HarryB's Strato blue NB2

[HarryB]

New Year's update: with the Maruha deep top hats, fresh OEM rubber donuts and bump stops in hand, it was time to disassemble the Maruha coilovers.



Mostly to clean up and inspect, but also to measure general dimensions and travel; you never know when you gonna need data! I will post the findings to a new thread as AFAIK not many people use these and might be of use to someone. One key point is that although Maruha advises in replacing the damper units once shot, these are proper rebuildable units; the bottom cap is removable (threaded not crimped) and there's a schrader valve installed on the bottom, although not visible with the units assembled. Just for science, I am going to check with a reputable damper re-builder on what's possible.

[HarryB]

Coilovers now clean and ready to re-assemble. Took a fair bit of degreaser, a toothbrush, some WD40, and a quite bit of elbow grease but worth it!



Need to buy some copper grease and some sock-style covers to keep all the dirt out before (finally) putting them on the car.

[HarryB]

Suspension re-assembled, although everything just hand-tight for the moment. Used non-metal brake grease (Mintex CeraTec) as I found out I had no copper grease left, and replaced the lower damper rod nuts with OEM ones, as I liked the fact they are much larger in diameter and thus spread the load more evenly on the top hat shim. It also seems I will have to fab some bump stop spacers, as explained on the Maruha suspension thread. All assembled:



Speaking of OEM flanged nuts, the right-hand tail light ones have been replaced by the PO at some point with generic hardware which I did not like. Trying to stop a leak, I also replaced the OEM foam gaskets with some DIY ones, but both facts tickled my OCD....so, fresh OEM stuff is in!

[HarryB]

Updates; or kinda. Decided to do an engine swap. My car is an NB6, so 1.6, with 190k kms at the moment. I plan on boosting this (using a Rotrex supercharger) but I know it would eventually bite the dust, although compression is really good and it has been properly looked after.

I was planning to get a spare engine to rebuild on the side, and be ready to swap that in when time comes. I came across a 1.8 VVT engine/gerabox combo with 30k miles on them (or at least the seller claimed so, and I tend to believe him from how clean was everything beneath the VC), price was good so I bought it. I also bought a stock 1.8 ECU and engine wiring loom, so that the swap looks OEM.

Primary goal for this engine is to refresh it so it can make another 120k miles RELIABLY with mild boost. As such, I plan to do the following:

7500 max redline, stock CR (10:1), pump gas (no E85 here), Rotrex C30-74

Bottom end:
Boundary oil pump
Maruha oil pan baffles
Usual service items (seals etc.)
May replace freeze plugs (they are cheap) and paint the block as well while I am on it.
Stock/untouched otherwise (OEM crank bearings/bolts, pistons etc.)
Rotrex is easy on conrods as it builds up boost with RPM, but I may throw in a set of forged rods (Manley w. ARP bolts) just to help me sleep at night. If this happens I will also replace piston rings with NPR. I was actually thinking leaving the crank in place, remove rods/pistons, clean up pistons, slap new rods, put it back together. Leaving the crank in place means no decking of the block. I will measure flatness and roughness, and will remove crank if the block needs decking.


Head:
Head will have to be removed to swap out the HG for an OEM for a 99-00 engine (BP4W) which is necessary for a reroute in these VVT engines. As such:
ARP head studs
OEM BP4W MLS head gasket
Pressure check, deck/cleanup to get a proper HG surface
DIY ports cast flash cleanup (since it will be dissasembled)
New OEM valve seals
VVT actuator rebuild with Miataroadster viton seal kit
Eibach 20410.116 intake valve springs. My thinking is to use heavier ones only on the intake, to compensate for boost. Given the OEM cam specs, OEMish rev limiter and Rotrex, I do not see any need for heavier springs on the exhaust side; my logic says that they will only increase wear and parasitic losses, even marginally. On the intake side, and calculating a boost of 14.5psi over a stock valve, I see that I need an additional 37lbf of seat pressure to counteract it. It's oversimplified as a calculation but at least it gives me an idea. Does anyone know the OEM valve seat pressure on a VVT head? VVT intake springs are supposed to be heavier than non-VVT BP4W ones, and I can only find data for these.

Ancillaries:
EUDM Squaretop manifold
Maxim Works exhaust manifold to custom 2.5" exhaust
Rotrex C30-74 blower on custom designed/build mount
MS3 mini ECU (eventually, car will work as NA with OEM ECU for a while)
Bosch EV14 640cc injectors
DW200 fuel pump

Suggestions are always welcome!

[— kung fu jesus —]

I understand the reasoning to leave the crank in place, but I think it’s leaving low-hanging fruit on the tree, so to speak. The plan for the amount of pressure you are targeting with the supercharger is sort of the tipping point which induces more wear on stock parts.

I understand the added cost having the machine work done, but not having the bores checked and rehoned, let alone the block and oil gallies tanked and cleaned seems like a shortcut that may add to your questions later down the road. Additionally, stronger main bearings would offer more peace of mind and insurance with the added power.

Polishing the crank journals, replacing the thrust bearings add to the assurance, particularly if you are removing the pistons and rods anyways.

I don’t know the stock valve spring pressures, but I do recall 14psi of boost is the line of demarcation where the springs are affected. Do note that there have been issues with the valve stem seals Supertech provides/sells.

Consider making an auxiliary circuit with additional relay with the fuel pump you listed. It seems larger fuel pumps tax the OE relay in short order.

[HarryB]

Thanks Steve! Indeed, these are all meaningful suggestions. The redline boost indicated was more for a peace of mind. In reality I think I will stick to something much lower for longevity both on the engine and the blower (9ish PSI would do it).

In that scenario, the last item on the "block" list is not mandatory, and at the moment my mind is 50-50. I am seriously considering leaving the short block as-is, and adding only the Boundary oil pump and sump baffles. In theory, all bores *should* be OK (if the mileage is true), but my plan is to measure them once I remove the head in any case. The bearings comment still stands true. Do you recall if the OEM conrod and main cap bolts are torque to yield or if they can be reused? I do not wanna cheap out, but rods, rod and main bolts, bearings and rings add up to almost twice of what I paid for the engine itself (yeah, VVT engines can be had for cheap here).

[— kung fu jesus —]

The conrods bolts on my B6 were reusable. I don't know about the BPs. 9psi seems more reasonable, leave a lot of built-in safety at that level.

I completely understand leaving the engine block untouched. I think I would do the same if the bore walls check out, other things.

I now understand better what you are preparing for, but not sure upgrading all the components (internally) are needed. I might just recommend the head gasket, head studs, maintenance refresh and then stuff it in the car. Build for the intent, not necessarily the worst-case scenario.

[MiataQuest]

Your local fuel octane should play into your equation of compression and boost.
I think your high octane is around our USA 93 octane.
If the timing always needs to be dialed back you are losing power while at a risk of damage.

Consider this simple low cost route with a stock lower end while running the supercharger:
* Oil cooler with a thermostat.
* Accusump kit instead of all the baffling, etc
* Run Mobil-1 5W50 FS X2 oil (Mercedes formula) to protect the rod bearings and reduce oil whipping at high RPMs.
* Change head gasket to achieve a lower 9:5/9:3 to 1 compression ratio (Cometic?)
* While you are pulling the head anyway, install the ARP studs and smooth-out the exhaust ports.
* Add the bigger injectors and change the fuel filter.
* Header and exhaust.
* Present intake manifold is good enough with boost.
* 4:11 Torsen
* Tuning

[HarryB]

Thanks for all the comments! Steve you are right, no point in spending a shitload of money on building a fully forged internals monster of a motor when not needed. I need something mostly OEM, but refreshed as much as possible, and willing to take mild boost without any reliability issues. Hell, if K-swaps were road legal, I would not be bothering with boost at all, as I feel that more than 200 whp are too much for my intended use (road car/canyon carver)

Euro octane standard is RON, while US octane rating is (RON+MON)/2. Regular gas is 98 RON, and we also have "premium" 100 RON, which translates to 94 and 95.75 on the US scale. I know that detonation could prevent me from running super aggressive timing, but I hate thick head gaskets as they are weaker and easier to blow. Might go slightly thicker, need to investigate aftermarket options and thicknesses. Good thing is that Rotrex chargers are quite efficient so at least IATs are quite low which helps with det. A good friend is pushing me towards a water/meth injection, but I do not think I will need that at my target power level (250ish crank hp).

I plan to clean up casting imperfections in both intake and exhaust ports, and port match the intake manifold. I already have a square top intake; it comes as standard with the VVT engine here.

The plan of attack is as follows:
Finish the engine rebuild-refresh.
Swap fuel pump with DW200 (not really necessary but guess the OEM one is getting tired, plus I already go the DW pump). I will follow KFJ suggestion running through a separate relay and use the OEM wiring just to trigger the relay. Will replace in-tank strainer with proper one for NB2, as well as the external fuel filter.
Swap out the 1.6.
Swap engine wiring loom, injectors and ECU with an OEM 1.8VVT one (already got these) to simplify things and make sure it runs.
Install MS3 and tune.
Swap injectors with EV14 and fine tune.
Add Rotrex.

Knowing me, this most probably will take a couple of years, but I am taking this easy and love doing everything by myself, so no rush; it's all about the journey.

P.S 4.1 Torsen is already on the car

[MiataQuest]

If engines are plentiful and you will not change the compression ratio, I would be tempted to try your 30,000 mile engine as it it is. Not even do a cooling re-route.
I would change the front seal & timing belt and the rear seal and clutch then enjoy.

[— kung fu jesus —]

Playing with head gasket thicknesses aren’t a good idea to lower compression.

I think your plan is very manageable, Harry. The 250hp may come with tuning.

[HarryB]

Thank you both! I really do not like (much) thicker head gaskets. In order to have a meaningful effect on CR you need to use a much thicker one, which is weaker, and messes up with the squish zones as well. I know of a handful of cars around here with turbocharged stock, relatively high mileage VVT engines; no reroute or anything and they seem to have zero issues until conrod bending torque levels. Rotrex should be better on that aspect due to the nature of the "beast" (lack of midrange torque). What MQ proposes makes sense in a way; I can always remove the head at a later stage if needed, but I prefer to have peace of mind as much as I can, and reroute helps.

I forgot to address the oil cooler issue; I am currently designing my own version of a reroute, which will eventually utilize a Laminova oil/water heat exchanger. I like these because they help warming up the oil on startup, and keeping it cool when you reach operating temperature. They also keep the oil lines short and is simpler to integrate (no space in the front of the car ATM).

[Slampen]

Laminova oil/water heat exchanger.

Another Laminova fan, Yeah!!

Guess you have seen these
https://forum.miata.net/vb/showpost....3&postcount=10
http://laminovapro.com/

I like this solution if you choose to cool your gearbox. But that will probably not be an issue with a Rotrex.

[HarryB]

Actually, I have not seen that Miata installation, thanks! My planned one is similar enough but with a smaller core, placed under the intake manifold. And that gearbox idea is neat, I doubt that I will need a gearbox cooler for my intended use though.

[HarryB]

Till I manage to get started on the engine, I decided to let some steam off and actually replace some parts I already had. Started off with the cowl panel. Mine had cracked so I bought an IL motorsport replacement. The kit is super complete and comes with everything you need.



I decided to skip replacing the white mounting tabs since the original ones were in decent shape. Overall the quality is nice, although the color itself is a bit off (more gray than black) and I may be repainting this sometime in the future. Installed pic:



Next up, pedal covers, as mine were pretty worn after 110k miles. OEM freshness:



Decided to remove, refurb and reinstall the dead pedal at the same time...



...along with cleaning the 15-year grime under it and repainting the throttle pedal. Don't mind the filth, car needs cleaning.



I also went ahead and replaced my window switch. Tan ones are way more brittle than black (guess has to do with coloring in the plastic) and 15 years of sun exposure did not do it any favors. Sourced a black one with all tabs intact, took it apart, cleaned everything really well, and had a color matched spray can made.



While I had it all apart, I also trimmed the plastic gear boot ring. This is originally taller on the back, which stretches the leather boot when going in 5th and annoyed me a LOT.



End result, after giving the center console a quick wash as well.



Not too bad!