FH6 Best Engine Swaps — Which Are Actually Worth It
Engine swaps are the most expensive upgrade category in Forza Horizon 6 — anywhere from 25,000 to 500,000 credits — and about 60% of them aren't worth the money. The wrong swap costs you PI budget, adds weight in the wrong place, ruins the car's balance, and for what? Twenty horsepower you could've gotten from bolt-ons for half the cost and zero PI impact.
But the right swap transforms a car. I'm talking about taking a sleepy C-class coupe and turning it into an A-class monster that gaps purpose-built sports cars. I've swapped engines in about 200 cars across my FH6 garage. Here's what actually works, organized by swap type, with specific car recommendations and PI cost analysis.
How Engine Swaps Actually Work in FH6
Before we get into which swaps are best, you need to understand the mechanics. An engine swap isn't just adding horsepower. It changes the car's weight, weight distribution, engine position, sound, redline, torque curve, and most importantly the PI calculation. The game recalculates your car's PI from scratch when you swap — some swaps actually lower your PI at the same power level because the engine is lighter or more efficient.
Swap cost: credits vary by engine type. A basic inline-four swap might be 25,000 credits. A Racing V12 swap is 500,000. The swap cost is per car — if you swap the same engine into ten different cars, you pay ten times. There's no discount for loyalty. Drivetrain swaps are separate — you can keep the stock engine and just swap to AWD, or swap the engine and keep RWD. They're independent decisions. Swapping both (engine + drivetrain) is expensive but sometimes necessary for a competitive build.
Weight change: not shown on the upgrade screen. This is criminal. The LS V8 swap into a Mazda MX-5 adds about 120 kg over the front axle. The 4-Rotor swap into the same car adds maybe 30 kg. The PI screen won't tell you this — you have to learn it through testing or guides like this one. Engine position matters too. Swapping a heavy V12 into a front-engine car that already understeers is making a bad problem worse. Swapping a lightweight racing engine into a mid-engine car preserves the balance.
Sound: look, I know this is subjective. But if I'm going to spend 200 hours in a car, I want it to sound good. The Lamborghini V12 swap screams like an opera singer. The 6.2L LS sounds like thunder. The 4-Rotor sounds like an angry chainsaw that went to finishing school. The 1.6L Turbo Rally sounds like a hair dryer full of bees. Some swaps are worth doing just for the noise, results be damned. I won't tell anyone.
S-Tier Swaps — Always Worth It
6.5L V12 (Lamborghini Aventador Engine)
This is the nuclear option. 700+ hp naturally aspirated, revs past 8,500 RPM, and the sound is worth the 500,000 credits all by itself. The Aventador V12 swap is available for most European sports cars and some JDM platforms. It's heavy — adds about 150-180 kg to most cars — but the power more than compensates. Best recipients: any front-engine GT car that needs personality (Aston Martins, Jaguars, older BMWs). The swap transforms a DB11 from a cruiser into a supercar killer. It also works brilliantly in the Toyota Supra MK4, turning the JDM legend into something that sounds like an Italian supercar with Japanese reliability. The internet gets very angry about this. Do it anyway.
PI cost: significant. The V12 swap will push most cars up one full class (A to S1, S1 to S2). You're committing to a higher class when you do this swap, so plan your build accordingly. Don't V12-swap a car and then try to de-tune it back to a lower class — you'll end up with a restricted engine that makes less power than a well-tuned stock motor at the same PI. Use this swap when you want to move a car into S1 or S2 permanently.
Racing V12 (Ferrari F50 GT Engine)
The Racing V12 is lighter than the Lamborghini V12, revs higher (9,500+ RPM), and makes about 650 hp naturally aspirated. It's derived from the Ferrari F50 GT's 4.7-liter V12 — the race car Ferrari built and then cancelled because they decided a road-legal F50 was enough. It costs 500,000 credits. Best recipients: lightweight chassis that can handle high RPM power delivery. The Lotus Exige with a Racing V12 is a tiny British car with an Italian heart making S1 power — it's completely insane and I love it. The Mazda RX-7 FD with a Racing V12 loses the rotary character but gains a reliability joke and 300 extra horsepower. Available for most mid-engine and front-engine sports cars.
The Racing V12's advantage over the Lamborghini V12 is weight and RPM. It's about 40 kg lighter and the extra 1,000 RPM of rev range gives you more flexibility with gearing. The Lambo V12 makes more torque down low. If the car is light and nimble, take the Racing V12. If the car is heavier and needs the torque, take the Lambo V12.
4-Rotor Racing (Mazda 787B Engine)
The 4-Rotor Racing engine is the crown jewel of swaps for rotary fans and honestly for anyone who likes engines that sound like nothing else on earth. Based on the Mazda 787B's R26B four-rotor — the only rotary engine to win Le Mans. In FH6 it revs past 10,000 RPM, makes about 500 hp naturally aspirated, and weighs almost nothing. About 40-50 kg lighter than most piston engine swaps.
Available for most Mazda platforms and some lightweight sports cars. Best recipients: Mazda RX-7 FC, RX-7 FD, RX-8 R3, Mazda MX-5 (any generation), and surprisingly the Honda S2000. The RX-7 FD with a 4-Rotor swap at 800 PI is one of the fastest A-class cars in the game — the engine is so light that the car's weight distribution stays near-perfect and the high RPM range means you can run shorter gearing for better acceleration. The MX-5 NA with a 4-Rotor swap weighs under 900 kg and makes 500 hp — that's a power-to-weight ratio in supercar territory. Cost: 250,000 credits. Worth every one.
A-Tier Swaps — Great in the Right Car
6.2L V8 (LS3)
The LS is the universal donor engine and it shows up as a swap option for roughly 60% of the car list. 430 hp stock, pushrod design keeps the engine physically compact (fits in tiny engine bays), and the aftermarket support in-game is massive — cams, supercharger, twin turbos, you can take an LS from 430 hp to 1,500+ hp depending on PI budget. But it's heavy. Adds 100-140 kg to most platforms, and almost all of that weight goes over the front axle.
Best recipients: cars that were already front-engine and already heavy enough that the weight gain is marginal. The Nissan Silvia S15 with an LS swap is a drift missile legend. The Mazda MX-5 NA with an LS swap is the classic "monster Miata" build — it understeers more but the straight-line speed is hilarious. The Toyota GT86 with an LS finally has the power the chassis always deserved. Avoid LS-swapping mid-engine or rear-engine cars — the weight distribution goes from "balanced" to "why is my car trying to kill me." Cost: 150,000 credits.
Racing V8 (Ferrari-Derived)
The Racing V8 is a flat-plane crank, high-revving monster derived from Ferrari's motorsport program. About 550 hp naturally aspirated, revs to 9,000+ RPM, and weighs significantly less than the LS — only about 60-80 kg added. Sounds like a proper racing engine. Best recipients: European sports cars that need a power boost without ruining the handling. The Alfa Romeo 4C with a Racing V8 is a baby supercar. The BMW M3 E30 with a Racing V8 is a DTM tribute. The Porsche Cayman GT4 with a Racing V8 fixes the one thing wrong with that platform (not enough power for the chassis capability).
This swap is expensive at 350,000 credits, but for the right cars it's transformative. The power delivery is peaky — you need to keep the engine above 5,000 RPM to make power — so pair it with short gearing and a car that can handle high corner speeds.
1.6L Turbo Rally (WRC-Derived)
Don't sleep on this one. The 1.6L Turbo Rally engine is based on modern WRC power units — small displacement, massive turbo, anti-lag system. It makes about 380 hp at full boost but the real advantage is weight. It adds almost nothing — maybe 10-20 kg over the stock engine in most cases, and in some cars it's actually lighter. The torque curve is a cliff face: nothing below 3,000 RPM, then everything at once. You drive it with your right foot pinned and your left foot modulating.
Best recipients: lightweight classic rally cars and hot hatches. The Ford Escort RS with this swap is period-correct and devastating in A class dirt racing. The Peugeot 205 Turbo 16 with this swap is a Group B monster. Any sub-1,100 kg chassis that needs more power without the weight penalty of a larger engine. This is the swap for dirt and mixed-surface builds where weight transfer matters more than raw horsepower. Cost: 100,000 credits. Bargain.
B-Tier Swaps — Situational
2JZ-GTE (Toyota Supra Engine)
The 2JZ swap is iconic and I want it to be S-tier, but in FH6 it's situational. The 3.0-liter inline-six makes about 320 hp stock but the whole point of a 2JZ is the tuning potential — with a single turbo conversion you can push 800+ hp. The problem: the swap itself costs 200,000 credits and you still need to buy all the power upgrades separately. By the time you've built a 2JZ to its potential, you've spent 400,000+ credits total and the car is in S1 class. For the same money you could have swapped a V12 and made more power with a better torque curve.
Where the 2JZ makes sense: JDM purist builds, cars where period-correct engine choices matter to you (it doesn't affect lap time but it affects soul), and any Toyota platform where the swap is a bolt-in upgrade rather than a radical conversion. The Toyota GT86 with a 2JZ is a canonical build. The Toyota AE86 with a 2JZ is a death trap and I respect anyone who drives it.
Electric Motor Swap
FH6 added electric motor swaps and they're weird. Instant torque, no gears (single-speed transmission), silent except for tire noise. The Rimac-derived swap makes about 600 hp and weighs a ton — battery packs are heavy. Available for a surprisingly wide range of cars. Best recipients: cruisers and show cars where the novelty is the point. Competitively, electric swaps are slower than equivalent gas engine swaps because the single-speed transmission limits top speed and the weight hurts handling. Fun for messing around, not for racing. Unless you're doing a very specific build for a very short track where instant torque matters more than anything else.
Hidden Gem Swaps Nobody Talks About
The 3.0L Racing V6 swap into the Honda NSX-R (1992) is absurd. It's lighter than the stock C30A, revs past 9,000 RPM, and makes about 400 hp at A class PI. The car retains its perfect mid-engine balance and gains 120 hp. This swap turns an already-great A class car into an A class dominator. Cost: 175,000 credits.
The 5.2L V10 (Lamborghini Huracan engine) swap into the Audi RS6 Avant is a 200-mph station wagon with all-wheel drive and a naturally aspirated V10 screaming behind the front axle. It's completely pointless and completely wonderful. The PI cost pushes it to S1 but the RS6 chassis can handle it — surprisingly capable on high-speed circuits. Cost: 300,000 credits.
The 2.6L 4-Rotor swap into the Mazda RX-3 is a tiny 1970s coupe with a Le Mans engine and a curb weight under 900 kg. It's the most intense driving experience in the game — every corner is an event, every straight is a prayer. Not competitive at the top level but genuinely the most fun I've had in FH6.
Drivetrain Swap Compatibility
Engine swaps and drivetrain swaps are independent decisions but they interact. The most important rule: if you're swapping a heavy engine into a RWD car, consider an AWD swap to manage the power. LS-swapped Miata with RWD is a drift car. LS-swapped Miata with AWD is a grip monster. Same engine, completely different car.
Not every drivetrain swap is available for every car. Generally: AWD swaps are available for most platforms but cost 50,000-150,000 credits and add 50-80 kg. RWD conversions (from AWD) are available for some cars — the Nissan GT-R and Mitsubishi Evo can both go RWD, which is sacrilege but creates very entertaining drift builds. FWD to RWD conversions exist for some hot hatches — the Honda Civic Type R with RWD is a budget drift car. Check the conversion menu for each specific car; compatibility is car-by-car, not engine-by-engine.
When Not to Swap
Some cars have such good stock engines that a swap is a downgrade. The Porsche 911 GT3 RS's 4.0-liter flat-six revs to 9,000 RPM and makes perfect linear power — any swap adds weight and ruins the rear-engine balance. The Ferrari 488 Pista's 3.9-liter twin-turbo V8 is already making 710 hp and responds well to bolt-ons — a swap costs PI that's better spent on handling. The Koenigsegg Jesko's twin-turbo V8 is the best engine in the game and swapping it is a crime against engineering. Know when to leave well enough alone.
Rule of thumb: if the stock engine can reach your target power level with bolt-ons (intake, exhaust, cams, turbo upgrade), don't swap. Bolt-ons cost less PI than a full engine swap and preserve the car's character. Save engine swaps for cars where the stock engine physically cannot reach the power level you need, or where the swap adds something meaningful beyond horsepower (weight reduction, higher redline, better sound).