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      05-02-2012, 01:11 AM   #1
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Potential Horsepower Decrease?

I am pretty sure most of you are like me, we want to have a 400WHP NA M3 but just can't hit it. M3's stock power can range anywhere from 330WHP - 360WHP on the same dyno! So this got me thinking, is it how we drive and take care of the car? And can we potentially damage/decrease the power of the car with money shifts, bouncing off redline, accidental redline with cold engine, or abused by dealer like me (revved the car to redline with cold engine: http://www.m3post.com/forums/showthread.php?t=673085)? I know the above can potentially shorten the engine's life, but will it decrease its power?
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      05-02-2012, 01:25 AM   #2
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If you damage the piston rings or cylinder walls (via a lack of oil, excessive heat, etc.), you will lose some amount of compression in that cylinder(perhaps trivial, perhaps not, depending on the severity), which will cause for a reduction in power. Anything that can bend valves, negatively impact valve guides and seals, can lead to a reduction in compression, and thus in power production.
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      05-02-2012, 01:46 AM   #3
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Quote:
Originally Posted by piloto View Post
If you damage the piston rings or cylinder walls (via a lack of oil, excessive heat, etc.), you will lose some amount of compression in that cylinder(perhaps trivial, perhaps not, depending on the severity), which will cause for a reduction in power. Anything that can bend valves, negatively impact valve guides and seals, can lead to a reduction in compression, and thus in power production.
What are the chances of these happening? Will the signs be obvious or not really?
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      05-02-2012, 02:11 AM   #4
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Out of the scenarios you've listed, the money shift is the one that would be most concerning. Bouncing off the limiter is just fine, so long as you have pegged the accelerator down and are just letting bounce of the limiter non-stop (which unless you're crazy, you'd never do). Accidental reving to "redline" on a cold engine is the least concerning, as the M3 adjusts it based on engine temperature.

As to the money shift, you have the potential for all types of damage, depending on the severity. There's the possibility of damage to the main bearings, con-rods, valves, lots of stuff.

If you're concerned about compression loss, just do a compression test, but it'll be a PITA accessing the aft most cylinders on each bank.
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      05-02-2012, 05:46 AM   #5
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The engine has temperature senders and a reduced redline when it is cold. No need to worry about over-revving a cold engine.

The money shift is a different issue. If you downshift instead of upshift, you may learn a very expensive lesson. It has happened on some E36M3s. It did not seem to happen when the cars were fairly new, like less than 5 years old. At some point after that, the shift linkage began to wear, the clutch began to wear, the detent bushings in the side of the trans began to wear (and not guide the shifter into gear as well), and the cars were sold to younger and less experienced drivers who wanted to play racer. And the money shifts became more common.
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      05-02-2012, 09:36 AM   #6
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DCT owner. Now what about daily downshifts but not money shifts? Say every time your coming to a light I like to downshift from 3 to 2 then I let the car go to 1st. Or on the highway I'll downshift from 5th to 4th (hitting around 6-7 rpms) to pass and then shifting back up. Is this a huge wear?
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      05-02-2012, 10:30 AM   #7
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How does one "accidentally" hit redline with a cold engine?
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      05-02-2012, 10:34 AM   #8
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Most of that 20 hp you're talking about is just the individual dyno and all the variabilities involved in making a run. Unless a car is well out of the normal range its probably making pretty close to the same hp as any other car of the same exact type.

I'll give you an example. Back when I got my 3G Dodge diesel it was among the first made with the new engine type. A local diesel shop had a dyno day and 4 of us ran our similarly new trucks with the roughly the same low mileage on that dyno in less than an hour with the shop owner driving the vehicles on the dyno and trying his best to use exactly the same procedure. Because there was a lot of interest in what the trucks would do he ran each one 3 times while on the rollers and averaged the results. All four trucks fell within a 4 hp range. A few months later I rolled by to pick up some parts and at that time he had then run a number of further trucks on the dyno and he told me that they seemed to be falling into the low 220s to low 240s range. Notice how you have a range of about 20 hp on the same dyno but different days? You can pretty much figure that all of them were making close to the same power.
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      05-03-2012, 11:12 AM   #9
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Quote:
Originally Posted by Nicname View Post
DCT owner. Now what about daily downshifts but not money shifts? Say every time your coming to a light I like to downshift from 3 to 2 then I let the car go to 1st. Or on the highway I'll downshift from 5th to 4th (hitting around 6-7 rpms) to pass and then shifting back up. Is this a huge wear?
The DCT isn't supposed to let you do anything harmful. If you shouldn't make that shift, it should just ignore your request.
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      05-03-2012, 03:56 PM   #10
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what is a money shift?
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      05-03-2012, 04:35 PM   #11
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Money shifting is like sasquatch..the stories have been told but no one has actually seen it..

Its more of a feeble excuse to say "I picked DCT vs MT b/c that way i wont money shift"..ridiculous

OP just drive the car..and dont worry so much...
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      05-03-2012, 05:22 PM   #12
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Quote:
Originally Posted by Meccos View Post
what is a money shift?
It's an accidental down shift that that results in broken components, a costly mistake that results in a lot of money required for repairs (bent valves, etc.). Example: you upshift from 4th to 5th gear, but hit 3rd accidentally or shift from 3rd to 4th, but accidentally go into 2nd (the more common one), etc.. The rev-limiter isn't going to save you from a mechanical over-rev of this nature.
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      05-04-2012, 11:17 AM   #13
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Quote:
Originally Posted by hieu1004 View Post
It's an accidental down shift that that results in broken components, a costly mistake that results in a lot of money required for repairs (bent valves, etc.). Example: you upshift from 4th to 5th gear, but hit 3rd accidentally or shift from 3rd to 4th, but accidentally go into 2nd (the more common one), etc.. The rev-limiter isn't going to save you from a mechanical over-rev of this nature.
ya i dont see this being a problem in the dct
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      05-04-2012, 11:43 AM   #14
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Quote:
Originally Posted by M3Denver View Post
ya i dont see this being a problem in the dct
Correct. It's a concern for manual transmissions.
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      05-04-2012, 11:59 AM   #15
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Quote:
Originally Posted by M3Denver View Post
ya i dont see this being a problem in the dct
My buddy turbocharged his previous car and let his friend race it and he money shifted 3 to 2 instead of 3 to 4. Blew the engine to smithereens.

How he missed the 3-4 shift, I don't know.
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      05-04-2012, 12:02 PM   #16
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Quote:
Originally Posted by KJ View Post
My buddy turbocharged his previous car and let his friend race it and he money shifted 3 to 2 instead of 3 to 4. Blew the engine to smithereens.

How he missed the 3-4 shift, I don't know.
Some cars have gates that are very close.

I haven't driven one, but I hear the RSX has been pretty notorious from kids money shifting.
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      05-04-2012, 12:07 PM   #17
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Quote:
Originally Posted by hieu1004 View Post
Some cars have gates that are very close.

I haven't driven one, but I hear the RSX has been pretty notorious from kids money shifting.
OK OK, I'll give his friend a partial pass on this one, it was an RSX! LOL
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      05-04-2012, 12:14 PM   #18
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i thought a money shift was one where you have quick hands and quick feet like your auditioning for the fast and furious and really bang it home. kinda like a money shot its not a bad thing but a well executed shift, or load depending on the term.
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      05-04-2012, 12:16 PM   #19
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money shift is confirmed to be a NOT good thing.
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      05-04-2012, 12:53 PM   #20
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The engine has temperature senders and a reduced redline when it is cold. No need to worry about over-revving a cold engine.
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      05-06-2012, 11:56 PM   #21
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Quote:
Originally Posted by Jamie430 View Post
The engine has temperature senders and a reduced redline when it is cold. No need to worry about over-revving a cold engine.
Not true..

It will let you rev up to about 6K on an cold engine. Way too high. I don't go over 3000 RPM until the oil is atleast 160F. Then gradually raise RPM as temp raises.
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      05-07-2012, 05:07 AM   #22
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Quote:
Originally Posted by Mike Benvo View Post
Not true..

It will let you rev up to about 6K on an cold engine. Way too high. I don't go over 3000 RPM until the oil is atleast 160F. Then gradually raise RPM as temp raises.
Definitely agree - anyone who relies on the variable red line as a source of useful should think again....this reminds me of the mis-translation from German to English, in the E46 SMG manual...."the shift lights indicate the optimum up-shift revs"......erm no, they dont.

Over-revving when cold (and that means anything less than normal operating temperature) is the quickest way to ruin your engine, either catastrophically (something breaks, or a head gasket pops) or by rapidly increasing wear.
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