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

Front Tower Bar: Had to get the NISMO Titanium one, of course!

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...

Trunk Bar: Another Noticeable Improvement in Body Rigidity

As I wait for a part I need to finish my extra mod for the BNR34 diffuser to arrive (so I can do my true last post on the diffuser install), let me also showcase something ELSE I had done at BeAmbitious, and the real reason it took over a week to get the car back to me.

So during my research into the mechanical differences between the R33 and R34 GT-Rs, other than aerodynamics, the other area where the R34 improved upon the R33 was in body rigidity.

This makes sense, I believe my car is a much better handling car since the addition of various NISMO underbody brace bars, and especially the Nagisa Auto fender brace.

Now the Series 3 has additional bracing in the trunk, but that is in the front of the trunk area - between the struts towers and the rear wall framing where the battery is located.

And this is a result most likely because the BNR34 was being developed during the run of the R33 and in fact the BNR34 test beds were modified R33s. So likely, these braces were an improvement that was discovered during the BNR34 development, and incorporated into the later R33s.

There was one improvement that isn't that well advertised or known, and that is the brace bar in the trunk of the R34.  Not sure why this didn't make it into later R33s, as it is an easy piece to add, however this brace bar concept DID make it into certain models of the S15 Silvia.

So when I began my search for a used piece, I was able to find one in decent shape off of an S15. I had also read on Minkara of another R33 GT-R owner (and also a few ECR33 and even ER34 owners) who had installed an S15 trunk brace bar without issue, so rather than searching for a BNR34 one, I picked up one of the more easily available S15 ones.

When it arrived, it was in good shape, with some scratches, presumably caused by items in the trunk!

But as I had some leftover KR4 silver paint from my fluidic nozzle project, I used that and sprayed the entire bar to get it as nice looking as possible. Turned out ok, I think:

I let Ninomiya-san of Be Ambitious take care of the install while I left the car with him in order to install the R34 V-spec rear diffuser. It turns out that there are already holes pre-drilled in the trunk in the right place (under some rubber caps), however what needs to be taken care of is to have something fill the gap between the floor and the bumper reinforcement, which also has holes pre-drilled. (Apologies but since I did not do the install I don't know what size bolts...). For my car, Ninomiya-san had some billet anodized aluminum spacers custom made (not cheap), but it is obviously more solid than what people usually do, which is to stack washers one on top of each other to fill the gap. And getting these spacers made took over a week and hence the delay in getting my car back to me (I thought the diffuser and trunk bar install would take a day or two, but it ended up taking a week).

EDIT - Mook on the UK GTROC forum did this mod - here is a link to some GOOD installation photos and information on the bolt and spacer sizes.  Thanks to both Mook for the photos and K66 Sky for the information.

Anyway here is how it looks now, installed.

And here is close-up of one side, bolted in:

Now what about the result? Did it change the car? In a word, "yes!" Definitely!  On my way home after picking up the car, it's only a few kilometers, but immediately the car felt "shorter" - I know that sounds odd but that is the best way to describe it.

Later, I took a 2 hour drive into Tokyo, and discovered that, in addition to the car feeling shorter, the suspension seems much stiffer now. What was before a firm but pleasant ride is now on the verge of being a bit too harsh!  So unless this is a placebo effect, I guess my senses are telling me that, before the trunk flexed and allowed the dampers to feel softer - now as the trunk area is more solid, the dampers don't have as much "give"... at least that's my theory.

Any thoughts, my friends? Am I imagining things? I think I am going to continue making the body as rigid as possible without the use of a roll cage, until the car feels like it's carved out of one solid block of steel. I will look into spot welding, but have heard that rusting can be an issue, so I may just have to see what else is out there that is bolt-on.

Interim Post – Some Recent Random Observations

Gentle readers, as I finally had a day off from work (national holiday today when I wrote this - Friday the 24th), I just wanted to post a few recent thoughts and observations involving my car that I had as they are all on scattered topics (not worth writing about alone), all in one writing.

Remember this install? The Nagisa auto brace:

While I was able to feel a difference immediately, I assumed that this type of brace was used only on older cars that were probably designed before automakers had access to supercomputers and hence could be improved upon with a simple bolt on.  But look at this, which I recently found in a current model year catalog for the Lexus GS cars:

Yes that’s right – an almost identical brace, in the same location! Presumably, supercomputers also agree that an efficient way to improve body rigidity even in today’s cars is by way of this type of bolt on brace. Amazing.

Going even further back – I had installed these underfloor aerodynamic devices

Daytona Ground Effectors. As I recall the car felt slightly more planted with them installed. Unfortunately with the addition of some underfloor Nismo bracing, these Effectors had to be removed as they used the same mounting points, but I continued to wonder what could be done to help airflow under the car.

Looking at this photo – taken from the same Lexus catalog as the photo above – shows that modern cars also use under chassis aerodynamic tweaks in order to improve airflow. Interesting. I’m sure that Toyota spent lots of money and lots of wind tunnel time to perfect these under chassis bits, making them minimally intrusive while maximally effective.  As I obviously I can’t replicate this on my car (unless someone wants to lend me a wind tunnel and a computer or two), I think the Ground Effectors may be the most cost effective way to go. So, I may have to rethink about their placement under my car.

Finally, I’m happy to report that I was finally able to take the car out for a full blast run, including a quick high speed run on the expressway, to test out the full breadth of the Okada Plasma Directs.  

In a word, awesome.  There is definitely a difference in how the car accelerates. Yes there is more power off the line, and also the engine revs up more smoothly and there seems to be more torque throughout the entire RPM range.  Not only could I tell there was a difference, it was enough of a difference that the new found acceleration was addicting, I was lucky not to get a speeding ticket that night.  Of course, part of the difference in engine performance might have come from the Tomei exhaust (which I uncorked) as well as the colder than usual air, but this would explain only part of the difference in response I think. So as I said before, a worthwhile addition, however get all of the other engine mods done first!

So what's next? Stay tuned...

Nagisa Auto Gacchiri Support

After my recent research into what mechanical changes Nissan had made to the R34 vs the R33, and finding that basically, other than aerodynamic improvements, a lot of effort was put into improving body rigidity, I began to think about what I could do to improve the rigidity of my car.

Granted, it’s a Series 3 so there already is additional factory bracing in the rear trunk area, and I have already installed the Nismo underfloor bracing (both front and midsection), but what else is there?

Obviously, a roll cage is one solution, but I want the solution to be invisible. I have heard of foam that you pour in that hardens when it dries, but I have also heard that it can trap moisture, leading to rust, and that if not done properly it can, upon expansion, distort the sheet metal around it! Also, some people point out that it could cause the body to act in weird ways during a crash.

Spot welding is another option, but that of course should be undertaken with a full repaint, if you want to do it properly (although I will be looking into this).  So, my choices at the moment are limited to bolt on braces.

I searched on Minkara, the popular Japanese car-related website, in their “Parts Review” section (where readers post their reviews of parts), and found one part that received universal praise, and almost always the full 5 stars (out of 5 stars).  The Gacchiri Support from Nagisa Auto. Nagisa Auto is an Osaka based tuner that specializes in various small parts, but mostly suspension and body rigidity items.

“Gacchiri” in Japanese means “solid.”  The Gacchiri Support is a triangular shaped (patented!) fender brace that gets fitted on the door hinges area extending forward to the top part of the inner fender.  When the package arrived, I took out one side for a photo:

Here is the Nagisa Auto link for this brace
http://www.nagisa-auto.com/products/gacchiri/index.html

And for Nissan cars: http://www.nagisa-auto.com/products/gacchiri/nissan.html

MINKARA Parts Review on the Gacchiri Support

Also there are some better photos of how it looks installed (apologies for no photos here as my tuner installed it and I was not around...)

Anyway, I’ve only driven the car a short distance, that is back from my tuner. And yet, in the few kilometers back home, I DID feel a difference. It’s somewhat hard to describe, but basically, the car feels more responsive to steering input, and strangely, it feels smaller.





This weekend I may be attending an event on a track, in which case I will be able to get a better feel for this, so will update in my next post!