Right now, ive got all 3, as theres always been some confusion about what the differences are.
1.6 > 1.8 > 1.8RS (the angle that the 1.8 one is sat at makes ports look small…)
(No mark) 90bhp
1.6 one is pretty puney, small throttle body. small ports etc
(SO) – 105/115bhp
1.8 one has bigger ports and bigger throttle body.
(ok there should be an image here but i seem to of misplaced it)
(HO) 130bhp
1.8 rs one has THE SAME size ports as the 1.8 one, however, the throttle body is HUGE compared to the others. The manifold generally looks beefier/wider all the way from TB to end of port, and looks like it is able to flow more air than the 1.8 one.
SO vs HO
With the throttle bodys, we all know that you can bolt up a 2.0 one with some modifications.
Comparison Chart.
| 1.6 Inlet (No marking) 90PS | 1.8 Inlet (SO Marking) 105/115PS | 1.8 Inlet (HO Marking) 130PS | |
| Bore Size (Manifold) | 4.4cm x 2.4cm | 4.6cm x 2.8cm | 4.4cm x 3.0cm |
| Bore Size (Sandwhich Plate Manifold Side) | 4.6cm x 2.4cm | 5.0cm x 3.3cm | 5.0cm x 3.3cm |
| Bore Size (Sandwhich Plate Head Side) | 4.0cm x 2.2cm | 4.4cm x 2.7cm | 4.4cm x 2.7cm |