How Accurate is the Big Boyz Compression Calculator

[hrdtail78]

"Aluminum is about 12x10-6 and steel is about 6x10-6 per degree per inch."

Ok this means that Aluminum grow  6x10-6 per degree per inch more then steel.. Lets assume the top of the piston and the cylinder grow at the same rate.. You got 2 inches of flywheel and 7.7 inches of rod or 9.7 inches..  Ambient is 70 so lets say the motor is 270 gives us a nice 200 F increase..

200 X 6x10-6 X 9.7 = 0.01164

Max

How do I figure ductile iron cylinders into that?

[wfolarry]

I think he did an excellent job no matter how you measure it. 

[Scramjet]

I thought the expansion rate formulas might be close enough to "ballpark" the cylinder expansion.  It seems to me that the cast iron sleeve, steel cylinder studs and head bolt compression would work to constrain the expansion.  It would be my guess that the cylinder expansion is closer to the low side of the estimates relative to the calculated compression - hot.

Hardtail, the expansion rate of iron is similar to steel, about 6x10-6/deg/in.

Max, that looks about right but the heads and tops of the cylinders are hotter.  The rods and crank would stay around oil temperature but the cylinders would be around 300 degrees F.  I would guess a slightly higher number.  Maybe:

Rods=7.667"       Crank throw= 2.1875" (for 4.375 stroke)       Total rod and crank= 9.8545"

Rods and Crank: 240*F x 9.8545" x .000006 = .0102"
Cylinders and Cases: 300*F x 9.8545" x .0000125 = .0369

Calculated expansion hot = .0227"      (Edited)

Remember, "no mathematical model is perfect some some models are useful"

My hat is off to Springer for the spreadsheet.  I have found it very useful.  Thanks Springer.  When you put your work "out there" it is very easy for others to second guess your work.  I appreciate the sharing.

B

[jsachs1]

Big help in my business. 
Thanks,
John

[springer-]

I appreciate the positive comments, Thanks.

I have some updating to do to the calculators, adding some cams to the cam comparator and a few changes to the drive line calculator.  I am open to suggestions that anyone might have for any of the calculators, so please feel free to post them.  Also if anyone has any additional cam specs that I might add, I would appreciate the info.

Thanks

[GoFast.....]

I also use the cam compairing one. Just used it last night, The altitude thing is what I really like because I am at 5600 ft but wonder sometimes how it can be accurate. Also it still seems everyone is all over the place on cylinder expansion, I'm like, well which number do I feel like throwing in there today.

[Admiral Akbar]

"Rods and Crank: 240*F x 9.8545" x .000006 = .0102"
Cylinders and Cases: 300*F x 9.8545" x .0000125 = .0369

Calculated expansion hot = .0227"      (Edited)"

I would probably consider this a worse case difference.. I'd bet that difference between the Rod/ Crank and cylinders cases is less then say 10/20 degrees untill you get to the upper 1/2 of the cylinder. There you could see 50 degrees.  Crank and rods may actually be hotter since the only way they can loose heat is through the oil. Cases/cylinders have outside air..  Heat is energy. It has to flow somewhere. It just don't disappear... (Unless you want to get into a discussion on entropy..  )

Still, notice that the total expansion is limited to 37 thou on the cases and cylinders.. It's a safest worst case..  Maximum

[Scramjet]

Your comment brings to mind the following discussion on heat transfer:

Dr. Schambaugh, of the University of Oklahoma School of Chemical Engineering, Final Exam question for May of 1997. Dr. Schambaugh is known for asking questions such as, "why do airplanes fly?" on his final exams. His one and only final exam question in May 1997 for his Momentum, Heat and Mass Transfer II class was: "Is hell exothermic or endothermic? Support your answer with proof."

Most of the students wrote proofs of their beliefs using Boyle's Law or some variant. One student, however, wrote the following:

"First, We postulate that if souls exist, then they must have some mass. If they do, then a mole of souls can also have a mass. So, at what rate are souls moving into hell and at what rate are souls leaving? I think we can safely assume that once a soul gets to hell, it will not leave.

Therefore, no souls are leaving. As for souls entering hell, let's look at the different religions that exist in the world today. Some of these religions state that if you are not a member of their religion, then you will go to hell. Since there are more than one of these religions and people do not belong to more than one religion, we can project that all people and souls go to hell. With birth and death rates as they are, we can expect the number of souls in hell to increase exponentially.

Now, we look at the rate of change in volume in hell. Boyle's Law states that in order for the temperature and pressure in hell to stay the same, the ratio of the mass of souls and volume needs to stay constant. Two options exist:

If hell is expanding at a slower rate than the rate at which souls enter hell, then the temperature and pressure in hell will increase until all hell breaks loose.  If hell is expanding at a rate faster than the increase of souls in hell, then the temperature and pressure will drop until hell freezes over.

So which is it? If we accept the quote given to me by Theresa Manyan during Freshman year, "that it will be a cold night in hell before I sleep with you" and take into account the fact that I still have NOT succeeded in having sexual relations with her, then Option 2 cannot be true...Thus, hell is exothermic."

The student, Tim Graham, got the only A.

[Admiral Akbar]

 

[fuzznut5197]

Also if anyone has any additional cam specs that I might add, I would appreciate the info.
Thanks

OK 

Can you put the 4 evo Ultima cams on there?

BTW, the S&S 640 is 25/60 not 26/60. I know, typo... 

[skyhook]

bob wood has a couple of new cams that aren't on your calculator...408-44 and 9b-6

[GoFast.....]

Springer could you post your deck height article with the pictures for us here and any other stuff thats helpful

[PanHeadRed]

Springer, I have a suggestion, how bout dropping CCP to whole numbers and CR to a maximum of 2 places to the right of the decimal? CR in fractions (1/4 max resolution) would be even better. 

[springer-]

OK 

Can you put the 4 evo Ultima cams on there?

BTW, the S&S 640 is 25/60 not 26/60. I know, typo... 

Done and done, thanks for the recommendation.

bob wood has a couple of new cams that aren't on your calculator...408-44 and 9b-6

Also done, thanks
I added many cams from Wood and found some of the listed specs on his site seem to be incorrect.  I will contact him to confirm but for time being I used the listed specs.  The cams you mentioned are not the cams in question.

Springer, I have a suggestion, how bout dropping CCP to whole numbers and CR to a maximum of 2 places to the right of the decimal? CR in fractions (1/4 max resolution) would be even better. 

I kept the CCP at 1 decimal place too give indication to what whole number it is closest too.  CR is 2 places now. thanks.  I also changed the CC measurements to 1 place.  Displaying fractions was not an option.


I also made some additional changes based on the discussion about hot compression and cylinder expansion.  This has been a bit of a thorn and as mentioned was only kept for the play factor.  Well it's gone now since it had little or no real use.  I also changed the piston dome volumes.  I have indicated a range of values rather than a value.  As a side note, only actual measured values should be used for accuracy.

Additionally on the Gear Ratio Calculator I added a belt size calculator and added 09 transmission data.

Thanks for all the suggestion and feel free to keep them coming.

[Scramjet]

Don't know that it matters but:

The 2009 SE catalog now shows the stock 2007-2008 EFI cam at 30* intake close.

B

[springer-]

Don't know that it matters but:

The 2009 SE catalog now shows the stock 2007-2008 EFI cam at 30* intake close.

B

Good catch, fixed.  The Cam Comparator had the correct info but the Compression Calculator didn't.  HD specs are one of the hardest to get correct, they publish conflicting information and wrong specs all the time.  When creating the gear ratio and drive line calculator I found most of HD specs on the gear ratios for the 07-08 models to be incorrect.  After theorizing they were wrong we took apart an 07 transmission and counted the teeth on each gear to get the correct information.

Andrews cam specs are all over the place too.  I found up to 3 different cam timing specs for the same cams on Andrews website.  I had to call them to clarify what was correct, it was a mess.

Thanks

[Billy]

springer, thanks for a very useful tool, I use it often. I do notice a discrepancy between the specs you have in the TC compression and displacement calculator and camshaft comparator with the specs for the T-Man 525C he has listed on his website.

http://www.tmanperformance.com/cams.htm
   
   

[GoFast.....]

Springer I think the little changes are great and thanks so much for having something like this, but I disagree with those who say aluminum expansion is not an issue with compression and if they want to put zero on the line thats fine but we have no line now.

[GT]

nice work i like the vin calulcator thing

[ejk_dyna]

<<but I disagree with those who say aluminum expansion is not an issue with compression and if they want to put zero on the line thats fine but we have no line now.>>

no matter what expansion rate you use .040, .020 etc ,the compression calculator calculates a LOWER "hot" compression rate and as a result lower cranking compression hot versus cold.  this value will be wrong 100% of the time because hot cranking compression will be higher than cold 100% of the time because the expansion of the combustion chamber mixture more than offsets the cylinder expansion.

so why is that you feel it is important to input this expansion number?

[springer-]

Billy, thanks.  I corrected that as well added additional Tman cams.  Those correction will be up this weekend.

GoFast..... Too many variables that effect the "hot" compression and really it doesn't have a practical purpose.  I agree with ejk_dyna

GT, thanks.  The VIN Analyzer has been a work in progress for some time.  I just decided to put it out there for some feedback.  Still working on the Twin Cam portion.