Picking Shoes

In my winter boredom, I've had little to do but research, dream, and shop.One of the big draws about the 350z landing in STU is that it can fit ALL THE TIRE. The rule set specifically says that 2WD vehicles, be it front or rear, can use wheels of any size up to 11" wide, and wrap them with any tire 180 UTQG or higher.. up to.. and here's the big one.. 285mm wide.

This is a BIG tire.
Again going back to the rules you can use up to your maximum tire allowed, but you can't rub through fender liners and can at most roll fenders. No cutting allowed.

So, can you fit this much rubber underneath a 350z? Absolutely.

The back is zero problem at all.. people who go with staggered setups will often put 315s or 325s and they fit fine with a little extra camber. A 285 on the back is a no brainier. The front on the other hand, that gets a little more tricky. a 285 is pushing the upper limits as to what can slide under the front fenders.

When the rule set came out, I was looking high and low for anyone who had been putting such rubber on the front of the z.. a lot of 265s, hearsay, and pictures with very little info. I had remembered years back that the magazine Sport Compact Car had done a non-staggered setup with some big rubber. I knew I'd never find that particular copy of Sport Compact Car again, but maybe someone had put it online?

Well, if hell hasn't just frozen over. It looks like a lot of the content of Sport Compact Car was consumed by Modified Magazine. The Article is Project 350Z Part 2: Balance. It's complete with tons of detail I came to expect of SCC back in the day.. Tire sizes, wheel sizes, offsets and any spacers used.

[caption id="attachment_35" align="aligncenter" width="300"] Oooh... that looks nice[/caption]

[caption id="attachment_36" align="aligncenter" width="300"] Just Clears, but I don't need much room. the wheel is static to that point.[/caption]

[caption id="attachment_37" align="aligncenter" width="300"] This picture pretty much exactly what i was looking for... i just wish it was a bit lower so i could see the wheel clearance.[/caption]

 

So, now I know that a 275/40-18 tire fits on an 18x9 wheel with an effective offset of +30mm, and I know that there's very little room to further bring the tire inboard. Using this info, I can crunch some numbers, or use yet another handy online calculator, like this one: 1010Tires wheel offset calculator. So I had something to start looking and sizing, but nothing beats finding something confirmed. I knew I'd be looking for 18x10.5 or 18x11" wheels.. so the crawling would continue.. not like I have to buy wheels right now, right?

So, I managed to find a hit on a 350z wearing 285s all the way around.

[caption id="attachment_41" align="aligncenter" width="300"] Oh My...[/caption]

 

The car is running on 285 wide tires, on 10.5" rims with a +15 offset. Thankfully, there's a fairly wide selection of wheels in that size, including my favorite light weight go-to, the Enkei RPF1 , Clocking at 19 lbs.

Then another update popped up. Brian Peters, a name you'll probably be hearing alot in this blog, updated his build thread with wheels that fit the maximum. 18x11 +20 wheels, paired with 3mm spacers (+17mm effective offset). Brian is also running the 285/35-18, not the 285/30-18 I plan to run.. this actually gives him less clearance on the curved upright of the front suspension.

[caption id="attachment_43" align="aligncenter" width="300"] Yup, They'll fit.[/caption]

[caption id="attachment_44" align="aligncenter" width="300"] And look good too..[/caption]

They're XXR wheels which isn't really a great brand, nor are they they the lightest (at a bathroom scale 25lbs), but they have price going for them as a set of 4 can easily be had for around $700 on ebay. That's less than half the price of the RPF1s.

After all this, I've pretty well identified exactly what sizes will fit, and have been keeping my eyes open for lightweight options that may spring up.

I've gotta give the flushtards out there a bit of a hand, as their efforts to screw up their cars have made nice wide wheels fairly more common.

 

 

Choosing The Car – Part 2

So now that I've covered the basics of the options of the 350z, I have to pick which one to buy.

The standard factor in autocross is usually grab the lightest, followed by the most powerful. Simple equation. Not so much in this case..

As I mentioned earlier, the chassis among all 3 variants is identical, so I don't need to chasing a certain year with better geometry, or a faster steering rack. The same gear box  and rear end is also used, so no better gearing ratio to be had.

On the weight factor, I couldn't find anywhere specifically that there was 151 more lbs added to the HR variant cars. No mention of more supple powered airbag seats, or a steel vs aluminum hood.. nothing nice an clear cut. so I have to assume that weight is there to stay.

So, engine then? On two factors we can easily eliminate one candidate from the running, the 06 Up-Revs. They weigh as much as the 07-08 HRs, and have less horsepower and torque. On top of that big disadvantage they supposedly have oil consumption issues, possibly a byproduct of being spun harder (7000 RPM vs 6500) with (rumored) only a mild rework of the internals. No, an 06 is definitely off the table.

Continuing on the horsepower comparison, we're down to the orignal DE engine versus the new higher strung HR engine. There's defintely a noticeable output difference between these two engines. the wiki pages put them at 287 and 306 hp, 274 and 268 lb/ft respectively. Even at 151 lbs heavier, the HR has a power/weight ratio advantage over the DE, but is down on torque. Not good. But these are factory numbers.. separated by different SAE calculations. So I went digging, and came across a most helpful forum post: Stock DE vs Revup vs HR vs VHR numbers

[caption id="attachment_19" align="aligncenter" width="300"] DE Engine Dyno
234.8 HP - 222 Lb/Ft[/caption]

[caption id="attachment_20" align="aligncenter" width="300"] HR Engine Dyno
260.9 HP - 227.1 Lb/Ft[/caption]

Well, looks like there's a bit bigger gap there than originally perceived. Take note when looking at those graphs that they are on a different RPM scale. The DE engine revs to 6500 RPM, while the HR spins all the way out to 7500.  Adjusting for this, the HR has a very similar torque curve to the DE, and has a noticeably more aggressive HP curve.

This is all base horse power though.. what about post modification? maybe that air intake just frees up a ton of horsepower on the DE and is less effective on the HR. This too has been factored into my decision. It appears one of the biggest hold backs of the DE and UpRev engines were their intake manifold, as adding a spacer to the big pancake of a plenum frees up significant horsepower... horsepower that would be completely unavailable in STU class. Intake modifications are allowed up-to but not including the throttle body. The HR engines took care of this issue. So much so, that it required a different hood to clearance the engine. The replacement manifold no longer being a single plenum, but dual independent manifolds with a throttle body for each.

[caption id="attachment_23" align="aligncenter" width="300"] Notice the large Pancake plenum feeding the single throttle body?[/caption]

[caption id="attachment_21" align="aligncenter" width="300"] Unfortunately mostly covered by plastic, there are two independent manifolds, feeding all the way up into separate ram are intakes[/caption]

But the differences don't stop at the intake. The HR engine also received redesigned high-flow heads containing both intake and exhaust variable cam timing, as well as a compression ratio raised from 10.3 to 10.6:1. All of these differences seem to me like there's a lot more room for horsepower in the legal realm.

So, now that I've gushed all over about how much better the HR engine is, you'd think by this point that's really the deciding factor. and you'd be right, but maybe not for the reasons you'd think.

The real answer is... Tires.
In STU legal trim, the maximum width tire is 285mm initial digging has shown no shortage of people putting 275mm up front and 315mm tires in the back. Squeezing a squared set of 285mm tires all the way around shouldn't be a problem, and has already been done by Brian Peters on his STR winning 350z (DE).

If the chassis is the same, how do tires come into play in this decision? Well, it's slightly less about the tires, and more about the gearing. As I mentioned before, all 350Z use the same gearbox and rear end.

Gear Ratios (that I care about)

• First: 3.794


• Second: 2.324


• Third: 1.624


• Final: 3.538

use some maths (or an internet calculator), pair this up with the stock tire size (245/45-18) on the rear end, and a stock DE will be going 64 Mph when it hits the redline in second gear. Now, our younger HR brother gets 1000 extra RPM to play with.. meaning it's second gear tops out at 72 MPH. Now 64 is a nice sweet spot for autocross speeds, and topping out would be pretty rare.. but this is on the stock tire size. The whole goal here was to shove 285s under this thing and build a rubber monster. There's only two sizes of 285 that will fit the 350z.. a 285/35-18 (Hankook RS3) or a 285/30-18 (Dunlop ZII, Bridgestone RE-11, and Yokohama AD08). On a DE car, the 35 series tire will top out at 62 MPH.. the 30 series, a paltry 59 MPH, where as the HR engine will top out at 70 and 67 respectively. 59 is pretty much unacceptable and 62 is definitely lower than I'd like on car that will have this much horsepower and grip. It is legal to bump up the rev limiter in Street Touring classes, but with the up-rev engines being so similar to the original DE, but still being reinforced to handle only 500 more RPM, I don't know how comfortable I would be doing that.. especially on something that could be over a decade old by this point.

Then we factor in the tires themselves.. the Hankooks having a history of being squishy and demanding of heat may not work well In the northern climate, where as the options from Dunlop, Bridgestone, and Yokohama are all considerably more favorable to our mixed temperatures as well as being a generation newer tire.

So, after clearly some real thought into this.. it's settled.I'm seeking a 2007-2008 Nissan 350z Enthusiast.

Choosing The Car - Part 1

This should be as simple as hitting up AutoTrader, selecting "350z" and picking the one that has the best combo of miles and price, right? Not quite.

One thing I've learned from 8 years in the Street Touring category, you've really gotta live with what you buy. There's no update/backdate allowance like the Street Prepared cars get, so you need to choose what you buy very carefully. An example of this from my WRX is that in 05 Subaru decided to swap out the slower steering rack used in the WRX, to the faster one that had previously only been used in the STI. Doesn't seem like much, but that can be a big deal when it comes to slaloming and fast transitions.

The 350z has only one branding, but more or less 3 revisions, and a handful of option packages. The chassis, suspension, differential and transmission all remained the same throughout the run, as well as most of the body. First, I'll breakdown the option packages, because they carried more or less through all the revisions.

• Base
  This is the no-nonsense package. It came with zilch.. not even cruise control. No traction control, no VLSD, no vehicle stability, manual seats, manual mirror.. everything is stripped. Easiest way to spot a base model is the steering wheel. it's the only one with no steering wheel controls at all.


• Enthusiast
  This package picks up cruise control, traction control, and a VLSD


• Performance
  This includes all previous packages and gains 18" wheels, TPMS, and VDC. Easily spotted by the VDC button regardless of wheels.


• Touring
  All Previous Packages, and adds heated leather seats and the BOSE stereo system.


• Grand Touring
  Everything the touring includes, plus Brembo brakes. Top of the line fully loaded.


• Track
  The Track package is a cross between Grand Touring and Enthusiast. You get everything in the Enthusiast package as well as VDC, 18" lightweight Ray's wheels, and Brembo brakes.

For my purposes, I'm targeting a Base or an Enthusiast model. I'm going to wind up adding an aftermarket diff in STU trim anyway, and changing the the tire stagger messes with VDC. The only reason the enthusiast is on my list is cruise control. 5+hr road trips are not uncommon for cars pulling autox duty for me, and that's a very ice thing to have. For the new Street classes, an Enthusiast model will be the best option.

Next up we have the "Revisions", all of them are based around the engine they came with. Easiest way to determine which engine the car came with is the gauge cluster. Each revision had a different redline.

• DE
  The original release of the 350z was sold from 2003-2005, and equipped with the VQ35DE engine. This put out 287hp and 274lb/ft. The redline is 6500 RPM. Base weight of these cars is 3,188 lbs


• Up-Rev or RevUp
  The second revision, sold only in 2006, but first making an appearance in the 2005 Anniversary edition. Still a VQ35DE engine, but with a 7000 RPM redline and some reinforced internals it outputs 300hp and 26o lb/ft. This car maintains the same weight as the original. There are many noted concerns with higher than average oil consumption for these engines.


• HR
  In 2007 the VQ35 got a large overhaul. now carrying the title VQ35HR, updated connecting rods, heads, exhaust manifolds, and independent intake plenums yield 306 hp and 260lb/ft and a 7500 RPM redline. All these changes did add to the car though, as the base weight is up 151 lbs to 3,339. These cars are easy to identify externally by a revised hood that is raised in the middle.

Now that I've covered the models themselves, in part 2, I'll be covering the thought process to which one I want to purchase.

And we're off and running..

An empty blog, for a build I haven't started on a car I don't yet own.

Seems kinda crazy right?

When I built my current, outgoing, autocross car the decision was simple. It was to be a daily driver year round and modified autox car, so it was pretty much narrowed down to a WRX up here in Minnesota where the snow flies 6+ months of the year. AWD was a fairly important option, and they didn't make alot of options in the WRX that mattered. At that point, all they'd changed was the front end between the 02-03 and the 04-05.. I like the 04-05 better, and what do you know, they came with a slightly better gearbox. Sold.

I've spent 8 years in my WRX. Building, adjusting, negotiating with sponsors, and of course, driving... but in that time that car has fallen out of favor with the gods of autocross. No longer is it the top dog in STX, as BMWs and RX-8s swooped in with their wider tire allowances and really got the upper hand. And to top it all off, the twins (FRS/BRZ) have also landed in STX to beat up on the BMWs and RX-8s. Once that car gets up and running, it's going to be an unstoppable little beast.

Some budget constraints, and urges to try something new after a pretty dramatic winter of change made me decide to leave the WRX in storage and spend the year co-driving. I've hopped in about a half a dozen cars over the 2013 autox season, with most of my time spent in an RTR-ES Mk2 MR2 (The Zebra).

Driving all these RWD vehicles made me realize how different the handling dynamics were to my pushy, nose heavy WRX that I'd been fighting with for all that time. It took me a long time to try and get over some really bad habits that I had learned spending so much time behind the wheel of my trusty friend. After a season of doing that, and what felt like getting faster as a driver, I decided it was time for the WRX to head on down the road, and for some new RWD vehicle to come into my life.

Of course i'd love to go cut a check for a BRZ and continue my run streak in STX.. but I can't personally justify turning a new $25k car into a track only toy.. but then like a message from on high, the SCCA fast track deliverith.
The September fast track had a rule suggestion to move the Nissan 350z to STU, from it's previous home in STR. Hmm.. a 300 horsepower rear wheel drive coupe with a limited slip and 285 tires on all four corners? Now that sounds like a hell of a fun car.

Since then, the 350z has been cleared to move to STU, so here we are.The goal of this blog is to document my thought process in choosing a car, build plans, when I actually buy one, the build, and any development along the way.