Rv8 lighter flywheels

[Pupp]

Anyone come across any good aftermarket options... may need a new one and would like to lose a few lb in the process? How much is possible before the idle etc becomes a problem?

[JonRB]

Personally I wouldn't want to go any lighter than thatever is fitted to my 1997 Chimaera 500. It is very blippable and has very little flywheel effect. You wouldn't want even less in my opinion.

My Corrado has a Fidanza flywheel, so I am speaking from some experience although admittedly on a different engine.

[rev-erend]

I'm sure there might be more knowledgeable people than me on this .. but I believe TVR already lightened the flywheels ....

The std flywheel is about 32lbs and the one on my car was around 18lbs.

Take a look here :

http://www.v8tuner.co.uk/category.php?id=20

They have Aluminum (11lbs) and steel (27lbs) .. I thing the 11lbs jobbie would be no fun at all around town !

[TVRleigh_BBWR]

I would also not want to go the Aluminum route in a TVR as they can shatter, and your not got much protection in a TVR.

[Graham]

TVRleigh_BBWR said:

I would also not want to go the Aluminum route in a TVR as they can shatter, and your not got much protection in a TVR.

I'd have thought much less chance of a purpose designed ally one shattering than a cast iron one thats been machined down..

[trackcar]

I've got a lightened flywheel on the back of the 5 litre to go in the V8S .. also a prototype twin plate clutch .. the whole thing is very light .. i can probably get some stats off the engineer who built it for me if you like?

[Graham]

trackcar said:

I've got a lightened flywheel on the back of the 5 litre to go in the V8S .. also a prototype twin plate clutch .. the whole thing is very light .. i can probably get some stats off the engineer who built it for me if you like?

I might be interested in that as we run a stock griff 500 flywheel and clutch on the tuscan

cheers

G

[Pupp]

Cheers guys, don't want to go 'fragile' as it's still a road motor at the end of the day but I would like a sharper response and don't mind lumpy low down running. Reason I'm thinking about changing is I have some clutch judder that's worsening and when the clutch was changed only a month or two ago, it was noticed the flywheel face was pretty blue... I'm assuming refacing is not an option?

[JonRB]

There are better ways to get improved response than just lightening the flywheel. Have you done all the usual things yet?

[Pupp]

JonRB said:

There are better ways to get improved response than just lightening the flywheel. Have you done all the usual things yet?

Getting there... focusing on improving/modding stuff as it needs changing etc, hence thinking if there's any gains to be had, I'll do it now

[rev-erend]

Pupp said:

Cheers guys, don't want to go 'fragile' as it's still a road motor at the end of the day but I would like a sharper response and don't mind lumpy low down running. Reason I'm thinking about changing is I have some clutch judder that's worsening and when the clutch was changed only a month or two ago, it was noticed the flywheel face was pretty blue... I'm assuming refacing is not an option?

I would think a skim would be OK .. best call a RV8 expert like V8 Developments.

[Speed eight]

Using a 9lbs weight flywheel and even a wild cam you will achieve a 900/1000Rpm tickover speed.
This style of flywheel will incorporate a steel friction plate within it.

[trackcar]

Indeed .. the thing in your favour is you have a V8 twin plane crank, so 4 firing puses per engine rev .. even the lightest flywheel will be smooth enough with that pushing it round.

ive never understood this thing about light flywheels harming engine smoothness .. the apparent smoothness you feel is down to the torque reaction of each engine pulse not being able to accelerate the crank/flywheel .. so the heavier the rotating mas the MORE the impact into the cabin surely? .. I have never been able to get my head around something which is likely to accelerate faster per firing pulse therefore imparting less torque reaction back through the engine mounts into the chassis making a car less smooth.

If someone can adequately explain this i would be most impressed!

[JonRB]

I can't explain it, but have experienced it. My Corrado VR6 is definitely lumpier and more prone to stall with the lighter flywheel.

Vince at Stealth (who installed it and did all the other mods too) says I'll be losing a little torque at lower revs due to the flywheel too. Not sure how that works personally.

Edit: Well, I say it's lumpier, but since I had a more aggressive cam fitted at the same time and also the dual-tract inlet manifold, I guess I can't really do an objective "before and after" as there are too many variables.

Edited by JonRB on Wednesday 10th October 15:18

[Speed eight]

With the Rover V8 engine the cheapest and easiest way to gain a throttle response is by the lightening of the rotational mass...in this case the flywheel and or clutch unit.
There is no reason for this to affect the tick over speed smoothness or desire for the engine to "stall" whatsoever.
This would be down to some other factor.
Even with the above and a radical camshaft profile there should be no problem.
If the engine vacuum falls to say 5 or 6 inches, then further work would be needed....but I do not think that this is going that way.

Edited by Speed eight on Wednesday 10th October 15:32

[JonRB]

Just to reiterate my earlier post, my Chimaera 500 has almost instant throttle response and the engine revs instantly rise and fall with the merest blip of the thottle. I love it.

If there are any differences in the flywheels used in the various incarnations of the RV8 then I'd recommend the flywheel off the 500, otherwise I don't see what you would hope to gain by going beyond that.

[Speed eight]

Faster throttle response.

[JonRB]

Speed eight said:

Faster throttle response.

Well, yes, but I meant that I was saying that I was suprised you would want much more than that.

[Steve_T]

JonRB said:

I can't explain it, but have experienced it. My Corrado VR6 is definitely lumpier and more prone to stall with the lighter flywheel.

Ok folks, see if this makes any sense. The engine generates a torque, which is transferred to the mounts as a force causing compression or extension, when the engine's speed speed alters. The force applied is in proportion to the rate of change of the rotational speed of the engine. You can see this when you blip the throttle on a big engine, as it rocks on the mountings. Thinking about idling, each time the engine fires, its speed alters. A heavier crank is harder to accelerate, therefore when a heavier crank is used the engine speed varies less at idle and therefore the engine appears smoother. An engine is more prone to stall with a lighter flywheel, simply because there is less momentum built up in the engine.

Steve.

[Talkwrench]

All that Steve says above is true and affects smoothness at idle but the biggest factor in maintaining smoothness is the momentum the flywheel has when the engine hits a compression stroke. A light flywheel with little momentum will slow dramatically as a piston hits compression. A heavy flywheel keeps going and contains the necessary energy to complete the compression stroke.