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Jeff Goji's 2004 Mazdaspeed Miata BSP Build Thread - Kiryu
The goal of this thread is to keep track of all the modifications and various testing and tuning I'll be doing
As I very gradually turn my 2004 Mazdaspeed Miata into a BSP race car.... As cheaply as possible. ;D
Basically, I want to keep the stock turbo (at least for a little while longer), the stock 6-speed MSM transmission, and the stock 4.1 diff.
All modifications will be simple bolt-on parts that are fairly easy to attain, with special care and attention being put into the suspension and wheel and tire selection.
The car also has to be driven to the event on the tires it will be racing on, so street tires are a must for the present time.

So let's start with the basics on where the car is now and I'll update the thread as I continue to update and improve the car.

BEGI ECU re-flash
Cost: $895 dollars.
If you want to make the Mazdaspeed Miata even semi-enjoyable in autocross, you NEED to get rid of that retarded 6700 RPM rev limiter.
The serious autocross competitor who wants the most performance imaginable and is willing to spend every moment of his life fine-tuning and adjusting things and swapping the ECU back out for the OEM unit for the street will go with a stand-alone unit like Hydra.

My goals are not so lofty, and I hate swapping ECUs, so the BEGi chip and flash was the only viable option in my case.
I keep OBD2 compliance, and the rev limiter is at 7200 RPM like any other Miata. It also drives better and has more consistent power delivery across the entire rev range. It also gets rid of a stupid computer conflict that causes the infamous MSM "bog" problem.

AEM Intake
Cost: $165 dollars - I got this for a steal from a friend. Wink
The turbo spools up alightly quicker than the OEM intake, and makes more noise on the whole.
The only plus side is that the turbo now more easily over-powers the pitiful OEM electronic boost controller allowing you to often hit 9 and 10 PSI of boost in ambient temperatures below 90 degrees, which makes more power and makes you go faster.

Corksport 3.1" catback exhaust
Cost: $450 dollars.
This actually makes more power and allows the turbo to spool-up faster than the intake by itself.
You mostly notice this lag-free response in the on-throttle off-throttle conditions of autocross or aggressive driving.
The only downside, is the noise factor... Neighbors will hate you when you take that 2:00 AM drive to the "house of pies" and fire the car up in the garage. But oh it sounds sooooooooo good.

Larger front mounted Intercooler
Cost: $500 dollars.
This upgrade is an absolute MUST on ANY Mazdaspeed.
You end up with a more consistent power delivery pull after pull, especially with the AC on or when autocrossing in temperatures above 70 degrees.
Gas Head Motorworks installed a larger intercooler that they keep stocked from a local supplier for $500 dollars, which included installation and parts. They also relocated the second IAT sensor to the post intercooler pipe to help keep it from heat-soaking in traffic conditions.
Combined with the ECU re-flash, you simply can’t get more consistent or reliable performance out of this car.

Wheels and Tires:
Cost: $1064 dollars.
If you want to have a quick MSM, you need to run a 15X9 wheel at the very minimum.
15X8s won’t properly square up a 225/45/15 street tire or r-compound tire, and a 205/50/15 tire is just plain suicide on the super-heavy Mazdaspeed.
The only thing better than a 15X9, is a 15X10 wrapped in a HUGE 275/35/15 Hoosier A6 R-comp.
But, you need to cut the fenders and add fender-flares to make those tires work, and hacking up a street-driven MSM isn’t an option for me, plus the whole process to fit 15X10s with R-comps and fender flares is cost prohibitive for this build.

For the 15X9s, I wanted cheap and good looking and preferably light.
Well, that last one didn’t happen, but I did find a cheap and good looking wheel in the TR Motorsports TR3 15X9 wheels, and in my case, I went with black.
To finish them off, I wrapped them in the 225/45/15 Hankook RS3, which is an amazing maximum performance street tire that is very long-lived in its competition use and street driving.
The only issue I’ve seen form these tires is that they do need a good deal of heat to start gripping properly.
So you can expect to set your fastest runs (all things being equal) the hotter the tire gets and on your last 2 runs.
If you happen to have a co-driver, you’re in good shape. If not, plan on over-driving the car hard on those first 2 runs.

Here is my favorite subject of all time in the Miata world and a subject that is very dear to me.

I originally wanted to run a 600/400 spring setup for dual purpose system, but after Shaikh and I got to talking we decided on an 800/500 spring setup.
This setup can get a little busy on the street, but for a super heavy 2500 lb autocross car on sticky street tires, it is damn near perfect without any penalty in traction in the rain (in fact the car grips better than the stock MSM setup in the rain).
With an 800 lb/in front spring and 500 lb/in rear we are looking at bounce frequencies of 2.38 Hz front, and 2.22 Hz rear.
Right in the realm of race-car bounce frequencies... But it rides so nicely!

The FRC would be 64% with my Racing Beat 1.125” front swaybar and no rear bar. So I should have a fairly neutral handling car right off the bat, and I can always add the OEM rear sway-bar if I need more over-steer, or I could fine tune with bumpstop-packers.

For ride heights, I settled on 4.55" and 4.66" pinch weld to ground heights with the original bumpstop setup, which works out to roughly 12" front and 12.5" rear measuring from the center of the wheels to the fenders.
This would change with further collaboration with FCM and the hard knocks of autocross life.

Racing Beat 1.125” (99-00) front swaybar.
Cost: $160 dollars.
A bigger front bar is an absolute MUST on any Mazdaspeed Miata that spends time on the autocross course.
I had mine set to full stiff when I was on the stock suspension in an attempt to better keep the inside rear tire planted under Autocross cornering conditions on sticky tires.
When I upgraded to my coil-overs and could now adjust the ride height and had the car’s basic balance tuned properly with spring rates and correct damping ratios, I set the bar to full soft and dropped the rear bar off of the car.

Super Miata Endlinks
Cost: $69.95 for a pair, $139.95 for all four.
Simply the best endlinks on the market. Period.

Fat Cat Motorsport 3040 “Elite” coil-over system.
Cost: $1684 dollars (at the time of purchase, plan on a $1864 dollar price tag presently.)
I went with the Fat Cat Motorsports 3040 non-adjustable “elite” coil-over system.
The best part about this suspension setup is the custom damping ratio that is setup with your goals for the car and its intended use in mind.
You also get MCU bumpstops that are trimmed with your ride heights, spring rate and lengths, and damping ratios in mind.
You also get MCU top-hat bushings instead of the OEM style rubber bushings, which decreases NVH.

I could go through all the various little tweaks and changes I made (many, for better or worse), but that would most likely bore the majority of people who will read this, so instead I'll sum it all up to what we have now.
I ordered a set of FCM 56mm Red bumpstops and trimmed them to 24mms front and rear and used a 3mm spacer on all four shocks.
The car was lowered to 4.25mm front and 4.35mm rear pinch weld heights which equals around 11.8" front and 12" rear fender heights.
Here is the photographic data on the travel I gained from that modification:
[Image: Front90213.jpg]
[Image: Rear90213.jpg]

And here is the current alignment:


Toe: 0 mms
Camber: -3.0 degrees
Caster: 4.1 degrees


Toe: 1.0 mms In.
Camber: -2.7 degrees.

And here we are in action!
[Image: BSP01.jpg]

The car did amazingly well at 30.5 PSI (hot pressures) all around, very well balanced letting you aim the nose with the wheel and adjusting your line as needed with the throttle. And most importantly, the rear hunkered down properly on the gas in the tighter bends and the car deployed it's power almost as efficiently as it did with the stock power.

The Hankook RS3s are definitely my kind of tire. For some reason the car just rotates better on them and is more controllable than it was with the BFG Rivals.
You can still slide the tail around a bit, but recovery is easier and the tires don't overheat during a run on our car like the Rivals did. In fact, it is very much the opposite, the RS3s love to be over driven to get the most heat in them and usually deliver their best around your 3rd or 4th run, and deliver even more if you have a co-driver.

On a similar note, BSP Pax SUCKS for a Mazdaspeed on street tires!
So, I've decided to switch over to "Street Tire Other" or "STO" class to continue to run street tires and have the opportunity to race in the same class as my friends.
Jeff, thanks for jumping in with all these notes on your build. I have to read through it in detail. I just put a set of BFG Rivals on Christina (our E46 Project Car). It's cooling off here so a warm weather test hasn't happened yet. So far they feel comparable to the Dunlop Direzza Z1s they replaced in cooler temps. I also really loved RS3s on the various cars I got to drive (but haven't yet owned). I'm wondering if in raw grip the Rival is faster in a narrow temperature narrow while the RS3 loves the heat. In which case I can't see the Rival being faster than a Toyo R1R in cooler temps.

Actually, Brian C. (STR NC Miata in Pacific NW) trophied at Nats after switching to the R1R from the Rival they'd previously used.... hmm... several data points in action here!

I want to stay on topic for your overall build but your tire comments got me thinking.
Time for a quick update.

We decided to abandon the BSP route on account of severe frustration with the 2nd gear top-speed limitations of the Mazdaspeed's 6-speed transmission (54 MPH Mazda? Really? How stupid.)
I also am not ready to hack up the fenders and run 275/35/15 R-comps on 15X10s just to compete locally.

Instead I have decided to go play in a local street tire class (STO) which is a bit of a catch-all class for those of us with modified cars who want to run on street tires.
The competition in the class is VERY fierce, and I'm allowed to upgrade to a 5-speed transmission which should put us at 62 MPH at the top of second gear as the car SHOULD have been set from the factory.

I already have a low-mile NB 5-speed sitting in the garage and I'm just waiting for GHM to have some time to install it for me.

In suspension news, we have a 11mm swaybar hanging in the garage for further suspension tweaking when the 5-speed goes in, and I have a brand new Long Acre Probe-type Pyrometer for taking tire temperatures at our next Houston SCCA event on the 5th of January.

We also had a BMW event last month that was a lesson in severe frustration, a frustration that all of my fellow competitors who ran on the Hankook RS3 shared.
Apparently RS3s don't work very well in temperatures below 60 degrees, and at 40 degrees they become downright SCARY when driven hard.
So the car was a balancing act of severe under-steer followed by severe power-over-steer once you got back on the gas.

It is starting to look like we will need to have a second set of 15x9s and some BFG Rivals sitting in the garage for cold events and add a rear-sway bar on top of it and/or a huge amount of bumpstop packers to the rear shocks to get the car to handle correctly with the tire switch.

Lots of testing and tuning to follow in the next couple of months.
have you thought about throwing in a 3.63 final drive? slightly shorter than a 5 speed and a nicer highway cruising RPM.
I gave it a little thought and checked out all the numbers on it and read some user feedback from people who had done the swap.
It seems that the 1-2 shift has to be done around 7200 RPM all the time or you fall a little too low in the power band, since the car still has to be a daily driver in traffic at times, this was unacceptable.
Another issue is that doing a diff-swap would not cure the sloppy-shifting of the 6-speed box which to be honest, is pretty vague compared to the 5-speed boxes.
It also as easy to swap as the 5-speed transmission or as easily reversible.
62 MPH at the top of second should work out perfectly.

The MSM really needed a 5-speed from the factory, why on earth Mazda thought a lowered redline and a 6-speed was a good idea I'll never know.
My fastest run from the BMW CCA event yesterday:

Official results:

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