Time Attack Setup For A Gtr

[Full-Race Geoff]

Hello resident SAU experts, I have decided to turn my GTR-based S14 into a time-attack machine for a big race event coming up (modified tuner shootout). it will go back to occasional street car duty afterwards (laws are loose where i live), but first and foremost I am working hard to make the car competitive for the event. We got 2nd place the last 2 years in heavily modified street subarus and we dont want to give that up. A street subaru wont get us 2nd this year - there will be a dedicated track porsche 911 twin turbo awd as well as the sierra sierra cosworth evo and tarzan is driving crawford's STI so we have to be on top of our game to do well. I own full-race and have a team of expert welders/fabricators so we can build almost anything. We have 10 weeks before the event. The chassis and engine are VERY solid and have plenty of time with no problems. Our driver is an ace and knows this track extraordinarily well.

Specs are:

full roll cage, proper bracing in the right spots

r34 gtr brembos front and rear, pfc 01 pads, brake ducting

R32GTR front suspension, caster changed to 7degrees through custom upper control arm mounts. Stock swaybar, Stock Upper Arms, Stock lower arms, Stock tierods, Quaife Front LSD, urethane swaybar bushings

R33GTR rear suspension, full adjustable links, R32GTR stock swaybar, nismo LSD

Tires are Hoosier A6 (Autocross compound for time attack) and BFG R1 (enduro + lapping) 275/35 on a 18x10.5

Torque Split is running fixed with 40-55-60psi in the transfer case (ATTESSA eliminated) depending on preference and tires/track condition

its a built motor, single twinscroll turbo, 680hp on E85 (helps response), good oiling system and cooling is getting improved right now

I am getting a set of triple adjustable motons, and they will be used only for the track (will switch out to my koni 28 series for the street). Curious on what you guys have used with regards to spring rates on a full aero equipped gtr at track weight (~3000lbs dry)

Please advise on roll center adjuster height, tie rod changes, spring rates, alignment and anything else pertinent. We are taking care of aero and improving the cooling right now, will jump on susp middle of next week, waiting on the motons and will need to make some decisions soon.

here are some pics of the engine setup 2 months ago while i was daily driving it (engine/turbo will remain unchanged) and the twinscroll borg warner S300SX 88-75 turbo, with 90 degree compressor housing.

-- crappy dyno of pump gas at 19psi. e85 tune will be at 30 psi and will destroy this

some pics of the changes im making now:

^^new vmount, optimized radiator airflow

^^modified R32 GTR spindles to accept the 1/2" heims on the motons AND dropped the toe link 30mm to adjust for bumpsteer. will finish machining this weekend

^^surge tank with dual 044s, to run 100psi base fuel pressure on E85

PLEASE ADVISE:

-roll center modifications to the front/rear?

-bumpsteer mods for the front end?

-spring rate ranges for slicks and full aero package

thanks for reading, i hope to represent the RB26s well!

Edited February 5, 2010 by Full-Race Geoff

[Travis Trayhern]

hang on you got the gtr 4wd system in there............. dam thats kool

[R31Nismoid]

100psi base fuel pressure... jesus!

[evil_weevil]

All I can say is :drool:

[DJRIFT]

i dont know much as im no expert but i am surprised reading this that you have used r32 GTR front suspension (guess saying it come with the engine EG half cut) as the later stuff (r33 34) is far better in the actual geometry.

The R32 stuff also has a very narrow range for optimum suspension travel. if you lower it much over stock it throws the geometry out. So if you want it low and sleak with the ground the pick up points if possible need to be changed to.

At the end of the day if you map the suspension travel as in bump steer and camber you will be able to see where changes need to be made.

Oh and thats a top job and the car looks very clean in the battle ship grey.

Edited February 6, 2010 by DJRIFT

[Full-Race Geoff]

thanks for all the compliments guys, glad you like the build.

r32GTR must be used in the front susp because of space constraints of the s14 chassis... r33/r34 upper control arms simply will not fit. Im not sure where you got your info djrift becuase the only real difference from r32 to r33 is that the upper control arm on the r33 is a true wishbone, whereas the R32 is a single link. otherwise the subframes are identical, LCAs are identical, ball joints are identical... just different upper arm (camber curve) and the fact that i can put my casterat 7 degrees while an r33/r34 cant move their is a big advantage to me. I have cycled my susp and do have a small amount of toe change (bumpsteer) and i dont want to make any changes until i figure out what to do with the roll center spacers between the ball joint and knuckle... doesnt make any sense to fix the bumpsteer and then have to change it again for the rollcenter spacers.

anyone on here experimenting with the roll center adjusters?

[JAGR33]

Nice car, love the 4wd modification in the s14 chassis, will surely surprise everyone on the track.

Can clarify that 32 LCA's are definetly different to the 33/34 setup. They are definetly shorter.

Check the Nismo catalogue, thay have different part numbers aswell.

I know because I bought a second hand set, and was told by the seller they came of an R33. Went to put them on and they were shorter than my standard LCA's.

Good luck with it all....

[Full-Race Geoff]

Nice car, love the 4wd modification in the s14 chassis, will surely surprise everyone on the track.

Can clarify that 32 LCA's are definetly different to the 33/34 setup. They are definetly shorter.

Check the Nismo catalogue, thay have different part numbers aswell.

I know because I bought a second hand set, and was told by the seller they came of an R33. Went to put them on and they were shorter than my standard LCA's.

Good luck with it all....

oh wow thanks for that bit of info! i have many clips, r32 and r33, will have to go measure them and use the longest to get the most negative camber.

to clarify - do you have any idea how much shorter the 32GTR LCA is than 33GTR?

[Duncan]

very interesting project....more pics and details would be interesting considering the work that must hasve gone into it.

I don't see how much information on roll centres can help when it is such a different chasis....but here goes.

In our 32 gtr (and in other 32gtr/z32s being raced is aus), the rear roll centres are easy to work with. We simply modified the subframe to have higher mounts for the upper control arms (3 points, each about 2cm apart), same with the lower rear mount. the lower front mount on the r32 was not great, and nissan adjusted in on r33/r34 by changing the angle/moving it up. we made the same change to the rear subframe. then removed hicas and used rose jointed links to the hub instead. also we solid mounted the subframe to the floor which lowered the car another 15mm (the 32 gtr bush sticks up a fair way and there is a large washer)

the front is much harder. we have been racing a 32 gtr production car for years and the main lesson has been that the front geometery witht he factory arms is shit house. we are lucky if adjustable upper arm bushes last half a season, and the max castor we can get is 4.50 without rubbing on stuff (i guess the s14 chassis is different). basically the castor just pulls the upper arm at an angle and it is only designed to move in 1 plane.

as for suggestions at the front.....contact John at Unique Autosports here in sydney. He has done a heap of work on the upper arms and has come up with a good design to deal with the castor challenges. Also he has 20mm ball joint spacers which we are running to help lower the front roll centre (not as good as the rear unless you also move the upper arm points as you affect the geometry). Fulcrum suspension here in sydney also offer 15mm longer bll joints as another option. Obviously all bump steer will require measurement and adjustment after.

Having said all that - given the amount of work you have done I'm surprised you did not do a custom double wishbone suspension at the front, that is what the most serious cars have done here. I think you should consider the idea before stuffing too much with the standard r32 setup.

[DJRIFT]

I thought i was on the right track

every one ive ever spoke about the front suspension of a r32 has said its crap. with the r33 one being better.

I had also been told not to go changing the front roll centre with just the 20mm ball joints as what you do to the bottom you must do to the top and after studying my own set up these is f all you can do at the top without major changes. if your going to make major changes to fit the r32 stuff than you may as well fit somthing better again.

the Drift guys on Nissansilvia.com.au have been talking about it alot. http://www.nissansilvia.com.au/forums/inde...howtopic=412505 Most of its rubbish posts but some interesting stuff non the less. they run the McFurson strut thoe so they are talking about irrelevant stuff for the front end but the rear has some good ideas to

[Full-Race Geoff]

the front is much harder. we have been racing a 32 gtr production car for years and the main lesson has been that the front geometery witht he factory arms is shit house. we are lucky if adjustable upper arm bushes last half a season, and the max castor we can get is 4.50 without rubbing on stuff (i guess the s14 chassis is different). basically the castor just pulls the upper arm at an angle and it is only designed to move in 1 plane.

as for suggestions at the front.....contact John at Unique Autosports here in sydney. He has done a heap of work on the upper arms and has come up with a good design to deal with the castor challenges. Also he has 20mm ball joint spacers which we are running to help lower the front roll centre (not as good as the rear unless you also move the upper arm points as you affect the geometry). Fulcrum suspension here in sydney also offer 15mm longer bll joints as another option. Obviously all bump steer will require measurement and adjustment after.

Having said all that - given the amount of work you have done I'm surprised you did not do a custom double wishbone suspension at the front, that is what the most serious cars have done here. I think you should consider the idea before stuffing too much with the standard r32 setup.

that was a huge help, I am with you 100% on the rear. The front is where i am trying to find what setups people like. here are some pics of my setup, you will see why R32GTR is just perfect for this cars strut tower spacing (keep in mind this pic shows 7 degrees positive caster, and it works very well - no worn bushes):

This is a kit we are wrapping up development on for enthusiasts to do the swap themselves, all they need is a good MIG welder. I am only interested in tuning this setup to the best of its abilities, not interested in starting from scratch with a fabricated double wishbone setup.

As far as i know, the midori seibi R34GTR is one of the fastest GTRs in japan, and Ive got some pics of that car where you can see what the do differently:

^^in this picture you can see they mount the tension rod *under* the front LCA + they use a tall spacer on the tierod from the knuckle

^^in this picture you can clearly see there is no balljoint spacer (aka roll center adjuster) between the ball joint and front spindle. Also it appears to be a stock height ball joint.

^^this pic shows the rear susp and you can see where they beefed up the toe link, added a tube for support between the RUCA and Traction rod mounts on the subframe, and by looking at the exposed threads on the subframe mount, it is clear that the subframe has been moved up as far as is possible

Id love to get input from John at Unique -- does he post on this forum?

32 LCA's are definetly different to the 33/34 setup. They are definetly shorter. Check the Nismo catalogue, thay have different part numbers aswell.

thanks again for that last post, I checked my car and the parts i have here, i had (10) 05U arms (i assume that is R32 GTR) and only (4) of the 3N GTR - i assume that this is R33? Ive always had the 3N GTR arms on my car so i assume that may be why i always was happy with my camber curve, with the stock UCAs. pics:

---------------------------------------

here are some more pics to keep the thread alive

^^^my kind of RUCA, plenty of strut clearance, easy to get replacement heims for, and it cost $50 in parts

^^how the heim will sit inside of the welded spindle I posted last time

^^^welded the fender braces to the sheet metal, these can make a difference if the cage doesnt pierce the firewall - but only if they are welded in.

^^its a huge hassle to jack a 240 with big sideskirts + i needed some stiff mounts for the bellypan aero - so we made these jackpoints/bellypan mounts

^^^sealed up the area from frame rail to skirts, and put a little dynamat in there to keep things quiet. will finish the center and f/r in 2 weekends.

more random pics:

[Beer Baron]

your front upper control arms are definitely still 32 GTR. 33 and 34 GTR front upper control arms look very different. instead of a dog bone shape they are more of a U shape and their two arms of the U mount on the outside of a upper hub mount instead of inside like the 32 ones do.

33 upper control arms (they are aftermarket but you get the idea).

the rears are in this pic on the right. where as 32 rear upper control arms encircle the shock and spring so they are sort of an O shape with a single mount point to the upright and to the car.

these are 32 rear upper control arms.

car looks awesome btw. I imagine it's pretty quick.

[Giveway]

Insane car. Tidy work.

[Equinox]

Hey Duncan do you have any pics of the modifications you did to your subframe's pickup points?

I've run out of room to raise my subframe any further and need to look into other ways.

[Equinox]

Nevermind found the pics.

[Full-Race Geoff]

Nevermind found the pics.

PLEASE POST!!! i dropped my subframe and stripped it down today, getting ready to weld tomorrow. would really help me to see pics now (and save me a bit of time)

[hpt_simon]

interesting post

im ding my rear and front subframes too right now.

would anyone be so kind to right down some supension geometry changes

i saw a post long time ago about unique autosports doing something similar to their z32 but i cant seem to find the build thread.

keep pics coming

simon

[Duncan]

very interesting project....more pics!

it wasn't exactly a bolt in for the upper arms by the look of it, did you have to cut out the clearance for the upper arm? got pics from the other side?

I guess if you can locate the upper arm anywhere you can actually fix most of the issues we have with the stock location:

can't lower it/move roll centre

can't run too much castor due to flogging out upper arm bushes.

I am literally lucky to get 1/2 a season out of the upper arms before they flog out, and that is without roll centre adjustment.

my build thread is here but it talks only about the rear...we have not finished the front and are going to go a pretty custom direction (with ae86 lower arms of all things). Also it's never turned a wheel so take it all with a grain of salt. http://www.skylinesaustralia.com/forums/Ma...ld-t221982.html

[Full-Race Geoff]

it wasn't exactly a bolt in for the upper arms by the look of it, did you have to cut out the clearance for the upper arm? got pics from the other side? I guess if you can locate the upper arm anywhere you can actually fix most of the issues we have with the stock location:

actually there was zero cutting required for the upper arm in the S14 chassis, that is the point of our conversion. There is welding, but no cutting. I will post some more pics during the next round of work.

i am just about finished with my rear subframe, very very happy with the end result. Got some bushings to press and a cpl welds left, you guys are going to like it my new stainless fuel filter came in so i can finish the fuel lines and now i really ned to start working on mounting my NASCAR front splitter and the ic/rad/bumper, making all of them quick release

Edited February 15, 2010 by Full-Race Geoff

[Full-Race Geoff]

still needs 2 more tubes and some sphericals for the uprights, should go back in 2 days from now