Supercharged/Turbocharged The increase in air/fuel pressure above atmospheric pressure in the intake system caused by the action of a supercharger or turbocharger attached to an engine.

Superchargers with restrictive air flow with higher PSI pullies

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Old Oct 3, 2003 | 11:56 AM
  #1  
Prodeje79's Avatar
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Superchargers with restrictive air flow with higher PSI pullies

I have read some threads reguarding use higher PSI pullies and using BOVs/etc to save from hitting as high a boost in the end.
I have also read threads discussing a possble variable pully to have higher boost low end and then switchching to lower boost at high end.

Is anyone familiar with the Ford SHO supercharger options?
One of the options uses higher boost pullies, but then use air restrictions via piping or air filters. Here is an excerpt from the SHO mailing list:
***
Vadim / SHO Shop use the Vortech 15psi pulley for their 9-12psi kits as
well. The tiny personal-birthday-cake K&N filter restricts air to 9psi;
for the 12psi kit, there is a "reducer" that's in the snorkel side to
restrict flow. Remove the birthday cake, and you'll hit 14-15psi like I
did on the dyno (or the street, wherever).

I contacted K&N & got some basic flow info on the engine and on the
filter SHO Shop provides - 880cfm is K&N's estimate of the engine's
breathing requirements at 14psi, 7200 redline, 3.2L; the birthday cake
flows 262cfm, IIRC. I have a large cylindrical K&N now that flows
801cfm
(IIRC).

If you removed the provided filter & replaced it with something else,
or
if you removed the neck-down restiction, you're hitting more actual
boost. The logic was, 15psi pulley helps max boost hit earlier, then
gets choked off to the desired max limit.

Hope this helps the confusion.

EDIT: the peak hp with the smaller
pulley
/ more restrictive setup at 9 psi will be lower than a larger pulley /
less
restrictive filter that also makes 9 psi...but the opposite will be
true of
low end torque.

***

Any thoughts or ideas about this?
Old Oct 3, 2003 | 12:08 PM
  #2  
ejj's Avatar
ejj
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Originally Posted by Prodeje79
Any thoughts or ideas about this?
Sounds right. I gained over 1psi on the stock pully in going from the stock filter to a SCCAI (http://www.ericj.org/maxima/img/sccai/filters.jpg). I have to think that gain would be larger with smaller pullies.
Old Oct 4, 2003 | 07:53 PM
  #3  
Craig Mack's Avatar
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Maxi-Overdose is doing something similer to this. He is using a 2.6" pulley, and leaking boost via his adjustable BOV so he only hits like 10psi. The pulley he is using is made to produce 14psi, however. So he probubly see's boost a lot sooner then someone like me who see's about 10psi via a 3.125" pulley without bleeding boost.

The only problem with this is that he is wearing down his blower a lot faster. The 2.6" pulley overspins the blower slightly near redline, and probably creates tons of heat.

Another idea is a CVT pulley, that spools up full boost before redline, similer to a roots type blower. Only problem is that this option isnt available to us and would take a lot of money/hours to manufactor, and no one knows if it would even fit.
Old Oct 6, 2003 | 02:21 PM
  #4  
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I'd be interested to see how much restriction the pan-cake filter or even CAI makes on a dyno.

Someone should try removing the filter and see if there are gains to be made. Choking the inlet side of the blower to limit boost will work, but you're losing power as the choking point is reached and overheating the air as the blower is inefficiently spinning too fast.
Old Oct 6, 2003 | 03:11 PM
  #5  
[maxi-overdose]'s Avatar
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Originally Posted by Craig Mack
Maxi-Overdose is doing something similer to this. He is using a 2.6" pulley, and leaking boost via his adjustable BOV so he only hits like 10psi. The pulley he is using is made to produce 14psi, however. So he probubly see's boost a lot sooner then someone like me who see's about 10psi via a 3.125" pulley without bleeding boost.

The only problem with this is that he is wearing down his blower a lot faster. The 2.6" pulley overspins the blower slightly near redline, and probably creates tons of heat.

Another idea is a CVT pulley, that spools up full boost before redline, similer to a roots type blower. Only problem is that this option isnt available to us and would take a lot of money/hours to manufactor, and no one knows if it would even fit.

I am using 2.87.....

2.62 is for Mardigrasmax only....

update : I tighten the BOV once and I only see 11psi max on my boost gauge. I am thinking either the greddy S BOV is not capable of holding more than 10psi boost pressure or some other mechanical issues. (Greddy does recommend to use the Type R BOV for higher boost pressure).

anyways, I am happy with 10psi.....but my injectors are not.
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