Under Drive Pulley

[steve_vu]

Hi all ill start by intorducing myself long time reader but just recently became a contributing member, names steve, live in perth and own a series 2 VUSS with a few decent mods cam, heads, forged internals ect. Look forward to being part of the forum!

Back to my question, am currently chasing a few extra HP and looking into bigger heads, larger intake manifold and a few other things. I have seen a lot of people put 25% underdrive pulley kits on thier cars and am curious as to what sort of advantage/gains are to be had by installing one. I dont fully understand the concept other than it reducing the amount of load on the engine caused from power steering and aircon.

Any answers would be appreciated cheers!!

[peter b]

[QUOTE. I dont fully understand the concept other than it reducing the amount of load on the engine caused from power steering and aircon.

Any answers would be appreciated cheers!![/QUOTE]

You have answered it there. Less parasitic loss eg anything that runs of the drive belt use power to turn the item. in turn gives you a parasitic loss going the 25% under drive balancer reduces the parasitic loss and in turn you pick up a little bit of power but would be lucky to see 5 rear wheel horsepower

[steve_vu]

ok so thats basicly all there is to it, obvoiusly not to much to be achieved by installing one i have a mate who recently had one installed and claimed 10-15 hp increase so i thought it may be something worth doing.

Mabye the extra HP im chasing may result in some form of forced induction rather than minor N/A modifications :)

[peter b]

yeah you get to a certain point and unless you are going to increase cubic capacity other option is forced induction. The balancers are cheap but dont net massive gain. Yes there is a gain but is only marginal

[awesome _vzss]

It's a pretty good mod considering you do gain abit more power and remove abit of load off the engine.
And the kits aren't that expensive.

[surfwagon]

If you fit it yourself then it is not a bad bang for your buck to gain around 3-4rwkw (around $350 for a kit on ebay) but if paying someone to do it then not really worth the cost .
If btw you are getting a bigger cam fitted then definitely fit one then.



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senator http://www.ls1.com.au/forum/showthread.php?t=121025
dyno http://www.ls1.com.au/forum/showthread.php?t=137278
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[RB30X]

Just on this subject, I did the original article in the DIY section on the installation of these UD balancers but I'm trying to do the same thing to my current LS1 and I can't for the life of me undo the crankshaft bolt. I've tried the breaker bar on the nut and crank the engine over, even tried a rattle gun with an impact socket and she wont budge.

Any other tricks??

[duke5700]

Get a bigger rattle gun.. they take some shifting sometimes.

[CHe]

Just on this subject, I did the original article in the DIY section on the installation of these UD balancers but I'm trying to do the same thing to my current LS1 and I can't for the life of me undo the crankshaft bolt. I've tried the breaker bar on the nut and crank the engine over, even tried a rattle gun with an impact socket and she wont budge.

Any other tricks??

What happens when you try the breaker bar on the nut and crank the engine over? Does it bend/break the breaker bar or not turn over the engine?..

[steve_vu]

i do have a bigger cam already installed, but still running the standard pulley may look at doing it as its a cheap mod and something i can do myself.

[Rhc 1]

The power steering also has a fun trick of over heating and spraying your engine bay with fluid when you are pulling high revs for sustained periods. The under drive knocks the pump speed down by a worthwhile amount.

[sv300 - 75]

so it seems like a good little thing to do if you are already getting some other pulleys replaces (just worn out parts).
are there any other sorts of gains like, better fuel economy, lower engine temps?

and also are there any down sides? will my alternator still be able to power my sound system? i do have a decent system but i am not sure if changing the UD pulley will cause problems later.

any advice would be greatly appreciated

[daztheclipper]

I only had the bottom pulley changed to UDP, definately noticed that the engine seems to spin a lot more freely, it's on a WM and to date have had no issues whatsoever with alternator etc, and Caprices put a fair strain on the electrics. Get the Gatorback Goodyear belts as I have read elsewhere that cheaper belts can jump pulleys. Extra KWs? I did read somewhere that on a dyno a manual with UDP installed ended up with 5rwkw extra, not too sure about that but definately feels more willing to spin quicker. Thats my experience with it so far, would recommend it!!
Cheers


Sent via IPhone
Daz

[dogsballs]

worthwhile mod if you are pulling bits off the engine already (as you'll need to drop fluids and move rad etc to get puller on). also good to use an ARP replacement bolt as the OE are single use.

i noticed a bit more freeness in the revving and gain on strip.

sorta like upgrading springs, something relatively straight forward to do, gives some insurance.

[OVZ-346]

i have one on my ute i ONLY did it as to not over speed the accessories with higher engine operating rpm when racing the car

i diddnt give two hoots about the power gain if anything

[RB30X]

What happens when you try the breaker bar on the nut and crank the engine over? Does it bend/break the breaker bar or not turn over the engine?..

The breaker bar just loads up and bends, the engine lifts up a bit on its mounts and the starter comes to a stop.