New Arrival Suggestions

[John Sims]

ORIGINAL: sawood12

....... Also don't forget that ABS cuts in before the tyres actually loose grip ...

And I thought it compared the speed of all four wheels and then started working if one of the wheels suddenly went much slower (ie locked) []

Ignoring that, I see your point with regard to the brakes going on an off with ABS reducing ultimate braking. I'm not sure I would go for disabling the ABS though as (so I understand) you can still steer and brake with ABS. If things get exciting I think I would like all safety nets available.

 

[carlmthompson]

ORIGINAL: sawood12

....... Also don't forget that ABS cuts in before the tyres actually loose grip ...

It cuts in when it senses an imbalance between the rotational speeds of the wheels - or to put it another way, when one locks! ABS sensors are also used in newer cars for traction control using the same principle.

I agree though, you're going to get much more effective braking by not triggering the ABS, but it's nice to have it there in case you do try too hard and panic - over - cadence sets in....

Edited to say that the 944 ABS isn't that modern, so when it kicks in it feels a bit "floaty". I do agree that it's set at a good point too kick in though.

Also edited 'cos the wrong person was quoted originaly (John)

 

[Hilux]

Interesting! I had assumed that because the ABS is working grip has gone and therefore braking is too hard. I endeavour, not always successfully, to try to keep just off the ABS working.

In the early days of ABS I understand BMW racers would dive much deeper into corners and trail brake letting the ABS do it's thing around the corner. I've never had the nerve to try it in the 944.

So what it the view of the masses then?

a) Brake as hard as possible and let the ABS sort it out.

b) Brake as hard as possible without the ABS intervening

I look forward to your comments.

I find that with my ABS there are longer periods between the off and on than with modern cars in my opinion. At Bedford I could brake really late on turn 1 and as the ABS kicked in start to steer the corner. I can see how trail braking would work better with ABS but I need about 500 more track hours to perfect my cr*ppy driving anyway [&:]

 

[sawood12]

I would never suggest to anyone to disconnect their ABS on tack days, especially if i'm on it, but I was just highlighting that you can disconnect it if you wanted to. Also just to clarify a point I was trying to get over in my last post: A GOOD driver can brake better without ABS but the problem with ABS is that because the system predicts when a wheel is going to lock up there are limits set by the manufacturer as to how close to the limit the ABS will kick in. But I still maintain that ABS works by cutting in before wheels loose traction and doesn't wait until a wheel actually locks up before kicking in. That is why some modern cars the ABS seems to cut in very early (i.e. like with my wifes Mini).

Obviously the main advantage of ABS is that you can steer whilst braking however when on track if you are driving in a textbook fashion you should be doing all your braking in a straight line before you turn in so you can be on throttle as you go round the corner. My understanding about trail-braking is that it is primarily a technique to counteract understeer by loading up the front as you turn in (i.e. it is popular with 911 drivers). I think it still remains that the textbook driving technique where you do all your braking in a straight line before turn-in still remains the ideal technique (?).

 

[Neil Haughey]

This myth about braking better without ABS gets on my nerves. Honestly pull the fuse out, slap a g-tech pro on the dash and try some 60-0 runs. Last year I did about 20 runs over different days and always got between 127 feet and 130 feet. Without the ABS you might get one run at 125 feet but don't be surprised to get loads of runs at 140 feet or more.

What the guy said about how difficult it is to get the ABS to kick in on the track is true. I would only get the groaning sound for perhaps 1/3 or 1/4 of the deceleration usually about 1/2 way down since you always want to be easing the pressure of as one approaches the corner. This would have been on perhaps 2/3 rds of the laps when really on it.

If you don't ever hit the ABS on the track then you don't know where the limit is, and hence are not braking hard enough. Same goes for the nonsense often said about understeer and oversteer.

 

[Neil Haughey]

It doesn't actually. I used to work at a place that had very dusty roads around the parking areas and I would regularily get one wheel to lock at low speeds, the ABS would cut in but it still didn't stop one of the wheels from locking. I have also had this happen at 45-50 mph on the road when braking hard and getting one wheel onto a white line, huge screeching sound as the ABS was happy to let one wheel lock up completely.

It seems to me that the Porsche ABS is designed to cut in and out gently allowing the car to have maximum stability. As a comparison the system on my SAAB 9-5 feels much more aggresive. It got the car from 60-0 in 121 feet but the car was all over the road. Obviously designed for emergency stops only and would be a nightmare on a race track (assuming the brakes lasted more then 3 corners before overheating!).

 

[sawood12]

Neil, with all due respect my point is that a GOOD driver i.e. racing driver, can stop a car significantly quicker without ABS because they can take the braking right upto the limits of tyre adhesion and beyond the point where the ABS would normally cut in. Obviously i'm only talking about the context of running on a track, but nevertheless it is the case. If your car is only braking for 50% of the time how on earth can it slow the car more quickly than if the car is braking 100% of the time. And the whole point of ABS is that it is ANTI Lock Braking system i.e. it is supposed to prevent the brakes from locking. By leaving a wheel or wheels to actually lock up, even for an instant, defeats the object of the system. Once the wheel locks up you've lost grip and it takes precious parts of a second to release the brake, wait while the wheel accellarates back upto road speed again then re-apply the brake. And because the system has to guess when a wheel is about to lock up then by definition the system is going to activiate the system prior to the wheel actually loosing grip. A good racing driver can feel the limits of tyre adhesion and take the braking right upto that point and make small adjustments to the pressure on the pedal to keep the braking level on the limit. The ABS system cannot feel where this limit is and uses the assumptions and calculations programmed into it.

Also it was certainly the case with early ABS systems that if one wheel lost grip the ABS was also applied to the other three wheels, therefore not only are you getting reduced braking on the wheel that lost grip, you are getting reduced braking on the three wheels that have grip. Anywhat this is all purely academic because with power assisted brakes it's very difficult to get the level of feedback you need which is why racing cars tend to have no power assistance so as you have pointed out for us mere mortals in our cars with relatively soft suspension, rubber bushes and power assisted brakes are probably not as capable of out-braking the ABS system consistantly.

 

[Neil Haughey]

Like I said slap a gtech on and try for yourself, also look at my numbers and do the maths for yourself. Then compare to the test figures for modern cars printed in mags like Autocar and you will see that stock 944 S2/turbo on stock tyre sizes stops as well as a modern Porsche or just about any other high performance car (close to 1g on poor UK B road surface). In all these tests the ABS was full on for pretty much all of the deceleration. Significantly better without ABS? well if you mean a couple of feet is significant then over a lap with perhaps 2 big stops we are talking about 100ths of a second.
I won't deny that it is possible to get a car to stop faster without ABS but in all honesty we are talking about tiny almost insignificant differences.

 

[NeilW]

Neil, fully agree. Also, the non-ABS racing driver may be able to better the ABS system on occasion, but, it only takes him to make a mistake braking for one corner and his advantage is lost. He is human therefore fallible and it's well known that juggling several activities in parallel leads to mistakes. By relying on ABS surely the driver is able to devote more of his sensory input processing to other aspects of driving, e.g. when to turn in, is anyone next to me, are the tyres gripping, etc. Accepted that this removes part of the skill of driving and could therefore be a reason for less overtaking (and therefore bad!) but in terms of repeatable lap times is superior.

 

[Hilux]

the Porsche ABS is designed to cut in and out gently allowing the car to have maximum stability

Dunno if thats true but I generally use the ABS during track days [8D] and note that you can feel and hear the wheel locking/unlocking without the vibrating pedal and `chatter` of more modern machinery hence my previous post that it is entirely steerable and you can carry braking late into the turn. Saved me running into the back of a car at Bedford when a tw*t in a scooby decided he`d go for the inside stupidly late at turn 1 and cut me up as he then naturally ran wide and I steered inside him with abs on full chat [8|]

At least I did and I am assuming from my experiences that the ABS works as my car didnt `groan` [&:] but it still grinds coffee when I start off?

I will have to say that with my current set up the retardation increase is very noticeable even compared to original Mo30 set up (must go to big blacks [8D][8D][8D]) so I find that I can `find` the ABS anytime I need []

 

[Neil Haughey]

Paul what I mean is that in general the car stays very stable when the ABS is doing its stuff. In me SAAB it is not very stable when the ABS is working. You can feel various wheels locking intermittently, grabing and then letting go. I don't tend to feel this so much in the S2. The groaning sound is the sound behind the dash of the ABS gubbins. When I got the car I used to think there was something wrong with the car until one day I almost didn't stop and realised it is the ABS! The lack of big vibrations in the pedal is as also a factor that made me think the system is very smooth in operation. Helps of course that our cars are so stable anyway.

 

[sawood12]

Well I was braking pretty hard at Bedford and my ABS wasn't kicking in even in the morning when the track was damp. I fear what i'm suffering from is that my suspension is so old and knackered that all its doing is absorbing all the energy from my Big Blacks and just causing the front of the car to dive even more with no corresponding increase in retardation force. After what Paul has just said i'm expecting a night and day improvement when my suspension is refreshed.

 

[Neil Haughey]

Just punched in the figures, 127 feet works out at 2.9 seconds and 0.94g average. This is identical to the time given by Autocar for the 997S. 120 feet is pretty close on 1g average and works out at about 2.75 seconds. I reckon on a test track with well warmed up tyres the S2/turbo brakes will perform better still. Note that looking through loads of test results shows very little difference between different manufacturers and types of car. Lastly it is interesting that TVR who don't believe in ABS have test times no better then Porsche or lots of other cars. Reminds me that the last 20 pages of Autocar is the best reason for buying that mag.

 

[Hilux]

Well I was braking pretty hard at Bedford and my ABS wasn't kicking in even in the morning when the track was damp.

Only at turn 1, dry conditions only, after that there wasnt much braking apart from the pre straight chicane as it was so tight. Most circuits dont have quite so tight corners after a longish fast bit (Mallory hairpin??)

 

[John Sims]

ORIGINAL: Hilux

......Most circuits dont have quite so tight corners after a longish fast bit (Mallory hairpin??)

But Mallory has the advantage of braking up hill and you don't get to full chat as you are accelerating up hill after the Esses.

The end of Revett at Snetterton and the end of Dunlop Straight at Donnington are particularly high on my sphincter chart. As is the hairpin at the end of the start finish straight at Pembrey (Hatches Hairpin). I have pictures of the discs glowing red on Sluggy (The Westfield) after hauling him up for the hairpin [] and he only had Capri 2.8i brakes.

 

[Hilux]

But Mallory has the advantage of braking up hill and you don't get to full chat as you are accelerating up hill after the Esses.

True but you can get there far too quick when your gearbox sticks in 4th so the anticipated engine braking isnt there at the esses [][8D][8D][]

The end of Revett at Snetterton and the end of Dunlop Straight at Donnington are particularly high on my sphincter chart. As is the hairpin at the end of the start finish straight at Pembrey (Hatches Hairpin). I have pictures of the discs glowing red on Sluggy (The Westfield) after hauling him up for the hairpin [] and he only had Capri 2.8i brakes.
#
Dont know Pembrey or Snetterton so I bow to that man but these are longer straights? tighter bends?..............have you (will you) trouser yourself in the 944 at these places too - especially with the big blacks and *cough* red stuff pads [][]

 

[Hilux]

After what Paul has just said i'm expecting a night and day improvement

Nnnnnnnnnnnnnoooooooooooooo..........................dont [8|]

Its NOT day and night.

1) As I stated on another thread I really needed to have driven a fresh or refurbished Mo30 as my opinion is subjective and related to my opinion and experiences.
2) I considered that my Mo30 was worn or baggy (it might not have been) cos of my Westy and Ginetta days so wanted stiffer and less roll.
3) It rolls less definitely BUT look at Rick`s photos with mine compared to Riverside's. The roll reductiuon is not huge but what it does is keep the tyres better planted BUT they all heat up evenly and more so so there`s a trade off.
4) It will roll but not in extremis and that reduction feels really flat inside the car. It was IMHO better at cornering than Riversides but its all down to tyres at this level and I am losing boost with a leaky cycling valve and also wasnt able to hold boost for long as it kept overboosting and cutting fuel so I had to let people by all day [&:][].
5) Also remember Andrew S had old Mo30 with big blacks and slicks so thats another way to go isnt it?

I think its the right way to go but its only a step in the right direction and definitely enhances the car by miles IMO

 

[sawood12]

Well Paul, if your M030 was a bit baggy my non-M030 is even moreso. I'm not necessarily expecting a night and day improvement in body roll as i'm not uprating my ARB's (apart from the bushes), not even to M030 bars, but i'm bound to get an improvement with the stiffer springs and fresh shocks. I am expecting a big improvement in dive under braking and squat under accellaration, both of which are particularly bad. With my current shock absorbers I liken it to driving a car with knackered shocks which considerably reduces braking efficiency. Don't worry Paul - I wont hold you to account if the difference is dissapointing!!

Andrew was certainly showing the way and demonstrates that ultimately you cannot beat driver skill, and that of course is the point of messing about with cars on tracks. The upgrading suspension and other parts is purely for fun!! I plan to upgrade to sticky tyres as my last chassis mod as I think you cannot really get a feel for the car if you have such sticky rubber. I like to feel the limits of the car, which is part of the point of going on track. Once i've finished uprating everything and I think I have a good feel for the car and I think my driver skills have come on more than what they are currently then i'll invest in a set of stickyer rubber. I've done quite a bit of karting so am used to feeling the car sliding around more under me but it is going to take alot more balls doing it in my 944 with another 30 or 40mph.

 

[Neil Haughey]

I find that I enjoy the 944 much more then prokarts for example. Very different dynamics. I had 2 spins on cold tyres last time I went in a prokart caused by braking to hard then not lifting smootly before turn in. Karts annoy me no end. Until you get it hooked up really well they are not much fun IMHO. Then the problem is that you have next to no power and massive grip so fast times is all about maintaining as much momemtum as possible.

Bizarely I found on the track at Bedford that I didn't really get such good feedback through the steering. Maybe it is the tyre type but I had to rely on what I could feel through the seat. I found in the dry that just before the back end could go at speed I would feel the car make tiny jumpy jitters like a tyre vibration. Latter on I realised that this could be tiny rubber balls being pulled of the tyre since the feeling was similar to that found if one strayed onto the marbles (only nothing like as bad). I didn't feel anything before understeering in the dry. When I had the 720 spin in the morning I felt that but by the time I followed the rear end with counter steering it was to late and I was just a passenger. Basically went in much to fast.

 

[944Turbo]

Prokarts are like buses, you want to try a 2 stroke for some excitement,
Tony