2000 Lbs of Compression???

[icanfixall]

This is for the real thinkers in math. What I am wondering is what poundage of compression do we have when we add 10 lbs of boost with a turbo. I read somewhere that for each 5 lbs of boost we see 500 lbs of compression added to our running motor. I know in phsyics anything moving has energy and a moving piston sucking in compressed air will make more compression but how much. Is there a formula for this? Thanks math genious's out there. I'm not a smart man when it comes to math..... I can hardly read or write... But I can trach a line....

 

[DeepRoots]

why test compression and do all that math?

we test firing pressure on our engines. Why not do the same?

 

[icanfixall]

Deeproots.... I have no way to get my sidewinder turbo to boost without a load on the motor. Now maybe if I was on a dyno I could make some boost but I don't know how much... Then again what kind of a compression tester would I use??? Most diesel compression testers only go up to 1000 lbs. Thats why I kinda need a mathamaticion that might know of a formula so I could calulate the lbs per boost..... Just something to do on a Thursday nite....

 

[Dsl_Dog_Treat]

Thats why I kinda need a mathamaticion that might know of a formula so I could calulate the lbs per boost..... Just something to do on a Thursday nite....

Gary,
most people round these parts sleep at that time on a Thursday night.
That just makes my head hurt this early in the morning.

I'll betcha Poindexter errr I mean Justin might be able figger that one out.

 

[bbressler]

Here you go...

(actual boost/14.7)
+1
X compression ratio

So -- Let's say you've got 0 boost.

0/14.7=0
+1 = 1
X22 = 22

So, with no boost, you've got a 22:1 ratio. Multiply that by 14.7 to get the psi... 323 psi

Now, let's do 5

5/14.7 = .3401
+1 = 1.3401
x22 = 29.482

5lbs boost = 29.482:1 ratio. times 14.7 = 433 psi

And 10

10/14.7 = .6802
+1 = 1.6802
x22 = 36.966

10lbs boost = 36.966:1 ratio. times 14.7 = 543 psi


So, your 5lbs = 500 psi comparison wasn't a bad one, just off a bit. Looks like 5 lbs = 110 psi on a 6.9.. Now, the original compression ratio makes a difference on the 110 psi deal. My powerstroke has a ratio of 17.5:1, so I only gain 87 psi each 5 lbs of boost. If you had a engine that had a compression ratio of 100:1, you'd achieve 500 psi for each 5 lbs of boost.

 

[icanfixall]

Thats a grat formula but somehow it doesn't fit what I have. My compression is 530 lbs at cranking rpm. So if I follow this formula I would have a much higher compression tatio than 22 to 1. Why is that?? I realize my numbers could be suspect and just what my compression gage is telling me but... Could I have more than this calculation showing a 22 to 1 cr... Could I have 1073 lbs of compression while running?? Thats using my 530 + the formula's 543 = 1073....

 

[bbressler]

the 14.7 is the atmospheric pressure at sea level. at 5000 ft elevation, instead of 14.7, you would use 12.2... I see you're probably pretty close to sea level though, no?

Let's try to go backwards...

530 / 14.7 = 36:1 compression, yowsa!

You wouldn't add the 530 + 543, that 543 includes the baseline...so more likely you might be getting 740 (530 - 323 + 543)..still awfully high.