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risk
Samba Member
Joined: June 24, 2004
Posts: 710
Location: Stumpbroke, Arkansas
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 Posted: Wed Apr 03, 2013 9:27 am Post subject: |
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turboblue
Samba Member
Joined: October 09, 2003
Posts: 4216
Location: Central Indiana
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| Posted: Wed Apr 03, 2013 10:33 am Post subject: |
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My 1st turbo engine had a lot of deck to get the compression down with the heads I was using.
.125" to be exact plus the copper gasket.......that was in the late '80's and we didn't know better then.
Never cracked a cylinder even with 28psi of boost.
Detonation is your likely culprit in this case.
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Gary
Turbo VW Sand Drag Buggy
"If you don't run into the Devil every once in awhile, you must be going in the same direction!" |
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miniman82
Samba Swamp Donkey
Joined: March 22, 2005
Posts: 9515
Location: Southern Maryland
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smithers
Samba Member
Joined: June 21, 2007
Posts: 240
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| Posted: Wed Apr 03, 2013 6:19 pm Post subject: |
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| You should also have the head "cleaned up" it probably left a small burr in the head at the crack. I had the same thing happen when it ran lean under boost. |
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turboblue
Samba Member
Joined: October 09, 2003
Posts: 4216
Location: Central Indiana
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| Posted: Thu Apr 04, 2013 8:39 am Post subject: |
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| miniman82 wrote: |
| wastegate get stuck or something? |
No, I run it at 28#
It did stick one time and broke a 30# boost gauge.
Best I could tell it went to about 43#.........sure did make one helluva pass it did........... 
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Gary
Turbo VW Sand Drag Buggy
"If you don't run into the Devil every once in awhile, you must be going in the same direction!" |
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miniman82
Samba Swamp Donkey
Joined: March 22, 2005
Posts: 9515
Location: Southern Maryland
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| Posted: Thu Apr 04, 2013 9:06 am Post subject: |
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Probably wasn't lean (detonating) if the ring lands didn't collapse, you might want to make sure they aren't pinched when you pull it down. If not, it's just the barrels being too weak. 
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Build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=212747
| Glenn wrote: |
| satterley_sr wrote: |
I just wanted to bitch but I'm getting no sympathy. |
Welcome to the Samba. |
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risk
Samba Member
Joined: June 24, 2004
Posts: 710
Location: Stumpbroke, Arkansas
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| Posted: Thu Apr 04, 2013 9:13 am Post subject: |
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| smithers wrote: |
| You should also have the head "cleaned up" it probably left a small burr in the head at the crack. I had the same thing happen when it ran lean under boost. |
It did leave a burr but I had copper gaskets in there so the heads are clean.
| miniman82 wrote: |
| Probably wasn't lean (detonating) if the ring lands didn't collapse, you might want to make sure they aren't pinched when you pull it down. If not, it's just the barrels being too weak. |
The ring lands look fine, the rings even look good just some minor scuffing. Veedubcrazy is hooking me up with some cylinders and rings, so I should be good to go. |
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Chip 
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Thu Apr 04, 2013 1:28 pm Post subject: |
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I did this same thing a week or two ago. Why were you running 25-30psi? Was this on the street? Pump gas? Efi? I cracked mine at 18psi, but went a little too lean. Had to drive mine about 6 miles home. not a fun drive  |
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risk
Samba Member
Joined: June 24, 2004
Posts: 710
Location: Stumpbroke, Arkansas
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| Posted: Thu Apr 04, 2013 1:52 pm Post subject: |
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| Chip B. wrote: |
| I did this same thing a week or two ago. Why were you running 25-30psi? Was this on the street? Pump gas? Efi? I cracked mine at 18psi, but went a little too lean. Had to drive mine about 6 miles home. not a fun drive |
Yes, on the street, EFI, 93 octane pump gas
Two reasons..
I couldn't get over 12psi boost, so I was messing with re-plumbing my boost control to closed loop. Didn't have it turned down nearly enough and overboosted.
And, I had reverted my tune to an older version where I didn't have the overboost protection turned on.
Live and learn I guess... |
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Chip
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Thu Apr 04, 2013 4:32 pm Post subject: |
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| Doh! I've had mine up to 24psi multiple times in the past with no issues, but i always had the fuel to cool it. This time it went just a bit too lean. 91 octane here. What pistons are you running? |
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Chip
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Thu Apr 04, 2013 4:33 pm Post subject: |
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| Doh! I've had mine up to 24psi multiple times in the past with no issues, but i always had the fuel to cool it. This time it went just a bit too lean. 91 octane here. What pistons are you running? |
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veedubcrazy
Samba Member
Joined: February 14, 2005
Posts: 2130
Location: La Porte, Tx.
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| Posted: Thu Apr 04, 2013 7:56 pm Post subject: |
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| risk wrote: |
Pulled the 3-4 side apart last night... #4 was cracked too, almost the entire length of the barrel.
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[email protected]
Samba Member
Joined: August 03, 2002
Posts: 12785
Location: Salt Lake City, Utah
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| Posted: Thu Apr 04, 2013 8:36 pm Post subject: |
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don't go leaner than 13:1 on boost!!!! 12.75 is safer
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risk
Samba Member
Joined: June 24, 2004
Posts: 710
Location: Stumpbroke, Arkansas
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| Posted: Fri Apr 05, 2013 12:30 pm Post subject: |
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I was shooting for 11.5 to 11.8 to be on the safe side..
They're about to open a new gas station in town that will have E85..
So I'm thinking I need to raise my static compression ratio a bit for this fuel. Also, having the tighter deck, the cyls might not be so prone to cracking.
I was running 0.085" deck plus 0.040" copper gasket.
This put my C/R around 7.89 :1
If I don't run the copper gaskets, 8.54 :1
If I cut the cylinders down 0.045", 9.21 :1 |
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56Speedster
Samba Member
Joined: May 14, 2009
Posts: 66
Location: UFO Capital
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| Posted: Fri Apr 05, 2013 5:56 pm Post subject: |
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| Chip B. wrote: |
| Doh! I've had mine up to 24psi multiple times in the past with no issues, but i always had the fuel to cool it. This time it went just a bit too lean. 91 octane here. What pistons are you running? |
Were you messing with the tune Chip? I've been playing with my tune and am getting good results at 18psi. My newest problem is keeping the street tires glued to the asphalt. Even when I go easy on 1st gear, they spin like mad all the way through 2nd and into 3rd. I'm hoping to ease into 20+psi but I hope I can keep the power on the ground where it needs to be but am happier than a pig in sh!t that I'm doing it all on 91 pump gas.
Thanks for pointing me in the right direction on the squishies!!! |
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Chip
Samba Member
Joined: July 19, 2008
Posts: 969
Location: Utah
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| Posted: Fri Apr 05, 2013 9:11 pm Post subject: |
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| 56Speedster wrote: |
| Chip B. wrote: |
| Doh! I've had mine up to 24psi multiple times in the past with no issues, but i always had the fuel to cool it. This time it went just a bit too lean. 91 octane here. What pistons are you running? |
Were you messing with the tune Chip? I've been playing with my tune and am getting good results at 18psi. My newest problem is keeping the street tires glued to the asphalt. Even when I go easy on 1st gear, they spin like mad all the way through 2nd and into 3rd. I'm hoping to ease into 20+psi but I hope I can keep the power on the ground where it needs to be but am happier than a pig in sh!t that I'm doing it all on 91 pump gas.
Thanks for pointing me in the right direction on the squishies!!! |
I'm always messing with the tune, been on a quest to lean it out a lot, the car was absolutely evil the time before it popped. I just went a little too far. It seems to really like about 12.0:1.
You're welcome!  |
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56Speedster
Samba Member
Joined: May 14, 2009
Posts: 66
Location: UFO Capital
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| Posted: Sun Apr 07, 2013 9:56 am Post subject: |
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| I need to do some more tuning but have it currently running pretty sweet at 18psi now. I'm thinking that I really need to get into some kind of staged boost setup because of the severe tire spinning through the first 2 gears. Is a ton of fun though and is much faster today than it was with the flat top pistons. |
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[email protected]
Samba Member
Joined: August 03, 2002
Posts: 12785
Location: Salt Lake City, Utah
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| Posted: Sun Apr 07, 2013 10:14 am Post subject: |
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Timing and A/F are directly related. If the engine runs best at 12:1, at 13:1 it will just need less ignition timing. Even on boost the engine will make best power in the 12.75-13:1 range, WHEN IGNITION IS OPTIMIZED.
Every molecule of fuel takes the space of a molecule of O2. So if you run "over-rich" you have less O2 to combust. It's a balance. Chemically speaking you'd make the most power at Stoic, but in reality every fuel molecule "can't find" an O2 molecule to match up with, when you run Stoic. So running a little richer than Stoic is how you combust all the available O2 (within reason). But too rich you lose power, because in the 12.75-13:1 range you have already used up almost all the O2, but richer that that and you have started displacing O2 with the extra fuel, which is why potential power drops.
If an engine makes more power "richer", it likely means the leaner tune had too much timing to begin with. Timing is DIRECTLY RELATED TO FUEL. If you treat them as unrelated you are making a common error.
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mightymouse
Samba Member
Joined: May 26, 2004
Posts: 4220
Location: las vegas
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| Posted: Thu Jun 27, 2013 1:38 pm Post subject: |
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What turbo is on this setup? where is timing set and how? ditch the shit 92s or this will happen again and again. The cyl wall is far too thin.
BUT... cylinder pressure was obviously WAY Too high due to improper timing at peak torque.
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Note to EVERYONE.
Know your ZDDP levels or you WILL lose a cam and lifters. |
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risk
Samba Member
Joined: June 24, 2004
Posts: 710
Location: Stumpbroke, Arkansas
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| Posted: Thu Jun 27, 2013 1:49 pm Post subject: |
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| mightymouse wrote: |
What turbo is on this setup? where is timing set and how? ditch the shit 92s or this will happen again and again. The cyl wall is far too thin.
BUT... cylinder pressure was obviously WAY Too high due to improper timing at peak torque. |
I'm running a Comp CT4.. ignition is thru megasquirt w timing set to 24 deg under boost.
I have since replaced the cylinders and rings, ditched the copper head shims and I have the overboost protection set to 15psi. It's running excellent with no problems so far.
Yes, the cylinders are super thin... but I think the carnage could have been avoided had I not plumbed the wastegate wrong and had the overboost protection off. |
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