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So my engine is stock except for a IPD street performance cam. I was thinking about lightening the fly wheel. Don't need anything extreme but looking for a little more livelier engine. So I ask the all knowing. Should I bother lightening it? If so what would be a good weight to go to?
Thanks for your time
Marc
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Is this in the new 142 you picked up?
Anywho, my 8 bolt flywheel is lightened to 18lbs and it is very noticeably better than my 6 bolt one that's currently in my '68. I'd love the 18lb one over the stock on any day of the week.
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If you do mostly highway driving, leave it stock, especially if you have a 5 speed. If you are mostly driving around town, lighten the flywheel, get it rebalanced & don't forget to take the pressure plate in for balancing too.
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Agree. Less weight makes it spin up faster, more weight gives it momentum for cruising. That is why Volvo gave it the weight it has, otherwise they would have made it as light (lower cost, higher profit) as they could have. Ideally you want a flywheel that can shift weight as required (similar to a centrifugal speed governer you often find on industrial machinery), but that is too complex and expensive for a consumer product.
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I have an aluminum flywheel on one of mine (8 pounds, I think it is), and I can't tell the difference between that and the stock one at cruise. It's crossing parking lots in first gear that gets a little touchy.
In any case, I don't think you can safely take off enough mass from a stock flywheel to bother anything.
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Agreed with Phil.
When your foot is off the clutch pedal, the whole damn car acts as a flywheel. As I mentioned, the effect of a lightened wheel is felt in the bottom gears, not direct.
Volvo used a large flywheel to improve the idle quality. Some Toyota engines, like the Tercel 1500 (?) used a wheel of over thirty pounds. Made for a near stall-less clutch take-up and a dead smooth idle. Many marine diesels use a large wheel, whereas the truck version of the same engine uses a much smaller one. It is mostly a vibration dampening effect in respect of the marine transmissions.
Lighten the flywheel. It works.
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Lighten the flywheel. It works.
You & Phil are right, lighter flywheels means more acceleration, but practicality has to be considered.
Example: My B20B 142S has a D-Type M41 with a 4.1 diff & 205x60/15 tyres. I found with the lightened stock flywheel that it was harder to take off from a standstill, especially uphill & I couldn't keep the car in 5th gear as much as I would have liked, so I put the stock one back in. Now if I was to put a 4.56 diff in to my car or a T5 gearbox with a much lower 1st gear I would automatically put the lightened flywheel back in.
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"I found with the lightened stock flywheel that it was harder to take off from a standstill, especially uphill & I couldn't keep the car in 5th gear as much as I would have liked...."
This may sound argumentative, but although I understand the first problem, I certainly do not understand the second. At highway speeds in OD, a lightened flywheel should be of very little consequence... virtually undetectable via seat of the pants, IMO.
Gary L
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1971 142E ITB racer, 1973 1800ES, 2002 S60 T5
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Your right, it's not that significant. What have you got in your racer?
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The Improved Touring ruleset prohibits lightened flywheels. However, you can use any clutch assembly that will bolt up to the stock flywheel and work with the stock transmission input shaft. So yes, the clutch assembly is all aluminum with the exception of the diaphram fingers and splined drive collar.
I do not know the exact weight of the whole assembly, but it is undoubtedly several pounds lighter than the stock clutch. Similarly, I do not know the exact cost of the whole assembly, but it is undoubtedly several times that of a stock clutch. :)
Gary L
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1971 142E ITB racer, 1973 1800ES, 2002 S60 T5
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As I recall it saved about 6 lbs.
Marc
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That sneeky Bob Griffith and his race car parts!
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Yeah, that clutch is a nice piece of work. And obviously it is not a fragile device... I've put nearly 1000 racing miles on it myself, all on the same disk.
IIRC, Kerr said he used up one disk while he had the car, but that was the direct result of slipping the clutch while putting the car on the trailer.
Gary L
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1971 142E ITB racer, 1973 1800ES, 2002 S60 T5
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Sounds like a neat bit of gear, photo anybody?
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I have a couple pictures of it going together. I am not sure on how to post them. It is pretty amazing on how simple it is. If someone can tell me how to post a picture (not in the photo gallary)I will do so.
Marc
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I assume that means you already have them posted somewhere online? If not, email them to me and I'll get them up on OVT and post them in here for you.
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Could've sworn I had photo's of the clutch assembly, but I can't find them if I do.
Will take some shots next time it's exposed, but with any luck that will be a while!
Gary L
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1971 142E ITB racer, 1973 1800ES, 2002 S60 T5
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The equivalent weight is proportional to the distance from the center squared (or is it to the 3rd power, can't bother confirming the exact equation). That's why the effect is greater when removing weight from the rim rather than the inside (you also remove more weight faster due to a longer cutting circumference). Yes, your drive shaft and what not does act like a flywheel, but the diameter is much smaller than that of the flywheel.
This discussion is getting too technical for this forum, and for the application (every day driving) it is sufficient to just go with people's personal impressions/experiences. If you want to build a racer, find advice from race car builders.
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I have been lightening Volvo flywheels for over twenty years, and every one of them made a big difference. I remove material to within about .060-.080 inch of the ring gear, and then down to nearly the clutch cover bolt holes. That takes around four pounds out. Like Phil says, weight from the rim makes the biggest difference. I found a website that explained the physics behind this, and it compared the weight removed to the equivalent weight of the car, and it is most pronounced in the lower gears, and then tapers to parity in the direct gear. I can't remember the site, but what they said matched my experience.
Have the wheel rebalanced of course, as most times you will cut into and remove factory balance holes.
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I think it makes a really noticeable difference in the lower gears. I'm taking another two to the machine shop this week, in fact. My guy generally takes a shallow step off it beginning immediately outboard of the clutch bolt holes, and then tapers that down to the thickness of the ring gear on the outer edge. Some can be carved from the thick outboard section on the motor side as well.
This brings the flywheel down to 16-17 lbs instead of the stock 22+, but the effect is greater than you might think, as all the weight came off the outside. I've had 4-5 done for various motors and none has felt at all uncomfortably light for street use.
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posted by
someone claiming to be 145volvowayne
on
Wed May 10 06:28 CST 2006 [ RELATED]
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If I took mine to my local machine shop what kind of instructions could I give them? What would be a fair price to have mine turned down?
Thanks,
Wayne
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A lot of shops won't do them because of liability issues. If a flywheel comes apart, it can cause a lot of damage to both people and machinery. Look for a shop that regularly builds racing motors and they'll know what to do.
My shop charges $170 for lightening, resurfacing and balancing.
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Hi Phil,
Do you have any pictures of your modified flywheels?
Thanks,
Craig
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Most of the weight on this one came off the engine side -- only pic I've got, I think.
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theoretical question here:
If I was doing a ligthly modified motor, say 150 hp. should i go with a vpd aluminum flywheel? I am under the assumption that it will help the motor rev faster/easier and otherwise not make too much difference in day-to-day drivability. Is this correct?
CU
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First off, 150 HP does not come from a lightly modified motor -- at least not if you want to maintain good tractability. Have a look at what goes into a VPD SP kit as one example of what it takes. None of it's radical stuff, but there's a lot to it.
For any particular customer's budget, I try to spend the money where it will do the most good. An aluminum flywheel costs roughly $300 more than having a stock flywheel lightened. Are we better off spending that $300 on better machine work, additional porting, buying a good header, a modern cam kit, or on the flywheel?
On a 150-160 HP budget, the aluminum flywheel usually doesn't make sense to me. On a 180+ HP budget, it fits in much better.
Does that make sense?
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Hi Phil, Thank you. I am getting a vpd SP kit. I miss spoke, when I said "lightly modified" I guess I meant no forced induction or modifications that would make it more a of a track car than a street car. I probably should've asked if the aluminum flywheel is a worthwhile addition if I was going with the sp kit and for good streetable drivability. I really wanted to know what the advantages were for street use, if they would be noticable, and if there are any disadvantages.
I guess you have answered my question.
Thank you for your insight.
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If I was doing a ligthly modified motor, say 150 hp. should i go with a vpd aluminum flywheel?
No. It's too light. Just lighten up the stock flywheel. The VPD flywheel starts to become worthwhile on a racer where it does triple duty by helping the brakes(the rear brakes have to slow the car + the engine down) & helping the gearbox achieve quicker shifts.
What intake & exhaust do you have? The next thing you want after the VPD SP kit is probably a bigger camshaft or maybe fuel injection depending if you want more power or economy.
The time to get a VPD flywheel is after you have 4.56 gears in the diff with an LSD.
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Thank you! This helps a lot and goes to the old addage that, just because something is a hi-performance aprt it doesn't mean it will work well on the street.
I ma not sure yet abou the exhaust, bu tbelieve I am going with the twin Mikuni set up.
the 150 Hp is plenty for me as I am mostly using the car as a regular driver, (though not my daily driver, untill my mitsubishi dies,... if ever).
The brakes and suspension are already done, the body and interior are in very good shape.
CU
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