aidandj

iTrader: (5)

Ian, what did you use for your final dwell numbers?

codrus

So we looked over the tables of the stock Corvette dwell numbers, they range from 2 to 10 ms, depending on voltage and RPM. We concluded that while it would be possible to use the 2 2d tables in the MS3 (nominal dwell vs RPM and dwell trim vs battery voltage) to simulate the Chevy 3d table, it probably wasn't appropriate to do it. For one thing, a 24 psi turbo mixture is going to be harder to set off than a naturally aspirated V8, so I would likely want more at the high RPMs, and for another I'm not particularly concerned about try to eke every last percent of fuel economy out of it, so I'm not going to run it particularly lean at low RPMs. We also concluded that the primary reason for wanting to minimize dwell is coil life, and my car sees a few thousand miles a year, so even if I shorten the life and only get 50K out of them that's still 15 years.

So I borrowed a variable power supply from Jason, and measured the saturation voltage curve.



Flipped the probes around this time:



And got:


So I decided to set it for 3.5ms nominal dwell, burn that voltage saturation curve into the battery compensation table, not do any RPM or MAP based trimming, and see what happened. 3.5ms turned out not to be enough at 21 psi, so I turned it up 4.5ms and it was happier.



So now I just need to schedule a dyno session.

--Ian

codrus

So while driving the car around last week to test out the FM coils, the brakes felt really really bad. Lots of travel, poor bite, hitting the stop before ABS engages, etc. I had swapped out the brake booster hard line for a hose due to interference with the LS3 coils in the FM bracket, and was worried I'd screwed something up.

Nope. The problem simply turned out to be that running the BP-20s at FM's mini track day was too much for them. I'm kinda surprised, I knew they weren't track pads (I use them for street and autox, they work well for that), but this is only a go-kart track, you never get out of 3rd gear, and I only did four 5 minute sessions. The pads were probably half-worn going in, but those 20 minutes completely destroyed them.

Tapered wear as before with the Wilwood Bs:


No wear groove left for half the pad:


Swapped in a set of new BP-20s, flushed the fluid as well. I'm a bit worried that I may have worn a taper into the rotors, because the new pads did not want to go in the last little bit to line up with the mounting holes, and there's no lip worn on the rotors. It feels right out on the road, though. We'll see what happens with them -- I have a second set of rotors for the track, so I'm not worried about that.

And yes, that's a new set of Dynapros in the background. I was reading the "wilwood maintenance" thread and recommendations of replacing Dynalites every 3-4 years and realized mine were 11 years old. Yikes! I have another set new-in-box that I'd been planning to swap in, but decided it made more sense to put in Dynapros and sell the NIB Dynalites instead.

So why not put them in today? Well, I don't have pads that fit them except for an old set of Hawk Blues, and I'm not using those. DTC-60s are on their way. I'm pondering Aidan's idea of using the center hole with a big-*** pin to put in the BP-20s, but didn't have the right parts to do it today. I hope to swap the Dynapros on this week before Laguna, but that may or may not happen.

turbokitten

Note that 4.5ms nominal dwell is at 12.0V. At 14.0V it's 3.6ms actual.

aidandj

iTrader: (5)

Won't work. Big enough pin won't fit through the pad, too small of pin lets the pad wobble around. I looked into it, but it doesn't really work.

codrus

Making small holes into big holes is what drills are for.

--Ian

codrus

I went out and looked at it some more. The inboard hole is threaded, the outboard one is drilled larger. So I'm thinking you drill out the hole in the pads to the diameter of the outboard, then get a bolt that will go through the outboard hole, through the two holes in the pads, and thread into the inboard hole. Make it an allen-key bolt and it'd actually be easier to install/remove than the standard spring clip.

I *think* there's enough room for a bolt like this to clear the rotor, but I didn't have one handy to check.

--Ian

turbokitten

Spring clips provide positive retention. As the caliper flexes, heat-expands, and vibrates, the spring pressure keeps them in their notch.

Bolts back out.

You might want some combination of stover nuts, safety wire, or high-temp loctite.

codrus

So I took the car to Synergy Auto Works today and ran it on their DynoJet. Learned a few things:

- The timing numbers I tuned at FM were close, but needed a tiny bit of tweaking at sea level.
- The LS3 coils were slightly unhappy at 240 kpa and 4.5ms nominal dwell. 5.5 cured it, didn't try to tune it further on the dyno.
- On 100 octane it will reach MBT at 240, barely. It will not reach MBT at 265.
- The valves are floating at 7000.
- FM's dyno was very optimistic, it reported 325 at 215, with the same tune this sea-level DynoJet said about 275, both numbers uncorrected.

Unfortunately, it wouldn't go over 300-310 rwhp. At 240 kpa it's basically flat at 300 hp from 5500 to 7000, at 265 it goes flat at 310 from 5200 to 7000. It smells like something is flow-restricting in the exhaust. The primary suspect is the muffler, where it dumps into a cavity, if that turns out not to be it then perhaps the head.

Green is 215 kpa, blue is 240, red is 265.



Did a quick valve lash check this evening as well, a few of the valves are a bit looser than I'd like, but nothing that needs attention before Laguna Seca.

--Ian

codrus

Oh, it was also generating sync errors on the dyno occasionally. I suspect the cam sensor may have been overheating -- I have a new one of those I should swap in before Laguna as well.

On the brake front, I'll probably just buy another set of BP-20s with the right backing plates on them.

--Ian

patsmx5

iTrader: (16)

Can LS coils run 5.5ms on a track and live? Check your duty cycle at high RPMs, that's really aggressive duty cycle on those coils. I too had to run 5.5ms to fire a plug without a misfire at .040" gap with my IGN1A race coils, but like I said I went to .030 and dropped the dwell to something more reasonable for reliability.

codrus

At 7200 RPM, a spark plug fires every 16.6 ms, so that's 33% duty cycle.

I have them gapped at .032. As I said, I don't know if 5.5 is required -- 4.5 was not quite enough, but 4.8 might well be. I can tune that on the street, I don't need to spend $135/hour doing it on the dyno.

Also note that, as TK observed, nominal dwell is at 12v. The car is more typically at 14v, and the voltage curve requires something like 25% less dwell at that point.

Finally, I don't think I'm going to run 240 kpa at Laguna, I'll probably turn it down to 215 or 200.

--Ian

codrus

So I was a lazy bum on Wednesday and Thursday and didn't finish track-prepping the car. I was taking Friday off, so I figured I'd just do it in the morning.

Filled the Miata with 100 octane, got the DTC-60 and track rotors installed, fixed up the radiator ducting (I really need a permanent solution for that, instead of something that's good for one track day and then needs to be re-taped), swapped in the cat-delete pipe, reinstalled the belly pan, and put on the RRs. Loaded stuff in the truck, went and got the trailer (the new house has trailer parking, and that will be so much more convenient than driving 20 minutes to a storage place), fueled the truck, loaded the car on the trailer and left at 3:30, only 30 minutes after I'd planned on it.

That was a mistake. Traffic was terrible, it took 3 hours to get to Monterey, a trip that I can do in just over 60 minutes at 6AM, and shouldn't take more than 90 minutes normally. Ugh.

Well, at least they didn't close the paddock until 9, so I could go drop off the Miata and trailer even though it was late.

No pictures, was too busy actually doing stuff. Met up with Aidan and Ed at the BBQ, no sign of E02K or gesso yet.

--Ian

gesso

iTrader: (1)

We didn't actauly leave Redwood city until 6:30 or so and then there was traffic all the way to Santa Cruz :(

But, on the upside for you, I remembered to pack all seventy billion of your fancy Miata tools the G and I have "borrowed" over the last year! We should make sure you get those back this weekend.

Did they give out parking passes or anything at the BBQ, and/or does it seem more low key than last year?

codrus

So Miatas@MRLS appears to have been a success this year. Historically I've had about a 50% failure rate at the event, six events of which 3 featured major breakages on the car (head gasket, 5-speed, then TB screw last year). I say 'appears' because the TB screw breakage didn't actually become apparent until the weekend after last year's event, and all I did was roll the car off the trailer and into the garage last night.

The cooling system was flawless, I love the TSE radiator. The 11.75 TSE brakes with DTC-60s worked much better than any other braking system I've used at Laguna as well. The pads are done, but that's 3 track days on them so that's expected.

It was blowing the wastegate hoses off on Saturday. Zip ties on the EWG are a bad idea -- they get hot and brittle and fall off. I borrowed some safety wire from Andrew on Saturday and did all six wastegate-related lines (2 on the EWG, 3 on the solenoid, feed from the throttle body inlet) and that held up for the rest of the weekend. Hose clamps are probably the right long-term solution here.



So my best recorded lap for the weekend was a 1:47.8, which is about a second faster than my best from last year. I say recorded lap because I was having trouble with the DL1, and it didn't record about half of my sessions. I really need to either install this thing properly (use the remote input connectors to put a 'logging enable' switch and light on the dash) or convert to something else.

One thing I learned from looking at the data, though, is that my wussing out and lifting after the bridge is costing me tons of time. The fast lap I held the throttle a bit longer and it was over a second faster than another one I compared it to. Something to work on for next time.

--Ian

codrus

[deleted double post]

patsmx5

iTrader: (16)

I ran 1/4" fuel injection hose with hose clamps for my external gate, and put about 2' of fire sleeve over the hose where it's close to the exhaust parts. Worked perfect for years.

codrus

The silicone vacuum hose itself seems to be fine, it's just the mechanism for securing it to the EWG that's the problem.

--Ian

aidandj

iTrader: (5)

If only someone you knew made an affordable easy to use GPS solution

EO2K

iTrader: (37)

I'm glad I'm not the only one