• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

lightweight flywheel-do or don't

Share this page

hi,
i am planning to use the stock rear end 3.7:1 with a phantom grip lsd and a w58 toyota supra 5-spd. yes, major suspension mods in the works. most of this is still in the works (planning, designing, reasearching). i already have adjustable front and read anti roll bars. 1" front, 5/8" rear. these are the rally/road revington tr antiroll bars from england. i have not decided on how soft to run the front and rear springs yet. revingtons' package with these bars are 450# fronts, 160# rears with 5.5" ground clearance.
i understand however that i would get better GRIP with softer springs, however bottoming with a tr4 becomes an issue with soft springs in a fast, rough road condition.
rob
 
My thought was....

The lower your 1st gear is, the lighter your flywheel can be.

I don't know what the stock ratio is on a TR4 or what it will be after you put the Supra 5-speed in. (tires can influence your choice also)

BTW..Phantom Grips destroy differentials. They are total crap and the company that produces them should be burned to the ground.....END OF STORY
 
[ QUOTE ]
My thought was....
The lower your 1st gear is, the lighter your flywheel can be....

[/ QUOTE ]

Probably true if you mean "geared lower" (which is numerically higher).
But most folks looking at light flywheels are also interested in close-ratio gearboxes (which means that first gear isn't so "geared down" and is numerically higher).
And many race motors have less torque at low RPMs, which makes things even worse.

There is no real solution to this....other than careful slipping of the clutch to get rolling.

By the way, I lightened my steel flywheel by carefully removing material from near the outer diameter (where it makes the most difference). I used big radius blends on the cuts to reduce any stress concentration.
I only took off about 3 pounds, but I think it helps acceleration a bit (and it was free /ubbthreads/images/graemlins/cool.gif )

I use a thick piece of cast-off Lexan as a scattershield.

I've heard very mixed reviews about the Phntom-Grip limited slip diff modification.....some of the front-drive guys I know have complained of rapid spider gear wear.
 
phantom grips are crap?
really. i didn't know that. are they more like a locker that snaps in and out?
rob
 
hi,
i wouldn't use lexan. i doesn't x-ray very well when it is imbedded in your leg or fragments are in your leg. 4340 is the stuff.
rob
 
oops! /ubbthreads/images/graemlins/blush.gif
4130
rob
 
[ QUOTE ]

Probably true if you mean "geared lower" (which is numerically higher).
But most folks looking at light flywheels are also interested in close-ratio gearboxes (which means that first gear isn't so "geared down" and is numerically higher).
And many race motors have less torque at low RPMs, which makes things even worse.


[/ QUOTE ]
YES.......All true......I should have been more specific.
My own situation (Auto-X & fast road use) MGA 1622 engine 10 to 1 compression

270 degree cam----11 lb Flywheel-----3.73 rear end-----1500 lb car (wet+me)----MGB heavy duty clutch---Tran-X LSD(clutch type)

The standard box has 3.64 2.21 1.37 1.0
The close ratio box 2.45 1.62 1.27 1.0

Street tire launch (standard box) 3000 rpm (C/R box) 4000 rpm

While the standard box is easy to drive (feels stock) on the street, the C/R box requires some slippage.
The Elva has gobs of low down torque & is out of it's cam @ 6400 rpm's
I don't know the hp or torque.
 
I got my quaife from a fella running an Elva Courier... He said it made him nervous in high speed sweepers but I've had no issues whatsoever. Perhaps he didn't have it well set up, I dunno.
Yeah, I got it for $1K ten years ago!
 
What I heard is that light cars like Elva, Sprite, Turner etc. have very sensitive butts & wiggle more.
(They like smooth clutch packs)

Heavier cars MGB, TR 2-4 & AH are not so much disturbed by the operation of the torque sensing mechanism.

(The great thing about Quaife is that they are guaranteed INDEFINITELY to who ever manages to blow it up)

Also...You don't have to periodically replace clutch packs, goof around w/ ramp angles or be a chemist to properly figure out how much "slip" juice to add.
 
Really?? Quaifes are guaranteed for the life of the unit? That's amazing! Makes their $1350-1500 prices seem like a decent investment.
 
Quaife America Torque Biasing Differential Lifetime Warranty: Quaife America warrants each new Quaife ATB Differential against defects in manufacture, material, workmanship, and wear-out when used in the vehicle application for which it was originally designed, on any motor vehicle, under any and all operating conditions, including racing, for as long as the original purchaser, or any subsequent purchaser owns the differential

<font color="red"> I click & pasted the above from thier website.
 
Dave wrote: [ QUOTE ]
What I heard is that light cars like Elva, Sprite, Turner etc. have very sensitive butts & wiggle more.
(They like smooth clutch packs)

[/ QUOTE ]

Find an Elan driver with the original donut-type rear axles and try that out. Smooth... Hahahaaaaaa! "Snap!... SPROING!" sometimes followed by: "SH*T!"
 
Rob, I don't know what ratios are in the 5 speed box, but obviously a numerically high first gear ratio gives scope for a better launch, so makes lightening the flywheel more practical.
I feel this is not necessary for this type of event, however, as two things will help you do well: your driving ability and grippy tyres.
The tyres must get up to temp quickly, so if allowed by the class rules get Hoosier Autox, and if you have to have street legal tyres get the fattest, stickiest ones you can.
That and driving ability will make much more difference than spending a lot of money on engine development.
A limited slip diff is also going to help a lot, (remember you should break in a new lsd by driving around in figure 8s in an empty parking lots), and getting the best alignment and suspension settings will be very important; again more so than power. (Some toe-out at the front helps pull the car into the corner.)
All this is just my opinion, but the bottom line is I would not mess with the flywheel.
Cheers, Simon.
 
I didn't mess with mine, and I feel it's a much easier car to drive than my buddy's MR2 with lightened everything. It's obviously not as fast, but it's still quite peppy. I don't feel that the added mass is a real killer, but rather helps with making a solid launch (without stalling). It does make you slightly slower, especially in the lower gears, but I feel this is negligible.
 
Hope I don't repeat too much. Yes, go with lighter flywheel. But go with factory made if possible, just for accuracy, quality, etc.

You'll notice 3 things:
1. You'll kill it the first few times you begin to release the clutch. The engine has less rotating mass to keep on rotating.
2. It will spool up faster, yeah team!
3. The converse also applies. Your brakes don't have to slow the motor, compression will help you slow. Brake later (not at all), yeah team again!
 
For the record.......Go for it.

Get the 2 pound flywheel & everything else.

Later, if you discover the car is undrivable, you can adjust from there.

You have more than enough opportunity to be practical & responsible in the decisions you make daily.

Can you tell I just got back from the pub? /ubbthreads/images/graemlins/grin.gif
 
I lightened mine from 22 lbs to 15 lbs.
The engine has about 10-1 c.r. a slighty better cam, 7 degrees of cam advance, ceramic coated header, roller rockers, high flow stainless steel valaves, etc.
I keep the revs limited with a Pertronix Second strike to 6500 rpms.
All of this adds up to a very reposnive engine. But, the 7 degrees advance at the cam limits the power curve to max. at about 5000 revs.
Oh it will go to the red line, but especially in 3rd and 4th gear slowly.
 
well,
i talked to jack drews "uncle jack". he said that was one of the first things he'd do. he said it's in the top 3 mods that make the most difference to a tr4 motor. Darryl uprichard of racetorations said he would not shave much off a stock flywheel because of safety, but would go with a purpose built lightweight. i put the stock flywheel with ring gear on the scale, get this, a WHOPPING 30 LBS"! i would be taking 8-9 lbs off to get to 20 lbs. pressure plate 12 lbs, friction disc 2 lbs. best price on lightweight flywheel from ts import auto $335. i think i'll go for it when dollars available
rob
 
I had the flywheel cut down in my Street / Autocross Cortina from like 23 lb to 14 and change. It needs a slightly faster idle than before, and I stalled it a few times at first. It picks up revs quicker than before. all the weight was removed pretty much from the outside BTW

Its cheap and it works.
 
Back
Top