A motor running at 450 -500 rwhp with a supercharger is using anywhere from 90 -140 hp to turn the belt depending on the supercharger used. (Throw in some more realistic numbers if you have them.) The turbo is using significantly less HP.

Does this correlate to less load on the crank/rods?

Theoretically. if you match the boost levels between the turbo and the SC, the crank/rods see the same load, but more power at the flywheel with the turbo. Anyone have a guess at how much more?

 

Re: Does a turbo put less stress on the rods then a Supercharger?

When the Piston is at the top of its cycle, there's a certain degree of backpressure that softens the pull on the Rod from the Piston due to inertia. The load on the Crank is different because it doesn't have the Radial "pull" from the belt.

"In General" people can make the same power at 2-4 psi less on the Turbo than with the Blower.
issuez

 

When I switched from a Vortech T-trim at 13 psi to a T-76GTS at 13 psi, I gained 30 rwhp. That's with a blower cam and a log header for the turbo.

 

Re: Does a turbo put less stress on the rods then a Supercharger?

Thanks for the responses!!

So 'softening' of the inertia puts less stretch on the rods ( a good thing).
So rwhp being equal the turbo car is putting less load on the rods and crank?

And the 30 rwhp you gained was with the same loading of the crank/rods, in essence 30 free hp without greater stress to the motor?

If I am missing or misinterpreting something here please jump in!!

 

Re: Does a turbo put less stress on the rods then a Supercharger?

I think the stress was the same, but at a higher power level. If I had subtracted 2 psi, then it would have made the same amount of power with less boost and stress.

 

RWHP being equal, there is less stress on the rods and crank. The 30 HP was gained when comparing the 13psi backpressure in the intake.

As far as the stress on the engine goes, think of your shoes. Standing flat-footed, your feet are only supporting the weight of you. Now pull on a locked door with 10lb of force, the shoes are now supporting the weight of you and supporting the lateral load of your pulling compounded by the moment caused by the distance from your arm to your feet.

Now let go of the door and hold a 10lb weight. Your shoes are no longer supporting a lateral load, but they're supporting addition force in the same direction as the weight of you.

That's essentially what's goin on in the swap from the blower to the turbo. The additional load from the belt is removed, yet the increased HP from the increased efficiency is still applied. So there might not necessarily be "less" stress on the crank, but it's in a mode that the crank is "designed" to handle.
issuez

 

In your door analogy, with a supercharger wouldn't you have the lateral stress and the ten pound weight? I mean wouldn't it be like holding the ten pound weight and pulling on the door at the same time? where with the turbo it would just be the weight? just a question that came into my head while reading your post.

 

Basically

 

Thanks! Good analogy!

 

That's what I was thinking also. But still, pretty good analogy.

 

Dont know if im saying this right BUT with a supercharger you will have steadily increasing power cauz its directly related to rpm in constant drive, so you should have a steady increase in boost.
With a turbo depending on the size (im assuming t 70 on a v8) where there is considerable lag there tends to be an explosion of power. Wouldnt that put more stress on internals, drivetrain, etc then a supercharger since the boost would come on exponentially?

 

Once your turbo kit arrives, ask yourself that question

 

It's actually quite the opposite. The turbo takes .5 - 1 second to spool up, whereas the supercharger makes all its power instantly. My 60' time went from 1.52 with the supercharger to 1.8 with the turbo.

 

Read Maximum Boost. There's a good explanation of why turbochargers are easier on the rotating group.
Now a turbo's effect on the torque converter; that's a different story.

 

Ok, does it have a happy ending for the torque converter?

 

What is the def of turbo lag, time before 0 psi (vacuum) or after 0 psi (boost)?
I cant wait to finish install i wanna see how the boost hits, I thought it was more explosive than a supercharger.... When the turbo is big enough... Not in the small turbo cases..... Havnt played with a big turbo yet just theorizing...

 

Very good info here for a sticky by issuez. Exact explanation of the loads. Very good carry on.