Service Manual

ISB, ISBe and QSB (Common Rail [...] Crankcase Blowby, Measure
Section 14 - Engine Testing - Group 14 Page 14-31
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Blowby Conversion Table (7.67-mm [0.302-in] orifice, Blowby Tool, Part Number 3822566)
mm [in] of H
2
O Liter [cfm] per Minute
228.6 [9] 172 [6.074]
254 [10] 180 [6.357]
279.4 [11] 187 [6.604]
304.8 [12] 193 [6.816]
330.2 [13] 200 [7.063]
355.6 [14] 206 [7.275]
381 [15] 211 [7.451]
406.4 [16] 217 [7.663]
431.8 [17] 222 [7.840]
457.2 [18] 226 [7.981]
482.6 [19] 229 [8.087]
508 [20] 235 [8.299]
533.4 [21] 239 [8.440]
558.8 [22] 242 [8.546]
584.2 [23] 246 [8.687]
609.6 [24] 248 [8.758]
The following chart contains general blowby specifications
for MidRange engines. Due to the wide variety of engine
types, configurations, and ratings, these specifications are
intended to only be used as a guide to help identify if a
problem exists. These specifications are not intended to
be used as engine condemnation limits.
NOTE: If internal engine damage is suspected to be the
cause of the excessive blowby condition, other steps can
be taken to confirm this.
Measuring blowby must only be considered when
confirming engine break-in after a rebuild or if another
symptom is present. These symptoms can include:
• Excessive carryover (oil out of the crankcase breather
tube)
• High crankcase pressure (for engines equipped with a
crankcase pressure sensor)
• Low power
• Oil consumption
• Exhaust smoke.
If no other symptom is present, blowby measurements
need not be taken.