Performance Mods

[doggystyle]

i'd be careful about machining the factory flywheel as they have a tendency to explode under stress.. it costs(in nz anyway) about 150 bucks to have one made up at your local engineer unless you like the idea of having flywheel shrapenel embedded in your legs....

[Charles]

Depends how silly you go with them. A well machined flywheel is actually under less stress than the stocker because of the lower weight at the periphery. I have never seen a lightened Honda flywheel let go and I have seen a lot treated awefully badly. Not saying they won't but it is unlikely that machining the weight of the ring off the edge will cause failure. Just make sure that you do not go below the thinest point (Ie the area where the flywheel is thinest is the weakest). Machining excess weight from beyond the clutch surface is also never going to present a problem.

[QikLude]

yeah I agree with charles.
A 5.8kg factory flywheel has more than enough meat to last the distance.
Last weekend I completly destroyed my clutch bt the flywheel held up no problems...

I guess the phat sity flywheels are trying to give the cars that real phat torque feeling, which for factory isnt all that bad!

Cheers

[Michael]

The problem is the standard city turbo flywheel is cast metal. The surface of the metal is like a skin and makes it stronger. It is alot safer to lighten a turned flywheel rather than a cast one. Im going to get quotes on getting the cast one lightened and get a few opinions as to a safe amount to take off. Ill keep you posted.   Are there any hondas that dont have a cast metal flywheel? later civic etc? It may be safer to get a flywheel that isnt cast and lighten it.

Michael.

[QikLude]

as far as i know there all cast.

horrid damn things really.. hmm nice lightweight alloy one YUM!  :P

Jw

[Charles]

All honda flywheels are cast. The "skin" you refer to can be recreated after lightening and balancing by shotpeening, no big deal. .. There is no skin on the clutch side obviously.

There is still less stress on a lightened flywheel than on a stock job (unless you only skim the outside surface. However there is is debate against which is stonger standard cast or ground (with grain). By grinding and providing grain plus shotpeening you get better overall strength.

The other thing to consider is cryo treating. Cheap and effective (apparently, pretty hard to messure). But by reducing the random crystalline structure formed by byproducts of the casting process it increases strength. Look it up for more details.

[doggystyle]

but the fact remains that cast flywheels are full of imperfections regardless of shot peening etc, if your gonna spend the money its better to get one machined out if billet steel cos its by far stronger

[Charles]

If your gonna spend the money AND have got the money, sure get a billet wheel. If you have to do a clutch and need your flywheel balanced and surfaced lightening costs stuff all if not free with a definate performance gain and very little in the way of a downside.

Me, I'd save the cash and get my stocker lightened unless you are going extreme power and/or revs. The performance difference between a lightened flywheel and a custom job is minimal.

I have used both in the past and can honestly say that unless you are competing at the highest level where every tiny bit counts a lightened flywheel will suffice.

Honda's casting, forging and metalurgy is second to none and lightened flywheels under normal conditions are going to be fine. Spin the engine to 13000 rpms and it could be different, there would be nothing left of your city motor though if you did that.

I would personally be very dubious of a $150NZ "billet" flywheel which is the price you suggest people should be able to get them for.

[doggystyle]

thats how much it used to cost us to get rotory ones made at our local engineers we just took in our factory flywheel and tell him the wieght we wanted and he'd machine one up out of a piece of high pressure forged steel or though i do agree that hondas casting is good, i had a friend who used to race minis and they would blow flywheels all the time.. mind you that is old english tech

[Michael]

$150 would be an absolute bargain. I just had quotes just to lighten and balance the flywheel that were about $200. The original flywheel for a T2 weighs about 7kg. It was estimated that you could lighten it by about 1kg safely. This in the opinion of the machinests that I spoke to, would not be that noticeable on the street, and to lighten it as much as possible you need to get rid of the timing marks. All this considered, I have decided not to get the flywheel lightened as the expence and trouble of loosing the timing marks is not worth the performace gain.

Michael.

[QikLude]

I chewed lots of my prelude flywheel, and lost the timing marks.

What we did there tho, was put a dowel in the flywheel with a nice pointed end in it.
Its now MUCH more obvious that the factory timing mark.

Good idea if u ask me

[Charles]

Taking 1mm off a turbo 1 engine head increases compression from 8.48:1 to 9.16:1 (Around 9.3:1 on a turbo 2).

[BOOSTBOY]

Hey Charles,

Ive just got my heat back from being ported, it has been machined down to the indicators, there is about 1mm of indicator left.  Any idea what compression i'll be running?


G

[Charles]

If you cc it and let me know I can tell you. Stock is about 37cc