Probably dumb coolant reroute with turbo
 

I have a 94 and I wanted a reroute that is cheap and uses the water port at the back of the head for turbo cooling. I've been reading and trying to understand all this. So tell me how dumb the below idea is.

So this is like the Miata Mike reroute where you move the neck and thermostat from the front to the back and put the one from the back on the front. You can keep the coolant temp sensor in the back via the port that's capped with a bolt normally and then use that bolt in the front to cap the hole left by the old sensor location. But instead of routing the heater core line from the front, you cap that and have it feed from the turbo outlet. The heater core return is normal and goes back to the mixing manifold.

https://cimg3.ibsrv.net/gimg/www.mia...3227f0908a.jpg90-95 reroute with turbo
So:

Does this work ok when the tstat is closed, is there enough flow?

Does the heater still work, is there enough flow from the turbo to deal with it? (I'm in Texas so optimum heating is not required).

With engine off, will the natural flow help the turbo cool down?

Here is some good reading

https://www.miataturbo.net/engine-pe...reroute-94127/

I've read it and that one does look nice but I don't see any need to spend $250. I'd rather just buy the hose that goes from the back to the rad inlet plus the fittings and line needed for the turbo which i'd be buying anyway.

Assuming it will work and the flow is ok in various scenarios.

The normal problems the mtuned/supermiata/begi reroutes address is cleaner routing plus getting around the egr pipe and coil pack. I didn't mention that I have a non-standard egr pipe already and COPs are in the works.

Excuse me if this was posted here but here's what google found: https://forum.miata.net/vb/showthread.php?t=548423

I'm aware of the regular reroute kits. I'm asking about my diagram above. Is there any problem with having the turbo outlet back to the heater core?

You need to have the water return to the mix manifold, as it is both a low point and serves to draw water through the turbo. The fitting you need for the water port on the block is a M12x1.25 to 6AN adapter. For the return, you could drill and tap a hole to 3/8" NPT and put an adapter from that thread to AN6. This type of system will work regardless of how you do a reroute, and will prove to more durable than running silicone lines or something else to the turbo.

OK that's what I was afraid of. I mean the heater core outlet gets the water back to the mixing manifold eventually but i guess that's too long a route and the core itself is too much of a restriction?

I can go the normal way and drop it from the turbo to the inlet that normally comes from the water neck at the front (the hose that goes by the belts). I was hoping to avoid that long hose from the front neck back to the heater core inlet.

The easiest way to run the water lines is the way the FMII kit and many others do, and that is intercepting the 5/16" hose from the front water neck to the mix manifold. Due to the heat of the turbo however, it isn't really advisable to run a rubber hose directly off a banjo on the turbo, which is why many people run short AN lines to get away from the turbo with hose barbs on the end. I am not a huge fan of this solution as it introduces more points of failure to the cooling system.

If you are doing a reroute you might as well delete the front water neck, and run the coolant hose from the throttle body outlet directly into the mixing manifold bard. Or, as I mentioned earlier you could intercept it for the traditional water routing. Overall, I am more a fan of using the water port on the block and then adding an AN fitting to the mix manifold, as it will be much cleaner and more durable with appropriate fire sleeve used on the lines.

I don't see a problem with it.

Makes sense, thank you. :likecat: Now that I look at it, what you're saying is exactly how Mazda did the MSM turbo coolant lines as well. (Input from back of the head, return to a fitting in the mixing manifold.)

I guess another downside of the MiataMike/MiataKing style reroute is having the heater core feed from the front. This likely decreases overall flow through the block. His version definitely works (proven over years) but you may be giving up some effectiveness. I saw a video from LucaCarMods where he did the same thing and got good temp decreases. But the other thing I worried about with that reroute version is the only flow past the thermostat when it's closed is the little line to the oil cooler. The spacer versions always have a port for the heater core.

I do like the idea of AN lines all the way. I have power steering though and I'm not looking forward to wrestling out the mixing manifold to tap it. I did a timing belt and water pump replacement recently so I don't have the "well, while i'm in there" excuse. :)

This is what I did on my 1.6
https://cimg3.ibsrv.net/gimg/www.mia...9437a4acb2.jpg

Heater core to the turbo, turbo to mixing manifold. I did not use the block water port. I do not have the front water neck. I am using Bandits billet water pump adapter which has a 3/8" NPTF so you can use an off the shelf Meziere water pump fitting to adapt to 6 AN off the turbo.

I would go with the Qmax/Supermiata reroute personally, it's the best designed kit out there. And as you mentioned it has the provision for the heater core, so proper flow is maintained even with the thermostat shut. If cost is a factor then there are certainly other options out there.

The fittings and lines to run from the water port to the turbo, and then back to the mix manifold should run about $100 depending on what brand you decide to go with. Add some fire sleeve and they should last forever, and be easy to disconnect if you need to service things. Yeah the time to mess with the water neck is and mixing manifold is definitely when you have all the timing gear and water pump off. Kind of a PITA otherwise.

Awesome photo, thank you. That water pump adapter is nice, had not run across that before. I couldn't quite tell, does this replace the mixing manifold completely? That's another problem i need to deal with, the lower rad hose being in the way of my preferred intercooler piping.

Sweet. Ok maybe I'll have to give it a shot. For science.

It replaces the mixing manifold completely. Check out the thread I linked, it has photos of the way its now routed and what hose is required. The hose can be found at your local auto parts store. In my setup, I found it gave me more room to work. I have other photos of it I can post if you are interested if the other thread doesn't show what you need.

Oh wow, it's been a year? Ok well I finally got around to doing this. I've posted a video on the process. I don't know how well it works yet, I'll post results here after I get my downpipe made and the car is running.

Follow-up: It works!

This was super cheap and seems to work exactly the same as a regular reroute. I can detect no problems with flow through the turbo and the heater core. The heater blows the same temps as before. It's now acting as an extra radiator for the turbo.

Another plus is everything is really clean in the engine bay -- there's the new upper radiator hose assembly on the intake side but other than that everything looks OEM designed. Everything is tidy and compact.

Do you get water boiling in the turbo after shutdown with this setup? From my understanding, thermal siphoning should work well with your setup.

No boiling that I can detect, I think I am getting some siphoning effect. I have the CHRA clocked with a tiny angle (<5 degrees) with the outlet side higher than the inlet for this reason. It can then fall from there as the coolant cools down.

Just for future reference, here's the materials list:

Reroute:
Gasket maker - $7
Front thermo housing (reused)
thermostat (reused)
Gates 21864 (back of head to pipe) - $9
1.25" steel pipe - $5
Gates 22382 pipe to upper radiator - $8
Block off plate (1/4 inch) for front water neck - free or like $3
Couple of extra hose clamps - $2

If doing the full turbo route like me you can fix up the water lines on that side. I went for AN lines and fittings. I don't have an exact cost but I got all the below plus the oil lines (10 AN) for $110.
Block to -6an fitting/male AN side 12mm x 1.25
90 degree female hose end
6an braided steel line - need 12-18 inches for this side
6an to turbo banjo bolt (inlet)
turbo water outlet to 6an male
6an straight female hose end
6an steel braided hose (12-18 more inches)
6an female hose end
6an to 10an adapter fitting
10an to 5/8" hose barb
Miata heater core hose (cut and reused)

Also bleeding was exactly the same as normal. I usually raise the front of the car pretty high, fill it, wait for bubbles, fill some more, fill the overflow tank.