Autocrossing the 510 - Advice?

[demo243]

Ive done some searching and havent found any threads dedicated to this-

 

If you have been following my thread - http://community.ratsun.net/topic/46032-red-71-4dr-first-510-streetautocross/ - you'll see I have finally pulled the trigger on AutoX'ing the 510- getting pretty stoked for it, hoping to get her finished up this week so I don’t have to rush anything next week.

 

I have signed up for Rookie school and the first no points race- so the 23 and 24^th will be a full weekend of racing for me.

Never done this before so looking for advice –

 

I got some of the basics- Tire pressure higher then street – make sure there is nothing in the car- make sure everything is bolted down ect – anything else? What do you guys bring with you…? Also I need to get a helmet- anybody have any suggestions? Open face or closed?

 

Bad news is I don’t have a trailer so I have to drive her there- that means I can’t easily just load tools and everything into the back of the truck-  I can bring them with me, they will just have to be loaded in the Datsun and left out in the lot while I am racing.

 

Good news is the venue is about 15 minutes from my house so I can drive her there and isn’t a huge deal if I run into a problem.

 

Also I have no clue what class I fall into given the modifications to the car. I tried digging up a description of the classes but was unable to really come up with a good feeling for what class I would race in.

 

Details on the car – ’71 510 4 Door- Fully gutted -4 point Cage- 5 Point Harnesses – L20b with Dual Weber DCOE40’s – 5 speed transmission, not sure what it came from… - Lowered with lowering springs /Bilstein Struts– big fat sway bars- Porterfield R4-S pads/shoes- Goodrich Stainless Steel Brake Lines- Fresh ATE Brake Fluid -  Got some used Federal 595s with some camber wear on them, hoping to just get a season out of them – a bit worried about the exhaust as it seems to be fairly loud inside the car, not sure about outside the car as I have never heard it from that vantage point at high RPMs-  basicly just a straight pipe to a flowmaster muffler, not sure which one.

 

Thanks in advance!

 

Devon

[HRH]

Open face helmet is best.  Autocross is one of the safest "racing" sports out there.  I put that in quotations because it is one at a time with cones.  It's still racing, but it's not wheel to wheel or rally where the possibility of hitting trees is imminent.

 

The two biggest things in autocross are:

 

1.  Look ahead.

2.  Slow is fast.

 

On point 1, you need to know what is coming up before you come up to it.  Drive the course as you would a curvy mountain road, always straining to see the farthest thing away to react quicker.

 

On point 2, drifting is cool, tire smoke, sliding sideways, etc. but it's not fast.  The fastest cars are the cars that are the most in control.  A lot of times they'll look slow.  Stopwatch doesn't lie though.

 

You will have a slight problem depending on your competition.  Being you have "engine-swapped" your car, that will likely put you in a SM pax index, which means Street Mod, which puts you against motor swapped and turbo-equipped cars.  With good suspension and brakes you'll probably do alright.  However, if you're still working the bugs out, you may well get spanked due to being in the same class as 200+ hp turbo cars who can just plain out-run you.  I had that happen with my L20b in the 510.  Still did reasonably well, but couldn't get first. This next time around I plan to do quite a bit more suspension work.  I haven't raced autocross in about 2 or 3 years now.  Back in '06-'07 I had 2nd in CSP in my Miata for two seasons in a row.  Missed 1st the second season by 4/10s of a second.  Ain't that about a bitch!? :)

[510T]

Pinned in the suspension section, lots of good info:  http://community.ratsun.net/topic/47668-looking-for-input-on-alignment-for-an-autox-setup-510/

 

I am also going to be dodging cones for the first time soon :)

[datzenmike]

Lower tire pressure will give more grip than higher.... within reason.

 

A five speed doesn't really help here.

 

If this is a purpose built car, you should look at getting a 4.375 or better, a 4.625 R180 for the back. This will multiply your torque at the expense of top speed. You probably still won't get into 4th but will really improve your acceleration.

 

Lowering to the max will also lower your center of gravity making the car less 'top heavy' and less prone to leaning in corners. Stiffer springs will help too. Beware rear sway bars. They increase over steer, unless you have too much under steer you want to get rid of.

 

Mounting the battery in the trunk can help remove weight from the front and lower the center of gravity.

 

If you ever have the motor out a lightened flywheel is good. Less power is used spinning that heavy weight up to speed and more is available to move the car. Any part being turned by the motor that can be lightened, frees up power available to move the car. Maybe a pair of the 240Z aluminum drums?

 

Reduce weight. Get rid of the wiper motor and wipers, horns, heater assy, replace door glass with Lexan plastic,

[Stupid_fast]

Beware rear sway bars. They increase under steer, unless you have too much over steer you want to get rid of.

Larger front sway bar increases understeer.

 

Larger rear swaybar increases oversteer.

 

Everywhere I've seen except what you say has said this.

 

I can see in some situations, the increased steering response by a properly sized front bar can decrease understeer.  But I'm no pro. :)

[HRH]

On tire pressure, it depends on if you're on street tires or actual race tires or stickier tires.  Street tires need to be at the top of there pressure range due to the side loading where the edge of the tire rolls over.  Regular driving pressure in extreme cornering will cause the tire to deform if pressure is too low.  Most street tires need to have a shitload of air in them to handle the rigors of autocross.

 

Slicks however, follow the less is more rule.  One of the easiest ways to figure this out is to take the shoe polish and make four dots on the sidewalls of your tires.  (Common autocross practice)  As you make runs, you look to see how much of the dot is worn away in cornering and increase air pressure until you're not coming over on the sidewall.

[RMS]

make sure you brush your teeth!  your guaranteed to support a big grin all day :D

[datzenmike]

Larger front sway bar increases understeer.

 

Larger rear swaybar increases oversteer.

 

Everywhere I've seen except what you say has said this.

 

I can see in some situations, the increased steering response by a properly sized front bar can decrease understeer.  But I'm no pro. :)

 

 

You know, I always get it wrong. I see it in my head and type it and it looks right.... but it's not. Thanks.

 

Most all cars are designed with slight understeer in them. The reasoning is that it's the easiest to recover from... simply let off the gas and/or hit the brakes. Weight shifts forward and understeer is reduced.

[demo243]

make sure you brush your teeth!  your guaranteed to support a big grin all day :D

 

 

Haha thanks this is probably true!

 

At this point I really am not going at it from a competive standpoint- I understand I will be up against more powerful cars, experienced drivers yada yada yada... and I am not at the point of swapping gears ect to increase performance- 

 

I am really just going at this as a way to have fun and safely push the limits of my car and my driving skills- im sure the competition will be there- who doesnt want to go faster then the other guy- its more just a place to hoon my car with a bunch of other people that want to do the same.

 

really just looking at how to make the most of the day and have the most fun-

 

 

on a set up note- battery is in the back already and the car does seem to handle quite neutrally- although i havent truely pushed her since i havent trusted the brakes or tires and really dont want to wrap her around a tree or worse hit someone else.

 

End of the day she is a street car that can be raced- just stoked to go drive here how she was built and how I want to