Maximum boost with ceramics vs exhaust being used - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

R33_GTS-t · 17th August 2006, 09:54 AM

I got to thinking about the 1 bar limit for R32/R33 ceramic (turbine) turbos. Surely the maximum safe boost depends on the exhaust being used. To attain a certain level of boost, you need a certain flow and pressure gradient across the turbines. Hence, if you have higher back-pressure (e.g. using stock exhaust, downpipes and cat) you need higher pressure on the inlet to attain 1 bar and the blades are more at risk of shearing off. Using a 90-100mm decat turbo-back system, there is next to no back-pressure and hence the pressure on the inlet is less, meaning less risk to blades.

Is this reasoning sound?

R34Nismo · 17th August 2006, 09:56 AM

HEAT.

ExScoobyT · 17th August 2006, 10:32 AM

Its shaft torque that breaks ceramic wheels-off (assuming a good map with no det). As temp increases the torque limit does come down as well.

More inlet boost = higher compressor tip-speed. Higher compressor tip-speed = more torque from the turbine and = higher shaft torque.

R33_GTS-t · 17th August 2006, 02:30 PM

Cheers.

danok · 17th August 2006, 03:08 PM

No more than 1 bar on ceramics

SIHethers · 18th August 2006, 09:32 AM

If it's shaft speed/torque that breaks them, then low exhaust back pressure will exacerbate this by increasing airflow, and hence compressor speed required to develop any given boost pressure, particularly as compressor efficiency drops at higher flow rates.

17th August 2006, 09:54 AM	#1 (permalink)
R33_GTS-t GTR Register Member Join Date: Apr 2005 Location: [510] days from disposing of Labour. BNFL are shit. One repossession, one (bank) window. Posts: 8,241	Maximum boost with ceramics vs exhaust being used I got to thinking about the 1 bar limit for R32/R33 ceramic (turbine) turbos. Surely the maximum safe boost depends on the exhaust being used. To attain a certain level of boost, you need a certain flow and pressure gradient across the turbines. Hence, if you have higher back-pressure (e.g. using stock exhaust, downpipes and cat) you need higher pressure on the inlet to attain 1 bar and the blades are more at risk of shearing off. Using a 90-100mm decat turbo-back system, there is next to no back-pressure and hence the pressure on the inlet is less, meaning less risk to blades. Is this reasoning sound?

17th August 2006, 09:56 AM	#2 (permalink)
R34Nismo GTROC Member Join Date: Oct 2002 Location: United Kingdom Posts: 1,113	HEAT. __________________ ___________________ ..+ +.. HQ is Now Closed Note for Marketing Agencies - McDONALD'S Make your brown carrier bags green in colour so they blend in with the countryside after they've been thrown out of car windows.

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17th August 2006, 10:32 AM	#3 (permalink)
ExScoobyT GTR Register Member Join Date: Jan 2004 Location: `down sourfff Posts: 1,052	Its shaft torque that breaks ceramic wheels-off (assuming a good map with no det). As temp increases the torque limit does come down as well. More inlet boost = higher compressor tip-speed. Higher compressor tip-speed = more torque from the turbine and = higher shaft torque.

17th August 2006, 02:30 PM	#4 (permalink)
R33_GTS-t GTR Register Member Join Date: Apr 2005 Location: [510] days from disposing of Labour. BNFL are shit. One repossession, one (bank) window. Posts: 8,241	Cheers.

17th August 2006, 03:08 PM	#5 (permalink)
danok GTR Register Member Join Date: May 2006 Location: South East Posts: 151	No more than 1 bar on ceramics

18th August 2006, 09:32 AM	#6 (permalink)
SIHethers New Users Join Date: Feb 2006 Location: Newcastle Posts: 193	If it's shaft speed/torque that breaks them, then low exhaust back pressure will exacerbate this by increasing airflow, and hence compressor speed required to develop any given boost pressure, particularly as compressor efficiency drops at higher flow rates.