Quote:
Originally Posted by the_rifle
Si cu ce e diferit un motor M fatza de unul non M din punct de vedere mecanic ?
N-are tot pistoane unse ?
Sau dupa capul tau M-ul merge doar in tzarile calde ?
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Quote:
Originally Posted by the_rifle
Hai ca ma dai pe spate... Deci daca n-am M nu pot sa-i pun ulei 10w60... Deci dupa logica ta daca n-am motor de M nu pot sa-i pun nici jante de M ...
Da am retinut... Mai am multe de invatzat de pe acest forum...
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quote-urile astea spun multe despre cunostiintele tale. cu ce e diferit un motor M fata de unu non M? =) esti amuzant intr-o oarecare masura..
snt foarte multe diferente, dar principala diferenta (si relevanta in discutia de fata) este temperatura de funtionare. in functie de care iti alegi vascozitatea uleiului la cald. snt convins ca o sa te depaseasca un argument tehnic, dar cine e interesat:
"Lets look at what oil specs actually mean and particularly the higher number which is in fact the oils SAE number (the "w" number is in fact the cold crank viscosity and measured in a different way) The SAE number is measured by the oils viscosity at 100degC.
Your cars require according to the manufacturers specs, sae 30, 40 and in some cases sae 50.
To attain the relevent sae number the oil has to be at 100degC (no thinner than)
SAE 30 11cst approx
SAE 40 14cst approx
SAE 50 18cst approx
Centistokes (cst) is the measure of a fluid's resistance to flow (viscosity). It is calculated in terms of the time required for a standard quantity of fluid at a certain temperature to flow through a standard orifice. The higher the value, the more viscous the fluid.
As viscosity varies with temperature, the value is meaningless unless accompanied by the temperature at which it is measured. In the case of oils, viscosity is generally reported in centistokes (cst) and usually measured at 40degC and 100degC.
SAE 60 is in fact 24cst viscosity at 100degC!
This is 33% thicker than an sae 50, 70% thicker than an sae 40 and over 100% thicker than an sae 30!
So, what's the problem with this thickness?
Well, this is measured at 100degC and at lower temps (70-90degC) all oils are thicker than at 100degC so the problem is compounded to some extent.
The downsides of such a thick oil (when not specified) are as follows:
Additional friction, heat and wear.
A reduction of BHP at the wheels
Lower fuel consumption
The thicker the oil is the more friction and drag and the more power the engine needs to move it around the engine which inevitably translates to less at the wheels.
So, when do we spec a thicker oil?
Well, you will probably have seen us on occassions recommending a 10w-50 but only in these circumstances.
1. If the car is heavily modded and heat/oil temperatures are excessive.
2. If the car is used on track and heat/oil temperatures are excessive.
3. If it's required by the handbook.
In a worst case scenario with thick oils (when not required) is that you will experience air entrainment and cavitation inside the bearings at high RPM. Not clever stuff!"
(sursa: opieoils.co.uk)