Suggestions for modifying an E46 M3

I'm going to start modifying my M3.

My biggest problem is can I up the power and torque substantially without forced induction of any kind?

I know G-power have a supercharger kit that can get 525hp and 600Nm, but can I get similar figures while keeping the engine NA.

Weight reduction is easy. I'm having new rims, brakes, tyres, springs, dif, exhaust and air filters.

My goal is a car under 1300kg and at least 500bhp. 0-62 in 4.0s or less, and a sub 12 quarter mile while still handling like it's on rails around a track.

I'd appreciate any suggestions.

500 Hp out of such a small engine will be very hard if you want to keep it NA.

You would have to increase the compression so hight that only race fuel can be used and you would have to use some very agresive cams which might not even work with Vanos(so might have to disable it).

The best answer is to go FI, true for that kind of power sone new internals would be recomended(at lest some low CR pistons), but you would end up with a much better powerband than NA and better drivability.


A turbo kit sholuld be the best solution IMO because of its flexibility and efficiency.

good tip. I forgot to mention, a friend was talking to me about titanium pistons or forged pistons with ceramic caps. I know nothing about that. But he said they can take a lot more than the current ones.

Also, what about boring the engine to make it bigger capacity. This friend (he's a BMW mechanic) said you can bore it out to about 3.6L.

But why would you choose turbo over supercharger? And being a SMG gear box, how would turbo lag affect the transmission management system? Probably some fancy tinkering involved (launch control!!!).

good tip. I forgot to mention, a friend was talking to me about titanium pistons or forged pistons with ceramic caps. I know nothing about that. But he said they can take a lot more than the current ones.

Also, what about boring the engine to make it bigger capacity. This friend (he's a BMW mechanic) said you can bore it out to about 3.6L.

But why would you choose turbo over supercharger? And being a SMG gear box, how would turbo lag affect the transmission management system? Probably some fancy tinkering involved (launch control!!!).


I never heard of titanium pistons, but I don't see why they would not work since they are lightweight and can whistand high temps.

I'm not sure how strong the internals are in the M3 engine, so I'm not sure if you would need new ones or not.

Increasing displacement is always a good thing since it will give you more power and better powerband so boring it to 3.6 can only help. It might be expensive though.

There are several reasons I choose a turbo over a superchanger. It has no parasitic loss, its more thermodinamically efficient, you can change the boost anytime you want(you can get race fuel anytime you want and up the boost in a sec), you can even set the boost differently from gear to gear. Turbos are also load dependent and not RPM dependent like supers.

Turbo lag will be virtually nill with a proper turbo, if you are constantly at full load as under racing conditions it will stay spooled even at low RPM so its harder to be below the powerband.


About the SMG, if you are in manual mode i will not matter since you are choosing when to change the gears. In auto mode it might not match perfectly the new powerband but you don't usually race in auto mode plus I bet you can chip it to change the shift points to better match.

Well that sounds logical. Although I live in Queesland, the so called sunshine state of Australia and it gets very hot. How would that impact the decision to go turbo.

The tempting thing about supercharging is G-power has a kit already. It's tried and tested so I don't have to search in the dark with regards to what is the "RIGHT" turbo.

Another friend suggested if I'm going to increase the capacity, I may as well have the block remade in titanium. And then the internals will be able to handle anything if I have the custom titanium pistons to go with it.

Titanium isn't used in pistons, not in blocks either (and actually you don't want it there). Furthermore it seems that you don't know much what you are talking about. To remake a block isn't easy, and especially don't cheap, do you have a few hundred k to play around with?

Pistons are all about high stiffness, low weight and good heat transfer. One common material that is used in forged racing pistons is from WW2, the material is known as Rolls Royce 58 or 2618A. The currently best piston material availible is aluminum-beryllium, sadly it's very expensive, difficult to work with and toxic. The only coatings used are used for decreased friction and increased strength in the ring land. No more than 2 rings per piston will be needed if the cylinderwalls are stiff (note that when the bore is increase, the walls will be weaker and might deflect during load).

What usually needs to be replaced/modified for a higher power output is:
- pistons
- piston rings
- connecting rods
- head and main bolts
- head gasket
- bearings

Furthermore I can recommend that the coolant system is modified. For really high power outputs thick cylinder liners of iron/steel should be installed, preferbly Nikasil coated. The oil system must be modified, for high powers a dry sump system is recommended.

Then it's basically up to the cylinder head on how much power you can get, and the more power the narrower will the powerband be, the engine will also be more difficult to drive. How much the head must be modified depends how much power you want from the engine.
When using a turbocharger you can make power by boost and therefore the head will not need to be that modified.

If you have done large modifications on the engine an aftermarket engine management system is recommended, they usually cost between $3000 and $100,000 for a complete system.

Then the transmission must be modified also, at least a better clutch will be needed. To get the electronics to work together can also be a difficult task, at least if an aftermarket system is used.

When buidling BMW engines with high power outputs usually it's based on the older cars like this one:
http://www.m3turbo.nu/

The old 3.6 and 3.8 litre M5 engines also work very well with turbocharging, and the original engine is very strong so it need to be modified that much for high power outputs.