Underdrive Pulleys for Supercharged Cars?

[FordNut]

When you supercharge, the original size crank pulley is used (doesn't make sense to underdrive a blower) but couldn't the same effect as a smaller crank pulley be achieved with larger pulleys on the PS pump and air pump (and water pump unless an electric one is used)? Alternator shouldn't matter since it can be shut off at WOT. Sure, it's only worth about 10 hp which is not that significant to a blown car, but why not? And while you're at it why not go with 8 ribs instead of 6 ribs.

Just wondering.

[TAF]

Or...you could go with an Overdrive pulley on the crank/dampner...as much as 10% over. Which will spin the SC pulley faster without downsizing the pulley.

One of the BEST made is from a small company called Innovators West http://www.innovatorswest.com/ all 8-rib and made by true craftsmen.

[martyo]

Or...you could go with an Overdrive pulley on the crank/dampner...as much as 10% over. Which will spin the SC pulley faster without downsizing the pulley.

One of the BEST made is from a small company called Innovators West http://www.innovatorswest.com/ all 8-rib and made by true craftsmen.

Yep, they make nice stuff all right. Their web site doesn't do their products justice.

[BillyGman]

Just a side note here:

The blower pulley and crank pulley in the Trilogy blower kit's are 8 rib already.;)

[MikesMerc]

Just a side note here:

The blower pulley and crank pulley in the Trilogy blower kit's are 8 rib already.;)

Yep. Therefore, it's not worth the gain to change everything. Without the benefits of needing to go to 8 rib, there 10hp is of little value for the $$$ involved.

A much better mod with the blower install would be the electric water pump. The water pump is where you get most of your parasitic drag (aside from the blower of course).

[FordNut]

Yep. Therefore, it's not worth the gain to change everything. Without the benefits of needing to go to 8 rib, there 10hp is of little value for the $$$ involved.

A much better mod with the blower install would be the electric water pump. The water pump is where you get most of your parasitic drag (aside from the blower of course).
Well, I guess that's a matter of opinion. IF you had 492 RWHP and your goal was 500, and every other power adder had been added (including the water pump), then why not? And if somebody has already sunk well over $8000 into hopping up a car, what's a few hundred more?

I agree the electric water pump is probably a better route to go for the 12 hp gain (at least that's what I picked up) but as far as I know the 10 hp I gained from adding the underdrive crank pulley didn't go away when I took off the water pump and pulley to install the electric pump with idler.

[Dennis Reinhart]

When you supercharge, the original size crank pulley is used (doesn't make sense to underdrive a blower) but couldn't the same effect as a smaller crank pulley be achieved with larger pulleys on the PS pump and air pump (and water pump unless an electric one is used)? Alternator shouldn't matter since it can be shut off at WOT. Sure, it's only worth about 10 hp which is not that significant to a blown car, but why not? And while you're at it why not go with 8 ribs instead of 6 ribs.

Just wondering.

Its not a good Idea unless the blower is rated for the increase in RPM. you can burn the blower up and the motor, with contaminated oil.

[BillyGman]

"Contaminated oil"??? My guess is that this would NOT apply to the Trilogy/Eaton blowers, since they're self contained and use their own oil reserve rather than the engine oil. Right? I'm not neccessarily saying one design is better than the other simply because of that. I'm just thinking that your statement must only apply to certain types of blowers.

[Dennis Reinhart]

Yes Billy I am talking about a Vortech blower but even though the Eaton has a self contained oill system, if the blower lets go it could damage the engine.


http://www.marauder57.com/images/Reinhart%20Moving%20MM.gif

[BillyGman]

Okay Dennis. Thanks. :)

[FordNut]

Its not a good Idea unless the blower is rated for the increase in RPM. you can burn the blower up and the motor, with contaminated oil.
I do not see how changing the driven pulleys for accessories would have any effect whatsoever on the blower. Do you not have to remove the underdrive pulleys and reinstall a different crank pulley (original size) for your blower system? I understand that the oversize crank pulley mentioned in one of the replies in this thread would indeed overdrive the blower but I don't understand how changing to a larger size PS and air pump pulley would do anything to the blower or oil. It should only reduce parasitic losses.

[martyo]

I understand that the oversize crank pulley mentioned in one of the replies in this thread would indeed overdrive the blower.

The idea here Brian is to spin the blower faster and increase the boost.

[FordNut]

The idea here Brian is to spin the blower faster and increase the boost.
Yes, I realize that either increasing the crank pulley size or reducing the blower pulley size will spin the blower faster and increase boost. This increases power production of the engine. That was not what I was talking about when I started the thread. I am thinking about reducing power loss to drive accessories, as we have done with the NA cars.

The underdrive pulleys we put on the NA cars use a smaller crank pulley which spins the ps pump, air pump, alternator, and water pump slower and reduces power loss to these devices. A larger water pump pulley is also used which further reduces the water pump speed and frees up even more power for application to the rear wheels.

So why would the same effect not be observed by using larger pulleys on all the driven devices with the crank pulley being left at the OEM size (or whatever size is specified for the blower).

[Dennis Reinhart]

I must have misunderstood, I thought you were talking about leaving the Underdrive pulley on an SC car this will Raise the boost level as well as the speed of the blower, each blower is rated for a specific RPM if you exceed this, it can damage the blower, for example of the S Trim I use as well as KB you can only go so small on the blower pulley with out risking the chance of the blower coming apart, if you have an engine that will take more boost then at some point you need to upgrade the blower, for example going from a S. Trim to a T. Trim or a JT trim, each of these blowers throw more boost as well as volume,

The Eaton is the same way you can only go so far with a smaller pulley. Brian at Apten was honing out the Eaton case and making more power that way, so again there are limits to different setups, changing the PS pulley will effect only that, since it is run off the OEM crank pulley, so you will either lower or raise the PS pump speed by changing the pulley, now if you can change power steering pressure by demand by changing the pump pressure this can be a RWHP since reduced pressure would be less drag on the motor just like the belt drive water pump.

There would be a gain if you can reduce pump pressure. The draw back is less power steering assist but at higher MPH that would not be noticed as much. One way of doing this is to change the spring in the PS pump housing I may try this at some point:beer: