Hussein's 1998 V70 Xr : The Force Awakens

[Boxman]

Taking into account both the longer conrods (relieving pressure) and the shortskirts (increasing pressure), the net pressure increase with his setup was 22% over regular conrods + skirt length. Not orders of magnitude more, but still significant additional pressure, which may have just pushed it over the edge of what it could sustain long-term. Especially when combined with possibly increased piston rocking.

Edited September 25, 2015 by Boxman

[blkaplan]

Taking into account both the longer conrods (relieving pressure) and the shortskirts (increasing pressure), the net pressure increase with his setup was 22% over regular conrods + skirt length. Not orders of magnitude more, but still significant additional pressure, which may have just pushed it over the edge of what it could sustain long-term. Especially when combined with possibly increased piston rocking.

How did you calculate this?   

 

 

 

 

[Boxman]

How did you calculate this?   

Like this a while back.

Edited September 25, 2015 by Boxman

[andyb5]

Like this a while back.

Is there a reason you calculated the forces at the middle of the stroke, where forces are minimal, and not near the top of the stroke when forces are highest? 

[Boxman]

 

Is there a reason you calculated the forces at the middle of the stroke, where forces are minimal, and not near the top of the stroke when forces are highest? 

Actually the horizontal force is minimal at the top of the stroke, as there is no horizontal component at all then (ideally). As α -> 0 at TDC, so does N_{R_|_}

At small angles (near TDC) the relieving effect of the longer rods tops out at ~5.4%, resulting in (combined with short-skirt increased pressure) overall 21.6% increased pressure over stock. The actual maximum sideways force should be somewhere between 25%-50% of the combustion stroke, as it's a trade-off between the increasing sideways force due to increasing α, and the decreasing pressure as the stroke continues. But this would take some more time to figure out exactly - bottom line is the overall pressure increase is a pretty constant (22.0 ± 0.5)% across the entire stroke.

Edited September 26, 2015 by Boxman

[lookforjoe]

Those are the only things I can really think of as well.   It either was contacting something.... unlikely if there weren't marks found anywhere...  or perhaps the clearances were off and it was allowing the piston to rock in the bore.        Or..... the skirts of the pistons were too short for the rod length and stroke and it was side loading the piston excessively.    With the longer rod it tends to reduce the side loading but the skirts on these are shorter from what i know.   

I never measured them relative to stock Volvo Short skirt pistons. I assumed them were the same length. Perhaps not.

I touched base with my Wiseco contact:

 

Hi Trent,

 The skirt breaking off like that is really strange.

Excessive piston to cylinder wall clearance could cause that. The piston would be rocking in the cylinder.

If the piston came into contact with something, that could also cause the skirt to break off.

If you’d like to send them to us, Harvey here could take a look at them. We could send them down to the lab at the factory for review.

Best regards,

Adam Silverthorn

PMI Canada / Wiseco Piston Canada

Nice!

I'll check with the machine shop. If he did;t get anything concrete from his contact, I'll send them up. I'd like to know why.

[blkaplan]

I talked to a couple other people about it,  their response was that they thought the piston was loose in the bore ( bore was oversized for the piston)  allowing it rock excessively which led to the fatigue failure.

Edited September 27, 2015 by blkaplan

[dougy]

???how many miles with these pistons???

[lookforjoe]

???how many miles with these pistons???

I posted that previously, Doug

40K miles on the build.

 

[German850R]

I posted that previously, Doug

40K miles on the build.

 

Is it just me who thinks that 40k miles or 60k km on a build like that which went through a lot of tuning iterations and certainly some level of abuse is actually quite OK?

[dougy]

I posted that previously, Doug

40K miles on the build.

 

oh ok i missed it, thanks. 

Is it just me who thinks that 40k miles or 60k km on a build like that which went through a lot of tuning iterations and certainly some level of abuse is actually quite OK?

kinda yes and no...one would think/hope not that type of damage, but with 40k miles of high-output  HP of wear and tear it is certainly is very possible to wear the cylinder walls to give it that rocking that could to produce those pistons cracks...still, for the money you pay for those that's poor in my opinion. 

[EricF]

oh ok i missed it, thanks. 

kinda yes and no...one would think/hope not that type of damage, but with 40k miles of high-output  HP of wear and tear it is certainly is very possible to wear the cylinder walls to give it that rocking that could to produce those pistons cracks...still, for the money you pay for those that's poor in my opinion. 

I agree.  If it were residual damage resultant from detonation in the process of tuning or something, that would be more understandable.  But if in fact the break is due to cylinder liner wear, I don't know that the wear would be that accelerated with say an average of double the stock output.

I also put 40k on a car in a year sometimes, so for me it's hard to imagine a properly conceived and clearanced setup like that to just reach end of life at that type of mileage.

 

[German850R]

I agree.  If it were residual damage resultant from detonation in the process of tuning or something, that would be more understandable.  But if in fact the break is due to cylinder liner wear, I don't know that the wear would be that accelerated with say an average of double the stock output.

I also put 40k on a car in a year sometimes, so for me it's hard to imagine a properly conceived and clearanced setup like that to just reach end of life at that type of mileage.

 

Maybe I have a German view on it. Our cars see a significantly higher load collective due to our (few remaining) limit-free motorways. So, for us a car with twice the original power output reaching more than say 50000km with a certain setup is quite uncommon. Of course, there are cars which last longer than that, but that would be the exception.

[venderbroeck]

I definately have to try to finish my build before those limitless motorways cease to exist 0o.

[German850R]

I definately have to try to finish my build before those limitless motorways cease to exist 0o.

Sure, helps tuning a lot ;). I can offer you a place to stay as a "road tuning base" with great access to good motorways ;). From our new place we have 3 great motorways within 10min of driving