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Thanks for those measurements. I've taken foxk56's steering rack model and put it into my CAD assembly to mock up some of the steering geometry. This forced a change in lower wishbone design to make room for the tie rod. I was in full-delusion mode for a while: "Oh, everyone has a problem packaging the tie rod with the lower wishbone. Mine will be different and I won't have that problem."

In other news, I got some extra money and ordered springs, shocks and a new driveshaft. My front and rear wheel rates are completely different, but because of installation geometry, the spring rates end up exactly the same: 350lbs. We'll see if those actually work; if they don't, I don't feel too bad about just buying new springs to make adjustments. I bought the springs shocks (QA1 Proma Stars) from Autofab Race Parts, which I believe others have recommended in this forum. Super helpful and knoweldgeable, and competitively priced.

The driveshaft from the Miata was shot: the differential was only held on by one of its "ears", so the driveline was rattling around and hitting the PPF and wearing a bunch. I also cut it too short when I was mocking things up. So it was probably best to just get a new one. I called up Power Train Industries, who makes all the aftermarket driveshafts for Miatas, and a lot of other vehicles. They asked for a flange-to-seal length (23.75" for me) and confirmed the slipshaft and flange design and I had it at my door in 3 days!

No pictures, unfortunately.

Holy cow. It's been a while! I've been busy with other home-making projects. I made some benches for a camping trip with some friends. They're made out of 1.25"x1.25"x1/8" angle and two 2"x6" boards. Let's just say that without the benches, the camping would've been much less fun and enjoyable!

I've also made some upgrades to my tool arsenal. A coworker was selling his 60-gallon air compressor, so I picked that up in my wife's wagon (who needs a pick-up truck?). It fit with a couple inches to spare. I also picked up a 40", 8-drawer Craftsman top chest for tool storage. I'm pretty pleased with the additional storage capacity.

I'm slowly working on getting suspension components made so I can get a roller soon. I should have some good progress made tomorrow.

Also: Oregon SAE asked me to give a talk about what I've done so far on the project. It should be fun to report out on the car.

Matt,
You did a very good job with the presentation at the SAE meeting in Portland today. With my own "no time to begin a build" life, it was nice to see in-person how things are going with your build. Everything looked very nicely done.

I'm sending you a PM.

Dean

Thanks Dean! I had a lot of fun presenting it.

Oregon SAE invited me to talk about my current progress with the car. On dollies, we rolled it onto a trailer and brought it to Elmer's for the talk. It went well. Certainly fun to present something and look back at the progress made so far. Very inspiring and motivating to keep working on it.

Evan got some pictures of the event:

No way! Matt actually did something on his car recently! I got a chance to measure up the space for my fuel tank thanks to my now clean garage. I transferred these dimensions to CAD and now have a fuel tank drawing!

Attached are the 2D drawings in a zipped-PDF. Not figured out yet are: fuel filler neck and mounting.

Here are some things I've been pondering:

1. Do I need baffles? Is foam better/easier?
2. The bottom is a point: I can flatten that out just a little bit to give the fuel sock something to rest against, but should I?
3. I'm planning on using/adapting the Miata's fuel sender/pump assembly for my height. Is this wise?
4. If not #3, what is the best/easiest/nicest/whatever fuel pump setup? Internal? External?

What else do I need to consider for my fuel tank?

Depends on the goal. Baffles keep the fuel from sloshing around when cornering. Foam - real fuel-cell foam - prevents the fuel from being vaporized into an explosive mixture when a car rear-ends you. It slightly slows sloshing but does not prevent it - I know because I experienced slosh with a true fuel-cell.

Your choice as to which of the above is more important...

Foam also has the unpleasant tendency to degrade over time, turning the fuel tank into it a maintenance item. While I have seen manufacturer claims of foam life as high as 10 years, most racers replace the stuff after two or three. When it goes bad, it tends to break down and clog the fuel system.

Personally I wouldn't use foam because it will turn bad eventually. I would personally angle the bottom of the tank to the middle and have the pick-up there. Otherwise you could always have a surge tank and a lift pump before the EFI pump? thats the best solution, but its twice as complicated pump and plumbing wise

Alright. I'll take my chances with no foam. Not only does it degrade, but it's way expensive, too! I'll see if there's a good way to draw some baffles in--I'll probably just shear some triangles or whatnot around the fuel pickup.

Speaking of pickup. Guess what's exactly the same height as my fuel tank? That's right! The Miata fuel pump and level sender assembly! I got so lucky.

EDIT: Added pictures of the cardboard mockup. It's a little bigger than it will be finished, because the cardboard folded on the inside, and that's the true dimension. I figure another 3/8" (10mm) clearance when made from aluminum. The fuel pickup fits beautifully. The sender swings perpendicular to the tank, so I'll have to figure out a way to get that mounted in a suitable orientation. Probably with screws and some rubber washers into the tank--unless I find another nice sender unit.

Wow, that looks like a big tank! Any idea the capacity?

With it's very wide size, I'd certainly put about a pair of baffles in it. I suspect slosh in a tank like that might be noticable even off the track. At least to your ears, if not the seat of your pants. Should be trivial to add if you're building your own tank. I'd make the bottom passage very small...maybe a couple of 1/2" holes or leave the bottom corner open an inch. Vents at the top, of course.

What about forming an in-tank sump with a couple of small, shallow angled baffles near the pump pick-up? The 2nd generation Toyota MR2 has a similar small, ramp-fed cup around the fuel system pick-up and that car can be driven down to almost empty on a track; my Evo, for comparison, starts to fuel starve in hard corners at about 1/4 tank with it's more open fuel tank (and twin tanks) design. Interestingly, the MR2 shares a similar challenge to your tank design in that it has a long, narrow center mounted tank. It also has a series of baffles to limit fore-aft fuel sloshing during braking & acceleration.

Do be sure to get the fuel pick-up a close to the bottom of the tank as is practical.

I had fuel problems under heavy corner with about a 1/3 of a tank. I built a sump with hinged trap doors and position the sump about 2" lower then the bottom of the tank. I have not had any issues since adding the sump. I would suggest that if you do not plan on a sump, then design the tank with 2 baffles and add trap doors that direct flow to the center section of the tank and fuel pump pick up.
Dave W

Well, I bought the aluminum for the fuel tank and got all the pieces cut out*. I factored in all of y'all's advice. I decided not to go with foam in the tank--at least at this time. I might shove some of it in later. I redrew the tank in CAD and truncated the bottom vertex, so I now have a sump about 1" deep in the middle (with the fuel pump sock right at the bottom) and added in two baffles. That should be decent enough for whatever corners I encounter. I think the capacity is now close to 9 gallons to the top, so 8 gallons with some sort of margin at the top. Perfect for what my intentions.

*BTW: CNC shears are awesome. All my edges are within half a mm of each other--this should be pretty simple to weld up, now.

I finally found something that'll work for rubber isolators for my rear transmission mount and the front differential mount. I'm going to try and use the little "foot" that comes off the bottom of the transmission tail to mount it.

Quick questions (which could benefit from some photo illustrations to accompany):

1. That foot is threaded. Do I need a jam nut or some other locking mechanism for this bolt? It'll go through rubber isolators, so I'm not sure if bolt tension alone will hold it in place.
2. Also: Depending on the order of things (from bottom: bolt head, isolator, chassis plate, isolator, threaded transmission foot), I may have this bolt hanging below the bottom of the car's chassis. My oil pan will sit 1.5 inches lower, this bolt will be maybe 2.5ft back and 0.5" below the chassis. Is this bad, or okay? I could, quite easily, modify the foot to be shorter, which would raise up the whole thing.

Yes, you need a locking mechanism. Torquing the the bolt on a rubber washer will NOT hold. I drilled for safety wire. You could use locking tabs, locktite, etc.

-dave

I used deformed thread conical locknuts thru-out my build. Should work here too. Available in Metric and SAE sizes fom McMaster.com: