what is the equation to convert PSI to RPM and HP?

 

As soon as I find out, I think I may have something a lot of you will be interested to know.

 

I'm confused, what exactly do you mean conversion? There is no direct correlation between boost pressure, engine rpm, and horsepower output. It all depends on the size of the engine, the size of the turbo(s), and the max CFM that flows through the motor and exhaust.

 

Hmm, let me start over, i've talked to another person and he told me it wasn't going to be easy at all to convert the numbers.

So, here's the deal...i'm planning on stretching 6 OEM VQ35DE rods and compressing 6 OEM VQ35DE rods and see how much average PSI it takes to snap them.

I need to know what this all is going to give me. It sounds like there are a few equations you are going to need to do. In theory, you know what PSI it takes to snap the rods, so you compare that to the pressure they are being exerted on at redline in the stock engine and then somehow figure out what cfm's or PSI they will withstand.

Hmm, definitely need a mechanical engineer to help with this.

 

I doubt the pressure experienced by forced induction is enough to break the rods. The rods usually break from the destructive forced of detonation, or from the inertial loads from over-revving the engine, or from oil starvation..or some combo thereof.

just my .02

Also, what about the wrist pins, the rod bolts, ring lands..etc....just too many variables..i think.

 

Sharif, thanks for the input...I didn't think about that.

My friend pointed out as well that the rod isn't going to act the same in an engine...

Well, no testing of rods will be done.

We'll see what Tuan can do.

 

We also don't know if these failures are from high or low cycle fatigue. If you stretch or compress the rods you will find out what its max load is before failure but that would be so high it would probably not tell you much. You would probably have to pick a few pressure loads and cycle the part to failure and see the results of load vs cycles to failure........ A lot ofthings to do, more than just trying to find max load.

 

What might be of value is the margins that exist between design limit (failure) and expected load limit under an arbitrary boost of say 8#s or any boost deemed appropriate. Calculating the force (#'s) on the piston head transferred to the rod during the down stroke and assuming that the piston/rod has seized (on the crankshaft) for whatever reason you could compare the margin between design limit (failure) and expected. We would assume that the rod is at an angle of 10 deg after TDC. (max combustion pressure)

Assming stock compression ratio of 9.5:1? and 8lb"s of boost and approx 4x combustion pressure x the area of the piston gives the load on the rod in #'s.

This yields approx 1800#'s. Put the test rod(s) in a compression load device and find out what it fails at and compare it to the 1800.