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Discussion Starter · #1 ·
I know all to well from personal experience the "joys" of dealing with a cracked cylinder sleeve on a stock R engine. My engine and vehicle was completely stock at that point. My car had roughly 117,000 miles on the odometer around the time when I started encountering misfiring issues and a slow coolant loss. After an initial miss-directed diagnosis I eventually replaced my engine with a lower mileage (74,000 miles) R engine from a totaled 2007 S60 R.

I have been thinking of trying to put together an evaluation of the fatigue strength of the R engine cylinder walls based on real world data. As an aerospace engineer specifically working in the fatigue and fracture analysis and evaluation of rotor craft parts this should be right up my alley. My engine is one datapoint, however it would be beneficial to have a greater population of data. If your engine has ever suffered a fracture of the cylinder sleeves please chime in and add to this thread. I want to know mileage at which it occurred and if the engine was being run in the stock configuration or with a tune and any additional modifications. Also if your vehicle was tuned and running various engine modifications that potentially produced higher boost pressures, please explain at what mileage those were added.

Another bit of information I will need help on is determining how many cycles of compression and combustion are accrued per mile driven. I am thinking an average RPM of 3000 is good place to start for most driving. If anyone can add to that or knows better how to approach this let me know. By the end of this I hope to put together a mean strength demonstration for our engines with an expected life based on real world data.
 

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I had one bad crack and one minor one by 160K miles when I tore down my motor, but neither were leaking yet interestingly enough.

One reason that might have been the case is I had put some alumiseal in the coolant system from when I had a small water leak before the 100K mile point. I wonder if that being in the cooling system was effective enough to keep them clogged so it never became a serious issue.

I have a tune and some other mods, so I was often pushing around 20 psi of boost since around 60K miles.
 

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Discussion Starter · #3 ·
So Stealthy you never experienced miss-firing during startup from coolant entering the combustion chamber or white smoke out the tail pipe? Your engine might have to be a reference point in the data population without a clear indication of when the crack occurred. Do you have pictures? Did it look like the crack had propagated far with the bad one?
 

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I might have to try the Alumiseal
 

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Never had a misfire not related to a bad coil. Always started up perfectly on the first cylinder to kick.

I did at one point around the 100K point did have an issue with it blowing coolant out of the cap. Replaced the cap and all appeared to be well again. Perhaps it was one of my cracks opening up and then the leftover alumiseal flowing around clogged it before it could get into the cylinder and which also then blocked any exhaust gasses from leaking back the other way.

Here are some pics of the crack, as you can see from the ringlands the bad crack was reducing cylinder pressure past the rings so that might have helped keep it from leaking too . . .

Minor Crack:


Major Crack:
 

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I'd like to quote something my shop foreman said, which was along the lines of "We rarely, if ever, saw cracked blocks in these engines. Then some of these new "tuners" came along who hadn't been working with Volvos as long as the old ones had, and started cutting corners in the name of making power. Now we're just waiting for the whole R line to go extinct."

Volvo designed these cars with quite possibly what was near to the safe limit of power out of these blocks in mind. We're pushing them too hard, and we're paying the price. I'm not making excuses for poor design decisions, but it is what it is.
 

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I'd like to quote something my shop foreman said, which was along the lines of "We rarely, if ever, saw cracked blocks in these engines. Then some of these new "tuners" came along who hadn't been working with Volvos as long as the old ones had, and started cutting corners in the name of making power. Now we're just waiting for the whole R line to go extinct."

Volvo designed these cars with quite possibly what was near to the safe limit of power out of these blocks in mind. We're pushing them too hard, and we're paying the price. I'm not making excuses for poor design decisions, but it is what it is.
The issue is a lot of these cars were on the stock tune and still cracking blocks... And stress-wise there doesn't seem to be a bias towards MT vs GT R engines failing. Given the GT cars don't lose boost when shifting they endure less stress because boost isn't building and falling. With that fact one would expect a bias towards MT cars failing faster. It's a poor design plain and simple. It's not a question of if, it's a question of when (except for maybe those 04 cars that are limited to 10psi for some reason)...
 

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Even among the stock cars, I assume the ones with cracked blocks were driven harder than those who didn't crack. We've had a few members make it over 200K miles without cracking, so it appears the stock HP does reduce the risk quite a bit. Plus we don't know how many of the stock cars might have had ****ty tunes that were flashed back to stock before they were resold since a few of the busted stock Rs were not in the hands of the original owners.
 

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For turbo charged cars it is Volvo corp. fault for not using thicker walled sleeves especially in R line..."absolutely dumb!" and that's as far as you will get... but , i seen plenty of 81mm bore distorted before shimming when I ran a feeler gauge through those cuts between the sleeves...now by thicker I mean thicker than 81mm bore and there would not be a discussion about this at all, buuuut they actually bored them out to 83mm making them waaaay to thin and weak even for stock unmodified caRs...and they know it ... but you can dance around it pretty much by saying what stealthy said above (edit) and below. :D case closed.
 

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Few cracked during warranty period, that's all volvo corp needed to be concerned with, lol.

In reality though, how many thousands of Rs are out there and how many cracked blocks are there? Chances are high this might be a failure down in the 1% or less range, and lots of cars die for lots of reasons more likely than this one.

Hell, a bad thrust bearing in my turbo killed my engine, but you don't see me bitching about how B-W designed the K24's thrust bearing because its a pretty hardy turbo despite its minor flaws.
 

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My R has 263k kms (160k miles) and is starting to eat coolant. No wet carpets, no leaks, just coolant loss.

Car is completely stock. From what I can tell, it was dealer serviced and lady driven until I bought it at 230k kms (138k miles). My wife drives the car more than I do and certainly is easier on it than me.

Luckily I have a couple low k motors on hand.
 

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Discussion Starter · #13 ·
After doing a quick back of the envelope evaluation, the cylinder sleeve fracture mode of the R engines is likely not related to a high cycle (N/Rev) event such as boost pressure and compression in the cylinder chamber but rather a low cycle event of start-stop relating to the thermal cycling of the engine block. Simply the number of cycles compression accumulated by 100,000 miles would be out beyond the 10^8 high cycle region where the material property fatigue curve for steel is nearly flat.

I would need the maximum temperature during spirited driving that the engine block gets up due during operation and an assumption of the number of start-stop cycles our engines go through per hour's of operation. Is there way to get hours on our engines and engine block temperature from VIDA? Any idea what a good estimate of average trips would be for our cars?
 

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After doing a quick back of the envelope evaluation, the cylinder sleeve fracture mode of the R engines is likely not related to a high cycle (N/Rev) event such as boost pressure and compression in the cylinder chamber but rather a low cycle event of start-stop relating to the thermal cycling of the engine block. Simply the number of cycles compression accumulated by 100,000 miles would be out beyond the 10^8 high cycle region where the material property fatigue curve for steel is nearly flat.

I would need the maximum temperature during spirited driving that the engine block gets up due during operation and an assumption of the number of start-stop cycles our engines go through per hour's of operation. Is there way to get hours on our engines and engine block temperature from VIDA? Any idea what a good estimate of average trips would be for our cars?
The CEM stores a global time but I'm not sure when that starts--i.e. at startup or just key on. An acceptable approximation would be total miles/average speed there would obviously be some error but it's a least a decent first approximation in most cases. However, given my average speed in my R is less than 40mph and it has 289k... I don't think that works because it returns about 7300 hours. A large amount of highway driving will raise the average speed.
 

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Discussion Starter · #15 ·
During an average week of commuting to work and weekend driving, my average speed has been around 37 mph therefore my estimated hours on the engine would be 3,162 hours and with an average trip duration of 0.5 hours that's a total of 6,324 start-stop cycles. However as you mentioned there are plenty of longer trips beyond my "standard week" with large durations of highway driving and with my car I can only account the driving and usage during the last 53,000 miles on the engine.

A check against what the CEM reads would be great to verify how close these approximations are. Hound, do you have VIDA and would you want to get together and see how far our estimates deviate from what has been recorded by our vehicles?
 

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During an average week of commuting to work and weekend driving, my average speed has been around 37 mph therefore my estimated hours on the engine would be 3,162 hours and with an average trip duration of 0.5 hours that's a total of 6,324 start-stop cycles. However as you mentioned there are plenty of longer trips beyond my "standard week" with large durations of highway driving and with my car I can only account the driving and usage during the last 53,000 miles on the engine.

A check against what the CEM reads would be great to verify how close these approximations are. Hound, do you have VIDA and would you want to get together and see how far our estimates deviate from what has been recorded by our vehicles?
I do have VIDA. Let me see what I'm doing and I'll get back to you... The R is currently in several piece with the ETM sitting in front of me...
 

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If this was my fatigue analysis I would focus on the stress riser created by the cut when cylinder pressure is being exerted on the cylinder walls. More boost and more WOT time means more stress, so those higher stresses will certainly matter more than the low stresses the engine sees most of the time.

Its easy to reach a quarter million miles when most of your time is spent putting around or cruising down the interstate.
 

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If this was my fatigue analysis I would focus on the stress riser created by the cut when cylinder pressure is being exerted on the cylinder walls. More boost and more WOT time means more stress, so those higher stresses will certainly matter more than the low stresses the engine sees most of the time.

Its easy to reach a quarter million miles when most of your time is spent putting around or cruising down the interstate.
Theoretically it should be possible to calculate the force on the cylinder wall knowing a fuel charge for 5500RPM. Just need to know how much the fuel charge is expanding after ignition. Max force should be at TDC the moment before the piston is shoved on its down stroke.
 

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Isn't this an AL block? You mentioned the 10^8 fatigue cycling of steel.

I am not a ME, but here is my take.

It seems variable. I wonder how the relief cut is made. What sort of tool it is, and if it could leave striations on the metal in the cut surface. That might contribute to stress risers forming there.

If you look at Stealthy's picture closely, you can see that the crack isn't exactly on-center in the bore wall. It should be if it is entirely wall thickness based.
 
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