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Lightened flywheels, worthwhile?
sdh2903 - 19/10/15 at 07:06 PM

I've never used a lightened flywheel before and they are very popular for my donor MX5 1.8 engine. Now googling brings up various good reviews and also bad with reports of engine bogging at low revs etc. I am planning on a little N/A tuning and wondered if a lightened flywheel would complement this? Are the reports of engine bogging as noticeable in such a lightweight car?

There are varying weights available with some radically lightened and some more moderate, the general consensus being a 10lb flywheel (down from stock 20lb) seems to be the middle ground of choice.

Any opinions from the collective if a lightened fly is a worthwhile purchase for a 7?

r1_pete - 19/10/15 at 07:22 PM

I've one in the E Type, the engine is more lively, but, at tick over there is a considerable rattle from the gearbox due to the flywheel not smoothing out the pulses as effectively as a stock one, its not a faulty box, its a rebuilt 5 speed Getrag.

If I ever need to split the engine and box I would put the stock flywheel back in.

[Edited on 19/10/15 by r1_pete]

mark chandler - 19/10/15 at 07:41 PM

On my DB7 i6 I removed the DMF, a whopping 38kg built up and replaced with a lightened 3.6 flywheel (22kg down to 18kg) with helix 6 finger paddle clutch with sprung centre and had professionally balanced.

Car idles if anything more smoothly, very noticeable difference in first and second (acceleration spin in first now) car feels much more lively go for it.

Pete, I also have a getrag box, the 290, if yours rattle now you must have an imbalance as a straight 6 is naturally smooth.

I used Andy @ http://www.bassetdownbalancing.co.uk, fantastic job, gave him the flywheel and cover.


Note, bike engines rev up like fury as the have very little mass to accelerate = light flywheel.

Regards Mark

CosKev3 - 19/10/15 at 07:47 PM

I fitted a billet very light one in my pug 306 Rallye and that made a nice improvement in how it revved out.

Bogging down wise it did make the clutch feel more like a paddle clutch,soon got used to it tbh.

snapper - 19/10/15 at 08:09 PM

I run lightweights on 2 of my pintos, in a lightweight car even with long duration cams I found no disadvantage only benefits

l5tuy - 19/10/15 at 08:58 PM

Aright mate?

I bought and fitted one from MX5 parts, i bought it based on reviews and a recent episode of wheeler dealers....... The positives for me were worth the risk of lumpy idle etc.

If you do get one make sure they supply high tensile bolts for the clutch plate bracket.

Stu

coyoteboy - 19/10/15 at 10:55 PM

Gains in power are generally tiny and primarily in 1st/2ND. In higher gears the gains are pretty much negligible. The grin from light fw revving out of gear probably outweighs the annoyance at lack of gain

steve m - 20/10/15 at 07:46 AM

I had run one for years in my 7 on the old xflow, and the only fault I would find is it needed a slightly higher tickover as the car would shake at 800-900 rpm

performance in all 4 gears was brisk, and the engine would rev to 7k very easily

however I could not get the flywheel off the engine when I changed engines, so I have an old standard one in the 7 at the moment, and can really feel the difference in how the car drives

I will put the lightened one back in

steve

r1_pete - 20/10/15 at 08:06 AM

quote:
Originally posted by mark chandler

Pete, I also have a getrag box, the 290, if yours rattle now you must have an imbalance as a straight 6 is naturally smooth.

Regards Mark


Hi Mark, the engine had an £11,000 (yes three 0's) just before I got it, including a full dynamic balance clutch flywheel, crank rods etc. with it being a long stroke engine, idling at 600rpm it shakes the cogs a bit, if I set the tickover to 800 it goes away, its currently at 700rpm which seems the best compromise.

snapper - 20/10/15 at 12:22 PM

I would always use a steel light flywheel not a home lightened cast one and always fit ARP flywheel bolts
Both the ones I fitted also had crank to flywheel dowls fitted

luke2152 - 20/10/15 at 08:30 PM

I have a stock mx5 one lightened and balanced. Not an expensive job. None of the structure has been removed only the large ring of material on the outer edge which serves only to add weight to the flywheel. It makes the engine free rev much quicker matching revs on downshifts. and also somewhat easier to stall. Doesn't affect idle. Only really improves performance in 1st and 2nd.

sdh2903 - 20/10/15 at 09:06 PM

Cheers for the input guys.

I'd seen the mx5parts one but a bit rich for me. I've seen a couple for around the 200 mark. The ones I've been looking at are chromoly steel. Particularly this one from tegiwa but am waiting to find out exactly how light it is.

http://www.tegiwaimports.com/select-car/mazda/mx5/drivetrain/rpc-lightweight-chromoly-flywheel-mazda-mx5-na-nb-1-8.html