BriK

iTrader: (11)

Parts sourced for my aluminum catback:

What I got:
- Four feet of 3" OD, 16-gauge aluminum pipe (weighs 0.7 pounds per foot-- 4' is a total excess of length, but it's cheap and I had plenty of extra just in case)
- Two mandrel bent 45-degree angles in 3" OD 16-gauge aluminum pipe
- One aluminum O2 bung. This and the aluminum pipe were all from RacePartSolutions
- Two Vibrant Aluminum Race Mufflers (weigh 1.7 pounds each)
- One Vibrant Streetpower Flat Black stainless steel muffler
- Two 3" aluminum v-bands by OBX from eBay
- One 3" stainless steel v-band flange by OBX from eBay (to be welded to the stainless steel muffler)
- One STM 3" aluminum exhaust flange (to connect the midpipe to cat)

I didn't source anything to make hangers but that was supplied by the fabricator.

Everything is mandrel bent and all the mufflers are straight through with perforated cores, so the system flows very well.

I've been meaning to get a turndown but I've not broken the sound barrier so my motivation isn't huge. Maybe something I'll add this season.

Pics are below. You'll see the midpipe has a slight angle in it which was necessary to clear the driveshaft, but it's not any lower than the side skirts so it doesn't present issues.

Butt Dyno

iTrader: (10)

How much did all that run (if you don't mind me asking)? Have you ever been to an event where they've been doing sound readings?

BriK

iTrader: (11)

Parts were $400-$450, driven mostly by the mufflers at ~$100 each. Fabrication + finishing parts was $370. I got 3 estimates and two shops quoted me 6 hours at $100+/ hour; the shop I went with charged $85/ hour and finished in 3.5 hours.

So, all told, this ran around $800 which is a little lower than the price of a used titanium catback. That said, ti catbacks tend to be loud and the impetus for this project was actually to get a quieter exhaust (hence the 3 mufflers for DD) due to a newborn daughter (she's 9 months old now); while I was at it, I thought I'd get another benefit by dropping some weight.

All the events I've run do sound metering and enforce a 100dB limit. I haven't heard where I've come in, but I've not had a problem, even with a test pipe (part of what vaulted me into ASP) and just the two race mufflers-- a high flow cat and a turndown would obviously make it even quieter.

psushoe

iTrader: (8)

John, the exhaust on my car is aluminum. I have a stainless downpipe that transitions to an aluminum "cat" back (no cat). It only has a single resonator, and I have not had any sound violations. I've been warned at one event, which was at the Deven's tour this past year. I believe the unit is an old Tab-Fab one. It was on Mike's BSP car before we put it on mine. It's been around the block a few times and is holding up well.

Butt Dyno

iTrader: (10)

Cool. I may need to get the fabrication wizards at CBRD on this Probably not a 2013 thing though.

For anyone wondering, the rear Hotchkis bar weighs 6.7 lbs
For comparison, some other useful weights
http://highboostforum.com/forum/show...n-thread/page4
So Tanabe saves ~3 lbs from stock, and the Hotchkis bar would save probably about 5 (since that weight includes brackets). That's not bad.

That's a pretty good weight list. Down-sizing the front strut bar is another decent way to save poundage it appears.

My 245-40-17 ZIIs arrived today. Going to get them mounted once the snow passes through and get them scrubbed in at the next AI event. Psyched! From early returns, it appears that like the Z1s, they'll be a little bit off for their first event or two before they really come in. I'm going to get as many fun runs as possible on Sunday to accelerate that process

Butt Dyno

iTrader: (10)

Event #1: Autocrossers Inc @ Waldorf, 3-10-2013

Finally, the first event of the year! Christmas in March. 03fiftyzee (Mike) was codriving since he was too lazy to drag his BSP car down the Beltway for two days in a row The event unfortunately overlapped with Daylight Savings Time, so as I was looking at the car on Saturday night and realizing that the SSRs+shaved Z1s were still on there, I figured it would make sense to just run competition runs on the Z1s, and switch to the Z2’s for fun runs. The conventional wisdom on the ZIIs (if such a thing is possible with such limited data) seems to be that they are like the Z1s and don’t really come in at their first event or maybe two events - they need some runs on them before they’re fast.

Results aren’t up yet, so I’m doing this from memory. No video/data but I should have that for event #2.

I was in a bit of a daze for morning runs, having not gotten anywhere near the amount of sleep necessary to be a functional human being. I hit 4 cones on my first run, all with the front of the car, all pretty much during turn-in. So either the car turns in a bunch better or I am anticipating just a bit too much 44.7, +4. Mike went out and ran a faster time, but with two cones - 44.1+2 (I think). Both our 2nd runs were dirty also. We then realized that the tires had crept from 38 all the way up to 43 and took them down. I hadn’t brought a sprayer either (again, a bit out of it... and I hadn’t anticipated needing one) so we were hoping the tires wouldn’t get greasy. They stayed okay though. Anyway, on our last two runs, I managed to get a 43.7 (or was it 43.4?) and Mike dropped all the way to a 43.1 to take the lead in PAX and Pro.

At this point I bolted the Z2’s up. They are on my 17x9.5 and very-orange RPF1s, so it’s not a 100% fair comparison (wider wheels). They had zero street miles coming in.

In 2nd heat, Sam Strano took the Pro/PAX lead with a 41.1 in a Super Stock C6 Grand Sport. 41.1 on the SS PAX is 35.3049. To tie that with a PAX of .846 would require a 41.73.

Sooo... on to fun runs.

I went out on the ZIIs first time and just overdrove stupidly - intentionally. I wanted to get some heat in them and start the break in process right I think I ran a 55.x, with a spin in there somewhere. But on my 2nd run - 43.4, with one really ugly mistake in the middle of the course. 3rd run - 43.1, with a braking mistake into the turnaround. 4th run - 42.7! Holy crap. If the ZIIs are really “slow” their first day I can’t wait for day 2. On my 5th run though, the tires were overheated and I went back down to a 43.4. There was some overdriving there for sure but those tires were mad at me by the time the run was over Keep in mind these are 5 runs pretty back-to-backish. I stopped to bleed pressures but there was not 5 minutes between any of those runs, probably a lot less for the first three runs.

Then, bonus! Sam was able to take the car out at the end of fun runs to get an impression. On his first run, the timing equipment didn’t work.. doh! On his second run... 42.2! Criminy. He went out for a 3rd run, pretty sure he could get a 41.x out of it, but the tires quit on him pretty quickly - 42.6 with lots of understeer and squealing. I really wish I had brought that sprayer... I think another run with proper pressures and not violently hot tires and he would have gotten there.

Later he said, “What are the spring rates on this car? This is the best one of these I’ve ever driven.” He said the car felt much better than it had looked previously.
Me: Can I infer from that feedback that I should leave the car the f* alone?
Sam: Yeah
Me:

One other thing about our fun run times - for the competition runs, we were launching enough not to bog, maybe a little more. We got a little bit of clutch smell, so for fun runs, I was putting it in 1st, letting the clutch fully engage, and then hammering the gas, in order to make sure I wasn’t slipping it at all. So there was at least a couple tenths of slow in the fun runs, because the start line was pretty close to the start timing lights.

So, reasons why the test wasn’t scientific:
-fun runs were later in the day when the course was more rubbered in. (would skew to Z2)
-I was driving better in the afternoon (would skew to Z2)
-Less launching in fun runs (would skew *away* from Z2)
-Z2's were brand new (would skew *away* from Z2)

Reasons why it was vaguely scientific
-In both cases I had someone faster than me driving as a sort of “control”

I’ll update this post with real numbers when the results are up, but that’s the jist of it.

So, Z1 vs ZII cliff notes:
* Fastest me time: Z1 43.7, Z2 42.7
* Fastest not-me time: Z1 43.1, Z2 42.2
* Z2s pretty damned fast their first day
* Seem to require about the same pressure as the Z1, maybe a little less

Since the BFG’s are not out in our size until May, I am going to just run the Z2s all year and wait for things to settle down. So far I think this is going to work out okay.

03threefiftyz

STU is .846 not .827. The evo is fun.

Butt Dyno

iTrader: (10)

Ahhh I was looking at STX. I'll fix it.

03threefiftyz

What size wheels were the Z1's on? I think a 41.8 was doable on the Z2's. It didn't feel like there was much left out there on the Z1's...although it was the morning, etc.

Butt Dyno

iTrader: (10)

17x9s. I don't know how much the extra .5" really matters on stiff tires like that, but I'm sure it doesn't hurt.

piknockout

I'm betting that had you done Z1 fun runs in the afternoon that you would have been within a few tenths of your ZII runs. With a warmer, rubbered in course after knocking out 4 months of rust, I can imagine that you could knock out 0.6-0.8s pretty easily. Then again, ZII's with no break in, overheated, etc.

Then again, this "test" was not scientific in the least, and even if it was then you just provided information that everyone pretty much already knows: ZII's are better than Z1's. Thanks for nothing.

03threefiftyz

I don't disagree. We were one of the first cars off on the day (probably temps in the 40's?) and the fun runs were with temps in the mid 60's. The course/familiarity was probably good for .5-.6 or so...

Hopefully I can take a stab at the Z2's some time this season.

Butt Dyno

iTrader: (10)

I need a DeLorean and some plutonium so I can do same day same surface testing of Z2's when they are brand new vs broken in.

qucifer

I may be at the NNJR event on 3/30 and my ZIIs may be brandy new for that event. If you're there too I'm sure we can work something out.

Currently mounted on 17x9 FN01R-Cs.

-Bryan

Butt Dyno

iTrader: (10)

Thanks for the offer - I don't think I can go anywhere Easter weekend though. In fact I withdrew from the NJ Pro this week. April just sucks this year and removing clutch-splosion from the list of variables was worth it for me. It sucks though as it looks like it's going to be a good field.

Event #2: WDCR/SCCA @ Fedex, 3-17-2013

This would be the first test against Josh and Shane in 2013.

It was a great course... designed by an 11 year old Julian G (FJA/FJB national champ a bunch of times) designed it when he was in FJB but never got to use it until now. He is almost 16 and soon will be terrorizing some non-FJ class near you (he’s already running showroom Spec Miata IIRC). Good mix of fun and tricky.

Since there was lower enrollment for this one, WDCR let you sign up for both morning and afternoon. Early in the season, still figuring stuff out, definitely a good thing. It was mid 40’s and very windy so there was almost no heat in the tires, even after 4 runs.

Run 1, official get off the rust at Fedex run. After almost spinning in the first corner, I got it together and ran a 64.2... +4. One of the fastest times, at the time.. until Shane came across with a 59.4. Crap Due to the low grip, I backed off the rear rebound. It did seem to help.

Run 2. This run started out pretty well, got through the first batch of tough sweepers under control, and was 80% through (and clean) when... I caught up to the Mustang in front of me. Didn’t get flagged, so it’s good that the Mustang was a nice bright orange. Got a re-run, which I hoped would work out okay since the tires might have some heat in them.

Run 2a. 60.0, +1. Not sure what I hit, but I’m guessing it was the quasi-Jones cone in the last box (1:06 mark). I was a bit behind in two of the braking zones (:46 and :56). My looking ahead doesn’t look as bad as I thought it was... but I definitely don’t feel like I was *thinking* ahead.

Meanwhile, Josh and Shane both ran dirty 58’s... I did not know this at the time thankfully

Run 3. Serious kerfluffle at the :20 mark, not getting the car entered into the braking chute right. Hit another one somewhere (I think in the slalom at the end). 60.6...+1. Josh gets a 59.0, Shane runs a 59.2+5.

Run 4. The same mistake I made on run 3 at the :20 mark, I made much worse, taking out 3 cones. The rest of the run was really, really good though. On the uphill section (:41 second mark in the run 3 video) instead of hitting the rev limiter just a couple of times, I hit it for like a second and a half. I knew that meant I had done something right. I ended up with a 59.7+3. Given how bad a slide into the wall I had made, I felt really good about this run overall - minus that mistake it would have been a low 59 for sure, maybe better. My GoPro had fallen off the car before this run (in grid thankfully) so no video.

At the time, I thought my 60.6 was clean. Doh.

Afternoon runs came, with the rest of the normal DC STU competitors. Same temperature, maybe a little windier. Generally pretty miserable.



Run 1 - same as run 1 before - cold tires, little grip. 61.2, but DNF because I understeered through a wall

Run 2 - pretty decent. Another 59.7 but only +1 this time. I think Shane rode along for this one, and told me I was braking too much on the first half of the course, both braking where braking wasn’t necessary, and overslowing when braking was necessary.

Run 3 - spun in the chute. Intentionally over-drove the rest of the run to try to get heat in the tires. 72 something.

Run 4 - final run and... hit a cone in the first 5 seconds in the slalom. F*. 60.2+2.

Zero clean runs. 16+ cones over 8 runs. An inauspicious beginning to my season at Fedex for sure.

No video... have some data, but it’s early so I haven’t bothered processing it.

Even ignoring the cones, Josh+Shane murdered me a little, first time out on Z2s. My best raw was 59.7 and they both had dirty low 58’s. They had a little bit of tire heat advantage (I didn’t have a codriver) but I don’t think they had 1.5 seconds worth. I know I had 80% of a really good run but never came close to getting it together on one run.

The car felt great, considering the conditions. I really have no complaints there.

Seeing as my schedule is about to shrink a little, I need to make every event count more. So I’m going to make mini resolutions for the next event that I can skim easily. For 3-24, notes to self:

* Turn off the GoPro when you’re done running so you can actually diagnose your driving later
* Do 3 course walks per session, even when it’s freezing (actually, especially when it’s freezing). I only did one each, thinking it was a test and tune and who cares... but that’s a terrible habit.
* Try the blue tape on the windshield trick to force yourself to look ahead.