1998 NA2 Coupe full refresh adventures

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Since there's been so much work done on that car to start with I'll start documenting it, at least for me to remember

It's an Euro-spec silver '98 NA2 Coupe, black top, black interior.

It was bought in Spain from the 2nd owner, the maintenance seemed spotty - 1st owner did everything at Honda, 2nd did not and their mechanics obviously didnt know how to work on that car... Some bolts were the wrong size and forced in (needed to repair those with helicoils), front engine bolt was replaced by something not from Honda and just snapped in half, and a few other surprises which led me to last year "heavy refresh" decision.
I'll detail everything in the next post for readability

 

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What was done before the refresh:

Engine / transmission:
- Poor repaint of the valve covers (dated from Spain)
- 80K km maintenance done in Spain by shady mechanic. Everything points at the top of engine having been open at some point. I'll get back to that
- Lightened clutch flywheel (dated from Spain)
- Koyo radiator, some important cooling hoses replaced
- Otherwise stock

Intake / Exhaust:
- Toda Ti catback exhaust (specific model for 97-01 NA2..)

Suspension / brakes / wheels / chassis:
- Bilstein shocks with Tein lowering springs (dated from Spain)
- Stoptech slotted rotors (NA2 OEM size)
- Hawk pads
- Rays Volk TE37SL 17" / 18" wheels, build on order with specific offset & sizing (which I cant remember exactly - I'll edit this after I get the car back from its refresh)
- Border Racing rear strut bar

Exterior:
- Downforce NSX-R rear wing (with the brake LED)
- Downforce NSX-R-style front hood
- Downforce hood scoop
- Downforce rear lower bumper
- at some point a Downforce rear diffuser that's scraped so much everywhere it's now entirely destroyed and removed
- Spoon mirrors
- SOS front licence plate bracket
- Guppy antenna (dated from Spain), they gave me the OEM antenna as a spare part (I'll probably sell it)

Interior:
- Completely stock
- Broken door panel tabs (almost all of them) with various wrong sized screws
- Broken rear panel (one corner gone)
- Otherwise in really good condition (seats, knee bolsters, etc.)
- OEM radio with a GROM USB thing
- Downforce NSX-R engine lid


What's being done right now:

Engine:
- Full engine rebuild and cleanup short of pistons & cylinders (those were still pristine) - really was not confident in what was done in Spain on it...
- Absolutely all engine and transmission seals, and all rubber hose, are now new
- Polished head ports, ported exhaust ports (port matched to the SOS headers)
- Cleaned and polished valves
- Toda oil pump gear
- ATI damper pulley
- '99+ LMA's
- Cometic head gaskets
- SOS custom ARP head studs (had to Timesert the threads..)
- All new connecting rod bearings
- SOS billet camshaft plugs
- SOS oil sensor relocation kit
- SOS baffled oil pan
- New expansion tank with NSX-S black cover
- AS Motorsports special gaskets for the intake manifold
- ATR oil cooler kit (located behind passenger side scoop)
- Foundry3 lightweight alternator bracket
- Foundry3 billet engine mounts
- re-painted valve covers with VHT red wrinkle

Transmission
- NSX-R 6-seed input shaft with the dual spline
- Exedy dual clutch & flywheel
- New 2nd gear synchro (it was almost gone, missing teeth entirely on one side..) and new bearings
- New clutch plates for the diff
- SOS slave clutch hose kit

Intake / Exhaust:
- Toda high flow cat converters
- SOS exhaust headers
- Downforce intake scoop (and deleted the stock resonator..)
- all new o2 sensors.. they were completely shot (leading to a CEL)

Suspension / brakes / wheels:
- new stainless steel braided brake lines

Exterior:
- KSP side skirts
- Dowforce CF side scoops
- ATR front & rear CF bumpers
- ATR CF battery tray
- Deadweight Industries LiFePo battery
- CF brake air deflectors

Interior:
- Mita door panels repair
- Zanardi short shifter
- OMP light steering wheel (with the Mita NSX-R style hub kit)

 

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What's planned in a near, or more distant future:

- install the KSP side skirts and repair / repaint the rear bumper (it's got a light scratch and indent)
- install the teflon window rail guides (thanks Bruno !)
- see if I can install a CF center console so I can run a modern system with Android Auto..
- ABS upgrade
- Ohlins coilovers
- a lift system (iLift have stopped selling to end customers - so I have to find something else, that will fit the Ohlins, and that can be hidden just as well as the iLift) so I stop destroying my front lip spoiler
- All suspension bushings (maybe that Prothane kit, the need for mods is not a good news though, that T3Tec kit looks good but $$$)
- Install under body panels front to rear (got the Downforce panels for the fuel tank and engine bay, and a 02+ front underbody panel that obviously wont fit, the seller thought all NA2 were post-facelift..)
- Maybe find another diffuser once I have the lift kit so I dont kill it again
- delete the antenna completely (really have no use for it..)
- maybe CF seats, continuing the light weight trend. ATR seem to have custom CF shells, AS Motorsport have the CF Recaro's, Bride have some nice CF models (Zieg IV, for example)
- Reprogram the ECU to cash in from all the mods. I want absolutely to keep the cruise control so AEM Infinity is out of the equation. AS Motorsport says that Haltech can keep its function...
- LED lights (starting with front turn signals, one has got a rock chip..)
- RFY intake - I know, zero gains, but it really dresses up the engine bay...
- wanted to delete the headlight washers, they are like ugly warts, but it seems they are needed or I fail the MOT, maybe switching to LED headlights would allow for them to be removed...

A few photos from the current refresh:

stock rod bearings, two (passenger side.. oil starvation in turns) were very slightly marked:

Open engine:

Crank, in a really good shape:

Cylinders, in a really good shape too (we see a mirror reflection of the piston):

It's been almost 1 year stuck on a lift due to mechanics getting sick, parts shortage, global pandemic and supply chain issues, then that war in Russia that delayed all shipping from Japan... Hopefully it's about to get put back together again and I can enjoy it before this autumn.

 

[docjohn]

Looking forward to your refresh.... thanks you for loving NSX

 

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I hope the spirit of Soishiro-sama is indeed keeping watch on it, engine block is now completely assembled and ready to get filled with oil to check for pressure, and adjust the valves clearance. Each bolt was torqued to specs and marked with white paint. OEM oil cooler was a bit rusted so everything was cleaned up and is now like new out of the factory.
Also when installing the new head bolts we pulled the threads - Timesert are now in place and indeed really strong. It seems as if the heads were pulled out once before (back in Spain) and the threads got damaged.

Then what's left is putting the transmission back on, and put everything back up where it belongs...

 

[docjohn]

...hmmm the Spanish inquisition...:frown:

 

[BBVNSX]

Looks like a great refresh program you have there! :biggrin: and future plans sound great too! :wink:

Keep the great work!

Who do you plan to use to program your ECU (Haltech or other)?

 

[Arkaid]

Has always been one of my favorite cars on the forum. No great to see it going through the refresh and cant wait to hear all about it when it's back on the road. Enjoy it!

 

[Yinzer]

- wanted to delete the headlight washers, they are like ugly warts, but it seems they are needed or I fail the MOT, maybe switching to LED headlights would allow for them to be removed...

Funny, I've always thought they looked good, and appreciated the function they served. All the girls with straight hair want curls, and those with curly hair want it straight...

Stellar car and post!

 

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Thanks for the compliments ! Trying my best to keep it clean and as close to the original spirit as possible (more of a resto-mod)...

Who do you plan to use to program your ECU (Haltech or other)?

That's the big question. One idea would be going to the Netherlands so AS Motorsports can do it but that's quite the distance.. Yamamoto-san (owner of RFY) told me he could fly in and do it here, that's also an interesting option that doesnt add a lot of mileage to the car but of course I'd have to pay for his trip.. Both are using Haltech.
One big question is will they find a compatible ECU to start with, as my '98 is a weird OBD1.5 thing, I can bet money nothing is plug and play, as I learned the hard way with exhaust headers and many other C32B specific oddities.
Local shops are of course completely out of the equation - they know nothing about the car, I wont let them touch it apart from strapping it on a dyno maybe.

 

[Honcho]

Oh man another epic refresh thread! So excited to see it completed! Having just gone through this, I would think twice about the SOS cam plugs and oil cooler (unless you track regularly). The OEM cam plugs (if installed properly), will last all the way to the next engine service interval. The metal ones have leaked, since it is really just the O-rings that are sealing. As for the oil cooler- you are introducing a failure point at the fittings where there previously wan not one. A sudden loss of oil is a bad, bad thing for the NSX engine.

 

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I hoped the aluminium plugs would leak less than the OEM rubber ones oh well.. I'll see to that when they start seeping oil. Engine is completely assembled and is getting back in... At least they'll look good while they last

And yes I do track my car (for fun only), actually its main intended use is mountain roads and track (both really intensive). The baffled oil pan is also part of that equation, as expected my passenger side rod bearings were starting to wear (which given their relative position is a sign of oil starvation in a right hand curve...). The goal was to make it a bit more bullet-proof considering I dont do competition with it, but still drive it as intended Maybe a top speed run or two on German autobahn will happen too... Depending if I go and see ATR in their home country (Austria) to get those custom CF seats and undertray.

(edit) the oil cooler kit is not from SOS but from ATR: it's very high quality, with a CF duct, and steel braided lines, custom fittings and a custom sandwich plate.

 

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Engine is back into the car, got some questions but first here are the photos

Here we see the special insulation gaskets made by Adnan @ AS Motorsport:

(see the other insulation gasket under the intake plenum

Cleaned and polished exhaust ports:

Those may leak sooner but they do look really good:

All properly torqued bolts are marked with white paint.

New SS braided clutch line but I forgot to buy a new slave cylinder ! Let's hope this one will hold for now (it's been "refreshed"..)

 

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So engine is now back into the car (and runs fine !):

Got a question - this lambda sensor (we see the cable hanging down):

Where do we route the cable ? I have a quite long extension for it - one possibility would be to route it up all the way around the top ? I cant see any way to get it past the oil pan cleanly and of course it should be nowhere near the exhaust collector.
(SOS front collector didnt fit properly by the way - it hits the oil pan and doesnt come out straight)

 

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O2 sensor cable was routed above the engine...

Clutch slave cylinder seems to be dead. It was really not looking good when disassembled, we tried to restore it but looks like it was not enough. Replacement part was pre-emptively ordered from Amayama but it's not there yet, maybe next week !

Depressing the clutch pedal all the way only seems to produce a small resistance at the end and the clutch does not disengage.

I hope it's only the slave cylinder: master cylinder (for LHD) is not available until December at least. More delays

 

[Superhatch]

Always a great feeling when putting a motor back in and hearing it fire up and run the way you want it to. Awesome rebuild so far, can't wait for more.

You ended up with the Exedy S2 clutch/flywheel?

 

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Yes that's the Exedy dual organic clutch + flywheel, mounted on a NSX-R 6-speed dual spline shaft. I got the full assembly kit from SOS so I suppose it's fool-proof enough that the mechanic put the release bearing correctly.

 

[MotorMouth93]

I don't think I've ever seen anyone replace rod bearings as preventative maintenance before (well, not counting BMW engines LOL)! Did you use plastigage or a dial bore gauge to check the clearance on the new ones? And do you have any photos of the main bearings I'd be curious to see how they looked compared to the engines I've pulled apart.

 

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I replaced only the rod bearings that were marked (main bearings were OK) - these are the C32 ones which are supposed to have consistent tolerances (only one possible OEM). Used the original color codes too as they were not really shot, but the slight marks meant the protective layer was gone in places. My mechanic did not have plastigage unfortunately :/ The photo is the first one I posted after the introduction I dont think I have any closer photo of these bearings.

On another news I'm getting both clutch cylinders from ATR who's saving me from another headache here !

 

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Thanks to ATR for being so quick The car is now on its wheels with everything complete and is going for rear bumper paint (there was a crack in the paint that was getting a bit too visible) and side skirts prep+paint. Going to try the car next week when the bumper is back on, before installing the KSP side skirts and I'll be done for that stage of the refresh.

 

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Slight delay on the rear bumper (it was in rough shape and had a layer of prep that would not stick to plastic !)... It's done now though. Most recent photo before mounting it, with that fantastic CF bumper beam:

 

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So it's now up and running, and I got to try it today before letting it go for painting the new side skirts. What a pleasure It's now a bit more raw and brutal with the twin plate Exedy clutch, and all the lightweight parts... I'll have to get used to it again !

I have a squeak when steering right though (when turning the wheel) - somehow that would be related to the electric power steering, but I fail to see what that would be. It's only when turning the wheel to the right, not to the left. Anyone got any idea ?

 

[Mac Attack]

Nice car! I don't know if it's the picture angle and lighting, but in your post #14, it looks like the oil pan has been dented inwards. This can happen when the engine gets rested on it like in the pictures above when it was undergoing the rebuild.

If it is dented then you definitely want that fixed. As designed, there isn't much of a gap between the oil pickup and the pan bottom.

 

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Thanks !
For the oil pan I think it's the angle and lighting. It's brand new (and was never rested upon) - I'll have another look in person but yeah the engine would have a lot of issues if it was really dented.

 

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So I got my car back at last after many delays (back ordered and missing parts, sickness leaves..) - it feels really good.
It's indeed more brutal now with the light weight clutch, new headers, high flow cats.. I'd consider it being at the limit of what would be reasonable to drive on open roads.

I seem to have a whistle noise that goes up and down with the revs: maybe a belt, maybe the alternator, or a pin hole exhaust leak from the headers.. Cant locate it, but I suspect the headers.

I was considering the RF Yamamoto headers but no one seems to be able to tell me if they are compatible with the NA2 layout (for example KSP headers will not fit at all, they are way too long). That's a $4000 gamble (incl. labor and shipping) I'm not going to take...