Keeping 300Kw On The Ground

[GTScotT]

Morning all,

Whilst I'm not currently a skyboat captain I am a diahard SAUer and am looking for some direction re my wannabe F14 fighter jet (read; S14 that struggles to stay on the ground).

I've recently finished my motor setup and have had it tuned, which resulted in 295rwkw on a DD roller.. Its definitely motoring along when set to 'loud'. For reference its the usual SR business with a GTX3071R.

The problem I'm having is that the car seems to want to catch air with the smallest bump in the road, and generally wants to break loose a lot. Let me be clear though, the car has a lot of cornering traction (I fall out of the seat before it understeers) and it has a lot of straight line traction for putting power down. Its when I want to use BOTH that things get silly, AND the obvious issue of taking flight on bumps.

Now I know everyones going to say that its normal for the amount of power etc. but I really do want to hear some feedback on what others have done to make their cars more manageable. What changes and mods have been performed that will make the car more 'seated' on the road and generally able to belt a little harder through the twisties.

The existing chassis setup as follows:

Tein superstreets 6/6kg (quite smooth and comfortable, generally absorb bumps well)

Castor rods

Rear camber arms

Rear toe arms

(full camber and toe adjustment)

The alignment as follows:

0 toe front

2mm toe in per side rear

2 degree camber front

1.2 degree camber rear

So, what sort of things will help keep this thing better grounded? Heavier spring rates? Fatter sway bars? A different alignment? And what will be the side effects if any?

I want to drive the car in a little more anger, which was easily achieved @ 240kw. Please give some suggestions on what could aid this.

Cheers!

[GH05T]

what wheel size and tires are you using?

[PN-Mad]

Toe settings are wrong.

Get them reset.

-3.00 total toe on the front

+2.5 total toe on the rear.

Camber is fine. Wind off the rear damper.

[GTScotT]

what wheel size and tires are you using?

17x8 +15 front 215/45 Potenza RE002

17x9 +28 rear 235/45 Potenza RE002

Offsets are being achieved with spacers to give the car 20mm more track than standard with 20mm wider front track than rear (factory ratio front to rear).

As noted the cars got a lot of traction in most ways, but its less than stable when you want to try use that traction to its fullest. I really want to push it out of corners but its possibly squatting and picking up the front too much when I do.. Which I believe would also be why when on power it tends to want to catch air (squatts a lot and picks the front up).

Toe settings are wrong.

Get them reset.

-3.00 total toe on the front

+2.5 total toe on the rear.

Camber is fine. Wind off the rear damper.

Cheers man. Can you confirm if these are MM or degrees?

I need to re centre my steering wheel as I went to a quick release so will get these done when I do.

[Scott Black]

Can't do shit to fix it, give up and get a skyline instead of a drifter

[PN-Mad]

Lol.

MM.

[GTScotT]

Can't do shit to fix it, give up and get a skyline instead of a drifter

lol you first

[GH05T]

GTR

[GTSBoy]

It's too stiff in the rear. 6kg at the front would probably be nicer with 5 at the rear, possibly even 4. If you like the handling balance that having that much rear roll resitance is giving, then replace it with stiffer rear ARB (adjustable of course).

[Scott Black]

lol you first

Halfway there I have the running gear and most of the front end

[GH05T]

It's too stiff in the rear. 6kg at the front would probably be nicer with 5 at the rear, possibly even 4. If you like the handling balance that having that much rear roll resitance is giving, then replace it with stiffer rear ARB (adjustable of course).

actually thats a good point, whats skipping, the front or the rear?

[GTScotT]

It's too stiff in the rear. 6kg at the front would probably be nicer with 5 at the rear, possibly even 4. If you like the handling balance that having that much rear roll resitance is giving, then replace it with stiffer rear ARB (adjustable of course).

Are you sure about this? I'm aware that dropping the rear rates is going to make it have more traction as it will be able to squat more, but how will it also help out of corners?

Once this issue is sorted im fairly sure that I will need a bit more resistance all round to compensate for the increased corner speed. Maybe new sways front and rear will make the car feel firmer on the road? And perhaps an increase in front spring rate will give the effect you are describing? Or do you feel the softer rear will definitely be better?

Halfway there I have the running gear and most of the front end

lol I expected this for an answer.

[GTSBoy]

Well, spring rate balance is important - actually wheel rate balance, which is the sum of all spring components (actual springs and ARBs) multiplied by their respective lever arm lengths. The rear suspension for S14s is the same as Skyline, so what's true at that end of a Skyline is true of an S14 also. The fronts will be a bit different because the suspension geometry is different between struts and double arms. But nevertheless, and despite the lighter engine at the front of the S14, I would say that having the same spring rates front and rear is going to give you too much rear roll stiffness. That's a separate issue to traction. 6kg rear springs are pretty stiff for the street. I have ~5kg at the front of my R32 and ~4 at the rear and I have traction problems with that. The rates are high enough to limit weight transfer. When you consider that stock spring rates are ~3kg/mm you can see that a 100% increase might limit the abilities to hook up.

High spring rates are required to limit body roll and absorb high frequency loads when running at high speeds (on the track, or on reasonably decent roads). Stiff springs do not work well at low road speeds especially where the roads are a bit rough. Even a sizable bump, when taken at low speed, represents a lower frequency input than stiff springs are "tuned" for. You really cannot have it both ways. Any car that reviewers claim handles massively well (so, BMW M cars, etc) won't have really high wheel rates. They will have sensible rates and top shelf damping (and top shelf geometry design, etc etc).

With respect to how it will "help it out of corners" if you softened the rear - all of what I said above applies. Reduced roll stiffness increases weight transfer onto the outer wheel which helps with drive. Reduced total stiffness increases weight transfer towards the rear regardless of whether you are going straight or accelerating out of a bend. Adding stiffness to the front helps with the balance between front and rear, but does nothing to improve the weigh transfer to the rear - it would actually make it worse.

[gtr jet]

Wider tyres?

[GTScotT]

GTSBoy:

Sorry to throw a spanner in the works, I was SURE they were F6R6 but have just looked online and found that Tein list them as F6R4... That would probably explain why the car has a lot of rear end traction for what it is. Sorry for killing your time on explaining the suggestion, my error.

Now comes the part I hate.

I've analysed your response a few times and have noted a few key points surrounding frequencies and variation between high and low speed driving, and am getting the impression you are basing advice on the fundamentals of regular street driving. The reason why this is the part I hate is because I don't like being that guy talking about how fully sick they drive, so don't get me wrong here. I'll explain more.

For regular driving most people think the car is close to stock. Its solid, firm, well behaved, absorbs bumps well etc.though the car feels incredibly light on power, and the lift I'm describing is when I'm trying to use upward of 70% throttle. In the last couple of weeks I have been fiddling with boost control and the car has come off the ground twice when fully loaded in 3rd. Not exactly what I would consider low speed nor low frequency. I am actually trying to resolve the opposite of this, where I'm going fast and the wheel cops a reasonably hit from the road.

The whole exit speed thing does make sense in what you were saying before, but after checking advertised rates I am a little confused again. I guess the trick may be in ARBs but I am not sure at the moment. Originally I was leaning heavily to a stiffer setup with larger diameter monotube shocks. Now not sure what to do or think, wishing I could just work it out for myself..

[GTSBoy]

OK. That's a reasonably large spanner to put into the works.

Rear subframe and diff bushes are a place you could look to. If the subframe is moving under big power loads (ie squishing the bushes up all in one direction or torquing the subframe relative to the car, then you hit a bump, maybe the sudden release of torque is causing a reaction back through the suspension arms and breaking traction + possibly having a vertical component making it feel like the car is jumping. It's pretty much a sudden axle tramp sort of thing.

No HICAS on this thing, yeah? What condition are the toe control rod ends in?

What diff?

I would try some pineapples first perhaps, see if it behaves better (or at least different). You could also try unhooking the rear ARB to see if changing the way load is transferred from one side of the car to the other has an effect on this behaviour. Beware, the car will probably be an understeery pig set up like this. Use caution!

[GTScotT]

Damn I didn't even think to mention subframe positioning, I keep assuming those mods are the norm.

I've got pineapples in place which are locking the subframe at maximum height. The diff is a helical from an S15 with a 4.3 ratio, hook up from this is good. Always predictable, pulls the nose in rather pushes the arse out.

Non HICAS in the S14. Adjustable toe rods are rose jointed and near new, as are the camber and castor.

Haha no rear ARB, that would possibly be quite scary. I really want to be able to get the gas on earlier with a bit more confidence, grrr.

[HR32GTS 4DOOR]

You have in the first post that you have rear camber and toe arms, but no traction arms. How much have you lengthened the camber arm relative to stock?. If you lengthen the camber arm and not the traction arm you end up with a large change to the toe curve during the suspension travel, ie. Bump steer. The wheel will toe out under compression if the camber arm is lengthened and the traction arm is not. So when you hit a bump at speed, wheel goes up, toes out and it breaks loose.

So either put the standard camber and toe arms back in and live with the hektik rear camber (assuming the car is low).

Or

By some traction arms, make a bump steer gauge and set it up properly.

[LTHLRB]

to keep 300kw on the ground without melting your tyres is to use softer compound 255 wide tyres or semi slicks. Minimal amounts of camber because you want the full face of the tyre on the road and softer damper settings as you want the ass end to squat and put weight onto the rear tyres. Anything less with a 300kw responsive setup you'll be the frymaster of the streets

[Cxxo]

I find that my 32 was terrible around the mountain, it was bouncy and soft and all over the shop, unstable and really didn't let me push it. now it was no weapon in the power department. 260rwhp.

I found that with my coilovers they were to soft for me. I had 8 fronts 6 rears. I bought 10kg springs and put the 8s on the rear. If feels SO much nicer to drive just around the streets and with it slightly stiffer (less of a bouncy role) Was like shock rebound was to high and springs to soft. less body role from the springs as well around corners. I find soft suspension is for straight line squat and grip. but soon as you hit a corner its to sloppy and feels like its floating around to much.

That's my personal experience anyway.