carbon

iTrader: (1)

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.








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.



repainted and new top:









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.

carbon

iTrader: (1)

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.

adamiata

iTrader: (1)

Very cool.

Where'd you get your 1.6 head flange?

Leafy

iTrader: (1)

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 ***** feel small.

iantboyd

iTrader: (11)

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.

Leafy

iTrader: (1)

it sounds like you're in a car that isnt a miata that has vastly superior aerodynamics.

iantboyd

iTrader: (11)

Its more of a little black brick but I like the vastly superior comment.

cyotani

iTrader: (8)

People are claiming good mpg gains with an undertray/ splitter and other aero mods from the DIY aero thread.

curly

iTrader: (25)

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.

concealer404

iTrader: (3)

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.

Leafy

iTrader: (1)

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.

Efini~FC3S

iTrader: (4)

The really high spark advance for mpgs in cruising plateaus and then starts to adversely affect fuel economy if you go too far advanced

Leafy

iTrader: (1)

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.

concealer404

iTrader: (3)

5spd/4.10 combo, lean highway cruise in the 16s. The instaspool/torque of the 2554 is advantageous since lugging is not necessary to get up hills.

Efini~FC3S

iTrader: (4)

Right...spend $400+ in dyno time to pick up that last 1mpg. That'll pay off quickly.

concealer404

iTrader: (3)

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.

**** was so cash.

Leafy

iTrader: (1)

The time spent finding the gas mileage had better cost you less than $75 or you're doing it wrong. It shouldnt take more than half an hour longer over a normal make it run make power dyno session to go back and hit those cruise areas for spark.

shuiend

iTrader: (24)

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.

carbon

iTrader: (1)

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...



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.





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.



Super messy bench with new V-band turbo outlet.



Opens and closes fully.





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.







Installed clutch, and chopped off OEM water neck up front and welded it shut to use in the reroute.















Do my water routing lines look good for the reroute?

petrolmed

iTrader: (8)

It's doable, depending on your trip. On all highway trips, I get 30-33 mpg on my t25 1.6. Commuting to work every day, I average 27 with heavy footed driving and the stop and go nature of highways at peak hours