Turbo Cams

JeremyH

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Short answer is yes it would hinder it overall through the curve and power band when compared to something made for a turbo application not to say it would not make some torque and power in areas. Which could be ok depending on the application. In general the specs for a blower specific cam are indeed completely wrong for a turbo, the exact opposite(on the exhaust side anyway). That cam you have would be considered a max effort blower cam as well making it not overall idea for sure. Good news is its an excellent cam for a blower setup so would be easy to sell and get something appropriate.

Long answer is you have to look at how cam specs affect power. A basic na or blower cam upgrade will increase lift and duration on both sides and tighten the lsa increasing open and closed valve overlap time, which raises effective compression which increases torque and brings peak torque in sooner which translates to more flow/peak power while narrowing the power band up top. The longer closed overlap helps build pressure on the intake valve on a rpm set compressor and the longer open overlap allows the new intake charge to help evacuate the previous exhaust charge from the previous cycle as well. Makes perfect sense for these applications as that's how a na and blower setups use rpm and ve to make more power so they compliment each other.

A turbo really cant use this effect of a "peak aggressive" cam with more flow on both sides. That flow up top still has to get out the head and through the exhaust but due to having another load after the pump(motor) with increased exhaust pressure and temperature it doesn't react the same. So when you want to go ahead and optimize the cam for it to maybe get better low end and more power its often a custom grind as it doesn't translate like any other setup being its load based and you have to address reversion and turbine drive pressure which can be higher than intake pressure.

To dig deeper, the Intake side of the cam is not much different. More lift and duration will get more air in so you can run more fuel and make more power. This is grossly unchanged be it na or a belt or turbine driven compressor.

Exhaust side of the cam is where the big fundamental difference is. Due to the exhaust restriction you have to address reversion other wise you negate the power as the pump(motor) has to fight to push the air out. So a well spec'd turbo cam will not have a lot more lift and duration on exhaust side compared to the intake side which is what you do want for na and blower.

It has to do with valve overlap as well, specifically open valve over lap for a turbo which on a sohc setup is soley based on the lsa and centerline. You can't use that naturally scavenge flow with a turbo you want to close that exhaust valve sooner and not open it as far so you aren't fighting exhaust drive pressure and you can still force more air in. So a wider lsa would be better. The mechanical advantage of the load based turbo and drive pressure will then drive up effective compression in the cylinder and in turn peak torque instead of the cam/motor having to do it, and then by protecting the motor from the back pressure you get more power through the upper range. That's why when you spec a turbo cam, things like vehicle weight, desired rpm, gearing and turbine design/setup come into play.

So to show you these fundamentals on the cam specs you listed it would look like this. Drop that extra exhaust lift from .550" to the same as intake side .535'" Now you aren't pushing that exhaust valve open further than the intake. Decrease that exhaust duration, you still need more than intake since there's more heat and pressure coming out but not so drastic so drop exhaust duration from 236 to 230-232. And then finally to decrease valve overlap and combat reversion so both intake and exhaust valves aren't open at the same time as long you would widen that lsa some. I would go from 112 to 114-115. Cam centerline can stay the same typically 110 to 112 for an ohc. (more important if you lock the cam).

My best advice for turbo and cam, either leave in the stock cam or a mild na cam, and if your trying to optimize the setup get a reputable company to spec a custom turbo grind for your setup and goals. My custom cams for my setup were actually cheaper than my original off the shelf na comp cams I had.
 
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TzReddy

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I appreciate all the advice. You have been super helpful and giving me great information. Where did you get your custom grind cams? I already have upgraded springs, vct lockout and phasers. So I guess I will start looking for different cams
 

JeremyH

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No prob. I got mine from Bullet Racing. I already had springs, retainers and phasers limiters as well, so just pulled my comp cams and swapped them in.
 

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