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Не не не ти просто продължаваш да ме изумяваш с теориите си  . Както и преди ти казах не бъди ГОЛОСЛОВЕН......просто така само се джавкаме а от това нема смисъл сам го знаеш. Както ти казах питай твоя приятел Дунев и не мога да разбера що като спомена името му ти все се палиш да не би ти да си некой от Дуневците  , знам ли вече нищо не може да ме учуди. Аз обаче понеже знам какво говоря и съм сигурен в приказките си ти намерих еи сега едно текстче за да се пообразоваш и ти малко.........ами приятно четене и ако имаш нещо напротив след като попрочетеш пак заповядай в темата за да споделиш възраженията си
Ето текста :
Cams And CR
Most cam companies recommend increased CR to be used with their "higher performance" cams. Why is this necessary or recommended?
Let's review CR and what it really means. "Static" or "rated" CR is a ratio of the fixed volume of space above the piston top in the cylinder at Top Dead Center (TDC), to the volume of space displaced by the piston when moving from bottom dead center (BDC) to top dead center. When we look at actual cam timing specs, we find that the intake valve does not close until sometime after BDC. There can be no compression until the intake valve closes, so actual CR will be less then the static. How much less will be determined by the closing point of the intake valve. This actual CR will be referred to as the "dynamic" CR. These two different CR values are predictable and calculable. There is a third type of CR which represents the total cylinder pressure, and is the result of many more variables, but this value is unpredictable and for all practical purposes, unmeasurable. We will discuss it in later sessions.
Here are some examples of static CR and dynamic CR of a given engine using different cams. The dynamic values are as calculated by a Performance Trends Engine Analyzer program, and they may vary slightly from the absolute values. However, they will suffice for comparison purposes. There are equivalent math formula for calculating these values, but are quite involved. Assuming a 462 engine with different static CR values as noted, the real (dynamic) CR will be listed by cam type.
Comp Cams 268H (Intake 218 duration, 106 LC, Exhaust 218 duration, 114 LC). Intake valve closes at 35 degrees ABDC.
8 Static CR, Dynamic CR = 6.14
9 Static CR, Dynamic CR = 6.87
10 Static CR, Dynamic CR = 7.6
Comp Cams P-306R (Intake 275 duration, 102 LC installed,, Exhaust 278, 106 LC
installed). Intake valve closes at 59.5 degrees ABDC.
10 Static CR, Dynamic CR = 5.09
11 Static CR, Dynamic CR = 5.55
12 Static CR, Dynamic CR = 6.00
13 Static CR, Dynamic CR = 6.46
What do these numbers mean in regards to practical CR? What they show is that a shorter duration/ advanced intake lobe cam, will have much higher real compression then a long duration high performance cam in the same engine. Note that the 268H provides higher real CR with 8-1 rated CR then does the 275/278 at 12 - 1 rated (static) CR. How can we use this information? First, if we have a factory high-CR engine, we sure as heck don't want to install a cam like the 268H. We want to look for a cam that will provide the desired power range while keeping the dynamic CR as low as possible/practical. Note the intake closing points of the two cams above - the 268H closes at 35, and the race cam closes at 59.5. If we can find a cam that has the intake closing later then 35 but before 59, we should have a better chance to live with the resulting CR. How abut the Pontiac cam grinds?
744 (RA III) (Intake 224, LC 113, Exhaust 236, LC 118) same 462 engine. Intake valve closes at 45 degrees ABDC.
8 Static CR, Dynamic CR = 5.6
9 Static CR, Dynamic CR = 6.25
10 Static CR, Dynamic CR = 6.91
041 (RA IV) Intake 230, LC 112, Exhaust 240, LC 115). Intake valve closes at 47 degrees ABDC.
8 Static CR, Dynamic CR = 5.42
9 Static CR, Dynamic CR = 6.05
10 Static CR, Dynamic CR = 6.69
How about the cam that I use - Wolverine 234/244? (Intake 234, LC 107, Exhaust 244, LC 117). Intake valve closes at 44 degrees ABDC.
8 Static CR, Dynamic CR = 5.55
9 Static CR, Dynamic CR = 6.19
10 Static CR, Dynamic CR = 6.84
Пак ти казвам кажи с кое не си съгласен, защото материали по темата има не е като да нема така че........
Сега сигурно ще се хванеш за понятието "dynamic" CR и че то не е това което е нали така
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Jamie :-)))))))) [re: jamie]
