[e.n335]

Hi,

Found information for the Alpina B3, which uses the same turbos we have:

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(from Alpina Press Release)

In ALPINA’s more than 40-year history of manufacturing automobiles, turbo-charged engines have consistently set enduring accents. Launched in 1989, the BMW ALPINA B10 Bi-Turbo is just one example of the cult status some of these automobiles achieved. In fact, ALPINA’s turbo-charging history began in 1978, based on the 5 Series and 6 Series of the day (E12 & E28 and E24). The new BMW ALPINA B3 Bi-Turbo continues this tradition for the first time on the basis of the BMW 3 Series with its world premiere at the 2007 Geneva Salon d’Automobile

The heart of the B3 Bi-Turbo offers 265 kW (360 hp) at 5,500 - 6,000 revolutions per minute, as well as maximum torque of 500 Nm from 3,800 - 5,000 rpm. The B3 Bi-Turbo’s engine has a sporty engine’s willingness to rev to 7,000 rpm. Equally as present but usually reserved for diesel engines, there is vigorous torque from 1,500 rpm onwards. The result: a powerband broader than ever before experienced, guaranteeing both sporty and bullish driving dynamics

Technically, this is all made possible due to the exceptional BMW base engine with injectors centrally located over the pistons – the state-of-the-art in direct injection technology. For more than a year, ALPINA engineers researched, developed and tested, both on the engine test bench and on the road. Ever refining the ALPINA engine map to leverage all the advantages offered by modern direct injection, the potential inherent in the BMW foundation was maximised. The use of extremely durable MAHLE pistons allows for a maximum boost of 1.1 bar with a 9.4:1 compression ratio. The result, peak specific values of 89 kW (121 hp) per litre and a maximum average pressure of 21 bar

The allure of the new BMW ALPINA B3 Bi-Turbo is found in its V8 like performance, but with the advantages of a much lighter and noticeably thriftier 3.0-litre straight-six, a six with an aluminium block and twin-turbo charging. The smooth-running nature inherent in this engine concept is even more prominent when the engine is charged

The BMW ALPINA B3 Bi-Turbo embodies pure driving enjoyment – whether cruising along or enjoying all 7,000 revs in each gear. The reason for the spontaneous responsiveness of the B3 Bi-Turbo is the ZF 6-speed sport automatic transmission with its very short shift sequences, which smoothly processes the power through the drivetrain without any uncomfortable interruption of forward momentum. The driver may also choose to shift manually at the wheel using SWITCH-TRONIC, which contributes in no small part to both the awe-inspiring performance numbers and the ability to save fuel in top gear. Frugality and driving excitement are therefore not contradictory in the B3 Bi-Turbo. Driven by high torque means using sixth gear on the Autobahn is more than sufficient in almost all situations

The engine’s kick surprises even those in the know: 0-100 km/h in 4,9 seconds and thrust-like acceleration that keeps pulling all the way up to a top speed of 285 km/h. Indulgence without remorse: in spite of its stellar performance, the new BMW ALPINA B3 Bi-Turbo achieves excellent fuel economy in relation to its competitors. One of the B3 Bi-Turbo’s features that literally stands out are the four exhaust tips, with their catalytic converters contributing significantly to the achieving of low Euro4 emissions standards

The intense driving experience and an immediate bonding with the B3 Bi-Turbo are markedly influenced by fine materials and superior ergonomics. The standard leather interior features comfortably-padded sport seats with excellent lateral support, making long journeys a joy. The ALPINA SWITCH-TRONIC steering wheel falls perfectly to hand and affords a clear view of the typical ALPINA blue instruments with their red pointers. As demanded by any enthusiastic driver, the provision of essential information in the form of the analogue oil temperature gauge located below the rev counter means the B3 Bi-Turbo can be pushed to its limits, once the minimum oil temperature of 50° C has been reached. Next to the analogue speedometer, the B3 Bi-Turbo also provides a digital speed read-out as well as average fuel economy and instantaneous fuel economy figures – thrifty driving also creates driving pleasure

Immediately noticeable is the B3 Bi-Turbo’s light-footed, extremely agile handling. The secret lies in an ideal 50/50 weight balance between front and rear axles in combination with a ALPINA’s neutral and supple suspension. Augmenting this agility are light-weight 18” ALPINA CLASSIC wheels shod with conventional MICHELIN tyres, 225/40 ZR18 front and 255/35 ZR18 rear, with a conscious choice having been made not to use heavy Run-Flat tyres. 19” wheels offer an even higher level of potential lateral acceleration – in either DYNAMIC or CLASSIC design

ALPINA’s newest creation reduces aerodynamic lift, especially approaching top speed. The greatest contributors are the optimised front and rear aerodynamics, helping guarantee true driving safety, not just creating a feeling of safety

In quite exclusive fashion, we’ll complete but a few hundred B3 Bi-Turbos in Buchloe per annum for automotive connoisseurs. As tradition holds, each automobile will be fitted with an ALPINA plaque identifying its unique production number

The new BMW ALPINA B3 Bi-Turbo – revel in its unique driving experience infused with impressive grace, power and thrift.

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1.1 bar are 15.95 psi.

- Eugen

[JoeyFiasco]

so basically, we could in theory push past the 15 psi mark safely?

[ironic]

Originally Posted by JoeyFiasco

so basically, we could in theory push past the 15 psi mark safely?

it works out to be 15.95 psi

[JoeyFiasco]

Originally Posted by ironic

it works out to be 15.95 psi

I realize that, but the stigma was to stay below 15psi due to engine/turbo reliability and durability.

[e.n335]

IMO the maximum boost of 1.1 bar is comparable to the maximum boost 0.8 bar of the 335i, only applied on very hot days or at high altitude. So not exceeding 15 psi under normal conditions on the piggies might be a good idea.

However, good to know that the turbos are tested and can sustain nearly 16 psi.

[YvesD]

Originally Posted by e.n335

IMO the maximum boost of 1.1 bar is comparable to the maximum boost 0.8 bar of the 335i, only applied on very hot days or at high altitude. So not exceeding 15 psi under normal conditions on the piggies might be a good idea.

However, good to know that the turbos are tested and can sustain nearly 16 psi.

Yes, but more crucially perhaps they felt the need to upgrade the pistons.

Any technical insight on this ?

Yves

[Bubbles]

Great read, thank you Eugene.

[JOe335i]

GOOD FIND!

[scheherazade]

Originally Posted by YvesD

Yes, but more crucially perhaps they felt the need to upgrade the pistons.

Any technical insight on this ?

Yves

If I remember right, the compression ratio they mention is lower than stock.
Which probably means they changed pistons just to lower compression.
They would lower compression because it's how you keep the F/A mixture from igniting too early if it's already under boost pressure.
You'll find that most 'little engine big turbo' cars have pretty weak compression.

-scheherazade

[stressdoc]

The Mahle pistons and lower CR, and some other software tweaks, were in large part Alpina's response to the overheating issues for cyl 5 & 6.

[oddjob2021]

sweet! great find man, I wonder if active knew? I'm JUST under the mark, (15.7 psi)

[Tobias1980]

FWIW, I recently talked to a ECU tuner that is developing a flash for X35i - they are in doing small adjustment with lag issue etc right now and it will be commercially available soon. He told me that his "stage 0" (no other mods) will have maximum boost of 14,5 PSI due to extreme heat build up in the turbos during heavy acceleration. According to him more heat (by boost) could potentially damage the turbos. His opinion is that the car should be able to handle all potential stress that a stock car is built to handle. He was specifically pointing at extreme acceleration like 0-160 MPH and full throttle for long time at top speed etc.

The first hardware that should be updated according him was better flowing downpipes that would decrease heat build up in the turbos and hence allow for more boost.

He also told me that he did not find the intercooler to be a weak point right now according to his measurements- but it will certanly be the next hardware upgrade after downpipes.

[vegasspeed]

I think the next logical step is replacing the turbo setup and building a stronger motor as well. That would be a pretty kick ass project.

[5soko]

doesnt a stock engine stop making power at about 15psi? dont DP,intake come in after that to make more usable power with more PSI?

i think on a 14psi tune setup well, can be reliable.

[Lane]

Originally Posted by e.n335

Hi,

The use of extremely durable MAHLE pistons allows for a maximum boost of 1.1 bar with a 9.4:1 compression ratio. The result, peak specific values of 89 kW (121 hp) per litre and a maximum average pressure of 21 bar[/B]

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1.1 bar are 15.95 psi.

- Eugen

Eugen, this is not quite the way to interpret the text. The total stress is a function of boost AND compression ratio. By lowering the compression ratio using low CR pistons, they are able to increase the boost resulting in higher average total pressure.

By "allowing" they can mean that the boost can safely be increased. Note that the total pressure is not as high with the low CR pistons as with higher CR stock pistons at the given 1.1 bar boost level. I.e. with stock pistons and 1.1 bar boost, the total pressure (boost & CR) is more than what Alpine has as their total pressure.

Or they can mean that the pistons "allow" to increase the total pressure. (Again boost + CR).

All this has nothing to do with turbo longevity, since that has more to do with the turbo revolutions. Turbo revolutions are not a direct function of CR. Turbo longevity has to do with how much boost is applied at high engine speeds. High boost at high engine speeds may cause overspinning of turbo and reduce the life of turbos.

To summarize, there is nothing that would suggest that the total pressure would require forged pistons. The total pressure is not too high for the stock cast pistons. This is based on the fact that there are many tuners offering more power (which implies more total pressure in the cylinders) than Alpina, and still using the stock pistons.

In fact the forged pistons do not even stand much more pressure than cast pistons. Forged pistons typically stand more revs and allow more revs due to being lighter.

And finally, Alpina is not referring to the longevity of turbos in this text. Obviously they believe that the longevity of turbos is just fine with the 1.1 bars i.e. 15.95 psi.

[HighVoltage]

If you can effectively eliminate detonotation theres really no point to running forged.

Originally Posted by Lane

Forged pistons typically stand more revs and allow more revs due to being lighter.

Oops..

[O-cha]

Maximum boost has nothing to do with turbo reliability.

[Robmaster]

yes, 15psi, but dont forget, they have a 9.4:1 compression ratio!!!!

[O-cha]

Originally Posted by Robmaster

yes, 15psi, but dont forget, they have a 9.4:1 compression ratio!!!!

CR doesn't effect turbo reliability either. They are unrelated. Maximum boost has to do with engine reliability, CR has to do with knock chance as well as peak and dynamic cylinder pressures, again, about engine reliability.

[Robmaster]

so why does Alpina change the pistons if there would be no problem to run 15psi with the normal pistons?

[TMR]

actualy, if we are running 14psi to the manifold..... thats only 7 psi per turbo.

[Strax]

I think Alpina is designing the engine with the "european" driving style in mind. In Europe and in Germany it is not unsual for the engine to see sustained speeds of 240+ km/h, which is extremely unusual in the US.

It is in this case that 15 psi for a few minutes could mean trouble for the engine and so the need for lower compression ratio.