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dgross7's STF build thread

47K views 244 replies 24 participants last post by  dgross7 
#1 · (Edited)






Using this thread to document/share my progress both as a driver and of my car.

Improvements to date:

Chassis
Koni 8611-1256 race inserts
Corksport plates
Hypercoil 400f/650r
Goodridge ss lines
SPC rear arms
EBC yellowstuff
Tripoint RSB
AWR endlinks

Engine
Mazdaspeed CAI
Vibrant Headers/HFC
Racing Beat exhaust
SU trans mount
cp-e passenger motor mount 60 duro
cp-e rear motor mount 65 duro

Wheel & Tire
Rota Slipstream 15x7.5
205/50/15 RE-71r

O.Z. Alleggerita 17x7.5
225/45/17 Michelin PSS (travel tires)
 
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#2 ·
Just last week I purchased the speed3 brakes from a fellow member.

Weird thing I realized and I want to say I remember reading it somewhere but haven't been able to find it. Notice the dust covers sitting on the ground next to the car. They did not fit with the larger rotors so rather than try and bend them out of the way and risk the cover contacting the rotor, I just removed them. Maybe I'll purchase the ms3 dust covers one day, or I'll just cut back the stock ones I have, not worried about it too much right now.
 
#3 · (Edited)
Just FYI VTCS flap removal bumps you to street modified at least.


Otherwise looks good. Will be watching. I'm casually running stf because I want to fix the "Mazda problems" it came with... motor mounts and wheel width in particular.


Edit: do you have your old 3S caliper brackets? I have an I model and want to run the S brakes myself. I think the speed 3 brakes are heavy and over kill for autox... if you plan on track driving they're a great choice then though.
 
#4 ·
Right now I am torn on the brakes. While they are a definite improvement, I wonder whether the change to hawk HPS pads or the speed 3 calipers made the largest improvement. I only had stock pads on before.

And thanks for bringing the flaps to my attention, after reading more carefully I see I am not allowed to modify them.
 
#7 ·
I'll say I'm unimpressed with HPS pads vs stock pads. I found no more overall stopping power, but they are easier to modulate and not so grabby. They're not bad or anything, just pointing out that most of your improvement is likely from the calipers and larger rotors.

I will go for EBC yellow pads next, others here have reported they are way better than HPS for autocross. I'll do those and 3S upgrade at the same time likely.
 
#5 ·
From my experience AutoXing, I'll give you two options.

1. You're a dedicated, serious Autocrosser for life. Read the rule book like it's your bible, be prepared to make substantial changes to your car to stay competitive/within the rules year by year when they change.

2. This is the gateway drug that leads to track days. When you get tired of autocross, and want another challenge, you'll naturally make that progression. If that's the aim, then mod whatever you please, don't worry about what class you're in, and just concentrate on learning car control before you move into higher speeds/track days.

I chose option 2. in my Miata, and loved every second of it. By the time I quit autocrossing, I was in SM2 in a naturally aspirated Miata getting murdered, but didn't care. I was just on my way to track days, and as long as I got faster than last month I didn't care how far down in the class I was.
 
#8 ·
C&D did a good comparison of a selection of brakes. I came across it when GrifN was trying to figure out what to get (wanted stock but enough convincing from all sides was that was a bad idea).

But yeah, pretty good short read. HPS are good when cold, but AWFUL for trackdays, surely fine for AutoX, but once warmed up they begin to fail very fast; friend in a speed miata learned that the unfortunate way at the last track day. My new brakes have HPS pads and I will absolutely be swapping the fronts at least for something with more bite.
Otherwise, I've been very happy with my EBC Yellows. Plenty of dust compared to stock but that's to be expected, braking is excellent, and when up to temperature also great. I only had an issue with mine once at that trackday, pushed to hard, had a bit more fade than I wanted, but oddly that only occurred once.

http://blog.caranddriver.com/performance-brake-pads-compared-hawk-hps-hawk-hp-plus-ebc-yellowstuff/

 
#10 ·
I had the HPS pads before I switched to the EBC yellows (still have the HPS on the rear actually with Yellows up front). As Tony said up above the HPS is pretty much a regular pad marketed by Hawk as a "performance pad." It wears like a regular pad, it dusts like a regular pad, it stops like a regular pad. There is really nothing high performance about them and they are not better than the oem pads...maybe even worse (ie less bite). HPS to Yellow is a night and day difference. Waaaay more initial bite and ultimate stopping power than HPS hot or cold. It will take awhile to readjust your brain and muscle memory because they quite literally need half the pedal pressure as the HPS to brake the same distance.
 
#11 · (Edited)
First scca event was a success! I really enjoyed it, definitely a lot more fun with the longer and faster courses than what I've been used to. I finished 4/4 (as expected) in FSP @ 58.993 personal best, I was 2.192 seconds behind 3rd. Videos soon to follow.

Run 1 @ 60.443


Run 2 @ 59.295


Run 3 @ 59.656


Run 4 @ 58.993
 
#12 ·
Looked good! Made some good improvements in cutting closer to cones in your last 2 runs. Were all the runs clean?


Few things I noticed: You're milking your clutch off the line... try launching it and you'll cut at least 0.3-0.4 off your times I'd estimate. I normally launch between 2500 and 3000 rpms. You don't just dump the clutch completely(though that does work), you slip it enough to hear some tire squeal until it's all the way out. Hard to explain, but dump it too fast, you'll likely get some wheel hop. Dump it too slowly and you hear "whiirrrrrr" much like in your videos. I probably let my clutch out over the course of about 0.5 seconds.

Also maybe it's just the angle, but pull your steering wheel closer to you and/or move the seat as close to the wheel as possible. You'd be surprised at how much of a difference this makes... you feel more "connected" to the car. It's much in the same as when you're playing a racing game 15ft from the TV vs sitting 5ft from it.

I have the steering column adjusted as close to me as possible(I'd pull it even further toward me if it were possible), and move my seat about 2-3 notches further forward than normal driving. My limiting thing is my legs, I can't go further forward and be comfortable hitting the clutch. If I were road racing I'd probably only be 1-2 notches forward for more long term comfort.
 
#13 ·
Yes, all runs were clean. I launch soft because the start gate isn't right away. I never get the launch right at autox. I'll practice at a red light and just launch as quick as possible without tire slip but I struggle to replicate it at these events.

Thanks for the tips on steering wheel position. I'll try pulling it forward since I can't get any closer for the same reason as you.
 
#14 · (Edited)
One thing that just crossed my mind, in the 4th run you'll notice I missed 2nd. This happens every now and then when I try to shift too fast. While it's mostly driver error, anyone have any suggestions to lower the likelihood of error? I was thinking solid shift bushings, or something to tighten things up. But I keep thinking that it grinds because it is just being shifted too fast, rather than myself messing up the shift? If this is the case then installing a short throw shifter could possibly make it worse because I could potentially shift even faster than the transmission already doesn't like?

Just putting my thoughts to words.
 
#16 ·
Change your trans fluid right meow!

I had the same exact problem grinding into second. Changed to Redline MT90 and gave it about 1000 miles to "shear" and its a night and day difference. I have not had a problem since. You still cannot shift stupid fast, but it won't grind shifting quickly.
 
#15 · (Edited)
I've experimented with launching techniques at the Pro-Solo's and noticed the best 60' times are achieved for me when I bring up the rev's to around 4,000-4,500 rpm, dump the clutch, and get a healthy amount of wheel spin. The clock says using fewer revs with little to no wheel spin = around .2 sec slower. This is on high grip concrete (Lincoln, Blytheville, Toledo). On asphalt slightly less revs may be ideal since there would be less grip more than likely. Also tires make a difference. I'm on very sticky street tires so all seasons would require a less aggressive launch for example. Basically, what I've found is the ideal amount of revs is whatever you need to spin about 1/3rd to 1/2 way through 1st gear then have it hook up completely. This keeps the revs up in the middle to upper portion of the tach and prevents bogging once the tires get fully hooked up. If you've ever seen a S2000 do a proper launch, it's sort of like that. I don't have any wheel hop issues at all in a straight line launch on good street tires (I have stock mounts too that have tons of miles on them). Only time there is a wheel hop issue is when trying to turn and accelerate too aggressively at the same time from a dead stop (Bad idea).
 
#19 ·
One more quick tip. You will be much more consistent, and most likely faster, if you keep your hands glued to 3 and 9. There is very rarely any need to shuffle steer on an autocross course. If you watch your videos you will notice the wheel never gets spun past 180 degs. Happy soloing!
 
#28 ·
Since this is an STF build thread, please allow me to ask a related exhaust question. Didn't see anything on exhaust here yet.

I know that STF is allowed headers and such, but for those of us starting out "light", and perhaps doing just a muffler or cat-back, I've been told that the stock 2.0 engine exhaust pipe is 2.00" OD after the cat. True or false? Is the 2.3 engine after the last cat also this same size, or larger? Anyone know for sure?

If true, what good would a 2.25" cat-back system do? And therefore the 2.5" systems (different makers have different sizes). would be even less useful, right?

What I'm thinking .....is that to start out inserting a Magnaflow 2" muffler might be "good enough" initially for a "start-up" effort , until headers become part of my STF budget. Perhaps as good/functional as a $600 cat-back system.

Opinions?
 
#29 ·
Not sure if things changed between generations but the 2.0L should get a 2.0" exhaust, yes. Upsizing post-cat to 2.25" does reduce the "pipe friction" for the exhaust gas so no matter what, flow is improved.

I don't think it's worth trying to upsize on a stock-block/head MZR 2.0. Keep in mind the MZR engines only go to ~7k RPM so we're not even in the regime yet where the built K20A boys start to complain about needing 2.25" or 2.5" piping to avoid choking the engine. 10k RPM's + aggressive cams + ITB's is a much higher flowing setup than ours, so if the biggest built K20's are using 2.5" I doubt that you can make use of it here, yet.
 
#31 ·
You're making several generalizations that are just plain misinformed. TYPICALLY, increasing pipe diameter will decrease flow restriction and CAN potentially increase power so long as exhaust velocity is maintained to induce a strong scavenging effect.

Its just a more complicated set of variables than you're making it out to be.


Sent from my iPhone with Tapatalk.
 
#30 ·
Just curious, why would manufacturers such as Borla, who's been around for ages and who knows what they're doing, use a 2.5 inch pipe for our cars? And same for Corksport, who specializes in Mazdas and who uses a 2.4 inch pipe for our cards? All marketing hype? I mean honestly, I feel a real appreciable difference with my Borla. Ofc, that's running it with an SRI and VTCS delete.

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#33 ·
Exhausts requiring backpressure is a myth as old as cars, and it's been disproven.


Sent from my iPhone with Tapatalk.
 
#35 ·
It's not really a straight forward answer. The way I see it though, an exhaust is what 600 bucks to gain less than 10 hp? Not worth it to me, I'd rather invest that money in headers (which are also slightly cheaper, what like 450 to 500?) where I'm likely to see larger gains.
 
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