My 240D 3.0T 4-speed Swap - Page 5 - PeachParts Mercedes-Benz Forum

JEBalles · #61 01-10-2011, 04:51 PM

Quote:

Originally Posted by DeliveryValve

OK since you are having no vibration issues, I was randomly thinking the engine was sitting differently. Hence the w126 arms question. But now you stated you are using the 240 arms, it still could be the case.

.

Probably should mention that I am having some vibration issues. Can't tell you the engine speeds, but it's usually between 20 and 30 mph in 3rd gear and 30 and 40 mph in 4th gear with the 3.69.

It also, however, depends on the location of the accelerator. If I have it depressed about 1/3 of the way down, I get the vibes. More or less than that and they go away. In other words, if I drive with a lead foot, I don't get any vibrations.

In other news, I finally put in the auto 240 crossmember. Helped greatly with the idle vibrations, but didn't affect the other vibes. Granted, I am still using my worn-out manual transmission mount.

ForcedInduction · #62 01-11-2011, 01:56 AM

That is natural vibration from lugging the engine. Automatics don't feel it because the torque converter is a very effective damper.

t walgamuth · #63 01-11-2011, 05:59 AM

In mine there are certain vibrations which can be felt at certain rpm and they are somewhere in the middle ranges. Not severe but noticable. I have the 38# 300d flywheel in mine.

leathermang · #64 01-11-2011, 11:59 AM

Amen to the torque converter being a great vibration damper.

I have always advised against putting a manual trans behind a turbo 617 engine.. I have more confidence in the MB Factory... in that there is some reason THEY did not marry up those two items.... or at least in the years in which we are discussing..

But it would be nice to get rid of as many vibrations as possible so I am going to mention that in the 616 manual .. .and the updated maintenance manual for these cars..
they mention checking to be sure the correct Vibration dampers are installed on the drive shaft. AND the recommended COMBO ( like most other things on these cars ) was modified over the years....

There are specific " SOFT" and " REGULAR " ( round rubber 6 hole ) dampers in the driveshafts... and in some cases they recommend BOTH .. like one in the front and the other in the rear..... so a person going in for new ones on a project like this might not know they needed the " 616 Manual trans" combo instead of what is listed as correct for their car.

winmutt · #65 01-11-2011, 02:57 PM

Quote:

Originally Posted by JEBalles

Probably should mention that I am having some vibration issues. Can't tell you the engine speeds, but it's usually between 20 and 30 mph in 3rd gear and 30 and 40 mph in 4th gear with the 3.69.

It also, however, depends on the location of the accelerator. If I have it depressed about 1/3 of the way down, I get the vibes. More or less than that and they go away. In other words, if I drive with a lead foot, I don't get any vibrations.

Uh thats your rear diff being unhappy with you.

leathermang · #66 01-11-2011, 03:18 PM

Quote:

Originally Posted by winmutt

Uh thats your rear diff being unhappy with you.

UH, how do you get to that conclusion ?

ForcedInduction · #67 01-11-2011, 09:58 PM

Quote:

Originally Posted by leathermang

I have always advised against putting a manual trans behind a turbo 617 engine.

Though there is no sound reason against it.

Installing the correct driveline damper from a 617-4m greatly absorbs vibration, especially at highway speeds, it will not stop vibrations caused by lugging the engine from 1000-1600rpm.

Part number 123 411 01 47 072, unfortunately its an unavailable part from MB new so the only option is 2nd hand.
Also note, a cut 240D can't have it installed because of the large diameter and its match balanced to its host driveshaft. A factory 300D-4m driveline must be used.

leathermang · #68 01-11-2011, 10:50 PM

Quote:

Originally Posted by ForcedInduction

Though there is no sound reason against it....

it will not stop vibrations caused by lugging the engine from 1000-1600rpm.
.

For those watching ... I am assuming that you chose 1600 rpm as the approx point at which the Turbo Kicks In.. which would then provide the power to keep the engine from lugging...

So explain how one with a manual trans avoids lugging the engine in that rpm range WITHOUT Slipping the clutch ( excessively and thus wearing it out prematurely)......

With a torque converter the stall speed can be set to allow the engine to get to that rpm before introducing the load which would cause lugging.

Why did MB not produce cars of this era with the combination of turbo and manual trans ? ( Since you are rejecting my hypothesis )...

ForcedInduction · #69 01-12-2011, 12:50 AM

Quote:

Originally Posted by leathermang

For those watching ... I am assuming that you chose 1600 rpm as the approx point at which the Turbo Kicks In.

No, I can start the turbo boosting from 1000rpm if I lug. 13psi by 1500rpm is rather easy though its tough on the driveline and turbo.

Quote:

So explain how one with a manual trans avoids lugging the engine in that rpm range WITHOUT Slipping the clutch

Choosing the correct gear for the conditions. 1st and 2nd gear don't have enough load for the engine to lug (even if you start in 2nd, which I never do). In 3rd and 4th its "operator error" if the engine is lugged.

Quote:

( excessively and thus wearing it out prematurely)......

My $25 clutch has been in place over 5 years without trouble and is showing no signs of wear. Even with the additional load of having a 3.07 diff.

Quote:

With a torque converter the stall speed can be set to allow the engine to get to that rpm before introducing the load which would cause lugging.

The stock 1500rpm speed is lugging. MB figured this out (a little late in the game) and fixed the problem in late-1984 with the 1800rpm converter.
Thats why I'm looking for a 2100rpm converter to fit my 300D.

Quote:

Why did MB not produce cars of this era with the combination of turbo and manual trans ?

The USA/Japan market buying these cars didn't want a manual and the 300D turbo and 300CD were only sold in the USA (300SD USA/Japan). The 240D was the only model offered here with manual devices to minimize introductory cost to the brand. The same way manufacturers today still advertise their cars "Starting at $xx,xxx". Why R&D a drivetrain for "lazy Americans" that don't want it?

The only difference between a 300D-4m and a 300D-turbo with a retrofit 4-m (and correct driveshaft+damper) is 37hp. A euro 300D-4m lugs and vibrates at the same rpm.

300D85 · #70 01-21-2011, 04:26 PM

how'd you come up with the exact 37hp#?

SirNik84 · #71 01-21-2011, 04:46 PM

88hp non-turbo engine, 125hp turbo engine. the difference is 37hp

http://en.wikipedia.org/wiki/OM617

winmutt · #72 01-21-2011, 05:38 PM

Quote:

Originally Posted by ForcedInduction

Part number 123 411 01 47 072, unfortunately its an unavailable part from MB new so the only option is 2nd hand.

I can't remember but someone posted a link to the OEM who still sells them....

ForcedInduction · #73 01-21-2011, 05:39 PM

Yes. Like any car with a manual the driver simply has to learn how to drive the way that best utilizes the engine. NA can lug easier because it doesn't have much torque across the RPM range. Turbo is happier 1600+ because the turbo responds much better and the 40% more torque accelerates the vehicle faster.

JEBalles · #74 01-21-2011, 06:14 PM

Well, I can't be sure since I don't have a tach, but I'm shifting at the same recommended shift points as the 240, and I still have the 3.69 rear end, so shouldn't it not be lugging since the 617 has more power? Also, I can still accelerate at those speeds in those gears without vibes as I long as I don't press the pedal passed that ~1/3 point at which the vibes start.

Also, I read that using the heavier 617 flywheel doesn't solve the vibe problem, and as winmutt just told me, the lighter 616 flywheel = more HP, less torque (although that didn't make sense to me once the clutch is engaged, so if it's true, someone has to explain it to me). I'm also not sure how using the 3.69 diff could cause the vibes, either.

ForcedInduction · #75 01-21-2011, 06:30 PM

Quote:

Originally Posted by JEBalles

I'm shifting at the same recommended shift points as the 240

There is no such thing. The dots on the speedo are the maximum downshift speeds.

Quote:

Also, I read that using the heavier 617 flywheel doesn't solve the vibe problem, and as winmutt just told me, the lighter 616 flywheel = more HP, less torque (although that didn't make sense to me once the clutch is engaged, so if it's true, someone has to explain it to me).

More flywheel mass means more absorbed and released energy; Lighter allows more power directly to the wheels and the engine can accelerate faster. Heavier keeps the engine's momentum high so more torque is available between the power strokes.

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