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Project: Ultimate DIY High MPG Commuter
22 Attachment(s)
This is my build thread that kind of snowballed out of control. My original plan was to just buy this "cheap" 1990 white Miata, fix it up and drive it around for a little while and sell it. The top window was ripped out, and it had a little shake to it at idle, but it ran decent and I figured it might just be injector o-rings or something simple. It was fairly rust free so it didn't seem too bad. The only rust I've found isn't more than surface rust.
https://www.miataturbo.net/attachmen...ine=1408693309 https://www.miataturbo.net/attachmen...ine=1408693309 https://www.miataturbo.net/attachmen...ine=1408693309 So I replaced the top, injector o-rings, got it repainted white. Drove it on multiple trips totaling over 1000+ miles. It was always down on power, but I figured that is just the N/A Miata life yo. I decided to finally compression test it. Turns out it had a cracked exhaust valve on cylinder #3. https://www.miataturbo.net/attachmen...ine=1408693309 repainted and new top: https://www.miataturbo.net/attachmen...ine=1408693309 https://www.miataturbo.net/attachmen...ine=1408693309 https://www.miataturbo.net/attachmen...ine=1408693309 https://www.miataturbo.net/attachmen...ine=1408693309 At this point no one really wants to deal with buying a car like that, and I wasn't having any luck selling it, so I decided to just go all in and fix it. Besides cylinder #3, it had strong compression of 180+ psi per cylinder so I figured the rings were still good. I also figured since the head is coming off, might as well just put a new head on for basically the same cost as getting a new valves etc... One thing led to another and I ended up with a plan of a $1500 budget turbo car (not counting head replacement, etc... TURBO related stuff only.) I think realistically I will come closer to $2000. I am trying to do everything myself and keep it as DIY as possible. Installed brand new head, timing belt, water pump, gaskets, new crankshaft/cam seals, viton CAS o-ring, new alternator, intake manifold gasket, stuff for coolant reroute... I've forgotten a few things but I have receipts of everything in a folder that I will be putting into my excel sheet soon to see if I stuck to the original budget. The ultimate goal for the car is a budget commuter that gets 30+ mpg. Not sure if it's doable, but I am going to try. https://www.miataturbo.net/attachmen...ine=1408693309 https://www.miataturbo.net/attachmen...ine=1408693309 https://www.miataturbo.net/attachmen...ine=1408693309 |
18 Attachment(s)
DIY Manifold:
I used to have an S14 with an sr20, did plenty of turbo swaps with it and knew the places to look for a good t25 sr20. I got a freshly rebuilt one to use. Plans for the manifold are steel head flange with 304L SS runners and turbo flange. ER312 to join the mild steel flange to the 304L elbows, and ER308 for the SS to SS welds. I used a gas lens, as well as back purging the manifold with argon while I welded. I had to get a dual flow regulator so I didn't have to buy another bottle of argon. I made a purging setup on my welding table I made. Here a some pictures. I used the GTAW (TIG) process. https://www.miataturbo.net/attachmen...ine=1408694259 https://www.miataturbo.net/attachmen...ine=1408694259 https://www.miataturbo.net/attachmen...ine=1408694259 https://www.miataturbo.net/attachmen...ine=1408694259 https://www.miataturbo.net/attachmen...ine=1408694259 https://www.miataturbo.net/attachmen...ine=1408694259 https://www.miataturbo.net/attachmen...ine=1408694259 https://www.miataturbo.net/attachmen...ine=1408694259 https://www.miataturbo.net/attachmen...ine=1408694259 |
Very cool.
Where'd you get your 1.6 head flange? |
I was expecting the first line to go along the lines of, I wanted a miata but I decided the MX3 met my goals much better.
Err, good like with your 30mpg tops commuter car. I'm waiting for concealer to come in here and talk about his 40+mpg 400hp mx6 to make your penis feel small. |
He should be able to get well into the 30's. I just pulled 29mpg in my b6t last weekend....but I has awd, 190k miles and stock(ish) engine management.
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Originally Posted by iantboyd
(Post 1159967)
He should be able to get well into the 30's. I just pulled 29mpg in my b6t last weekend....but I has awd, 190k miles and stock(ish) engine management.
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1 Attachment(s)
Its more of a little black brick but I like the vastly superior comment.
https://www.miataturbo.net/attachmen...ine=1408716890 |
People are claiming good mpg gains with an undertray/ splitter and other aero mods from the DIY aero thread.
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Just spend a few hours on the free way at a steady 55-65mph, getting those AFRs in the mid 16s, and I think really high spark numbers help for MPGs? I think Scott had a ~4x4 table of 38* IIRC. Not sure if that helps.
Just don't forget weight savings, that's also a huge help. Ditching the AC, PS, manifold brace, trimming the alternator bracket, etc. It'll all help. I think higher temps too, so keep the stock 192* thermostat. |
Originally Posted by Leafy
(Post 1159950)
I was expecting the first line to go along the lines of, I wanted a miata but I decided the MX3 met my goals much better.
Err, good like with your 30mpg tops commuter car. I'm waiting for concealer to come in here and talk about his 40+mpg 400hp mx6 to make your penis feel small. What if i told you the built motor 2554 car also hasn't recorded a mixed-driving tank lower than 32mpg since March, and has a record high so far of 35.3mpg tank, all highway? Doesn't beat the MX6, but it's still pretty easy on the wallet. :giggle: |
Originally Posted by concealer404
(Post 1159995)
What if i told you the built motor 2554 car also hasn't recorded a mixed-driving tank lower than 32mpg since March, and has a record high so far of 35.3mpg tank, all highway?
Doesn't beat the MX6, but it's still pretty easy on the wallet. :giggle: |
Originally Posted by curly
(Post 1159994)
Just spend a few hours on the free way at a steady 55-65mph, getting those AFRs in the mid 16s, and I think really high spark numbers help for MPGs? I think Scott had a ~4x4 table of 38* IIRC.
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Thats why the car should be tuned on a load varying dyno. So you can lock the car into each rpm range and keep increasing the spark advance until torque stops increasing.
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Originally Posted by Leafy
(Post 1159996)
Holds the record for a miata swap in a miata. Only one better is that 3 cylinder guy that does 55mph on the highway to get upper 40's. The car is still a brick. I get the same mileage in the city as I do on the highway.
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Originally Posted by Leafy
(Post 1159999)
Thats why the car should be tuned on a load varying dyno. So you can lock the car into each rpm range and keep increasing the spark advance until torque stops increasing.
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Originally Posted by Efini~FC3S
(Post 1160018)
Right...spend $400+ in dyno time to pick up that last 1mpg. That'll pay off quickly.
When i paid $300 for dyno time once the Haltech was installed on the MSM, the car picked up 4mpg overage everywhere vs. the Hydra w/ FM tune. A week later, we took it on an 8,000 mile road trip. Saved $175 in gas. Shit was so cash. |
Originally Posted by Efini~FC3S
(Post 1160018)
Right...spend $400+ in dyno time to pick up that last 1mpg. That'll pay off quickly.
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6 speed + 3.63 gears will help you get better mileage while cruising on the interstate. I hit around 33-34mpg in Hustlers super commuter with cruise control set between 75-90mph.
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15 Attachment(s)
Head flange is a CXracing. I had to widen the holes a bit because fitment wasn't 100% perfect. I also cut between each runner for stress relief, heat expansion, etc...
https://www.miataturbo.net/attachmen...ine=1408744311 My attack plan for 30+ MPG is 440cc Yellow RX-8 Injectors I got a super sweet deal on from a race shop I worked at. I figured I could pick up 1-2 MPG on the design over OEM type. https://www.miataturbo.net/attachmen...ine=1408744311 https://www.miataturbo.net/attachmen...ine=1408744311 I also was originally going to build my MS3x... but then Brain decides to step out of retirement right at the moment I was about to start building... His price is so fair, it's hard to pass that up. Should be getting that back from him completed soon. https://www.miataturbo.net/attachmen...ine=1408744311 Super messy bench with new V-band turbo outlet. http://i12.photobucket.com/albums/a2...ps8001c03c.jpg Opens and closes fully. https://www.miataturbo.net/attachmen...ine=1408744311 https://www.miataturbo.net/attachmen...ine=1408744311 Fitting water/oil lines for the turbo. Going with -3 AN oil feed lines with the proper restrictor for oiling the T25. Doing reroute stuff, pulling engine for 949 Clutch kit install, need to make oil return bung to clear A/C. https://www.miataturbo.net/attachmen...ine=1408744311 https://www.miataturbo.net/attachmen...ine=1408744311 https://www.miataturbo.net/attachmen...ine=1408744311 Installed clutch, and chopped off OEM water neck up front and welded it shut to use in the reroute. https://www.miataturbo.net/attachmen...ine=1408744311 https://www.miataturbo.net/attachmen...ine=1408744311 https://www.miataturbo.net/attachmen...ine=1408744311 https://www.miataturbo.net/attachmen...ine=1408744311 http://i12.photobucket.com/albums/a2...ps47e57756.jpg Attachment 184748 Attachment 184749 Do my water routing lines look good for the reroute? |
Originally Posted by carbon
(Post 1159919)
The ultimate goal for the car is a budget commuter that gets 30+ mpg. Not sure if it's doable, but I am going to try.
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