NSX chassis

[stevecct]

Just wondering are all NSX chassis the same? (In terms of the overall structure, rigidity etc)
From the oldest 1991 normal NSX to the newest 2005 NSX
From the normal to the high-end model Type R/NSX R

My technician strongly disagreed with me doing the manual transmission swapping (from AT to MT)
He thinks the chassis, and engine are different.
I never can turn an AT nsx to "MT nsx", even swapping the gearbox, the camshaft, springs, and ecu.
Because they are totally different story.

Prime dudes, please let me know your thoughts.
(FYI, a fair condition MT nsx costs around 1m usd here, and a AT nsx costs around 50-55K)

 

[docjohn]

Where are you?
All coupes have similar rigidity. The T top or targa needed some reinforcing and used a thicker frame rail. Many folks have done the swap, just search on prime

 

[stevecct]

Where are you?
All coupes have similar rigidity. The T top or targa needed some reinforcing and used a thicker frame rail. Many folks have done the swap, just search on prime

HK
yes I have read a lot of swapping threads. Thats why I think the swapping is make sense
All the holes are pre-drilled, even the ecu is similar, etc

 

[docjohn]

Between you and I , knowing what it takes If you pay someone to do the work, I would sell the AT and buy a MT

 

[stevecct]

Between you and I , knowing what it takes If you pay someone to do the work, I would sell the AT and buy a MT

Originally I will do most parts of swapping except the transmission up and down

 

[Honcho]

Just wondering are all NSX chassis the same? (In terms of the overall structure, rigidity etc)
From the oldest 1991 normal NSX to the newest 2005 NSX
From the normal to the high-end model Type R/NSX R

My technician strongly disagreed with me doing the manual transmission swapping (from AT to MT)
He thinks the chassis, and engine are different.
I never can turn an AT nsx to "MT nsx", even swapping the gearbox, the camshaft, springs, and ecu.
Because they are totally different story.

Prime dudes, please let me know your thoughts.
(FYI, a fair condition MT nsx costs around 1m usd here, and a AT nsx costs around 50-55K)

91-94 all have the exact same chassis regardless of transmission. 95-96 Targas have a reinforced chassis through the B pillars and side sills using thicker aluminum extrusions. Again regardless of trans. 97-05 have the same reinforced chassis as the 95-96 Targas, regardless of trans and regardless of coupe or Targa. They also use lighter body panels compared to the 91-96 cars.

Your tech is wrong. I fully swapped my 92 to MT including the cams and valve springs. Changing the ECU is as simple as cutting a single resistor and boom you have a MT. Unless you change the valvetrain I recommend keeping the AT ECU setting.

 

[stevecct]

91-94 all have the exact same chassis regardless of transmission. 95-96 Targas have a reinforced chassis through the B pillars and side sills using thicker aluminum extrusions. Again regardless of trans. 97-05 have the same reinforced chassis as the 95-96 Targas, regardless of trans and regardless of coupe or Targa. They also use lighter body panels compared to the 91-96 cars.

Your tech is wrong. I fully swapped my 92 to MT including the cams and valve springs. Changing the ECU is as simple as cutting a single resistor and boom you have a MT. Unless you change the valvetrain I recommend keeping the AT ECU setting.

Yes I've read your Type S thread too, truly inspiring.(R04 resistor theory!)
So I can assume 91-94 chassis are the same no matter which model

 

[Honcho]

Yes I've read your Type S thread too, truly inspiring.(R04 resistor theory!)
So I can assume 91-94 chassis are the same no matter which model

Correct.

 

[MaxGeek]

Again regardless of trans. 97-05 have the same reinforced chassis as the 95-96 Targas, regardless of trans and regardless of coupe or Targa.

If you are saying 97-05 coupe has the thicker frame rails of the targa, I think this is still a debatable topic and I don't think it's the case. The coupe is still the ~100lbs lighter which suggest it didn't get all the chassis reinforcements.

 

[stevecct]

If you are saying 97-05 coupe has the thicker frame rails of the targa, I think this is still a debatable topic and I don't think it's the case. The coupe is still the ~100lbs lighter which suggest it didn't get all the chassis reinforcements.

But do you think all the coupe remains the same chassis?

 

[drew]

Better question : Are all production NSX chassis effectively the same between AT and MT?

Answer: Yes

Real problem: The MT parts are getting scarce, gone and going out of production.

FWIW some guy in S Africa has used an Audi DCT paddle shift transmission in the NSX. Between something like that and EV conversion is where the NSX is headed.

Where are you located? HK.

 

[stevecct]

Better question : Are all production NSX chassis effectively the same between AT and MT?

Answer: Yes

Real problem: The MT parts are getting scarce, gone and going out of production.

FWIW some guy in S Africa has used an Audi DCT paddle shift transmission in the NSX. Between something like that and EV conversion is where the NSX is headed.

Where are you located? HK.

check email lol

 

[stevecct]

91-94 all have the exact same chassis regardless of transmission. 95-96 Targas have a reinforced chassis through the B pillars and side sills using thicker aluminum extrusions. Again regardless of trans. 97-05 have the same reinforced chassis as the 95-96 Targas, regardless of trans and regardless of coupe or Targa. They also use lighter body panels compared to the 91-96 cars.

Your tech is wrong. I fully swapped my 92 to MT including the cams and valve springs. Changing the ECU is as simple as cutting a single resistor and boom you have a MT. Unless you change the valvetrain I recommend keeping the AT ECU setting.

He used EK4 and EK9 as the example, which makes me confused.
Because its a different story.

 

[Honcho]

He used EK4 and EK9 as the example, which makes me confused.
Because its a different story.

The Civic platform has nothing to do with the NSX. Two completely different cars.

If you are saying 97-05 coupe has the thicker frame rails of the targa, I think this is still a debatable topic and I don't think it's the case. The coupe is still the ~100lbs lighter which suggest it didn't get all the chassis reinforcements.

There was only one production line in Tochigi and there was only one stamping/extrusion panel setup for the side rails and b pillars. Honda didn't do it specifically to make the coupes stiffer- they did it to streamline production of a very low-rate unit. No reason to run two stampings when you're only turning out ~200 cars per year. The entire reason they made all of the exterior body panels thinner/lighter was to offset the extra weight from the reinforcement. Still, you may be right that the coupes didn't have all of the Targa-specific stiffening- there may be additional welded-on bracing that is omitted from the coupes. But the chassis is the same. The T-top is considerably heavier than the coupe roof panel, for example.

 

[MotorMouth93]

Just wondering are all NSX chassis the same? (In terms of the overall structure, rigidity etc)
From the oldest 1991 normal NSX to the newest 2005 NSX
From the normal to the high-end model Type R/NSX R

My technician strongly disagreed with me doing the manual transmission swapping (from AT to MT)
He thinks the chassis, and engine are different.
I never can turn an AT nsx to "MT nsx", even swapping the gearbox, the camshaft, springs, and ecu.
Because they are totally different story.

Prime dudes, please let me know your thoughts.
(FYI, a fair condition MT nsx costs around 1m usd here, and a AT nsx costs around 50-55K)

That sounds like a guy you don't want doing the swap. You can absolutely turn an AT into an MT, just by swapping those parts you mentioned and you won't be giving up anything as far as performance goes. A lot of people don't do the engine mods and that works just fine too, but OEM valve train parts are really cheap used (I have some I would give away for the price of shipping) and OEM M/T cams can be had for $1000-1500ish.

 

[MaxGeek]

There was only one production line in Tochigi and there was only one stamping/extrusion panel setup for the side rails and b pillars. Honda didn't do it specifically to make the coupes stiffer- they did it to streamline production of a very low-rate unit. No reason to run two stampings when you're only turning out ~200 cars per year. The entire reason they made all of the exterior body panels thinner/lighter was to offset the extra weight from the reinforcement. Still, you may be right that the coupes didn't have all of the Targa-specific stiffening- there may be additional welded-on bracing that is omitted from the coupes. But the chassis is the same. The T-top is considerably heavier than the coupe roof panel, for example.

This is certainly a topic of much debate over the years. I think I believed both sides at some point, but here is why I now believe the 1997 coupes do not have most of the targa reinforcements like the frame rails and etc.

The coupe and targa have different part numbers for frame rails in the parts catalog.
1999 Targa L side sill - 65190-SL0-T11ZZ
1999 Base L side sill - 65190-SL0-A02ZZ

1996 Targa L side sill - 65190-SL0-T10ZZ
1996 Base L side sill - 65190-SL0-A01ZZ

I think we've all seen the photos of the frame rail that shows how much more material the targa has. The targa rails should weight significantly more. I will get back to the weight debate later though.

The A and B-Pillars are different as well. The parts diagram shows that the roof line is part of the B-Pillar on a coupe and the targa doesn't have a roof. The A-Pillar also has an extra bit of windshield frame on the targa.


Note: It's not just the outer A and B pillar, it's also the inner piece that is different.


The 97+ did get lighter exterior body panels to offset the weight of the Targa reinforcements. Both Targa and coupes benefitted from this and the body panels do have the same part numbers. So **if** the 97+ coupes did get the targa chassis reinforcements wouldn't that mean that the coupes became heavier and the weight difference between a coupe and targa should be smaller? That doesn't seem to be the case though.

1997 - Source

Curb Weight	Coupe	NSX-T
Manual Automatic	3069 lbs (1392 kg) 3113 lbs (1412 kg)​	3164lbs (1435kg) 3208lbs (1455kg)​

95lb difference between a coupe and targa

1996 - Source

Curb Weight	Coupe	Open Top
Manual Automatic	3047lbs(1382kg) 3113lbs(1412kg)	3142 lbs (1425kg) 3208 lbs(1455 kg)

Same 95lb difference between a coupe and targa

Well maybe the 95/96 coupes also got the targa reinforcements?

1994 - Source

Curb Weight

Manual: 3020 lbs (1370 kg) Automatic: 3109 lbs (1410 kg)

That doesn't seem to be the case either because a 1994 coupe (manual) is only 27lbs lighter than a 1996. That can be explained by the addition of EPS on most manual cars for 1995+. Also if we look at the automatic cars which always had EPS the weight difference is only 4lb (1994 vs 1996).

So that's why I think the 1997+ coupes did not have the targa chassis reinforcements. I think this is similar to the rumor that 2002+ all had NSX-R motors. The belief behind that was also "streamlining the manufacturing process."

 

[stevecct]

That sounds like a guy you don't want doing the swap. You can absolutely turn an AT into an MT, just by swapping those parts you mentioned and you won't be giving up anything as far as performance goes. A lot of people don't do the engine mods and that works just fine too, but OEM valve train parts are really cheap used (I have some I would give away for the price of shipping) and OEM M/T cams can be had for $1000-1500ish.

yes i remember around 400 per MT cam

 

[stevecct]

from some japanese magazine.
① High strength, high rigidity extruded side sill.
②Front side frame that efficiently absorbs front collision energy.
③ Highly rigid center pillar fixed to the main frame.
④Large-section, high-strength rear frame that protects the fuel tank in the event of a rear collision.
⑤ Highly rigid ultra-fine pillars made by arc welding.
⑥Double partition glass that improves body strength and rigidity and is effective in insulating heat and sound from the engine room.
⑦ Improved repairability in the event of a light collision by making the outer panel an assembled component.

Seems Honda had put their best afford since 1991 first production year of NSX

 

[Zoom]

Didnt they change the alloy used to build the chassis from 1997+ ? That also would account for some difference even between coupe models of different years...

 

[stevecct]

Didnt they change the alloy used to build the chassis from 1997+ ? That also would account for some difference even between coupe models of different years...

Or the same structure, but the "ingredient" of materials is slightly different?!
That would be another topic.
Let's make it simple.
Now I assume Gen1 type r coupe chassis = gen 1 MT coupe chassis = gen 1 AT coupe chassis

 

[Zoom]

It's supposed to be a stronger, lighter aluminium alloy, there's some litterature on this topic right here on Prime, cant remember where.

 

[MaxGeek]

Didnt they change the alloy used to build the chassis from 1997+ ? That also would account for some difference even between coupe models of different years...

Yes they moved to a stronger aluminum. I was under the impression that this primarily applied to the body panels only as a way to reduce weight for the weight adding changes the car has had over the years. However as the NSX is a semi-monocoque design so the body panels play a role in the rigidity of the car.

• New aluminum alloy in selected body areas to reduce weight and increase rigidity

Changes by year

From the wayback link posted above: Changes for 1991 First model year for the car Engine model number is C30A Changes for 1992 New Color: Grand Prix White Changes for 1993 Added cup holder to center console; console cover got two separate openings. Added Passenger Side Air Bag Changed...

www.nsxprime.com

 

[Honcho]

This is certainly a topic of much debate over the years. I think I believed both sides at some point, but here is why I now believe the 1997 coupes do not have most of the targa reinforcements like the frame rails and etc.

The coupe and targa have different part numbers for frame rails in the parts catalog.
1999 Targa L side sill - 65190-SL0-T11ZZ
1999 Base L side sill - 65190-SL0-A02ZZ

1996 Targa L side sill - 65190-SL0-T10ZZ
1996 Base L side sill - 65190-SL0-A01ZZ

I think we've all seen the photos of the frame rail that shows how much more material the targa has. The targa rails should weight significantly more. I will get back to the weight debate later though.

The A and B-Pillars are different as well. The parts diagram shows that the roof line is part of the B-Pillar on a coupe and the targa doesn't have a roof. The A-Pillar also has an extra bit of windshield frame on the targa.

View attachment 183828
Note: It's not just the outer A and B pillar, it's also the inner piece that is different.


The 97+ did get lighter exterior body panels to offset the weight of the Targa reinforcements. Both Targa and coupes benefitted from this and the body panels do have the same part numbers. So **if** the 97+ coupes did get the targa chassis reinforcements wouldn't that mean that the coupes became heavier and the weight difference between a coupe and targa should be smaller? That doesn't seem to be the case though.

1997 - Source

Curb Weight	Coupe	NSX-T
Manual Automatic	3069 lbs (1392 kg) 3113 lbs (1412 kg)​	3164lbs (1435kg) 3208lbs (1455kg)​

95lb difference between a coupe and targa

1996 - Source

Curb Weight	Coupe	Open Top
Manual Automatic	3047lbs(1382kg) 3113lbs(1412kg)	3142 lbs (1425kg) 3208 lbs(1455 kg)

Same 95lb difference between a coupe and targa

Well maybe the 95/96 coupes also got the targa reinforcements?

1994 - Source

Curb Weight

Manual: 3020 lbs (1370 kg) Automatic: 3109 lbs (1410 kg)

That doesn't seem to be the case either because a 1994 coupe (manual) is only 27lbs lighter than a 1996. That can be explained by the addition of EPS on most manual cars for 1995+. Also if we look at the automatic cars which always had EPS the weight difference is only 4lb (1994 vs 1996).

So that's why I think the 1997+ coupes did not have the targa chassis reinforcements. I think this is similar to the rumor that 2002+ all had NSX-R motors. The belief behind that was also "streamlining the manufacturing process."

This is really, really good and I think you might be on to something. I think the gap is whether other Targa-specific parts could explain the weight difference. Does the T-top and revised engine cover, for example, make up the difference, or is there still more left?

 

[Gansan]

If you are saying 97-05 coupe has the thicker frame rails of the targa, I think this is still a debatable topic and I don't think it's the case. The coupe is still the ~100lbs lighter which suggest it didn't get all the chassis reinforcements.

The NA2 coupe doesn't have all the reinforcements of the targa, but it does have some of them. Digging back in my Google docs, I translated a Honda advertisement for the NA2 NSX Type S which contained copy written by Motoharu Kurosawa.

WHY CHOOSE THE NSX

docs.google.com

(I am to blame for the janky wording.)

He said:

This driving feel is not something that could ever have been accomplished by just the latest technological advancement alone. The NSX is constantly improving. The 97 NSX's large jump in performance, in addition to the improved torque, 6 speed transmission, and tuning, is also the result of the introduction of the 95 Type T with its improvements in chassis rigidity.

I can probably also dig up a Japanese book that gives more detail but that would require me to go searching in the closet.

 

[stevecct]

The NA2 coupe doesn't have all the reinforcements of the targa, but it does have some of them. Digging back in my Google docs, I translated a Honda advertisement for the NA2 NSX Type S which contained copy written by Motoharu Kurosawa.

WHY CHOOSE THE NSX

docs.google.com

(I am to blame for the janky wording.)

He said:

I can probably also dig up a Japanese book that gives more detail but that would require me to go searching in the closet.

so basically in terms of chassis rigidity is not differentiated by coupe/type r, but by the year of making