Bugeye Sprite, Version 3

I’ve owned this car for nearly four decades. I used to run a Datsun engine (L18), 5-speed, and R160 rear in it, mostly as an auto-X’er and Friday night toy. Then about ten years ago I got interested in rotaries, yanked the Datsun gear out, started a 13b swap, then got distracted by the day job, parked the car for years, and did a bunch of other life stuff. I’m back putzing on it now, but with a big change in direction. Sold the rotary and have now dropped a 2.4-liter LE5 Ecotec and AR5 tranny in the car. Am going with a simple turbo system because one can never have too much horsepower in a tiny little car. Am also re-doing the entire rear suspension at the same time as the engine swap, going with a Mazda rear with LSD out of an NB car. After years away from this thing I’m back to being reinvigorated and making a lot of progress… but with A LOT more to do to get it back on the road.

Oh, and yes, before anyone asks, the engine does clear the bonnet--but only because of a minor mod or two I previously made to it...

Yessss! I'm so glad to see you back at it. 

Are your rear upper A-arms longer then the lower? 

Looks great, as the owner/builder of a 13B tube frame midget I'm fully onboard this project.

nocones said:

Are your rear upper A-arms longer then the lower? 

Looks great, as the owner/builder of a 13B tube frame midget I'm fully onboard this project.

No, that's an optical illusion of the way I shot that photo. The uppers are slightly shorter than the lowers.

Fantastic, really looking forward to following along.

This is gonna be fun to watch. 

Still some welding to complete to tie it all into the central tube frame better, and I have no idea what springs and shocks (nor how to tie in the upper mounts) yet, but we did get the diff trial fitted and the car back down on its tires so it's at least roll-able again. 

Someone asked me about the AR5 tranny and how it fit. Main thing I'm currently concerned with it about is the shifter, which is way back far in the car and will need to be somehow relocated up to a usable location. I'm open to ideas...

Here she is on all four wheels again for the first time in a while. Only about 1E+6 more steps to go to get it driving... :-p

subscibed!

So, as a man with recent catastrophic diff destruction in miatas, care to go through your moun strategies? I see tig weld bushing delete,  and unboxed batwings.

Here is what I did on my shifter.  This has been great for 20 track days and about 6 years.  I have brass bushings from the hardwares store in the pivots.   The remote shifter is just attached to a rod end on the bottom.  There is a bushing on the side that a rigid linkage attaches to.  The linkage is just a linkage that replicates the motions of the shifter back to the stub of the OEM shifter (from an RX7 transmission).   The stub has a second bushing.   The remote shifter atachement is about 25% higher then the OEM shifter so the translation is shorter.  Select takes the same amount of rotation.

Hey, another RWD Ecotec swap! I'll be following with great interest.

That looks like a Solstice AR5. If you can find a 2WD Colorado AR5, it has a shorter tailhousing that locates the shifter farther forward. I'm not sure how much, I think it's a few inches.

In reply to nocones :

Exactly what I was going to suggest.  Did similar with Susie.

In reply to BadBug :

Someone asking how the trans fit may have had the original tunnel in mind, into which it would not fit....

Dusterbd13-michael said:

So, as a man with recent catastrophic diff destruction in miatas, care to go through your moun strategies? I see tig weld bushing delete,  and unboxed batwings.

I'm curious to learn more about your diff issues. For mine, the welded-in bushing locations are how the diff came when I bought it. To be perfectly honest, I knew little about Miata diffs when I purchased it from a craigslist seller, and actually thought this was normal for these rear ends. I know differently now. Oh, and I'm not sure what "unboxed batwings" mean. Can you elaborate? If I can avoid some common breakage problems now (during fab) I'd like to incorporate solutions. Cheers!

Most of mine came from wheelhop we think. Avoid it at all costs. Also, the front of the diff moving around gets ugly quick as well. Thats what killed my last one. Hence why i was asking what you're doing on yours. 

You can see on this picture how we boxed in the mounting arms on the diff. all four sides are done. This adds a bunch of strength. 

We’re taking a break from working on the rear suspension to jump up front and play with steering. First problem was an interference issue with the alternator. Solution: relocate the alternator down lower on the engine. This is a trial fit, but it seems like it’s going to work. 

Have to (obviously) build a proper mounting bracket. Plan is to chuck the original big tensioner (shown here) and use a smaller belt tensioner from an LS that was lying around. Still don’t fully known what it’s going to end up looking like…

Here’s why the alternator had to drop. We looked at a number of options for routing the steering, but this is cleanest solution that minimizes U-joints.

Also built a simple sheet metal bracket to temporarily hang the steering wheel inside the cockpit in different heights. Spent a lot of time sitting in the seat and playing with different configurations… and making zoom-zoom sounds while I pretended the car was finished.

Tied into the whole alternator and steering solution mix is the exhaust and intake side of things. There’s surprisingly a lot of room for an intercooler. There is, however, unsurprisingly little room for the intake manifold. Yes, we’re getting ahead of ourselves, but with a project like this we have to think many steps ahead lest we box ourselves into a corner. Plus it's fun to see glamour pieces like ICs trial fitted...

Waiting on D-shafts and U-joints to show up for the firewall-forward side of things, but inside the cockpit we got the steering wheel itself mounted. 

Making progress on the alternator relocation. Moving the alternator was the easy part. Coming up with a relocated tensioner system was surprisingly challenging. Still have space back the idler wheel to align with the belt, but basically we can mark this task (almost) done.

And this bad-boy showed up from Summit Racing this morning, too. Frostbite FB600 intercooler.

Nice, nice, nice. 

Made some progress on the intercooler mounting. I'm pretty impressed with the Frostbite unit. Was only $159 from Summit Racing and seems to be made well. It also fits nearly perfectly in the car.

Finally, here's a view showing how the IC will be fed air. The old scoop I built to serve an oil cooler on the previous engine is nearly perfectly aligned with the intercooler. I also have room behind the IC for a small puller fan if need be.

Nice work!

I had this car saved as my background when you had the Datsun engine. Loved it then, love it now.