Question about calculating Boost Ratios MATH EXPERTS NEEDED

[90lxcoupe]

i have a paxton novi 2000 on my car and i am looking into buying a larger pulley to bring the boost down cause i am making way too much power (480RWHP) i have the stock pulleys from paxton on there plus a power pipe from AFM. i think the impellar pulley is either 3.50 or 3.75 and i can get a pully all the way up to 4.25 inches what would the ideal size pulley be to get me running 6 to 8 lbs of boost??

also i am asking because i dont want to buy a pully and have the blower only make like 4lbs

if anyone knows a formula that will help me out i would greatly appreciate it


thanks

 

[Scorcher2005]

you are complaining that you are making too much power? Why would you want to de-tune the car? i think the best advice would be to call paxton on monday and ask.

 

[90lxcoupe]

i want to de tune the car because i am now at the power level that i will crack a block, i am blowing lots of head gaskets and i will be happy with around 400 hp for a street car.

 

[88stangmangt]

i want to de tune the car because i am now at the power level that i will crack a block, i am blowing lots of head gaskets and i will be happy with around 400 hp for a street car.

cracking the block is a joke.....get better head gaskets.....look at my combo i have a girdle for more insurance.....i plan to make mid 5's to the ground.

motor is being sent to a motor dyno to be tuned and obviously dynoed.

 

[FullAuto]

If you break the block at only 480 it's your fault for the poor tune. Don't blame it on the block. If you change pulleys, you void the warranty. There is obviously something already wrong with your tune or some poor machine work if you're blowing head gaskets. Fix your current problems and you'll be fine.

 

[90lxcoupe]

i am fixing the gasket problem, i dont have a warranty on the blower and i am not using the smaller pulley as a solution to the head gaskets i dont really see a need for 480 hp on a street car. and there is a good possibility of cracking a block once over 450 rwhp is made. a girdle is only gonna keep the pieces together for so long until the block lets go

 

[Scorcher2005]

ehhh, if it were me, i would just keep 480 hp. When the block breaks, its just more of a reason to get a stronger block ;-)

 

[88stangmangt]

i am fixing the gasket problem, i dont have a warranty on the blower and i am not using the smaller pulley as a solution to the head gaskets i dont really see a need for 480 hp on a street car. and there is a good possibility of cracking a block once over 450 rwhp is made. a girdle is only gonna keep the pieces together for so long until the block lets go

if u dont shift every gear at 6600 rpms then you shouldnt have a problem....your not making 480 at 3-4k. which is with the type of motor we both have you still have plunty of power down there.

 

[90lxcoupe]

ehhh, if it were me, i would just keep 480 hp. When the block breaks, its just more of a reason to get a stronger block ;-)

im all about getting a stronger block but my wallet dosent really agree with that since the bare block is at least $2,000

 

[88stangmangt]

im all about getting a stronger block but my wallet dosent really agree with that since the bare block is at least $2,000

i'll tell you what....i have a stock pulley for my s-trim and you have the 10lb pulley right??? well lets trade.......then neither of us have to spend extra money and i think vortech makes paxton so blower wheels should match up.

 

[90Notch]

There is no formula to calc boost, you calc what rpm it spins at then go to boost curve to find boost.

 

[vikingpower]

also the volumetric efficiency of the engine will change observed boost with the same blower impeller speed: higher VE, less observed boost. Therefore you would have to experiment with different pulley sizes to find the desired (guage) boost specific to your engine.

 

[The Fox]

Somethings just dont make sense to me. We all save every dime dor more horse and this guys just blows past what he wants. Like, whoops, too much. Let's back 'er down 80hp real quick...If u want less horse let's trade cars. I don't have my heads yet so with luck I'm between 240 and 270. Depending on which/how many stickers I put on

 

[The Fox]

There's also a good chance of cracking a stock block, with 200hp revving to 5500, holding it there and having someone spray your block with a hose Make sure the engine is nice and hot, even overheating works well in this process.

 

[jrichker]

Rule of thumb: every 14.7 psi of boost doubles the power observed without boost. This does not take into consideration power required to drive the supercharger, or pumping losses from heating the intake charge.