Setting Up a 1989 240sx for Autocross

I'm planning to use my '89 240sx as both a daily driver and a weekend autocross car. I know that what is most important for this is good suspension and tires, but I'm not sure what would be best to start with (particularly with the suspension). I'm not a huge fan of the idea of lowering the car, but I'm willing to if it is necessary. Any helps or tips would be great.

Thanks ahead of time!

LSD will be a huge gain in traction and can be done cheaply (junkyard).

I tried a few different spring/strut combos over the years but wasn't impressed until I went to coilovers. They allow height adjustment, damping adjustment, and swapping springs to get the correct rate for your driving style.

I don't remember the issue, but GRM interviewed Jason Rhodes after he won the ST Nationals in an S13. He had since moved to SM, so he revealed just about every detail of his setup. I used it as a blueprint for my build and it payed off well.

But most of all, and this applies to all makes and models, just go out and drive! Seat time is the most valuable upgrade available to you.

I'm a firm believer that that best "first mod" for autocross is an entry fee. (It's also the cheapest, BTW) The thing is, classing rules in autocross are a bit complicated, so the first mod done incorrectly can have you racing fully prepped cars which are WAY out of your league. You need to figure out what class you are modifying for before you do ANYTHING to your car. The two suggestions I'd make to figure out classing are (as above) 1. going to an event and asking the dude there wearing the biggest hat (who will, invariably, be one of the experienced racers of the club) if anyone in the club races S13's and would know classing and 2. maybe finding an S13 specific message board/forum/club which has an autocross sub-section. Either spend time reading there OR post the "Please help a noob with classing" post, wade through 16 pages of "Search noob!" and somewhere in the drivel someone will likely be nice enough to give you a basic breakdown of available classes and a recommended mod path. Mods will not make you competitive if you don't know how to drive, but can quickly make you a backmarker (even if you have talent) if done incorrectly.

Cliff notes: Don't do any mods without research and a clear path ahead. Go to an event, race as is, where is, in whatever class they put you in. See if you like autocross enough to stick with it.

I'd love to find that issue! I'm not the autocross (to compete at least) type, but I'd love some tricks to dial in my S13... once it runs again

Junkyard LSDs are an option if you can find one that isn't worn out. Best non-budget option is a Quaife. There are some good coilovers on the market at reasonable prices as long as it's from a reputable brand (not Stance, Megan, etc). I have KTS on mine, there was some shock dyno work done for these back in the day when I picked them (2005 maybe? I've been out of the loop in the Nissan community for years).

I'd start with a second set of wheels and new tires for the dd duties and use your o.e. suspension, wheels and worn tires to learn the ropes of autocross.

Tire pressure can change the cornering behavior of a car. I've never flogged a 240 so I'm not sure where to baseline your pressures at but, if it were me, I'd start at 40 psi front and 32 psi rear, mark the shoulders with white shoe polish then tune from there.

Fresh fluids (high temp brake fluid), performance brake pads and I think your car is old enough that you can upgrade to braided stainless brake lines and stay in a stock class.

jsquared wrote: I'd love to find that issue! I'm not the autocross (to compete at least) type, but I'd love some tricks to dial in my S13... once it runs again

I keep that issue in the 3 ring binder I have my other S13 technical articles in. He gave spring rates and alignment angles too. I think that was the biggest money/time saver for me. No need to spend a bunch of time with hit and miss alignment angles.

I'll try to remember to dig the issue out when I get home tonight for specifics.

I'd say it worked because I was able to win the regional SM class in 2013 with a naturally aspirated SOHC.

Obligatory photo

nissanroadracing.com

Mostly auto X info, some track day and road racing folks too.

Koni Yellows with Ground Control style sleeves are the easiest route to decent dampers. You want to lower it a bit, the front especially is super high in stock form.

You can get a helical style LSD from Japan (s15 only) for about $500, which is worth it rather than the worn out viscous units out there in junkyards. Beyond that, some OE parts wear out easily like TC rod bushings in front and subframe bushings in back, so replacements can help a lot.

Cone_Junkie wrote:

jsquared wrote: I'd love to find that issue! I'm not the autocross (to compete at least) type, but I'd love some tricks to dial in my S13... once it runs again

I keep that issue in the 3 ring binder I have my other S13 technical articles in. He gave spring rates and alignment angles too. I think that was the biggest money/time saver for me. No need to spend a bunch of time with hit and miss alignment angles. I'll try to remember to dig the issue out when I get home tonight for specifics. I'd say it worked because I was able to win the regional SM class in 2013 with a naturally aspirated SOHC. Obligatory photo

NICE! To win anything with an NA KA-E is an accomplishment If you could scan that article I'd send you a beer/donut/equivalent

RE: I usually had tire pressures even front-to-rear on mine. They are not quite 50/50 but a stockish S13 should be around 52.5% front.

RE: the S15 diffs, I forgot about those but something in the dusty back corner of my mind says there was something odd about the housings on those, speed sensor made the nose longer or something? Might have been the 6-bolt vs 5-bolt axle flanges, can't remember.

kazoospec wrote: I'm a firm believer that that best "first mod" for autocross is an entry fee. (It's also the cheapest, BTW) The thing is, classing rules in autocross are a bit complicated, so the first mod done incorrectly can have you racing fully prepped cars which are WAY out of your league. You need to figure out what class you are modifying for before you do ANYTHING to your car. The two suggestions I'd make to figure out classing are (as above) 1. going to an event and asking the dude there wearing the biggest hat (who will, invariably, be one of the experienced racers of the club) if anyone in the club races S13's and would know classing and 2. maybe finding an S13 specific message board/forum/club which has an autocross sub-section. Either spend time reading there OR post the "Please help a noob with classing" post, wade through 16 pages of "Search noob!" and somewhere in the drivel someone will likely be nice enough to give you a basic breakdown of available classes and a recommended mod path. Mods will not make you competitive if you don't know how to drive, but can quickly make you a backmarker (even if you have talent) if done incorrectly. Cliff notes: Don't do any mods without research and a clear path ahead. Go to an event, race as is, where is, in whatever class they put you in. See if you like autocross enough to stick with it.

What he said. Though I'd first pay several entry fees, not just one.

1. You learn enough about driving what you have. I've seen people spend tons of money always tinkering with the car for naught. They change everything except the actions of the nut pushing the pedals.

2. You learn a lot more about the competition and see the rides which didn't show up on your first trip.

3. Usually if someone else has a ride even somewhat similar to yours, you can learn a lot of what does & doesn't work at their expense.

There are two different diff housings for s13s out there. Short nose (early production) and long nose (later production w/ ABS AND the j30 diff). The longer nose is because it needs extra room for the speed sensor. There are also two different flanges for axles, 5 bolt and 6 bolt. From what I understand the S15 helical diff is drop in as long as you change the flanges because the s15 has 1 more or less teeth.

I have a JY j30 VLSD diff I picked up for $60. It was a long nose that replaced my stock short nose. Rumor has it you can still use the stock driveshaft, but I used the opportunity to buy the appropriate (shorter) one piece aluminum driveshaft while I was doing the swap. Definitely better than an open diff, but is geared a little taller. I make up for this by running smaller diameter wheels.

My next purchase planned is an S15 diff from ebay that comes with the matching flanges. Seem to go for about $500 shipped.

Difference in length between the driveshafts-

j30 diff. Some have the 6 bolt flanges, so direct bolt in. You could also see the speed sensor sticking out the r/f of the nose.

Made sure the VLSD was functional

That sounds right (flanges). I've seen some pop the pumpkin open and swap the ring gears I think... again, it's been a while

In reply to jsquared:

That's my plan. Buy the s15 helical, use my long nose housing (because I have the driveshaft), and swap in my stock ring gear.

Hmmmm, for auto cross a big thumper (torque) is often useful. Its a single cam... so I wouldn't try to make it a screamer, I'd look into make it MORE of a thumper. Typically a head "rebuild" is allowed in most classes, you can get a 3 angle on the seats and it should allow for some improvements. You might also look into getting the "squish" (gap between piston @ TDC and surface of head) as tight as possible.

The SOHC KA is still used in one of those IT classes or some such (or was popular... 8-10 yrs ago? LOL I've been out of the Nissan crowd for too long), the roadracers might know some tricks to grunt up a KA-E.

That can be done by milling the head and block to maximum specs. That's what I did when I was building my car for ST, then DSP. Got compression up to 9.7 to 1.

The torque of the SOHC does really well in auto-x.

I can't count all the times I've had people peer under my hood during Tech and have their jaw drop. Everyone expected a V8 swap or at least some sort of boost

Eventually I added a cam and porting. Bam! Now I am in Street Modified with 500HP beasts!

If you can wait, the issue that just went to press shows how we took our S13 on track. The works was minimal. (Hint: tires, brakes and not much else.)

Thanks for all the help guys. I plan to take my S13 out a few times before I do any modifications but I still wanted some ideas for what might help. The only thing I might do before I go to an event is get some new tires... but it needs them anyway.

The tip about the fluids was also very helpful. I'll make sure to put some money aside for some of these mods in the future as well!

By the way, thanks for sharing that you did so well in your S13, Cone_Junkie. I've only heard of one 240sx within the group I'll be in, and it's an S14, so it's awesome to know I the car does well. It's also good to know that some good can come from a N/A SOHC, despite what people say!

Thanks everyone! Any more tips are completely welcome :)

There was a guy that went to a lot of the NC/SC autoXes about a decade ago (man, I'm feeling old!) and had good springs/dampers and a lot of suspension dialing-in time and with a near-stock KA24DE was running better times than some of us with modded SR swaps. Nut behind the wheel and all that plus the right mods dialed in properly.

David S. Wallens wrote: If you can wait, the issue that just went to press shows how we took our S13 on track. The works was minimal. (Hint: tires, brakes and not much else.)

But, but... I want it NOW

(just kidding)

I had great local success in my 89 240sx when I had it. It had the koni/GroundControls, urethane bushings, adjustable control arms to get the alignment in check, and a HICAS model rear away bar. Fun car. I sure miss it sometimes

Obligatory pic