This is a much more interesting comparison than simply “which engine is stronger.” An E46 2JZ and E46 B58 are two different philosophies of building the same chassis.
The fundamental difference
2JZ E46: build a brutally capable mechanical machine.
B58 E46: build a modern BMW-like powertrain inside an old BMW chassis.
The second is technically more difficult because the B58 brings considerably more electronics and integration requirements.
1. The 2JZ E46 route
The basic architecture is:
2JZ-GTE → longitudinal manual/automatic transmission → custom driveshaft → E46 differential → rear wheels
The attraction is that you can keep the E46 relatively understandable.
Stage 1 — choose the E46
I’d start with a 330i/325i manual shell, rather than sacrificing a rare M3.
You want:
- straight chassis
- good suspension mounting points
- healthy subframe/rear floor
- good cooling system condition
- minimal corrosion
- complete wiring
- good brakes
The chassis condition matters more than the original engine.
2. Position the 2JZ correctly
This is one of the most important parts.
You don’t simply ask:
“Can I fit the engine?”
You ask:
“Can I put the engine in the correct location without destroying the E46’s balance?”
You need to determine:
- engine setback
- engine height
- oil-pan clearance
- steering-rack clearance
- firewall clearance
- bonnet clearance
- turbo position
- exhaust routing
- transmission angle
A poorly positioned 2JZ can turn an E46 into a nose-heavy monster.
A carefully positioned one can make a surprisingly coherent car.
3. Transmission becomes a major decision
For the 2JZ, the classic solution is a strong longitudinal manual transmission.
Then:
engine → gearbox → custom prop shaft → differential
You need to engineer:
- bellhousing/adapter
- flywheel
- clutch
- gearbox mount
- shifter location
- driveshaft
- differential
- half-shafts
And this is where your power target becomes important.
A 400–500 hp street car and a 800+ hp drag-oriented car are completely different projects.
4. B58 E46
Now the fun part.
The B58 route is:
B58 → modern BMW transmission → custom driveshaft → E46 differential
But there is a major difference.
The B58 doesn’t just want to run.
It wants to communicate.
You have:
- engine ECU
- electronic throttle
- direct injection
- VANOS
- Valvetronic
- electronic sensors
- transmission controller
- CAN bus
- immobilizer/security
- DSC/ABS
- instrument cluster
- fuel control
- cooling control
That’s why the B58 swap can be mechanically easier in some respects but electronically harder.
5. Why B58 makes an extraordinary E46
The B58’s biggest advantage isn’t simply horsepower.
It’s power density + response + modern control.
You potentially get:
3.0L I6
modern turbocharging
direct injection
Valvetronic
Double-VANOS
modern ECU
modern automatic transmission possibilities
inside a chassis that weighs dramatically less than modern M cars.
That combination is potentially very serious.
6. The hidden enemy: electronics
This is where the B58 project can become expensive.
A 2JZ can essentially be treated as:
engine + standalone ECU
A B58 wants to be treated as:
engine + ECU + transmission + CAN network + security + vehicle systems
You therefore need to decide very early:
Route A — standalone ECU
Simplifies some integration but potentially loses or complicates OEM functionality.
Route B — OEM BMW electronics
Potentially gives you much better integration, but requires considerably more engineering around the donor electronics.
For a sophisticated B58 E46, I’d favour using as much compatible OEM powertrain electronics as practical, rather than trying to make the entire engine behave like an old standalone racing engine.
7. Cooling becomes critical
Both cars need serious cooling once modified.
For either build:
radiator
intercooler
engine oil cooler
power-steering cooling
transmission cooling
should be considered as one thermal system.
But the B58 has an advantage in thermal-management sophistication.
The 2JZ has an advantage in simplicity and accessibility.
8. The real stakes: chassis
This is where people often get the swap backwards.
Suppose you build:
700 hp + 700 Nm
but leave the E46 with mediocre:
- suspension
- tyres
- brakes
- differential
- bushings
- cooling
- chassis reinforcement
You haven’t built a 700-hp E46.
You’ve built an E46 carrying a 700-hp problem.
The chassis must evolve with the engine.
9. The differential is particularly important
You want the drivetrain to behave as one system:
engine torque
↓
gearbox
↓
prop shaft
↓
LSD
↓
half-shafts
↓
tyres
The LSD becomes especially important because an E46 with serious turbo torque can overwhelm an open differential very quickly.
For a road/spirited-drive build, I would prioritize predictable LSD behaviour over simply selecting the strongest possible differential.
10. What does each car become?
2JZ E46
Character:
old-school + brutal + mechanical
You get:
- huge tuning ecosystem
- excellent high-power potential
- simple engine-management philosophy
- distinctive turbo character
- relatively straightforward aftermarket support
But:
- heavy engine
- older combustion technology
- less refined
- more heat at high output
- more difficult to achieve modern drivability
- potentially more front weight
B58 E46
Character:
OEM+ × Frankenstein × modern M-car
You potentially get:
- excellent low/mid-range torque
- sophisticated engine management
- modern turbo response
- excellent drivability
- high power density
- modern transmission possibilities
- much more refined power delivery
But:
- much greater electronic complexity
- donor-car dependency
- CAN-bus problems
- immobilizer/security integration
- expensive troubleshooting
- specialist calibration requirements
11. The three levels I’d consider
Level 1 — sensible street weapon
400–500 hp
This is where I’d start.
You don’t need to chase enormous numbers.
The objective becomes:
light E46 + strong torque + excellent suspension + excellent tyres + reliable cooling
This could be an extraordinarily entertaining car.
Level 2 — serious fast road
500–650 hp
Now the supporting systems become substantially more important.
I’d expect:
- serious cooling
- upgraded fuel system
- upgraded clutch/transmission
- LSD
- stronger driveshaft
- serious brakes
- suspension tuning
- chassis reinforcement
- proper engine management
At this level, the car stops being an ordinary modified E46.
Level 3 — extreme build
700+ hp
Now the question changes from:
“How much power can the engine make?”
to:
“How much power can the entire vehicle exploit?”
Tyres, differential, gearbox, driveshaft, cooling, suspension and chassis become the limiting system.
12. The most interesting choice
If your priority is the legendary build, I’d choose:
2JZ E46
because the engine itself becomes the centrepiece.
If your priority is:
maximum modern performance from an E46 chassis
I’d investigate:
B58 E46
because the combination of modern turbo technology and the relatively light E46 chassis is conceptually extremely strong.
But I would not start with the engine.
I’d start with the target vehicle:
E46 + target weight + target power + target gearbox + target differential + target use
Then work backwards.
The ultimate build philosophy
For a car intended for street + spirited driving + occasional circuit use, I wouldn’t chase 1,000 hp.
I’d rather build something like:
E46
→ lightweight but properly equipped
→ B58 or 2JZ around 450–550 hp
→ strong LSD
→ properly matched suspension
→ excellent brakes
→ appropriate tyre
→ optimized cooling
→ excellent ECU calibration
→ modest aero
→ strong chassis
That gives you something far more interesting than a dyno-number car:
a lightweight BMW with modern six-cylinder turbo power and enough traction/chassis capability to actually use it.
And that’s where the 2JZ E46 vs B58 E46 debate becomes fascinating: 2JZ is the more iconic engine swap; B58 potentially makes the more integrated modern performance machine.
