Differential NVH Damper Delete

The NVH vibration damper on the input flange of one of my diffs has started shaking loose (a semi-common problem). Given that they’re not a critical piece, that they can be a critical failure. that they would be a royal pain to fix in the field (assuming I have access to air tools, which I typically don’t), and that I’m in the process of having them both in and out of the car before and after the hill climb, it’s time for them to go.

The piece in question is the big steel (? might be cast iron) cross sitting between the input flange and the differential housing. It’s mounted on a rubber donut bonded to the input flange.



A few minutes on the press (for the good one, the other nearly came off by asking it nicely) and it came right off. A little time on the wire wheel to knock off the excess rubber off of the flange and it’s ready to go back in.



I didn’t expect it would add up to much, but it did end up being a worthy gain (or loss, depending on how you look at it), taking 1.75 lbs of rotating mass off of the drive line. Like removing a small flywheel off the front of the differential. Success!



Trailer Winch

I absolutely adore my 6# flywheel, but it does make getting the car over the hump onto the trailer a challenge. The last couple times I had to make¬†course corrections part way up, I could smell that the clutch wasn’t happy. Since Harbor Freight had a sale going for their 2500# winch, I figured, for $50 and a bit of blood and sweat, why not?

This is my highly technical concept diagram on how I wanted to mount it. Given how short the legs are, I opted to keep both legs straight because…I had scrap pieces that were the right length ūüėČ



Here’s my starting point. I snagged a 6″ receiver tube, and since I didn’t have any 2″ tubing long enough, cut up a Harbor Freight 1 ball hitch:



The black-on-black makes it difficult to see, but here is the trailer-side mount, along with the 2″ hitch welded up to the winch mounting plate:



The trailer-side mount welded in place:



It fits with the fuel jug, but it wouldn’t take much wiggle for it to rub, so I’ll likely end up hooking the…hook… to the back side of the receiver tube.



I decided to run the winch off of the truck instead of having another battery on the trailer. It’s sort of a 6 of one, a half dozen of the other situation, but I mostly didn’t want to have another battery to buy, maintain, and maybe get stolen. Because of that, I needed a couple of small mods on the truck side. In the engine bay, the main things needed are a Circuit Breaker (just in case) to protect the truck-side wiring:



About 50′ of 4 ga battery wire, and a pair of very large Quick-Disconnectors for the rear of the truck. This shows both the truck and trailer sides hooked up while I was hunting around for somewhere to put them, and discovered a very convenient M6 bolt hole on a metal bracket that secures the bottom of the rear bumper in place. It couldn’t be more perfect. The shiny bit on the right is one of the valves for the rear helper air-springs:



After running most of the wiring for the truck (save the jumper from the battery to the circuit breaker, to keep the harness ‘cold’ so I could safely work on the wiring) it was time to work on the trailer side.

The winch comes with some pretty uninspired 10gauge wiring, so job one was replacing all of that. I’m also crimping *and* soldering all of the wire terminals. You can see the difference in size between the 4ga wire I’m running, and the stuff it comes with here.



With all of the wiring in place, I could build the jumper between the circuit breaker and battery:



And finally it was time to plug everything in and run a couple system checks. First off, everything was in fact dead with the circuit breaker tripped, which is a good sign. Next, plugging the winch into the truck didn’t let any smoke out. And last, I gave it a pull off of the 12,000 lb D-ring on the back of the trailer to make sure my welding is as extra medium as I thought it was. I still don’t have a ton of trigger time on it, and this is really the first thing I’ve fabbed up that could potentially kill or maim if it comes unmoored. So…I wanted to make DAMN sure the whole thing wouldn’t end up flying across the workshop. And it didn’t, so…win one for the good guys! Or…at least, for me.

Chasing the Dragon Hill Climb is this weekend, so it’ll get some use loading the trailer at home and after (hopefully….) the event. Also: SO EXITED! ūüėÄ

LED Tachometer Mount

The main reason I got the bling-o-meter is as a rudimentary yard stick for reviewing video of speed in a certain part of the track (or at least, RPM). More lights = more fast. Easy.

The problem is that it’s¬†nearly invisible in the video, because the steering wheel is between the tach and the camera. So how to fix it?

I noticed in the video that if it were directly behind the steering wheel on the column, it would show up perfectly, so I fabbed up a quick mount to get an idea of where it should go.


I briefly considered welding to the column housing, but after consulting with a friend who generally knows much better than I (Thanks Dave!) decided that there’s too many important unknowns that could be cooked inside the column housing (plastic bushings, grease seals, etc) to risk welding directly to it. He floated the perfect solution (as usual). Inexpensive and effective: a 2-piece shaft collar.


A little time on the wire wheel cleaned off the oxide coating on the un-threaded half, a little welding, and a coat of paint, and it should work great:


A little time spent on the little things that would bother me if they were staring me in the face before each run:




And now I should be able to get some use out of it. A little before & after:

Headlight cover bumpers

I had a little time for a quick project to correct one of the more annoying side effects of gutting most of the bumper supports: part of the bumper supports held up the leading edge of the hood, but with that gone, the already flimsy hood was even flimsier. The steel barn-door covers at the corners of the hood were causing the hood to flex, and causing the center of the hood to bow up, making a bit of a scoop, which is sub optimal.

I found a pair of rubber hood (or maybe trunk?) bumpers in 1 of my buckets o’ bolts and realized they would be about perfect for this.


These were going to be above the chassis cutouts for the turn signals, so I pulled the bumper to allow far easier access to the bottom nuts. What else are you going to do with an autocross 2 days away?


Not too many pictures of the process, but I used a pair of long M6 x 1.0 mm bolts and made up brackets that would accept the rubber bumpers. A little welding and grinding, and here’s what I ended up with. There’s another flange nut at the bottom underneath the body sheet metal, to lock everything together (along with some loctite):


And just like that, no more droopy eyeballs.


We’ll see how they work tomorrow at the autocross.

5th Gear Lockout

Sometimes I wish I’d kept more videos, but disk space ain’t free. I could put together a pretty solid compilation all the way back to the STS days of myself and my codrivers consistently missing 3rd gear and hitting 5th on faster courses. During normal driving it was never a problem, but when exiting a corner at an autocross at the top of 2nd gear, it seems like 75% of the time it just wants to go into 5th. After it still being a problem even with delrin engine¬†and differential bushings, and a delrin shifter bushing, I decided to do something about it.

I’ve seen a couple on other cars, and borrowed a ideas from just about all of them. I wanted something simple (ie: that I could make myself), something easily disabled (reverse is often needed for getting around paddock & grid), and fairly easily¬†removable.

First up was figuring out where to mount it. I played around with a couple different things and settled on having it reside between the transmission tunnel and the upper dust boot, on the passenger side, and use the 2 bolts for the dust boot along that side to secure it. A length of 1.5″ steel angle made a solid base for the lockout after a little love from the angle ginder.


A 3″ or so length of butt-hinge left over from another project gave me more than enough width to cover the full throw of the shift lever, and would allow the devise to be easily swung ‘open,’ away from the shifter.


I didn’t want the shifter ever making metal-metal contact, so I grabbed (and then sacrificed) a cheap plastic cutting board to use as the bumper for the shifter to contact.


With the height and positioning set, I could stitch the hinge to the base:


So that the bumper didn’t sit too low and contact the dust boot, I added a stop to keep it in place in the closed position. In the open position, the hinge runs out of travel and naturally stops at around 90¬į.


The thing was starting to get heavy, so the angle grinders and big drill bits came out to take some weight off. Here I’ve also added the spring retainers out of 1/8″ steel bar for a spring that will hold it steady at either end of its travel:


A coat of paint to keep the rust at bay, some final finishing on the bumper piece (it’s still completely flat throughout the full throw of the shifter), and final assembly, and it should be good to go.




I’m really happy with how it came out. It looks a lot less hacked together than a) it is, and b) I expected it to look as it was starting to come together.

Here’s a quick video made towards the end of mocking everything up, after securing the bumper in what should be its the final position. Unforunately it’s just a static test, I don’t have a way of getting the car into a position that creates the 2nd > 5th problem safely in my neighborhood, so I’m not even going to try. However, it seems to work great. There’s about 3/16″ between the shifter and its resting place in 3rd gear, and that seems to be enough to where it doesn’t try and skip 3rd and get jammed in the gate to 5th / Reverse, but also isn’t resting against the bumper. In the video, I’m also being way rougher than I ever would in reality just to make sure it doesn’t try and skip the 3rd gear gate.


I’m really pleased with how positive the action is, and how well it sits against the stops. I was worried I’d need to add a second spring (like in the example linked to earlier), but it’s nice and snug without being too hard to flip to the open position.



The 1st event we ran this at resulted in nearly worse performance. After doing some testing, it became clear that it was actually guiding the shifter into hitting the stop between 3rd and 5th.¬†To make it work, with the shifter in neutral, the lockout actually needs to push the shifter a bit¬†towards the 1 / 2 gates. It turned out that we didn’t actually need it at our last event, however we tried it out on first runs just to see, and now it’s guiding directly into 3rd under load. Success!

New Header, New Midpipe

Ever since putting in the VVT motor, my header situation has been sub-optimal. It was a Jackson Racing header (with the EGR fitting removed) which was better than stock, but it had a good bit of weld on the inside of the primaries directly in front of the ports. That big ridge is not great for flow:


I managed to work a deal on a Maxim Works (Mazdaspeed branded) NB header from JDM Land. Check out how clean the transitions from the flange to the primaries are:


After cleaning up a bit of surface scale with the wire wheel, it dropped right in. The JR basically had to be wrestled out. One more reason I like the Maxim Works better. And for what they cost new, it should be better.


Unfortunately, but also kind of fortunately, the flange and gasket type on the Maxim Works is completely different (round vs donut on the Jackson Racing), so a new cat-delete pipe had to be whipped up.

You’ll note that this is the 3rd or 4th iteration of the cat delete pipe, depending on how you’re counting. So while I dreaded the job a bit, I was also looking forward to doing it right. The exhaust hung a lot better with the last version than it did with the first version¬†(not that it was a particularly high bar to meet…), but it still scraped the cat-back portion at the top of my hill coming out of the shop, so I wanted to make triple sure that there wasn’t something else amiss.

There was something else amiss. The cat-back is a slip-fit with the axle back, and is secured by a large band clamp. Works fine, but doesn’t lend itself to repeatable installation, apparently. Because it turns out that the last time the exhaust was out (who knows how long ago that was), when I reinstalled it, I clocked the cat-back¬†incorrectly into the axle-back, and it was tweaked in a way that forced¬†everything lower than necessary.

This photo, by way of comparison, is with the new mid-pipe tacked up and bolted in place, and is taken by a lower angle (showing more of the exhaust) just so you can see some of the exhaust towards the right hand side:


That is WAY better, and should pretty well cure the scraping issue once and for all.
It also appears that I AM capable of learning from my mistakes. Instead of the pie-cut and poorly fit nonsense from before, I got it in 2 sections (with a small mandrel bend on each end, slip-fit flanges, and flared 1 of the tubes just enough that the 2 pieces were nearly a slip fit. That allowed for a bit more flexibility in fit up, and a much stronger weld (lap weld vs butt weld). And because occasionally the kids let us sleep these days, I managed to put the flare on the downstream side so it would flow more smoothly (ie: into the flare) instead of tripping over the hard edge of the downstream tube if it were flowing out of the flare.


The slip fit flanges allowed a ton of freedom when fitting everything up, to the point that both flanges had maybe 1/16″ of tubing sticking out past the flange to get the correct angles. A flap disk trued everything up nicely.


And finally, after a final test fit and a bit of grinding to clean up some booger-welds where I had to clean up after blowing through the tubing, a coat of high-heat paint to keep everything shiny.


Aero: Front Splitter

The biggest concern with making a splitter for me was that it had¬†to¬†be fairly easy to take on and off for loading and unloading, so the entire build is made with that in mind. I think I’ve accomplished that, as by releasing 2 pins and 2 dzus fasteners, the splitter can be lifted free from its mounts.

The constraints that the splitter must live in for a D Prepared car are:
It may not be further rearward than the leading edge of the front wheel opening.
It must fit below the silhouette of the car as viewed from above.

Given that, the first thing to do was measure measure measure and make a template:




Next I wanted to make a set of mounts that would do most of the work of locating the entire assembly both laterally and longitudinally. I had a fairly large length of 1/8″ Aluminum Angle, and went to town with the drill and sanding drums. The hook portion will take care of the longitudinal location, and the mounts will be placed flat against the chassis mounts to locate them laterally.


With all the ‘easy’ stuff done, I wanted to make the base of the splitter so that we could start working off of something more consistent that cardboard. The material I chose was 1/8″ Dibond, which is 2 thin sheets of Aluminum with a solid plastic core. A single sheet wouldn’t be strong enough, so I used some of the stronger 3M Double Sided tape to bond 2 sheets of Dibond together.


I spread out some steel and lead to evenly press the 2 sheets together.


After more measuring and fitting, I finally had a starting point:


Now that I had it at a reasonable height, I could start measuring out to build the chassis mounts. Once those were fixed in place, I drilled out 3/8″ holes in the mounts and welded the ‘hooks’ I made to the backs of them, so that the weld metal wouldn’t interfere with the splitter mounts.



With the rear of the splitter fixed in place, I could start making a mount for the fronts. I built it to bolt to existing holes in the bumper support. Harbor Freight actually had excellent ends for the 3mm cable I used. I used a pair of Forked Cable Ends for the chassis side, drilled out¬†to use 1/4″ quick release pins, and used a pair of Eye Terminals for the splitter side.



Finally having the splitter hung and being supported 100% by the car was a big moment for me, as the end was in sight and it finally started looking useful. I noticed however that in order to actually get my hands under the bumper and crash structure, the crash bar needed to be notched:


With all of the mounts sorted, it still felt like it had a bit more flex than I was comfortable with. I used a length of 1/2″ aluminum angle along the rear edge of the spoiler to add strength. Fortunately, I had Superman there to help with the riveting work.


For the air dam, I used 1/8″ ABS as it’s sturdy and easy to work. To join the ABS to the Dibond, I picked up some garden / paver edging from Home Depot Racing Supply. It’s nice and sturdy plastic, but also very light.


Everything got disassembled for a couple coats of paint to keep the rust at bay:



And finally, put back together to be viewed in all its majesty ūüėÄ



I think maybe she might need a wash. Before then, there’s lots more¬†work to do in the month or so before the next event.