Supercharging a high mileage M3

[M400DPC]

Im looking to buy an E46 M3 with a view to supercharging it. The car Im looking at buying currently has all the track gubbins APs, suspension, exhausts, manifolds, cage etc... It's mileage is currently 90k (on the original engine) and has spent the last 30k miles of its life as a track car in the ownership of the previous 2 owners. Most of the track time has been Nurburgring and Spa. Thus, the latter 3rd of its life has definitely not been easy...

My question is what steps would I need to take to avoid the engine detonating when supercharged? Can I simply forge the internals of the existing 90k engine i.e. is it a simple case of getting forged pistons, rods, bearings etc plus machining the block and the heads? Will the engine have seen too much wear for this? Will it need a complete rebuild?

As for costs, I know I will be in for £7k as a base cost for the supercharger alone. Anyone know what rough costs for forging and/or rebuilding?

Cheers all

[Kev T360]

Sounds good! I do know there is a supercharged 330i in the readers cars somewhere, that didn't get 'charged till 150k miles. I'm aware this is a different engine, but it shows that the BMW 6cly are still strong in old age.

[k-ink]

That is a chunk of change to spend if you rebuild it as well. Would an LS conversion be much different?

[vrooom]

BMW used high mileage bmw 2002 engine block, and left it outside for everyone to piss on, then cleaned up/machined for F1.. and turned the boost to 1500hp for F1 races... im sure your 90k block is fine.

[rallycross]

its worth discussing your plans with these guys before sinking £7k into this:

http://www.technosport.co.uk/contact.html

[MattOz]

Im sure it would be fine, but I'd change the head gasket as a precaution. The rest of the lump should be good to go.

[davepoth]

M400DPC said:

My question is what steps would I need to take to avoid the engine detonating when supercharged? Can I simply forge the internals of the existing 90k engine i.e. is it a simple case of getting forged pistons, rods, bearings etc plus machining the block and the heads? Will the engine have seen too much wear for this? Will it need a complete rebuild?

Um...that's almost a complete rebuild anyway. The only major thing left is the crank.

[HD Adam]

Forged or stronger engine parts will not have anything to do with detonation.

That will be down to compression ratio, boost, intake air heat, fuel type, timing and the general tune.

The forged bits will only make the engine stronger and allow to to make more power before it eats itself. (up to a point)

Not a BMW engine but my Ford V8 with too much power for the chocolate internals.

[TheAngryDog]

rallycross said:

its worth discussing your plans with these guys before sinking £7k into this:

http://www.technosport.co.uk/contact.html

I bet they aren't cheap! £70 + VAT an hour for Labour!

[paulrussell]

I'd do a compression test just to see how healthy the engine is. If the compression test shows the engine is in good condition, then I wouldn't worry about rebuilding the engine.

[M400DPC]

k-ink said:

That is a chunk of change to spend if you rebuild it as well. Would an LS conversion be much different?

True but Id want to keep it purist. If I had the money Id have a supercharged CSL sat next to an M5 V10 CSL....

Still haven't ruled out the v10 conversion but it's getting hold of someone to do it for sensible money

[aka_kerrly]

HD Adam said:

Forged or stronger engine parts will not have anything to do with detonation.

That will be down to compression ratio, boost, intake air heat, fuel type, timing and the general tune.

Very much this, the amount of boost will determine how thorough you need to build the engine. Typical supercharger conversions run on 6-8psi which many factory engines can handle without too many issues.

[rallycross]

TheAngryDog said:

rallycross said:

its worth discussing your plans with these guys before sinking £7k into this:

http://www.technosport.co.uk/contact.html

I bet they aren't cheap! £70 + VAT an hour for Labour!

The point is they know a thing or two about building high powered M3 engines (race) ask first before spending money elsewhere.
And £70 + vat p/h in London for a specialist with the all the BMW tec' they have is actually quite cheap!

[Silent1]

vrooom said:

BMW used high mileage bmw 2002 engine block, and left it outside for everyone to piss on, then cleaned up/machined for F1.. and turned the boost to 1500hp for F1 races... im sure your 90k block is fine.

No they didn't, it's a myth.

[750turbo]

rallycross said:

TheAngryDog said:

rallycross said:

its worth discussing your plans with these guys before sinking £7k into this:

http://www.technosport.co.uk/contact.html

I bet they aren't cheap! £70 + VAT an hour for Labour!

The point is they know a thing or two about building high powered M3 engines (race) ask first before spending money elsewhere.
And £70 + vat p/h in London for a specialist with the all the BMW tec' they have is actually quite cheap!

Have to agree with this totally.

OP, are you seriously thinking about this, or just dreaming like we all do at times?

Seems a good way to turn a lot of cash into a little cash possibly?

[M400DPC]

750turbo said:

q

OP, are you seriously thinking about this, or just dreaming like we all do at times?

Seems a good way to turn a lot of cash into a little cash possibly?

Yes very serious. Agreed, it will be cash spent never to be seen again but these things are easy to justify when you're a petrol head

[750turbo]

M400DPC said:

Yes very serious. Agreed, it will be cash spent never to be seen again but these things are easy to justify when you're a petrol head

Good luck and let us know how the project develops.

Having owned one supercharged car, 28MPG at 70MPH was enough for me (Toyota Corolla Compressor 1.8, and there is no way that they develop the supposed 217BHP IMO)

[gaz1234]

There is someone on here with one

[mike-r]

May be of interest:

http://forums.m3cutters.co.uk/showthread.php?t=920...