NOₓ Tier I / II / III Limits

Contents

Formulas

Tier I (engines built 2000–2010):

$$ L^{(I)}(n) = \begin{cases} 17.0 & n < 130 \ 45 n^{-0.2} & 130 \le n < 2000 \ 9.8 & n \ge 2000 \end{cases} $$

Tier II (engines built ≥ 2011, global):

$$ L^{(II)}(n) = \begin{cases} 14.4 & n < 130 \ 44 n^{-0.23} & 130 \le n < 2000 \ 7.7 & n \ge 2000 \end{cases} $$

Tier III (engines built ≥ 2016, inside NECAs):

$$ L^{(III)}(n) = \begin{cases} 3.4 & n < 130 \ 9 n^{-0.2} & 130 \le n < 2000 \ 2.0 & n \ge 2000 \end{cases} $$

Symbol	Meaning	Unit	Source
$L^{(t)}$	Maximum NOₓ rate at tier $t$	g/kWh	MARPOL VI Reg 13
$n$	Rated engine speed	rpm	engine nameplate