John, You have done a truly inspiring work, both at building this car and at communicating your experience. You are operating at a rare quality level. Thank you for taking the time to share all this with us.
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| John's miata-based SV clone http://www.locostusa.com/forums/viewtopic.php?f=35&t=13510 |
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| Author: | Royce [ September 6, 2017, 4:38 pm ] |
| Post subject: | Re: John's miata-based SV clone |
Beautiful work John. |
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| Author: | Wheezer [ September 6, 2017, 4:45 pm ] |
| Post subject: | Re: John's miata-based SV clone |
JSArmstrong wrote: A truly awesome build!! Thank you for the updates John, what thickness Ali did you use to do the sump modifications? Thanks! I used 3/16" thick 6061-T6. The stock pan measured about 0.120-0.140" in most spots, so I added a little bit for safety. You lose the T6 heat treat during weld, but the aluminum is still very strong and malleable (rather than brittle) so I think it's pretty safe. I also used 4043 rod - recommended for welding to cast aluminum. I did a quick "cleaning" pass and then wire brush before performing the actual weld with filler rod. Seemed to work really well and I had no issues welding to the previously oil-soaked pan. |
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| Author: | Lonnie-S [ September 7, 2017, 9:19 pm ] |
| Post subject: | Re: John's miata-based SV clone |
I know you're not truly "finished", John, but did you put yours in the "Finished Builds" thread? It's a great example, and I think it definitely should be there as a terrific inspiration for potential builders. On-going improvements could still go here, I'd think. Cheers, |
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| Author: | Wheezer [ May 31, 2018, 11:14 pm ] |
| Post subject: | Re: John's miata-based SV clone |
Once again, it's been a really long time since I updated the build log. Last Fall I had an window in the weather to get the new engine on the dyno - I only had about 700-miles on the engine, and still had the break-in oil in the crankcase. See results below: very noticeable increase in the area under the torque curve - it adds a solid 1000-rpm of usable power - pulls harder after 4k, and the power doesn't flatten out until around 6700. I did this dyno run early because I wanted a before/after with the new manifold I was going to make over the Winter. |
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| Author: | Wheezer [ May 31, 2018, 11:24 pm ] |
| Post subject: | Re: John's miata-based SV clone |
After much design work, I committed to build a manifold from scratch using a cast aluminum base flange, with machined and welded runners and plenum. All designed to use the stock throttle body, and run on the stock ECU. I cast the base flange from scrap 6061-T6 aluminum I had from the shop using the lost wax technique. I first printed two individual port sections of the base flange, machined and siamesed them into a single model for casting. I then made a multi-core silicone rubber mold that enabled me to pour duplicate wax models and then invested those wax models in a plaster/silica investment (plaster). The wax is then melted out of the plaster investment using a wallpaper steamer, leaving a void in the investment to pour molten aluminum into. I used a home-made crucible furnace to smelt the aluminum, and it worked great! I cast two of the two-port sections and then machined and pinned them together to create the base flange of the manifold. |
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| Author: | Wheezer [ May 31, 2018, 11:28 pm ] |
| Post subject: | Re: John's miata-based SV clone |
Next I machined the runners and plenum base with trumpet inlets out of aluminum. Here you see it assembled before welding, tacked in place for fit-check in the car, and clearance under the bonnet. The runner lengths are very similar in length to what I'd have with a good IRTB setup, and the plenum is the same displacement as the engine. |
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| Author: | Wheezer [ May 31, 2018, 11:30 pm ] |
| Post subject: | Re: John's miata-based SV clone |
Here's the throttle cable bracket detail, and final assembly with cold-air intake at the firewall. |
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| Author: | Wheezer [ May 31, 2018, 11:37 pm ] |
| Post subject: | Re: John's miata-based SV clone |
I wanted to make a unique intake in the bonnet, and decided to do something similar to what I've seen Donkervoort use on some of their turbo inlets. I used my CNC router to make a forming die out of MDF to hammer-form the aluminum wire screen into. Then I made a backing ring and riveted it to the bonnet. I'm happy with how it looks and functions. The new intake has a good honk to it, and now the engine revs freely up to the 7200-rpm rev limit. I have not dyno'd it yet, but seat of the pants feels like another 5-7 hp up top, with a linear torque curve - as before it wakes up around 4000-rpm and then pulls strong all the way up. |
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| Author: | Wheezer [ May 31, 2018, 11:42 pm ] |
| Post subject: | Re: John's miata-based SV clone |
With the new intake I wanted to clean up the fuel system a bit - I made a simple fuel rail and added a better adjustable fuel pressure regulator. And with the intake at the rear of the car, I was now able to mount a larger radiator up front. I chose a scirocco style crossflow unit, and couldn't be happier. Even without proper baffling around the radiator, the intake temps are stable and right at 193°F - exactly what the thermostat is rated at. |
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| Author: | Wheezer [ May 31, 2018, 11:49 pm ] |
| Post subject: | Re: John's miata-based SV clone |
I ended up having to replace the front main seal on the crank due to some freak issue with a brand new seal that started leaking like crazy. As long as I had the timing belt off, I decided to install a cheap set of adjustable cam gears that a friend had given me years ago. Honestly, I should have just installed these when I built the motor... I haven't played with them yet, but I'm thinking I might be able to move the power down a little bit lower by advancing them some, and perhaps even find a bit more power from the stock cams by playing with overlap. With how well the engine is running on the stock ECU, I'm curious if I can possibly hit the 150-whp mark - so far it's running very strong, and it behaves extremely well in all weather conditions - and it's been as reliable as a stock miata. |
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| Author: | phil [ June 1, 2018, 6:41 am ] |
| Post subject: | Re: John's miata-based SV clone |
John, You have done a truly inspiring work, both at building this car and at communicating your experience. You are operating at a rare quality level. Thank you for taking the time to share all this with us.
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| Author: | Lonnie-S [ June 1, 2018, 9:20 am ] |
| Post subject: | Re: John's miata-based SV clone |
Ditto phil above. Cheers, |
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| Author: | TRX [ June 1, 2018, 9:31 am ] |
| Post subject: | Re: John's miata-based SV clone |
Looking good! A question, though: You went printed pattern > silicone mold > wax cores. Was there some reason you didn't just print the cores directly with PLA, or were you just staying with the process you were most familiar with? |
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| Author: | niko [ June 1, 2018, 9:59 am ] |
| Post subject: | Re: John's miata-based SV clone |
WOW ! Any more info on the casting method ? I'd be interested to see the furnace . I have an injection burner powerful enough for forging, maybe I can make it work for this type of deal ? |
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| Author: | Wheezer [ June 1, 2018, 10:33 am ] |
| Post subject: | Re: John's miata-based SV clone |
Thanks for the compliments, guys. I'm happy to share; this forum gave me the motivation to do this project in the first place. LonnieS - I'll take your suggestion and try and get a post in the "completed build" section soon. I think this car will always be a work-in-progress, but it's finally feeling pretty well dialed in. TRX - I did lost wax because I was familiar with the process (another hobby of mine is glass casting, for art). My printer is a Form1+, and the castable resin is too expensive for big parts like these - the standard resin doesn't burn out nearly as well as PLA does (from what I've read - I've never done a PLA burnout). This was by far the most complex mold I've done, and it was fun to figure out how to do it. niko - I'll post some pictures of the furnace and burner I built soon. I'm guessing you could totally use your forge burner. Mine is a smaller copy of a T-Rex burner that I made just to see if it would work. It melts ~6-lb of aluminum in about 30-minutes from a cold start. |
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