trying to understand why tb cam specs so different from other non na engines

[gunzandgearz]

I reread my previous post and realized that I meant to say intake valve closing point because that determines how much air fuel gets trapped in cylinder before piston starts shoving air fuel back into intake tract.

 

[MCH86GN]

Turbo camshaft guide - The truth about camshafts and turbochargers

link

http://www.hotrod.com/how-to/engine/ctrp-1106-turbo-camshaft-guide/

 

[fastblackracing]

One thing you will find out is that our 3 bolt turbine housings have more back pressure restriction at elevated power levels than the turbo set ups that brand c,f and m use so the ultra low back pressure numbers that are reffered to with the new generation turbos dont really apply to our 3 bolts....... even with the current turbine wheels......... back pressure is always a concern for us......Now if you change to a 4 bolt style housing then things start to change......I read that carcraft hotrod article and was not impressed with what was in their, even the stuff KD had to say about our v6 did not seem right to me.....pretty sure our stock oem cam had 107 LSA and they tightened it up to 109??

 

[87GN_70GS]

I reread my previous post and realized that I meant to say intake valve closing point because that determines how much air fuel gets trapped in cylinder before piston starts shoving air fuel back into intake tract.

Even in a NA engine the cylinder is still filling at IVC, at high rpm due to inertia ram effect. In our cars, pressure overcomes any effort to push air back into the intake.

 

[gunzandgearz]

when the intake valve is closing the engine is on the compression stroke,close the valve too early you shut the door on cylinder filling,closethe valve too late, piston starts pushing a/f back into intake,less effective compression. both scenarios = bad this is why ivc is so important,even in turbo application because if you hang valve open too long on ivc ie compression cycle it starts putting pressure on piston, so now its fighting against boost pressure.on any engine the cylinder that is filling is on ivo during overlap period that's when exhaust valve is closing on exhaust cycle and the intake valve is just starting to open the residual pressure leaving combustion chamber helps to start pulling the fresh intake charge in.

 

[bison]

In our cars, pressure overcomes any effort to push air back into the intake.

Not true during overlap when the piston is at or near tdc. The exhaust pressure is going to be higher than intake pressure on 99.9% of anything that's run hard. This is exactly why the valve timing is important.


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[gunzandgearz]

What part isn't true

 

[87GN_70GS]

Not true during overlap when the piston is at or near tdc. The exhaust pressure is going to be higher than intake pressure on 99.9% of anything that's run hard. This is exactly why the valve timing is important.


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Was referring to filling at IVC during intake stroke

 

[gunzandgearz]

G.otcha, bye the way nice car for youre avatar picture, my dad has 72 convert skylark.