F80 M3 / F82 M4 S55 Tuning

[solstice]

Originally Posted by Boss330

I don't know the exact PSI, but you can assume it's above 1,8bar (26PSI) since that is stock boost...

I added to my comment you quoted. I suspect it's not peak boost but less tapering.

[RoBiK]

Multiplying CR with the boost pressure is wrong.
What you want to do is to calculate the absolute pressure inside a cylinder.
Boost pressure is the relative pressure above atmospheric pressure. So if you want to calculate absolute pressure inside a cylinder (ignoring other factors like for example volumetric efficiency or that the pressure at the cylinder intake port is lower than the pressure generated by the turbo) you need to use absolute pressure - atmospheric pressure (that is not constant) plus the boost pressure. The result of this addition can than be multiplied by the CR to get a somewhat meaningful number.

Atmospheric pressure at sea level is around 14,7 psi.

[solstice]

Agree, Boost x CR is simplified and flawed but IMO still works reasonably well for comparison purposes and to get a rough idea without getting lost in complexity.

[Boss330]

Originally Posted by solstice

What is the psi with those tunes?
I suspect that gains are mainly made by less tapering and not by pushing peak bost. The question is, can the S55 stock turbos support less tapering?
A pure guess from me is, not much. Reasons being that minimum lag and high rpms are both M trademarks leading me to think that BMW selected small turbos and utilized most of their ability to pump air at high rpms already.

I do think they have left enough room for about a 5% or ~25hp power bump with the comp. pack. utilizing mainly peak boost ~4psi but this is just speculation.

Minimum lag is taken care of via the "anti-lag" system explained in a different thread that keeps the turbos spinning at 100.000rpm even when coasting (when in "M-modes"). So, not that critical to have small turbos. But just as you, I don't know any details of the turbos so they could be on the small side and not have a lot of room for more Power. But I find it unlikely that BMW has chosen turbos that operate at 95% of full capacity...

Let's take a different example:

Audi RS6 with the 4.0 V8 TFSI engine.
It has a 10.1:1 CR and max boost of 1.2 bar

An unthrottled intake system supplies the four-liter V8, which has a specific engine management system, with air; the Audi FSI direct injection metres the fuel. Switchable flaps in the intake ports mix the incoming air in a cylindrical motion to enhance charging and combustion. The directly injected and intensively swirled fuel cools the combustion chambers. This method enables the high compression ratio of 10.1:1.
Two turbochargers generate up to 1.2 bar of relative boost pressure.

http://www.ausmotive.com/downloads/A...t-July2013.pdf

MTM has developed several stages of tuning with the highest output being the 722hp version. Similar output to the Manhart and G-Power versions of the F10 M5.

http://www.mtm-online.de/en/Audi/RS6...FZID=RS6C7412q

I find it unlikely that BMW has left so little safety margins in the S55, when the S63 hasn't and other manufacturers also have high CR engines that can achieve a 25% boost in power. You really don want a turbo setup that runs at 100% in Competition Pack mode. That would very likely not be up to BMW quality standards and needed longevity of components (warranties etc).

If, BMW has built in so small margins, then I suspect that will allmost be a world first...

[BlackLight]

Originally Posted by solstice

...Show me a car/tune that continue to gain hp when exceeding +220 CR x psi on street gas and you'll change my view. The S55 is stock at 10.2 x 18 = 183...

The 18psi published for the S55 is what it is capable of in order to compensate for low pressure atmospheric conditions like at high altitude, or when the air is very hot and the density decreases. For sure it is not always running at this pressure, otherwise the torque curve would not have had such a pronounced flat plateau, created by the ECU artificially limiting the boost.

I am guessing the actual "normal condition" max psi on the stock S55 is going to be ~14 psi to make the 431 hp.

[solstice]

The anti-lag system operates on-off-on throttle it does not help from idle rpms. Here you benefit from small turbos to get on boost quickly. My guess is small turbos and that in a strive to keep as much as possible of the M high rpm character they use most of their potential to pump air at high rpms but your guess is probably as good as mine here.

[BPMSport]

There is going to be some power left on the table tuning wise with the S55 motor - but it's not going to be as much as we've seen from the N54 motors. The biggest battle the S55 will face is controlling temperature. With upgraded cooling, there is much more potential, but with the factory cooling system, there may issues keeping temperatures down on more aggressive software.

[Boss330]

Originally Posted by solstice

The anti-lag system operates on-off-on throttle it does not help from idle rpms. Here you you need small turbos to get on boost quickly. My guess is small turbos and that in a strive to keep as much as possible of the M high rpm character they use most of their potential to pump air at high rpms but your guess is probably as good as mine here.

My guess is also "small" turbos, just as on any other modern turbo engine. But with a bit more margin for safety and durability than what you assume, i.e. not running at 95-100% of maximum in stock tune...

Do we know everything about how the anti lag system works, and that it is only operative during those conditions?

But anyway, look at RS6 spec, F10 M5 spec and notice how soon they build pressure (and power) from idle. And both have been tuned to increase power by 25% on stock turbos. Let's say that the S55 relatively has slightly smaller turbos, should still be able to do a 20% increase. Which brings us to 515hp, or +85hp.

And a turbo also consists of both a compressor and turbine unit. Turbine unit can be small to aid spool up. But with a good wastegate it can bleed off excess exhaust at high rpm's to avoid backpressure and overspooling. The compressor unit needs to flow a decent amount of air, and since BMW has said that the S55 shall make it's 430hp also in low density, high altitude and high temp situations I suspect that the compressor unit is able to flow decent amounts of air. If you tune it to 520hp, sure it might not make that power on the hottest day in Death Valley or at Mount Everest altitudes (like the stock S55 shall at 430hp). But that's part of tuning. If you push the envelope to 95% at ideal conditions, you won't get the same power under less ideal conditions.

To me the turbine unit looks fairly small, but notice how the wastegate is positioned and the large diameter of the exhaust part that routes exhaust past the turbine. To me that indicates exactly what I said above. A small turbine to aid spool up, but a large exhaust bypass to exit exhaust outside the turbine at higher rpm's. The compressor unit on the other hand looks fairly big.

[Boss330]

Originally Posted by Mike Benvo

There is going to be some power left on the table tuning wise with the S55 motor - but it's not going to be as much as we've seen from the N54 motors. The biggest battle the S55 will face is controlling temperature. With upgraded cooling, there is much more potential, but with the factory cooling system, there may issues keeping temperatures down on more aggressive software.

Of course it will not be able to do the same doubling of power as the N54... The N54 was a engine at 50% of it's potential, the S55 is maybe at 70% (just random numbers, but the point is that obvioulsy a engine running at 0.5 bar boost has a much larger potential for tuning than a engine running at 1,25 bar... The latter engine is allready at a much higher state of tune, so leaves less room for tuning).

[basscadet]

Originally Posted by BlackLight

I am guessing the actual "normal condition" max psi on the stock S55 is going to be ~14 psi to make the 431 hp.

Maybe. But until we know the specifications of the turbos this is all just shooting-the-sh*t.

If a full-bolt-on 335i is capable of 450ish hp (or whatever, not sure of that #), and the limitations are not fuel-related, I do not see how the F8X is going to be able to do much more than that. The golden rule needs to be repeated more on this forum than it is: There is no replacement for displacement.

Now yes, this engine is more robust, can take more boost, has forged internals, etc but NONE of that matters if the small and quick-spooling turbos on this car just can't flow.

By the way, are we really happy with straight-line performance equal to a bolt-on, last-generation 3-series? We need to aim higher in our expectations.

[Boss330]

Originally Posted by basscadet

Maybe. But until we know the specifications of the turbos this is all just shooting-the-sh*t.

If a full-bolt-on 335i is capable of 450ish hp (or whatever, not sure of that #), and the limitations are not fuel-related, I do not see how the F8X is going to be able to do much more than that. The golden rule needs to be repeated more on this forum than it is: There is no replacement for displacement.

Now yes, this engine is more robust, can take more boost, has forged internals, etc but NONE of that matters if the small and quick-spooling turbos on this car just can't flow.

FI is a replacement for displacement... A 3l engine with a boost of 1bar has the same performance potential as a 6l NA engine... (but obviously a 4l engine at the same boost is potentially as strong as a 8l engine... So yes, displacement still makes a difference, but FI is a different way of increasing effective displacement).

And I believe the turbos combine quick spool up and good flow, see my post above for details. Since the S55 turbos operate at 200.000rpm (50.000 more than in NeXT years F1 engines), a small turbine with a large wastegate can spin a fairly big compressor wheel and make good boost even at low rpm's (due to high rpm of turbine shaft).

[Penguino]

The problem with the S55 is the 3.0L. If the car were to have a 3.2L or 3.4L engine then it'll be a bit harder to compare the S55 with the N54, but since both are the same exact CR, bore and stroke then the only difference might be the turbos, cooling, and potentially different fueling system. An N54 struggles to break 400whp on pump gas without meth. But again, this is not an N54.

If the S55 runs 12-14psi stock (18.9psi is MAX), and it's rated at 425hp (431ps), and we all know BMW is underrating this engine, then you are looking at least 370-390whp STOCK. That's STOCK! Perhaps we are underestimating the size of the stock turbo or the tuning potential of this car.

Now we go to the "limited" tuning potential predicted by many of you. At 370whp-390whp stock, that is already running close to a FBO N54 with a full warranty at your disposal and stock drive-ability and reliability. That right there should be plenty enough for most of us. Now, BMW will NEVER produce an engine where it's working at its full potential just because of reliability issues, warranty and even potential lawsuits. A FBO S55 should be over 450whp easily. Spent the $10k you'd have spent on an S65 SC on an pair of upgraded turbos and you`ll be over 550whp without a doubt.

So relax. The fact that you don't see the potential doesn't mean it is not there.

[Penguino]

Originally Posted by basscadet

Maybe. But until we know the specifications of the turbos this is all just shooting-the-sh*t.

If a full-bolt-on 335i is capable of 450ish hp (or whatever, not sure of that #), and the limitations are not fuel-related, I do not see how the F8X is going to be able to do much more than that. The golden rule needs to be repeated more on this forum than it is: There is no replacement for displacement.

Now yes, this engine is more robust, can take more boost, has forged internals, etc but NONE of that matters if the small and quick-spooling turbos on this car just can't flow.

By the way, are we really happy with straight-line performance equal to a bolt-on, last-generation 3-series? We need to aim higher in our expectations.

One of the indications that turbos are flowing is power holding up top. BMW dynos shows power peeking at redline and holding until 7200rpm. This could just be proper tuning, but also an indication that the turbos are not really running out of air up top.

[BlackLight]

Originally Posted by basscadet

...If a full-bolt-on 335i is capable of 450ish hp (or whatever, not sure of that #), and the limitations are not fuel-related, I do not see how the F8X is going to be able to do much more than that...

the 335i was not designed to run reliably at 450hp. The 450hp is reached by exceeding the margins the factory thought prudent.
And the same philosophy went into designing the S55, therefore it will have the same percentages for margin when stock.

[solstice]

I'm not so sure about that the flat power curve on top indicates that the turbos are under utilized. Isn't this what you would expect when the turbos spin at full capacity and as rpm grow and they no longer can support peak pressure the rpm linear power growth by more combustion cycles per time unit is equalized by the linear inability of the turbos to support the air volume resulting in the same volume of fuel per time unit and a flat power curve?

[basscadet]

Originally Posted by carlitosz

One of the indications that turbos are flowing is power holding up top. BMW dynos shows power peeking at redline and holding until 7200rpm. This could just be proper tuning, but also an indication that the turbos are not really running out of air up top.

This is a question of tuning and controlling boost taper at higher RPM.

I am not arguing that there isn't power left on the table, I am just saying that I find it highly unlikely that there is gobs of power waiting to be untapped by the aftermarket as there was with the N54.

While I think we can get more out of this engine than we did the S65, I don't see people cracking 500hp without full bolt ons (FBO), a tune, intake, and supporting fuel mods. Compare this to other modern turbo engines in performance cars such as GT-R, M5, and 911 Turbo where they develop 50+ whp with simply a tune and you can see why I'm disappointed in what many expect to be the "tuneability" of this motor.

Bottom line, 3.0 liters isn't cutting it in this price bracket.

[basscadet]

Originally Posted by BlackLight

the 335i was not designed to run reliably at 450hp. The 450hp is reached by exceeding the margins the factory thought prudent.
And the same philosophy went into designing the S55, therefore it will have the same percentages for margin when stock.

It will have even less margins as BMW has expectations that this car will see track duty (heat!) and they have maximized the output as much as they can while keeping the car reliable.

Looking at the history of M3s, I think all of them came to market pretty much tweaked as much as you could possibly expect.

Compare this with the AMG C63 engine which basically burps out 50 whp with a tune alone...which is incredible for a NA engine.

My point: BMW squeaks by with the bare minimum. We're beat over the head constantly with their "handling" and "chassis" to make up for the lack of "crude power". How about this, guys? GIVE US BOTH. Or at least, do what Mercedes and Audi do and give us the option (Black series, RS series) of putting TRUE hot hi-po engines in your cars.

[Penguino]

Originally Posted by basscadet

This is a question of tuning and controlling boost taper at higher RPM.

I am not arguing that there isn't power left on the table, I am just saying that I find it highly unlikely that there is gobs of power waiting to be untapped by the aftermarket as there was with the N54.

While I think we can get more out of this engine than we did the S65, I don't see people cracking 500hp without full bolt ons (FBO), a tune, intake, and supporting fuel mods. Compare this to other modern turbo engines in performance cars such as GT-R, M5, and 911 Turbo where they develop 50+ whp with simply a tune and you can see why I'm disappointed in what many expect to be the "tuneability" of this motor.

Bottom line, 3.0 liters isn't cutting it in this price bracket.

You are comparing a 3.8L to a 3.0L. A GT-R/911 Turbo will pick power proportional to its displacement. I believe the S55 will boost 12-14psi stock, not 18.9psi which people think. If this holds up then it'll make 139hp/L, nearly identical to the GTR 140hp/L at the same 12-14psi stock. A GTR picks up 97whp FBO (intake, exhaust, injectors, tune) on 91oct at 17psi. That's about 25whp/L. +75whp (25whp/L) out of the S55 with a proper FBO setup is not something unimaginable. I know these are different engines and not comparable, but you get an idea.

And I agree with you, the issue here is the 3.0L. This engine should have been 3.2-3.4L.

[swamp2]

Originally Posted by Boss330

But anyway, look at RS6 spec, F10 M5 spec and notice how soon they build pressure (and power) from idle. And both have been tuned to increase power by 25% on stock turbos. Let's say that the S55 relatively has slightly smaller turbos, should still be able to do a 20% increase. Which brings us to 515hp, or +85hp.

Those appear to be good examples on which to base some super back of the envelope ratio type calculations.

540 hp is a better estimate though since the car will likely put down 450 crank, being underrated by 20-30 hp. I'm pretty confident, that the S55 with stock turbos and little to no other hardware changes will reliably permit this, i.e. around 550 hp. Of course the question may be can the ECU be cracked/augmented/circumvented and how long will that take? It certainly begs the question if the "absolutely lag free" throttle response can be maintained at such power levels.

[Savory]

Originally Posted by basscadet

It will have even less margins as BMW has expectations that this car will see track duty (heat!) and they have maximized the output as much as they can while keeping the car reliable.

Looking at the history of M3s, I think all of them came to market pretty much tweaked as much as you could possibly expect.

Compare this with the AMG C63 engine which basically burps out 50 whp with a tune alone...which is incredible for a NA engine.

My point: BMW squeaks by with the bare minimum. We're beat over the head constantly with their "handling" and "chassis" to make up for the lack of "crude power". How about this, guys? GIVE US BOTH. Or at least, do what Mercedes and Audi do and give us the option (Black series, RS series) of putting TRUE hot hi-po engines in your cars.

Until you can substantiate those bolded points, your guess is good as ours. We don't know what the limiting factors are until tuners get their hands on one. Closed deck block could possibly mean more resilience to boost, though that's if the turbos are up to it. It is true, there is only so much 3 liters of displacement can do reliably, but 430 hp is admittedly not that much for an engine to handle by today's standards. Time will tell..

[Transfer]

Originally Posted by Mike Benvo

There is going to be some power left on the table tuning wise with the S55 motor - but it's not going to be as much as we've seen from the N54 motors. The biggest battle the S55 will face is controlling temperature. With upgraded cooling, there is much more potential, but with the factory cooling system, there may issues keeping temperatures down on more aggressive software.

Holy crap. You're back. I'm glad I'm not the only one seeing temperature control as being a significant limiting factor.

[Boss330]

Some info on the electric wastegate actuators:

"Electric actuators provide higher control dynamics and better accuracy and resolution in controlling the position of the wastegate,
since they are independent of unstable vacuum conditions found in gasoline engines,"
"The improved performance allows more precise control of the turbo charger in critical areas of operation
– a major pre-requisite for increasing the lifetime of the charger.

"Electric actuators also shorten the so-called 'turbo lag' and produces less 'turbo flutter,'
a sound heard when lifting off the throttle in a turbo-charged car.
Some have described this noise as the sound of a chipmunk or a rattlesnake."

I wonder whether the electric control over the wastegate will be an advantage for tuners, or just one more "problem" to overcome?