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Old 03-17-2011, 07:33 PM
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Anyone put a smaller turbo on a 617a + 4-speed combo?

I'm trying to track down the source of the low-rpm vibrations in my 240D 3.0T and my dad (B.S. in Mech. Eng. and phD in Combustion from MIT, used to build and race cars) says they're from the engine lugging. Now, I don't understand why it would lug and higher speeds than the 616. He said it was cause of the turbo.

Now, since a smaller turbo should spool up faster, I imagine it would lug at lower speeds. Has anyone tried this? Or does anyone maybe have the shift points of a non-turbo 617 for comparison?

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Old 03-17-2011, 07:37 PM
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It's probably not the lugging but the actual low rpm. So don't run low rpms.
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Old 03-17-2011, 07:51 PM
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Originally Posted by aaa View Post
It's probably not the lugging but the actual low rpm. So don't run low rpms.
I'm not sure I follow. How can low engine speed cause vibrations if it's not lugging? And my biggest problem is that I have to run second uncomfortably high before the vibrations stop.
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Old 03-17-2011, 09:04 PM
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Define lugging. I don't think getting more power down low will change the vibration, I think it's the cylinders pushing harder at a certain rpm that causes the vibrations.

If it's doing this over 2000rpm I'd think it's unbalanced somehow.
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Old 03-17-2011, 10:18 PM
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Define lugging. I don't think getting more power down low will change the vibration, I think it's the cylinders pushing harder at a certain rpm that causes the vibrations.

If it's doing this over 2000rpm I'd think it's unbalanced somehow.
Well, I don't have a tach yet, so I'm not sure exactly how fast the engine is going, but I can tell you that a machinist told me that the flywheel is neutrally balanced.
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Old 03-18-2011, 10:45 PM
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without a tach you can look up the gear ratios for your trans and rear and figure what the engine speed will be for a given mph. You should drive it and note when you have vibrations, noting also if it is in all gears. Then figure what rpm's the engine is doing at the vibration points. You should also bring it up to vibration speed, and ease of the throttle, and see if the vibration goes away. If so lugging it well could be. I do not think lugging is your problem though. I would suspect a driveline vibration, or engine imbalance. Was this engine mated to a automatic? If so then it is likely the flexplate may not have had the same balance as the flywheel you are now using.

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