Wednesday, October 2, 2013

Can There Be Too Much Body Rigidity?

(Or, what I was actually doing at Do-Luck on my day off this past Monday)

So as I continue to bring my car up to more modern standards, one area where I have spent time, money, and effort recently, as readers have noticed, is in the area of improving body rigidity.

So far, I've attempted to add body rigidity to the following areas:
Rear trunk area (cross-wise):  S15 Trunk bar
Front fenders (longitudinal): Nagisa Gacchiri support
Front underfloor + steering rack (cross-wise), replaces standard front cross bar: NISMO Front Underfloor Reinforcing Bar
Center underfloor + rear suspension (cross-wise), replaces standard center cross bar: NISMO Center Underfloor Reinforcing Bar
The chassis and subframe: Spoon Sports "Rigid Collars"
Not exactly a “stiffening” part, but something that cancels out the excess vibrations caused by stiffening: NISMO Performance Dampers

This past Monday, I added one more - the Do-Luck Floor Support Bar!
Courtesy of Do-Luck RS webpage; Floor Bars (aluminum) shown on demo R34 GTR
While I thought that my body rigidity work was finished after I got the trunk bar installed, in the back of my mind, I had my doubts - was I doing the right thing? Were these reinforcement parts working in the additive sense - was having more rigidity everywhere, better? Or was I risking unbalancing the car?  After all, during my research into the differences between the R33 and R34 GT-R, there was some extra welding done in the C-pilllar, and the trunk bar, but nothing about fender and underfloor bracing...

And as you recall from my results after the trunk bar installation, the ride quality got much stiffer, in fact on the verge of being too harsh! So did I really want to further stiffen the car?

A while back I had called Ito-san at Do-Luck and asked him this question.  He believed that it would only benefit my car to tighten up the floorpan, that what I had done so far wasn't excessive. So, it was only a matter of time before, when I had a day off, I drove over to Do-Luck to get their Floor Bars installed.

They were waiting for me, so I had them pull my car into the workshop because... 
As you can see it was pretty crowded in there that day.
No way I'm taking responsibility if I accidentally run into something!
I spent most of my time while there talking to Ito-san about his latest product, the DTMII ETS Controller, (I volunteered to translate the manual, so he gave me some inside info as to how it work! I hope to share it here soon...) so did not watch as his staff installed these:

However the concept is ridiculously simple - using lightweight aluminum, oval shaped (in order to prevent excessive underhang) bars that bolt on to the underbody in 3-4 places. Here is an interesting tidbit - he found that some 33s had 4 mounting holes available (like my car) but others only had 3. Hence he ended up standardizing his bars to have 3 mounting holes, as can be seen in the photo above.  However, ALL R34s have 4 holes on the chassis, so the R34 bars all have 4 mounting holes... not sure if it makes a difference but it would have been nice just in case...
Close-up of rear of bar (looking towards front) showing how the NISMO brace fits OVER the Do-Luck one, no problem
Ito-san remarked that as he had developed these bars BEFORE even NISMO released their series of underfloor reinforcing bars - he had never seen the above scene before in person!  I couldn't believe it myself, but it was the first time he himself had seen that these two pieces fit without issue. Turns out that not many of his customers get their pieces installed at his shop, and I guess I was the first R33 with the NISMO pieces to do so...
Here is the front of the bar. You can see how there is a hook that ties it securely to the frame
 (prepped with anti-rust later, of course)
sorry for the blurred shot, but you can see how the bar runs along the chassis 
Anyway, based on my research I don't think there are any more aftermarket add-on parts available to improve body rigidity.  So I think I am done with this type of body rigidity improvement. When I have the time, I’d like to follow up on methods to stiffen the shell by way of either spot welding, or hardening foam (for example in the C-pillars, like the BNR34).

After the work was done, I then took a quick spin to Nissan Prince Shinagawa and visited their Motorsports Division to order some additional parts for some upcoming projects I have. You’ll have to check back in order to see exactly what I got….

But more importantly during the drive over, I could DEFINITELY feel that the Floor Support Bars had made a big difference, more than what I had expected. 

First, the harsh ride was gone!  I asked Ito-san about this, and he explained that the trunk bar had solidified the rear body and allowed the rear coilovers to work off of one solid base - so the left and right sides were unified, both front and rear.  However, with the longitudinal Do-Luck bars now installed, all 4 wheels were tied together, allowing the suspension to work off of one large, solid base.  Indeed the car feels more solid, more carved out of one piece. 

Second, the car felt shorter, and more nimble. It might be my imagination, but it seemed that there was a bit less "lag time" when making high speed lane changes, for example. Obviously I can't quantify it by saying it took 0.00000005 seconds less (or whatever) to respond, but there is definitely a difference in how the car feels. I recall this is the same feeling I had when I first had the Nagisa fender braces installed.  So perhaps front/rear rigidity improvements can be had with longitudinal bracing?

Sadly I got used to this improvement in feel after about 10 minutes of driving...and now I'm wondering if it makes sense to get the car spot welded where I can! In any case I'm actually looking forward to going for a spin soon...


マット said...

Oh! You've finally decided to install the Floor Support Bars!! Thanks for the detailed photos on the install.

I'm glad you felt the difference. You've convinced me to get these installed on my car. I hope installing these on a BNR32 will also be trouble free, ie. no drilling extra holes, fitment problems, etc.

aquila4889 said...

Interesting, I'm interested on you thoughts on the Super HICAS, is yours still working, personally I would not want a GT-R without HICAS, how does it feel with your incresed rigidity and work with your upgraded g-meter for your ATTESA ETS, etc?

Aki said...

マット、thanks for the comment.

aquila4889 - personally, I agree, without HICAS the second general GT-Rs are not GT-Rs. When I spoke to Ito-san at Do-Luck, he mentioned that it was not worth locking out or removing HICAS unless your car is huge power like 700+. Also, most people will not be able to tell the difference with the HICAS on or off.

So mine is still working. As for how it works with the increased rigidity, I could not tell but must assume it's more accurate now - perhaps this is why the car feels more nimble now? (I don't think my digital G sensor has much effect on HICAS though).

aquila4889 said...

it just had me thinking because i commented about one of you previous posts (ages ago now) and you replied at the time asking if the was anything I could think of that would make for an interesting read, and when u said how it made you car feel I thought "I know, "HICAS"

Aki said...

Well, despite what many say I will never remove the HICAS. I do wish however sometimes that the car had even sharper steering feel...

Michael said...

You could always track down a long discontinued Nismo rear upper strut brace. This requires cutting holes in the parcel shelf trim though which is something you may not want to do.

Aki said...

Hi Michael, thanks for the comment and the idea! Alas you are right, I don't like cutting the parcel board, and I also think it would intrude in the cabin too much. Also weren't these for ECR33s, without the stock rear tower bars?