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wondering if you guys know why toda spec Bs require about 12.3:1 CR and skunk2 stage 2 only require 11.4:1 CR. i thought you raised the CR b/c of the longer duration which makes you lose pressure up the intake port but the skunk2 stage 2 have more duration than the toda spec Bs. u guys know why??


Toda B's ($980/pr)

INTAKE lift - 12 mm,duration - 255 @1mm
EXHAUST lift - 12mm, duration - 245 @1mm

Stage II (not street legal, $700-725/pr)
INTAKE lift- 12.07 mm, duration 265 @ 1mm
EXHAUST lift - 11.6 mm, duration 256 @ 1mm
 

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have you ever seen a cam's valve opening and closing spec sheet? have you ever degreed a cam before on install?

if not, then I suggest you go to the cranecams.com site and read upon what these basics about cams mean...then you will understand what the ABDC spec is first...then we can move forward from there...

otherwise, you will have no clue about what I just put up in the first reply.
 

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remember BDC (Bottom Dead Center)is when the piston is at the very bottom of it's travel. The piston is travelling up over a total time from BDC to TDC (top dead center). It is squeezing the air fuel mix on the compression stroke over a total time from BDC to TDC.

After BDC (ABDC) means the exact time when the piston is rising. So on the compression stroke, we can locate exactly where the piston is when it is squeezing the air fuel mix by using the ABDC number or spec. The higher the ABDC number, the further up it has travelled away from the very bottom most point. The higher the ABDC number the more squeeze has occurred.

The intake cam has a spec sheet which tells you exactly when the intake valve opens and closes. They give you the exact time when the valve opens BTDC (before top dead center) and when the valve closes (ABDC). We are interested in exactly when does it close while the piston is squeezing. This is why we focus in on the intake valve closing spec. The intake valve closing spec is given in degrees ABDC.

The amount of time from BDC to this closing spec is how long the intake valve is open AS THE PISToN IS SQUEEZING THE AIR FUEL MIX on the compression stroke.

The longer that time from BDC to valve closing is determines how much mix goes up the intake port and how much cylinder pressure you lose.

So you see, the Skunk 2 stage 2 cam can have a longer duration but it may start opening earlier and the valve closes ealier ABDC compared to the Toda.

So if the Skunk2's ABDC closing point is earlier, less mix has been squeezed up into the intake port while the intake valve is open during the compression stroke.

therefore it needs less static CR to get back the same cylinder pressure or dynamic CR.
 

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wait skunk2 cams are non-street legal?!?!??!
 

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whew! <<whips brow>> dont matter newaz no emissions down here <<muhahahahahah>>
 

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one quick, simple question i have about dynamic versus static compresion then is; since the Toda B/C needs 12.3 static, while the skunk2 can make due on 11.4, will they both be able to run on 91-92 oct pump gas? i know 11.4:1 isnt' that big of a deal, but what about the Toda B/C?

if the dynamic CR is lower with the Toda B/C, does this mean that they can still use pump gas even with a high 12.3;1 static CR?
 

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I'm running on pump gas (Sunoco 94 octane). There are lots of people (Endyn/Wiseco or CTR pistons in an ITR and Spec C ) running on pump gas. The thing they don't tell you is their other fuel mods and extensive ECU tuning (usually a Hondata or APex Power FC or custom programmed chip).
 
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