Where to stop?

v8 coupe

Veteran Member
Joined
Sep 3, 2008
Location
bloomington, mn
TDI
09 rabbit 2.5L Gas
Lower CR will reduce overall thermal efficiency lowering the overall Volumetric efficiency. torque output is a result of VE, you are basically doing the same thing cams do. Cam+ lower CR= drastic dymanic CR change. Power band will move.

If your looking for torque down low you might want to pick your turbo carefully. something that can flow good in the low PR without surging, but will still be able to flow good as PR increases. Port work will also help as it increases VE.
 

Whitbread

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Jan 21, 2007
Location
Johannesburg, MI
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Several
Any theories on why a change in compression ratio would change the powerband?

Did you change cam's or anything else when you changed CR?
Come on now, you're the engineer here :p. Lower cr = less energy generated off boost to drive the piston down = less energy to spool the turbo. This will shift the powerband up slightly.

Having said that, since you're running a stock cam and 17/22, your boost threshold is very low to begin with and in all likely hood you won't suffer much of a loss at all. If you did the pistons and a very large cam, you would notice a definite major loss of power off boost as your dynamic CR would drop into the high 17's.

NoJoke's monster at 16.X:1 is a whole 'nother story. A 1.6 NA rabbit has more low end than it has. However, on boost when dynamic CR is brought up, it's an animal. The turbo system starts to come to life right around 1700-1800rpm though so it's not a big deal. Just keep it above that and it's happy whenever you roll into the throttle.


No need for different piston squirters. A long screwdriver is all that's needed to correctly angle them. Done it a couple times now and works like a charm.
 

Fix_Until_Broke

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Joined
Aug 8, 2004
Location
Menomonee Falls, Wisconsin, USA
TDI
03 Jetta, 03 TT TDI
That makes sense now that I think about it (engineers even miss things once and a while :)), but once the turbo is spooled up the additional mass air in the cylinder for the same boost pressure should allow more fuel for the same smoke level I'd think?

I know lowering the CR will reduce the thermal efficiency, but I wouldn't think it would change volumetric - if any anything I'd think it would improve it for the same operating conditions as mentioned above?

Do I angle the squirters once the pistons are in the engine at BDC so they aim at the hole in the bottom of the piston? They look difficult to remove with the crank installed and at $35 each I think I can bend them a little :)

I need to remember to get the main cap bolts from Fastenal as well tomorrow.
 

Dodoma

Veteran Member
Joined
Mar 30, 2004
TDI
2002 Jetta White
With the mileage you have as well as other issues, your objective should be to make the car run again with minimal cost. So your best strategy should be to replace the parts that fell apart. This theory is based on the assumption that the chance of another piston failling or cracking is remote. So get a used piston from a junk yard and removing the other four, take all to a machine shop to have them cleaned and weighted. Reinstall all these, put head gasket and timing belt. The car should run ok. No need to remove the engine out as the damage is just related to the crack in one piston only and that can be removed and installed without removing the short block. There is also no need to deglaze the bores. Just clean them. You always see marks in the bores here and there.
 

Whitbread

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Forgot to add, for a really nice one piece ring compressor call Total Seal. If they don't have it in stock, they'll machine one up for you in 2-3 days for around $35+ship if I remember right.
 

Fix_Until_Broke

Top Post Dawg
Joined
Aug 8, 2004
Location
Menomonee Falls, Wisconsin, USA
TDI
03 Jetta, 03 TT TDI
Some pictures now that I have the rods and pistons out.

#2 has a crack in it as well - just not as developed yet.





You can just catch it with your fingernail...

The top half of the big end of the rod bearings are showing signs of wear - The crank looks good, but the bearings are "tired"

#1


#2


#3


#4



Wrist pins look good - some minor marks on the brass wrist pin bushings in the piston and rod. Crank looks good on the rod journals.

Engine oil has been 506.01 0w30 for the last ~100k miles, was 5w40 pentosyn before that.

Not sure what this means other than it's time for bearings :)

I'll pull a couple of the mains tomorrow and see what they look like - hopefully better than the rods.
 

Whitbread

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Now's a really easy time to throw new main bearings in it. Pull all the caps, tug the harmonic balancer downward, and use a thin-ish piece of aluminum or brass to "roll" the upper bearing shells out. Reverse to procedure to install new shells. Even though your lower main bearings take the main load, no reason not to change the upper shells while you're this far in.
 

TDIJetta99

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May 17, 2005
Location
Port Jervis, New York, USA
TDI
03... Faster than yours =]
Don't use the 0w30 anymore... Me thinks it's not providing adequate lubrication under heavier loads.. I ran the 0w30 for 10k in mine and never liked the way it sounded especially when the engine was hot.. I switched back to M1-TDT and have been running that or the T6 since.. much happier engine..

Has it ever run without oil? I've pulled a few apart to inspect after a busted oil pan and they looked similar but a little worse depending on how long it was run with the oil light on..
 

Fix_Until_Broke

Top Post Dawg
Joined
Aug 8, 2004
Location
Menomonee Falls, Wisconsin, USA
TDI
03 Jetta, 03 TT TDI
I'm not sure how to get the main caps 1 & 5 off - there does not seem to be enough room to get a socket on the bolts with the rear main seal and front cover installed? The rear main has been seeping the last ~30k miles or so - no drips, but dampness. Water pump has pink crusties growing around it, I'm 30k miles from the next timing belt change. It's looking like I may as well pull the block...Remember the title of this thread, "Where to stop?", yeah - here we are...

It's never been run without oil unless the previous owner did in the 13k miles before I owned it.

An oil pressure/temp gauge will be going in (where I don't know yet, but I'll find a home for it somewhere). I'll report back on what the oil pressures/temps run once I get it back running. A larger oil cooler is also on the list. It will have 5w40 break in oil. I'll decide later if I want to put the 0w30 back in it or not.

Some more pictures...

Lower Rod Bearings

#1


#2


#3


#4



Here's the #4 Rod small end


And the Piston 4 Wrist Pin Bushings





As mentioned above, I could only get the inner main caps off. They're not new, but not near as bad as the rods

#2


#3


#4
 

Whitbread

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No need to pull the block to get 1 and 5 main caps out. Take two old bolts, put them halfway in the cap, grab both bolts with one hand, squeeze them together, and wiggle back and forth. If that doesn't work, GENTLY use a short prybar on the short edge of the cap while wiggling the cap with the bolts in the other hand.

If that doesn't make sense, I'll try to snap a pic.


Are those new pistons 79.48mm? Make sure you measure them just below the oil ring at 90* to the wristpin. Do the math to calculate your piston to wall clearance. I don't recall the oem spec at the moment, sorry. If it's too tight, the block will have to come out to be rigid honed by a machine shop to properly size the cylinders. Otherwise, if your piston to wall clearance is too tight, you'll run the risk of scuffing or even sticking a piston the first time you get it hot.
 
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Fix_Until_Broke

Top Post Dawg
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Location
Menomonee Falls, Wisconsin, USA
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03 Jetta, 03 TT TDI
The ALH's are marked 79.44 and the ARL's are marked 79.46 so 0.00078" bigger in theory - I'll probably remove that much with honing.

ARL 1/2 measures 3.1256" (79.390mm)
ALH #4 measures 3.1245" (79.362mm)
Both measured on the grey coating - I'm assuming that the coating is more worn on the ALH piston causing it to read smaller?

I'll measure them up and calculate the clearances shortly

The issue is that I can't get a socket on the bolt head - even a thin wall chrome socket won't clear the rear main seal and the oil pump chain tensioner is in the way on the one front bolt.
 
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Whitbread

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The ALH's are marked 79.44 and the ARL's are marked 79.46 so 0.00078" bigger in theory - I'll probably remove that much with honing.

ARL 3/4 measures 3.1279" (79.448mm)
ALH #4 measures 3.1245" (79.362mm)
Both measured on the grey coating - I'm assuming that the coating is more worn on the ALH piston causing it to read smaller?

I'll measure them up and calculate the clearances shortly

The issue is that I can't get a socket on the bolt head - even a thin wall chrome socket won't clear the rear main seal and the oil pump chain tensioner is in the way on the one front bolt.
Ah, it was hard to read them in the pic. You should be ok then. If they were .48's you'd be 1.5 thou bigger and that might have caused a tight fit in a couple cylinders.

Hmm, I know I've removed all bearing caps from the bottom in the car, don't remember having any major issue. Maybe try a crowsfoot socket?
 

Keebler145

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Jun 29, 2008
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Niles, Ohio
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Jetta MKIV 2000, 2003, and MKV 2006 PD DSG
Boy I don't know Fix, my motor had 350k miles on it before I tore it down to check on things before going my building route and my rods and mains didn't look like that.

The only time I've seen rod bearing get wiped that hard before was low oil and/or a motor that had the piss lugged out of it. I agree a heavier weight oil should be ran and I would try to keep those RPMs up. The edge of some of the OEM stock piston crown's looked pretty chewed/beat up.

Glad to see you went with some heavier pistons, I'm sure you'll like them coupled with your 17/22!
 

Fix_Until_Broke

Top Post Dawg
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Location
Menomonee Falls, Wisconsin, USA
TDI
03 Jetta, 03 TT TDI
ALH Piston Diameters - 170k miles

#1: 3.1239" = 79.347mm > Bore ~3.131" = 79.527mm > Clearance ~0.007" = 0.178mm
#2: 3.1237" = 79.342mm > Bore ~3.131" = 79.527mm > Clearance ~0.007" = 0.178mm
#3*: 3.1292" = 79.481mm > Bore ~3.1315" = 79.540mm > Clearance ~0.002" = 0.050mm - *Cracked
#4: 3.1238" = 79.344mm > Bore ~3.1305" = 79.515 > Clearance ~0.006" = 0.152mm

ARL Piston Diameters - New

1/2: 3.1256" = 79.390mm > Bore ~3.131" = 79.527mm > Clearance ~0.0055" = 0.140mm
1/2: 3.1256" = 79.390mm > Bore ~3.131" = 79.527mm > Clearance ~0.0055" = 0.140mm
3/4: 3.1256" = 79.390mm > Bore ~3.1315" = 79.540mm > Clearance ~0.006" = 0.152mm
3/4: 3.1258" = 79.395mm > Bore ~3.1305" = 79.515mm > Clearance ~0.005" = 0.127mm
 
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Ski in NC

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Wilmington, NC USA
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2001 Jetta ALH 5sp stock
The issue is that I can't get a socket on the bolt head - even a thin wall chrome socket won't clear the rear main seal and the oil pump chain tensioner is in the way on the one front bolt.
I've turned sockets down on a lathe to get side clearance. Too much and socket will break, but worth a try. If no lathe, you could grind it down, but a little crude there.

But the mains do look to be in pretty good shape.
 

Fix_Until_Broke

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Aug 8, 2004
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Menomonee Falls, Wisconsin, USA
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03 Jetta, 03 TT TDI
I might be able to get an open end wrench or a crowsfoot on them, but they're tight clearance.





Whitbread said:
..........go to fastenal and get some M10x80mm 12.9 capscrews and 3/8" grade 8 SAE washers to put in the for the main bolts.
All I can find is socket head capscrews in 12.9 - no hex head like what was in there. This will make installation a snap (and removal if I should ever have to do this again).

I can turn down a socket or use a wrench or whatever to get the existing bolts out - I was more concerned about getting them back in, but the socket head screws elimnate that issue.
 

Whitbread

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I might be able to get an open end wrench or a crowsfoot on them, but they're tight clearance.

All I can find is socket head capscrews in 12.9 - no hex head like what was in there. This will make installation a snap (and removal if I should ever have to do this again).

I can turn down a socket or use a wrench or whatever to get the existing bolts out - I was more concerned about getting them back in, but the socket head screws elimnate that issue.
I just went out and measured an old craftsman 17mm short socket that I used to take those bolts out before in a car and it's only .855" OD. All my other non impact 17mm's are .930-.970". That must be the secret trick. Never even thought about it before.

The socket head cap screws will be a snap to re-install for sure!
 

Fix_Until_Broke

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I turned a 17mm 6pt socket down to 0.855 diameter, but didn't go far enough down the OD so I couldn't get full engagement on the head of the bolt. I'll turn it down for more of the length tomorrow and get the last cap off (I was able to get the #1 cap off finally).

I was planning on measuring the piston protrusion, picking the correct head gasket and putting the head back on with the ARP head studs.

Should I strip the head and have it surfaced before putting it back together or will it be fine as-is? Gasket never leaked, all was well when it came apart (except for all the above :)), it came apart "cool" to the touch, but not "cold" - probably 80F.
 

Whitbread

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Should I strip the head and have it surfaced before putting it back together or will it be fine as-is? Gasket never leaked, all was well when it came apart (except for all the above :)), it came apart "cool" to the touch, but not "cold" - probably 80F.
Having the head skimmed is cheap insurance plain and simple at this point.
 

greengeeker

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Cambridge, MN
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2002 Jetta GLS
When pulling the trailer heavy it will run 1200F-1400F EGT's steady state - Light trailer will run ~1000F. I've done about 4000 miles of heavy trailer pulling and ~8000 miles of light trailer pulling. Self imposed 20 psi boost limit when pulling the trailer, the tunes run 24-26 psi max.
Forgive me if this is already common knowledge...I don't read up on TDI towing all that often.

Does this clearly define 1200-1400 sustained EGT's as too high for stock internals? If it is too high, what is the limit? If he upgrades to the ARL pistons does the limit change? Same question if he were to simply coat the ALH pistons?

Sorry to hijack - I'd like to learn as this is critical information for my next build. :eek:
 

TDIJetta99

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Port Jervis, New York, USA
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03... Faster than yours =]
If your cooling system is in good shape, and you have good oil, and you aren't lugging the engine, 1650F is the max sustained... The VNT vanes and the blades on the exhaust wheel of the turbo are the weak link.. Everything else inside the engine is cooled by some other source (oil or coolant).. Mine has seen sustained 1550-1600F for 4-5 miles at a time on long uphill pulls, but everything else was in check.. coolant was under 220F, oil under 250F, rpm around 3200, 80% throttle to maintain speed...
 
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