Auto-x Questions
 

Thinking about trying my hand at auto-x. I have 3 questions after looking at the rules (Northern New Jersey SCCA).
1) I have a 74 with a 70 1.7 96mm big bore Dual webbers.
2) Is the stock seat allowed because of the tilt.
3) Do you need a roll bar and 4 point seat belts.
Any advice would be appreciated.

With the modified engine, you can't run in any of the Stock or Street Prepared classes. You may wind up stuck in F-Production, or D-mod. Those are "cubic dollar" classes.

If you run hard-compound street tires, you may be able to get into "Street Mod 2" or equivalent class, if local rules allow it. Still a big-buck class.

Stock seats should be fine in all classes. Not sure about the safety equipment in the highly-modified classes.

You may be able to claim your engine as a 2.0 one (it isn't, but they don't know that!) and run in C Street Prepared. A tough row to hoe, but still fun. Stock seat and belts are fine, no roll bar required. You would technically be breaking the rules, but 1910cc (your displacement) is less than the stock 2.0's 1971cc and shouldn't make much more power than the low-compression stock 2.0 motor. And I doubt anyone will protest you for a while--until you start beating people, which frankly ain't gonna happen right away unless you've got years of motorcycle racing (or some such) under your belt already.

--DD

It has been a couple of years since we auto-x'd with the SCCA but one thing you'll find is that the rules are the same all over the country, not like Porsche clubs at all. As for the class I think they allow carbs now since the FI system has gotten to be such a hard item to keep up but try to find who their chief steward is as he/she can tell you in detail what is allowed and not. As for the seat, the stock one is fine but remove the bottom pad to get you lower and use a harness bar and belt system to strap you on very tightly. Also remove the wiper assemblies so you won't surpreise yourself when you accidentially hit the lever. Good luck.

PLEASE be very careful. This is what happened after I went to my first autox 11 years ago. I got it BAD!! http://forums.pelicanparts.com/uploa...1064281758.jpg

Dave's right (again). You can't technically run in any of the stock or street prepared classes with the set up you have, but unless you're running at the top of your class you can pretty much run where ever you want and no one will care. Welcome to the addiction!

I've got another auto-x related question for the group: I'm running a stock '74 2.0 in the SCCA C-Stock class, and I'm consistently tenths of a second behind the class hot shot in his Miata. I'm looking for the last couple of tenths for this weekend. If I can win the class we'll be neck and neck for the year end points total. Any advantage to running race gas in a stock motor? What if I also advance the timing to take advantage of the higher octane and build more cylinder pressure?

Well Mark several things to check: Install a factory limited slip (no penalty), solid motor and tranny mounts, use a roll bar with brace or a cage (stiffness), run as low tire pressure as possible till you get too much roll- over, short shift on straights, use as little gas in the tank as possible(less weight), use as light batt. as possible, if allowed keep right side window up (better aero), keep the top on(better aero), lower the car as much as possible, use wheel spacers (but check the rule on track width) to make track wider, get a corner balance, wax the car really well and use Rain-X on the windshield to reduce drag. Some things sound silly, but a few .001's here and there add up to a .01 here and there and that gets you into first!

I have heard conflicting things about high-octane fuel and timing advance. I would at least give it a try. Note that it will be real hard to get a good idle when you advance the timing--it will likely idle very high.

Best bet on that is to get yourself to a dyno and do some test pulls. You may be able to adjust the FI as well--there are built-in adjustments for fuel pressure, and you can probably argue the MPS adjustments as well. (Though they are sealed from the factory, so I'm not certain on that one.)

I don't think the solid motor and tranny mounts are legal in stock class. Check the rules to be certain.

I assume you're running Hoosiers? If not, switch to them and re-learn the car on the new tires. And be prepared for your tire budget to go through the roof....

--DD

Hey, all just wanted to give you a quick update on the race gas thing. I bought some 114 octane fuel, put it in the car, and advanced the timing to 37 degrees total (about 10 at idle with the vacum disconnected). Seat of the pants evaluation: it doesn't feel too much different. But it sure sounds a lot better. Difficult to describe, but overall a little deeper sound and definitely smoother at all points in the RPM range.

At the autocross last weekend it was difficult to quantify if there was an improvement or not. The Miata I usually run with didn't show up. But, good news is I had 3rd fastest time on the course for all groups!

Whoa, I'll bet there was a lot of unburned fuel in the exhaust and some crackling and such when you let off the gas?? I don't even use that high of octane with 11 to 1 compression, but what the heck, it is worth a try. Did you play with tire pressures any and if so what were the results?

And I doubt anyone will protest you for a while--until you start beating people, which frankly ain't gonna happen right away unless you've got years of motorcycle racing (or some such) under your belt already.

Dave- tell me more. How does bike racing factor in? (And where do I put my knee pucks?)

John, acutally no. I expected that it wouldn't idle well and would run rich, but it didn't. No popping on let off either; but really during an autocross circuit the exhaust system doesn't get all that hot. There may have been a lot of fuel, but it wasn't hot enough to ignite it. Other than a K&N filter and Triad muffler, the drivetrain it totaly stock. Maybe the improve breathing afforded by the two mods are enough to lean it out so it worked well with the higher octane stuff. I think as Dave suggested, a dyno is the only way I'll know for sure what's on.

Mark, are you running SSI Heat exchangers? They are bigger than stock units. 30-32 degrees advance is about where the most power is on a stock motor. Take the air filter off if they let you. Try bumping the fuel pressure up to 31 lbs to richen the mix alittle or have the MPS adjusted richer at WOT as they are usually too lean or find a stock unmolested 037 MPS that is richer out of the box.

Just trying to find a few more hp for you.......

Geoff

Thanks for the tips Geoff. Yes/No on the SSI exchangers. I'm not sure who the maufacturer is, I bought them at a swap meet, but both the tubes and surrounding shell are stainless. I measure the I.D. when I put them on and they were the same as the original 2.0 exchangers.

Short of an exhaust gas analyzer, any way to determine if it's lean now? Plug readings look good (but with unleaded fuel, that's not too reliable), no missing, popping, studdering,.. indicating a lean contidition.

I think SSI is the only one who has made stainless 914 exchangers.


As for the motorcycle racing thing, it gives you a very good "feel" for how the car reacts, gives you a very good appreciation for the "line", and gives you very good reflexes. ...If you survive... ;)

Some of the best autoXers I know, locally, used to road-race motorcycles (this is Big Track stuff, here) before they got into four-wheeled fun.

--DD