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paul
08-26-2004, 12:47 PM
ok have been wondering this for a while now and yes i am prob the most uneducated person on here so exuse my ignorence anyway


why is it that rally cars when hitting a corner make a skittiling sound? best i can describe it its not the gear box because it would do it all the time but just when they are against compression and shifting + braking before a corner a sort of skittiling (best i can describe it!) sound is herd why is this? :)

Matra et Alpine
08-26-2004, 12:55 PM
It's an anti-lag technique employed to keep the turbo spinning.

Basically it adjusts the ignition timing to ignite fuel in the chamber AS the exhaust valve opens, so the burning fuel spins the turbo.

The noise you hear is the retarded combustion through the turbo.

All explained - and warnings on the impact it has on the parts - at http://www.rallycars.com/Cars/bangbang.html

UK CARS
08-26-2004, 12:58 PM
It's an anti-lag technique employed to keep the turbo spinning.

Basically it adjusts the ignition timing to ignite fuel in the chamber AS the exhaust valve opens, so the burning fuel spins the turbo.

The noise you hear is the retarded combustion through the turbo.

All explained - and warnings on the impact it has on the parts - at http://www.rallycars.com/Cars/bangbang.html
Blew my mind :eek: Bang :D

Tuscan666
08-26-2004, 03:04 PM
It's an anti-lag technique employed to keep the turbo spinning.

Basically it adjusts the ignition timing to ignite fuel in the chamber AS the exhaust valve opens, so the burning fuel spins the turbo.

The noise you hear is the retarded combustion through the turbo.

All explained - and warnings on the impact it has on the parts - at http://www.rallycars.com/Cars/bangbang.html


Damn you know too much about rally cars! Do you work with them or something?

stratos
08-26-2004, 03:19 PM
Damn you know too much about rally cars! Do you work with them or something?

i don't have sure but i think matra is a co-driver :rolleyes: :confused: ....

Matra et Alpine
08-26-2004, 03:48 PM
Damn you know too much about rally cars! Do you work with them or something?
I've rallied on and off since I was 15 ( now 31 years ago ) !!

Rockefella
08-26-2004, 03:54 PM
matra is the ucp rally expert

Spastik_Roach
08-27-2004, 02:21 AM
Matra is the UCP Expert Full Stop :P

Tuscan666
08-27-2004, 10:20 AM
Wow thats cool, wish i was involved with rally at 15 lol

Ferrari Tifosi
08-27-2004, 01:28 PM
Cool little inovation that Anti-Lag system is. Never read about that before.

Do WRC cars use metal turbine blades or can they use ceramic blades?

Mustang
08-27-2004, 03:26 PM
i might be able to get a vid of this for you guys, on 12th of next month iam going to a rally and one of the enterents there has just baught a Hyundai WRC car - lasy years car - and he also has a full rally spec impreza that he runs too. should be an interesting battle this time with the 6R4's, Impreza's, EVO's, Darrians and now that Hyundai ;).



@ Matra, if you have TOO MUCH boost is it possible to blow the pistons ?

Coventrysucks
08-27-2004, 03:26 PM
Skittle shake - occurs when you've left an open packet of skittles in the glovebox, and a few escape during hard cornering. ;)

"The explosions which occur in the exhaust tubes generate important flames which can, sometimes, be seen at the end of the exhaust tube"

Important flames?

Matra et Alpine
08-27-2004, 04:03 PM
@ Matra, if you have TOO MUCH boost is it possible to blow the pistons ?
For sure.
You put too much fuel/air mixture in under V.high boost.

So one of 2 things happens.
On an otherwise untuned engine the compression stroke will blow head gasket, twist the head or bend a conrod.

If that doesn't happen then on the combusion stroke it's almost guaranteed to bend conrod, sheer gudgeon pin, , blow gaskets and maybe even manage to throw the head :)

megotmea7
08-27-2004, 04:05 PM
Matra, if you have TOO MUCH boost is it possible to blow the pistons ?
if you dont provide anough fuel the car can run lean and detonate which in some cases will blow a hole thru the psiton, if you dont run a high enough octane fuel for the compression and boost you can detonate with the same effect. also dependent on the material of the pistons and rods (holes in pistons and bent rods are pretty big problems, along with blown piston rings) so define what "too much boost" is what the compression of the engine is, ambient outside temperature, temperature drop after the intercooler/water injection/etc. if present, octane/type of fuel your running. and you can get a general idea based on these and several other variables(e.g. ignition timing)


and hey i talked about ALS first! :P

Mustang
08-27-2004, 04:12 PM
For sure.
You put too much fuel/air mixture in under V.high boost.

So one of 2 things happens.
On an otherwise untuned engine the compression stroke will blow head gasket, twist the head or bend a conrod.

If that doesn't happen then on the combusion stroke it's almost guaranteed to bend conrod, sheer gudgeon pin, , blow gaskets and maybe even manage to throw the head :)


thaught thats what happened, a guy in our rally club has a group N impreza, he was doing a rally in wales with full boost / anti-lag on, and woundered why it was chucking loads of smoke and stuff out. got home took engine block apart, took piston out a and a big chink dropped out the side of it :( he has just got a set flown over here from america and he will hopefully have the car ready for the rally in 2 weeks that i am at :)

NAZCA C2
08-28-2004, 10:58 AM
Could'nt the differentials cause a similar sound?

paul
09-07-2004, 11:12 AM
they would not do it into corners i don't think depends what rally cars run> lsd? but it normally only happens when against compression so is bound to be that anti lag technique / but the dif could make a skitting sound but would only happen at high speed i would think ?

Alastor
09-07-2004, 02:35 PM
Although I am relatively new to the board, I know that it is foolish to question Matra et Alpine’s wisdom. Nevertheless, I have my doubts as to whether or not what the original poster described as a “skittle” is in fact the AL system.

The following link is a video of a Subaru WRC car entering and exiting the equivalent of a hair pin (900Kb avi file).

http://jupiter.walagata.com/w/alastor/WRC.Subaru.Impreza.WRX.zip

Well before and most of the way through the corner a high pitched squeak (I am assuming this is the “skittle” noise) can be distinctly heard. Upon existing the corner the squeak is no longer present. Once on the straight a pop or bang can be heard during the up-shift, and then several more again at the end of the video (presumably from lifting off the accelerator).

It seems to me that the initial squeaking sounds more like a BOV or similar device. While the popping/banging could be caused by a AL system.

Even though there are not any question marks above, it is a question ;-)

Matra et Alpine
09-07-2004, 03:19 PM
Although I am relatively new to the board, I know that it is foolish to question Matra et Alpine’s wisdom. Nevertheless, I have my doubts as to whether or not what the original poster described as a “skittle” is in fact the AL system.
....
It seems to me that the initial squeaking sounds more like a BOV or similar device. While the popping/banging could be caused by a AL system.

Even though there are not any question marks above, it is a question ;-)
I agree the sound is NOT the same as the "classic ALS".
I checked and ALS are no longer the only method.
They also use a modified verison of the standard Exhaust Gas Recirculation.
However, I've not ben able to find any technical articles from any of the teams on their implementation of EGR and ALS.
I think you're right that it's the BOV we're hearing but that it's in a programmed mode as an EGR woudl need. So instead of jsut opening and releasing all the pressure, it's useing a slower controlled release and that woudl surely make a squeaking noise as heard.
I'll ask around guys at the next event, some of them work for the big guys :)

PS: It's never a problem to question my knowledge, I do it all the time.
AND this is a prime example of things moving on from the setups I'm experienced with and not hearing it first hand. The vid was a help. Hadn't released noticied it as a 'squeak' till then. Still not sure if that's the "skittle" though :)

KnifeEdge_2K1
09-07-2004, 03:53 PM
i know burning too rich a mixture is bad for teh cat because the unburned fuel is really hot and will prolly ignite as it reaches the air at the end of the exhaust bla bla bla but what if there was too thin a mixture, like too much air and not enuff fuel, now this i imagine would only happen when a) u run outta fuel or b) ur ecu is playing tricks on u

i cant imagine there being any harmful effects since extra air is .. air
the only thing bad i can think of is bad economy because u waste energy compressing the air u dont need and blowing it out, oh that and the engine being seriously underpowered but that fits in to the other thing

but emmissions rating will be phenomenal :D

KnifeEdge_2K1
09-07-2004, 04:02 PM
oh and ive never heard of it being reffered to as skittling more of a popping sound, like when u microwave popcorn

its basically an engine misfire but deliberately caused by the ecu to keept the turbo spinning (i came to the same conclusion as matra)

as the car goes up to a corner a driver would lift off which means the revs drop, and the turbo's turbine's rpm dropping as well, now this is really bad when you exit the corner cuz u want the torque made by the turbo to get out fast, but here in lies the problem
if you want the turbo to keep spinning you have to add throttle, but if u add too much throttle u run into a tree, so you back off the throttle but that means your turbo slows down
what the anti lag system used by wrc cars is time the spark plug to fire right when the exhaust cam begins to open the exhaust valves, this causes the air fuel mixture to litterally explode out the manafold into the turbo and out the back of the exhaust, this keeps the turbo spinning while the bov is open to prevent the pressure from getting too high and stalling the turbine (VERY BAD THING)

now as you can imagine having air fuel mixture explode out the entire exhaust system and your turbo charger all the time cant be good so thats why its mainly used only on competition spec cars and also because they're so loud they're illegal on the streets, n even if you tried to get one on the streets ur car would start smoking cuz the explosions will melt ur catalytic converter and then ull have a hole in ur exhaust and the cops will come after u :D

megotmea7
09-07-2004, 05:31 PM
i cant imagine there being any harmful effects since extra air is .. air
a very sevire problem comes of running a car to lean, this is also effected by the ambient tmpertature and temp. drop after the intercooler, air pressure, and octane of fuel used. detonation is when the a:f ratio is so high that there is not anough fuel to prevent preigninition. when the a:f mixture goes off before the piston reaches tdc and the expanding gasses are pushing against the piston as it is going up or just reaching tdc. this is very bad for piston engines and even worse on rotaries(the explanatin is also slightly different on rotaries also) cars usually make more power whern running lean but there is the point where you stop making power and start detonating(usually tuned with ignition timing) and detonation is not good ;)

crisis
09-07-2004, 05:45 PM
It's an anti-lag technique employed to keep the turbo spinning.

Basically it adjusts the ignition timing to ignite fuel in the chamber AS the exhaust valve opens, so the burning fuel spins the turbo.

The noise you hear is the retarded combustion through the turbo.

All explained - and warnings on the impact it has on the parts - at http://www.rallycars.com/Cars/bangbang.html
Very informative. +3. Also because Ive been mean to you.

Blue Supra
09-07-2004, 07:19 PM
Is that system being referred to here the same as a misfiring system used in WRC?

Blue Supra
09-15-2004, 08:34 PM
anybody?

paul
09-16-2004, 12:17 PM
yes it is

KnifeEdge_2K1
09-16-2004, 08:16 PM
anybody?

no body calls it a misfiring system
misfiring is synonymous with the word bad

uve been watchign too much initial d

and thanks for the explanation about lean/rich ratios and thier effects on premature detonation :D to whoever wrote it im too lazy to check

Blue Supra
09-16-2004, 08:42 PM
Initial D owns me:D
i love it!

whiteballz
09-16-2004, 09:35 PM
i will ask in with shiftys dad when i next see him, he rallys STI's and im sure he will know.

Ferrari Tifosi
09-17-2004, 01:35 AM
no body calls it a misfiring system
misfiring is synonymous with the word bad

uve been watchign too much initial d

and thanks for the explanation about lean/rich ratios and thier effects on premature detonation :D to whoever wrote it im too lazy to check

Premature Detonation, isn't that a bit redundant? Anyways, I believe only a lean mixture will cause detonation, I may be wrong though.

KnifeEdge_2K1
09-17-2004, 05:50 PM
Although I am relatively new to the board, I know that it is foolish to question Matra et Alpine’s wisdom. Nevertheless, I have my doubts as to whether or not what the original poster described as a “skittle” is in fact the AL system.

The following link is a video of a Subaru WRC car entering and exiting the equivalent of a hair pin (900Kb avi file).

http://jupiter.walagata.com/w/alastor/WRC.Subaru.Impreza.WRX.zip

Well before and most of the way through the corner a high pitched squeak (I am assuming this is the “skittle” noise) can be distinctly heard. Upon existing the corner the squeak is no longer present. Once on the straight a pop or bang can be heard during the up-shift, and then several more again at the end of the video (presumably from lifting off the accelerator).

It seems to me that the initial squeaking sounds more like a BOV or similar device. While the popping/banging could be caused by a AL system.

Even though there are not any question marks above, it is a question ;-)

i know this is an old post but i just saw it, the only sounds i could make out was tire squeal, bov during the up changes, and the engine itself

Alastor
09-18-2004, 12:49 AM
i know this is an old post but i just saw it, the only sounds i could make out was tire squeal, bov during the up changes, and the engine itself

When I watch this video I hear lots of tire squealing also. But during the beginning of the video (0 -> 4 seconds) I hear a 'chirping' sound (I assume this 'chirp' is what the original poster described as a 'skittle'). To me this sounds like a BOV although it differs slightly from the traditional sound. Instead of making the normal "whoosh" it 'chirps' in short intervals. The only time I have heard a BOV make a 'chirping' sound is on a automatic AWD DSM. It is hard to say if the car is decelerating or accelerating during the corner entry so I wont make any assumption about it.

However, after clearing the corner the Subaru is accelerating away from the camera and at least one up-shift takes place. During the up-shift a short pop or rumble can be heard. As well during the initiation of the feint maneuver (~8 seconds) more rumbling occurs I assumed from releasing the accelerator. I was wondering if the rumbling could be caused by a anti-lag system.

paul
09-18-2004, 06:49 AM
yes my post was wanting to know what that exact chirping/clipping/skittle sound was just as the car is decelerating and maunovering round the corner it made a short sharp/skittle/chirping sounds in very short intervals and stopped soon as the car accelerates again!

johnnynumfiv
09-18-2004, 09:12 AM
couldn't it be ABS? if they brake hard, you should hear when the brakes go on and off with the skittle noise.

paul
09-18-2004, 09:27 AM
i don't think rally cars use abs ,lol

johnnynumfiv
09-18-2004, 10:22 AM
oooo, didn't know you were talking about rally cars, i haven't really followed the thread.

paul
09-18-2004, 11:15 AM
ha ha na its rally allright , just tring to define what this skittle/chirping sound is comming from , matra originally has said its an anit turbo lag technique so its got to be that!

KnifeEdge_2K1
09-18-2004, 08:16 PM
yeah, as the car is going into the corner the skittle is most likely the anti lag system keeping the turbo turbine speed up, it sounds like rapid firing roman candles :D

paul
09-19-2004, 02:42 AM
or a cage full of budjies!!!!

Alastor
09-27-2004, 10:16 AM
I took this sound clip from this On Board Camera Tramac Edition 2000 vid.

It is 37 seconds from a Peugeut 206:

http://jupiter.walagata.com/w/alastor/ALS.mp3

During braking there is a popping/banging noise sounds kind of like rocks bouncing around inside the cockpit. Just wondering if that is the AL system at work?

paul
09-27-2004, 12:42 PM
yes im guessing thats just the sound of the car repeatidly back firing because of the als