sutyak
07-09-2010, 01:40 PM
I need some turbo theory clarification, because I've apparently missed something.
First, the max flow potential of a turbo is defined by the cross-section at the compressor inlet. Yes/no?
Looking at a compressor map, this max flow is the "choke line" on the right side, sweeping upward.
In comparing my dyno chart to the compressor map it appears the max HP is seen when the max turbo flow is met.
HP will drastically drop after this flow is met, as does torque.
It also appears the max torque is met within the map's "island" and will gradually drop off outside that island.
(If you see this like I do, your turbo is either too small or best-case this happens right at redline)
These things being noted, I've read where people get more HP from the same turbo by increasing the psi, even though the turbo's flow potential was already met at a lower psi.
My question is: doesn't this seem to violate the first rule that the max flow potential is defined by the compressor inlet?
So if a compressor wheel is rated to flow 400CFM, how does someone get 450CFM worth of power out of it? Internet BS? (I'm serious)
Aside from that, if the max flow is met at a lower psi, then increasing the psi would only result in the max flow being met at a lower RPM and dropping off sooner, correct?
I started with a 350CFM (max) IHI RHB52 turbo, which saw it's max flow at just 5,300 RPM.
Recently I sent the turbo off to upgrade the compressor wheel to a TD0H 16T wheel, which flows 440 CFM.
The turbine side has not been opened up yet.
With that upgrade and a better tune it gained 5mph in the 1/4, and moved the max flow to appx 6,000 RPM.
There is still room though as it's clear I didn't get all of that 440CFM. More like 390-400CFM.
I'll definitely open up that turbine outlet some to help out, but until then I had ideas floating around.
One idea was to increase the boost a bit. (already at 10psi)
Well if it already sees max flow then there's no point right?
That would really just move my powerband down, which I don't want to do.
This thought took me back to some reading where I came across a Volvo owner making a supposed 282whp with that 16T, whereas average numbers were 240whp, which is what 440CFM should result to.
So this is why I actually posted. How can one get that much more power from a turbo supposedly restricted to 240whp?
I'm not wanting to, I just want some clarification.
First, the max flow potential of a turbo is defined by the cross-section at the compressor inlet. Yes/no?
Looking at a compressor map, this max flow is the "choke line" on the right side, sweeping upward.
In comparing my dyno chart to the compressor map it appears the max HP is seen when the max turbo flow is met.
HP will drastically drop after this flow is met, as does torque.
It also appears the max torque is met within the map's "island" and will gradually drop off outside that island.
(If you see this like I do, your turbo is either too small or best-case this happens right at redline)
These things being noted, I've read where people get more HP from the same turbo by increasing the psi, even though the turbo's flow potential was already met at a lower psi.
My question is: doesn't this seem to violate the first rule that the max flow potential is defined by the compressor inlet?
So if a compressor wheel is rated to flow 400CFM, how does someone get 450CFM worth of power out of it? Internet BS? (I'm serious)
Aside from that, if the max flow is met at a lower psi, then increasing the psi would only result in the max flow being met at a lower RPM and dropping off sooner, correct?
I started with a 350CFM (max) IHI RHB52 turbo, which saw it's max flow at just 5,300 RPM.
Recently I sent the turbo off to upgrade the compressor wheel to a TD0H 16T wheel, which flows 440 CFM.
The turbine side has not been opened up yet.
With that upgrade and a better tune it gained 5mph in the 1/4, and moved the max flow to appx 6,000 RPM.
There is still room though as it's clear I didn't get all of that 440CFM. More like 390-400CFM.
I'll definitely open up that turbine outlet some to help out, but until then I had ideas floating around.
One idea was to increase the boost a bit. (already at 10psi)
Well if it already sees max flow then there's no point right?
That would really just move my powerband down, which I don't want to do.
This thought took me back to some reading where I came across a Volvo owner making a supposed 282whp with that 16T, whereas average numbers were 240whp, which is what 440CFM should result to.
So this is why I actually posted. How can one get that much more power from a turbo supposedly restricted to 240whp?
I'm not wanting to, I just want some clarification.