sits at stock height or maybe higher. I could not go any lower without helper springs. It is also rubbing on the adjustable shock sleeves
- The $100 5 speed I got on FB marketplace is crunchy going into 5th, so I just stopped using 5th and wound out in 4th instead
- We had other teething problems such as leaking brake fittings that we also found in the paddock or on the track
- Fan is not getting turned on for some reason
Next steps:
- New rear diff. Torson? Ratio? Whatever ratio we have worked good for Sonoma
- Get some gauges and idiot lights. We only had a tachometer and water temp.
- Fix the suspension with an ideal ride height and camber
- Make it look pretty
Some pictures from the track
Ready to race!?
We had 4 black-flag-alls for oil cleanups and wall resets, the most I had ever seen at a race.
Practicing driver changes. With a 24 gallon fuel cell, we didn't need to fuel up. We only did 1 hour stints as it was our shakedown race.
We had a 1.5 hour fog delay Sunday morning, so we had a cars and coffee on pit lane.
So rad, dude. Glad to hear it was a good weekend, and the "good" list seems to have outweighed all the "bad's". Seems like most of the issues are finite and should be easily remedied.
What needs to be "prettified" about the exterior? I see nothing that needs to be worked on
That's so awesome, perfect results for a shake down weekend.
Yes, grab a torsen. You'll eventually want a 6-speed, LE5 torque will break the 5-speed eventually, maybe not if you don't tune it though. That being said, your options are 3.9, 4.1, and 4.3. The 4.3 is probably too short, and will probably be the most expensive. The 3.9 is probably ideal to keep RPMs down, not run out of gearing, and lengthen gears. Not good things for a lower powered sprint or track car, but awesome things for an enduro car. 3.9 is however the more desirable ratio, so it may be less available or more expensive, or both. So the 4.1 is really the answer. Probably the cheapest, most plentiful, and splits the difference between taller/boring gearing and shorter/faster gearing.
Edit: as for the bilsteins, I think the common lengths are 7" or 6" with a helper. Rubbing on the collars is common. Try to get it adjusted sooner rather than later, before the threads get too damaged.
That's so awesome, perfect results for a shake down weekend.
Yes, grab a torsen. You'll eventually want a 6-speed, LE5 torque will break the 5-speed eventually, maybe not if you don't tune it though. That being said, your options are 3.9, 4.1, and 4.3. The 4.3 is probably too short, and will probably be the most expensive. The 3.9 is probably ideal to keep RPMs down, not run out of gearing, and lengthen gears. Not good things for a lower powered sprint or track car, but awesome things for an enduro car. 3.9 is however the more desirable ratio, so it may be less available or more expensive, or both. So the 4.1 is really the answer. Probably the cheapest, most plentiful, and splits the difference between taller/boring gearing and shorter/faster gearing.
Edit: as for the bilsteins, I think the common lengths are 7" or 6" with a helper. Rubbing on the collars is common. Try to get it adjusted sooner rather than later, before the threads get too damaged.
Thanks for the feedback, especially on the ratios. 6 speed is on the list after I go through the three $100-200 transmissions I collected.
I went back and looked and I have 7” springs. I am going to mess with them when I pull the car out of the trailer, ride height was low on my list for the mad scramble to get it to the track.
I'm a big fan of 4.1/6-speed/Torsen combo for atmo cars, having run it on my dual duty cars for years. Just note the Torsen stops being an LSD when a rear wheel is in the air ...
I'm a big fan of 4.1/6-speed/Torsen combo for atmo cars, having run it on my dual duty cars for years. Just note the Torsen stops being an LSD when a rear wheel is in the air ...
I have had rear wheel lift with sub-optimal spring rates and a rear sway bar that was too stiff trying to compensate for lack of roll stiffness during autocross.
yes, if you try to use anti roll bars to add most of your roll stiffness. Better to use spring rates rather than couple your independent suspension (particularly in the rear) with excessively stiff anti roll bars.
I have had rear wheel lift with sub-optimal spring rates and a rear sway bar that was too stiff trying to compensate for lack of roll stiffness during autocross.
Originally Posted by The Australian
yes, if you try to use anti roll bars to add most of your roll stiffness. Better to use spring rates rather than couple your independent suspension (particularly in the rear) with excessively stiff anti roll bars.
Currently we have no rear bar, so good to know when/if we plan to install a rear bar. We have the solid Racing Beat in the front.
Yes, they can. As above, depends on how they are set up. I used the NA 11mm(?) rear bar and tuned around that. I have a photo somewhere of my car on a long fast corner, the inside rear at full droop. I suspect the tyre was actually slipping a bit so light was its load, but there was enough resistance for the outside to remain powered.
The litmus test around here is a tight corner approached via a heavy downhill braking zone, where the track turns across the downhill slope, probably the worst combination for a torsen. It took some fiddling, but after that I never had a problem with drive through there.
Spent part of the day yesterday figuring out the CAN bus frames for this e67 ECM. It doesn't seem to use the standard GMLAN CAN IDs.
I had it working with the OBDII codes, but I wanted to build some shift lights and a engine temp warning light and I only know how to do that on an Arduino with CAN. I figured out RPM, engine temp, IAT, and MAT. Got bored after that.
Torsen diff arrived from eBay yesterday, going to tackle that today.
My biggest issue with the car at our first race was the welded diff. It was horrible, it felt like the rear end was going to rip off the car when I turned in the paddock. At one point during the race the two rear PPF to diff bolts backed out, destroying one.
Welcome a new third member to the family. 4.1 Torsen was delivered and installed. I took it for a quick spin around the neighborhood and I can make a U-turn without any crunchy sounds. The oil in the carrier was only 10 hours of use old and was nasty.
While I was under the car, I noticed this nasty fuel residue. To be safe, I pulled the fuel cell bladder out.
There was fuel in the bottom of the metal container, so I added a little air to the bladder and checked for leaks. None were found, but the cork seal for the fill plate looked nasty, so I replaced it. Unknown age foam felt good, I didn't see any disintegration. Having it out of the car really emphasized how big 24 gallons is.
Then I painted the car blue with a can of Rustoleum and a cheap paintbrush. Looks good at 20 feet.
Worked on the dash a bit too.
Going to try the MTTC event at Buttonwillow on January 24th. I have never participated in a time trial event. I also don't think I have ever driven 13CW, just 100s of laps of 1CW in my old Volvo. If anyone else is going, please stop by and introduce yourself, I will be pulling in Friday night. Silver Ram truck, 24' enclosed trailer.
I also got some helper springs, so I am going to drop the ride height a bit. Any recommendations for endurance racing? 4.5" front and rear at pinch welds? Do I even have pinch welds anymore?
Well I added helper springs and lowered it as far as I could and got it down to between 5" and 6". It is hard to tell as the pinch welds are basically gone. I either need to ditch the helpers or get shorter main springs. They are 7" x 700# and 7" x 400# right now. Regardless, I loaded it up in the trailer for MTTC at Buttonwillow, I hope to get to the track before dark tonight. I have never done 13CW before, only 1CW. If you are also coming, please say hello. I will be in a Silver RAM 2500 with Carson enclosed trailer.
Robb
Sick. My car was also ride height limited with 7" springs on my diy billies. 6's with helper springs would be better for sure. I was able to get to the taller side of the SPM specs but no lower.
Sounds like this events gonna be lit! Def meet up with the other mt.netters, it sounds like it will be a good turnout!
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