Holy thread necro batman!
Now that various winter commitments have expired I am starting work on my Miata again. Given my wedding this summer time and money are both limited, so I am only focusing on two smaller projects compared to what I've done in the past: a coolant re-route and a 2.5in ID stainless steel v-band downpipe.
The downpipe is the only part of the exhaust system I haven't completely replaced, so it's about time. A larger diameter downpipe will help improve turbo spool and top-end power, and making it out of stainless steel will help reduce under-hood temperatures. I got the needed bends and v-band fittings from amazon for less than $100 with prime shipping, winning.
My first focus though: a coolant re-route on the cheap. A little history lesson: the Miata's Engine, B6ZE, is a slight variant of the Mazda 323 GTX engine, the B6T. The B6T was an E-W engine fitting into a fwd car. In the E-W configuration there is a coolant inlet near the bottom of cylinder 1, and a coolant exit (and thermostat) near the top of cylinder 4. This provided nice uniform cooling for all the cylinders. However, when the engine was flipped N-S for the Miata, this cooling layout was no longer practical. In the stock configuration the coolant inlet is near the bottom of cylinder 1, the exit is near the top of cylinder 1, and there is an always-flowing bypass through the heater core from the top of cylinder 4 to the bottom of cylinder 1. This configuration is not ideal, but in the Miata the B6ZE was only producing 115hp, so it was sufficient.
However, when a turbocharger, racing conditions, or both, are introduced the cooling system starts to show deficiencies. So, the solution is to re-route the cooling system such that it performs as originally intended.
It's a well known concern, with many OTS kits available:
http://www.bellengineering.net/product_info.php?products_id=300
http://949racing.com/miata-coolant-reroute-system.aspx
https://www.flyinmiata.com/index.php?deptid=4532&parentid=0&stocknumber=09-60000 1990-93
But all of the OTS solutions are fairly expensive and, IMO, leave a lot to be desired. Each one introduces several, if not many, new failure points to the Miata's cooling system and cost too much damn money for what they are.
So, I didn't do a coolant re-route for a while. It was never a serious problem in Autox where the engine never really has a chance to heat-soak. Then enter the 'coolant reoute easy button': an upper radiator hose from a 2002 Cadillac Escalade fits the miata almost perfectly. Now there is a decent option to do a coolant reroute without spending an inordinate amount of money, the hose is a whopping $17. I figured 'why not?' at the very least it will open up the option of driving my Miata at a serious track day.
http://revlimiter.net/blog/2011/06/coolant-re-route-2/
Not sure if I'm going to need the second hose suggested in this thread, but it's only $10 if I do.
Now the second part of a coolant re-route is the fitting on the back of the engine's head. Most people need to buy a Kia t-stat housing because it's outlet is slightly different from a Miata's and that lets it get around the coil pack. Fortunately, I have a COP conversion, so I can just re-use a Miata t-stat housing, which I have an extra of because of the spare engine(s) I have lying around. I also have an extra heater core and thermometer fitting too. So, I set to work to turn those two extra parts into one part that would (a) house a thermostat, (b) fit on the back of my engine, and (c) have enough room to keep the coolant temperature sender in place.
The first thing I did was start to clean up the old fittings. Hooray wire wheels on bench grinders!
Then I got a little creative with the bandsaw to get the two chunks to fit together.
A little something like this...
And there is still plenty of room inside each bit for the thermostat and coolant temperature sender.
The next step will be to fine-tune their fit-up, add chamfers to improve weldability, run them through an ultrasonic cleaner, and then TIG them together. TIG welding cast aluminum can be very tricky, but I've done it before, so I am optimistic that I can get them stuck together and water-tight.
Here goes nothing!