Engine build update Bad news

Quoting BarnesMobile:
Quoting galant1517:
Barnesmobile, I unfortunately have to say you are incorrect sir. After doing the math, here are my results.




You're own math confirms what I said. You showed that reducing the dish volume increases compression ratio linearly. I even plotted a graph of your data. It's a linear relationship. I could even write a mathematical proof if need be.



After having re-read exactly what I said, and re-reading exactly what you said, I fail to see how.

Mitsuturbo said:
Quote:
3cc difference = +.5 CR difference



While this may be true when starting with a particular CR, it isn't true when starting with any CR.

Let's exaggerate this a bit. If it were possible to have our engine with a piston dish that was 200 cc, making the dish 197cc would effectively change nothing. The increase in CR would be unnoticeable. Same goes for the other end of the spectrum. If we could have a dome that left only 6cc of combustion volume at TDC, adding 3cc to the dome would leave only 3cc of combustion volume left, doubling the CR. These increases occur on a curve. Either that or one of us needs figure what linear means.

 

[Barnes]

From what you have written, and some assumptions, I'm guessing what you mean by 'curve' is that changing combustion chamber and/or piston dome/dish volume affects compression ratio non-linearly. That is, if you plotted compression ratio vs. combustion chamber volume/piston dom or dish, the graph would show a curved line. I am saying this line would be straight. I will generate some graphs tomorrow. And if you are not persaded by that, I'll gladly write a proof.

 

[Muskrat]

Quoting Drdamm21:
The cover is off and the starter is removed the tranny is off the pins large pins that stick out of the block as well .... So I dont know ? I will have a friend of mine come over and help me also im gonna post some pics just incase



Have you tried using a pry-bar between the block and transmission? Or are you just trying to pull it off by hand?

 

[DR1665]

Hey Barnes and Galant1517 - How is your in-depth debate on relational compression physics A) valuable to the guy who can't seem to separate his engine from his transmission and B) contributing to useful search results in the future? Any chance you could take this - truly - valuable debate to a new thread and leave this one for helping the new guy solve the problem at hand?

Thank you,

Brian

 

[Barnes]

Quoting BarnesMobile:
From what you have written, and some assumptions, I'm guessing what you mean by 'curve' is that changing combustion chamber and/or piston dome/dish volume affects compression ratio non-linearly. That is, if you plotted compression ratio vs. combustion chamber volume/piston dom or dish, the graph would show a curved line. I am saying this line would be straight. I will generate some graphs tomorrow. And if you are not persaded by that, I'll gladly write a proof.



Awesome. I get to eat my words. I was totally wrong. I think the reason I thought it was linear was because when you look at the curve by the time you get to practical combustion chamber & piston dish/dome it looks linear. I chalked up any inconsistency to rounding. I realized my algebra might be bad, and plotted the whole thing, and low and behold compression ratio as a function of increasing final combustion volume is an exponentially decaying function. Now to go back and figure out how the algebra works. I'll probably do that while I'm enjoying my nice plate of crow.

 

[cheekychimp]

At least you are man enough to admit you are wrong. There are a lot of people on here who are not. Whatever you find out, post it up. The math on this is clearly very very complicated and very few understand it which is more than likely why most of us can't pick the best CR for the boost pressure we want to run.

I want to run about 18 psi when I'm all said and done with my daily driver but because it is daily driver I'd like to run as much compression as I can to get off boost driveability. If I can get away with 9.0:1 I would probably do that as I can just purchase EVO III OEM pistons and be done with it. However if forged pistons would allow me to run a 10.0:1 compression that might be a better option, or if 18 psi on a 9.0:1 CR is going to cause detonation issues I might need to look at straight 2G pistons or EVO 9 pistons to bring the CR down to 8.8:1 or even 8.5:1. The math on this is far, far beyond me and I'd really appreciate some help.

 

Quoting DR1665:
Hey Barnes and Galant1517 - How is your in-depth debate on relational compression physics A) valuable to the guy who can't seem to separate his engine from his transmission and B) contributing to useful search results in the future? Any chance you could take this - truly - valuable debate to a new thread and leave this one for helping the new guy solve the problem at hand?

Thank you,

Brian



Brian, you are absolutely right. While Drdamm21 originally posted a query that is very much relevant to the debate that Barnes and myself are involved in, HE changed the direction of HIS thread, and we should have changed with it. Or, on second thought, maybe we shouldn't have. because separating the engine from the transmission has nothing to do with "Engine Build and Power". Maybe Drdamm21 should've started a new thread, with a title more appropriate to his current situation. It seems that if you're looking to preserve accurate search results, and Drdamm21 would like to have the people who might know something about separating an engine from a transmission actually view his thread, the more appropriate action would have been to request a new thread be started on that front, not this one.

Barnesmobile, +100 respect points. It takes a lot to admit one's mistake, and a lot more to do so as openly as you have. Kudos. I must admit, you had me going back and double and triple checking my math, because you are very seldom wrong, far less often than myself.

Moderators, I can see where Brian D is coming from. If you'd feel so inclined, I feel that it would be appropriate to separate the "Debate on relational compression physics" from the rest of this thread...in this interest of preserving accurate search results.

 

Quoting cheekychimp:
At least you are man enough to admit you are wrong. There are a lot of people on here who are not. Whatever you find out, post it up. The math on this is clearly very very complicated and very few understand it which is more than likely why most of us can't pick the best CR for the boost pressure we want to run.

I want to run about 18 psi when I'm all said and done with my daily driver but because it is daily driver I'd like to run as much compression as I can to get off boost driveability. If I can get away with 9.0:1 I would probably do that as I can just purchase EVO III OEM pistons and be done with it. However if forged pistons would allow me to run a 10.0:1 compression that might be a better option, or if 18 psi on a 9.0:1 CR is going to cause detonation issues I might need to look at straight 2G pistons or EVO 9 pistons to bring the CR down to 8.8:1 or even 8.5:1. The math on this is far, far beyond me and I'd really appreciate some help.



Cheeky, I wish that I was more experienced in preparing engines for a particular purpose. The mechanical basics come easily to me, however the tuning aspect often leaves me confused. And truth be told, I've only ever assembled one engine from individual pieces to running and driving. I can tell you the how and why on any aspect of the rebuilding process, and I can confidently tell you that, despite my inexperience, I can assemble your engine properly. I cannot, however, tell you how the computer will interpret the changes or how well a particular setup will match your desired outcome. For that, I apologize.

 

Barnes, I have given this a great deal of thought, and although I do not have the time to verify it, I believe that if you wanted to plot a linear graph showing compression, the changes would have to be percentage based.

For example, we'll start with a total combustion volume of 100cc.

If you were to remove 10%of the volume, leaving 90cc, this will give you X increase in CR.

Remove 10% from 90cc, leaving 81cc, and your increase in CR should still be X.

Remove another 10%, leaving 72.9cc, resulting again in X increase of CR.

I have not confirmed this yet though.

 

[Muskrat]

The compression discussion is definitely a good one, but you might be better served summarizing what's already been posted, and starting a new thread in the Technical Discussion section of the forum.

 

No I have not tried a pry bar as its aluminum and I dont want to break it . I will post when it gets seperated thanks everyone for the help! /ubbthreads/images/graemlins/worthy.gif

 

I meant no harm by posting addl. Qs on my problems but per previouse messages I have been told to not keep posting new threads . I figure if I have alot of experts in one room why go to another room. Thanks again to all

 

[Barnes]

Take a two-by-four and saw it down into some wedges. Place them all around the block/tranny and slowly pry it apart that way.

 

[Muskrat]

Def. try a pry-bar or what barnes said.

You wont hurt anything, unless you're really cranking on it. And if you have to do that something else is wrong.

My bet is you just need a little bit of leverage to get it going.

 

This is a great idea thanks again I will use the wedge

 

[mitsuturbo]

Get the diff lower than the rest of the transmission. Make SURE you pulled the 5 bolt gusset out from under the pass side axle area!

 

[Muskrat]

^^ If I'm not mistaken, I think he already has the engine/trans out of the car.

 

[mitsuturbo]

Quoting Drdamm21:
No I have not tried a pry bar as its aluminum and I dont want to break it . I will post when it gets seperated thanks everyone for the help! /ubbthreads/images/graemlins/worthy.gif



Not according to this post.

 

[Muskrat]

Quoting Drdamm21:
The engine is out but the damn tranny just will not seperate I guess just brute force then /ubbthreads/images/graemlins/mad.gif



/ubbthreads/images/graemlins/wink.gif

 

[mitsuturbo]

Let's play a little game called "follow the conversation".
If you look at entries in this thread just a few before your own, one with a bit of good sense could glean that the transmission is NOT in fact, out of the engine bay yet.