Author Topic: M42 single mass VS M20 single mass conversion (Read 97604 times)

DesktopDave · « **Reply #45 on:** March 11, 2010, 04:05:51 PM »

I have a late model 325i downstairs, and an earlier 325. When I do my swap I'll verify fit and part numbers. Just waiting on a cheap lift to appear on Pittsburgh CL...

Warsteiner · « **Reply #46 on:** March 11, 2010, 10:49:34 PM »

I have a lightweight M20 single mass in my car and I weighed it at 10.75-11 lbs. It is possible. I will also have 2 or 3 lightweight single mass M20 flywheels for sale shortly just like mine. These bolt right in with no problem. I'll post when I'm ready. If 2 or 3 people are interested let me know now. I still need to figure out a price.
I think that mine was a '87 or '88 325i clutch kit and new flywheel bolts. You retain the M42 starter.

4banger · « **Reply #47 on:** March 11, 2010, 11:06:44 PM »

Quote from: Warsteiner;89331

I have a lightweight M20 single mass in my car and I weighed it at 10.75-11 lbs. It is possible. I will also have 2 or 3 lightweight single mass M20 flywheels for sale shortly just like mine. These bolt right in with no problem. I'll post when I'm ready. If 2 or 3 people are interested let me know now. I still need to figure out a price.
I think that mine was a '87 or '88 325i clutch kit and new flywheel bolts. You retain the M42 starter.

id be interested. hell id even drive to pick it up. gives me a excuse to come with in range of AC. plus i have some friends in the belmarw/neptune area i havnt seen in years

Bracky · « **Reply #48 on:** March 13, 2010, 09:04:17 PM »

Could a 325e clutch and pressure plate work or does it have to be a 325i??

Bracky · « **Reply #49 on:** March 14, 2010, 03:17:36 PM »

harvey2 · « **Reply #50 on:** March 18, 2010, 12:40:57 PM »

Quote from: Bracky;89411

Could a 325e clutch and pressure plate work or does it have to be a 325i??

I tried to figure this one out just by looking at part numbers and found it confusing. Pelican Parts (whose website makes browsing quite easy) shows 3 different clutch disk part numbers depending on production dates, with changes occurring on Aug/Sept 85 and April/May 86. BMWfans shows 4 disk part numbers, with changes on Sept '85 and May '86 which agrees with Pelican. But they also show an additional part number with the designation For Vehicles with: 325 (V002A) = Yes. I don't understand this note at all.

It is this last part number that matches what Pelican is actually offering for the 325i, which implies that later 325e with SM flywheel could indeed use the 325i disk.

Now, looking at the pressure plate part numbers on BMWfans, there is a change at May 1986, with different pns before and after. Pelican shows the same pressure plate for 325e up to April '86 as is used in the 325i. I get the impression that this date, April '86/May '86 is when the 325e changed from single mass to dual mass flywheel.

Not sure if any of this helps, but bottom line is to find someone who has hands-on experience with your year of car for the final word.

harvey2 · « **Reply #51 on:** March 24, 2010, 12:42:20 PM »

This is an update on my flywheel conversion project. Previous info is in post#42 of this thread.

The car is back on the road and working smoothly. The clutch pedal feels exactly right, engagement and disengagement is perfectly smooth with no issues. There is zero noise, like chatter for example, during idle or any other time. The starter works perfectly with no issues. My idle is very smooth, perhaps slightly better than it used to be, but that may be my imagination. So there seems to be no drama and no issues after installation.

To be clear, I did not do the install, my favorite BMW independent shop handled it. If there were issues, I would have heard about them.

Now, as far as improvement to the car is concerned, I was not blown away, but it was better, no question. It is safe to say that my expectations, after many months of preparation and reading other's comments, got a bit too high. I was expecting a major difference in the speed at which the engine changes revs between shifts, and I was expecting a big change in the feel of acceleration in first and second. These expectations were wrong.

On my first drive with the new setup, there is no question the car feels lighter and livelier accelerating from a stop. So the improvement is obvious, just not as big as I was hoping. I expected to have to relearn how to drive due to the light flywheel spinning down much faster between shifts, but its not like that. Sure, it spins down noticeably faster, but not dramatically so, and adapting to it was so easy that it happened subconsciously with no effort at all. Some posters have described the change as "waking up" the car. Yes, that is a good description. But it doesn't "transform" the car.

I notice that I can re-engage the clutch on up-shifts just a bit quicker as the rev-matching happens just a bit quicker. That is a definite grin generator.

So, my advice to those E30-M42/318is owners who want to go to a lighter flywheel...don't be afraid of using a 13.5 lb M20 flywheel (along with the M20 clutch plate and disk) as this weight is clearly fine for street use. So much so that I wonder why they didn't fit this sort of thing in the factory those many years ago.

autox320 · « **Reply #52 on:** March 25, 2010, 02:27:58 PM »

So I found the easy way for me. They have a thread in this forum. here, dynotech motorsports

emailed
http://www.dynotechonline.com

complete kit ran me $535

12 lb lightened M20 flywheel (with M42 starter ring gear)
325 clutch kit
shorter flywheel bolts
longer slave cylinder push rod

They have the all in one solution and cost wasn't bad in my book.

dude8383 · « **Reply #53 on:** March 25, 2010, 09:08:59 PM »

Quote from: harvey2;89957

This is an update on my flywheel conversion project. Previous info is in post#42 of this thread.

The car is back on the road and working smoothly. The clutch pedal feels exactly right, engagement and disengagement is perfectly smooth with no issues. There is zero noise, like chatter for example, during idle or any other time. The starter works perfectly with no issues. My idle is very smooth, perhaps slightly better than it used to be, but that may be my imagination. So there seems to be no drama and no issues after installation.

To be clear, I did not do the install, my favorite BMW independent shop handled it. If there were issues, I would have heard about them.

Now, as far as improvement to the car is concerned, I was not blown away, but it was better, no question. It is safe to say that my expectations, after many months of preparation and reading other's comments, got a bit too high. I was expecting a major difference in the speed at which the engine changes revs between shifts, and I was expecting a big change in the feel of acceleration in first and second. These expectations were wrong.

On my first drive with the new setup, there is no question the car feels lighter and livelier accelerating from a stop. So the improvement is obvious, just not as big as I was hoping. I expected to have to relearn how to drive due to the light flywheel spinning down much faster between shifts, but its not like that. Sure, it spins down noticeably faster, but not dramatically so, and adapting to it was so easy that it happened subconsciously with no effort at all. Some posters have described the change as "waking up" the car. Yes, that is a good description. But it doesn't "transform" the car.

I notice that I can re-engage the clutch on up-shifts just a bit quicker as the rev-matching happens just a bit quicker. That is a definite grin generator.

So, my advice to those E30-M42/318is owners who want to go to a lighter flywheel...don't be afraid of using a 13.5 lb M20 flywheel (along with the M20 clutch plate and disk) as this weight is clearly fine for street use. So much so that I wonder why they didn't fit this sort of thing in the factory those many years ago.

You should really consider pairing this up with a chip. I have to admit when I did this swap for a friend of mine (achtungE30) I noticed that it didn't feel like my car did.

Quote from: autox320;90012

So I found the easy way for me. They have a thread in this forum. here, dynotech motorsports

emailed
http://www.dynotechonline.com

complete kit ran me $535

lightened M20 flywheel (with M42 starter ring gear)
325 clutch kit
shorter flywheel bolts
longer slave cylinder push rod

They have the all in one solution and cost wasn't bad in my book.
http://img339.imageshack.us/img339/7352/dsc05768s.jpg
http://img179.imageshack.us/img179/1415/dsc05767v.jpg

That sir is AWESOME. I'm glad someone is offering a whole kit now. What does the flywheel weigh?

harvey2 · « **Reply #54 on:** March 25, 2010, 09:45:59 PM »

Quote from: dude8383;90034

You should really consider pairing this up with a chip. I have to admit when I did this swap for a friend of mine (achtungE30) I noticed that it didn't feel like my car did.

Do you mean that your car feels better or his does? What are the important differences between the two?

I wonder how yours and mine would compare? I already had the DySylva EAT chip for 93 octane installed, so my car was already pretty lively before the swap. One other thing I did at the same time as the FW swap was to replace a 4.10 open diff with a 4.27 LSD. I wonder if the limited slip diff is slightly more lossy. Wanna race?

I did a dyno run before the swap, and we measured 125HP and 115 ft-lbs at the wheels, so it was healthy. Now it is noticeably livelier again.

dude8383 · « **Reply #55 on:** March 25, 2010, 10:57:19 PM »

Well the car in my signature doesn't have an m42 but my old red car did.

The main difference between my old car and his old car was that he didn't have a chip and mine did. It just didn't feel as sluggish anymore. It's hard to describe the feeling b/c it's been nearly 3yrs since I took the red one apart.

I drove the car with a stock flywheel for 2yrs and to me it was a big improvement when I installed the lighter flywheel and chip.

A 4.27 lsd will definitely make things a bit more interesting but you'll probably experience some discomfort when driving on the highway b/c of the higher rpm's. If the car is mostly a toy and see's the track more often, then this is an excellent upgrade.

Those are pretty strong numbers for a little m42b18

Even though I've long since moved over to the 2.5l 24v engine, I still have a soft spot for m42's. In fact when I have more time than I know what to do with, I will build myself a little stroker!

Quote from: harvey2;90036

Do you mean that your car feels better or his does? What are the important differences between the two?

I wonder how yours and mine would compare? I already had the DySylva EAT chip for 93 octane installed, so my car was already pretty lively before the swap. One other thing I did at the same time as the FW swap was to replace a 4.10 open diff with a 4.27 LSD. I wonder if the limited slip diff is slightly more lossy. Wanna race?

I did a dyno run before the swap, and we measured 125HP and 115 ft-lbs at the wheels, so it was healthy. Now it is noticeably livelier again.

autox320 · « **Reply #56 on:** March 26, 2010, 02:47:24 AM »

Quote from: dude8383;90034

That sir is AWESOME. I'm glad someone is offering a whole kit now. What does the flywheel weigh?

Edited post, 12 lbs

Bracky · « **Reply #57 on:** March 26, 2010, 03:27:29 PM »

Quote from: harvey2;89670

I tried to figure this one out just by looking at part numbers and found it confusing. Pelican Parts (whose website makes browsing quite easy) shows 3 different clutch disk part numbers depending on production dates, with changes occurring on Aug/Sept 85 and April/May 86. BMWfans shows 4 disk part numbers, with changes on Sept '85 and May '86 which agrees with Pelican. But they also show an additional part number with the designation For Vehicles with: 325 (V002A) = Yes. I don't understand this note at all.

It is this last part number that matches what Pelican is actually offering for the 325i, which implies that later 325e with SM flywheel could indeed use the 325i disk.

Now, looking at the pressure plate part numbers on BMWfans, there is a change at May 1986, with different pns before and after. Pelican shows the same pressure plate for 325e up to April '86 as is used in the 325i. I get the impression that this date, April '86/May '86 is when the 325e changed from single mass to dual mass flywheel.

Not sure if any of this helps, but bottom line is to find someone who has hands-on experience with your year of car for the final word.

Yeh too confusing but cheers anyway

Does anyone know the difference between the 325 clutch and the 320/323 part as i've found this but unsure if there is a difference in fitment or would I be correct in assuming the pressure plate is weaker/softer??
its listed as:
FITS BMW E30 320i 323i 1983 TO 1991
228mm DIA PLATE
Any help would be appreciated and my apologies for keep asking random questions about the clutch but the cheepest i can find a 325 cluch near me is nearly �200!!!! as i already have a barely worn in stage 1 cluch i dont want to throw nearly �600 down the drain for a mod that I've done before and have had good results but not worth that sort of cash and also cant afford trial and error approach.

CO318is · « **Reply #58 on:** October 18, 2010, 01:03:07 PM »

I just bought the used single mass m42 flywheel off of the classifieds here and I was wondering if anyone knows the lowest weight I can have it machined down to. Going through this thread I saw 13 pounds, is that what I should do?

NisseJ�rnet · « **Reply #59 on:** November 25, 2010, 06:25:06 PM »

Easiest way:

M20 flywheel, mill down the engine side of the flywheel a bit to get clearence
M20 starter
M20 flywheel bolts (dont forget the big spacer between the flywheel and bolts!)
M20 clutch

Done!