Thread: Designing an NX for SCCA class FSM

Well, after lifting the head on my high compression all-motor setup, the lure of a turbo car for AutoX has me. While this thread might be better suited to the VVL or turbo section on first blush, bear with me, as I think the folks here will have a better take on the application requirements.

What I am trying to decide is whether I should stick with a mildly built avenir setup (or even a DE+T), and upgrade the turbo to a T28/360 degree thrust bearing mod, or head for the deep end with a VVL head/T28 combination to keep it interesting. My power goal is approximately 300HP (dictated by the tranny life).

Bearing in mind it will be an AutoX/light track machine with the occasional DD duty, what seems to make the most sense? I already have minty fresh BC stage 2s ready to drop into a motor, so they are a shoo-in for the avenir/DE+T. One thing that comes to mind is I will be racing, therefore breaking stuff, and parts availability/time required to aquire has me concerned with the VVL (one reason I ruled out a GTiR swap). Bang for the buck comes somewhere in the equation as well, and because of the catastrophic failure of the last one, I am buying an engine, regardless, so I have a clean slate.

I have seen lots of talk about the horsepower potential of the VVL engine, but not alot of talk about the torque, and that's what you really need on an AutoX course. From what I have read/researched, the avenir has lots of grunt, and it seems to be a bit more suitable for the application, but... well, I need a bit more experience coming to bear on this.

I'd appreciate hearing from folks who have done this, guys experienced with a turbo setup and AutoX, whatever. I've done a fair amount of research, but I am to the point where I need to ask questions to figure out what will be best for me.

Looking forward to hearing your thoughts!

Darrin

I've always thought torque was not desired in a FWD chassis for auto cross. I always envision tire spinning madness at these slow speeds. I'm not sure you do want torque, not to mention you describe trying to keep the transmission together. As for the VE head, you can expect more torque from it than a DE or DET head.

I'm reminded of the Car & Driver sponsored RSX that won the road course challenge against many other magazine sponsored RSX entries. The C&D team had the least power (230 WHP or so) where other teams had over twice that.

I'm a bit biased, but I like the idea of the 9.5:1 CR DE plus T28 combo. I'd also recommend a low port head + intake which are just as easy to find as the high ports. You'll keep the transmission together, parts and replacement engines and such are the cheapest you can find and you can make the power you're after easily even without the cams.
Switching between cams and boost levels should also provide you with many options for torque/power.

If I'm wrong about the torque and tire spin (maybe warm, sticky tires are doing wonders these days) and you really do want all of that power early on, I'd still do the same setup, but make sure to use the BC cams and run a whole bunch of boost.

It sounds like you're set on the turbo idea and FSM class, but something tells me a real nice N/A VE setup would be competitive, but I'm not sure you want to go down that road.

Hey Ben, thanks for your thoughts.

I've been doing the N/A thing, and while fun, I know I'll be wanting to go turbo at some point. The VVL all-motor would probably be a hoot, and it would still keep the door open for future VE+T goodness. That may end up being the best path, although probably the most expensive overall.

As you mentioned, wheel spinning madness might be the result of a torque monster, so the ability to modulate the power will be important; power, without control, is nothing! The car will be getting lots of tire on the front, so I hope to compensate for that, along with suspension to keep the contact patch optimized. I am most concerned with controlability of the VVL+T setup; from what I have seen, cam switchover+boost=WAY non-linear output, with very difficult modulation; that could, however be a combination of tuning/driver input.

What exactly is lots of tire up front?

If you decide on the VE turbo or NA. You will find your self downshifting to first alot. Thats not necessarily a bad thing, depending on the course setup. The next thing would be a good LSD to help with traction. Don't be discouraged with the Modified class and run slicks, fun, fun.

*puts on flame suit*

"lots of tire up front": I am thinking 245ish, in a Kumho (our club sponsor) or Hoosier. I will be bumping the fenders to allow for the wider wheel/tire combo, and running a low offset on the front in a front stagger configuration to increase the front track (Caroll Smith was a big believer in wide-tracking the front end). The suspension discussion could be a thread all it's own, but that's the plan.

A good LSD will have to go on the shopping list, for sure, otherwise the inside tire will take a lot of punishment.

Downshifting to 1st might have to go into the bag-o-tricks (kind of a PITA with the B13 tranny); I can see how you'd be faster than waiting for the motor to pull out of the hole.

You might be okay with some torque with that tire. I stick with my second recommendation then. 9.5:1 DE with T28, BC2 cams, and bunches o' boost.

DET (oil squirters) might be a better idea if road racing is a common, high possibility.

I just saw a thread where a guy stuck 275s on the front of an SE-R here which would help a lot I bet.

I am assuming you are going to run CSKs and Ground controls and work on getting stiffer springs for the ground control perches? or you can buy the ebay coilovers to use the top-hats and adjustable bottom part.

I don't know too much about the engine setup you are wanting to run, but torque is good for autox, especially bottom end for smaller courses. Sure you might have to feather the throttle sometimes, but if you have good enough tires you won't need to as much.

If you want to race, you want to be realiable. Keep it NA. Even with little tuned DE, its a lot of fun if you have good suspension/brakes/tires.