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Re: Fleas have 9 lives too :(
[Re: ]
#546957
22/02/2008 01:55
22/02/2008 01:55
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Joined: Dec 2005
Posts: 5,405 Castle Combe
Flea
OP
Forum is my life
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OP
Forum is my life
Joined: Dec 2005
Posts: 5,405
Castle Combe
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This may seem OTT to some, but seeing how many times this has happened to you , i would want to try and put an end to it once and for all - this is what i would do. I would install a small spy camera looking at the belts and then do some high rpm runs on the dyno and watch the footage to see if you can see what the belt is doing during a high rpm run down. This in my opinion is the only real of having some sort of chance to understand(and see!)EXACTLY what is happening to the belt, otherwise you could just keep ending up guessing and speculating. I know it will be spinning extremely quickly, but you could record the footage and slow it down afterwards. You can buy a small camera kit here for less than a £100 and if it doesnt work, just sell it on or have some fun doing other things with it..... http://www.wirelesscamera.co.uk/spycam-spy-camera.htm I know what you mean, it would be good to see what is going on at the moment of destruction. The reality is the belt will last a good length of time i.e. I have done countless blasts, drag runs and track days where it really gets a beating but ends up ok. I have checked it before and after and there is no visible sign of wear i.e. a slow wear and tear process. They literally appear to go bang when coming off the throttle at high rpm.
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Re: Fleas have 9 lives too :(
[Re: Flea]
#546969
22/02/2008 02:04
22/02/2008 02:04
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Joined: Jan 2006
Posts: 1,618 Oswestry
Genic
My life on the forum
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My life on the forum
Joined: Jan 2006
Posts: 1,618
Oswestry
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Re: Fleas have 9 lives too :(
[Re: Flea]
#546981
22/02/2008 02:10
22/02/2008 02:10
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Joined: Dec 2005
Posts: 9,706 Gone
Jimbo
Je suis un Coupé
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Je suis un Coupé
Joined: Dec 2005
Posts: 9,706
Gone
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Thinking about why the belt should shear on lift off, it must be put under some extra stress at the point but whats happening. I know the air-con disengages the clutch under hard acceleration to reduce the load on the engine but could the alternator be doing the same ? If it did then as soon as you lift off the throttle the alternator would immediatley act as a brake due to the load placed on it. Could the powersteering pump be doing the same, its spinning very quickly and producing its maximum pressure (Im guessing this is regulated in the pump) but the flow will be at its highest I would imagine, would this high flow then cause the pump to act momentary as a motor, even if its for a milli second, the engine has suddenly reduced rpm but the pump is still going at the original high speed, could cause stress on the belt ? Could this be the same for the water pump ? Just thinking aloud really Leight and trying to figure why its only on lift off. Gutted its happened again though
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Re: Fleas have 9 lives too :(
[Re: Jimbo]
#546983
22/02/2008 02:14
22/02/2008 02:14
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Joined: Dec 2005
Posts: 12,296 Sandhurst
Begbie
ex El Presidente
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ex El Presidente
I AM a Coop
Joined: Dec 2005
Posts: 12,296
Sandhurst
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Leighton, sorry to see that you have done another belt and potentinally more damage this time As with what Jimbo is saying above, thinking out loud, when on full chat the engine will tilt back due to the torque and when coming off lurches forward, would there be anything that causes a brief slack point on the belt that allows it to slip fractionally?
Your car is Usain Bolt with wellies
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Re: Fleas have 9 lives too :(
[Re: Jimbo]
#546987
22/02/2008 02:17
22/02/2008 02:17
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Nobby
Unregistered
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Nobby
Unregistered
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Engine mounts are all ok? ( I know this should really affect the belts, but a seriously rocking engine can't help)
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Re: Fleas have 9 lives too :(
[Re: ]
#547003
22/02/2008 02:39
22/02/2008 02:39
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Joined: Dec 2005
Posts: 5,405 Castle Combe
Flea
OP
Forum is my life
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OP
Forum is my life
Joined: Dec 2005
Posts: 5,405
Castle Combe
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Engine mounts are all ok? ( I know this should really affect the belts, but a seriously rocking engine can't help) Think so, I haven't noticed any play in the engine mounts. I have the uprated top left mount but will check the others.
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Re: Fleas have 9 lives too :(
[Re: Flea]
#547008
22/02/2008 02:45
22/02/2008 02:45
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Matty
Unregistered
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Matty
Unregistered
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Jesus, gutted for you mate.
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Re: Fleas have 9 lives too :(
[Re: Jimbo]
#547028
22/02/2008 03:13
22/02/2008 03:13
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Joined: Dec 2005
Posts: 33,674 Berlin
barnacle
Club Member 18 - ex-Minister without Portfolio
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Club Member 18 - ex-Minister without Portfolio
Forum Demigod
Joined: Dec 2005
Posts: 33,674
Berlin
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I know the air-con disengages the clutch under hard acceleration to reduce the load on the engine but could the alternator be doing the same ? If it did then as soon as you lift off the throttle the alternator would immediatley act as a brake due to the load placed on it. The alternator system is completely self-contained; if the output voltage is low, the regulator increases the field current to increase the voltage. But... the electrical load should be pretty constant. The lights, aircon clutch, and fans/screen heaters are the biggest load; the ECU requirement is only a few watts, and the injectors are of course turned off on over-run anyway (though I think the sparks still happen). Hmmm... I wonder how fast the aircon clutch comes in once you come off peak throttle? If it's instantaneous, you've got a few hundred watts load on the alternator as the a/c clutch engages, *plus* whatever the pump load is on the aircon itself, and all that's going onto the aux belts. I don't know what the load is on the aux belt in normal running, but that's got to have the potential to be a serious and sudden shock load... Ideally, you'd want to wait until you were either at idle or steady speed again before you turned it all on again, I suppose, when the engine is back in closed loop and the loads are more nominal.
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Re: Fleas have 9 lives too :(
[Re: Flea]
#547205
22/02/2008 05:44
22/02/2008 05:44
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suba
Unregistered
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suba
Unregistered
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Really sorry to hear about this Leight - I hope it's not too bad for you - there has got to be something out of alignment or worn I think, the question is what? How many cars do we know of that run with aircon and a fair bit over 400 bhp? I thought that there was no way that the aux belt could fowl up the cambelt with the protection pulley (which is why I got one...)
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Re: Fleas have 9 lives too :(
[Re: ]
#547212
22/02/2008 05:55
22/02/2008 05:55
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h2ypr
Unregistered
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h2ypr
Unregistered
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I thought that there was no way that the aux belt could fowl up the cambelt with the protection pulley (which is why I got one...)
Same here. Ross
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Re: Fleas have 9 lives too :(
[Re: ]
#547268
22/02/2008 13:21
22/02/2008 13:21
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Joined: Dec 2005
Posts: 4,080 Dumfriesshire, Scotland
Baz76
Forum is my job
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Forum is my job
Joined: Dec 2005
Posts: 4,080
Dumfriesshire, Scotland
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I think some of the new cars are coming fitted with free-wheeling alternators which disengage on over-run. Don't know whether you could adapt one to fit and work,seems a lot of work though for something that runs fine on other high powered Coop's . Has the crankshaft pulley been the same one for all the breakages or was it swapped when you had it adapted? Baz
Project LE+
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Re: Fleas have 9 lives too :(
[Re: Baz76]
#547289
22/02/2008 14:18
22/02/2008 14:18
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Duffman
Unregistered
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Duffman
Unregistered
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I know its a bit of a pig but do you know or can you tell where they brake most often at the top or the bottom of the belt system or do they brake randomly. I know you mentioned they seem to brake on liftoff at v.high rpm, where there would be some sort of large braking motion in the belt like a kick back. You really need some sort of eye in the area you think it brakes, run up the power and watch carefully.
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Re: Fleas have 9 lives too :(
[Re: ]
#547305
22/02/2008 14:48
22/02/2008 14:48
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Joined: Dec 2005
Posts: 1,059 Drakelow
Jamiepm
Club member 1989
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Club member 1989
Enjoying the ride
Joined: Dec 2005
Posts: 1,059
Drakelow
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Would there be any mileage in altering the size of the pulleys to be larger so the overall speed/rotation of the belts is slower. If I understand correctly Leighton you run the highest rpm of any coupe and is that simply the root cause.Whilst it is going away from 'standard' your car is also far from standard.
Jamie
She's alive!
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Re: Fleas have 9 lives too :(
[Re: Jamiepm]
#547309
22/02/2008 14:56
22/02/2008 14:56
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Duffman
Unregistered
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Duffman
Unregistered
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So what your saying is you think the belts snap nearer the bottom and around the area of the crank pully ? Also what gear do they brake in any sort of pattern ? sorry for all the q's im quite interested.
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Re: Fleas have 9 lives too :(
[Re: ]
#547320
22/02/2008 15:04
22/02/2008 15:04
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Joined: Dec 2005
Posts: 5,405 Castle Combe
Flea
OP
Forum is my life
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OP
Forum is my life
Joined: Dec 2005
Posts: 5,405
Castle Combe
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So what your saying is you think the belts snap nearer the bottom and around the area of the crank pully ? Also what gear do they brake in any sort of pattern ? sorry for all the q's im quite interested. Not sure whether they break at the bottom or top of the pulley but normally they shred along the belt not through it.
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Re: Fleas have 9 lives too :(
[Re: Flea]
#547329
22/02/2008 15:12
22/02/2008 15:12
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circolo
Unregistered
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circolo
Unregistered
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Probaly talking out of my ãrse on this. But if the indication is the belt is slipping off the pulley. Could a pulley be machine with a lip? So in effect the belt is held in a track on the pulley.
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Re: Fleas have 9 lives too :(
[Re: ]
#547334
22/02/2008 15:21
22/02/2008 15:21
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AlistairM
Unregistered
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AlistairM
Unregistered
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Forgive me for meing clueless but,some cars use chains rather than belts on the engine.
They're supposed to last alot longer but I don't really know that much on the subject.
It it possible to retrofit the fiat engine with a chain rather than a belt?
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Re: Fleas have 9 lives too :(
[Re: Nellybear]
#547401
22/02/2008 16:29
22/02/2008 16:29
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Nobby
Unregistered
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Nobby
Unregistered
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For using chains you need to keep them enclosed and some sort of oiling system. Complicated.
I'd prefer machined ally pulley' with extra lips each side, strenghtened belts and some sort of protection plate to cover the cambel bottom pulley.
P.S Presumably if you alter the size of pulleys then it might have an effect on the components performance. An alternator with a smaller pulley might be spinning too quickly, or too big and it won't be spinning fast enough.
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