Transmission upgrade - comparison.

[Yankee]

Dears,

I'm still on my quest "how much is possible to invest in my NSX"
I have done much to intake/exhaust and feeling a good upgrade in HP and torque, but all HP remain on a flywheel. I have to drive either 19' or 18' rear wheels and cannot go down due to BBK. I need to have more HP on road, thus have to do something with transmission. Could you please share what you have done to your gear box. If it is a good idea to upgrade it up to 6 speed transmission (or even buy a used NSX-R transmission) or possible to keep 5gears and install final drive?

Also what are better OS-Giken 4,44 or NSX-R 4,23?

Does it needed to install OS-Giken differential?

What is better choise in case I think to go Supercharged next year. Any advices are welcome...

 

[goldNSX]

If you're already went the route of 18/19 a different gearing will not be very effective. A CTSC or in general more HP is the only thing that helps you out.

 

[Yankee]

If you're already went the route of 18/19 a different gearing will not be very effective. A CTSC or in general more HP is the only thing that helps you out.

Thanks for the clue. What is CTSC?

 

[MvM]

Thanks for the clue. What is CTSC?

CTSC is short for CompTech Super Charger.

A supercharger will easily give you an additional 60 RWHP (rear wheel horsepower) extra on top of what you have now. They went out of business but they are starting up again under new management. You might find this link useful.
http://www.nsxprime.com/forums/showthread.php?t=107542

As for the gear-options, I guess it depends on the speeds you will be travelling with. The Japanese gears (short-gears in popular terms) will give you faster acceleration up to around 100 mph, but above that, they will be slightly slower.
A different differential will give you slightly faster acceleration all around but you will be travelling at higher RPM's at any speed and that could be a bit annoying after a while.

Perhaps you can state you full list of modifications, it might make things easier for people to give you a number of options.

As for your location, are there any qualified NSX-mechanics in your area you would trust to do these kinds of things to your car without damaging it?

 

[MJK]

I went from a 5 to a 6 speed. The big upside is not having that power lag on the 1->2 shift. 1-5 are great around town and 6 is a great freeway cruiser.

Things I think I did right:
Kept the OE 5speed twin disc clutch (with NSX-R input shaft)
Got a light flywheel (Jun)


Things I wish I did:
Also put in a shorter gear ratio. In retrospect, I wish I had put in the 4.23 at the same time. OSG 4.44 would be great for track, but probably a little short for the street.

That said, it is not great bang for the buck. By the time the total bill was in, I could have put in a CTSC. I agree that a CTSC or a 5 speed 4.23 w/ light flywheel is probably a wiser use of your money unless you do a lot of freeway driving.

 

[nsxtasy]

Bob Butler calculated 1/4 mile accelleration times for various gearing setups on an otherwise-stock '91 NSX, as follows:

Stock 13.67 seconds
Short gears and stock R&P 13.56
Stock gears and 4.235 R&P 13.57
Stock gears and 4.55 R&P 13.43
Short gears and 4.235 R&P 13.48
Short gears and 4.55 R&P 13.38
Six-speed 13.56
Six-speed and 4.55 R&P 13.36

To put these numbers in perspective, here are the effects of a couple of other changes you can make to an otherwise-stock '91 NSX:

Reduce weight 100 pounds 13.51
Add 15 hp 13.35

He also did the calculations using a stock '97-05 six-speed NSX:

NSX Coupe 13.24
NSX Coupe and 4.55 R&P 13.06
NSX-T 13.39
NSX-T and 4.55 R&P 13.20

 

[Yankee]

CTSC is short for CompTech Super Charger.

A supercharger will easily give you an additional 60 RWHP (rear wheel

As for the gear-options, I guess it depends on the speeds you will be travelling with.

Perhaps you can state you full list of modifications, it might make things easier for people to give you a number of options.

As for your location, are there any qualified NSX-mechanics in your area you would trust to do these kinds of things to your car without damaging it?

Thanks you. Actually I'm almot ordered CTSC from Chris of SOS.
Actually my upgrades are:
Exterior
Rays TE37 17/18'' 9,5/10 + 40/Yokogama Advan A-048 225/45ZR17-ft; 265/35ZR18-rr
HRE 841R 18/19'' 8/10,5 - Black red lip + Toyo Proxes T1R 225/35/18-ft 285/30/19-rr
TAITEC GT2000 ft Bumper <> TAITEC rear wide fenders/quarter panells <> TAITEC GT500 CFRP rear wing <> Margahills side skirts <> BBK - Brembo GT kit + Brembo E-brake on drilled rotors <> CFRP Side Ducts <> TAITEC rear diffuser
Interior
Honda Zanardi / Type-S Shift Knob <> Zanardi rd/black floor mats
Engine
ScienceofSpeed Big Bore Throttle Body <> Cantrell Carbon intake <> ScienceofSpeed Super tuned ECU <> Taitec GT-011 Manifold <> Taitec GT-003 Catalist pipes <> Taitec Parallel Exhaust GT-106 STLW <>
NSX short shifter kit <> TEIN Mono Flex <> FT/RR JDM NSX-R anty sway bars <> NA2 ABS system <> Okuyama rear Brace <> NSX-R Front Chassis Reinforcement Bars <> Cedar Ridge Non-Compliance Front Pivot Clamp Kit <> ScienceofSpeed Adjustable Anti-Sway Bars <> TEIN EDFC

I'm thinking about NSX-R final drive - but uncertan in 2 things - if it will help me to accelerate faster both los speed and high speed, an if if will be possible to drive with my OEM clutch (2 disk) Also I have European NSX that, as far as I know, have different (like in US) gearbox...

Now I'm going to order AEM ECU on top of all. Mechaniks we have - mine is 50 years old and former rallist. However will appreciate your advices...

 

[Yankee]

Bob Butler calculated 1/4 mile accelleration times for various gearing setups on an otherwise-stock '91 NSX

Interesting. My best time was 13,62. So 6 spd make her accelerate faster?

What is R&P?

 

[nsxtasy]

Interesting. My best time was 13,62. So 6 spd make her accelerate faster?

Yes, it does.

Often people can do better than the published or calculated numbers for a car, because they have modifications done to their cars, they empty the car of the spare and other standard items to reduce weight, etc.

What is R&P?

R&P is the ring and pinion gear in the transmission, sometimes called the "final drive gear". When the power goes through the transmission, it goes through the drive gear (first, second, third, etc) and then through the R&P, so changing that ratio affects the gearing in all gears.