Clutch and Flywheel Recommendations for Street and Occasional Track

[Rockonp04]

Looking for advice on purchasing a light single mass flywheel and a clutch kit. Not looking to blow the bank but that will be easy to drive on the daily but will be fun to drive on the track.

I am planning to eventually do the 2.8l upgrade so I want to make sure the clutch kit will be able to hold up to the slight gain in HP. I think a stage 1 clutch kit will be all I need or even the stock kit will suffice.

Just looking for advice.

[roguetoaster]

Stock SMF with a stock clutch seems like a winner. Remember there's really no such thing as "Stage XYZ," and clutch assemblies have more practical rating systems.

[Rockonp04]

Stock SMF with a stock clutch seems like a winner. Remember there's really no such thing as "Stage XYZ," and clutch assemblies have more practical rating systems.

Yea I agree with your assessment. I always use finger quotes " " when I say stage 1. Lol. I agree with the stock clutch setup but I am leaning toward the lightened flywheel. I had one on my E36 M3 and it reved so nice. Any recommendations?

[bmwman91]

I HIGHLY recommend the RHD 7.4lb billet steel flywheel. Prior to this, I ran an M20 FW lightened 11lbs. But, the 7.4lb one is not only lighter, but it has much less mass at the outer perimeter, which makes a huge difference. It is a totally different feel, and far more freely revving. This is on an M42 engine, mind you. I had a little trouble with the idle at first, where it would stall due to lack of rotational inertia, but since I was getting a full custom tune done, we took care of that. In the case of the M20, I doubt it is an issue at all since you have a lot more overlap between power strokes. My 2.1L M42 makes ~200bhp / 165 ft-lbs, and a stock M20 clutch & PP are just fine. Hell, the PP weighs a lot more than the FW lol.

Here's the M20 FW, if you are curious. It is a fantastic price.

https://racehead.com.au/product/bmw-light-flywheel-m20/

Apparently they are listed as 8.5lbs now. Weird. Either I am remembering wrong, or they beefed something up. Also, which one you buy depends on your starter ring. The single- & dual-mass flywheels differed, so you need to verify what is in your car before buying.

[digger]

Anyone know if there is a rhd for m20 and 240mm clutch ?

[moatilliatta]

Stock SMF with a stock clutch seems like a winner. Remember there's really no such thing as "Stage XYZ," and clutch assemblies have more practical rating systems.

Another vote here.

Sachs HD pressure plate added if you’re feeling like you might track intensely more.

The SMF factory kit should have a sprung hub clutch disk.

And the back side of the SMF can be shaved if needed.

[Rockonp04]

I HIGHLY recommend the RHD 7.4lb billet steel flywheel. Prior to this, I ran an M20 FW lightened 11lbs. But, the 7.4lb one is not only lighter, but it has much less mass at the outer perimeter, which makes a huge difference. It is a totally different feel, and far more freely revving. This is on an M42 engine, mind you. I had a little trouble with the idle at first, where it would stall due to lack of rotational inertia, but since I was getting a full custom tune done, we took care of that. In the case of the M20, I doubt it is an issue at all since you have a lot more overlap between power strokes. My 2.1L M42 makes ~200bhp / 165 ft-lbs, and a stock M20 clutch & PP are just fine. Hell, the PP weighs a lot more than the FW lol.

Here's the M20 FW, if you are curious. It is a fantastic price.

https://racehead.com.au/product/bmw-light-flywheel-m20/

Apparently they are listed as 8.5lbs now. Weird. Either I am remembering wrong, or they beefed something up. Also, which one you buy depends on your starter ring. The single- & dual-mass flywheels differed, so you need to verify what is in your car before buying.

This looks like a cheaper alternative to the $500 plus aluminum flywheels out there. I'm leaning toward this option. I think chromoly would be a better option considering its stronger than aluminum.

[bmwman91]

Of the E30 LTW FW's I have seen, the RHD ones might be the best performers. Net FW weight is only part of the story. The real factor is WHERE that mass is located. The RHD design has removed all but the bare minimum of material from the outermost radii of the thing, which is enabled by the fact that it is a 1-piece design with integrated starter ring. The aluminum & modified stock ones have to keep a fair amount of metal out there to support the OEM starter ring. If you imagine two 10lb pieces of metal, one a large diameter thin disc of sheet metal and one a long rod of small diameter, think about which one will be harder to rotate if you tried to spin it by hand. The large thin sheet would obviously feel like it was resisting more, since its polar moment of inertia is a LOT larger than the skinny rod. Same deal with these flywheels.

[digger]

based on a CAD model i made of the RHD 228 flywheel the "Mass moment of inertia (MMOI) " is about ~35-40% of the OE m20 flywheel.
your typical lightened OE M20 FW will be ~60-65% MMOI of the unmolested OE m20 flywheel.

This means the RHD has about ~55-65% of the MMOI of a lightened m20 OE FW.

What is important is that in terms of overall inertia of the engine system considering the MMOI of whole rotating assemebly (crank, rod rotating mass, vibration damper+pulley, pressure plate, , crank gear, clutch disc etc but ignoring gearbox and driveline etc) swapping the m20 OE with RHD is a reduction of ~30% where the lightened OE is ~18% reduction

[Rockonp04]

based on a CAD model i made of the RHD 228 flywheel the "Mass moment of inertia (MMOI) " is about ~35-40% of the OE m20 flywheel.
your typical lightened OE M20 FW will be ~60-65% MMOI of the unmolested OE m20 flywheel.

This means the RHD has about ~55-65% of the MMOI of a lightened m20 OE FW.

What is important is that in terms of overall inertia of the engine system considering the MMOI of whole rotating assemebly (crank, rod rotating mass, vibration damper+pulley, pressure plate, , crank gear, clutch disc etc but ignoring gearbox and driveline etc) swapping the m20 OE with RHD is a reduction of ~30% where the lightened OE is ~18% reduction

Point taken on the where the mass is located. However, how is this flywheel during daily driving?

[digger]

Point taken on the where the mass is located. However, how is this flywheel during daily driving?

with a mild cam and stock style organic clutch it will be fine with appropriate tuning, i dont know if there are any users on here running on motronic to know how if it copes as far as idle control with A/C and general drievabiity as its not motronics forte.

It may make some noise but seems to be gearbox dependant as i know some G260 are ok even with the UUC alloy FW

for anyone interested i contacted Rama and he said those with m20 and G260 can use the following if they want the higher torque cpacity 240mm setup, it requires a different starter to suit the ring gear. this is probably the route im going to take as with bigger stroke etc it offsets it some. I already have the upgraded e28 M5 clutch

https://racehead.com.au/product/bmw-...54-heavy-duty/

[Rockonp04]

with a mild cam and stock style organic clutch it will be fine with appropriate tuning, i dont know if there are any users on here running on motronic to know how if it copes as far as idle control with A/C and general drievabiity as its not motronics forte.

It may make some noise but seems to be gearbox dependant as i know some G260 are ok even with the UUC alloy FW

for anyone interested i contacted Rama and he said those with m20 and G260 can use the following if they want the higher torque cpacity 240mm setup, it requires a different starter to suit the ring gear. this is probably the route im going to take as with bigger stroke etc it offsets it some. I already have the upgraded e28 M5 clutch

https://racehead.com.au/product/bmw-...54-heavy-duty/

I decided to pull the trigger. like the price and this won't be a daily driver just for hoons on the weekend so I am willing to take the risk. Price is much better than the aluminum flywheels out there. Thanks for all your advice and insight. Can't wait to get this thing installed.

[bmwman91]

Regarding tranny rattle and drivability, here's my experience. It's on an M42, and I'd assume that the M20 would be no worse, probably better in these regards.

Transmission rattle is significantly more noticeable than stock, but no worse than it was when I ran a lightened stock M20 FW. Drivability is fantastic. You will quickly get used to having to give it a bit more gas from a stop, maybe stalling it once or twice. I needed a shit load of tuning to get it to idle (and not stall coming off throttle), but I also have a VERY non-stock M42 lol. It needed a bunch of tuning anyway. Again, I'd expect the M20 to handle this better since it actually has power stroke overlap. In terms of moving drivability, it is amazingly better. Rev matches are almost effortless, shifting can be done faster since the crank speed will change more rapidly and overall it is one of the best mods I have ever done. I think that you will like it. Some people really hate the "coffee can full of rocks" noise that our transmissions make with lightweight flywheels, but other than making the car sound like a bucket of bolts at stop lights, it is not hurting anything. Hell, I sort of like it.

[JehTehsus]

I have an aluminum flywheel on my M20 stroker build... I love it. Motor is extremely snappy, definitely a big impact on making the car more fun to drive - it just feels super responsive. My buddy has a lightened steel flywheel on his build, which he told me he was quite happy with, and after he drove my car he said he is very seriously considering pulling the trans and swapping to an aluminum flywheel.

I have a bit of trans noise, but whether that is due to the flywheel or all the stripped sound dampening is an open question. I have had absolutely zero issues with driveabilty on the street, custom engine management as well though. In fact, I actually love it on the street, because feeling the engine just snap to where you want it on the heel toe downshift is so immensely satisfying after driving a stock M20, I drive my girlfriend nuts because I just constantly giggle to myself like an idiot.