03/04 Overdriving Crank Pulley Information needed

Tat98Cobra · Jul 20, 2004

Hey guys - just wondering if anyone had gone the overdriving route instead of just getting the smaller blower pulley. By overdriving of course, I mean getting a larger crank pulley so everything spins faster. Helps to reduce slippage as well. It workes really well on the old 98 d1sc setup

peace

Dr. Wu 2000 · Jul 20, 2004

Have not read anyone just doing that without the smaller blower pulley. Seems like it would add some power. Good question though.

Tat98Cobra · Jul 21, 2004

It really made a huge difference on the Centri. Just wondering if it would be just as effective on the roots style. A wise man once told me (Mike Dez) that the crank pulley is a much more effective way of raising boost

peace

Uncle Meat · Jul 21, 2004

There are guys out there running 2, 4, & 6lb lower pulleys. Some use a smaller blower pulley in conjunction with the larger crank pulley too! Problem with the lowers is they are harder to swap out initially than the upper pulley, plus they are more expensive. This and the need to go with a larger alternator pulley when using the 4 or 6lb lower because it ends up over-driving the accessories. Almost all the 03/04 guys still running the stock unported Eaton have found the stock lower pulley coupled with a 2.80 upper is the most economical combo for making power.

U.M.

Dr. Wu 2000 · Jul 21, 2004

thanks Meat

Tat98Cobra · Jul 21, 2004

Uncle Meat said:
There are guys out there running 2, 4, & 6lb lower pulleys. Some use a smaller blower pulley in conjunction with the larger crank pulley too! Problem with the lowers is they are harder to swap out initially than the upper pulley, plus they are more expensive. This and the need to go with a larger alternator pulley when using the 4 or 6lb lower because it ends up over-driving the accessories. Almost all the 03/04 guys still running the stock unported Eaton have found the stock lower pulley coupled with a 2.80 upper is the most economical combo for making power.

U.M.

Do you find you have problems with slippage though with the less surface wrap on the smaller pulley?

peace

Uncle Meat · Jul 21, 2004

Tat98Cobra said:
Do you find you have problems with slippage though with the less surface wrap on the smaller pulley?

peace

Any upper pulley with a diameter of 3.10 or smaller will require a larger idler pulley to prevent belt slip at higher RPM's. You can get away with the stock idler and a shorter belt with pulleys as small as 2.93 if you use one of the non-slip grooved pulleys. Those can eat belts a little faster though.

U.M.

The Factor · Jul 22, 2004

I'm running a Billet-flow 2.76 blower pulley with stock lower and a gatorback belt "smaller size" along with the full set of Idler pulleys and no belt slippage or dust With lots of power and Torque.Billet flow is a little more expensive,but don't try to cut corners when it comes to pulleys because you can end up with alot of slippage and belt dust.U.M is definately correct about non slip pulleys eating belts,i've seen it happen to my friend.He ended up going with a lightning 2.93 pulley I believe,and whats cool about that is it looks stock or closer to stock I should say.Good luck with your choices

Tat98Cobra · Jul 22, 2004

03yellowvenom said:
I'm running a Billet-flow 2.76 blower pulley with stock lower and a gatorback belt "smaller size" along with the full set of Idler pulleys and no belt slippage or dust With lots of power and Torque.Billet flow is a little more expensive,but don't try to cut corners when it comes to pulleys because you can end up with alot of slippage and belt dust.U.M is definately correct about non slip pulleys eating belts,i've seen it happen to my friend.He ended up going with a lightning 2.93 pulley I believe,and whats cool about that is it looks stock or closer to stock I should say.Good luck with your choices

Hey 03yellow - how do you like your Borla stingers? Im thinking about going with them. Did you do them with the x pipe at the same time? Just wondering if they sound good with just the stock h pipe

peace

The Factor · Jul 22, 2004

Tat98Cobra said:
Hey 03yellow - how do you like your Borla stingers? Im thinking about going with them. Did you do them with the x pipe at the same time? Just wondering if they sound good with just the stock h pipe

peace

Yes I did them with the stock h-pipe at first and it sounded great.Alot of compilments from friends to people on the street.Then I did the xpipe and its way loud WOT...but at idle and crusing at parking lot speed it cant be beat..deep throaty and exotic...one of the best choices you can make.Just make sure that if you do a bassani xpipe you get cats...because its nascar loud if you dont.I actulally like the sound better with stock h-pipe ,but I got around 20 more hp by going with bassani x-pipe.If I were to do it again I would get another borla stinger cat back..for sure.

Tat98Cobra · Jul 22, 2004

03yellowvenom said:
Yes I did them with the stock h-pipe at first and it sounded great.Alot of compilments from friends to people on the street.Then I did the xpipe and its way loud WOT...but at idle and crusing at parking lot speed it cant be beat..deep throaty and exotic...one of the best choices you can make.Just make sure that if you do a bassani xpipe you get cats...because its nascar loud if you dont.I actulally like the sound better with stock h-pipe ,but I got around 20 more hp by going with bassani x-pipe.If I were to do it again I would get another borla stinger cat back..for sure.

Hey thx for the info - did you make anymore power with just the catback?

peace

The Factor · Jul 22, 2004

Tat98Cobra said:
Hey thx for the info - did you make anymore power with just the catback?

peace

No problem glad I can help.I didnt dyno it then, but I could feel the difference in the seat of the pants dyno ..I'm not sure but I think there claiming around 20 to 25rwh with just the borla stinger cat back.Make sure you get the stinger cat back I think they have another one were the tip of the pipe has another pipe inside like a baffle.Stick with the one that has a 4" tipe and rolled edge,its less money and sounds way better in my opinion and looks sweet.I f you havnt yet I highly reccomend a cold air intake,so it will let you get more air into the motor and with the less restricting exhaust you'll notice more power increase.

john336 · Jul 24, 2004

I have the 4lb lower crank w/ Steeda idler and I'm installing a 3.10 upper, soon. What's your thoughts on that, U.M.?

Uncle Meat · Jul 25, 2004

john336 said:
I have the 4lb lower crank w/ Steeda idler and I'm installing a 3.10 upper, soon. What's your thoughts on that, U.M.?

Personally I think you spent some money unnecessarily! Them lower pulley rings ain't cheap. You could have achieved the same amount of boost with an upper pulley only (2.80) for a lot less money.

Word of caution for everyone.... Unless you are running a ported Eaton, spinning the stock blower that fast will only cause more parasitic loss and gobs of heat soak. Not to mention the added stress to the alternator because you are over-spinning it with the 4lb lower.

The M112 is rated at a maximum RPM of 14,000 by the manufacturer, although the Lightning guys have been spinning the piss out of them for a couple years now with very few failures. Using the following equation (lower pulley diameter (stock=7.625), divided by upper pulley diameter (stock=3.65), multiplied by max engine RPM (6500) = max blower RPM.
7.625 / 3.65 X 6500 = 13,578RPM's.
Lets take a look at some of the available pulleys and their max RPM's.

Pulley Dia./Blower RPM
3.65 / 13,578
3.40 / 14,577
3.20 / 15,488
3.10 / 15,987
2.93 / 16,915
2.80 / 17,700
2.76 / 17,957

I think a Metco 4lb lower pulley is roughly 8.5 inches in diameter, so using that figure we get the following for your current set up:

8.5 / 3.65 X 6500 = 15,137 Blower RPM's.

Add the 3.10 and you get:

8.5 / 3.10 X 6500 = 17,822 Blower RPM's.

This is roughly the same as a 2.80~2.76 upper.

U.M.

Tat98Cobra · Jul 25, 2004

Uncle Meat said:
Personally I think you spent some money unnecessarily! Them lower pulley rings ain't cheap. You could have achieved the same amount of boost with an upper pulley only (2.80) for a lot less money.

Word of caution for everyone.... Unless you are running a ported Eaton, spinning the stock blower that fast will only cause more parasitic loss and gobs of heat soak. Not to mention the added stress to the alternator because you are over-spinning it with the 4lb lower.

The M112 is rated at a maximum RPM of 14,000 by the manufacturer, although the Lightning guys have been spinning the piss out of them for a couple years now with very few failures. Using the following equation (lower pulley diameter (stock=7.625), divided by upper pulley diameter (stock=3.65), multiplied by max engine RPM (6500) = max blower RPM.
7.625 / 3.65 X 6500 = 13,578RPM's.
Lets take a look at some of the available pulleys and their max RPM's.

Pulley Dia./Blower RPM
3.65 / 13,578
3.40 / 14,577
3.20 / 15,488
3.10 / 15,987
2.93 / 16,915
2.80 / 17,700
2.76 / 17,957

I think a Metco 4lb lower pulley is roughly 8.5 inches in diameter, so using that figure we get the following for your current set up:

8.5 / 3.65 X 6500 = 15,137 Blower RPM's.

Add the 3.10 and you get:

8.5 / 3.10 X 6500 = 17,822 Blower RPM's.

This is roughly the same as a 2.80~2.76 upper.

U.M.

Thats good stuff U.M.
Only thing about your theory of the upper pulley being the way to go though is you're promoting belt slippage. Leaving your upper pulley alone has its benefits imo. True, you will spin your accessories faster with a larger lower, but is that necessarily bad thing? Water pump spinning faster = better cooling. Alternator faster = better charging. Blower faster = more boost. Main reason I started this post is because I know first hand that the oversized crank pulley method works wonderfull on a Centri - however, I am unsure if the Roots/twinscrew style blowers would react negatively (more heat?) from this method.

peace

Uncle Meat · Jul 26, 2004

Tat98Cobra said:
Thats good stuff U.M.
Only thing about your theory of the upper pulley being the way to go though is you're promoting belt slippage.

Yes, with the upper only you will be forced to go with a larger idler to prevent belt slip. My whole point to john336 was that even an upper pulley and new idler combo is cheaper to buy and easier to install than just the lower.

U.M.

john336 · Jul 26, 2004

Uncle Meat said:
Personally I think you spent some money unnecessarily! Them lower pulley rings ain't cheap. You could have achieved the same amount of boost with an upper pulley only (2.80) for a lot less money.

Word of caution for everyone.... Unless you are running a ported Eaton, spinning the stock blower that fast will only cause more parasitic loss and gobs of heat soak. Not to mention the added stress to the alternator because you are over-spinning it with the 4lb lower.

The M112 is rated at a maximum RPM of 14,000 by the manufacturer, although the Lightning guys have been spinning the piss out of them for a couple years now with very few failures. Using the following equation (lower pulley diameter (stock=7.625), divided by upper pulley diameter (stock=3.65), multiplied by max engine RPM (6500) = max blower RPM.
7.625 / 3.65 X 6500 = 13,578RPM's.
Lets take a look at some of the available pulleys and their max RPM's.

Pulley Dia./Blower RPM
3.65 / 13,578
3.40 / 14,577
3.20 / 15,488
3.10 / 15,987
2.93 / 16,915
2.80 / 17,700
2.76 / 17,957

I think a Metco 4lb lower pulley is roughly 8.5 inches in diameter, so using that figure we get the following for your current set up:

8.5 / 3.65 X 6500 = 15,137 Blower RPM's.

Add the 3.10 and you get:

8.5 / 3.10 X 6500 = 17,822 Blower RPM's.

This is roughly the same as a 2.80~2.76 upper.

U.M.

Thanks for your reply.

The lower 4lbs Metco came with car (bought it used @4100 miles) so no $ lost there. I only found out it had the lower because the 2.8 belt wouldn't fit when I tried to install a Steeda 2.8 pulley.

My SCT 9100 is tuned for a 2.8 so I'm still going ahead with the 3.10 upper in addition to the lower.

BTW, I talked to Metco and they said I won't have any alternator problems running a 2 or 4lb lower.

Thanks again!

03/04 Overdriving Crank Pulley Information needed

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