Jump to content
SAU Community

Recommended Posts

S13, but that shouldn't matter.

See video and not that in the long left hander at 0:41 and 1:43 how the nose of the car seems to want dart around a bit. All throughout the video you can see how skittish the car is. Last time I drove here it was much more progressive, I've added swaybars since then and I'm guessing the whole setup is too firm now.

And this is before the bars went in and starting from turn 1.

Here's what's in it/the alignment, let me know what you think. I did the alignment with a stringline, took 6hrs going up and down allowing the car to be settled again then re-measuring. I had no success with local shops.

So after A LOT of stuffing around it now has the following and "looks" a lot better.

Front - Camber/Toe (can't tell you what castor is, arms are stock). Considered maybe less camber might give me a better contact patch if the car is now not leaning over as much with the swaybars.
Driver: -2.75/1mm toe out
Pass: -2.75/1mm toe out

Rear- Camber/Toe
Driver: - 1.3/1mm toe in
Pass: -1.3/1mm toe in

Car has BC BR Coilovers with 8kg Front and 6kg rear springs - maybe these are too firm?

Whiteline 27mm front swaybar (adjustable and on max soft)

R32 GT-R rear swaybar (25mm hollow)
New end links both ends.

Federal RS-Rs 235 all round, was running about 29-30psi hot on that day. Maybe I'm just at the limit of what these tyres can do?

I'm yet to get under it and have a look at how the tyres wore, but the car was a late more skatey than usual, not sure if that's because the swaybars are allowing me to go faster or because something is wrong.

Yes I realise I am also a shit driver and smoother inputs will help :)

Did you use the same spring damper before and after ?

I would have thought before putting sways in the coilovers were taking alot of the load to stop body roll hence you having to run a harder setting on the coilovers?

Now you have decent sways the coilovers dont need to run double duty as such and take the anti roll job as much hence if using the damper rate as before your now too stiff....you should be able to soften the damper rate off to allow each part to do its job now

  • Like 1

I'm thinking a couple of things.

1) Like you and bcozican, I ponder if the overall suspension rate is too high. If your coilovers have very stiff springs and you have added stiff ARBs, then you will possibly have too much roll rate.

If you have wound the damping on the coilovers back to full soft (or even at the soft end) then it is very possible that you simply have too much spring (spring and ARB) rate for too little damping. As your very first order of business I would suggest that you look to winding the dampers up to half way, or perhaps stiffer and try again. The reason I say this is that if you are underdamped on stiff spring rates, then it will certainly skip around and be skittish. There isn't enough damping for the spring rate.

2) It is just possible that the ARBs that you have added have unbalanced your previous setup. Assuming it had good front-rear balance before, putting semi-random ARBs on top of that setup might have stiffened the front a lot more than it stiffened the rear. If that has happened, then it will want to understeer more. It certainly looked and sounded like it was understeering more in the long left hander. Admittedly, that will also happen if the damping isn't right, per my first thought above.

If your ARBs are adjustable, you could try softening the front one as much as you can. That will shift the grip balance forward a bit. Be aware though that if the real problem is unsufficient damping, then it could end up feeling better anyway, simply because you have backed off on the total roll rate at the front. Also be aware that if the problem is not in the balance, if it is instead simply too much spring rate for the damping, then softening the front without softening the back may well make the skippy behaviour worse at the rear.

^^ all that :yes:

also if all that is done and still a little unbalanced would it be a case of if you are now cornering harder and faster that front camber specifically (and may rear) might have to be increased a little bit also so that your not rolling over on the tyre? and increase turn in

Spoke to BC who suggested I speak with Paul at option1, he recommended returning to the stock front swaybar and testing that, leaving spring rates alone. Then swapping that around and putting the stock rear back in but leaving the front.

That's a fir bit of f**king around at a paid track day but it's not impossible.

I might take both bars, go and run a session with it as it is, and see how those times compare to previous Winton times then look to swap a bar out and test again.

Federal said my hot tyre pressures are fine.

Paul also said my alignment settings were on the money.

I put it on stands last night after packing up all my gear from the track day.

Interestingly the outside edge of the tyres front and rear looks darker/more worn.

Which I thought would imply it needs more camber.

Talking to a buddy of mine with a very similarly setup car (but better and wider tyres) he runs -3.5 front and -2.5 rear with the same bars and spring rates (although Tien RS and no BCs).

Two other things.

I'm being advised to get some adjustable castor arms and dial in more positive castor and was also asked to look at the angle of my LCAs, which are definitely not parallel upfront. Cross member side sits lower than wheel side which as I understand it is not good for Roll Centre,

Essentially, yes. It's about the arc that the arms swing through and the induced camber changes etc etc blah blah. If the arm is horizontal then the wheel is at the widest point of the circle/arc when at rest/zero position. Any disturbance up/down changes the relationship of the wheel to the road and the car less when set up this way than when the wheel is up above that diameter line. Know what I mean? Different suspension designs suffer to varying degrees. Skylines hate being too low. Silvias, with struts at the front, probably aren't as bad.

Then you start to get into more serious questions about where the roll centre is located. Perhaps you should google up the question and look at what happens when the roll centre is too low. There are some great books you can buy that will open your eyes a lot if you're interested enough. I recommend this one http://www.amazon.com/Race-Car-Vehicle-Dynamics-Experiments/dp/0768011272

If I raise it, I'm going to lose some neg camber also, so may also need camber bolts - but then strut clearance starts to become an issue.

A few people are jumping up and down about how I am still running stock caster arms also - which should give me more neg (dynamic) camber if I understand it correctly.

A few people are jumping up and down about how I am still running stock caster arms also - which should give me more neg (dynamic) camber if I understand it correctly.

Yes. Correct. And for a track car especially, the free dynamic camber you gain is worth a lot.

OK so raise the ride height, and get some castor arms.

I also have ties to the local BMW dealership who are happy to run over the car on their laser aligner for mates rates.

Any indication of what ride height should be in the rear? Front seems to be, get arms parallel, what about the rear?

OH I may also grab some camber bolts.

Edited by ActionDan

I wouldn't go more camber at the rear unless you want less drive traction. As to height, again the lower arms want to be close to parallel. If it was a Skyline you could look up the recommended eyebrow heights and use that as a guide. Silvias might be different measurement for the same actual height though.

If you lift the front, and the back then looks low......then lift the back too!

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • I'm looking for some real world experiences/feed back from anyone who has personally ran a EFR7670 with a 1.05 exhaust housing or a .83 I'm leaning towards the .83 because its a street car used mostly for spirited driving in the canyons roads. I"m not looking for big numbers on paper. I want a responsive powerband that will be very linear to 8000 rpm. I dont mind if power remains somewhat flat but dont want power to drop off on top. The turbo I've purchased is a 1.05, although the mounting flange T3 vs T4 and internal vs external waste gates are different on both housings, I not concern about swapping parts or making fabrication mods to get what I want. Based on some of the research I've done with chat gpt, the 1.05 housing seems to be the way to go with slightly more lag and future proofing for more mods but recommends .83 for best response/street car setup. AI doesn't have the same emotions as real people driving a GTR so I think you guys will be able to give me better feed back 😀   
    • Surely somebody has one in VIC. Have you asked at any shops?  Is this the yearly inspection or did you get a canary?
    • This is where I share pain with you, @Duncan. The move to change so many cooling system pieces to plastic is a killer! Plastic end tanks and a few plastic hose flanges on my car's fail after so little time.  Curious about the need for a bigger rad, is that just for long sessions in the summer or because the car generally needs more cooling?
    • So, that is it! It is a pretty expensive process with the ATF costing 50-100 per 5 litres, and a mechanic will probably charge plenty because they don't want to do it. Still, considering how dirty my fluid was at 120,000klm I think it would be worth doing more like every 80,000 to keep the trans happy, they are very expensive to replace. The job is not that hard if you have the specialist tools so you can save a bit of money and do it yourself!
    • OK, onto filling. So I don't really have any pics, but will describe the process as best I can. The USDM workshop manual also covers it from TM-285 onwards. First, make sure the drain plug (17mm) is snug. Not too tight yet because it is coming off again. Note it does have a copper washer that you could replace or anneal (heat up with a blow torch) to seal nicely. Remove the fill plug, which has an inhex (I think it was 6mm but didn't check). Then, screw in the fill fitting, making sure it has a suitable o-ring (mine came without but I think it is meant to be supplied). It is important that you only screw it in hand tight. I didn't get a good pic of it, but the fill plug leads to a tube about 70mm long inside the transmission. This sets the factory level for fluid in the trans (above the join line for the pan!) and will take about 3l to fill. You then need to connect your fluid pump to the fitting via a hose, and pump in whatever amount of fluid you removed (maybe 3 litres, in my case 7 litres). If you put in more than 3l, it will spill out when you remove the fitting, so do quickly and with a drain pan underneath. Once you have pumped in the required amount of clean ATF, you start the engine and run it for 3 minutes to let the fluid circulate. Don't run it longer and if possible check the fluid temp is under 40oC (Ecutek shows Auto Trans Fluid temp now, or you could use an infrared temp gun on the bottom of the pan). The manual stresses the bit about fluid temperature because it expands when hot an might result in an underfil. So from here, the factory manual says to do the "spill and fill" again, and I did. That is, put an oil pan under the drain plug and undo it with a 17mm spanner, then watch your expensive fluid fall back out again, you should get about 3 litres.  Then, put the drain plug back in, pump 3 litres back in through the fill plug with the fitting and pump, disconnect the fill fitting and replace the fill plug, start the car and run for another 3 minutes (making sure the temp is still under 40oC). The manual then asks for a 3rd "spill and fill" just like above. I also did that and so had put 13l in by now.  This time they want you to keep the engine running and run the transmission through R and D (I hope the wheels are still off the ground!) for a while, and allow the trans temp to get to 40oC, then engine off. Finally, back under the car and undo the fill plug to let the overfill drain out; it will stop running when fluid is at the top of the levelling tube. According to the factory, that is job done! Post that, I reconnected the fill fitting and pumped in an extra 0.5l. AMS says 1.5l overfill is safe, but I started with less to see how it goes, I will add another 1.0 litres later if I'm still not happy with the hot shifts.
×
×
  • Create New...