Upgrades and Redux for US chassis #155

[SeanW]

Apr 24, 2018 0:48:31 GMT bornwild said:

Awesome work mate. The little nut that you put in place of the oil pressure sender - do you have a link to it? I was going to use a sandwich plate at the filter location but this seems better.

It’s an oil-cube by Acutiy.

acuityinstruments.com/products/bspt-to-npt-oil-cube

I like it but, honestly, it’s pain in the ass to install and work on without removing the intake manifold. If I were going to do it again, I’d just use a sandwich plate.

[SeanW]

One of the things that I’ve neglected for a long time has been exhaust hangers. For the most part my exhaust has been held to the car by a the single hanger off the rear sub-frame. Less than ideal to say the least.

Fortunately I found that Pypes makes a perfect hanger mount for the Exocet!

Installation is crazy simple. Lined everything up, drilled the frame tubes to 7/16th for M8 nutserts.

[garman]

Seriously, that looks like the perfect solution. Nice find.

[SeanW]

Another month, time for some updates.

First, on the exhaust front, mine broke. A lot. The tubing of the Yonaka exhaust I’d been running on the car started to crack around the exhaust hangers. No bueno. To get me through the week I welded the snot out of the hangers and the cracks but needed to do something...more. It’s at this point that I decided to replace the majority of the tubing (including the cracked sections) with a $26 Thrush glass pack muffler.



The glass pack replaces the tube’s original small resonator. (Sounds pretty nice, takes some of the raspy edge off the exhaust note.)



Once I had it all fit and welded up I nailed with a few coats of high temp flat black paint to hide my crimes.

[SeanW]

Since I’ve got a track day and some dyno time coming up soon, I figured I really needed to get the clutch changed out. Ran into a lot of “Previous Owner Sins” while myself and a friend were doing the deed. In particular, the bell housing bolts were WAY over torqued.

While I had the transmission out of the car I took care of replacing the rear main seal and the input and output shaft seals on the transmission. They looked good at the time but now I know for sure that they’re going to be just fine.



The old clutch was toast. Massive scored ring around the edge of the disc, material worn down almost to the rivets. The flywheel showed signs of slipping and excessive heating. When we pulled the pressure plate and friction disc off the pilot bearing literally fell out of the flywheel. No bueno! (We replaced the flywheel with a fresh 11 lbs flywheel sourced from eBay.)

The clutch that went into the car is a Competition Clutch Stage 3 setup. It uses a sprung 8-button sintered friction disc and heavy duty pressure plate. Competition Clutch isn’t particularly straight forward about how much power it will hold, claiming only “150%” over an OE clutch which would put it in the range of 275 lb/ft on a Miata. I get the feeling it likely would hold a fair bit more than that.

For maximum freshness I also replaced the [over torqued] OEM flywheel bolts with ARP flywheel bolts. Smart me did a little reading beforehand and found that on a 1.8 you need to use a high temp thread sealant on the the flywheel bolts to keep from leaking oil all over the pretty friction surface of the flywheel and clutch.




The clutch feels great! No more heavy than the Exedy clutch it replaces but it bites much harder. That surprised me a bit an I stalled it a couple of times while getting used to it. Engagement is much more abrupt, you have to feed the car a bit more gas but not much. It’s not hard chirp the tires taking off from a stop, something I could never get the old clutch to do because, well, slipping.

Can’t wait to get the clutch broken in and then start beating on it like a drum.

[SeanW]

Been a bit, for the most part the car has sat in the garage pending other work but I did enough miles onto the clutch to make my session on the dyno successful.

The care was running quite nicely before getting tuned, most of what was done was fine tuning of the fuel and boost maps, tuning the car for drivability. The tune’s on the conservative side of thing, pushing 12psi. It’s a stock bottom and top end, after all. (Please note that the numbers that it puts out on the dyno aren’t really what’s important to me, the power under the curve is where it’s at. And Dynapack dyno are called Heart Breakers for a reason.)



The end result, as measured on the Dynapack, was 208HP @ 6300 RPM and 197 lb/ft @ 4600 RPM. But the big news here is that my tuner was able to pick up 10HP and 12 ft/lb across the range and the part throttle tuning that’s been made SO much better.



There’s an annoying dip in power around 3500 (that I can’t feel from the driver’s seat) caused by a lack of resolution in the boost duty table. Only way to make that better is to go to a boost controller that has more columns.



Boost control, though, was the area I waving the most problems. I’d manage to mostly get it tamed so that it wouldn’t spike but would still creep a little. Now it’s a whole lot better behaved, holding a pretty solid 11.8-12PSI all the way to red line.

It’s enough to make me grin.

[SeanW]

CARNAGE!

While tearing it up on some local back-roads one of my rear fender mounts failed and jammed the fender between the wheel and the frame. No real damage done other than to the fender and the mounts, thankfully.

The fender mounts sold by Exomotive just suck.



Thankfully I was able to pull it off and limp the car back home. (Where I pulled all of the fenders off.). This actually happened before my dyno day.

The point of failure is this:



Had Exomotive used angle steel for the mounting plate this fatigue fracture might not have happened.

[SeanW]

Fortunately I had some replacement mounts ready to be assembled and installed to replace the way too flexible Exomotive solution.

I don’t have good photos of the build/assembly process but they’ve quite a bit better.

[SeanW]

While I was talking to the tuner who dialed in my fuel, spark, and boost maps we got to subject of cable bracing for big wings. I mentioned that I needed to remake my cables, shared an interesting pro-tip with me that made me realize I was way overthinking my solution.

On his time attack S2000 they just use really long zip-ties to brace their wing. It’s easy to get the correct tension, practically impossible to over-tension with zip ties, they’re strong enough to keep the wing mounts square to the body. They’re easy to cut and replace if you need to. Added bonus, the zip-ties have a slight give to them so that sudden changes in direction won’t stretch the cables, basically damping big bumps that could damage the cables.

Suddenly I went from this complex construction of cables, cable stops, threaded cable ends and tensioning nuts to just two equal length 1/16th inch cables with thimble loops on either end zip-tied to eyebolts mounted to the chassis and the wing mounts. Works crazy well!

For the record, I’m using stainless steel M8 eyebolts and eyenuts to actually affix the cables to the chassis and wing with zip ties.

[SeanW]

A few more photos of the fender mounts and the trashed but still functional fenders that I remounted.

These are part of the rear mounts, front side of the wheel.



These are part of the rear mounts, back side of the wheel.



Drilling the mounts for the fenders once they’re on the car and I can figure out exactly where the fenders are going to sit. I’ve become very pleased with the functionality chalk markers for working with metal, green in this case.



While I’ve got a new set of aluminum fenders that I could use, I wasn’t really feeling very up to working with them this weekend so I used the old fenders to make sure that my screws and bolts were going to line up where I want them. And while I was at it I scribbled all over the fenders, for reasons.



Last, photo of the car back on the ground and fully fendered once again.

[buildercg]

Sorry to hear about the issue with the fenders; glad you made it home in almost once piece. I also have noticed my Exomotive supplied fenders need improvement (especially the rears). Do you mind sharing pics of how you mounted the new front mounts? Did you keep the Exomotive "ring around the hub" or fabricate something complete else?

[SeanW]

Jun 21, 2018 0:32:01 GMT buildercg said:

Sorry to hear about the issue with the fenders; glad you made it home in almost once piece. I also have noticed my Exomotive supplied fenders need improvement (especially the rears). Do you mind sharing pics of how you mounted the new front mounts? Did you keep the Exomotive "ring around the hub" or fabricate something complete else?

For the sake of getting it done fast, I recycle the ring mounts for the front hubs. I just cut the bar off and smoothed the plate out with an angle grinder, then welded my new mounts on. Unfortunately I don’t have a lot of photos of them during the build process and the ones I did take aren’t that great. I’ll see if I can snap better ones in the morning.

I put a serious amount of consideration into further modifying the front hub rings, cutting them apart so that they’re only crescents with two bolts holding them on, allowing them to be removed without having to take the whole front hub apart. I’ve quickly sketched up what I think that would look like from memory.

The green lines are where I would cut the circular mount. (Or however it would be that would let me have two bolts and an open side on the ring.)

[SeanW]

Quickie from last night, replaced the shagged lower front ball joints on the car. They were “alright” when I built the car up but they were old, wasn’t too surprised to see that the boots had split and were starting to squirt grease everywhere.



Replacement is fast on these, thankfully.

Tools needed:
17,19,21mm sockets
17,19mm open-end wrenches
Breaker bar (helpful)
Hammer
Harbor Freight scissor type ball joint separator
Needle nose pliers

I sourced a set of OEM Mazda ball joints for the project for $75 each. You can get them after-market/refurbished for as low as $20 each but I’ve never had great longevity with refurbished parts and the OEM ball joints on the car lasted 20 years before the boots split so...

[buildercg]

Jun 21, 2018 3:30:04 GMT SeanW said:

Jun 21, 2018 0:32:01 GMT buildercg said:

Sorry to hear about the issue with the fenders; glad you made it home in almost once piece. I also have noticed my Exomotive supplied fenders need improvement (especially the rears). Do you mind sharing pics of how you mounted the new front mounts? Did you keep the Exomotive "ring around the hub" or fabricate something complete else?

For the sake of getting it done fast, I recycle the ring mounts for the front hubs. I just cut the bar off and smoothed the plate out with an angle grinder, then welded my new mounts on. Unfortunately I don’t have a lot of photos of them during the build process and the ones I did take aren’t that great. I’ll see if I can snap better ones in the morning.

I put a serious amount of consideration into further modifying the front hub rings, cutting them apart so that they’re only crescents with two bolts holding them on, allowing them to be removed without having to take the whole front hub apart. I’ve quickly sketched up what I think that would look like from memory.

The green lines are where I would cut the circular mount. (Or however it would be that would let me have two bolts and an open side on the ring.)

Thanks for the info.

I cut mine as a crescent which keeps all three of the bolts and still slips around the hub so that it can be installed and removed as needed without doing anything other than taking off the tire. It's a bit cumbersome as you need small fingers (like mine) to get the bolts into place but it works.

[SeanW]

Seeing a couple of instances where other turbo BP powered Exocets that have been driven hard on the track caused some issues/melting of the stoppy-bits in the engine bay, I decided that it would be worth while to build a heat shield to deflect the direct radiant energy from the turbo.



Very simple project, the sheet of aluminum used cost like $30 at OSH and I’ve got a reasonable amount left over after the projects. (It was a 12” x 18” sheet, 0.025 thickness). Used the lid of a cardboard box (I have so many) to mock it up, then transferred the dimensions to the sheet aluminum that I’d covered in blue painter’s tape to make marking/cutting easier. Cut everything up with a pair of aircraft tin-ships, then bent everything into shape with a spare piece of angle iron and couple of vice grips to act as a bending brake. Along the bottom edge of the head shield I’ve folded the metal in with a one-inch lip and riveted the overlaps to give the structure some rigidity.

After getting it shaped and test fitted, I wiped the whole thing down with acetone before applying strips of gold foil tape for a little extra reflectivity.



I decided the best/easiest way to mount it to the car would be to affix it to the proportioning valve. Should be good enough to project everything from direct radiant heat coming off the downpipe outlet which is the only portion of my turbo that’s not wrapped DEI header wrap or covered by a turbo blanket. If I need to extend it, I can easily rivet an extension onto it.