How much boost on standard M52 B28 compression

[MarkT]

Prob one for Gunni or Geoffbob. Just wandering how much boost could be ran on standard compression. I guess it varies between turbos but just a ball park figure? More interested in how far the horsepower can be taken to on a stock engine.

I'm currently in the middle of an M52 build and am going to keep it higher compresion initially for cost purposes and also from a drivability point of view. I'm not chasing silly power, just enough for track use.

[Gunni]

Steel or Aluminium?

10.2:1 compression ratio will allow quite the level of power if the backpressure is kept low and you swap the headbolts out for studs.

Also another factor is the fuel you plan on running.

I´d say 350hp on stock compression shouldn´t be a real problem if you run a generous back end turbine and 99octane fuel.

MLS gasket will put that up to 500-550hp.

[MarkT]

Alloy block with steel liners mate.. The turbo I'll be using will have a 10.5cm outlet on the hot side and will be capable of running about 2 bar.

350 ish is what i'm looking at power wise, I really think I don't need any more power than that for the track and I'm not overly fussed about 1/4 miling. Car wouldn't be set up for it anyway.

ARP the only people to use for head studs? Also, where abouts will the stock injectors run out?

Thanks

Mark

[E30BeemerLad]

You're a brave man changing the head bolts on an M52

[MarkT]

Well, if they get stripped then it'll be M50B28 time.. Or V8

[Geoff]

MLS gasket will put that up to 500-550hp.

Excuse my ignorance, whats an MLS gasket?

[MarkT]

Multi layer steel. Generally made by cometic mate.

[Geoff]

Cheers Mark... i was thinking multi layered something or other...

[Gunni]

Alloy block with steel liners mate.. The turbo I'll be using will have a 10.5cm outlet on the hot side and will be capable of running about 2 bar.

350 ish is what i'm looking at power wise, I really think I don't need any more power than that for the track and I'm not overly fussed about 1/4 miling. Car wouldn't be set up for it anyway.

ARP the only people to use for head studs? Also, where abouts will the stock injectors run out?

Thanks

Mark

What exactly is 10.5cm?
And 2bar is not a measurement of anything but pressure, it doesn´t mean any amount flow, which is the important bit.

You´ll run the injectors out rather fast. I calculated the 328i injectors at 5bar pressure to reach about 300hp.

S50 ones at 5bar will do more then 350hp.

[bss325i]

You're a brave man changing the head bolts on an M52

It will be fine if its not been cooked.

It only becomes a problem when the engine gets that hot that it weakens the threads.

[MarkT]

What exactly is 10.5cm?
And 2bar is not a measurement of anything but pressure, it doesn´t mean any amount flow, which is the important bit.

You´ll run the injectors out rather fast. I calculated the 328i injectors at 5bar pressure to reach about 300hp.

S50 ones at 5bar will do more then 350hp.

Exducer I think, I get the thing your saying about pressure, it's down to how well the head flows, volumetric efficiency etc?

I've got som 55lb injectors of one of the blokes off of here.

If i'm going to the hastle of doing all the head bolts, I might as well lift the head off and change the gasket too.

[MarkT]

You're a brave man changing the head bolts on an M52

It will be fine if its not been cooked.

It only becomes a problem when the engine gets that hot that it weakens the threads.

Engine shoud be fine, was a replacement due to nikasil liner faileur on the previous.

[jaistanley]

The difficulty with changing head bolts on aluminium blocks comes from when you are re-tightening.. With studs you insert them before applying torque (which due to the shape of the cut thread applies torque and tension to the bolt). On a stud you are only applying tension to the block side so therefore less likely to strip the thread in the block..

Hope that makes sense, it's early!

Jai

[Brianmoooore]

With studs you insert them before applying torque (which due to the shape of the cut thread applies torque and tension to the bolt). On a stud you are only applying tension to the block side so therefore less likely to strip the thread in the block..

And a stud can be screwed right to the bottom of the bolt hole, utilising every bit of the thread in the aluminium.
So why don't BMW offer studs as replacements on these engines?

[Simon13]

money i expect, heli coils the other option

[tomson]

heli coils the other option

Gets expensive though at £25 a thread!

[DanThe]

heli coils the other option

Gets expensive though at £25 a thread!

You are thinking of thread inserts Tom, best price I have had is £6 odd each and you can only buy them in packets of 20.

Helicoils are pence, a packet of 20 would be about £5

[tomson]

Nope, I pulled a thread in an S38 I rebuilt recently and had to get an engine shop to helicoil it for me, cost about £25 Dan There are 14 holes on all BMW 6 pots!

Edit - just reread your post Dan, the engine shop called it a helicoil, I dont know though!

[DanThe]

Ahh they charged you £25, sounds about right, but if you were doing all 14 you wouldnt pay someone to do it

[tomson]

Too right, they did try telling me I should get them all done, I had none of it!

Got a link to these bits Dan, I didnt realise it was something that can be done DIY?

[DanThe]

Helicoils are easy, you just need a special tap, best to fit them with thread lock and leave it to dry before screwing the bolt in.