s1ngle

Alright, Ive been searching and searching forever, found some info, but want to come to a conclusion on this.

Ive had people tell me, that a small turbo at 5 psi will create less power than a larger turbo at less boost. Is this true? I dont think so.

Wouldnt boost be boost? no matter how small or big the turbo is? Granted, a smaller turbo will have to spin faster, and might not be able to hold boost at high RPM, but it still will make the same power, given its actually creating the desired boost. Boost is just the pressure created by the turbo. heck, it could be created by me blowing into the charge pipe, and if i can create 5 psi i will still get the same result.

However, there is one issue to consider. Your car will make less power with a smaller turbo, if it loses efficiency before your engine's peak power range. Thats obvious.

My conclusion: 5 psi on a T4 will give you the same power as 5 psi on an RHB5.

How does everyone else feel about this? Agree, disagree?

s1ngle

Please give me substantial arguments if you disagree, not just no youre wrong.

Spenser

A smaller turbo will give you more restriction in the ehxaust, so thats one reason why A larger turbo will give you more powa! But the main reason why a larger turbo gives out more powa! is the CFM, 5 Psi on a little IHI is not the same as 5 psi on a T4

turboguy84

a bigger turbo conatins more Oxygen per lb of boost

turbohf

its all about CFM...the T4 will be able to push more air into the engine AT 5psi than a IHI......---- this is hard to explain...how about this: a sqirt gun sprays out a stream of water = 5psi (for example) not much water is it even at 5psi? now try a garden hose at 5psi....you understand now?

baldur

No, CFM is completely irrelevant here. It's all about lbs/min of air! Hot air at the same CFM means less lbs/min airflow, hence less power!

SpeedyJAY

Sounds like someone needs to take a mechanical systems design course, or consult the MEEB (thats Mechanical+ Electrical Engineering for Buildings)

It IS about moving Cubic feet per minute.

Picture this you place a little fan (18" in Dia.) turning at about 500 rpms. Preasure behind the fan will be @ XX atmospheres This would generate an ACH (air change per hour) of ohhh say .25

Now lets say you put a fan that is 8' in Diameter in the window and it turns @ 100 rpms. The Air speed would be 5x less giving it about 5x less preasure behind the fan.

However the big fan would generate an ACH of say 1.75

Got it ?

s1ngle

Well, I seem to be getting the same arguments I have always heard, with very little to back it up.

The exhaust restriction argument seems to be the most relevant. I didn't think about that before.

What some people dont understand is, yes a larger can flow more CFMs, but if you have a big turbo at 5 psi, it can only flow enough cfms to create 5 psi. The smaller turbo creates the exact same number, but it just has to spin faster.

Doesnt that make any sense to anyone?

s1ngle

Someone give me a trustworthy source for your argument!

Don't just tell me its all about the cfm's!

s1ngle

What seems a little wrong about this, is that you dont consider the fact that the air from both fans, to be comparable to a turbo, would have to be channeled into a pipe of the same diameter for both fans. Thus, from the big fan, youre gonna get more air speed, and either as much or more boost as the small fan.