Guess I'll just use this as my introduction. I'm new to ZX3's, but not to autocross. I started autocrossing in 2005 and have owned/autocrossed a lot of cars since then. My most recent autocross car was a 2005 Scion TC built for RTF (HS index.) Finished mid-pack with it at nationals, which was about where I'd hoped to end up with a non-Mini Cooper. I've considered prepping the car for STF, but after more research I'm realizing there are better cars for the class. I loved the torque of the Scion's 2.4L for corner-exit, but the weight was the real concern for me. In RTF trim, I got it down to 2776 pounds (race weight.) Which isn't bad for a starting curb weight of 2905 pounds. However, I think a full STF build would only get the car down to around 2700 pounds. That's still pretty heavy for a car that can only run 225's on 7.5" wide wheels. Mazda3's have similar power and slightly less weight, but are still a little on the heavy side. Enter the 2.3L Duratec ZX3... 2600 pounds and 149hp, stock. In STF prep, it seems reasonable to think it could get under 2500 pounds and over 160hp, (based on dyno charts I've seen.) 2.3 Liters means the car should have fairly decent torque. Also, the dimensions are pretty good. Somewhat short in height and length, and also pretty narrow. Operating costs for STF should be pretty low, and the car has enough power that it could still be fun on a road course. All of these things together, have really sold me on this car.
I've got a line on a very low-optioned D23 ZX3, and if all goes as planned, I should be picking it up next week. I'm pretty excited to build this car, as I think it could be a very strong contender in STF. Especially on larger, power courses.
I'll hold off on sharing my build plans until the car is actually in my driveway. At that point, I'll probably be asking a lot of questions on this forum. I'll also try to get pictures up once the car is officially mine.
What did you end up doing for a slider with the race seat? We are going to swap in the OMP's over Christmas break, and will need a slider for my co-driver.
Are you talking about the Massive rear conversion?, also I think there is some weight to be saved doing a l.w. caliper and 2 piece rotor up front. Who will get to 2300# first.
I think I have the Corbeau single-locking slider. I fabbed up the mounting bracket though.
I was just suggesting that there was weight savings to be had in the brakes. The Massive conversion does look like a good option. Have you found a 2-piece rotor or lightweight caliper for the front?
You'll probably get to 2300# first. I'm not willing to put in the money/effort required to get there.
Are you running extremely short springs in the rear suspension? I tried to install a set of spring adapters in the rear of my car and the only way the spring would sit flat is if I had very short springs (probably ~4 inch).
I've run 5, 6, and 7-inch springs. Mostly 6 inch. Also depends on the rate. A 300# 6-inch spring makes the car sit a bit lower than a 700# 6-inch spring.
Interesting, definitely report back on how you think they fair against the new breed of 200 treadwear tires. I saw some cars were getting it done on Kumho and BFG at a couple earlier events this year. I myself am going to jump on lemming wagon and get a set of RE71R's, mainly due to the fact I'm still poor, not buying new wheels and 16's are what I have, so, my options are very limited and the $70 rebate is very nice too. But, I would be interested to hear what you think!
Decided to shave the tires for autox use. Since I no longer have access to my own tire truer, I brought them to Gran Turismo east in Atlanta. They did a great job! Pic shows before and after. You can see that the tapered grooves got smaller after shaving, resulting in more rubber on the ground.
I have been reading the thread alot. I Just purchased a 2005 zx3 for the purposes of Auto Cross.
I am trying to find a solution for my lower rear spring seat. Not really having any luck finding what I need on google. I was wondering if you would share what you guys found to work with 2.5 linear springs..
The lower spring seat has a hole in the center, what fits in t here to take a 2.5 spring?
There are adjustable spring perches made, they are copies of those run by some Bmw models or you can buy the bottom plate from the circle track world which also use 2.5 if you don't need adjustable option. The adjustable option may only be available as a full suspension kit so you may want to look at Bmw suppliers.
I got the height adjustment going on the top of the spring perch. Just need something to keep the spring in place on the bottom. So no adjustment is needed
I just spoke with BC, so what I actually need to figure out is a Upper spring mount for 2.5 linear spring.
What was used in your guys solutions? They have a rubber piece that they made for Mazda 3's. That should fit, but they never tested, and it voids my warranty on my kit
how are you with a lathe?
my old KW coilovers had a lower perch that sat on that hole, with a plate clamping from below. I had a custom one made to give me more height.
the original part is the black piece in the pic. the silver part is what i had made.
I have access to CnC machines...but no experience using Mastercam or soildworks. With my time frame, I have to buy something pre-made.
That is neat what you came up with there. If if I had the offseason to prep, I could probably get someone to help me machine some parts.
...
BC just called and found a solution for me. Just need to pay extra for the upper adjuster cups. I'll post my own thread so I stop hijacking this one.
I have a pair of machined aluminum blocks, that hold the a 2.5 id coil over spring. with big bolts and washers to sandwich them to the lower control arms. I was going to keep a hold of them to use with my rally build. If you need them, email me at turbofbcrew@gmail.com and we can work out a deal.. I can shoot you a few pics .
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