nonchalantwhale

Hey all, I recently purchased a built NB MX5 SE. It was below market price due to it blowing a bit of blue smoke. I took the risk and went through with it seeing as I've heard lots of cases with faulty valve stem seals on MX5's (supertech?). There were no receipts for the engine building but I do have a list of all alleged modifications done to it. Here are the relevant mod list that was given to me. I will also post some engine bay pictures, if anyone can list any more things done to the car that aren't listed it'd be greatly appreciated. I've also been told by my shop that it's a custom manifold done by NitroDann.

Engine fully forged and everything balanced.
Head skimmed. Double valve springs.
Haltec 1000 ECU
Injector Dynamics 1000cc injectors.
Rising rate fuel pressure regulator.
Flex Fuel Sensor
Garrett 2871 turbo at 25psi max, with water cooling. (Dyno guy said it was only running at around 14psi)
Big radiator. Coolant reroute. Baffled sump.
Custom Intercooler

I had the dyno'd at and it made 207kw/501nm (277 hp/368 lb ft) at the wheels. I had doubts the engine wasn't forged due to the lack of receipts but it seems unlikely stock rods would take this sort of torque.

So the car blows some smoke on cold start, a small puff. It's definitely blue. I will upload some videos soon. I also notice quite a bit more smoke when taking off, especially when I rev the car to take off in first or while reversing. Quite a noticeable cloud. I was told by the previous owner it was very likely valve stem seals. All the symptoms match up. However I had my shop mention it could also be the turbo giving out. When boosting I don't notice any substantial smoke behind me, I have yet to drive behind the car but nobody's pointed out anything yet. I have yet to observe the car burning much oil either. It also has a catch can.

I had a pre purchase inspection done with a compression and leakdown test with the following results:

Cylinder 1: Compression: 175 psi Leakdown: 22%
Cylinder 2: Compression: 185 psi Leakdown: 28%
Cylinder 3: Compression: 180 psi Leakdown: 20%
Cylinder 4: Compression: 180 psi Leakdown: 22%

I was told the compression is fine but leakdown is a bit high but could be explained with forged pistons. Quite consistent across the board and nothing to worry about according to the shop.

How would I go about diagnosing the issue from here? I had the top of the pistons examined via the spark plug holes and was told there's no scorching and it's all good so that should rule out piston rings. The turbo boosts in a healthy manner, check the dyno graphs for reference. From here I plan to check if there's any shaft play in the turbo, though it's a bottom mount so any advice getting to it would be greatly appreciated. Check intercooler piping for oil? Is there any possible way to surely rule out the turbo as the issue?

Please let me know if I can provide any more information. I will update the post with videos of the smoke ASAP. But for now it looks VERY similar to except there isn't that much smoke and the small puff of blue smoke on cold start.








Cheers

andyfloyd

Sure does sound like stem seals, they will leak at idle and overnight so when you first start the car itll blow smoke. If you dont see smoke on boost the turbo is likely fine. Piston rings would be burning oil all the time. If those seals are Supertech thats DEFINITELY the issue.