Turbo restrictor choking speed

[PS]

Hi guys,


Can anybody tell me at what engine RPM their restrictor choked when using a turbocharger? I'm asking about the 600cc engines. Also, what kind of boost did you see when running a Garrett GT12 or GT15V? We are looking into a turbo.

Thanks.

PS

[Frank]

you will "choke" the restrictor when the static pressure immediately downstream of the 20 mm orifice is approximately 0.9 times the upstream pressure.. therefore it's 10 KPa vacuum (40 inches of water)

if you have a very short restrictor (small outlet area) there will loss that might decrease the static pressure (vaccuum) required at the pump inlet dramatically..

if you have a restrictor that performs very well, like the ones needed in naturally aspirated engines, with big area at outlet (i suggest at least 46 mm OD and about 4-6 deg outlet angle), then loss will be quite small.. and you will require about 10.5 KPa vacuum (42 inches of water) to choke the device

the mass flow rate through the device will reach the equivalent of around 135 CFM(stp).. (when "choked")

from this information you can calculate the requirements of the pump/blower/turbo/whatever, at high rpm

if your "turbo/whatever" tries to pull greater than 10.5 kpa vacuum (at high rpm) it will do nothing except create heat.. and use energy ("turbo") and waste energy ("blower".. and somewhat "turbo")

in other words.. you wont be able to create "boost" at high rpm

at low rpm is another story... you will be able to create "boost".. heaps (if you desire) at low rpm.. again raising the power requirements of the device above the previous calculation

regards

frank

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[This message was edited by Frank on August 19, 2003 at 12:25 PM.]