Old FM turbo kit low engine compression
 

Hi, everyone I recently purchased a 1991 Miata with what looks to be an old Flyin Miata turbo kit from 2007 with intercooler, wideband, boost gauge, IAT before and after intercooler and exhaust gas temperature with fuel management being a linkmiata piggyback that appears to be older than I am and the display no longer works. It looked to have been done reasonably correctly and taken care of til it was sold in 2016 and then not so well taken care of. I got it very cheap and while the turbo seems to still be good the engine doesn't look as lucky.

Compression test shows 170 120 165 170. Even if my compression tester is off by a few PSI the difference between cylinders is too high. There is significant blow by and some oil smoke out the tail pipe. The car has 130k miles and that seems correct from receipts. Given the difference between cylinders it looks like possible damage rather than just wear on the rings over time. I am also leaning towards damage because while the AFR's seem to stay in the low 12's under boost the boost gauge is reading weird. It reads 8 psi under boost briefly peaking at 8.5-8.7 before the waste gait fully opens. The problem is that with the car off it reads -3 PSI and when at idle reads -18 PSI. This leads me to suspect that the gauge or sensor is bad and I'm actually making 11 lbs of boost.

I was hoping I could say my current plan and someone could correct me where I am wrong. Assuming the pistons are good I would like to buy some ebay rods, rob bearings, HG, and rings and do a mild rebuild on the engine and then just enjoy it. I may decide to increase the power at some point but I'd have to figure out the turbo/look at compressor curves/etc. and right now I just want a reliable car I play with or take to the track once in a blue moon.

If the pistons/cylinder walls are bad I would probably just buy a used engine and swap it in and I found one on FB for 450. I also plan to do trans, diff and brake fluid and just generally make sure everything else works well. Does this sound reasonable and am I missing something really obvious? Thank you

It's not unreasonable to think that after 13 years of turbo life, the engine is worn out.

Do a rebuild, if cyl walls and rest are good, just hone, new bearings, rings, stronger rods, and all oem gaskets and call it a day.

Exactly what I did on my build.

Well , I have finally gotten around to taking the engine apart. I think this thread is going to end up being a build thread combined with me asking a bunch of questions. Idk if this is the right subforum so if not feel free to have a mod move it.

So, here's the update:

I took the engine out, it has an aftermarket clutch that looks good. The engine looks to have been apart before as the front shroud behind the cam gears was installed wrong and the amount of gasket maker used was obscene. This includes gasket maker for a front main seal. O.o

The good news is there's no wear on the cylinder walls and the cross hatching looks mint. And the pistons look to have avoided detonation and are in good shape.

There were a few weird things. A cotter pin in the pick up for the oil pump as you can see in a Pic below. Is that a thing? Also, the oil pick up filter appeared to have a few links broke.

The plan is to use new rings and bearings, get forged eBay rods, clean up the engine and use new gaskets.

I have several questions:

Is the cotter pin in the oil pick up a thing?
Do I need to hone with the cross hatch so perfect?
Do I need to balance ebay rods?
I can just use plastigauge for the bearings right?
https://cimg4.ibsrv.net/gimg/www.mia...d2bc5a47d4.jpg
https://cimg8.ibsrv.net/gimg/www.mia...fa5edc88a0.jpg
https://cimg4.ibsrv.net/gimg/www.mia...01dd463a60.jpg
https://cimg4.ibsrv.net/gimg/www.mia...0973bd9054.jpg
https://cimg1.ibsrv.net/gimg/www.mia...bc2762e957.jpg
https://cimg8.ibsrv.net/gimg/www.mia...f9436e638c.jpg

Maybe a burnt exhaust valve from a clogged injector.

Looks like I celebrated too soon. Looks like the pistons are shot.
https://cimg7.ibsrv.net/gimg/www.mia...834dcb8e08.jpg
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So I will just get a used engine and toss it in while I decide on pistons or whatever for this engine.

I will also have to decide what to do as far as engine management goes because the cars running an old piggy back that's not really supported anymore and the tune is clearly not good.

I have an mspnp3 available if you need management