Got a question about cars? (2 Viewers)

[sikeveo]

FTHRW8 - about the discs, same thing happeend on my mums car, the discs were warped. The mechanic said that she probably went through a puddle after breaking hard....

 

[SlipStream]

SlipStream, lets see if you tell me something before I go to get it checked out. Problems with my car:
1) Every time I go over the slightest bump, there seems to be a "rattle" in the rear part of the chassis of the car, to get an idea of what it soudns likeimagine the chassis had come "off" the body and was sort of rattling. Possibly shocks? Whats your take

2)Squeaking brakes- Possibly worn brake pads, but unlikely due to when I last had them changed, going to try cleaning with a high pressure cleaner or it could be warped discs as is crazy common on these cars.

3) Squeaking axles- Ok, this I have NFI on, the rotation of the wheels has a squeak as well, WTF

The car's a V8 Au2 Wagon.

1) Yep, could be shocks. Could also be worn bushes. Or could be something abstract and simple like the muffler has come off a mount and is rocking up against the chassis, or something else not secured/bolted in properly. I was going to say it could be a very dead CV but Falcon wagons have live rear axles.

2) Glazed pads which is normal or the pads vibrating at high frequencies which can be solved with some anti-squeel compound or special brake pad sound-deadening grease. If it's really loud then yes the pads may have worn down to the little metal doodah that rubs against the disc to warn of low pad matter. Warped disc wouldn't make a sound - the brake pedal would pulsate when you brake.

3) Could perhaps be dead bearings, or the pads rubbing very gently on the disc, or if it's the rear you could have an ill-adjusted handbrake. Depends on what kind of sound it is.

Keep me posted - likely the problem will be an "ohhh why didn't I think of that" problem.

 

[FTHRW8]

Cheers, gettin my mates to check it out over the weekend. 2 & 3 I'll have to check, 1 I know it aint the muffler, Ive checked if anythign rattles upto the rear axle.

Good to see you're into motoring journalism too. I don't have the technical knowledge obviously, but I like it too

 

[SlipStream]

Cheers, gettin my mates to check it out over the weekend. 2 & 3 I'll have to check, 1 I know it aint the muffler, Ive checked if anythign rattles upto the rear axle.

Good to see you're into motoring journalism too. I don't have the technical knowledge obviously, but I like it too

^ No worries.

Yeh everything is set for my career - I managed to secure work experience at MOTOR magazine (my favourite car magazine) for next year and with enough sucking up I just might be able to secure some kind of junior editorial position there for 2007. Wouldn't that be just nice? That'd be the perfect start to my career goal of being Editor of MOTOR magazine before I turn 26 (2014)!

 

[FTHRW8]

Awesome work, I know firsthand how hard it is to get experience at the ACP publications. I myself tried Wheels and Speed. I ended up getting a gig at AutoSalon Magazine, which was then led by the brother of the then Speed editor lol.

Led to a short lived stint in freelancing here n there

Hope it works out for ya champ.

 

[braad]

2) Glazed pads which is normal or the pads vibrating at high frequencies which can be solved with some anti-squeel compound or special brake pad sound-deadening grease. If it's really loud then yes the pads may have worn down to the little metal doodah that rubs against the disc to warn of low pad matter. Warped disc wouldn't make a sound - the brake pedal would pulsate when you brake.

tell you a story where our calais started squeeling, and feeling damned wrong in the rear under brakes, we had replaced the brake pads, fluid etc (the norm) about 2-3 months before this problem occured. Started off on our trip back from canberra. the problem quietened down for about a week.It the started again one night when i was coming home from somewhere (probably a party) and noticed the rears were making a harsh metal against metal sound (the one we never want to hear from OUR cars ), a day later the car was sidelined as we'd checked over the brakes and couldnt see anything wrong (we hadnt taken the pads off at this stage) and tried to drive it...still squeeled.

a week later (we'd been busy with work & school) we checked the car and this time changed the rear pads and checked out the rear rotors, and fuck...they were scored, deep scratches right around (dont ask me why we missed this first time round *shrugs*). we took the pads off, and well, the cause for our screaming brakes was found. instead of having brake lining, we had metal rubbing the rotors. For some reason there was a heap of metal in the pads.

end result, new rear rotors, new pads...lucky they hadnt welded themselves together, considering the trip to canberra, driving around canberra and coming home.

eh...cars, weird things

 

[SlipStream]

Awesome work, I know firsthand how hard it is to get experience at the ACP publications. I myself tried Wheels and Speed. I ended up getting a gig at AutoSalon Magazine, which was then led by the brother of the then Speed editor lol.

Led to a short lived stint in freelancing here n there

Hope it works out for ya champ.

Cheers - it helps to know the editor of MOTOR personally... I might also be starting my career as an amateur racing car driver in '07 if I do well with a test for Aussie Racing Cars car number 34 sometime in the first half of next year! How exciting - if I do well I could even work my way up the ladder into professional status! That's a very big call, though... either way, exciting years ahead of me!

braad: ouch, yeh cars are bitches sometimes. My mate's Exa just blew a head gasket. Another rather large chunk of money down the gurgler...

 

[ToO LaZy ^*]

single clutch downshifting VS double clutch downshifting

besides the fact that SCDS rev-matches while the clutch is depressed while DCDS rev-match in neutral....what other differences are there between them?
pros / cons..?

 

[loquasagacious]

Well DCDS takes longer however is smoother because it allows the gears to physically slow more and thus engage smoother....

Um DCDS builds leg tone as opposed to mass like SCDS???? um i dunno i'm at a loss here

 

[Zozo6969]

Is it better to start a car with the clutch depressed or not (obviously if it is up it is in neutral)?

Also, does anyone know anything about the continuosly variable transmissions (CVT) like in the Honda Jazz. I know about them, like they were made so it can keep the car at optimum revs where there is most power available, and it just keeps at these revs (play Gran Turismo with the Jazz, does not change revs at all), but how exactly does it work?

 

[braad]

Is it better to start a car with the clutch depressed or not (obviously if it is up it is in neutral)?

Also, does anyone know anything about the continuosly variable transmissions (CVT) like in the Honda Jazz. I know about them, like they were made so it can keep the car at optimum revs where there is most power available, and it just keeps at these revs (play Gran Turismo with the Jazz, does not change revs at all), but how exactly does it work?

i'd say starting in either doesnt matter too much (i tend to start in Neutral just so i dont forget and leave the car in gear when starting )

the CVT in the Jazz was covered a while ago...im sorry i cant look it up, but if someone doesnt reply soon, you can always look it up

 

[redslert]

Is it better to start a car with the clutch depressed or not (obviously if it is up it is in neutral)?

Always start a manual car with clutch depressed even if you are in neutral. It's safer and does no damage.

 

[loquasagacious]

Well Zozo its a good habit to start the car with the clutch in for several reasons:
1)The car will never lurch anywhere because you've accidently left it in gear or forgotten that you left it in gear
2)It's a very easy way of telling if the seat is far enough foreward/back
3)It prevents any possible damage to the mechanicals.

As far as CVTs go: a CVT is a Continuously Variable Transmission which basically through the use of steel belts has an infinite number of ratios to select from whereas a conventional car has only five or so (each gear being a ratio). The CVT knows the optimum engine speed (best torque/kw versus fuel consumption and keeps the engine there through the use of the CVT to progressively and seamlessly change the ratios. In this way the wheel speed is progressively increased but engine speed stays the same.

One way to think of the advantages is to imagine the fuel savings that come with having a five speed over a four speed (or god help us - a three speed) these come because there's just one extra ratio available - imagine having several hundred extra. The other aspect of which is the ratio stepping - in a conventional five speed transmission it is neccessary to rev the engine past it's optimum speed to change up a gear at which point it drops down again to optimum. In a CVT the step up between ratios is very small so fuel is saved by not needing to run inefficiently to climb through the gears.

CVTs are very much the way of the future and I would expect them to be introduced on falcodores in a couple of models time (eg BH falcon and VF commo) they will certainly become the dominant transmission type.

What I would like to see though is more development of the jazz's gimmicky presets eg a button that would force the CVT to suddenly kick down by the equivalent of a gear or two in a conventional transmission and thus give the car a sudden kick in the go faster region. Also the development of sports modes where for instance the CVT kept the car revving faster than when in econ mode.

Hope that helped.

 

[Zozo6969]

Yeh thanks it's sort of clear. But I still don't get it, like how can it just change a ratio?

 

[Gavvvvvin]

How do you take off from a hill without rolling backwards? I know how to do it using the handbrake, but that seems rather a hassel when your only on a small hill at the lights or something?

Also how do you use a petrol pump?

 

[ToO LaZy ^*]

in a manual, you could use the heel-toe technique i suppose, or if youre extremely quick you could just use the normal take-off technique with minimal rollback.

for the heel-toe: (from a total stop)

1. use the ball of your right foot to hold the brake (or the left side of your right foot)
2. clutch in, put it in 1st
3. let the clutch out to friction point while adding some gas using the heel of your right foot (or right side of your right foot), while still applying the brakes
4. once you feel some 'push', completely release the brakes
5. fully release clutch slowly (usually slower than on a flat surface) while feeding it gas.

id personally think this would be more of a hassle then just using your handbrake.

 

[DaddyK]

wtf why the hell would you do all that?

Just find the friction point with the clutch and sit there, you dont even need to use gas or brake and you can sit there on any hill. A petrol pump? Put the nozzle in your tank and press the big trigger.

 

[ToO LaZy ^*]

1. clutch wear
2. smaller engines cant idle using just the clutch, itll stall and/or rollback, which wouldnt be too good if there people behind

 

[loquasagacious]

Holding at the friction point is generally a bad idea as it wears the clutch.

Personally I tend to use a heel-toe manouver to do a hill start with no handbrake eg:
1)Right Heel on brake toe on accelerator (its my pedal layout), left foot on clutch
2)Tickle the throttle a little bit
3)Release B-pedal (swivel foot) and depress A-Pedal whilst releasing C-pedal

The disadvantage (if it can be called that) is that when completed quickly this manouever may result in an illegal burnout (that is slight loss of traction and some noise).

Getting back to the CVT.

In a conventional gearbox you change a ratio by disengaging a gear (torque converter/clutch) and then engaging a new one - each gear being a ratio. In a CVT via the use of metal belts (sorry I cant really explain it well - try www.howstuffworks.com) the ratio can be varied with no engaging or disengaging - eg continuously.

 

[SlipStream]

ToO LaZy ^*, modern gearboxes have these things called synchros that eliminate the need for double clutching. I had to learn how to double clutch to drive my mum's Pajero, which has worn syncros on first and second - I don't drive it as much anymore, and now the skill I taught myself is more useful when driving big, quick cars like the R31 Skyline; when she doesn't want to select third quickly, a quick double-clutch motion soon solves that issue.

EDIT: I just noticed you were talking about double-clutch downchanges. You're not confusing double-clutching with heal-toeing, are you? Cos they're very different things.

As for hill starts, just learn and get used to the handbrake. If you try using something similar to a heal-toe movement you'll only come out looking like a dupe. lol, I'd avoid using DaddyK's method - you'll just destroy your clutch.