SCCA STR 370z Progress Thread.... It can be done!

[MIKE_STR]

Hello!

My name is Mike Carpenter and for the last couple months I've been building a 2009 MT 370z for competition in SCCA Solo STR Class. In this thread I'll post progress, lessons learned, and results from events I attend.

Just like any race build, things take time. From what I've seen, with the exception of Stock Class builds, there's really no data available in regards to STR or SP prep for the 370z. The goal of this thread is to fix that. Hopefully, you folks will find my posts helpful.

CURRENT SETUP

Suspension:
BC Racing ER Coilovers / Custom Valving BC NA
14k Front / 12k Rear
Whiteline Front Sway Bar Full Stiff
Whiteline Rear Sway Bar Full Soft
SPL Front Endlinks
SPC Front Camber Arms
SPC Rear Lower Camber Arms

Alignment:
-3.3 degrees front / ".25" Toe Out
-2.6 degrees rear / ".25" Toe In

Drivetrain:
Cusco RS Differential / 60% Lock
Whiteline Rear Differential Bushings
Redline MT Transmission Fluid
Royal Purple 75w140 Rear Differential Fluid

Engine:
Berk HFC Cats
3" Custom Single Exhaust (Saved 35lbs over stock exhaust)
4lb Shorai Lithium Battery

Interior:
Recaro SPG Seats
Bride FO Rails (rails are too heavy... but these are the only option with sliders that will fit me at this point... Total weight with seat is 35lbs. STR minimum is 25lbs. I could potentially save 10lbs a seat!)

Wheels:
TSW Nurburgring 18x9 +35 18.3lbs
Mustang Cobra R 18x9 +25 26lbs....

Tires:
Federal RSR?? (Probably switching to Yokohama ADO8R's for next year).

Current Curb Weight = 3134 with 1/2 tank of gas.

[MIKE_STR]

Reserved for future use

[MIKE_STR]

reserved for future use

[MIKE_STR]

Sunday October 25th , 2013 St George, UT SCCA Solo Match Tour – I ditched my warm bed for a fixed back Recaro bucket seat, grabbed a cup of coffee, and drove 4.5 hours so I could arrive at the event site by 9:30 a.m. Bottom line, I needed to get the car on the practice course ASAP.

This was my first event using my new BC Racing ER coilovers, all new spring rates, new alignment, new ride height, and a reconfigured rear differential. After a poor performance at the 2013 Solo National Championships, I decided to regroup and try and fix what went wrong. What went wrong you ask? Well, just about everything.

Let’s go back in time… My initial build used a set of well known “off the shelf” coilovers. These coilovers seemed to feel great on the asphalt surfaces we use at local events. Adjustment clicks for both rebound and compression made a notable difference and the progressive springs appeared to be doing their job. However, I had never tested the car on a “super grippy” surface. Lincoln Airfield, the site for Solo Nationals, just so happens to be a “super grippy” surface. Yup.

The car was virtually un-drivable. The rates of the progressive springs proved to be too soft. Furthermore, the body of the shock was not adjustable to allow more travel. As a result, I ended up slamming the car on the bump stops at nearly every turn. Oh, and a clutch type L.S.D. that was hell bent on locking 100% of the time doesn’t help either. Unknowingly, I had accidently concocted the perfect recipe for a 370z drift car… Back to the drawing board.

Utterly defeated, I made the long drive home through the corn fields back to Utah. I knew I needed stiffer springs. However, I also knew I would need a re-valve to support the spring rate jump I needed. I called the manufacturer of the coilovers I was running seeking a cost and time frame to re-valve my existing shocks. After skillfully navigating their automated system, I reached a Sales Rep that politely told me that his company does not re-valve the series of coilover that I had purchased. Perfect. I pulled the coilovers off the car and listed them for sale in less than 45 minutes.

My next set of coilovers needed the following features:
(1) Valved for higher spring rates (16k-18k front / 12k-16k rear).
(2) Straight rate race springs
(3) Adjustable bodies to adjust for ride height and shock travel
(4) An in-bord rear spring setup to keep the car STR legal as I’m unable to reinforce the shock tower under the STR rule set…
(5) VALUE. The best performance for the lowest cost.

Enter BC RACING. I was referred to BC Racing through a fellow road racer on the370z.com forums. As it turns out, BC Racing offers a custom valving service on all of their product line. However, the product that really stood out to me was the Flagship ER Series Coilovers. These gorgeous shocks come with the pillow ball top hats, adjustable bodies, external oil reservoirs, double adjustability, and optional swift springs! Furthermore, BC Racing had developed a custom spacer/adapter for the rear inboard springs which would allow me to run the exact same size of springs on the front and rear. Once again, they could be custom valved for whatever spring rates I wanted to run… All for less than half (in some cases a third), the price of anything even remotely comparable? SOLD!

BC Racing had my new ER Series shocks built and shipped to me in roughly two weeks. I ordered a plethora of spring rates (18k, 16k, 14k, and 12k) so that I could do some much needed testing. Meanwhile, I also had a close friend of mine help me rebuild and re-configure my differential so that it wouldn’t lock so abruptly on corner exit. A new set of coilovers, a new more aggressive alignment, and a new configuration on my differential in less than a week. Phew…. Now to the St. George Match Tour…

I arrived Friday morning at 9:30 am. Friday was scheduled as a practice / test-n-tune day. There was no doubt that with a completely new setup, I definitely needed to test the car. After throwing my race wheels and tires on the car I lined up for my practice runs. The shocks are 30 click adjustable for both rebound and compression. I started my practice session with the shocks set right in the middle setting, -15 compression and rebound, and started making changes based off the feedback I was getting from both ends of the car. After about 10 runs I felt like I had the car as dialed in as it could be. I ended up with:

-10 front rebound
-10 front compression
-5 rear rebound
-25 rear compression

Saturday October 26th, 2013 ST. George, UT SCCA Solo Match Tour

I woke up, or should I say “rose up” from my plywood topped, $40 dollar a night, hotel mattress. After grabbing a cup of coffee and an “Egg White delight” McMuffin from the McDonalds on the way to the site, I started to get excited about my competition runs.

Street Touring Roadster was arguably the toughest class at the event. There were only nine people in the class, but there were some serious names in the list. Brian Peters, Clint Child, and David Rock were in attendance… and these guys are fast. Here’s a quick run-down….

The living legend, Brian Peters, just finished smoking a class of 50 drivers in STR (including myself), at the 2013 Solo Nationals. To be honest, I’m not even sure how many National Championships Brian Peters has won… Now, I’m sure I could look it up… but as they say, “Ignorance is bliss.” David Rock was present in his MR2 Spyder. He had proven how crazy fast he and the MR2 can be taking 6th place out of 50 STR drivers this year at the National Championships. Clint Child was co-driving Brian Peters’ 350z in STR for this event. Clint is usually seen driving one of the cleanest Integra Type R’s I’ve ever laid eyes on. Clint was able to pedal his STX prepped Type R to 3rd place out of 60 drivers this year Solo National Championships. Sebastian Rios showed up in Max Hayter’s STR prepped NC Miata. Sebastian is rather new to STR. However, he took 2nd out of 43 drivers in STX Class at the 2011 National Championships… Bottom line, these are four very fast drivers.

The temperatures at the site were hovering around 60 degrees as we started our morning competition runs. Like a fool, I had neglected to bring any tire bags to hold in tire heat generated after my runs. I was on 8 month old, 150+ competition run, Hankook Ventus RS3’s. In my opinion, Hankook RS3’s are one of the best high heat tires. Unfortunately, the RS3’s are bricks in the cold. I didn’t have co-driver or tire bags so my only hope was to get enough heat in them by my fourth and final run. Brian Peters was also using Hankook RS3’s. Unlike me, Brian Peters is no fool. He’d brought Clint Child to warm his tires and was also wrapping them after every run.

My first run was respectable 59.289 considering the cold tires. The car felt foreign and didn’t feel at all like the car I had driven on the practice course the day before. I was constantly catching the car and making small adjustments to try and compensate. I attributed this erratic behavior to the cold tires and left the my suspension settings I currently had in place. Clint Childs ran a 59.5 +1 cone putting him at a 61.5 after his first run. I was sitting in 3rd place after first drivers first runs. Brian and Clint immediately wrapped the tires after Clint’s run to keep whatever heat they had in the tires. Shortly after, second driver / first runs began, and Brian Peters took his first crack at the course. He immediately put the whole class on notice running a 56.106… The rest of STR was left battling for 3rd place as Brian and Clint were the only two drivers with warm tires. Ultimately, Brian Peters found a 54.256 on his fourth run and Clint Childs found a 55.603 on his third run. Not one other driver even touched the 55 second mark. David Rock took 3rd place with a 56.137, Sebastian Rios took 4th place with a 56.518, and I was able to hold onto 5th with a best time of 56.536. As you’ll see in the video… the run was still very sloppy. I was constantly catching the car…, and it was very frustrating.
FASTEST COMPETITION RUN

In the Match Tour format, all drivers are competing for placement in the top 32 brackets A and B. The top 32 are held for brackets A and B on Sunday Morning.

Brian Peters finished in 1st place for Bracket A and 2nd place in the Top 32.
Clint Childs finished in 3rd place for Bracket A and 5th place in the Top 32.
David Rock finished in 13th place for Bracket A and 16th place in the Top 32.
Sebastian Rios Finished in 33rd place outside of the Top 32.
I, Michael Carpenter, finished 34th place and not in the Top 32.

What does finishing 34th overall mean? It means that I would not be held in the top 32 bracket and would need to run again Sunday morning in the L.C.Q. which stands for “Last Chance Qualifier.” Perfect! Assuming that I would be able to run the same times I did in competition, I should qualify no problem in the L.C.Q and would be held for Bracket C...

The afternoon consisted of non-competition fun runs driving the existing course backwards. I approached Brian Peters and asked him if he would be willing to drive my car. I knew he’d accept as I could tell he’s been curious about my car since day one.

Brian wanted me to drive the car first with him in the passenger seat. Brian is a Evolution Driving School Instructor and he’s used to giving valuable feedback to drivers of all levels. While driving the car backwards the car bogged right after a fast right hand sweeper. At first we speculated that the car shut itself down because engine temps were too cool. After all, I had a third of a tank of gas in the car. I ran a 51.2 on my first run. From the passenger seat, Brian felt that the car wasn’t putting power down as well as he would like on corner exit. He wasn’t sure at that point if it was my right foot or the differential.

It was Brian’s turn to drive. Brian started out by trying to late brake for the first right hander. Frankly, I couldn’t believe the speed he was trying to carry into that element… and I knew the car well enough that I knew we also weren’t going to stop in time. Sure enough, the ABS activated and we over shot the race line by about 10 feet. Right after the sweeper the car started cutting out again. There was no way it could be engine temps at this point. It had to be fuel starve…. I was dumbfounded. Once again, I had over a third a tank of gas in the car. Mind you, this is not a small tank. It’s a 19 gallon tank of gas…. So that means I had roughly 36lbs of gas sloshing around in there and I still was fuel starving. I apologized to Brian for my stupid car, ran down to the bottom of the hill, added 4 gallons of gas, and brought the car back for him to drive once more.

Brian now knew what the car was going to do in the braking zones. He adapted immediately to the brakes and through down an impressive 49.5 in the car. Not bad at all! This time the car didn’t fuel starve with the now half a tank, a whopping 54lbs, of gas in it. Brian was able to provided me with some much needed feedback. He said that the car felt like it was well balanced, the shocks seemed to be working great, and the spring rate felt very good. My right foot, not the differential, ended up being most of the problem with putting down the power on corner exit. However, he did recommend removing all of the bump, my remaining 5 clicks of adjustment, from the rear shocks. Furthermore, he mentioned that his 350z seems to work better without a rear sway bar and less front bar. He recommended that I try removing the rear sway at some point. Good stuff!

Sunday October 27th, 2013 ST. George, UT SCCA Solo Match Tour

Ahh… Sunday Morning. Thank you granite slab topped mattress for yet another night of tossing and turning from being extremely uncomfortable. I’m a heavy guy, and I’m not joking when I say that I was unable to even compress that mattress an inch.

Just like every Solo National event, the whole thing kicks off an hour earlier on Sunday then it did on Saturday. What does this mean for me? Yes, you got it…, even colder tires. Fortunately, I had already foreseen that problem the night before. A good friend of mine, Ralph Pensel, let me use his RV tire covers. Yes, those off-white vinyl covers that people put on their RV’s to block UV light. Would this work? Who knows… but I figured it was better than nothing at all.

I staged my car in grid, put a tire cover on the ground near each wheel, and waited for competition runs to begin. For the L.C.Q. drivers are given 2 runs. No runs from the day before count. The top 8 qualifiers from each group will move on and will comprise Bracket C. I supposed if I could match my time from the day before, a 56.536, that I would qualify in the top 8 from my group, and therefore qualify for Bracket C. Sebastian Rios in his NC STR Miata had qualified finished one spot ahead of me, in position 33, the day before. As a result Sebastian was also competing in the L.C.Q.

First Run: The car was a complete handful. Of course, I naively thought that I could go out there and be as aggressive as I had been on my 4th run the day before. I was very wrong. The car was all over the place, washing out in the corners, not steering on the first input, etc. I ended up with a big fat DNF on my first run as the car refused to turn going through the finish. I had the choice of taking out the timing clocks and about 15 finish cones or removing throttle and going in the dirt… I chose the dirt. I made it back to grid dragging my brakes the whole time to try and heat up the rotors. I parked the car and immediately trough the RV tire covers over my wheels.

FINAL Run: I pulled the RV bags off to find that the tires were actually somewhat warm… AWESOME! I pulled to the start and launched onto the course. The car felt much better. I had DNF’d my first run, so it was this run or nothing. I whipped the car through the final turn and FUEL STARVE…. The power came back right as I was crossing the finish lights. You have got to be kidding me. My fuel gauge showed more than a half a tank of gas. Fortunately, even though I had fuel starved at the very end I had actually picked up some time. I ran a 56.528 which was just a touch faster than my fastest competition run on Saturday. This proved to be enough and I qualified in 3rd place for C Bracket! Fellow STR competitor Sebastian Rios was unable to get back to his competition time on Saturday and didn’t make the cut for the C Bracket.

I ran to the bottom of the hill once again to buy more gas. I added another 4 gallons not knowing where the car was going to stop fuel starving. By my calculation I was running nearly 80lbs of gas in my car just so I wouldn’t fuel starve. This car exhibits the worst example of fuel starving I’ve ever heard of… ever. 80lbs of gas is just insane. Not only is this the heaviest car in Street Touring Roadster, but now it just got even heavier.

C Bracket 1st Round: First Round Runs I was excited for the C Bracket as I knew we’d be running in the afternoon. The afternoon meant warm temperatures and warm temperatures meant warm tires! The first round in the brackets consists of two hot lapped runs. For example, you take your first run, and then pull right back in to the start lights for your second run. I’m sure this is done so that the gents with race tires can get their tires up to operating temperature as well.

The first round of Bracket C was against Francis Miller in an ASP Evo. My first run felt great as the tires were warmer just sitting in the sun then they had ever been during competition runs. I came in with a indexed time of 46.884 which equaled a 55.8 in RAW time… a drop of over 7/10ths. Francis Miller came in with an indexed time of 48.5 which gave me a healthy 1.2 second lead for the first run. My second run felt even better. The car was far more responsive now. She was finally starting to feel a lot more like the car I’d driven on the practice course and during the fun runs. Hot lapping the tires meant that they were very warm now and times fell yet again. My second run yielded a 55.4**. Francis picked up some time as well, about 7/10ths. However, a 7/10ths pick-up didn’t end up being enough and I moved on to Round Two.

C Bracket 2nd Round: 370z STR St. George Match Tour 2nd Round Bracket C - YouTube 2nd Round – Final Round are all single run elimination. My 2nd round was against a good friend of mine, Ryan Dillan, in his beautiful SMF prepped Mazda 6. His car had taken 1st place in the competition runs at the hands of his Co-Driver Matt Linford. Ryan had not been far behind Matt’s times. Ole Ryan had just been “ridin’ dirty” with cones on all of his fast runs. Ryan left first. His car looked great through the slalom. Once again, I gave chase. I was pushing the car hard at this point. I entered the slalom late and tried to make up speed before the 1st turn around. I didn’t know it at the time, but I’d hit a cone doing it. I pushed the car hard through the final two finish sweepers and crossed the lights not knowing if I’d won or lost. As it turns out Ryan had also hit a cone and had gone a little bit slower than his competition runs. I moved on with a 55.4*** +1 (57.4).

C Bracket 3rd Round: I was relieved to hear that George Curtis, my good friend and 3rd round competition, had just knocked Bill Schenker in his CSP Miata out in his 2nd round bout! Mr. Schenker had purposely been dirty during his competition runs on Saturday so that he could run the L.C.Q. and qualify for Bracket C. Since Bracket C started, it was clear that Mr. Schenker was dumping his “sand” all over the course and was driving at a level that could potentially win the whole event. However, ole Bill got too used to hitting cones on Saturday and carried that trend over into the Bracket rounds. Bill was out and it was down to me and George. George was also running much faster than his competition runs on Saturday. However, in his round against Bill Schenker, George’s STX prepped 325is’s radiator fan malfunctioned, ate his a/c belt, and removed his power steering belt. He called a 5 minute mechanical to try and fix the problem. A couple of drivers, including myself, came over to help him try and get his power steering belt back on… Unfortunately, George couldn’t get the belt on with the tools and the time he had and I got a bye for round 3. I took my competition run anyway and dropped more time running a RAW time of 55.3**.

C Bracket FINAL Round: Final Round Run I’d made it to the Final! The final round was against Max Hayter in his beautiful blue pearl STX prepped 2013 BRZ. Max had also found a lot of time all afternoon. This was bound to be a good match. Both Max and I had hastily thrown our cars together about a week before the Match Tour and as a result were finally getting a feel for things. Max left first and I gave chase. I entered the slalom well, bumped the rev-limiter right before the first offset after the slalom (62mph), and then I over drove into the turn around and overshot the braking zone. I then tried to exit the turn around too soon and roasted the rear tires for a little bit and had to lift throttle. I drove the next right hand crossover well and was able to put down power early through the straight section. However, I ended up pushing the car too hard into the final right hand sweeper and over shot the braking zone. I slowed down for the first time and ran a 55.7**. My only chance of moving on to the final 4 was Max hitting a cone. He didn’t. Max even went faster throwing down a 55.9***. I would have needed to run a 55.0** to win. The car had the win in it… I just over drove.
Bracket C Results


Lessons Learned:
1. Don’t expect cold Hankook RS3’s to win anything
2. Bring tire bags or a co-driver…, or both.
3. My car needs ¾’s of a tank of gas or else it will fuel starve…
4. I need to run taller tires to help with gearing (currently on 255/35/18’s). I probably could have gained a couple tenths just by having taller tires at this event.
5. I need more power. Crazy, but Brian Peters said his car felt faster,…especially in the low end. My only engine modifications are a cat-back exhaust and high flow cat’s…, so there’s plenty of power on the table.
6. Next year I’ll try the car without a rear sway bar and potentially less front bar. Brian Peters is doing this… and it obviously works. I received plenty of spring options to try from BC Racing as well. This should* help the car put more power down on corner exit.




FINAL SHOCK SETTINGS

-10 front rebound
-11 front compression
-5 rear rebound
-30 rear compression

That’s all for now! Special thanks again to BC Racing and Rusty Horlacher with Lateral G Performance for a great finish to this season.

St. George Match Tour Results
Bracket C Results

[Rusty]

This is going to be fun reading.

[mdxj]

What diff did you have?

[Apollo8642]

Nice thread, lots of detail. Are you video recording any of these run?

[MIKE_STR]

Originally Posted by mdxj

What diff did you have?

Cusco RS. I'll post more info and pics later.

Originally Posted by Apollo8642

Nice thread, lots of detail. Are you video recording any of these run?

Yes, there are videos all throughout the St. George Match Tour Summary!

[takjak2]

Full tank or fuel starve. 3/4 won't be enough. You know the nice thing about Phunk's setup? No one has to know.

I don't know exactly how to read into the SEB response to our most recent round of STU but I won't be surprised when there's no change.

[MIKE_STR]

Originally Posted by takjak2

Full tank or fuel starve. 3/4 won't be enough. You know the nice thing about Phunk's setup? No one has to know.

I don't know exactly how to read into the SEB response to our most recent round of STU but I won't be surprised when there's no change.

Full tank? You have to be kidding. Saddle tank or not... that's insane.

My understanding is the SEB wants to increase attendance in STU by making the class cheaper. Or, I should say, introduce cars that are cheaper to build than the boost buggies. Theyr'e concerned that the 370z will bury the 350z if they were to move it and therefore... not make anything cheaper.

[mdxj]

I was thinking of going with cusco for mine since I am open right now.

[MIKE_STR]

Originally Posted by mdxj

I was thinking of going with cusco for mine since I am open right now.

It's a quality product. Don't set it any higher than 60% and don't use anything but Royal Purple or Motorcraft with enough friction modifier in it. I used redline 75w90 and 75w140 for awhile... The built in friction modifier was not nearly enough and I blame the redline fluid for most of my diff woes...

[mdxj]

Good to know. I have been researching settings for it. I am in ASP right now.

[03threefiftyz]

I use a Cusco in my BSP car as well. I use Motul fluid and 80% lock. Seems to work well for me...

[Apollo8642]

Originally Posted by MIKE_STR

Cusco RS. I'll post more info and pics later.



Yes, there are videos all throughout the St. George Match Tour Summary!

AH HA I see them now that's cool thanks!