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Lightweight Flywheel: Carbs vs. FI (tii)


2002#3

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Gang,

The numerous FAQ discussions re: lightweight flywheels appear to me to apply to carb'd cars.  I have not seen anything re: tii's.  I am installing a 245 transmission into my '74 tii and am wondering, "While I'm at it...".

     Q1:  How about with a tii?  Anyone? 

     Q2:  Would the results be the same, e.g., faster up/down rpm, faster out of turns, slower up hills, getting used to having to shifting more quickly while rpm are up, etc.?

 

Now that I think about it, maybe putting one into my '70 ti-wannabe (dual 40 Solexes) might be a better idea.

     Q3:  Thoughts?

Thanks,

Larry

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The difference between carbs and a Tii should be the same.

 

Can't speak to M10, but on an S14, in the M3 world, standard vs. Evo III , many complain about a less smooth idle, and the transmission rattling at idle. I did the calculations on the Hp difference, and found it takes about 8Hp more to spin up the stock vs. the Evo III.

 

 

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Lightened flywheels are for racing, where idle doesn't matter and you stay in the high rpm range where it makes a difference.

 

On a street driven car your better off sticking with the stock flywheel, so your engine idles properly. Spend your money on a nice 3.91 lsd to go with that getrag 245. 

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1 hour ago, 2002iii said:

Lightened flywheels are for racing, where idle doesn't matter and you stay in the high rpm range where it makes a difference.

 

On a street driven car your better off sticking with the stock flywheel, so your engine idles properly. Spend your money on a nice 3.91 lsd to go with that getrag 245. 


have you driven a 02 with a l/w flywheel? If so which one and how much lighter than stock? Aluminum or steel lightened? 
 

I have a stock flywheel that was lightened.  I did it when I went with a 245. Wouldn’t have it any other way.  Revs faster, idles great and no chatter or drivability issues.  
 

Also for my driving...and ALOT of 02 gurus...a 3.91 is not an upgrade...I stuck with the 3.64 and love it.   I also have a modded m10 motor so it has some balls. Just did a 900 mile road trip...cruising comfortably at 80-85.  Try that with a 3.91...

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1976 BMW 2002 Fjord Blue Ireland Stage II • Bilstein Sports • Ireland Headers • Weber 38 • 292 Cam • 9.5:1 Pistons • 123Tune Bluetooth 15" BBS

2016 BMW 535i M Sport

1964 Volvo Amazon Wagon
http://www.project2002.com

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JBR flywheel on my '72 tii, it was great.  I saw no disadvantage.  We're not talking about some multi-plate F1 / moto clutch.  I used a completely stock (new) clutch with the JBR flywheel, idled great, ran great, did everything great.  All it does is make the engine more responsive- if you ask for more acceleration, it gives you more acceleration sooner, if you ask for more deceleration, it gives it to you sooner.  That's it, it's more responsive.  It's not moto like at all, you're not stalling trying to pull away from stop lights.  It's not slower up hill (not sure where that came from.)  It's better everywhere.  Depending on the clutch you use, the clutch can rattle- but that's a function of the clutch, not the flywheel.  Use a bog-stock clutch, it's going to sound stock.  Clutchmasters clutch will probably rattle.

 

The stock flywheel is 20 pounds?  The JB is 8.  It is amazing.  I had one in the '72 tii with the little bit built motor, I've had them behind 3 s54's, and I just installed one on the s14 in my 2002.  When my wife gets in the car to drive it, she has no issues with the light flywheel.  Again, this isn't a full blown, F1 / moto clutch.  It's the regular system, just lighter.  It's not harder to drive, it's easier.  You know what the heavy flywheel is like?  It's like the goddam 'clutch delay valve' the factory installs in the newer manual cars.  That's exactly what it's like.  It sucks.  The light flywheel is exactly like taking the clutch delay valve out- it all works like it's supposed to.  Please stop spreading misinformation about this.  The light flywheel is wonderful.

 

I suppose if you can't drive a manual, then a heavy flywheel is better.  Just like the goddam clutch delay valve.  But learn how to drive a manual, get a light flywheel, and revel in how much faster your engine spins up when your foot is flat.

 

I've literally bought 4 aluminum flywheels for street driven cars.  Paid retail for every single one.

Edited by irdave
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Dave.

'76, totally stock. Completely.

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I’m with Dave, and agree completely - I have none of the ‘downsides’ cited. 
 

I have the 8lb JBR flywheel in my 245, mated with  M3 pressure plate & Sachs Tii clutch (all 228mm). 3.91 LSD in back. It’s super, would not hesitate to do it again.  It idles well (900 rpm, 304 Schrick, dual 40s), and revs quick, with no rattling ever. I really like the responsiveness, it’s SO much better.

 

Maybe I should join the naysayers, so no one else finds out how great this is...

 

... and with the OD 5-speed I can cruise at 90 all day at a relatively low 4100rpm,  just sayin’.

Edited by visionaut
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Where we goin’? … I’ll drive…
There are some who call me... Tom too         v i s i o n a u t i k s.com   

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Try one, you might like it...

 

I went so far as to remove the flywheel entirely, using a 7" puck clutch.

 

I soon realized that the crank has so much mass and inertia that it was all

joy, and figured that the next engine I built I'd try lightening the crank, too.

 

Some like it, some hate it.  I don't think it took much off my lap time,

but DAMN was it fun.  And far more reliable than the stock clutch.

 

Stock 215 clutch plate and disc weigh about #15, 215 flywheel something like #18.

And it's all distant from the crank centerline.

 

t

first one's free!

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"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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2 hours ago, visionaut said:

I’m with Dave, and agree completely - I have none of the ‘downsides’ cited. 
 

I have the 8lb JBR flywheel in my 245, mated with  M3 pressure plate & Sachs Tii clutch (all 228mm). 3.91 LSD in back. It’s super, would not hesitate to do it again.  It idles well (900 rpm, 304 Schrick, dual 40s), and revs quick, with no rattling ever. I really like the responsiveness, it’s SO much better.

 

Maybe I should join the naysayers, so no one else finds out how great this is...

 

... and with the OD 5-speed I can cruise at 90 all day at a relatively low 4100rpm,  just sayin’.

+1 - Same setup here but on my '73 Tii - made the change when I went to the 245 as well. No negatives whatsoever to date and that's 20K miles or so. Definitely more responsive and if I was to do it all again, it'd be a no-brainer this time around.

1973 2002tii Taiga, 2763376 

1969 2002 Chamonix, 1666774

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I'm getting a couple of flywheels lightened for project engines, nows the time.

Also switching worn double row timing chains to single row timing chains and sprockets on both. But admit the single row chains are not so much about reducing rotating mass as it is about cost. I have most of that stuff on the shelf here.

But hey, if the single row stuff is good enough for IE race engines its probably good enough for my "barely qualifies as a street build"  engines. 

Dont really see a downside. ?

 

Physics is physics, mass and inertia oh my!

 

 

Edited by tech71
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76 2002 Survivor

71 2002 Franzi

85 318i  Doris

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1 hour ago, tech71 said:

I'm getting a couple of flywheels lightened for project engines, nows the time.

Also switching worn double row timing chains to single row timing chains and sprockets on both. But admit the single row chains are not so much about reducing rotating mass as it is about cost. I have most of that stuff on the shelf here.

But hey, if the single row stuff is good enough for IE race engines its good enough for me.

Dont really see a downside. ?

 

Physics is physics, mass and inertia oh my!

 

Don't forget reduced friction!

 

I did the same on my rebuild, but it was mainly about cost lol.

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John Baas

1976 BMW 2002

2001 BMW M5

My Blog!

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When I re-did my '73's motor, I was very conservative WRT flywheel lightening--I had our local machine shop--who specializes in building performance engines--take off 2-3 lbs from around the edges--crescent-shaped bites from around the edge, leaving the clutch bolt holes intact with plenty of meat around each.  It was explained to me that taking weight off the edge vs the center changed the rotating mass's center point and thus required less material removal.  

 

I fitted 9.5 pistons and a 284 Schrick, and the idle is as smooth as to be expected with a 32/36 Weber--the idle with my 1 bbl Solex on the 69 has spoiled me for a smooth idle.  The rebuild was 64k miles ago and all has been well ever since...

 

mike

 

.

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'69 Nevada sunroof-Wolfgang-bought new
'73 Sahara sunroof-Ludwig-since '78
'91 Brillantrot 318is sunroof-Georg Friederich 
Fiat Topolini (Benito & Luigi), Renault 4CVs (Anatole, Lucky Pierre, Brigette) & Kermit, the Bugeye Sprite

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