Engine Conversions

Most of the cars in Forza 5 have one or more engine conversion options in the Upgrade Shop. Swapping an engine has the basic effect of improving performance through increased horsepower, (and in some cases can reduce weight) but also offers the option of different aspirations and cylinders. Although the engines aren’t named as in previous Forza versions, you can see additional description about the engine by pressing A (Buy and Install - you’ll have the option to confirm or cancel) in the Engine Swap screen. Following is a list of the engine swaps available as of January 2014. Information is listed by: engine specs, description and the game car it matches, stock aspiration and conversion options, purchase price, and cars it can swap into:

158 KW / 202 Nm (212 hp / 149 lbft) - 2.0L I4 - VVT (Honda Civic Type-R ‘04)
278 KW / 600 Nm (373 hp / 442 lbft) - 1.6L I4 - Turbo Rally (not in Forza but configuration matches the Ecoboost in the Ford Fiesta WRC)
227 KW / 394 Nm (305 hp / 290 lbft) - 2.5L F4 - Turbo (Subaru WRX ‘11)
242 KW / 475 Nm (325 hp / 350 lbft) - 5.7L V8 - (Chevy Camaro ‘02)
265 KW / 400 Nm (355 hp / 295 lbft) - 3.0L F6 - (actually 3.8L. No exact match in Forza)
244 KW / 398 Nm (327 hp / 293 lbft) - 2.6L I6 - TT (Nissan Skyline R34 ‘02)
248 KW / 366 Nm (332 hp / 270 lbft) - 3.7L V6 - VVT (Nissan 370Z)
248 KW / 355 Nm (333 hp / 262 lbft) - 3.2L I6 - (BMW M3 ‘05)
354 KW / 364 Nm (475 hp / 268 lbft) - 3.0L V8 - Racing (Ariel Atom)
419 KW / 540 Nm (562 hp / 398 lbft) - 5.2L V10 - (Lamborghini Gallardo LP570-4 Superleggera)
419 KW / 540 Nm (562 hp / 398 lbft) - 4.5L V8 - (Ferrari 458 Italia)
485 KW / 657 Nm (690 hp / 484 lbft) - 6.0L V12 - (Ferrari Enzo)
317 KW / 664 Nm (425 hp / 490 lbft) - 7.0L V8 - H (Dodge Challenger ‘70, Charger ‘69, Plymouth Cuda)
615 KW / 882 Nm (825 hp / 650 lbft) - 5.9L V8 - Racing (American Stock Car in FM4)
515 KW / 608 Nm (690 hp / 448 lbft) - 2.6L 4 Rotor - Racing (Mazda #55 787B)

List compile by ManteoMax and originally posted on FM.net

158 KW / 202 Nm (212 hp / 149 lbft) - 2.0L I4 - VVT (Honda Civic Type-R ‘04)
normally aspirated (Turbo, Centrifugal Supercharger)
12,000 cr
Available in:

   Abarth 500 esseesse
   Alfa Romeo Giulia Sprint GTA Stradale
   BMW 2002 ‘73
   Honda Civic ‘97 (and stock ‘04)
   Kia cee’d
   Lotus Elan
   Mazda Miata ‘94
   MINI Cooper ‘65
   Nissan 240SX, Datsun 510
   Toyota MR2 SC ‘89, Sprinter Trueno

278 KW / 600 Nm (373 hp / 442 lbft) - 1.6L I4 - Turbo Rally (not in Forza but configuration matches the Ecoboost in the Ford Fiesta WRC)
Turbo (no conversions)
28,000 cr
Available in:

   Abarth 500 esseessee
   Acura RSX
   Alfa Romeo Giulietta Quadrifoglio Verde
   BMW 2002 ‘73, M3 ‘91
   Citroen DS3
   Dodge SRT4
   Eagle Talon
   Ford Escort ‘77, Escort ‘92, Fiesta ‘14, Focus ‘09, Focus ‘13, Sierra ‘87
   Honda Civic ‘97, Civic ‘04, Civic ‘07
   Hyundai Veloster
   Kia cee’d
   KTM X-Bow
   Lancia 037, Delta S4
   Mazda 3 ‘10
   Mercedes 190E
   MINI JCW
   Mitsubishi Eclipse, Lancer VI ’99, VIII ‘04, X ‘08
   Peugeot 205, 308
   Renault Megane
   Scion TC
   Subaru BRZ, Impreza ‘98, WRX ‘04, WRX ‘05, WRX ‘11
   Toyota Sprinter, Celica ‘94, Celica ‘03, GT86
   Vauxhall Astra

227 KW / 394 Nm (305 hp / 290 lbft) - 2.5L F4 - Turbo (Subaru WRX ‘11)
Turbo (no conversions)
22,000 cr
Available in:

   Volkswagen Beetle ‘63

242 KW / 475 Nm (325 hp / 350 lbft) - 5.7L V8 - (Chevy Camaro ‘02)
normally aspirated (Turbo, Twin Turbo, Roots Supercharger, Centrifugal Supercharger)
26,000 cr
Max. upgraded power: 924 hp / 807 torque (twin-turbo)
Available in:

   AMC Javelin
   BMW 2002 ‘73, 1M, M1, M3 ‘91/‘97/‘05, Z4
   Buick Regal
   Chevy Camaro ‘69/’70/’79/’90/’02, Chevelle ‘70, Corvette C1/C2/C3, El Camino, Impala, Nova
   Dodge SRT4, Challenger ‘70
   Ford Escort ‘77/’92, Fiesta ‘14, Focus ‘09/’13, Sierra, Mustang ‘69, Cobra ‘93/’95
   GMC Syclone
   Honda S2000
   Hyundai Genesis Coupe Track
   Infiniti IPL
   Mazda Miata ‘94/’13, RX-7, RX-8
   Mercury Cougar
   Nissan 240SX, Datsun 510, 370Z, Fairlady ‘69/’03, GT-R ‘12, Skyline ‘71/’93/’97/’02, Sylvia
   Oldsmobile 442
   Plymouth Cuda
   Pontiac Firebird ‘69/’73/’77/’87, GTO ‘69
   Subaru BRZ, Impreza ‘98, WRX ‘04, WRX ‘05, WRX ‘11
   Toyota Sprinter, GT86, Supra RZ
   Volkswagen Beetle ‘63

265 KW / 400 Nm (355 hp / 295 lbft) - 3.0L F6 - (actually 3.8L. No exact match in Forza 5)
normally aspirated (Twin Turbo for zero credits)
25,000 cr
Available in:

   RUF CTR, CTR2, Rt12 (drops the Rt from A to B class)
   Subaru BRZ, Impreza ‘98, WRX ‘04, WRX ‘05, WRX ‘11
   Toyota GT86
   Volkswagen Beetle ‘63

244 KW / 398 Nm (327 hp / 293 lbft) - 2.6L I6 - TT (Nissan Skyline R34 ‘02)
Twin Turbo only
23,000 cr
Max. upgraded power: 748 hp / 585 torque (twin turbo)
Available in:

   BMW M3 ‘97/’05
   Hyundai Genesis Coupe Track
   Infiniti IPL
   Nissan 240, Datsun 510, 370, Fairlady ‘69/’03, Skyline ‘71/02, Sylvia
   Toyota Sprinter Trueno

248 KW / 366 Nm (332 hp / 270 lbft) - 3.7L V6 - VVT (Nissan 370Z)
naturally aspirated (Twin Turbo, Roots Supercharger, Centrifugal Supercharger)
24,000 cr
Max. upgraded power: 875 hp / 616 torque (twin turbo)
Available in:

   Abarth 500 esseessee
   Acura RSX, Integra
   Alfa Romeo Giulietta Quadrifoglio Verde, Giulia Sprint GTA
   Citroen DS3
   Dodge SRT4
   Eagle Talon
   Ford Escort ‘77/’92, Fiesta ‘14, Focus ‘13, Sierra
   Honda Civic ‘97/’04/’07, S2000
   Hyundai Veloster
   Jaguar E-Type
   Kia cee’d
   KTM X-Bow
   Lancia 037, Delta S4
   Lotus Elan, 2-Eleven
   Mazda 3, Miata ‘94/’13
   Mercedes A45
   MINI JCW
   Mitsubishi Eclipse, Lancer VI ‘99
   Nissan Datsun 510, 370Z, Fairlady ‘69
   Peugeot 205, 308
   Renault Megane
   Scion TC
   Toyota Sprinter, Celica ‘94/’03, MR2 ‘89/'95
   Vauxhall Astra
   Volkswagen Golf ‘92/’10, Rabbit, Scirocco

248 KW / 355 Nm (333 hp / 262 lbft) - 3.2L I6 - (BMW M3 ‘05)
naturally aspirated (Turbo, Centrifugal Supercharger)
24,000 cr
Available in:

   BMW 2002 ‘73, M3 ‘91/’05
   Mercedes 190E, 300 SL
   Nissan Skyline ‘71

354 KW / 364 Nm (475 hp / 268 lbft) - 3.0L V8 - Racing (Ariel Atom)
naturally aspirated (Twin Turbo)
38,000 cr
Available in:

   Caterham R500
   KTM X-Bow
   Lotus 2-Eleven, Exige S

419 KW / 540 Nm (562 hp / 398 lbft) - 5.2L V10 - (Lamborghini Gallardo LP570-4 Superleggera)
naturally aspirated (Twin Turbo, Centrifugal Supercharger)
46,000 cr (+39,600 twin turbo and full upgrades)
Max. upgraded power: 917 hp / 627 toruqe
Available in:

   Audi RS3, RS4, RS5, RS7, S4, Sport quattro, TT RS
   BMW 1M, M1, M3 ‘91/’97/’05/’08, M5 ‘03/’12, M6, X5, Z4
   Honda NSX ‘92/’05
   Lexus ISF
   Toyota Supra RZ

419 KW / 540 Nm (562 hp / 398 lbft) - 4.5L V8 - (Ferrari 458 Italia)
naturally aspirated (Twin Turbo, Centrifugal Supercharger)
46,000 cr (+26,800 for twin turbo and full upgrades)
Max. upgraded power: 914 hp / 615 torque (twin turbo)
Available in:

   Alfa Romeo Giulia Sprint GTA
   Aston Martin DB5, DBS, Vanquish
   Audi R8 5.2, R8 V10+, RS3, S4, Sport quattro, TT RS
   Ferrari California, 458, 512
   Ford R200
   Honda NSX ‘92/’05
   Jaguar E-type
   Lancia Delta S4
   Lotus Esprit, Exige
   Mercedes 190E, A45
   Renault Sport Clio V6
   RUF CTR, CTR2, Rt12
   TVR Sagaris

485 KW / 657 Nm (690 hp / 484 lbft) - 6.0L V12 - (Ferrari Enzo)
naturally aspirated
55,000 cr
Available in:

   Alfa Romeo 8C
   Aston Martin DB5
   Audi R8 5.2, R8 V10+
   BMW 1M, M1
   Ferrari 250 GTO/TR/California, 430, 458, 512, California, Challenge Stradale, Enzo, F355, F40, GTO
   Ford GT
   Jaguar E-type, XKR
   Lamborghini Gallardo, Miura
   Land Rover Range Rover
   Lotus Esprit
   Maserati GranTurismo S
   McLaren MP4-12C
   Mercedes 300SL, C63, SLK55, SLR, SLS
   Saleen S7

317 KW / 664 Nm (425 hp / 490 lbft) - 7.0L V8 - H (Dodge Challenger ‘70, Charger ‘69, Plymouth Cuda)
naturally aspirated (Twin Turbo, Roots Supercharger)
33,000 cr
Max. upgraded power: 799 hp / 800 (twin turbo)
Available in:

   AMC Javelin
   Buick Regal
   Chevy Camaro ‘69/’70/’79/’90/’02, Corvette ‘60/’70/’02, Nova
   Chrysler 300
   Dodge Challenger ‘12, Charger ‘69/’12
   Ford GT40, Mustang ‘69, Cobra ‘93/’95
   GMC Syclone
   Holden HSV
   Pontiac Firebird ‘77/’87

615 KW / 882 Nm (825 hp / 650 lbft) - 5.9L V8 - Racing (American Stock Car in FM4)
naturally aspirated only
60,000 cr
Max. upgraded power: 994 hp / 783 torque
Available in:

   AMC Javelin
   Buick Regal
   Cadillac CTS
   Chevy Camaro ‘69/’70/’79/’90/’02/’12/’12 #88, Chevelle, Corvette ‘60/’67/’70/’02/’09, El Camino, Impala, Nova
   Chrysler 300
   Dodge Challenger ‘70/’12, Charger ‘12
   Ford F150, GT40, Mustang ‘69, GT500 ‘07/’13, Cobra ‘93/’95/’00
   GMC Syclone
   Holden HSV
   Jeep Grand Cherokee
   Mercury Cougar
   Oldsmobile 442
   Plymouth Cuda
   Pontiac Firebird ‘69/’73/’77/’87, GTO ‘69
   Saleen S7
   Shelby 427, Daytona

515 KW / 608 Nm (690 hp / 448 lbft) - 2.6L 4 Rotor - Racing (Mazda #55 787B)
naturally aspirated only
60,000 cr
Available in:

   Mazda Miata ‘94/’13, RX-7, RX-8
   Nissan 240SX, Syliva

Those with the "Car Pass" feel free to list the swaps available on the new cars and I will add them above.