928 Block Thoughts
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Originally Posted by GregBBRD
The engineers at Porsche who couldn't make it work will be interested.
greg brown
greg brown
TWO people are doing this, in totally separate places in this country.
Your shadenfreude is showing.
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From: Anaheim
Brendan:
Again, sorry. Didn't think I needed to tip toe around in this forum. Seems like people pretty much say what's on their minds. I'm just honestly trying to find out if this works and if anyone has a running engine with sleeves in them. I see a few of these engines and I'm always trying to see if there is something new out there that I wasn't aware of. And by the way, you'll know when my shadenfreude is showing.
greg brown
Again, sorry. Didn't think I needed to tip toe around in this forum. Seems like people pretty much say what's on their minds. I'm just honestly trying to find out if this works and if anyone has a running engine with sleeves in them. I see a few of these engines and I'm always trying to see if there is something new out there that I wasn't aware of. And by the way, you'll know when my shadenfreude is showing.
greg brown
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Greg, Heres a link to Todd's build up in cheeseville. I don't know anything about it other than what has been posted. He is still building it I believe. http://www.erik27.com/todd/
Check some of Hackers old posts. Todd may have built a smaller one in the past but I'm really not sure. Good luck in your quest.
Check some of Hackers old posts. Todd may have built a smaller one in the past but I'm really not sure. Good luck in your quest.
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Originally Posted by BrendanC
TWO people are doing this, in totally separate places in this country.
If as Jim Bailey said, Porsche was making 650hp with those 944GTR engines that Greg says required a different block material because of the cracking problem, is this really going to be an issue unless someone's trying to make 1,300hp with a 928 engine?
From information in this thread, the cracking Porsche experienced was in 944 blocks, which have shallower water jackets, and as a result I'd guess thicker material in the area that the cracking occurred in if I'm picturing this correctly. If the 928 block has deeper water jackets, and thinner material in that area, it would seem that the high power 104mm alusil bore 928 engines would start to get to be more suseptible. Have there been any problems with any of the stroker motor 928 engines experiencing the cracking? Seems like they could be kind of a first indication of whether it's going to be a problem.
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Greg if your offending anyone it would be the engine builders. If they were offended they can talk for themselves, since they are very knowledgeable about what they are doing. Too many times people want to talk for others on this forum. Since Todd and Swaybar is it? "ARE" building and doing their engine builds, they are confident in what they are doing and that their approach is sound. Hopefully it will be a new proven way for HP for us.
Besides your right people do talk their minds when ever they choose on this forum, hope there's no more Judge Judy Shows on the 928 forums again. Just a waste of time.
Maybe you have a point, Porsche might be interested. Maybe Todd and sway can teach the P-engineers a thing or two. If not, at least they are making great strides in the engine building for our sharks.
Cheers to all the knowledgeable engine builders out there.
Besides your right people do talk their minds when ever they choose on this forum, hope there's no more Judge Judy Shows on the 928 forums again. Just a waste of time.
Maybe you have a point, Porsche might be interested. Maybe Todd and sway can teach the P-engineers a thing or two. If not, at least they are making great strides in the engine building for our sharks.
Cheers to all the knowledgeable engine builders out there.
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I've seen two cracked blocks in stroker engine applications. One with many hours and one with very few hours. The one with many hours had cracks in three of the five main bearings. The cracks run up into the cylinders, through the thickest part of the casting. All of the blocks that I've seen that have the spun thrust bearing problem crack in exactly the same place, in the same direction.
This is the same failure that Porsche had when they removed the cylinders from the 944 GTRs, before they redesigned the block and changed the material. The early 944 GTRs only made about 450hp. They had many, many problems with these engines in the development phase.
Both of the stroker engines with cracked blocks made over 500hp. One had a six counterweight Moldex crank and the other had an eight counterweight Scat crank.
I have seen no failures in stroker engines with less output.
greg brown
This is the same failure that Porsche had when they removed the cylinders from the 944 GTRs, before they redesigned the block and changed the material. The early 944 GTRs only made about 450hp. They had many, many problems with these engines in the development phase.
Both of the stroker engines with cracked blocks made over 500hp. One had a six counterweight Moldex crank and the other had an eight counterweight Scat crank.
I have seen no failures in stroker engines with less output.
greg brown
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Stan:
Bored to 104mm. Cylinders did not crack 1st and did not crack more than halfway up. The cracks originated from the main bearing area. One was Alusil and the other was Nicosil.
Bored to 104mm. Cylinders did not crack 1st and did not crack more than halfway up. The cracks originated from the main bearing area. One was Alusil and the other was Nicosil.
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From: Helsinki, Finland
Originally Posted by 123
From information in this thread, the cracking Porsche experienced was in 944 blocks, which have shallower water jackets, and as a result I'd guess thicker material in the area that the cracking occurred in if I'm picturing this correctly.
Code:
928 | | | | _| |_ 944 | | _| |_ | |
Racer
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From: Berkshire. 'Old' England. U.K.
Originally Posted by GregBBRD
All of the blocks that I've seen that have the spun thrust bearing problem crack in exactly the same place, in the same direction.
Great thread
Martin
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So what has to be done to a 928 block to ensure reliability at high power levels? If the blocks crack at a certain power level, keeping the stock bore in place is probably going to have no effect, keeping the power level low is no way to live either. Let's discuss methods of strengthening the 928 block! Here are some random thoughts:
The bottom end has huge forces applied to it from rotational inertia and downward piston forces from power and detonation. IMHO detonation is often ignored but always winds up happening at some point and you might as well plan on it. I don't know what the consensus is on it's effect to the bottom end but I've seen American V8 engines where the 4 bolt main cap is split, that happens from some serious pressure in the direction away from the piston whether it was caused by normal forces or not, it happens as well as cap walk when the forces against the main bearing are greater than the clamping force of the cap bolts. So there are huge forces acting on the crank, how do they effect the block? What are the bottom end studs doing, are they transferring forces to a bad place? What force propogates the cracks in the first place? Is it those 'downward' forces acting through the studs etc or is the crankshaft whipping about and generating many small stress cycles instead of catostrophic big ones? Do the cracks happens gradually or are they sudden?
Ah...the challenge of improving a great engine for glorious power levels, this could be fun.
Greg, get some failure pictures on this thread please!
The bottom end has huge forces applied to it from rotational inertia and downward piston forces from power and detonation. IMHO detonation is often ignored but always winds up happening at some point and you might as well plan on it. I don't know what the consensus is on it's effect to the bottom end but I've seen American V8 engines where the 4 bolt main cap is split, that happens from some serious pressure in the direction away from the piston whether it was caused by normal forces or not, it happens as well as cap walk when the forces against the main bearing are greater than the clamping force of the cap bolts. So there are huge forces acting on the crank, how do they effect the block? What are the bottom end studs doing, are they transferring forces to a bad place? What force propogates the cracks in the first place? Is it those 'downward' forces acting through the studs etc or is the crankshaft whipping about and generating many small stress cycles instead of catostrophic big ones? Do the cracks happens gradually or are they sudden?
Ah...the challenge of improving a great engine for glorious power levels, this could be fun.
Greg, get some failure pictures on this thread please!
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From: Chicago Bears
Originally Posted by BrendanC
Even without your tone, I have heard this statement before, and its not meant in a nice way.
Your shadenfreude is showing.
Your shadenfreude is showing.
This is one of the most interesting threads on this forum in a LONG time, with LOTS of good information being shared which we wouldn't have otherwise.
Originally Posted by GregBBRD
Seems like people pretty much say what's on their minds.
Originally Posted by Dozman
Greg if your offending anyone it would be the engine builders. If they were offended they can talk for themselves, since they are very knowledgeable about what they are doing. Too many times people want to talk for others on this forum.
Since Todd and Swaybar is it? "ARE" building and doing their engine builds, they are confident in what they are doing and that their approach is sound. Hopefully it will be a new proven way for HP for us.
hope there's no more Judge Judy Shows on the 928 forums again. Just a waste of time.
Originally Posted by GregBBRD
Both of the stroker engines with cracked blocks made over 500hp. One had a six counterweight Moldex crank and the other had an eight counterweight Scat crank.
Bored to 104mm. Cylinders did not crack 1st and did not crack more than halfway up. The cracks originated from the main bearing area. One was Alusil and the other was Nicosil.
Originally Posted by Mike Simard
So what has to be done to a 928 block to ensure reliability at high power levels?
If those expired engines are Mark's and Joseph's, then they both have the stock engine management computer/software which means stock fuel-maps and ignition-curves, which were written for a stock 5.0L engine.
Granted, their fueling has been manipulated through larger injectors and maybe a rising-rate-fuel-pressure-regulator, but it's still not dialed in taking into account 6.4L displacement, different intake and cams.
Due to the volumetric efficiency change over the stock 5.0L engine, this implies a different cylinder-filling and subsequent burn-rate at any given RPM which means the ignition-timing should be changed too, which it has not. Without an optimized ignition curve, who's to say that the engines didn't detonate/hammer themselves to death over time?
Anytime hardware is changed, the software should be changed too as it's every bit as important as the hardware; the two go hand-in-hand, but most people do not treat it as such.
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From: Attleboro, MA
This is a very interesting thread and I think many of us are interested in the sleeved engines potential, both short and long term. I think Greg asks a fair question and there may well be a development or implementation method that works where others have failed. Not that I'm an expert, but I too fall into the engineer/machinist catagory and have thought about sleeving a spare engine. Gregs info is very interesting as it seems to indicate a wekaness or crack that propogates from the base of the block upwards. Since these failures occured in non-sleeved (but over boared) engines, is there any theory as to the dynamics of the cracking? Becuase of the location and propogation, doesn't this type of crack indicate a flexure in tension at the base of the block? What would be the cuase of that?
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Perhaps not a fair assumption to state that IF the 4 cylinder GTR made 650 HP then the 8 cylinder should be good to 1,200-1,300 since the bottom end of the 944 is very much like the V-8 same number of main bearings but with one bank "cut-off" besides as Greg noted the early GTR blocks were failing at 450 hp too. The first 928 test engine a 5 liter with carbs " after a few minutes ...A crack had developed in the upper portion of the block,right in the middle of the vee,allowing water to penetrate to the outside as well as into the oil...." (later after core shift was limited another engine) .." Another block crack-this time in the lower housing-caused this test to be broken off after only 25 hours.." Later with a reinforced lower housing (cradle) they ran the full endurance test 250 HOURS with 209 hrs at full load. the above was lifted from the book Project 928 page 32. As a side note they stuck the pistons on another test engine and subsequently redesigned the pistons to be more elastic and full skirted. So the 5 liter prototypes with carbs making 250-300 ? hp initially experienced problems with cracks which were corrected but the design change probably was NOT MADE with 500 HP in mind since that was far beyond what was required.