Type 2 overrevs
07-21-2007, 11:50 PM
#1
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Type 2 overrevs
For the archives.
My car had 9 type 2 overrev counts when I bought it. This evening, with PSM turned off at WOT in 1st gear, it broke traction at about 5500 and was instantly on the rev limiter.
Now I have 21 type 2 counts.
So to all the guys who think type 2s can only come from blown down shifts (as I did up till today), you are wrong!
Jeff
My car had 9 type 2 overrev counts when I bought it. This evening, with PSM turned off at WOT in 1st gear, it broke traction at about 5500 and was instantly on the rev limiter.
Now I have 21 type 2 counts.
So to all the guys who think type 2s can only come from blown down shifts (as I did up till today), you are wrong!
Jeff
07-22-2007, 12:33 AM
#4
ummmmm...my guess is something else happened. 
What were the actual readings? The software gives number of ignitions and hours when occurred. We do know what type 2's are and they are typically not from hitting the rev limiter on the way up. The rev limiter is in place to protect in a situation such as yours. Type 2's, AFAIK are when the rev limiter can't hold the revs....otherwise known as over-rev situation. I suppose you could have hit the rev limiter so hard you created an over-rev situation (like top of the redline), but this is not usually the case. In any case it is not good if you care about warranty.
Found this in another thread FWIW:
What were the actual readings? The software gives number of ignitions and hours when occurred. We do know what type 2's are and they are typically not from hitting the rev limiter on the way up. The rev limiter is in place to protect in a situation such as yours. Type 2's, AFAIK are when the rev limiter can't hold the revs....otherwise known as over-rev situation. I suppose you could have hit the rev limiter so hard you created an over-rev situation (like top of the redline), but this is not usually the case. In any case it is not good if you care about warranty.Found this in another thread FWIW:
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."
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."
Last edited by wross996tt; 07-22-2007 at 01:10 AM.
07-22-2007, 01:41 AM
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Originally Posted by wross996tt
ummmmm...my guess is something else happened. What were the actual readings? The software gives number of ignitions and hours when occurred. We do know what type 2's are and they are typically not from hitting the rev limiter on the way up. The rev limiter is in place to protect in a situation such as yours. Type 2's, AFAIK are when the rev limiter can't hold the revs....otherwise known as over-rev situation. I suppose you could have hit the rev limiter so hard you created an over-rev situation (like top of the redline), but this is not usually the case. In any case it is not good if you care about warranty.
Found this in another thread FWIW:
What were the actual readings? The software gives number of ignitions and hours when occurred. We do know what type 2's are and they are typically not from hitting the rev limiter on the way up. The rev limiter is in place to protect in a situation such as yours. Type 2's, AFAIK are when the rev limiter can't hold the revs....otherwise known as over-rev situation. I suppose you could have hit the rev limiter so hard you created an over-rev situation (like top of the redline), but this is not usually the case. In any case it is not good if you care about warranty.Found this in another thread FWIW:
My Type 2 counts are at 520 hours, and the total hour count is 521. I think that's a pretty strong case for my additional 12 counts coming from hitting the rev limiter. QED.
Jeff
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07-22-2007, 12:24 PM
#8
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do you have your ecu tuned/reprogramed? what happens/what gets 'read' if you have your rev-limit increased with a tuned ecu - could you get this situation?
07-22-2007, 12:43 PM
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Originally Posted by Basal Skull
do you have your ecu tuned/reprogramed? what happens/what gets 'read' if you have your rev-limit increased with a tuned ecu - could you get this situation?
UMW-Kevin, does your tuning software let you change the Type 1 and Type 2 overrev thresholds?
Jeff
07-22-2007, 05:09 PM
#11
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Originally Posted by MidnighTT
For the archives.
My car had 9 type 2 overrev counts when I bought it. This evening, with PSM turned off at WOT in 1st gear, it broke traction at about 5500 and was instantly on the rev limiter.
Now I have 21 type 2 counts.
So to all the guys who think type 2s can only come from blown down shifts (as I did up till today), you are wrong!
Jeff
My car had 9 type 2 overrev counts when I bought it. This evening, with PSM turned off at WOT in 1st gear, it broke traction at about 5500 and was instantly on the rev limiter.
Now I have 21 type 2 counts.
So to all the guys who think type 2s can only come from blown down shifts (as I did up till today), you are wrong!
Jeff
Something else happend.
07-22-2007, 05:23 PM
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Originally Posted by tkerrmd
Jeff I do that in my car from time to time. I always have it checked at the dealer for type 2 over revs and have none.
Something else happend.
Something else happend.
I've been checking the overrev counts every time I connect Durametric, which is at least weekly. The range 2 counts went from 9 to 21 yesterday. I bounced off the rev limter hard in 1st gear yesterday. Seem conclusive to me.
Jeff
07-22-2007, 05:29 PM
#13
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Well Jeff you may be right and then if someone explains it to us all as the what is really going on we could all learn something.
On a better note, if considered a type 2 based on your driving the way you did at least it shouldnt be as damaging to the internals? I hope!!
On a better note, if considered a type 2 based on your driving the way you did at least it shouldnt be as damaging to the internals? I hope!!
07-22-2007, 06:58 PM
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A few of us have the capacity to clear the type 1 and 2 counts. But why.. Going from 9 to 21 is a fraction of typical type 1's.. The type two's that you fear are the missed downshifts. Valve float will occur around 7400 RPM's depending on boost pressure.
07-22-2007, 07:06 PM
#15
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Kevin,
I think Jeff is saying he has 21 type 2's, of which he attributes 12 to breaking traction and exceeding redline.
Jeff, that may be possible if your new management system allows revs to exceed Porsche's pre-set redline. In that case, going past our(stock) red line will get you type 1's on the way up, and type 2's on the way down.
Otherwise, the kid who valet'd your car two nights ago missed a downshift. AS
I think Jeff is saying he has 21 type 2's, of which he attributes 12 to breaking traction and exceeding redline.
Jeff, that may be possible if your new management system allows revs to exceed Porsche's pre-set redline. In that case, going past our(stock) red line will get you type 1's on the way up, and type 2's on the way down.
Otherwise, the kid who valet'd your car two nights ago missed a downshift. AS