200sx SE V6 Endurance Race Car Build

[Max]

Huge apologies for not keeping up with this.  The race car has been finished.  Please ask if you want to know anything specific about the build.  I know the thread is not current, but I can comment and add pictures on any area of the car... just ask!

​
Epic update:

I know its been a while since the last update.  Basically for the last three months I've been worrying myself sick trying to prepare the car for PIR, and studying for the PE exam (9.5 hours long) which is the day before we tow the car to the track for tech.  Impeccable timing!

The car's first race was last weekend at Portland International Raceway with LDRL 8+7 with 45 min. night sprint.  This is where it all started for Chumpcar back at the 24 hour race on Halloween 11 years ago.  That is also where I got hooked, volunteering from pit lane.   Only 11 years later, I'm returning in my own car. 

Three team mates put their faith in me and signed up enthusiastically to drive.  Funny thing is, the original team all dropped out at various times for various reasons.  This team came together in the last month before the race.  Two former team owners (rx7 & e30), and one friend that I attended UTI with 12 years ago who's never driven on a road course.  Basically, I was worrying myself sick that the car I'd spent two years preparing to race would break on these drivers that gambled on me and the new car.

Strategy was pretty simple for Saturday's 8 hour enduro, as I knew the odds of things going as planned were slim to none. I wanted to get all my drivers seat time before I got in the car. Just in case there was any incidents that kept us off track, I didn't want them to miss out. I asked them to stay out as long as possible, basically until the car started to stumble from low fuel.  I was pretty sure that with a 14 gallon tank, the car would only go about 1 hour 40 minutes. So with any luck we could get it done in 5 stints. 

 Qualifying:
I put my friend who'd never driven a race car before in for qualifying, to hopefully work out some novice jitters.  This worked! One spin by himself in the chicane, but otherwise trouble free.  

Start:
For the start of the race I put our most experience driver in, who had campaigned an FC rx7 for about 8 years.  He kept us out of trouble for the start, and started to get comfortable in the car he'd never driven before.  Everything went to plan, but then it started to mist pretty heavily.  About 30 minutes into the race and we see him coming down pit lane.  He informs us he had a huge spin in turn 11, which is a darn fast corner.  Luckily, after spinning a few 360's, he came to a stop without hitting anything. He pulled right into the pits and said he thinks something is wrong on the back end of the car. We checked it out and couldn't find anything, sent him back out and told him to take it slow.  Ok, first unscheduled pit stop, but hey we know we're not going to win today. About 1:35 into the race, he comes in for the end of his stint. Fast lap 1:46.1, half stint was in the wet.


First fuel & driver change:
Got our 1st driver out of the car, and I started fueling.  Holy crap it's taking fuel slow.  I need to modify my filler neck to make these hunsakers dump faster.  Car took just over 10 gallons, not good in a 14 gal tank.  Driver reported about 6 laps of sputtering in the tight right hand corners.  Put our next driver in, the rookie.  Also went from our biggest driver to our smallest driver, and this was challenging with a fixed mounted seat.  I need to relocate my lap belt mounting point on the door side, as it was dang near impossible to tighten without hurting yourself. 


Second stint:
Uneventful!!! My buddy who had never driven a race car stayed out of trouble, kept it on track, and brought it home for the next driver.  No rain thankfully. He lasted an hour and fifty minutes before sputtering, was not as fast as the first driver but was able to do some laps in the 1:46's.  Learning how to go fast can come later, I think he learned a lot about managing traffic and driving predictably.  Two criticism's I have are that he left the popups up the whole time, and put the steering wheel on crooked.  The ONLY video that worked all day was 50 minutes of this stint. I guess it's good that we got video for the new guy!
 

https://www.youtube.com/watch?v=zPNAfm0JLGk

Second fuel & driver change:

Same deal but smoother than before.  I put another 10 gallons in or so.  3rd driver is in (former e30 team owner), and off. 
 

Third Stint:
This stint was going smooth, and our lap times started to come down.  The track was still dry, and she was able to set a few times in the 1:45's.  After about 15 minutes the driver comes in for an unscheduled pit, and said the rear brakes are howling.  I asked if the brakes are still working, and she said yes.  I explained I think this is just the pads.  I don't know why they're howling but I suspect that there's too much rear bias, and the rear brakes are working too hard and getting too hot.  I used hawk blue front and rear, and I'm kind of thinking I should have staggered compounds and run a less aggressive pad like HP+ or HPS in the rear.  I told her to go back out and be careful in the braking zones if she felt comfortable.  She said she's having fun and wants to keep going. Alright!  Hour and a half total stint time and she comes in saying it just started to sputter. 

 

Third fuel & driver change:

O

M

G 

The car made it this far, every driver has had a full stint.  I can get in the car worry free now, just icing on the cake from here on out.  The stress is melted away and it's time to really enjoy the fruit of all this. No idea how fueling went, this was all a blur. 

 Fourth Stint:
I've been waiting for this moment for my entire life!!!!  In July I did a track night and was able to do a 1:41.8 on some older RS4's.  I have new one's today, and improved some bushings, new clutch, and cut the rear springs more, so hopefully I can be faster.  Basically we started from the back of the pack at the beginning of the day (50 cars or so total) after our spin & unscheduled pit stop.  Every driver moved us up a couple of spots and we were sitting somewhere around 26th overall by the time I got in.  I start getting settled in to the car, and lap times start dropping.  The body roll is still horrendous, but if you're patient with the weight transfer the car actually has some good mechanical grip. Pretty soon I'm beating my times in the 1:41's, 1:40's, and then a 139.9 and our fastest lap of the race.  I keep this up for a while but keep getting caught up in full course yellows, including one for an e46 that went into the wall right in front of me.  For some reason the car doesn't seem very fast to me despite burning off fuel weight, and running the engine up around redline causes a feeling of power surging.  Pretty soon I started to see my tachometer wigging out and flickering, and I'm suspecting an ignition problem, like a plug wire or something coming loose.  It seems like randomly the engine is down a cylinder.  About an hour twenty in to my stint, another full course yellow.  I putt around in 5th trying to save fuel as it basically reads empty, but no sputtering yet.  Green flag drops and I'm battling to keep some cars behind me, one specifically that I know is in my class. I actually want to race even though I might be battling for a position in the teens. Things went well for half a lap until we get to the hairpin, turn 7, which leads to the back straight.  I manage to stay ahead of about 3 cars setting up for turn 7, point the car and lay into the throttle...  All three of the cars fly by me on either side like I'm not moving.  I pump the throttle and just hear a really loud rattle.  Wot only results in me maintaining speed, but almost no accel.  I limp to the pits and inform the team that we lost the engine, suspected spun rod bearing.  Turned the car off and we pushed it into the cold pits.  After that, we tried to restart the car and it wouldn't fire.  Ultimately, I spent an hour testing to find out that the electrical problem I was experiencing was a battery cable crimp that was coming loose at the battery under the shrink wrap. Found out my battery mount was inadequate, and probably stressed that crimp until it failed.  Fixed that, fired the car while we were all listening... pretty obvious rod knock.

Our race is over.  We loaded it on the trailer and loaded up our pits. Missed out on the night sprint, and the Sunday 7 hour enduro.  Honestly the whole week was a rollercoaster and highly stressful, and I left the track feeling really incredible about how it all turned out.  The team seemed to be in good spirits despite losing out on the rest of the weekend, but there was also some relief that the new car was a blast and we all drove a lot.  We were also freezing our butts off, so that could have contributed!

 I also got a lot of love from the organization and other racers. Many compliments on the new build.  Some even called it "clean" but I would say they must not have looked very close.  Overall a really positive race weekend with a great group of racers. 

Takeaways: 

Obviously I need a new motor.  Picking up a vg33e core on Thursday to rebuild over the winter.
Need stiffer springs bad.  I think my cut springs are probably around 200 lb/in.  Will probably shoot for 350F300R.
Hydramat or surge tank.  We need to use more than 10 gallons of our 14 gallon tank. No money/time for a cell.
​Radios.  They would just be really handy.
Video.  Would like more than 50 minutes of working video.
Diff.  Currently open, if budget allows I'll get an LSD.  If I'm feeling really brave & broke I'll weld my diff. 

I just can't wait to get back out there.  Thinking about doing both PIR events next year. 

[CzechSilvia]

Great read! Get it fixed fast so you can humiliate some drivers in the newer cars

[Max]

Thank you! I will do my best.  There are 2 races a year at my home track, and that's probably the only one I'll do for the next couple seasons.  Those are in June or July, and October. 

I think we'll need to drop about average 3 sec/lap to be in contention for podiums. Better springs will get us close to that, and if I can get an LSD or locked diff I think we could be there.  I will be rebuilding a vg33e for the car, and probably adding some mild camshafts which should help to a lesser extent.  When we're 3 sec/lap faster, and can use almost all the fuel in our tank, and we don't screw anything up majorly, we'll be competitive!

[kelso840]

Way to go out there and represent our chassis!

Are there any aftermarket parts you can use in the rebuild to help the engine survive a whole race?

[Max]

Way to go out there and represent our chassis!

Are there any aftermarket parts you can use in the rebuild to help the engine survive a whole race?

That's a good question. 

Long answer: First off I think that a lower mileage vg33e from a 2003ish truck is going to be more reliable.  They have revised oil pumps, and mine was an oil related failure.  Also, the engine I blew up had an odometer stop at 242,000 miles and was apparently on it's original motor.  So just by putting new rings and bearings in the vg33e should make for a much more reliable engine.  I have considered modifying the oil pan to hold more oil, and add trap doors to try and keep the pickup always in-oil.  A lot of cars do this kind of racing and don't have regular rod bearing failures with stock engines, so I would like to believe it can be done without going with an accusump or anything like that.

I do intend to put in some cam regrinds to increase the power a bit, which isn't going to help the reliability at all.  I have no intention of raising the RPM range of the engine, as high RPM is a direct effect on engine durability.

Short answer: Newer engine with new bearings, maybe upgrade oil pans.

Photographer is finishing pictures from the event...

[CzechSilvia]

Whatabout an oil cooler, are you running one? I'd definitely run one in an endurance race car.

And since you have to put a new engine in there, you could diy the extended oil pan, the new engine would already be out of a car so it would be a lot easier. I don't think that would be too expensive and the vg33 would like that for sure.

As for the lsd, I have a Quaife torsen type diff in mine which I  love and I think it would be absolutely perfect for your application. It's a world of difference, I can put the power down a lot earlier coming out of a corner and my ca18et probably has half the torque of that v6 of yours, I think it would blow your mind what a difference can lsd make to your car on a track. Although it's hands down the most expensive aftermarket part on my s12, it was worth it, the car's a lot faster, I'd go for a torsen type lsd if I were you, it takes regular gear oil, you don't have to mess with any friction plates and setting it up, it just works and it's virtually indestructible which is probably a plus in endurance racing.

Also I don't know what shocks you have on the car but if you have some worn oem ones there, I'd be really careful with just slapping some stiffer springs on the car and calling it a day. The soft factory shocks seemed pretty useless to me to begin with and I don't think they could perform well or last long paired with stiffer springs

[Max]

Whatabout an oil cooler, are you running one? I'd definitely run one in an endurance race car.

And since you have to put a new engine in there, you could diy the extended oil pan, the new engine would already be out of a car so it would be a lot easier. I don't think that would be too expensive and the vg33 would like that for sure.

As for the lsd, I have a Quaife torsen type diff in mine which I  love and I think it would be absolutely perfect for your application. It's a world of difference, I can put the power down a lot earlier coming out of a corner and my ca18et probably has half the torque of that v6 of yours, I think it would blow your mind what a difference can lsd make to your car on a track. Although it's hands down the most expensive aftermarket part on my s12, it was worth it, the car's a lot faster, I'd go for a torsen type lsd if I were you, it takes regular gear oil, you don't have to mess with any friction plates and setting it up, it just works and it's virtually indestructible which is probably a plus in endurance racing.

Also I don't know what shocks you have on the car but if you have some worn oem ones there, I'd be really careful with just slapping some stiffer springs on the car and calling it a day. The soft factory shocks seemed pretty useless to me to begin with and I don't think they could perform well or last long paired with stiffer springs

Lots of good points here.

You're right about the oil cooler, that should definitely be on the list! I wish I had an oil temp gauge to see what kind of temps the oil reached. That would tell me if the oil temps were a contributor to the rod bearing failure. I do have a coolant temp gauge, and the coolant even with the stock radiator stayed right around 170 for the entire race. Larger oil capacity could help a lot with oil temp fluctuations as well. This engine does not have a very high oil capacity.  The truck oil pan has a bump out, and I might try and mimic that to add another quart or two of capacity with hinged trap doors.

You have a quaife, that's awesome! If money weren't an object, I would buy that diff too.  In my experience racing a miata, the torsen diff is everything I could ever ask for in a differential.  My boss who runs spec miata, has used clutch type diffs (mazda comp I believe) in endurance racing and they simply do not withstand the hours and hours of abuse.  He blew up two of them in one weekend endurance racing.  You're right, I think torsen is the best option for endurance racing.  There is another s12 team out here, believe it or not, with an LS2. They told me they use a OBX quaife knock off diff and absolutely love it, and have had no failures.  I would consider that too.  Yet another S12 team with a BMW engine swap use a weir spool (locked) diff. I'd prefer not to go full locked diff, but they are faster and about 80% as good as using an LSD.  If I can get my team on board to drive with a locked diff, I may go that route. I know there's bad, good and best options and there's a cost associated with each.  Right now I'm using "bad" and it's costing lap times.  I can tell you I will not be able to afford a quaife before the next race, but I will try to address this somehow.  You're right about putting the power down in corner exit.  Right now I have to coast through the first part of the chicane, and the other hairpin I have to bog through in 3rd gear or it will completely roast the inside tire.  I believe I'm loosing at least a second if not 2 per lap with the open diff.

Shocks are brand new GR2's.  I don't want to overload them, so I'm not going to go too crazy on spring rates.  I'll test it at a track day before the race weekend.  AGX's are an option, but again another cost.  We'll see if they hold up. 

I appreciate your input!