hey guys i was wonderong how many pounds of boost i can run a p up to if i build a blower motor?
Thanks Matt

 

Boost is all relative to engine size & flow capability.

about 15# on a stock LT1 350
about 10# on a good flowing 383

This can easily vary by 3# in either direction depending on specific cam, head & exhaust choices.

 

I thought it was rated to 28 psi? I am planning to run mine at 18 psi- what perimeters does ATI use to determine that the P1 can run up to 28psi of output?

 

http://www.procharger.com/models.shtml

Procharger rates it for 30 #... I'm just guessing here, but I figure the rating has to do with being too much load on the bearings if it has much more load on it.

Yeah, sure you could get 28 PSI with a P1 on a Honda Civic, but it just isn't capable of flowing enough air to make that much boost on a good flowing 383.

 

I am sure it wouldn't be the best blower at 30psi, but there's got to be some sort of specs on how they grade them. I wouldn't think there'd be THAT much of a CFM difference between a Honda and stock LT1 that 28psi on a Honda is better than it would be on an LT1. I also have a hard time believing the P1 is only good to 15psi.

 

No, I don't think you're getting it... The supercharger can only put out a certain amount of air at max RPM. So if you are spinning a P1 at it's max 62k RPM it's going to be flowing 1200 CFM. No matter what motor it's attatched to, thats all you will get out of it.

Boost is a measurement of restriction.

for example, Say a NA 1.6l honda flows 200cfm WOT... force 1200 CFM into it... that's 1000 extra cfm trying to fit into 1.6L, you may see 30 psi

where as a 383 NA LT1 flowing 600cfm, well if the same blower is flowing 1200 CFM, that's an extra 600cfm, going into 6 liters, you can see how it will definetly be lower PSI, as there is less restricion... 10-15# or so.

So when it's rated for 30 psi, that doesn't mean you'll be able to see that much on any motor you put it on. I made up the numbers in the example, but you get my point?

I'm assuming when they rate it for 30psi, that's how much pressure the impeller/bearings can withstand for an extended amount of time.

To actually see 30PSI on the 383 you'd need something like an F-1R at 2000 CFM.

 

Agreed. Lonnie is one of the most knowledgeable people on this board when it comes to ATI blowers so I would listen to him. I had a P600b with a built 383 motor and only made 10lbs of boost with a 15lb pulley. I would think that the P1SC could probably have made another 1lb of boost. Yeah ATI claims that a P1SC is good for 30lbs of boost. All I have to say to that is yeah right.

 

Then prove us all wrong and make 18lbs of boost. Good luck on those blower seals.

 

Here is a ballpark approach to airflow.......

Note it does not take into account: induction flow capabilities or volume changes due to charge heating (air expansion).

Take a P-1SC at 1200cfm.

A 100% efficient 350ci motor flows 607cfm at 6000rpm.
14.7psi is roughly 1 atmosphere of pressure.

((1200cfm/607cfm)*14.7)- 14.7 equals 14.36# boost.

This is based on max charger output at 6000 engine rpm & 100% efficiency (intercooler/aftercooler) temp.

Once you heat the air, boost also goes up.... the less that the intercooler cools the mixture the more boost you will see.

Do the same with a 350 running at 3000rpm & the supercharger maxed out & boost will double. The same with an engine 1/2 the size at the same rpm.

This is a crude approximation at best, but gives you some idea of the pressure relationship.

The boost capability of a charger is related to the compressor pressure rating. For example a rating of 2 (which is in atmospheres) 2 X 14.7 = 29.4# boost.

Hope this helps.

 

I knew my numbers werent too far off, but didn't feel like figuring out the actual formulas to come up with real numbers.

Thanks!

 

So what's better- to have a blower motor combo that makes 0psi without going into vacuum, or one that makes 10psi of boost?