Rod bearing gone?
 

Hi guys,

First time post here, long time lurker. Not US-based, but hopefully that won't be a problem in terms of sourcing the parts you suggest. I have a 2001 1.6 FM turbo Miata with RX8 injectors. Turbo kit was installed over the winter, running about 7psi of boost (GT2560 actuator pressure) and driven on public roads for about 1500 miles without any issues. Took it to a track day on a kart track and, during the second 15-minute session, this sound presented itself. AFRs were always ok and ignition map was quite conservative.


Car is with the mechanic right now, plan is to take the engine apart and assess the damage. Turbo Miatas are not that common around here, so would prefer to have a second set of opinions and advice on whatever we find. Plus talking about future mods is almost as exciting (and significantly cheaper) as getting them. :) Will be pulled apart next week and should have some pictures then.

Yep, sounds like a dead rod bearing.

Where are you from, I guess somewhere in Europe as you have a NB 1.6 ?
Might also be useful to understand why your rod bearings went south, before blowing up another engine.

I'm from Romania.

After I retired early from that session, checked oil and it was well below minimum (needed an extra 1.5 litres to get it close to max). So my guess is no oil. I suspect some kind of seal failure as mechanic said there was a right mess on the underside. Also (foolishly, I admit), I drove the car back home after the event (no boost, kept under 2500 RPM) and added another 2l of oil over the 80 mile journey. I have another used 1.6 engine that I bought, might be worth just giving that a quick service and use it instead of bothering with this one?

My aim is to get a reliable 200 WHP track car that I can use for 20 minute sessions in 30*C (86F) weather.

Is the used engine also from an NB? There are a few differences between the NA and the NB 1.6 (solid lifters, ignition system).
I would not use the engine which had the spun bearing without full inspection and cleaning, so using the other engine sounds like a good plan.
Given that you already use RX-8 injectors, I assume you are already using a programmable ECU?
Reliable 200whp sounds like a realistic goal.

Yes, that's an NB engine as well, bought used from a reputable seller on ebay, but never heard it run. Thanks for the advice, probably easier to just move all the turbo stuff across.

Running ME221 management.

Is the NB 1.6 VVT? With any bearing damage, make sure to replace anything you can't clean. Even the smallest piece of debris left will make it's way out and ruin your new rebuild. Biggest piece people forget to replace is the water/oil cooler, where the oil filter screws on to. Holds a lot of oil/bearing material. Otherwise 99% of used motors need a crank/water pump/timing belt/cam seals.

No, the NB 1.6 has no VVT.
But it does have solid lifters and the same ignition system as the 99-00 1.8 NB.

Ok, so new engine. What supporting mods should I put in place to get a reliable 250HP track car?

Was thinking:
1. Coolant reroute
2. Uprated oil pump
3. Bigger radiator

And some engine protection strategies and dash gauges for oil temperature and true oil pressure. Sounds about right?

Just conrods and adequate oil and water cooling.

You do not need an oil pump for a reliable 250HP track car. Weakest link in the engine are the conrods, so that should be the first thing to replace.
If you stick with the standard conrods then you should limit boost / torque in order to not bend the rods.

I know that 250HP (estimated at the fly) is pretty much the limit for standard internals (225 ft lbs torque). So aim is to stay under that limit.

While one might not "need" an oil pump at 250 rwhp, if I had the motor out of the car and apart I would think strongly about putting one in then.

--Ian