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Today at Atelier Kaz - Private NSX Enthusiast, ex-Honda R&D engineer with F1, Indy/CART background

Eng Refresh Stage 1 - 16

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Started vacuum filling the cooling system.

Preparing for the fire up.
After wearing the ear plugs in case the security alarm triggered, re-connected the
battery that was on battery conditioner from the start of the service.

As reported earlier, there was a trace of repair at the battery holder bracket and
as expected, I had to stop tightening the holder as it started to bent at the place
where it was repaired.
Although it is enough to hold the battery for the time being, please replace the
bracket in the near future.

Fired up the engine and warmed it up in preparation for the compression check.

In the process of compression check.

#1cyl: **5, #2cyl: **5, #3cyl: **8,
#4cyl: **0, #5cyl: **2, #6cyl: **0

Happy with the result.

As reported earlier, the TH butterfly was really dirty.
Decided to clean it for the owner as I donít want to see idle rpm issue after
the service.

Applied silicone grease to the new rubber seals at the IG coil covers.

So, almost all of the parts are now back in place at the engine bay.

Will adjust the coolant level after the test driving session and reset the ECU.

Ideally, wanted to finish painting the drive shaft joint but ran out of time
so had to stop for the day.

Considering the other project, looks like I need to work over the weekend againÖ..
Only one proper day off so far this yearÖ..



  1. gumball's Avatar
    Nice work Kaz.
    The car seems to have quite a high charge rate. Can it be too high nowadays?
  2. Kaz-kzukNA1's Avatar
    Hi, gumball. Thank you for the kind word.

    Not sure I understood your question correctly but if you are talking about the charging voltage, then there are so many factors to be considered such as the spec of IC regulator, temperature, time after the engine started, load, battery internal resistance, conditions, etc so not simple by just looking at the gauge.

    I donít know how accurate this gauge is but on almost all of the NSX with healthy condition, the IC regulator is regulating it with the gauge reading at about 14.5V to just below 15.0V under normal driving speed. With simple, plain, normal battery, the calculated full charge balance (don't know the correct word in English) is at about 14.5 - 14.8V and later NSX model tends to show about 14.5V whereas early model tends to be just below 15.0V on the dash gauge.

    As long as itís below 15.1V, you are fine.
    Although there is a big Zener diode and protection circuit against over voltage in all of the controller modules, most of the smaller modules, driver, etc wonít have it so if you see anything above 15.0V on the gauge, best to check your ACG.

    Among the NSX owners in Japan, ACG failure is very rare and in fact, people just replace it with the rebuilt one as a preventative measure even before experiencing any signs of failure.

    You canít judge the condition of ACG by the mileage but just as a reference, I checked my ACG after about 116K miles and still the brush was nowhere near to the limit so just carried on using it and then decided to overhaul it at about 128K miles even I didnít notice any issues.
    Electronically, there was no problem at all but decided to replace some components any way and in fact, it was one of the bearing that was showing some rattle although there was no noise.

    Denso products are very reliable.

  3. gumball's Avatar
    Thanks Kaz, interesting but electronics really confuses me lol.
    Way back when I trained as mechanic(I can't believe it either), I remember being told to watch for over charging, but this was a long time ago, most of the cars I worked on still had a set of points and condensor, When I left the trade in the 90's cars were already getting very complex electrics, so i was left behind.
  4. Kaz-kzukNA1's Avatar
    It is still true, overcharging is not good for the health of battery and it will shorten the life of it.

    So, long time ago, some of the car manufactures started to add the ACG control logic so that it will only charge the battery at deceleration rpm stage or under braking except for certain conditions where the battery has to be charged immediately. Our NSX is a classic car so .....