The real difference between A/r .68 and A/r .96?
06-05-2008, 12:01 PM
#1
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The real difference between A/r .68 and A/r .96? I am looking at a T-70 and it uses a/r .68
There is a .96 available but what is the real difference? Im only looking for around 550rwhp. Is the lower the a/r the faster it spools?
Should i stick with the .68?
There is a .96 available but what is the real difference? Im only looking for around 550rwhp. Is the lower the a/r the faster it spools?
Should i stick with the .68?
06-05-2008, 12:54 PM
#3
The 'A' = area of exhaust inlet
'R' = the distance from the center of the turbine to the center of the exhaust inlet
like this...
From another website...
A/R is the rated volumetric efficiency of a turbos 2 sections, so to speak. Imagine if you have a garden hose spraying water out at a pinwheel with the hose open ended, the pinwheel spins okay. Put a nozzle on it an the pinwheel will spin like mad.
There are issues with the nozzle on the end, you lose volume but gain pressure. With the nozzle off you gain volume, but lose pressure and you can't turn the pinwheel as much.
Simply put, on small displacement engines a smaller A/R is better, on large displacement engine a larger A/R is better due to exhaust volume.
A larger A/R will spool later and provide a higher power band, if your engine is capable of reaching the RPMS it should be used in.
Sooo a .68 might choke the motor some - at higher RPMs where it could be making more power (say above 5800-6000 rpm and +), but the .96 might be too much and make the car feel sluggish at lower speeds. This goes hand in hand with everything else in the combination. A turbo with a higher A/R wouldn't feel as 'sluggish' with more compression out of the motor or a with a camshaft that utilizes higher DCR and reduces overlap with higher cylinder pressures. Why not go with a .81 if you can find it? Don't just 'find a turbo', get one well suited for your application and power goals. You might PM Dr Turbo or another forum sponsor and see what they think for your goals.
'R' = the distance from the center of the turbine to the center of the exhaust inlet
like this...
From another website...
A/R is the rated volumetric efficiency of a turbos 2 sections, so to speak. Imagine if you have a garden hose spraying water out at a pinwheel with the hose open ended, the pinwheel spins okay. Put a nozzle on it an the pinwheel will spin like mad.
There are issues with the nozzle on the end, you lose volume but gain pressure. With the nozzle off you gain volume, but lose pressure and you can't turn the pinwheel as much.
Simply put, on small displacement engines a smaller A/R is better, on large displacement engine a larger A/R is better due to exhaust volume.
A larger A/R will spool later and provide a higher power band, if your engine is capable of reaching the RPMS it should be used in.
Sooo a .68 might choke the motor some - at higher RPMs where it could be making more power (say above 5800-6000 rpm and +), but the .96 might be too much and make the car feel sluggish at lower speeds. This goes hand in hand with everything else in the combination. A turbo with a higher A/R wouldn't feel as 'sluggish' with more compression out of the motor or a with a camshaft that utilizes higher DCR and reduces overlap with higher cylinder pressures. Why not go with a .81 if you can find it? Don't just 'find a turbo', get one well suited for your application and power goals. You might PM Dr Turbo or another forum sponsor and see what they think for your goals.
06-05-2008, 08:17 PM
#5
What would be the best size a/r for a good street/strip, twin turbo setup? Proposed turbo size are twin, 60-1 (turbonetics), on a 402/408 cid?
Sorry about "butting-in" on your thread.
