Removing HICAS?

[Ender]

If you were gonna drag would you load up wityh some extra weight in the back seat or boot? I generally see people unloading weight....I am genuinely interested as to why you are of the opinion hicas would make any noticeable difference to takeoff...

Cheers,

Russ

[Steve]

Ender, this is true, but speak to rev210 - he got some great times with 100kg of balast in the boot. On a dyno sometimes they put people in the boot. A serious drag car will try and loose as much weight as possible.

Try taking your car for a thrash with a full tank of petrol, 1/2 a tank and almost empty. I definatley notice a traction difference. In second with a near empty tank, from 30kph with 1/2 throttle and in a straight line my car goes sideways - doesnt happen with a full tank of petrol.

Remeber skylines dont have alot of weight on the back wheels for a drag car, which is why squat is so important on RWD for the drags, transfers to the back wheels.

[Ender]

People in the boot on a dyno is a bit different.....I understand squat is important for takeoff....hicas does not make your car squat....weight does (not an extra 15-20kgs) and weight transfer does...and rear suspension settings do and geometry of rear suspension does....having a lock bar as opposed to a hicas rack does not change the static geometry therefore how can it induce squat....(apart fromt he slight increase the 15kgs has...or is this the only advantage r31nismoid was proposing?).

1 tankof petrol is 50kgs not 15-20kgs so yes...i agree you would feel it...

I wonder where the point where weight for traction becomes a liability for acceleration after traction is not an issue....ie obviously 200kg in the boot would give an improvement in grip on take off...but at half track you are lugging an extra 200kg which slows you down at this point....

whereas if you had least weight possible you would have less grip on takeoff but at half track you would accelerate faster due to less weight.....

I wonder if anyone has done a graph or similar to find the optimum points for a skyline??

[Ender]

oh and the reason I say 15kg's or so is cause thats how much it all added up to when I pulled the hicas plus lines from my car...and it is not all from the rear....Just to clarify...it is not 40kg's as was mentioned earlier in this thread...

Cheers,

Russ

[Sydneykid]

Hi guys the way the HICAS works is like 2 pistons facing each other. Each piston is connected to one rear wheel via the usual tie rod (like on the front). The hydraulic pump can supply oil to one side of both pistons or the middle of the pistons. This means the pump can make the rear wheels toe in, toe out or steer together to the left or right. The HICAS ECU decides which solenoid valve opens and where the oil flows.

This system, in principle, is the same for R32 and R33. In the R32 the power steering pump at the front (driven by the engine) has two stages, one for the front wheels and one for the rear wheels. On R33's the engine driven pump only works on the front wheels (single stage). There is an electric pump at the rear instead.

If the pump is working there is pressure and oil flow to keep the rear wheels pointing where the HICAS ECU wants them. If you simply disconnect the pump, there is potential for oil to slowly seep past the piston rings and you can end up with funny rear wheel alignment.

Removing the rear steering rack, HICAS ECU, oil lines (R32), electric pump (on R33), changing to an R33 (single stage pump) on R32, reducing the oil capacity of the power steering system (R32), removing the steel pipes that run from the front to the rear (R32) and the 3 solenoids (R32) all adds up to significant weight saving (27 kgs on our R32 GTST race car).

But the main advantage is the removal of something that changes the attitude of the rear of the car other then the driver. I like to be in control, not have some ECU doing it for me. It is very disconcerting to have chosen a line around a corner and then have the HICAS decide it wants to change it. So you correct for it and the HICAS changes it again. Very unsettling.

Somebody mentioned weight over the rear wheels and drags. Well my experience has been that if you take the weight out of the car (front or rear) it will accelerate faster. If the rear does not squat enough to get traction, then put some softer springs in it or higher profile tyres or lower pressures. It will be faster every time than sticking a lump of lead in the boot.

Hope that adds to the discussion.

[Jay95R33]

Just for the record - the best launch I have ever done is when I had my parents in the back seat !! Poor Mum crapped herself !! But she loved it.. But in my case I've got hard suspension in the back, so really, to get good launches you need soft suspension just what SydneyKid said.

Re: the unplugging the HICAS ECU - I've said it once before that you need to lock the rear wheels into position. Hence why TOMEI have shims with thier kits that are placed in the rods to LOCK the wheel position.

J

[Ender]

As for weight removing hicas..I didn't weigh fluid, or replace my pump with the 33 one, Hence the difference I guess....

Removing hicas and putting some adjustable suspension bits in the front end would have to be one of the best mods to a skyline in my opinion....

Cheers,

[R31Nismoid]

Originally posted by Ender

1 tankof petrol is 50kgs not 15-20kgs so yes...i agree you would feel it...

Soz! i meant that it does squat... and gets good traction.

On a 1/4 tank my car is far too wild to get traction.

with a 1/2-full tank my car launches with real good traction.

Now if HICAS was gone... then say, 20 kg... and a whole tank of fuel equals 50 kgs... then with 1/2 a tank of fuel i'd struggle for grip as opposed to a 1/4. ???

does that sounds right?

[scm]

i like my hicas ,good on the track and good when drifting.

[R31Nismoid]

yeah true... in the wet i love my hicas.

dunno what it's like to drive a car without one so i guess i'm a bit bias!

[sn00p]

reducing the oil capacity of the power steering system (R32)

Sydneykid - How did you do this? By using non-HICAS p/steering resovoir, or just put less oil in it.

[Ender]

Ppl talking about traction for dragging and stuff...one of the things you can do for your rear drive car to greatly improve traction if you have height adjustable suspension is to raise it up as high as you can...only for dragging obviously....this creates a higher center of gravity and thus more weight transfer onto the rear for more traction.....

No good lowering your car for dragging...

Cheers,

[Sydneykid]

Hi snOOp, the components are all full of oil. A lot of people weigh the bits dry, but forget about the oil that usually inside.