Thread: Designing an NX for SCCA class FSM

I think that is the best way to go as well, unless you can do an exceptionally reliable turbo build, however, it would be more competitive IMO n/a. Why you ask? With the turbo you may have top end but having the boost build up will cause more wheel spin which just slows you down coming out of corners.

With less, I guess, "uneven" torque and power curves you will have a smaller powerband which will most likely result in unnecessary shifting just to be in the powerband. Going n/a you can have the ECU tuned to have a flatter torque curve which is what my parents had their SE-R tuned for. The car was able to pull out of a corner in low second gear with no trouble and less time loss compared to downshifting and the upshifting soon after.

I would think one could make a pretty fun maybe competitive car with the just the ve or avenir/t25 (which are dirt cheap for around $100-$150) at stock or low boost with some really wide tires. It is a good place to start for the experiment. If you are going the turbo route start looking at dual stage and electronic boost controllers you could change the boost mid course back and forth and just leave the car in second. And if I ever come into a tree that grows dollars bills it is what I will be doing

Unless you autocross on tiny little lots, you'll never downshift to first. Don't worry about that.

Don't worry about wheelspin, either. Unless you can break traction at will at any speed up to about 70 MPH, you don't have enough power. This is street mod we're talking about. A real diff with wide R-comps works a lot differently than the stock jell-o-box VLSD and street tires so many people with power run.

Then again, power isn't your first concern. A sorted out suspension that uses the tires well and a good diff come first. If you don't put in a Quaife (if you can find one) or Nismo diff, there's no point in going beyond a plain-jane 'DE. Tires, suspension, and diff are that important.

If you spend $900+ per set on wide Hoosiers that last half a season, you might be too broke to go whole hog on engine upgrades. If you go cheap on tires, all that money instead spent on the engine will be wasted on weak handling and traction. It's a poisonous path for regular guys!

Pat still hasn't reported on his experience with a B13 on 275/35-15 Hoosiers up front. $253/each, but so excellent to drive on. I'm driving a Neon ACR on 275 A6's (all four corners) this year that makes my SE-R's 225 front / 205 back A6 setup autocross like a snail in comparison.

Hey Jim, thanks for stopping by! The 275 setup would be just crazy on a B13. I would imagine that would be WAY too big for the 15x8 Koseis. Probably a 15x9, or 15x10 wheel would be called for with a REAL low offset. Then again, I think I have heard of some miatas running that combination. I still wouldn't mind running a front biased stagger. Maybe I can pick up a set or two of the hoosiers for cheap after nationals...

For the suspension, my setup is full ES bushings (including engine mounts), GC/AGX with 350# front, 250# rears (might be room for improvement on the spring rates), Superpro caster bushings, GC camber plates are on the way, and progress adjustable sway bars at both ends. Active tuning RSTB, Crappy FSTB (due for replacement; might just fab my own), and a BlehmCo LCAB.

I am going to try and get the block pulled this week (back issues are slowing me down), and then it will be off to the machine shop to validate viability of it, and perhaps the head, then go from there on what I start to build in the power dept. I had the DE set up with 87mm 300zx pistons, and a turbo head with a p&p job on it, but that may be so much scrap after the overheat/headgasket fail, so, we'll see. Just not sure if I want to throw the extra cash at a VVL (and maybe turbo), or just KISS and grab an avenir, and build and boost away. More research...

My SR20 wishlist for autocross would be: light flywheel, custom intake manifold and ITB's for fast response, more displacement, VE head with a supercharger or fast-spooling turbo for responsive power. No one should care about maximizing peak power. For autocross everyone wants broad, elastic, usable punch at any time, no waiting.

If you're dead serious, a factory BB/Avenir turbo manifold, turbo, lines, intercooler, etc., adds some weight. The simplicity, weight, and delivery of a supercharger would be something to try, but no one does them because cheap used turbos come over by the boatload (not a bad thing).

No matter what route you go, the chassis will always be playing catch-up. Our cars are limited by the camber curve of a McStrut, and can't fit much tire without being creative.

Your suspension setup sounds decent for the money. You could drool over really nice dampers, but the best way to go is to finish the engine, put some good tires on the car, and get some seat time. The cheapest and most reliable setup that lets you have fun is the best.

I wish Kumho V710's came in more sizes, because they're cheaper and last longer than A6's. Hoosiers will make you homeless if you use them all the time.

Alright, well I have decided to take the plunge, and go for boost! I have just bought an Avenir engine (not sure if it will be a W10 or W11), and I'll be popping in the BC stage 2's for some added punch. I am compiling the shopping list, and fortunately I already have a head start with some of the mods I had for the high-comp engine, including a lightened flywheel, AFPR, Calum basic ECU (with my own Moates Burn1 and chips to play with), Innovate! LC-1 based AFR. I am going to talk with one of the machine shops at the airport and see if I can get a deal on weld-reinforcing the B13 tranny. I am going to leave the door open for future mods including a T28, and perhaps adding VVL to the mix at a later date.

I looked at the idea of supercharging, and although it is as close as you get to all-motor characteristics while using forced induction, I was leery of the cost and heavy fabrication required, not to mention the path is not nearly as well worn as that of straight-up trubocharging.

The chassis/suspension is indeed the achillies heel. I am planning on foaming the chassis to promote rigidity without significant weight penalty, and I am addressing the MacStrut issues as best as able by inducing LOTS of caster (the equation runs 2 degrees of caster for every one degree of static camber. Thanks to Joe Cheng for help in this department). I am still pondering going for cup-car stiff spring rates (going that stiff will kill streetability). I have really tried to pick and choose the "best bang for the buck" approach to the suspension (thanks SO MUCH to ShawnB for his awesome suspension thread), and with the wider wheels/tires/track on the front, I am hoping to turn the NX into a G-machine, but I am still fully aware that there is room for improvement with progress, or CSKs. Like you said, Jim, get it on the road, get some more seat time, and go from there.

The Kumhos certainly represent a good value, and are my preference; the hoosiers are just too spendy at full retail for my wallet.

Well, I don't have any illusions of being able to get this all completed before the end of this season, but I'd be happy if it was up and running for a track day coming up the end of October. I won't, however, put a car on the track that isn't ready to be there.

Congrats on your choice.

Once you go boost you never go back.

Haha! Thanks man, and thanks for the PMs, by the way, they helped! A reply is enroute.

Also, thanks to everyone who took the time to offer up their experience, and opinions; I am fairly excited to get things underway, and get the NX back on the road, and on the track!

Darrin

One of my wheels was leaking and I sent it back to get fixed. Just drove it on the street for a few minutes to see if there were any rubbing issues -- had to cut off a very small part of the front bumper. They also rub the fender liners but so did 225 Kumhos.

Pat

Hey Pat,

Thanks for letting us know about yoiur wide tire choice. I am already prepared to do some fender pulling to accomodate the wide tires on the front, and I will probably mod the AGXs on the rear to prevent perch-scrape.

Things are starting to filter in now. The Avenir arrived a couple of days ago, and I just picked up a nice deal on a S14 T28BB for extra boost out of the box. The T25 has definite rotation issues (it won't), but the T28 was already in the plans. The GC camber plates and SHigspeed FSTB are enroute, as well as the Kosei 15x7 and 15x8s. Need exhaust, intercooler and piping, fuel pump, clutch, something better than the factory LSD... the list goes on!

Darrin

I need to make a shopping list, and start doing some damage!