Fiat 128 SOHC engine

Designed by Aurelio Lampredi, the Fiat SOHC engine first appeared in the front wheel drive (FWD) Fiat 128 of 1969. The in line four cylinder engine comprised an iron block with an aluminium cylinder head containing a single overhead camshaft operating directly on both the inlet and exhaust valves in a reverse flow cylinder head configuration. The camshaft was driven by a belt rather than chain. The engine remained in production until about 2010 and grew in capacity over the years from 1100 cc (in the Fiat 128) to an eventual 1900 cc (in the Fiat Linea). The Fiat 130 V6 engine, also appearing in 1969, although having crossflow cylinder head, is directly related to the 128 SOHC engine, but with a 1.20 upscale in bore and stroke. It was gradually replaced by the Pratola Serra engine series starting from 1995 (and in the 1100 cc guise, by the FIRE unit of comparable displacement), although it was also converted to use a multivalve DOHC head, giving birth to the Torque engine, used until 2005.

The engine was designed as a transversely mounted FWD only power plant being the second engine/gearbox combination to exhibit the now standard transverse engine next to gearbox layout with unequal length driveshafts (the first was the Autobianchi Primula, the Mini had its gearbox in the sump of the engine). The exception to the engines FWD only design is its revolutionary use as a mid engine drive train in the Fiat X1/9. Also Tofaş has adapted 128 engines into its Fiat 131 based longitudinally mounted, front engine, rear wheel drive layout platform. Unusual for the time was the electrically driven fan, rather than it being powered directly by the engine. This engine was later used in the X1/9. The original 128/X1/9 engine is the only one of the family to have used the bore. The second generation used bores of either with strokes of giving four possible engine capacities. The final generation of SOHC engines standardised on a longer stroke with either an bore (giving respectively). The stroke with the bore was subsequently used by the early Torque engines, while the later Torque units used an bore with a stroke. + Valid engine bore/stroke combinations Stroke(mm) Bore (mm)   80 80.5 86 86.4 55.5 1116 1130 1290 1302 Capacity(cc) 63.9 1285 1301 1485 1499 67.4 1355 1372 1566 158178.41576159618211839 Key 1st generation   1st & 2nd generation   2nd generation   3rd generation  3rd generation & 1st generation Torque  2nd generation Torque  

+ Engine specification (by engine number) Engine Code Bore (mm) Stroke (mm) Capacity (cc)stated Capacity (cc)calculated Production(from to) BHP Notes 128. A.000 80 55.5 1116 1116 1969–1982 55 65 128 128. A1.000 86 55.5 1290 1290 1971–1978 75 85 128 Rally & Sport 128. AS.000 86 55.5 1290 1290 1972–1978 75 X1/9 1300 128. A.064 80 55.5 1116 1116 1971–2008 55 64 Zastava 101 128. A1.064 80 55.5 1116 1116 1979–1983 64 Zastava 101 128. A2.064 80 55.5 1116 1116 1988–2008 60 Zastava Koral/Yugo 128. AC.000 86 55.5 1290 1290 1989–1983 73 128. A7.064 86 55.5 1290 1290 1981–1986 65 128. A6.064 86.4 55.5 1298 1302 1987–2008 65 11. E1.064 80 55.5 1116 1116 1986–1998 60 13. E1.064 86.4 55.5 1298 1302 1986–1998 65 13. E3.064 86.4 55.5 1298 1302 1988–1998 65 Zastava Florida 11. MA.064 80 55.5 1116 1116 1998–2008 60 13. MA.064 86.4 55.5 1298 1302 1998–2008 65 131. C.000 80.5 67.4 1372 1372 1980–1984 70 131 Mirafiori 1.4 131. C2.000 86.4 67.4 1581 1581 1980–1984 85 131 Mirafiori 1.6CL 131. D1.016 86.4 67.4 1581 1581 1992–2002 96 Tofaş Doğan and Kartal 1.6 S, SL, SLX (carb) 131. D2.016 86.4 67.4 1581 1581 1995–2002 92 Tofaş Şahin S, Kartal 131. F3.016 86.4 67.4 1581 1581 1998–2002 96 Tofaş Doğan and Kartal 1.6 S, SLX (i. e., cat) 131. F4.016 80.5 67.4 1372 1372 1995–2002 82 Tofaş Şahin 1.4 138. A.000 80 55.5 1116 1116 1978–1985 60 Ritmo 60 138. A1.000 86.4 55.5 1301 1302 1978–1982 75 65 Ritmo 65 138. A2.000 86.4 63.9 1498 1499 1978–1982 75 85 X1/9 1500, Ritmo 75 138. A3.000 86.4 55.5 1301 1302 1982 75 Ritmo S75 138. A4.000 86.4 63.9 1498 1499 1980–1982 75 85 X1/9 1500, Ritmo S85 138. A5.000 86.4 55.5 1301 1302 1982–1985 70 Also 138. AS.000 138. B.000 80 55.5 1116 1116 1983–1985 55 Uno 55 138. B1.000 80 55.5 1116 1116 1982–1985 55 58 Ritmo Mk II 138. B2.000 86.4 55.5 1301 1302 1983–1986 68 70 Uno 70 138. B3.000 86.4 63.9 1498 1499 1982–1985 70 85 Regata 85S 146. A4.048 80 55.5 1116 1116 1985–1989 58,5 Uno 60 146. A2.000 80.5 63.9 1301 1301 1985–1989 105 Uno Turbo Mk I 146. A2.146 80.5 63.9 1301 1301 1987–1989 99 Uno Turbo Mk I (cat) 146. A2.246 80.5 63.9 1301 1301 1989–1991 101 Uno Turbo Mk II (cat) 146. A8.000 80.5 67.4 1372 1372 1989–1994 118 Uno Turbo Mk II 146. A8.046 80.5 67.4 1372 1372 1989–1993 111 Uno Turbo Mk II (cat) 146. C1.000 80.5 67.4 1372 1372 1989–1993 72 Uno 70SXie 149. A7.000 86.4 55.5 1301 1302 1986–1989 65 Uno 70SX 149. C1.000 86.4 63.9 1498 1499 1988 75 Uno 75 SX i. e. (cat)/Selecta 159. A2.000 80.5 67.4 1372 1372 1990–1993 76 Tipo/Tempra 1.4 (carb & i. e.) 159. A3.000 86.4 67.4 1581 1581 1990–1996 75 78 Tipo/Tempra 1.6 (carb & i. e.) 159. B9.000 86.4 67.4 1581 1584 1996 90 Tempra i. e. 160. A1.000 80.5 67.4 1372 1372 1988–1993 72 Tipo/Tempra 1.4 i. e. 160. A1.046 80.5 67.4 1372 1372 1992–1993 69 Uno Selecta 160. A2.000 86.4 67.4 1580 1581 1988–1993 83 Tipo/Tempra 1.6 (carb & i. e.) 176. A4.000 80.5 67.4 1372 1372 1993–1995 133 Mk I Punto GT (GT1), CR 7.8:1 176. A4.000 80.5 67.4 1372 1372 1995–1997 133 Mk I Punto GT (GT2), CR 7.8:1 176. B6.000 80.5 67.4 1372 1372 1997–1999 130 Mk I Punto GT (GT3), CR 9.0:1 176. A9.000 86.4 67.4 1581 1581 1994–1997 88 Mk I Punto Sporting & Cabrio 178. B2.016 80.5 67.4 1372 1372 1996–2002 71 Palio/Siena 1.4EL 178. B3.000 86.4 67.4 1581 1581 1996–2005 103 DOHC 16v, Palio/Siena/Albea 182. A4.000 86.4 67.4 1581 1581 1995–2002 103 DOHC 16v, Bravo/Brava/Marea/Multipla/Lancia Dedra 182. B6.000 80.5 78.4 1596 1596 2002–2005 103 DOHC 16v, Marea/Multipla/Stilo/Palio/Siena/Strada/Doblò/Lancia Lybra 310 A3.011 86.4 78.4 1839 1839 2008–2010 132 DOHC 16v, Brazilian Linea 1.9 16v Torque 835. C1.000 86.4 67.4 1581 1581 1989–1995 75 78 Tipo/Tempra 1.6 i. e. (Typ 160), Lancia Dedra Mk I (1.6 i. e.) 835. A1.046 86.4 67.4 1581 1581 1989–1994 75 78 Lancia Dedra Mk I (1.6 i. e.) 835. A1.000 86.4 67.4 1581 1581 1995–1997 90 Lancia Dedra Mk II (1.6 i. e.)

List of vehicles using variations of the Fiat SOHC engine.

The Fiat SOHC used the full gamut of induction techniques through its long production run. The original 128 and 138 series engines originally used a single down draught carburettor. The carburettor was normally of progressive twin choke design (two asymmetric sized chokes operated progressively) such as the Weber DMTR and DATR of the X1/9. Multi point fuel injection (MPI) was introduced late in the 138 series to help meet lowered emission requirements in the US. The original MPI system comprised a large cylindrical plenum running parallel to the engine with individual runners to each inlet port and a single throttle controlling air flow into the plenum. This plenum was pressurised in the Mk I Uno Turbo. The plenum was slightly redesigned to a more angular "box" shape for the 3rd Generation engines and was again pressurised for the Uno and Punto GT Turbo models. For the 3rd Generation engines the down draft carburettor was replaced with a Single point injection system (SPI) in the base level models. The SPI system mounts on a manifold similar to that of the carburetted models and looks, as well as acts, much like a single choke carburettor with a single throttle plate but no venturi and a centrally mounted single injector.

Tuning of the early MPI systems has previously been difficult as the electronic control systems are analogue making them difficult to "re map". Low cost DIY Fuel Injection (FI) controllers (such as MegaSquirt) have made it easier to alter the characteristics of the early MPI systems and release similar potential as the DCNF/DCOE carburettors. It is possible to "chip" the later digital MPI systems though aftermarket FI controllers again give greater flexibility.

Individual FI Throttle Bodies (TBs) are available for mounting to DCNF and DCOE manifolds as well as custom built FI systems which, with aftermarket controllers, give the most flexibility and control over fuelling out of all the options.

Motorcycle, or "bike" carburettors, being a modern and cost effective alternative to DCOE/DCNFs, have been adapted to work with the 128 derived engines. They potentially offer better control over fuelling than DCNF/DCOE, but their use on the Fiat SOHC engine is still in its infancy.

The camshaft was a main methods of varying the 128 series engines characteristics for different applications/markets. The high revving oversquare design of the 128 engine lends itself to high overlap high duration cam profiles better than more traditional square/under square engine designs without losing drivability. Though a beneficial characteristic for sports orientated engine the high overlap high duration cam design gives poor emissions output which was unacceptable under the tightened US emissions regulations. To remedy this (in addition to the introduction of MPI) camshafts for emission restricted markets featured asthmatic low lift, low duration, low overlap profiles totally unsuited to the nature of the 128 engine.

+ Standard production camshaft specifications Profile Duration(degrees) Overlap(degrees) Lift(mm) Clearance (mm)Inlet/Exhaust Application 12/52 52/12 244 24 1.1 L 128 European Specification 10/54 54/10 244 20 1.1 L 128 North American Specification 24/68 68/24 272 48 9.85 128 Rally 24/68 68/24 272 48 9.85 1300 X1/9 European Specification 10/54 54/10 244 20 1300 X1/9 North American Specification 12/52 52/12 244 24 1300 X1/9 Australian Specification 24/68 68/24 272 48 9.9 1500 X1/9 European Specification (carb) 10/54 54/10 244 20 1500 X1/9 North American Specification (FI) 10/54 54/10 244 20 1500 X1/9 Australian Specification (carb) 9/39 31/1 228 212 10 8 1.3 L Uno 0/30 40/10 210 230 10 8 1.3 L Uno Turbo 14/36 44/6 230 20 8.8 1.4 L Uno Turbo7/35 37/5222128.80.4/0.51.6 Tipo 244 9.20.4/0.51.1/1.3 "DMB" Zastava European Specification 256 9.2 1.6 90hp i. e. Punto/Tempra/Dedra

+ Fast road/race camshaft specifications Manufacturer Profile name Profile Duration(degrees) Overlap(degrees) Lift(mm) Clearance (mm)Inlet/Exhaust Application Kent FT7 35/67 67/35 282 70 10.33 0.20 / 0.20 NA fast road Kent FT8 52/76 76/52 308 104 10.82 0.20 / 0.20 NA race Piper BP270 33/67 67/33 280 66 9.80 0.20 / 0.20 NA fast road Piper BP285 36/72 72/36 288 72 10.40 0.20 / 0.20 NA fast road Piper BP300 39/71 71/39 290 78 11.18 0.25 / 0.25 NA race Piper BP320 53/83 83/53 316 106 11.18 0.25 / 0.25 NA race