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Across the broad array of message boards we see a large
amount of misinformation. Sadly this bad info can lead
somebody into purchasing the wrong part. One common bit
of internet hearsay is "The bigger the turbo the bigger the
wastegate!" So is this fact or myth? This write-up may
influence your next wastegate purchase.
Generally speaking running lower boost levels, requires a
larger wastegate. The theory is more exhaust gas needs to
diverted (wasted) away from the turbine wheel during low
boost conditions. While running high boost levels, a
majority of the exhaust needs to be directed into the
turbine wheel to spool the turbocharger.
Example A: A GT42R turbocharger on a 1.6L engine would
require a smaller wastegate because a majority of the
exhaust flow from the engine would be required to spool the
turbine wheel.
Example B: A GT25R on a 3.0L engine attempting to run low
boost pressure would require a large wastegate because a
majority of the exhaust flow needs to be diverted away from
the turbine wheel to keep the turbo from boost creep or over
boosting.
The real life applications show here are performed on a dyno
with race gas. Use of 91 octane gasoline may result in more
boost creep, due to the necessity of running less ignition
timing advance. Less ignition timing advance raises EGT
temperatures causing the turbo to spool more agressively.
Full Function is not responsible for any damage or injury
that may occur by the replication of these tests. The tests
do not express the opinions of Full Function. The tests
supply real data and help explain the turbo/engine/wastegate
relationship.
The following data logs shown is a real life application of
example B.
Setup:
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