can a 45amg BO3 turbo (same type as n55) be fitted to A n55

[bmw335ie90]

Hi i have a a45 amg turbo and oil lines that did about 20000kms on the car since new. I bought it from a guy that went for a bigger turbo.

My question is can i make the a45 amg BO3 turbo fit on a n55 car?
(i know it might not line up right)

I know the n55 also uses a BO3 turbo. But its internals are not even close to the a45 amg bo3 turbo.

Stock the n55 B03 makes +- 10 psi 225kw, 400nm with a 3l l6

Stock the a45 amg makes 26 psi 260kw, 450nm with a 2l 4 cylinder.

The a45 amg makes 35 more kw and 50nm more then the n55 with a 2L vs a 3L. So the magic must be in the turbo :=):

If its "impossible" to make it fit can i use the a45 amg internals inside a n55 b03 turbo? :smilebounce:

 

[corp]

The responses on this should be interesting.


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[Ddoooooon]

Interested to see if this will work and if it does what will it put out mgwaiting:

 

[MikeR]

it should work - but I dont think the turbo itself will make the extra power straight off, a lot will have to do with the management system.

 

[Danny2]

Speak to Gaby from Fastec, sure he will have the best answers

 

[corp]

It is mentioned that the turbo found on the 45AMG can’t feed enough air into the 3l N55. Others said it has better internals only but should work fine.

I don’t know if there is a difference with the turbos on the E90 generation vs those in the F20/F30 generation of motors.

I do hope we find more info on this.


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[bmw335ie90]

"It is mentioned that the turbo found on the 45AMG can’t feed enough air into the 3l N55."

How can this be if the n55 comes from bmw with a B03 turbo? same as the one on the a45 amg? Only difference is internals here... and they seem to make a big difference. Wish i can get some more info on this. There must be someone that has had this idea...:tiptoe:

 

[FerdiBotha]

"It is mentioned that the turbo found on the 45AMG can’t feed enough air into the 3l N55."

How can this be if the n55 comes from bmw with a B03 turbo? same as the one on the a45 amg? Only difference is internals here... and they seem to make a big difference. Wish i can get some more info on this. There must be someone that has had this idea...:tiptoe:

The internals feed the air, so if the internals differ the amount of air being fed will also differ..

 

[osiris]

Hmmmmm the difference in power is due to the PSI differences.

The N55 is only pushing 10psi but is capable of allot more than that with software.

The A45AMG is pushing 26 psi which is a mammoth amount of boost!

If your N55 was pushing 26 pounds of boost you would be making serious power!!! I am not sure what the stock N55 turbo can push but its a hell of allot more than 10psi...

Surely this is all due to waste gate duty cycle being effected by ECU which will control the amount of boost being generated?

 

[Girevik77]

I'm just guessing here, but from first principles it would stand to reason that the B03 on the A45 would perhaps have more blades (both on the turbine and the compressor) than the one on the N55. This would aid spool up and increase the ability to deliver high pressure boost, whereas fewer blades on the N55 would lend itself to a higher flow application ie. delivering more air to a 3L 6 in comparison to a 2L 4.
I could be miles off though, because there are many other ways to accomplish this, it can be achieved with larger/smaller tip clearances as well.

It would be very interesting to compare the cores of the two units and see whats what.

In an attempt to answer the OP I will say the following, at first glance I would think that it would not be possible to just swap the turbos for the following reason:
A quick calculation: Engine displaces its entire volume for every 360 degrees of crank rotation.
N55 - 3L x 6000RPM = 18000L of air per minute
A45 - 2L x 6000RPM = 12000L of air per minute

It's a very basic calculation and it's not completely accurate, total volume will change when taking into consideration charge air temp and adiabatic compression, but the theory is there. Bigger engine needs more air at the same engine speeds.

But when you take into consideration that air is compressible, unlike water and oil, it can be said that to compress a similar volume to 26Psi vs 10Psi you would need to force a lot more air into the same space. Like forcing 18000L of air into a space originally meant for 12000L. For this reason I think it might actually be possible.

Like I said I'm not sure at all but it would be very very interesting to actually compare the two.

 

[Veteran]

As previously stated. Gabby of Fastec is probably the best person to speak to. He has built many a turbo for the n55 engine. He also knows the pure turbos and what else is used on the n55.
At worst, he would inspect the A45amg turbo and give you a genuine feedback of what it can and cannot do on a n55.
Fwiw, Fastec puts a bigger compressor wheel on the std turbo which ads much needed top rpm boost.
Standard turbos run out of puff at higher rpms.

 

[bmw335ie90]

As previously stated. Gabby of Fastec is probably the best person to speak to. He has built many a turbo for the n55 engine. He also knows the pure turbos and what else is used on the n55.
At worst, he would inspect the A45amg turbo and give you a genuine feedback of what it can and cannot do on a n55.
Fwiw, Fastec puts a bigger compressor wheel on the std turbo which ads much needed top rpm boost.
Standard turbos run out of puff at higher rpms.

I spoke to Gabby from fastec today and he was very helpful and smart when it came to these questions.

He said yes it is possible! But you will have to fabricate a other manifold and relocate a few small things. He said hardware (downpipe) ect will be needed and custom tuning will be needed.
The a45 amg turbo runs 29psi with a remap. Thats some hardddd boost!!

 

[corp]

So the question now is, who is going to do it first?

I will wait and see what the results for if I ever decide to mod that much.


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[ANiMOSiTY]

The only way to know the answer is by turbo data sheets and comparing ultimate output (flow, or volume) at a given level of boost. Then calculating that flow vs the engine's displacement and volumetric efficiency.

Gaby will probably know this data.

Engine displaces its entire volume for every 360 degrees of crank rotation.

No, a 4-stroke engine needs two complete revolutions to ingest it's displacement of air or combustible mixture, assuming 100% volumetric efficiency.
So it would be 720 degrees of revolution for a 100% efficient N/A engine.

For forced induction, volumetric efficiency is generally a fair amount greater than 100%, due to forcing more air into the cylinders.
So, more boost also means more air which increases volumetric efficiency, but only to a point.
There's a tradeoff of heat, boost pressure, turbo efficiency at low vs high RPM, turbo ARs etc.

So for your example, for a naturally aspirated engine with a volumetric efficiency of 100%, each flows half of your numbers.
3L x 6000RPM = 9000L of air per minute
2L x 6000RPM = 6000L of air per minute

Add turbos, which are at different boost levels to each other, and they could be each flowing enough to get each engine to the same amount of airflow as the other (hypothetically), meaning both turbos could be flowing the same amount of air per minute at a given boost level.

i.e.
N/A
3L x 6000RPM = 9000L of air per minute (3 x (6000/2) x 1.0) (the 1.0 for 1 bar of atmospheric air pressure at sea level, again assuming 100% efficiency)
2L x 6000RPM = 6000L of air per minute

Assuming 1.5 bar of absolute pressure is enough to get both engines to 150% volumetric efficiency:

3L TURBO @ 0.5 bar x 6000RPM
(3 x (6000/2) x 1.5) (the 1.5 for 1.5 bar absolute manifold pressure -> atmospheric + turbo)
= 13 500 l/minute

2L TURBO @ 0.5 bar x 6000RPM
(2 x (6000/2) x 1.5) (the 1.5 for 1.5 bar absolute manifold pressure -> atmospheric + turbo)
= 9000 l/minute

So, still the figures don't match the difference between the A45 and N55.
A45 was originally 265 kW (I know it was increased in 2016 I think)
N55 is 225ish, mostly?

So let's tweak the numbers so that the 2.0L T flows 17% more than the 3.0L T (based on an approx. 17% power difference?)

3L TURBO @ 0.5 bar x 6000RPM
(3 x (6000/2) x 1.5) (the 1.5 for 1.5 bar absolute manifold pressure -> atmospheric + turbo)
= 13 500 l/minute

2L TURBO @ 0.755 bar x 6000RPM
(2 x (6000/2) x 1.755) (the 1.5 for 1.5 bar absolute manifold pressure -> atmospheric + turbo)
= 10 530 l/minute

So, maybe it flows less and the A45 has a higher volumetric efficiency than the N55, or maybe they run the engine richer to make more power etc?
Volumetric efficiency has an effect on power, but it's only one factor out of a lot of things (removal of heat, mixture, engine inertia etc etc).

 

[Girevik77]

No, a 4-stroke engine needs two complete revolutions to ingest it's displacement of air or combustible mixture, assuming 100% volumetric efficiency.
So it would be 720 degrees of revolution for a 100% efficient N/A engine.

:hammerhead: Silly me I overlooked that.

So for your example, for a naturally aspirated engine with a volumetric efficiency of 100%, each flows half of your numbers.
3L x 6000RPM = 9000L of air per minute
2L x 6000RPM = 6000L of air per minute

Agreed

Add turbos, which are at different boost levels to each other, and they could be each flowing enough to get each engine to the same amount of airflow as the other (hypothetically), meaning both turbos could be flowing the same amount of air per minute at a given boost level.

This is what I was thinking

So let's tweak the numbers so that the 2.0L T flows 17% more than the 3.0L T (based on an approx. 17% power difference?)

If we tweak your numbers for actual boost pressure

3L TURBO @ 0.68 bar x 6000RPM
(3 x (6000/2) x 1.68) (the 1.68 for 1.68 bar absolute manifold pressure -> atmospheric + turbo)
= 15 120 l/minute

2L TURBO @ 1.8 bar x 6000RPM
(2 x (6000/2) x 2.8) (the 2.8 for 2.8 bar absolute manifold pressure -> atmospheric + turbo)
= 16800 l/minute

All that being said your calculations and my assumptions are very vague and based on perfect isothermal compression (no heat losses), whereas in the real world air compression is a polytropic process (losses due to thermodynamic efficiency and heat loss to atmosphere).
If we had raw data and really crunched the numbers I bet we would find that the B03 A45 flows slightly less due to mechanical and thermodynamic efficiencies and losses.

 

[akash]

Guys forgive me.......

Im gonna go slightly off track on the turbo fitment.

With the A45 pushing out so much boost, what is their fueling system like?

On an N54 and N55, as soon as you start to push higher boost level your stock pumps start to struggle.

It would be nice to know what fuel config they use to support those boost levels.

 

[ANiMOSiTY]

No, a 4-stroke engine needs two complete revolutions to ingest it's displacement of air or combustible mixture, assuming 100% volumetric efficiency.
So it would be 720 degrees of revolution for a 100% efficient N/A engine.

:hammerhead: Silly me I overlooked that.

So for your example, for a naturally aspirated engine with a volumetric efficiency of 100%, each flows half of your numbers.
3L x 6000RPM = 9000L of air per minute
2L x 6000RPM = 6000L of air per minute

Agreed

Add turbos, which are at different boost levels to each other, and they could be each flowing enough to get each engine to the same amount of airflow as the other (hypothetically), meaning both turbos could be flowing the same amount of air per minute at a given boost level.

This is what I was thinking

So let's tweak the numbers so that the 2.0L T flows 17% more than the 3.0L T (based on an approx. 17% power difference?)

If we tweak your numbers for actual boost pressure

3L TURBO @ 0.68 bar x 6000RPM
(3 x (6000/2) x 1.68) (the 1.68 for 1.68 bar absolute manifold pressure -> atmospheric + turbo)
= 15 120 l/minute

2L TURBO @ 1.8 bar x 6000RPM
(2 x (6000/2) x 2.8) (the 2.8 for 2.8 bar absolute manifold pressure -> atmospheric + turbo)
= 16800 l/minute

All that being said your calculations and my assumptions are very vague and based on perfect isothermal compression (no heat losses), whereas in the real world air compression is a polytropic process (losses due to thermodynamic efficiency and heat loss to atmosphere).
If we had raw data and really crunched the numbers I bet we would find that the B03 A45 flows slightly less due to mechanical and thermodynamic efficiencies and losses.

Shyte, didn't realise how much that A45 boosts.
But exactly, our numbers are completely hypothetical. We're at altitude as well, so that dramatically changes things too.
But our point is the same, you need the turbo data to know.

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---

Guys forgive me.......

Im gonna go slightly off track on the turbo fitment.

With the A45 pushing out so much boost, what is their fueling system like?

On an N54 and N55, as soon as you start to push higher boost level your stock pumps start to struggle.

It would be nice to know what fuel config they use to support those boost levels.

It's the same argument again.
The amount of fuel flow to 4 cylinders vs 6, vs the delivery pressure etc

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[bmw335ie90]

The only way to know the answer is by turbo data sheets and comparing ultimate output (flow, or volume) at a given level of boost. Then calculating that flow vs the engine's displacement and volumetric efficiency.

Gaby will probably know this data.

Engine displaces its entire volume for every 360 degrees of crank rotation.

No, a 4-stroke engine needs two complete revolutions to ingest it's displacement of air or combustible mixture, assuming 100% volumetric efficiency.
So it would be 720 degrees of revolution for a 100% efficient N/A engine.

For forced induction, volumetric efficiency is generally a fair amount greater than 100%, due to forcing more air into the cylinders.
So, more boost also means more air which increases volumetric efficiency, but only to a point.
There's a tradeoff of heat, boost pressure, turbo efficiency at low vs high RPM, turbo ARs etc.

So for your example, for a naturally aspirated engine with a volumetric efficiency of 100%, each flows half of your numbers.
3L x 6000RPM = 9000L of air per minute
2L x 6000RPM = 6000L of air per minute

Add turbos, which are at different boost levels to each other, and they could be each flowing enough to get each engine to the same amount of airflow as the other (hypothetically), meaning both turbos could be flowing the same amount of air per minute at a given boost level.

i.e.
N/A
3L x 6000RPM = 9000L of air per minute (3 x (6000/2) x 1.0) (the 1.0 for 1 bar of atmospheric air pressure at sea level, again assuming 100% efficiency)
2L x 6000RPM = 6000L of air per minute

Assuming 1.5 bar of absolute pressure is enough to get both engines to 150% volumetric efficiency:

3L TURBO @ 0.5 bar x 6000RPM
(3 x (6000/2) x 1.5) (the 1.5 for 1.5 bar absolute manifold pressure -> atmospheric + turbo)
= 13 500 l/minute

2L TURBO @ 0.5 bar x 6000RPM
(2 x (6000/2) x 1.5) (the 1.5 for 1.5 bar absolute manifold pressure -> atmospheric + turbo)
= 9000 l/minute

So, still the figures don't match the difference between the A45 and N55.
A45 was originally 265 kW (I know it was increased in 2016 I think)
N55 is 225ish, mostly?

So let's tweak the numbers so that the 2.0L T flows 17% more than the 3.0L T (based on an approx. 17% power difference?)

3L TURBO @ 0.5 bar x 6000RPM
(3 x (6000/2) x 1.5) (the 1.5 for 1.5 bar absolute manifold pressure -> atmospheric + turbo)
= 13 500 l/minute

2L TURBO @ 0.755 bar x 6000RPM
(2 x (6000/2) x 1.755) (the 1.5 for 1.5 bar absolute manifold pressure -> atmospheric + turbo)
= 10 530 l/minute

So, maybe it flows less and the A45 has a higher volumetric efficiency than the N55, or maybe they run the engine richer to make more power etc?
Volumetric efficiency has an effect on power, but it's only one factor out of a lot of things (removal of heat, mixture, engine inertia etc etc).

I am with you on the CFM ratings that count the most at the end of the day. But i am struggling to find that info on either of the turbos. Does anyone know the n55 bo3 cfm rating?

I might be wrong (probably am just thinking logical ) but in my mind bo3 vs bo3 turbo should allow the same amount of air in the housing. The internal parts of the turbo should influence the pressure of the flow...