Today at Atelier Kaz - ex-Honda R&D, F1, Indy/CART engineer

On several occasions, I was asked about the chassis stiffness between different NSX models and also about some of the well known modification to ‘stiffen up’ the chassis that ‘seems’ to sharpen the handling.


Followings are my personal view based on some test sessions carried out under several different conditions/timings at the twisty mountain road, a certain circuit and normal A-road in Japan.


There are lots of different concept for the chassis setup and the driving condition is quite different from yours so inevitably, you will have different view and also something didn’t work for me may be fine for you and vice versa.


The difference in human factor (sense, feeling, driving style, etc) will play a big role as well.


For example, lots of owners mentioned about negative view on the power steering (EPS) on NSX.

Going through the twisty (continuous repeat of almost 180deg turn) mountain road even for just 20min or doing just 5 set of 3 timed laps on a certain circuit, I love to have EPS on the NSX.


For the twisty road, we used to go really deep into the corner and used the side edge of the gutter to gain some extra camber.


So, most of the drivers with this style will have lots of scuffing marks on the wheels.

If you have a chance to look at my wheel, you’ll see lots of marking on it.

(As a side note, when I first went for NSXCB event, I was quite surprised with the amount of UK NSX owners who refurbished their wheels.)


These are just a few points to highlight the potential difference between you and me.


So, here we go.....


Recently, there was some discussion about the body stiffness between NSX-T and Coupe models.

There are several different ways on how to evaluate the ‘stiffness’ based on the angle/direction, frequency/speed, etc of the input energy.


Also each manufactures have different method to express their view on this topic so it’s not a simple task.


Any reinforcement will change the natural/resonance frequency of the parts and depending on the structure and assembly method, there could be 2nd, 3rd, … order frequencies as well so without the help of computer, you are not going to be able to tell the actual amount of changes.


At the same time, something calculated by the computer doesn’t mean that the human body/sense will feel the reinforcement in the same way as the simulated data.


So, for the first stage of the NSX-T development, Honda actually cut off the roof section of the earlier coupe model and took it onto the proving ground.


The result was ‘moveable’ but not ‘driveable’ over the certain speed.


The input to the certain part of the chassis will come from all direction at different frequency, energy, etc and yet you are relying on to the small tyre contact patch that is the size of the palm at each corner for the dynamic movement.


So, in order to put ideal load to the contact patch during the synamic movement, the chassis reinforcement study was started and at the end, there were more than 50 points reinforced as well as some changes to the internal aluminium structure.


Something looks the same as the coupe model from outside doesn’t mean the same structural stiffness on the NSX-T.


The end result was the targa design that can be used on circuit track with similar chassis stiffness as the earlier coupe models.


The R&D process of NSX-T contributed to the improved chassis stiffness on the later coupe models.


Therefore, if you compare the NSX-T to the later coupe models, yes, the stiffness is lower but similar to the earlier coupe ones.


Unless someone is comparing the NSX-T against the later coupe model, most of the claim as ‘NSX-T is softer than the coupe’ is the feedback through the softer suspension setup and the aftermarket tyre used.


For the production car, is stiffer better???


Any force/energy into the chassis parts will result in counter force and somehow you need to damp it to eliminate the energy.


Stiffening the chassis and damping the energy is a different matter but the aim is to achieve ideal load at the contact patch.

(By the way, if you want, you can read the paper on J-damper developed at Cambridge Uni here;

http://www-control.eng.cam.ac.uk/Hom...ontrol_859.pdf

While J-damper is using the flywheel to store and apply kinetic energy against the input energy, mass damper is also using the inertia effect of carefully calculated weight on spring to compensate the ‘bouncing’ vertical movement of the chassis.)



When Type-R was introduced, there were lots of strong recommendations on several forums to install the Type-R Front and Pivot bars and Type-R Front anti-roll bar.


Later, when Type-S was introduced, there were lots of praise for the changes made by installing the Type-S Rear anti-roll bar as well.


There was even some home made suspension tower bars discussed.


As we had access to all sorts of parts and thanks to some of the NSX owners, we tested these claims on several occasions.


We tried several different combinations of the parts back to back and as the result, the first thing to be removed from the standard coupe was the Type-R front anti-roll bar.


For my driving skill, I just couldn’t shift enough weight to the front tyres especially at the twisty mountain road.


Probably good modification for the skilled driver but not for the ordinary driver like me as it was understeer every where.


The Type-R Front and Pivot bars changed the natural/resonance frequency of the front section of the car.


This made the steering 'feel like sharper’ under some driving conditions but at the same time, I didn’t like the way the front tyre moved (or jumped) on some of the surface and also there was more vibration felt through the steering wheel.


I like to feel the road surface through the steering wheel but this extra vibration was somewhat disturbing the information.


Similar feed back was made from the driver of the tower bar equipped NSX.


I didn't like the idea of using the tower bar any way so didn't try it and only listened to my trusted driver's feedback that is good enough for me.


So, next to be removed from this NSX was both the Type-R Front and Pivot bars.


By the way, I was asked about the reason on why Honda didn’t put these two Type-R bars on other models and although I don’t have the definite answer, I think above fact is one of the reason for this.


At Honda, NSX was built around the human-machine interface and for standard NSX model, the human sense/feeling comes first.


It was aimed for all sorts of drivers to enjoy driving this car.


Therefore, any uncomfortable vibration/noise were not ideal even it may contribute to the ‘sharper’ steering feel under certain conditions.


Similar to the reason why the Type-R damper-less clutch joint was not installed on other NSX models.


From Clutch bite point of view, using damper-less joint is much easier to feel the disc movement.


Combined with the Type-R clutch pedal, it felt as if all NSX should come with this setup.


However, it also introduced quite noticeable vibration through the pedal and again, it was not ideal from product quality point of view and thus, not installed on other models.