I thought I would document my STU build for your enjoyment or hopefully use the info for your build.

A little about the car:

• 2003 Performance
• I bought it new in Jan 2003
• Currently has about 35K miles on it
• Used it primarily for fun trips, up and down the coast – Florida Keys to Quebec Canada.

I wanted to do something with it other than a touring car, ---> club racing. However, life (job & family) kept me busy, in addition to other projects. End of 2013 the rear differential bushing cracked. That was the push I needed to finally do something with the car. But not right away. I spent 2014 researching, including SpecZ, BSP, STU, etc. In the end STU looked to be the best option for me.

I’ll go through the 2014/2015 build and what’s going on this winter,

• Suspension
• Differential
• Engine
• Interior
• Brakes
• Other

but for now some pics of the car.

 

Love that LeMans Sunset color! Looks like a well-cared for example that'll do well in autocross. Do you run in local events, or the National Tour?

 

Thanks! I did only regional events in 2015, 22 of them. I already planned 7 to 8 National events in 2016. However, that could change depending on my travel schedule.

 

This is where I did the most amount of research, calls, calculations…. not only because it would be the single largest $$ purchase, but (aside from tires) it would be the most important performance gain/loss (maybe). My goal was to have a nationally competitive car by 2016 with a limited budget (hahaha, yeah I know).

Anyway, I narrowed by considerations to Koni, Bilstein, KW, Ohlins, Sachs, JRZ, Moton. From what I remember:

Koni Sport (Yellow)
Plus: inexpensive (relatively of course) especially if you piece the coilovers together yourself (multiple DIY instructions). Proven and used by many. Multiple shops that will do a good job with custom valving.
Cons: Single adjustable, may not handle the high spring rates as well, heavy’ish

Koni 28 Series
Plus: great performance, proven with others, multiple shops what will custom valve and dyno.
Cons: expensive

Bilstein B16 (PSS10)
Plus: great performance, affordable, and comes as a complete kit. Can be custom build for $100 per damper.
Cons: Single adjustable.
Bilstein’s engieer told me they have no double adjustable solutions for the Z. Maybe there are 3rd parties that will design and build adaptors for the Z, but I didn’t go that far.

KW Clubsport
Plus: Complete kit, out of the box spring rates of 855 lbs/in front and 455 lbs/in rear and both springs hold a 61mm ID. I believe they said the dampers will work with +/- 200 springs. You can get a great price from Nismo with the SpecZ kit.
Cons: questionable performance.

Penske 7500
Could not find a solution with these shocks for the Z.

Penske 8300
Plus: great proven performance.
Cons: expensive, have to assemble / find the remaining shock / spring supports.

Ohlins, Sachs, JRZ, Moton
I remember researching these, but they were all out of my price range.

I decided to buy the Penske 8300. To be honest I knew some people at Penske and their shop is close by. I picked up the shocks ready to go to fit the Z and custom valved from Penske. I got to see them build and dyno one of the shocks which was interesting.








I know the spring rates I wanted to use, so on to buying springs, and figuring out what mounts to use.

 

Call me jealous on the Penskes. I'm using the KW's which are great for the first 25 minutes on track.

 

Baller!

 

Another build, awesome!

So are the Penskes at a lower price-point than the JRZ DAs? I guess I need to do some research on them, I've just always thought Penskes were the most expensive option on most platforms.

quick edit: Can you elaborate on why there isn't a 7500 option for the Z? An aluminum bodied DA Penske for ~$565/shock is highly appealing.

 

You may have to do the research. I don't remember since it was 1 and a half years ago since I did the research and I didn't pay retail for the Penskes.

7500 option: Penske didn't have a design for the Z. I agree the price is great. If you could find someone that made an adaptor kit it could be the way to go. For me it didn't make sense to get the shocks and pay addition $$ for a custom setup.

 

The front setup was a little more involved than the rear. The Penske shock rod adaptor was designed to work with the Nissan OEM top mounts. However, I didn’t want the top of the spring in contact with the top shock mount like the OEM (or many other coilovers) since this would introduce rod side loads, potential spring bind. My plan was to use the Penske top spring retainer (Item 7).




Which means I couldn’t use the OEM top mount since it was not designed to take full corner loads via the rod alone. I needed to find a new top mount and I wanted a Pillowball bearing. I contacted many potential suppliers, SPL, Cusco, Megan, BC, and race shops. They didn’t have what I wanted in terms of strength, quality, or just cost way too much. I was eventually referred to a fellow competitor who designed and made his own top mounts. Pretty!




And I can replace the bearing easily when it wears out. These bearings were not meant to take force axially. BTW, my front dampers were made about 2 inches shorter then OEM and I don’t need to use a helper spring and adaptor.

Shock assembly. I decided to start with a 1200 lbs/in spring force and a Koyo thrust bearing and races at the bottom of the springs. I went middle of the road and bought Hyperco springs 8in length, 2.5in ID. I assembled everything together and immediately realized I had a problem. This was the car at full droop.




I didn’t check to see that these top mounts were designed for a different shock length and the mounting point was about 1 inch higher then OEM. Thankfully after some measurements,



I was able to get a local machine shop to make me new bushings that adjusted the shock down .7in. Done.



I also made artistic use of zip ties for the ABS sensor and brake lines. Temp solution that remains today. Eventually I'll just replace them with new zip ties when they harden from heat and age.



I didn’t have time to fab up any special brackets for the reservoirs. So I just ran the lines into the engine bay and into the battery and brake compartments. Wrapped them in foam to stop them from getting damaged or damaging anything else.




It was meant as a temporary solution, but I still run it this way. One plus is that they are not heated by the engine and I measured them to have considerable lower temps the other items under hood.

 

Are you running the rear springs on the coilovers or do you have a stock style spring seat? Just asking because I thought we had to keep the stock spring location until SM.

Please correct me if I'm wrong, as I'm looking at different coilovers and some are labeled as a true coilover in the rear, which I don't believe to be legal (ESP in my case).

another sweet STU build here...

 

Thanks! Yes, you have to use the stock spring location. I'll post my setup next week hopefully. Wanted to take some new pics first. The Penske's can be setup as true coilovers, but as you said not allowed under SCCA rules.

 

What he said

 

Up front the ABS wire and brake lines are held that way on my car for years now. My front reservoirs are actually in the same place too. I figure the reservoirs have great crash survivability there, and really low heat.

 

Who made the upper mounts?

 

Mark DeShon. His car won STU this year at Nationals with Jeff Stuart driving.

 

The rears setup was relatively straight forward. Since the rear damper was standalone (not coilover) I decided to use the OEM top mount. The bottom bracket of the damper is thicker than the OEM damper, so it just needed a longer bolt. I decided to use the Penske bump stops, but shortened and resting against a large “washer” bolted between the damper rod and the rod-to-top mount adaptor.




On the driver’s side I made a bracket to tie the oil reservoir line against the car body. The aluminum bracket is held in place by an unused welded stud. Finally I wrapped the hose in a larger plastic hose. The plastic hose allows the line to slide during suspension compression and extension. It also protects it from the tire slightly rubbing against it in compression and side load. On the passenger’s side, I just tucked it under the plastic shield protecting the fuel filler hose.


The reservoirs are mounted behind the differential on the rear pin stay. Using dense foam, I cut out 2 brackets or seats for the reservoirs to sit in so they don’t hit the pin stay or each other. Then secured everything with large zip ties. Not ideal, but it works and the compression adjustor is easy to get to.





The rear springs adaptors are from BC Racing. Megan has very similar (look identical to me) adaptors and slightly cheaper. However, Megan was out of stock and with a 3 month back order, so BC Racing Hi-Lo kit it was.




I replaced BC’s plastic bottom spring ring with Koyo thrust bearings. I also used the OEM bottom spring rubber seat like Z1NONLY. I know the rubber here and in the top mount introduce some nonlinearity, but I doubt I'll notice. My rear dampers are 3.25in shorter then OEM, so I do not require a helper spring or seat. Currently, the spring has a minor amount of preload. The rear spring is 6in by 2.5 ID. The small problem with this setup, as far as I can tell, is the spring is loaded unevenly during suspension travel on a relatively short spring. But no better choices.

 

Subscribed! Did you put your Berks in yet?

 

All done! Not sure if I have to glue some heat barrier to the firewall/underbody since these cats don't have heat shields.
Just waiting for Motordyne y-pipe now and the exhaust will be done. Well other then replacing headers.

My analytical side says the 5-8hp gain from headers does not justify $700, bloody knuckles, and hours to bolt them in. I know improving my driving will gain me far better results.

Then again, I was just looking up Stillen headers this morning. The heart wants what the heart wants.

 

So true, my heart wants alot on my car. Momma(wifee) just tells me no most of the time....lol. Although she did just let me order my RJM pedal assy. Can't wait to receive and install.

 

Oh btw, thought I had already commented on your thread but hadn't. Great build. Car looks great.