205 turbo crank pressure problems
Discussion
Evoluzione said:
Hmmm, I disagree, when you find out you need them it's too late.
Build it right and strong first time, forged pistons and 4340 rods aren't too expensive (compared to stock items) these days. This is an N/A engine that's been turbo'd and putting out twice as much power as it was originally designed for.
It's an engine running very low boost, so under very little pressure. Boost rarely ever kills rods, rpm does. And doubtful this engine is a screamer.Build it right and strong first time, forged pistons and 4340 rods aren't too expensive (compared to stock items) these days. This is an N/A engine that's been turbo'd and putting out twice as much power as it was originally designed for.
It's all very well saying yes...buy this, buy that, lets buy the best of everything...for an engine barely making 50% more power than it had anyway.
Why stop and rods and pistons...why not crank, why not a better block, why not...etc etc
A prime example is the current phase of people buying 4.8 and 5.3 LS based motors in the US. They're boosting them with standard crank, rods etc to 4-5x the original power output and they're surviving quite happily. The short motors arent anything fancy at all, but they are so cheap to replace, they just dont care. Except they are holding incredible amounts of power.
OEM Subarus....the turbo engines right use the exact same rods as the 1.6, 1.8 etc n/a engines right through from the late 80's until early 2000's
Just because a rod is in a n/a engine, doesnt mean it is weak or unsuitable for boost.
stevieturbo said:
It's an engine running very low boost...
it's running 1.2 bar, that's quite high for a converted N/A engine IMO, most standard turbo cars run below 1 bar don't they? all the ones I've worked on have done anyways 
the only reason I suggested/advised putting in rods was reliability. The OP doesn't want to spend out on forged pistons only to have the rods fly at 6krpm and smash the pistons again...
BTW, Max, did you get your cookie?
stevieturbo said:
It's an engine running very low boost, so under very little pressure. Boost rarely ever kills rods, rpm does. And doubtful this engine is a screamer.
It's all very well saying yes...buy this, buy that, lets buy the best of everything...for an engine barely making 50% more power than it had anyway.
Why stop and rods and pistons...why not crank, why not a better block, why not...etc etc
A prime example is the current phase of people buying 4.8 and 5.3 LS based motors in the US. They're boosting them with standard crank, rods etc to 4-5x the original power output and they're surviving quite happily. The short motors arent anything fancy at all, but they are so cheap to replace, they just dont care. Except they are holding incredible amounts of power.
OEM Subarus....the turbo engines right use the exact same rods as the 1.6, 1.8 etc n/a engines right through from the late 80's until early 2000's
Just because a rod is in a n/a engine, doesnt mean it is weak or unsuitable for boost.
The engine is fitted to a competition car running 1.2 bar more than standard, it's going to get plenty of abuse right from the off.It's all very well saying yes...buy this, buy that, lets buy the best of everything...for an engine barely making 50% more power than it had anyway.
Why stop and rods and pistons...why not crank, why not a better block, why not...etc etc
A prime example is the current phase of people buying 4.8 and 5.3 LS based motors in the US. They're boosting them with standard crank, rods etc to 4-5x the original power output and they're surviving quite happily. The short motors arent anything fancy at all, but they are so cheap to replace, they just dont care. Except they are holding incredible amounts of power.
OEM Subarus....the turbo engines right use the exact same rods as the 1.6, 1.8 etc n/a engines right through from the late 80's until early 2000's
Just because a rod is in a n/a engine, doesnt mean it is weak or unsuitable for boost.
Pushing an already built modern engine to the limit to see what happens is totally different to having to re-build a very old one which was designed as N/A and has seen a lot of action.
Some engine makers are known for over specifying parts, many are not.
There is a lot more to engine (component) failure than bending a rod and det'. I've taken out failed pistons with no signs of det whatsoever and seen plenty of unexplained big end bearing failures.
Unexplainable by the customer that is, until a strip down revealed that the old rods had gone oval around the bearing journal due to the constant stress on a weaker grade of steel. Also old factory rods for lower power often have no positive location for the end cap and weak bolts, this leads to the cap walking around and bearing failure.
Do people blame the failure of a bearing on the rod? No.
Do people blame the bending of a rod on the actual rod? Yes.
Both can be incorrect assumptions, quite often you have to look further than the end of your nose.
The re-fitting of a 20yr old stressed component in a new build is laughable, not when decent rods can be had for not much more money than new OE ones in many cases.
There is a lot of enjoyment to be had from taking a properly built strong engine by the scruff of the neck and giving it hell, much more than pussy footing around wondering if something might break....
stevieturbo said:
There is little need fitting forged rods if they are not needed. Even pistons....it was detonation that broke those, not any specific weakness in the piston.
A forged piston may survive longer, but if there is a problem, it's going to fail eventually.
I can't see any evidence of detonation on the piston tops? If there was det wouldn't they be pitted to hell?A forged piston may survive longer, but if there is a problem, it's going to fail eventually.
just to add a bit more input the engine was built with all new rods and pistons in 2009 i didnt build engine its a left hooker griffe from holland with my very untrained eye i cant see any other damage or signs of wear on the other pistons no signs of any pitting on piston tops, big end bearings look fine etc i have an article in a dutch magazine in which the car was featured i cant read dutch but i can make out a few things it mentions 7,2:1 i assume thats compression ratio which seems low to me even for a turbo car ? dont think 1.2bar is low boost to be honest , i drive car hard its a sprint car so it gets max attack although only for a short time
Pushing an already built modern engine to the limit to see what happens is totally different to having to re-build a very old one which was designed as N/A and has seen a lot of action.
Some engine makers are known for over specifying parts, many are not.
There is a lot more to engine (component) failure than bending a rod and det'. I've taken out failed pistons with no signs of det whatsoever and seen plenty of unexplained big end bearing failures.
Unexplainable by the customer that is, until a strip down revealed that the old rods had gone oval around the bearing journal due to the constant stress on a weaker grade of steel. Also old factory rods for lower power often have no positive location for the end cap and weak bolts, this leads to the cap walking around and bearing failure.
Do people blame the failure of a bearing on the rod? No.
Do people blame the bending of a rod on the actual rod? Yes.
Both can be incorrect assumptions, quite often you have to look further than the end of your nose.
The re-fitting of a 20yr old stressed component in a new build is laughable, not when decent rods can be had for not much more money than new OE ones in many cases.
There is a lot of enjoyment to be had from taking a properly built strong engine by the scruff of the neck and giving it hell, much more than pussy footing around wondering if something might break....
Evoluzione said:
stevieturbo said:
It's an engine running very low boost, so under very little pressure. Boost rarely ever kills rods, rpm does. And doubtful this engine is a screamer.
It's all very well saying yes...buy this, buy that, lets buy the best of everything...for an engine barely making 50% more power than it had anyway.
Why stop and rods and pistons...why not crank, why not a better block, why not...etc etc
A prime example is the current phase of people buying 4.8 and 5.3 LS based motors in the US. They're boosting them with standard crank, rods etc to 4-5x the original power output and they're surviving quite happily. The short motors arent anything fancy at all, but they are so cheap to replace, they just dont care. Except they are holding incredible amounts of power.
OEM Subarus....the turbo engines right use the exact same rods as the 1.6, 1.8 etc n/a engines right through from the late 80's until early 2000's
Just because a rod is in a n/a engine, doesnt mean it is weak or unsuitable for boost.
The engine is fitted to a competition car running 1.2 bar more than standard, it's going to get plenty of abuse right from the off.It's all very well saying yes...buy this, buy that, lets buy the best of everything...for an engine barely making 50% more power than it had anyway.
Why stop and rods and pistons...why not crank, why not a better block, why not...etc etc
A prime example is the current phase of people buying 4.8 and 5.3 LS based motors in the US. They're boosting them with standard crank, rods etc to 4-5x the original power output and they're surviving quite happily. The short motors arent anything fancy at all, but they are so cheap to replace, they just dont care. Except they are holding incredible amounts of power.
OEM Subarus....the turbo engines right use the exact same rods as the 1.6, 1.8 etc n/a engines right through from the late 80's until early 2000's
Just because a rod is in a n/a engine, doesnt mean it is weak or unsuitable for boost.
Pushing an already built modern engine to the limit to see what happens is totally different to having to re-build a very old one which was designed as N/A and has seen a lot of action.
Some engine makers are known for over specifying parts, many are not.
There is a lot more to engine (component) failure than bending a rod and det'. I've taken out failed pistons with no signs of det whatsoever and seen plenty of unexplained big end bearing failures.
Unexplainable by the customer that is, until a strip down revealed that the old rods had gone oval around the bearing journal due to the constant stress on a weaker grade of steel. Also old factory rods for lower power often have no positive location for the end cap and weak bolts, this leads to the cap walking around and bearing failure.
Do people blame the failure of a bearing on the rod? No.
Do people blame the bending of a rod on the actual rod? Yes.
Both can be incorrect assumptions, quite often you have to look further than the end of your nose.
The re-fitting of a 20yr old stressed component in a new build is laughable, not when decent rods can be had for not much more money than new OE ones in many cases.
There is a lot of enjoyment to be had from taking a properly built strong engine by the scruff of the neck and giving it hell, much more than pussy footing around wondering if something might break....
Evoluzione said:
The re-fitting of a 20yr old stressed component in a new build is laughable
Dont be silly now. Buy that logic, you'd never use a 20 year old crank, 20 year old block, 20 year old cylinder head etc etcThe list could go on really. But if the stresses on the part are nowhere near a level to pose it a problem, then changing it could be deemed rather wasteful.
And 1.2 bar is low boost in my book.
ninjacost said:
what should i be looking for Jimbob ?
irregularities between each pistons ring lands. if the ring clearance should be 0.002" all the way around but you find it's more on one side or in 1 particular spot and the difference is significant then the piston is borked. as Max_Toque said any deformation of the lands.
jimbob82 said:
Yeh I know of a few cars running mega boost but I was referring to standard boost levels on production cars. This is a converted n/a engine so 1.2 is relatively high.
7.2:1 CR and you think 1.2 bar is high ?Ive run 30psi boost on n/a engines converted to turbo use. 1.2 bar is not high at all.
ok thanks for that i will check
jimbob82 said:
irregularities between each pistons ring lands. if the ring clearance should be 0.002" all the way around but you find it's more on one side or in 1 particular spot and the difference is significant then the piston is borked. as Max_Toque said any deformation of the lands.
Inspect the ring grooves closely for any size of deformtion like widening or steps. If the ring pack or ring lands have been overloaded steps may have been formed as the ring twists and its corners jam into the lands. This is bad, as it creates massive stress concentrations causing cracking and failure even if the "bulk" piston material has sufficient strength.
Evoluzione said:
There is a lot of enjoyment to be had from taking a properly built strong engine by the scruff of the neck and giving it hell, much more than pussy footing around wondering if something might break....
A built motor doesn't guarantee a longer lifespan either. A friend built a turbo motor with H beam rods, forged pistons blah blah but a rod bolt let go. An ARP rod bolt, which are supposed to be indestructible, but they're not.SuperchargedVR6 said:
A built motor doesn't guarantee a longer lifespan either. A friend built a turbo motor with H beam rods, forged pistons blah blah but a rod bolt let go. An ARP rod bolt, which are supposed to be indestructible, but they're not.
Maybe he tightened it up incorrectly.Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff