Range 2 ignitions - need help in undstanding the meaning.
#17
02-11-2007, 10:19 PM
Originally Posted by CSD952
Tom,
Thanks, that it is more definitive than any description I've seen. Does it matter when the type 2's occurred relative to total hours on the engine? If early in engine life and it has soldiered on for many hours is it likely okay or is it considered a hand grenade with the pin pulled? I suspect any answer to that question is pure conjecture, but I just had to ask.
Carmen
__________
03 TT X50
Thanks, that it is more definitive than any description I've seen. Does it matter when the type 2's occurred relative to total hours on the engine? If early in engine life and it has soldiered on for many hours is it likely okay or is it considered a hand grenade with the pin pulled? I suspect any answer to that question is pure conjecture, but I just had to ask.
Carmen
__________
03 TT X50
Yes, I think that if the car has been fine for 10,000 miles after an event chances are it is ok. If real damage had occured to valves etc it is usually obvious immediately. Also the conditions the car sees will probably make a difference if more minor damage had occured. For example a car tracked heavily and often versus a garage queen. Bottom line is type 2 = crap shoot and for those of us with OCD we just couldnt take the worry!!!
Kevin you should have given me a shout!!!! Sorry I missed ya!!!! tom
#18
02-24-2007, 05:58 PM
So which one if either is when you hit the rev limiter?
Originally Posted by tom kerr
Kevin, I think you may be incorrect if you are using range 2 and type 2 over rev as the same thing. maybe this will help, some info from cyberspace......
"I discovered some information on the Type 1 and Type 2 over-revs that I would like to share. I purchased the Durametric OBD-II software and cable set a week ago and have evaluated my error codes and Over-Rev Counts The count that is recorded, and cannot be erased to my knowledge, is a count of the ignition firings above the redline threshold. It is not the total of the times that the engine has breached the redline value, as I was led to believe. The count is broken down into the two categories and I'm not sure how it does this, but it just does.
A Type 1 is an over-rev condition that thru to engines own inertia or power stroke has exceeded redline and the DME has fired the ignition during above redline and the condition has recorded the individual firings. It also records the time (Total Hours) and is revised at each event.
A Type 2 is an over-rev condition when an external force has caused the engine to speed beyond the redline threshold such as down shifting to a lower gear and engine matches the rpm of the transmission input shaft.
The difference between the two may sound subtle, but is more involved.
In a Type 1 condition, such as when one misses and up-shift. The engine is in a free-wheeling state and the internal energy is acting on the rotating and reciprocating mass. The crankshaft is unloaded for a brief moment and there is still some force on the top of the piston during most of the 4 stroke cycle.
Type 2 conditions are not healthy for the rod and rod bolts, although there must be some design reserve before yield. When one down shifts to a gear which leads to an over-rev condition, there is little energy pushing down on the head of the piston to keep the rod in a compression mode. The crankshaft is pushing violently on the rod and then jerking the piston and rod assembly back towards the crank centerline. The rods are primarily designed for a compression mode, meaning forces enacted on the top of the piston and imparting energy into the crankshaft via the connecting rod. The connecting rods and bolts really don’t like the dynamics in a stretching mode and this condition leads to material yielding. This is the condition that causes the rod bolts to fail. They yield during the stretch. The connecting rod can also yield due to stretch, but that is seen more with Aluminum Connecting Rods."
hope that makes some thing clearer for ya! Carmen?
"I discovered some information on the Type 1 and Type 2 over-revs that I would like to share. I purchased the Durametric OBD-II software and cable set a week ago and have evaluated my error codes and Over-Rev Counts The count that is recorded, and cannot be erased to my knowledge, is a count of the ignition firings above the redline threshold. It is not the total of the times that the engine has breached the redline value, as I was led to believe. The count is broken down into the two categories and I'm not sure how it does this, but it just does.
A Type 1 is an over-rev condition that thru to engines own inertia or power stroke has exceeded redline and the DME has fired the ignition during above redline and the condition has recorded the individual firings. It also records the time (Total Hours) and is revised at each event.
A Type 2 is an over-rev condition when an external force has caused the engine to speed beyond the redline threshold such as down shifting to a lower gear and engine matches the rpm of the transmission input shaft.
The difference between the two may sound subtle, but is more involved.
In a Type 1 condition, such as when one misses and up-shift. The engine is in a free-wheeling state and the internal energy is acting on the rotating and reciprocating mass. The crankshaft is unloaded for a brief moment and there is still some force on the top of the piston during most of the 4 stroke cycle.
Type 2 conditions are not healthy for the rod and rod bolts, although there must be some design reserve before yield. When one down shifts to a gear which leads to an over-rev condition, there is little energy pushing down on the head of the piston to keep the rod in a compression mode. The crankshaft is pushing violently on the rod and then jerking the piston and rod assembly back towards the crank centerline. The rods are primarily designed for a compression mode, meaning forces enacted on the top of the piston and imparting energy into the crankshaft via the connecting rod. The connecting rods and bolts really don’t like the dynamics in a stretching mode and this condition leads to material yielding. This is the condition that causes the rod bolts to fail. They yield during the stretch. The connecting rod can also yield due to stretch, but that is seen more with Aluminum Connecting Rods."
hope that makes some thing clearer for ya! Carmen?
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