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trying to understand Type II over revs ?


skipp

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I've read the posts on this topic and would appreciate a clarification.

When the computer records type II over revs, does this simply mean that the rev limiter was activated. In other words, is a type II over rev simply hitting the rev limiter anytime at all ?

Thanks

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There is some debate on the difference between type I and type II. It was thought that typically a missed down shift would cause a type II and hitting the limit on the way up a type I. I think Loren has a reasonable definition for type II, but this could also occur if you hit the rev limiter on the way up so quickly the ECU does not react fast enough...so essentially there may be a type I at a certain rpm and a type II at a higher rpm.

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WROSS: I've never heard of a Stage 1 over rev becoming a stage 2 on an up-shift.. I'm not sure how you would accomplish an overrev on the way up.....if the rev-limiter is working as it should, and it's cutting off the gas at 7200...how would you suppose that it would in some way go into a Stage 2? I can't visualize how this would occur.....

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WROSS: I've never heard of a Stage 1 over rev becoming a stage 2 on an up-shift.. I'm not sure how you would accomplish an overrev on the way up.....if the rev-limiter is working as it should, and it's cutting off the gas at 7200...how would you suppose that it would in some way go into a Stage 2? I can't visualize how this would occur.....

Chuck, I thought the same thing until this thread and posts by Jeff (MidnighTT) 6speed link.

He said he lost traction on the way up and logged type II over revs (durametric software). You got a better explanation of what happened?

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  • Moderators

MidnightTT did not supply some missing information. Such as the fact that his DME may have been altered to raise the rev limiter, and that is why he can get into range 2 under acceleration.

http://www.renntech.org/forums/index.php?s...&hl=altered

His car was in fact "tuned" by Kevin. http://forums.rennlist.com/rennforums/show...ight=MidnightTT And Keven said "if" he raised the rev limiter then Midnight can get in range 2.

So the only plausible theory base on what little info was supplied by MidnightTT, is that part of the alterations to his DME included raising the limit at which the rev limiter comes on. In the old days some of these tuners simply removed the rev limiter as a way to get a hp increase.

Now, if you would like a nice 1999 Boxster with 1,884.7 operating hours, and no range 1 or 2, then let me know....

post-4-1193603216_thumb.jpg

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WROSS et al: I read the various threads...the pros and cons....yea's and nays....and it still doesn't make much sense to me that you can blow by the limiter on the way up. I do not have an engineering background....so I'm basing my comments on what I would consider as logic......if the rev limiter cuts off the gas at the threshold (for most it's 7200)....then I am having a hard time visualizing how you continue to power the engine to blow by the threshold.....no gas...no power, engine stops accelerating.

Let's say you were driving along and suddenly you hit a patch of ice when you were accelerating....and the rpm's suddenly shot up.....would the engine have enough rpm's or energy to keep accelerating past the threshold? I don't know the answer....and after reading the links and reading all the comments about people calling each other stupid etc.....I certainly don't want to start anything. Suffice it to say....I am having difficulty figuring out a Stage II over-rev on the upshift. Guess I'm just dumb.

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Software works sequentially.

After some period of observation the SW decides "rpm too high, cut fuel"

If the engine is accelerating wildly, then perhaps the time it takes for this step is long enough that within the next time period the DME analyzes the engine will already be into a Type 2 over rev.

Remember these are step, by step computations and calculations- all piggybacked onto a continuous mechanical process.

I will not hold my breath for Porsche to provide clarification- other than the party line "Type 2 is abuse, Type 2 is abuse, Type 2 is abuse" you get it. Why possible reason would they have for exposing the truth on this matter?

A

PS It doesn't happen on the "up shift" it is on the 'late shift'....

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WROSS et al: I read the various threads...the pros and cons....yea's and nays....and it still doesn't make much sense to me that you can blow by the limiter on the way up. I do not have an engineering background....so I'm basing my comments on what I would consider as logic......if the rev limiter cuts off the gas at the threshold (for most it's 7200)....then I am having a hard time visualizing how you continue to power the engine to blow by the threshold.....no gas...no power, engine stops accelerating.

Let's say you were driving along and suddenly you hit a patch of ice when you were accelerating....and the rpm's suddenly shot up.....would the engine have enough rpm's or energy to keep accelerating past the threshold? I don't know the answer....and after reading the links and reading all the comments about people calling each other stupid etc.....I certainly don't want to start anything. Suffice it to say....I am having difficulty figuring out a Stage II over-rev on the upshift. Guess I'm just dumb.

Chuck...I don't recall calling anyone names about this...and I don't think anyone actually knows the answer. There are a number of hypotheses about what may be going on and several of them seem quite rational (or logical as you say)...though that does not make them correct. I also don't know anyone that wants to try to create Type IIs by running some experiments. ARDs explanation seems quite rational...and my guess is we may never actually know the truth. But it doesn't mean we can't suppose.

Tool Pants...I believe MignighTT did indicate that he had not requested the rev limit change and Kevin indicated he only changed it upon request...so FWIW.

Edited by wross996TT
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