Can someone explain what the Under Drive Pully does

bluestyle55 · 02-27-2010, 09:42 AM

Would someone mind quickly explaining what the crank drive pully does? What are the performance gains to be had on getting a light weight one? What are the risks of installing them?

bluestyle55 · 02-27-2010, 09:46 AM

So there is a underdrive and crank... Whats the difference?

MightyBobo · 02-27-2010, 09:54 AM

Same thing. Theres multiple versions you'll find:

Stock crank pulley
Lightweight crank pulley
Underdrive pulley

-Stock is exactly that.
-Lightweight is the same diameter as a stock pulley - just lighter, to free up a small fraction of power.
-Underdrive is a smaller diameter pulley (usually lighter, also) - this allows less parasitic energy to be used to spin your accessory belt (and, of course, all accessories THAT turns - alternator, AC compressor, etc). Obviously, those are not advised if you have a lot of power going to your sound system

. How much power you can get from that varies by the motor...on an LS1 it was worth 5ish WHP. This car, probably less.

bluestyle55 · 02-27-2010, 10:07 AM

thx dude

CBRich · 02-27-2010, 11:24 AM

You asked about risks and there are some of those too. The risks aren't due to the pulley itself but the installation procedure. It requires putting a lot of force on the stock pulley to get it off. This can cause problems with the seal and oil leakage.

02-27-2010, 09:42 AM	#1 (permalink)
bluestyle55 Premium Member Join Date: Apr 2009 Location: Pa Posts: 194 Drives: 09 Nissan 370z B 6M Rep Power: 18	Can someone explain what the Under Drive Pully does Would someone mind quickly explaining what the crank drive pully does? What are the performance gains to be had on getting a light weight one? What are the risks of installing them? __________________ 2009 370z 6MT Touring w/ Sport Pkg \| Invidia Gemini CBE\| Stillen G3 CAI \| ERZ HFC's \|X-Pel Clear Bra \| 20% Tint

02-27-2010, 09:46 AM	#2 (permalink)
bluestyle55 Premium Member Join Date: Apr 2009 Location: Pa Posts: 194 Drives: 09 Nissan 370z B 6M Rep Power: 18	So there is a underdrive and crank... Whats the difference? __________________ 2009 370z 6MT Touring w/ Sport Pkg \| Invidia Gemini CBE\| Stillen G3 CAI \| ERZ HFC's \|X-Pel Clear Bra \| 20% Tint

02-27-2010, 09:54 AM	#3 (permalink)
MightyBobo A True Z Fanatic Join Date: Feb 2009 Location: Las Vegas, NV Posts: 8,465 Drives: No cars; only bikes Rep Power: 54	Same thing. Theres multiple versions you'll find: Stock crank pulley Lightweight crank pulley Underdrive pulley -Stock is exactly that. -Lightweight is the same diameter as a stock pulley - just lighter, to free up a small fraction of power. -Underdrive is a smaller diameter pulley (usually lighter, also) - this allows less parasitic energy to be used to spin your accessory belt (and, of course, all accessories THAT turns - alternator, AC compressor, etc). Obviously, those are not advised if you have a lot of power going to your sound system . How much power you can get from that varies by the motor...on an LS1 it was worth 5ish WHP. This car, probably less. __________________ I don't own a car anymore.

02-27-2010, 10:07 AM	#4 (permalink)
bluestyle55 Premium Member Join Date: Apr 2009 Location: Pa Posts: 194 Drives: 09 Nissan 370z B 6M Rep Power: 18	thx dude __________________ 2009 370z 6MT Touring w/ Sport Pkg \| Invidia Gemini CBE\| Stillen G3 CAI \| ERZ HFC's \|X-Pel Clear Bra \| 20% Tint

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02-27-2010, 11:24 AM	#5 (permalink)
CBRich A True Z Fanatic Join Date: Apr 2009 Location: SC Posts: 2,464 Drives: 370Z Rep Power: 546	You asked about risks and there are some of those too. The risks aren't due to the pulley itself but the installation procedure. It requires putting a lot of force on the stock pulley to get it off. This can cause problems with the seal and oil leakage.