NSX Technical Part 2

If you made it past part 1 this is part 2 of the NSX Technical Series. I do assume that these parts are familiar to you. If there is time I will try and go back and take better pictures.


The best approach would be to make our own electrical harness, however we are limited by time.

The NSX has 12 Modules that talk to the PCM or as it’s commonly referred to as the Engine Control Unit (ECU). To our surprise a few modules were left functioning in the race car.

Security System

This was left connected and so it has to be removed. It would definitely not be amusing if it activated during a race session.

We elected to maintain the key start and so this is our solution to bypass the security wiring.

  • C11 is ignition power
  • C22 is ground

C11 needs to grounded / shorted.

Our solution: OBD1 twenty-two pin male plug and loop C11 to C22 (plug and play). There is most likely a more elegant solution, but with a roll bar through the dash in the way this was the solution.
* better solution would be to trace circuit, but the FSM is a little cryptic

Anti-Lock Brake (ALB)

Again, 1990 technology with the focus on 1990 wheel and tire technology. It’s a rabbit hole that we won’t go towards. In theory, if you maintain the TCS module, power switch to the ALB module, and then power switch to dash or fake the signal back from the dash… it should work after 5 seconds.

Yup, two 8 bit processors, 16 bit data transfer, extended because of the (A); It’s a beefy micro processor for it’s time.
I’m not savvy enough to find the datasheet.






OSGIKEN Differential (Clutch Type)

  • Country of R&D – Japan
  • Country of Manufacture – Japan (In-house)
  • Quality Control – Standard
  • Metallurgy – TBC
  • Origin of Barstock – Japan
  • Heat-Treatment – Standard
  • Lock Capacity: 20 clutch-disc setup, allowing an adjustable 20/40/60/80/100% Lock Capacity
  • Pre-Load: Spring type. Adjustable between 0-100% Pre-Load (~85lbfts)
  • Aggressiveness: Fixed Cam, Non-adjustable (Additional Cams may be available)
  • Warranty: 1-Year, Region-based
  • Guarantee: N/A

What kind type of fluid?

The honest part is we don’t have any technical information on the diff.  I’ve sent and called Osgiken for support and have been turned away;  they want me to contact a distributor. The distributors of course tell’s me I should bring the differential for service… WTF, isn’t a magical device… I digress.

This was hard to find. Which is shocking since OSgiken back then was hitting strong with their PR machine. So there should be info out there right?!? – nope. In the end Kelsey and I came up with the same solution of running a weight of 75w140. Eventually, through conversations with OSgiken who were slow in responding they did verified what we figured out – the suggestion was to run 75w140 as a weight.

We are using a blend of Honda MTX and Motul Competition 75w140.

The OSgiken OS-250R (80w250) is pretty thick and is not recommended for transaxle applications. Although, this was on the website and highly recommended online – and we know how reliable that info can be.

12/20/2016 Conversations with US division OSgiken, apparently they no longer supply technical information. It seems like they have had issues with damaged installation. This makes it harder to understand and monitor the diff. We want to make changes to the cones, springs, and plates. This also means it is essentially a black box at the moment. I don’t like black boxes. The semi good news is they will service the differential at a reasonable cost; Service is $150 USD including shipped back to you + part costs. The tuning part so far my understanding is that it’s just parts…

I need a few more conversations on what “tuning” means and how records are kept. So there will be a part three after all.

Comptech / CT Egineering

This NSX competed in the Historic Sportscar Racing (HSR) with a Comptech super charger and these parts are no longer part of the build – old school methods. We are running a full stand alone and fuel pressure is lot more manageable when it is one to one, 1:1.

Comptech Fuel Management Unit (FMU) – It’s implementation was to bypass the Fuel Resister while under load and to supply a constant power feed when under boost and the fuel regulator – voltage would rise. How much? My guess is closer to 14 volts.

Comptech Fuel Regulator – It is a rising rate fuel regulator. It’s a good part for street use , the only downfall is the unknown exponential increase in pressure. To be honest, for me it makes a lot of sense when setup with a FMU coupled with OEM parts that may not be able to supply the required demand.

It brings back memories of Apex Power FC and HKS FC … Yeah, I’m old school.

Bolts / Misc

The reality is that some parts are no longer manufactured.

These parts will be harder and harder to source unless you know a machinist. Lucky for us we have two on the team.



This ends Part 2. There might be a Part 3 in the works as I recall from my notes.

Collaboration with Kelsey B.

Part 1    Part 3 (soon)

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