Any 6.5 internal dimensions available for mathematical analysis?

[Dylly]

Heres my problem: I have a project in my Dynamics and Vibrations class in which my group was supposed to analyse some type of mechanism and offer suggestions to improve it through calculations... Our initial project, which we thought would be easy was the mechanism in the pump action of a BB gun.. turns out its hard to find specs on these, unless buying one and tearing it apart was an option... only problem is if we tore it apart and later find out there isnt much room for improvement... so we're trying to scrap the idea for something that seems a bit simpler... and the engine topic was brought up, so instead of doing any gasser, i thought i'd look into what was available in regards to information on the 6.5 before jumping to a small block 350 or something.

Our professor basically said we can look at almost anything to do with the rotating assembly in the bottom end for ease in calculation: Crankshaft+connecting rods+pistons ... and if it went further so be it.

So, where might i be able to find information on these components or any 6.5 components...?

My thought was to consider modification to the piston (by shaving)
- see what change in load is transmitted to the bottom end through the connecting rod...
- then perhaps see if the connecting rod dimensions are necessary or if there can be changes in their geometry to support the load...
- then perhaps look at the effects of boost pressure on the bottom end before and after piston shaving etc etc...

The list could go on forever but you get the idea... This would be easy if i had a 6.5 for parts kicking around, but unfortunately i dont...

So, is there any literature available on these engines that would provide the necessary information for calculations?

 

[buddy]

Just knowing the V-angle, bore, stroke, rod length and piston dimensions can get you pretty far. Compression ratio, deck height and stuff may be helpful.

rod length (pin to pin centers): 159.5mm
piston top to bottom of skirt is about 92.7mm
piston top to center of the pin (compression height): 53.8mm

This has some more info in it http://www.v8dieseltech.net/spec/engspec65.htm

I would look at using longer rods with pistons that have shorter compression height (distance from pin to top) That way there is less angle to the rod, more perpendicular force. Or could the block be improved by using a differnt angle itself, the V part. You can calculate the angles the rod has to be at with the piston and the crank journal and see if the force/torque on the crank could be improved with geometry differences. With inline cylinders TDC is when the crank is always straight up, but with the V you have all these opposing angles from one side of the engine to the other.

If you want to go along the lines of shaving pistons and reducing compression height you might consider trying to calculate any benefit from not just shaving the piston, but cupping it, like Kennedy's custom pistons. Does that cupped part help keep combustion forces in the center of the piston and away from rings, does the added surface area of the top of the piston help? Direct injected diesels used cupped pistons as their combustion chamber.

I created an excel spreadsheet to help me understand how differences in IATs, and compression ratio affect compression and heat in the cylinder. If you want a copy PM me your email. It takes any inputs and calcualtes peak pressure and temperature before the power/combustion stroke. A pdf file of it is posted in one of my threads, and you can use it, check my math and improve
http://www.thetruckstop.us/forum/showthread.php?25585-Anatomy-of-EGTs

 

[Dylly]

Thanks Buddy for the angle idea... that would probably be my best bet for this project... I recall looking at some newer diesels... maybe something volkswagon built or some other advanced automaker, and they squeezed the block together with funky angles in regard to crankshaft and connecting rods. My initial assumption was that it was so that they could get the engine to fit in the car, but now that you mentioned this, there is likely more to it that just that since the angle in this particular engine was not 90 degrees, but much less... I'll have to dig up some of that information because angle forces from the connecting rods acting on the crank in different points at the same time could be causing some sort of torque through the crank in unfavorable directions... which could be a factor in cracked blocks, and broken cranks.

Thanks again. Great information.

 

[sparky18]

Hey Dylly,I have a 6.2 with a broken crank in it over here in Semans that you can have if ya wish.

Maybe you can tell me why the crank broke in the first place,lol.

Let me know if ya want it.



Mark

 

[WarWagon]

All you have to do is look at a 6.2 Diesel and what GM did to make the 6.5 Diesel.
Bored out the 6.2 to 6.5 and reduced piston thickness to keep the rotating weight the same.

Same crankshaft for 6.2/6.5 in the 1 piece rear main years...

Then you can do vibration analysis of the different compression ratios and end it with the common failure of the vibration damper resulting in a busted crank and scrap metal engine.

Or do an analysis of the lighter 6.5 piston vs. the 6.2 piston and see what one lasts longer, in revolutions, with a failed/worn out injector before melting... See if the ceramic coating helps... Hint: the pistons liquefy first in the area without the coating... (Outer diameter)

 

[Dylly]

Hey Dylly,I have a 6.2 with a broken crank in it over here in Semans that you can have if ya wish.

Maybe you can tell me why the crank broke in the first place,lol.

Let me know if ya want it.



Mark

That would be wickid man, i just have to find time to get out there... I'll have to keep in touch on it because 6 classes a semester is ridiculous, i feel like a 4 hour round trip (from saskatoon) could be a problem academically.

 

[WarWagon]

I think you would have a better challenge with a V-6 than a V-8. An Olds 4.3L V-6 diesel would be fun (!)

V-8 engine have power pulses that are continuous. Look up odd-fire V-6 engines... "Firing intervals alternating between 90° and 150°" "power delivery shows large harmonic vibrations that have been known to destroy the dynamometer"

http://en.wikipedia.org/wiki/V6_engine

 

[Dylly]

All you have to do is look at a 6.2 Diesel and what GM did to make the 6.5 Diesel.
Bored out the 6.2 to 6.5 and reduced piston thickness to keep the rotating weight the same.

Same crankshaft for 6.2/6.5 in the 1 piece rear main years...

Then you can do vibration analysis of the different compression ratios and end it with the common failure of the vibration damper resulting in a busted crank and scrap metal engine.

Thats a good idea, i need to keep this on the simple side then branch off from there... so i'll see what my professor thinks of these ideas and if it gets the ok, ill see what he thinks the best option would be as a starting point

 

[buddy]

Yes, as WW said, you could mathematically and scientifically explain exactly why the harmonic balancer is so important on the 6.5

 

[sparky18]

That would be wickid man, i just have to find time to get out there... I'll have to keep in touch on it because 6 classes a semester is ridiculous, i feel like a 4 hour round trip (from saskatoon) could be a problem academically.

only bad part is that i work out in alberta,so setting it up will take more work then ya think,lol.i'll keep ya posted any time i get home though for sure.

 

[Dylly]

Yes, as WW said, you could mathematically and scientifically explain exactly why the harmonic balancer is so important on the 6.5

In your professional opinion Buddy, how much would you say would be a safe ammount to grind down these pistons? I dont have one here to look at and decide what would be reasonable.

 

[WarWagon]

Nothing can be removed from these pistons safely. It is a known fact that the 6.2 pistons are stronger then the 6.5 ones. Ceramic coating a 6.2 piston would be the strongest.

Some people do thin them out for 18:1 compression.

Start with a 130 HP 6.2 NA diesel.
Bore it out to 6.5 and thin the piston crown to keep the reciprocating weight the same.
Bump the HP up to 200 HP with a turbo.
Still at high compression.

Add ceramic coating to help the pistons out.
Hmmm... not enough... Add oil cooling to help the pistons out. In fact Bean Counter GM went through the trouble and cost of adding a High volume oil pump and additional expensive tooling and additional production time to add oil squirts to the blocks. GM spent money on this so you know there were issues with the factory thickness and high compression. GM would not have spent 10 cents on it otherwise. Warranty claims in the 3/36 had to make doing this cost effective. Or was it in the 100K warranty diesels came out with at some point I forget. Cept for the tooling clipping and cracked blocks that may have failed in the warranty.

Have another company redesign the engine from the ground up for reliability. They did not thin out the pistons...

 

[buddy]

I'm no professional, but I kind of a agree that cutting anything off the piston can be bad, but doesnt mean I wouldnt do it. Its a good idea to keep that anodized surface in tact as it helps prevent wear and increases hardness, and also will help a coating adhere.

There are already factory ones made with 0.01" shorter compression height (factory cut pistons with the anodized surface). I also intend to cut a good amout into a set, about 0.06" and ceramic coat it. Although I would not cut that much off all around, because it would significantly reduce the ring height. You can see what Kennedy does with his lower compression pistons, he extends and deepens the swirl cups. That is not what I plan to do but similar.

 

[Dylly]

I'm no professional, but I kind of a agree that cutting anything off the piston can be bad, but doesnt mean I wouldnt do it. Its a good idea to keep that anodized surface in tact as it helps prevent wear and increases hardness, and also will help a coating adhere.

There are already factory ones made with 0.01" shorter compression height (factory cut pistons with the anodized surface). I also intend to cut a good amout into a set, about 0.06" and ceramic coat it. Although I would not cut that much off all around, because it would significantly reduce the ring height. You can see what Kennedy does with his lower compression pistons, he extends and deepens the swirl cups. That is not what I plan to do but similar.

Makes sense, In that case, since im doing the rod extension version, how far up could i move the pin in the piston (compression height)...?

I know its not a practical modification as it would require a complete new piston, but for the mathematical analysis stand point i can at least find out if its worth doing... BUT i dont know how high/ how much room there is underneath to move the pin up to decrease compression height, and then increase rod length to get the same compression ratio as stock.

So, how far could i potentially move the pin up into the piston? (in a perfect world)

 

[WarWagon]

You can't hardly get a piece of busted piston between the bottom of the piston and the rod top. The pistons come up to the top of the block. The square top of the rod appears to have something to do with oiling the pin?

Any material removed puts the top ring land closer to the crown and higher heat, sticking issues, etc.

It would be interesting to work out vibration from 18:1 vs. 21:1 compression as far as cracking the block would be concerned.

 

[buddy]

Since you are in theoretical education land, I would do something extreme, like go down to two rings, where the compression ring is also a oil scraper and since the rods would be custom too you can make the pins smaller. So maybe cutting an arbitrary 10mm off the pistons and 3mm off the pin radius or something like that would give you a big enough difference in rod angle to get a better torque angle. Basically, you always have to use math and physics to justify trying something new.

Essentially you should be able to tell us at what crank degree does the piston/rod have the most torque on the crank. Then recalculate that for the longer rod setup, and also if the torque is greater over more degrees. So you could involve some calculus possibly where you would integrate the torque over several degrees of the compression stroke.

 

[Ratman]

You can't hardly get a piece of busted piston between the bottom of the piston and the rod top. The pistons come up to the top of the block. The square top of the rod appears to have something to do with oiling the pin?

Any material removed puts the top ring land closer to the crown and higher heat, sticking issues, etc.

It would be interesting to work out vibration from 18:1 vs. 21:1 compression as far as cracking the block would be concerned.

There is only .032" difference in compression-height when going from 21:1 to 18:1 CR.