What to do for a race car?

[Lockleaf]

Sweet. Nice work man. Looking forward to the pics.

[hobbes_the_cat]

What about an r200 diff? 280zx's came with em. Should fit the same as an r180 since the Zx came with both? I know the r200 could be had with a 3.90 cause I have one...

[HRH]

R200 is quite a bit bigger, not a direct drop in.  The R180 project has proven successful!  Or at least ready to go back together and be tested.  I have a video uploading to youtube now.  I'll post the link after dinner if it's done uploading.

[HRH]

[HRH]

Well, I have the diff in the car, all buttoned up, ready to put fluid in and install the driveshaft.  I'm all happy, thinking I'm just Mr. Badass, and suddenly the driveshaft won't mate up with the input shaft flange off the diff.  WTF?  I measured the holes, they were the same.  Yeah, as you might have already guessed, the prop shaft on a 720 4x4 is pretty dinky to clear all the stuff up front.  They forgot to machine out about a 1/4" of material.  So, the centering ring on my tiny Maxima driveshaft is too large!  ;)

 

F a duck.  So I yanked the flange off the old Maxima diff tonight, and I'll get to do that under the car tomorrow since I cinched everything up.  I'll consult the FSM, but the good thing is I think it uses preset washers instead of a crush sleeve like American diffs.  Meaning I can take it off and put the other flange back on and tighten her down without worrying about resetting the pinion.  The other option is the count the turns method, which I've done successfully before, but still.

 

Anyway, she's almost ready to go test drive, just a little snafu.  Remember to look at the FRONT of the input flange when swapping diffs to avoid this annoyance.

[paradime]

Had a similar hang up with my 06, sti r180. I had my drive shaft shortened, but didn't think I would need to dick with the flange on the diff. when I went to install it, I couldn't even get the flange through the X-member it was so big. Fortunately Troy Ermish was able to sort that one out for me. Not the only time I found myself in over my head on that build. Thank god for the pros. 

[Duke]

I'll drop my .02 in here.  I don't know how competitive the club you run with is, but setting FTD at pretty much any autocross takes some doing, from the car and from the driver.

 

First, go to R compound tires.  Don't expect that magical 2 second difference right away though.  It takes a while to get used to the extra grip, and to get the car set up to use that extra grip.  Don't try and cheap out and buy take offs or semi slick tires.  If you are really serious, go with Hoosier A7's.  If you don't want to spend that much I have been really happy with the Hankook Z214 C71's, they last a while and only give up about a second to the Hoosiers over a minute long course.

 

Spend some money and time really setting up the suspension.  Corner weighting, optimizing camber and tire pressures are very important.  Also good shocks (I'm not talking about KYB's or Tokico's) are worth the investment.

 

A LSD does make a huge difference as well.  It really enables you to steer the car with the throttle through long corners and helps immensely putting the power down coming out of sharp corners.  When I put the LSD in my car it completely changed the car, all for the better.

 

I'm really just scratching the surface here, there are countless more things that go into making a fast autocross car into a FTD car.

[paradime]

Totally agree with duke on the Hankooks and the investment in an LSD. If your goal is to shave those last few seconds, this is money well spent. Once you start searching for more power, it would be a waste if your diff can't put it to the ground. Unlike a set of R compound tires though, once you have that LSD, it's money in the bank, because it will always be worth what you paid for it. 

[HRH]

Yeah, I may not be able to get FTD with the current setup as my Datsun guru predicted, but we'll at least get as close as possible on my crappy budget. ;)  It's fing cold here this morning!!!  7:47 and it's 38 degrees!!!  Brrrrr!!

[HRH]

Flange swapped, diff filled with 85-140 for poor man's limited slip, lol.  Ran it on stands, everything looks ok.  Going to have a cup of tea and go test!

[HRH]

 

Now for dealing with wheel hop issues and transmission shifting issues!  Oh joy!  But she does accelerate better!  I definitely need some higher spring rates in the front.  Notice when I stop from the top of third, you can hear a little squeal from the tires?  That wasn't the front.  That was the rear from weight transfer.

[HRH]

Ugly Betty is definitely more fun!  Still dicking around with different varieties of transmission fluid to try and get clean shifting at 7200 rpm.  10w40 worked pretty well, 5w30 worked less better.  Just put 15w50 synthetic in, we'll give that a shot.  Also stopped by my Datsun guru's shop and corner weighted her.  She's actually remarkably balanced side to side.  Front to rear isn't horrible, just not the best.  58% front weight, 42% rear.  I've seen worse.  Hell, the 370z is 56% front.  Anyway, with a half tank of fuel she weighed 2385 without me in it.  Not too bad.

 

The front suspension is good enough, the rear needs some major firming up.  I'll be making solid mount bushings for three points in the rear, which should solve the wheel hop issue, while bringing more noise to the cabin, but hey, she's already loud now, so who cares right?

 

Oh, and icing on the cake, passed a Prius on the way home. :D

[Lockleaf]

Try synchromesh trans fluid. DatzenMike gave it rave reviews. Cleaned up all his shifts. It's also totally yellow metal safe. I'm planning to try it on my next trans fill.

[HRH]

Really?  Interesting.  It's a more ATF based fluid, which is fine.  But how often does Datzenmike shift at 7200 rpm? :D

[Lockleaf]

Ask him :)

[HRH]

Well Mike? :D

[datzenmike]

 

Now for dealing with wheel hop issues and transmission shifting issues!  Oh joy!  But she does accelerate better!  I definitely need some higher spring rates in the front.  Notice when I stop from the top of third, you can hear a little squeal from the tires?  That wasn't the front.  That was the rear from weight transfer.

 

It's also known as trailing throttle steer. Let off the gas or hit brakes, front dives and back lifts and you get positive camber and toe in on an IRS car. 

 

I never shift that high. The GM stuff 'fixed' downshifts into 2nd and 1st and also 3rd and 5th up shifts. By 'fixed' I mean less effort. I hardly ever used to down shift because it's a hard pull of the shifter into 2nd and even harder push forward into first with the 80w90 molasses I was using. Now much smoother and less effort down or up shifting. Almost no difference between cold and warm transmission now.

 

Quite the additional acceleration for the dollar spent isn't it Matt? (well if it had bolted up on the first try) I had 3.70 and went to 4.11 so 11%!!!! On my 5 speed this pretty much makes 5th over drive the same as what 4th was. At highway speed you seldom have to down shift now it just PULLS!!!!! I friggin' love it. 

[mattyhacks71]

E7 Corolla sedan. Stripped interior they weigh like 1800lbs. AE86 suspension and brakes, dual carbs, header...would be so cheap Pretty sweet cars too I had a wagon

[HRH]

Very cool, except it's Toyota, you know I just can't drive it. ;)  And yeah Mike, made a big difference.  Quite nice.  Wish I could have gotten an LSD, but oh well, too expensive for now.  Maybe over the winter I'll find a good deal on one.

[q-tip]

Should have kept the 510....

[mattyhacks71]

Nothing wrong with Toyota (older ones that is) or those cars. They have similar attributes to early Nissan/Datsun, same kind of swagger, and the E7 was what the HL510 should have been. I had an 81 Corolla wagon, great car to work on a drive!

[505plus5]

Nothing wrong with Toyota (older ones that is) or those cars. They have similar attributes to early Nissan/Datsun, same kind of swagger, and the E7 was what the HL510 should have been. I had an 81 Corolla wagon, great car to work on a drive!

My dad bought one also and we used it as the family wagon. I still remember how well build it was and how strong it sounded. Easy to work with. It was probably around the same time we had our first Datsun in the family, as well!

 

Wagons just rock! 510's especially.

 

But if u don't have one yet, a LADA will do! Hahahahah ;-D

[paradime]

I don't think HRH's aversion to Toyota is a practicality thing. It's a F**K Toyota thing.

 

HRH,

With regard to tapping the IRS for all it's worth, a valuable trick Troy Ermish gave me is to brake early before the corner, and accelerate early out of corners. As Mike mentioned about "trail throttle steer", this can also be used to you advantage. You know how the rear squats when you accelerate? When cornering, if you transfer weight to the outside, and load up the rear suspension under power, the toe out literally turns the car from the rear as well as the front wheels. Granted, the stiffer the rear the better, but you still need some suspension, so you can't eliminate it totally. Trail through is not the best geometry, but do it right, and you can make it work in your favor.

[paradime]

This brings up a question, have you corrected the roll center change after lowering the car, aka slotting, or adjustable brackets? If not, your in for a huge surprise once you correct.

 

Here's a fantastic thread on this engineering forum that really goes into the geometry issues involved with changing the "normal vector" static position of the suspension.

 

http://www.eng-tips.com/viewthread.cfm?qid=353732

[HRH]

The rear suspension is about where I want it actually, but no, I haven't slotted.  I roughly remember the alignment specs, but it's been so long ago, I've forgotten.  Plus, I still need to make the three mounts in the rear solid, which will solve oodles of problems.  Been reading up on that.

 

The 15w50 synthetic transmission oil did better shifting in cold, but about the same or a little worse for grindage on quick shifting.  Pretty much I'm going to either accept a little grinding in gear if I'm hammering on it at autocross, or I'll have the transmission rebuilt with new synchros and see if that doesn't help.  At the moment though, it's pretty good.  I might go back to the 10w40 I was running in it.  I've found I can shift at 6000 rpm and not have it grind, but any higher I get a little grind.  If I shift easily, it won't grind, but that means wasting a third of a second extra during shifts.  The good part is at least now even if I shift early, it still doesn't take nearly as long to get going again.