Map Width Groove HP charger

dvst8r

dvst8r

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Has anyone out there, that is willing to share there information, done any back to back tests to see if there is an advantage to running grooves on the HP charger?

I can see the obvious benefit in an atmospheric charger, but in an HP one not as much, but maybe I am not looking at it right?
 
Sad, but not surprised, typically if you have this kind of information, it cost you some $$$.
 
On a high pressure app i dont think it would matter. intresting to se if anybody has run tests?
 
It definitely matters. The HP turbo still functions as a single until the LP turbo builds pressure. That means it can still surge if you're trying to push a high pressure ratio out of it.
 
but when you're having to pull air through another turbo and expel exhaust through another turbo, the propensity to surge is lessened
 
Forrest Nearing said:
but when you're having to pull air through another turbo and expel exhaust through another turbo, the propensity to surge is lessened
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As well as the fact that by the time you get into the surge range on the HP charger, the LP charger should be well on its way. My manifold pressure is typically 2:1 of my interstage pressure.
 
it still matters. The MWE is there to decrease the Vena Contracta formed as the air flows into the compressor
 
Forrest Nearing said:
but when you're having to pull air through another turbo and expel exhaust through another turbo, the propensity to surge is lessened
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Actually it increases the likeliness of it!
Instead of pulling air through a nice straight nonrestrictive air filter assembly its having to pull air through the slot, blades and angles of another turbo. That means a higher vacuum on the inlet which means a higher pressure ratio.
 
300D said:
Actually it increases the likeliness of it!
Instead of pulling air through a nice straight nonrestrictive air filter assembly its having to pull air through the slot, blades and angles of another turbo. That means a higher vacuum on the inlet which means a higher pressure ratio.
Click to expand...

it causes the turbo to spool up slower... which decreases the likeliness to surge
 
Um, no. Thats not how turbos work.

The slower spool is due to the restriction. Restriction is vacuum. Vacuum increases the pressure ratio. A higher pressure ratio with less flow = easier to surge.

Turbos 102, I suggest you read up.
 
I suggest you try something real-world... how does the exhaust restriction effect spool-up? it slows it...

by the time you get well to the right of the surge line, the primary compressor is feeding the secondary and there's no vacuum

also... a more restrictive air filter will lessen compressor bark! :D
 
Last edited:
If no MWE groove is used shouldn't the interstage air plumbing be kept close to the same as the HP chargers inducer size?
 
300D said:
Um, no. Thats not how turbos work.

The slower spool is due to the restriction. Restriction is vacuum. Vacuum increases the pressure ratio. A higher pressure ratio with less flow = easier to surge.

Turbos 102, I suggest you read up.
Click to expand...


This seems to be more relative to the compressor sizing of each turbo as well, no?
 
In the little experience I have, it seems that the HP compressor becomes a restriction to the LP compressor on the pressure side of things, long before you ever come close to the HP charger surging. The size differential between the two compressors before the HP becomes that restriction, also seems to be much greater then what is commonly thought and advised.

This is one of the reasons I initially posted this question, as I experiment with spreading the chargers further and further apart in relative size the HP does eventually become a restriction, and in theory the same charger with the map width grooves should flow a little bit more, but this may not be the case at all when it is in a pressurized system. Hence I was hoping to find someone that has done the back to back testing. Someday I will test this, just need to acquire the resources.

With all of that being said, I am enjoying the discussion that has resulted.
 
LReiff said:
If no MWE groove is used shouldn't the interstage air plumbing be kept close to the same as the HP chargers inducer size?
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Tough to do on a turbo that is a 62mm inducer but has a 4" inlet size. Even if you kept the piping at 2.75", you'd still need a transition hose to adapt it. Would it really benefit to have two transitions right before the inducer?
 
Tate said:
Tough to do on a turbo that is a 62mm inducer but has a 4" inlet size. Even if you kept the piping at 2.75", you'd still need a transition hose to adapt it. Would it really benefit to have two transitions right before the inducer?
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there wouldn't be a transition if you ran the 2.75 pipe right up to the inducer bore. Leave a small gap so the mw groove is still functional. I don't know if it would work better like that its just the way I have done it in the past
 
DieselheaD said:
wouldnt it make interstage temps hotter? or you trying to create the same air velocity before and after HP turbo?
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No, interstage temps would not be affected.

Air velocity at the inlet of a turbo is always faster then at the outlet since the air comming out of the turbo is compressed!!!
 
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