Compound Procharging!

[T/Aaron]

Wouldn't you need 2 compressors to feed into 1 compressor to make this idea viable? If you have 2 compressors, you're airflow is limited by how much air flows through the first compressor. Pressure should not matter if the volume of flow is not increased. P1V1=P2V2. Not sure how compounding is going to change this fundamental equation.

[Procharmo]

Wouldn't you need 2 compressors to feed into 1 compressor to make this idea viable? If you have 2 compressors, you're airflow is limited by how much air flows through the first compressor. Pressure should not matter if the volume of flow is not increased. P1V1=P2V2. Not sure how compounding is going to change this fundamental equation.

Well it depends on how, much pressure and volume you can use. What Flex has done is to take a pair of off the shelf F2 Prochargers and have performance equal to the much more expensive Pro Mod PSI twin screw blower. If he were to do as you suggest and run an larger F3 into and F2 or two F2's into one F2 then the resulting pressure and heat would be much more than his engine could utilise.

If we look at the inner workings of jet engines the multi-stage compression can be achieved with either a larger slower spinning impeller or faster smaller impeller.
I think due to packaging and compressor efficiency reasons the twin same size blowers at different speeds worked out to be adequate...

The idea has been proved viable due to his record breaking run. It just hadn't been done when I first had the idea... I'm now just looking to see if it can be used out of the 3500hp arena and in our lowly 1000hp and below arena............

[Wicked]

For supercharging, you are limited by how fast you can turn the impeller...i.e. You can only fit so many gears in a given package and it still fit in the car.

Think about a turbo, it may spin up to 120,000 rpm depending on the size. Smaller one's approach 200,000 rpm I believe. So a much smaller compressor can be used to make big power.

Its much harder to make a blower spin that fast, i.e. a 6000rpm engine would require a 20:1 step up(including pulley ratio) ratio to get the same rpm as the turbo. If you could achieve the 20:1 you could use a smaller impeller. However, its then much less efficient due to all the gear losses and the fact that its always spinning 20 times faster than the engine.
To put it in perspective. My Procharger P1SC has an internal ratio of 4.1:1 and with my belt ratio was turning about at the limit 62000rpm.

The compound supercharging allows you to run two compressors in series. Here's an example of two identical centrifugal superchargers in series. These are vortech since that's the first compressor map i came to. One blower, for example, spins at 40000rpm, pumps 30lbs/min of air at a pressure ratio of 1.8:1. So the first blower would create 1.8*14.7psi-14.7=11.76 psi gage.
No the air coming into the second blower is higher. But the second blower is still pumping at the same rpm, will yield 60lb/min and 1.8:1 pressure ratio. So the final boost should be about 33psi at 60lb/min.

The good thing about this is the blower doesn't have to spin right at its limit to make a lot of boost. Because its two larger compressor(as opposed to a turbo), less heat is being added to the air. However, this should be quite inefficient compared to a turbo setup and possibly just as heavy.

This is the first time I've ever done the compound supercharging calculations, so I may have made an error.

In my opinion, twin turbos are better and definitely my qeapon of choice. And I have owned both. You can have the car setup for 500hp one day, and 800ho the next with the same turbos. No belts to change. Better efficiency. Etc.

[Procharmo]

For supercharging, you are limited by how fast you can turn the impeller...i.e. You can only fit so many gears in a given package and it still fit in the car.

Think about a turbo, it may spin up to 120,000 rpm depending on the size. Smaller one's approach 200,000 rpm I believe. So a much smaller compressor can be used to make big power.

Its much harder to make a blower spin that fast, i.e. a 6000rpm engine would require a 20:1 step up(including pulley ratio) ratio to get the same rpm as the turbo. If you could achieve the 20:1 you could use a smaller impeller. However, its then much less efficient due to all the gear losses and the fact that its always spinning 20 times faster than the engine.
To put it in perspective. My Procharger P1SC has an internal ratio of 4.1:1 and with my belt ratio was turning about at the limit 62000rpm.

The compound supercharging allows you to run two compressors in series. Here's an example of two identical centrifugal superchargers in series. These are vortech since that's the first compressor map i came to. One blower, for example, spins at 40000rpm, pumps 30lbs/min of air at a pressure ratio of 1.8:1. So the first blower would create 1.8*14.7psi-14.7=11.76 psi gage.
No the air coming into the second blower is higher. But the second blower is still pumping at the same rpm, will yield 60lb/min and 1.8:1 pressure ratio. So the final boost should be about 33psi at 60lb/min.

The good thing about this is the blower doesn't have to spin right at its limit to make a lot of boost. Because its two larger compressor(as opposed to a turbo), less heat is being added to the air. However, this should be quite inefficient compared to a turbo setup and possibly just as heavy.

This is the first time I've ever done the compound supercharging calculations, so I may have made an error.

In my opinion, twin turbos are better and definitely my qeapon of choice. And I have owned both. You can have the car setup for 500hp one day, and 800ho the next with the same turbos. No belts to change. Better efficiency. Etc.

Thanks, great breakdown. I'm not saying Centris are better than Turbos. Just saying that compound Centris can equal PSI twin screws or get close. Then again there are twin turbo Pro mod's as well as nitrous ones. At that power level I believe the engines are somewhat similar but the cost of a pair of F2's is less than the the other power adders when above 3000hp.....

Here's a test video of a twin compound F2 set up.....

[Wicked]

Notice how the bypass and reversion blows the air filter off.

[Procharmo]

That's not the air filter. This is a compound pair of Twin F2's that later went on to be the current fastest Procharged Vehicle......It's the Flex Racing Pro Mod mentioned earlier on a conventional BBC as opposed to the BAE Hemi.



What you saw blow out was the bung they had in the discharge tube whilst testing pressure....The output of the second blower was connected to that bung.

There was no air filter on the primary blowers intake.