Between the Light-Flywheel or the Light-Pully, which one shows dyno tested gains??
Also, when running turbo, can either mod allow for faster spooling giving you less lag-time???
Finally, can one use both systems with boosted power?? Meaning being to lighted can cause problems???

Thanks.

 

You're saving more weight with a lightened flywheel, so that frees up more hp than a lightened crank pulley. An under-drive pulley gains a little by not turning the alternator as fast, but I think gains there are pretty minimal. Yes, you can use both on a TC'ed car. You don't want to use an under-sized crank pulley on a SC'ed car for obvious reasons.

It is interesting to note that the hp gain from a lightened flywheel is proportional to engine rotational acceleration. So you will see all your gains in 1st and 2nd gear where acceleration is highest. The higher the gear the less effective a lightened flywheel is.

 

Very interesting. The light weight Fly, gives you greater acceleration on your lower gears... I guess up-top the rotational is not that noticable. Thanks for the feedback.

 

I have put UR UDP's on customer cars, and honestly, I dont see the big deal - but some UDP owners swear by them - "it revs faster" etc etc... i wonder if its not just justification for the $ though I dont run one and could get it for free, too lazy to install haha , granted id pick up some hp

Lightened flywheel I also had on my car personally, and have done on a customers car - revs quick yes, but for the money... whew - IMO not worth it... but if you have the money and nothing else to spend it on , yeah its great - car revs fast in neutral with udp and flywheel, but.. dont think the gains are there for a what do they cost now 500ish or something? i removed mine while ago.

 

Yeah, a lightened flywheel or udp will always make a noticeable seat-of-the-pants difference in rev speed in neutral, when the flywheel inertia makes up a significant portion of the total inertia being acclerated. That fools people into thinking it will be the same improvement when in gear, but it just isn't so. Once you're in gear and have to accelerate the whole car, not just the flywheel, the effect of the lightened flywheel drops into insignificance (except maybe in first gear).

 

As far as the pulley goes, some guy here just dynoed with the addition of and RVM UDP and I think he gained 8 hp. I'm pretty sure the graph is is the group deal forum under the RVM group deal.

Needless to say, I ordered one yesterday. They're only $75 shipped. Thats about 1 hp per 10 dollars, same as a y-pipe.

 

8 hp is an astonishing number. That would have to be due almost entirely to moment of inertia reduction, since alternator and power steering pump loads are minimal during a dyno run. I haven't crunched any numbers to do a sanity check, but I am highly skeptical.

 

I don't know man. I think that the 8 hp was gained at the peak too so it probably isn't a moment of inertia thing. Just find that thread and look at the dyno graph. Its all there for you to see.