550i motor

Why does the motor in the new 550i fall on its face after 5500 RPM's? Good tourqe before that, but why?

The main reason is restricted airflow due to an air intake that is essentially a baffle. Supposedly Dinan has an intake in the works.

Originally Posted by TahoeM3

The main reason is restricted airflow due to an air intake that is essentially a baffle. Supposedly Dinan has an intake in the works.

That is clearly a simplification. I'm pretty sure BMW engineers are smart enough that they didn't wake up one morning and realize they put on an intake that was not right for the car.

I feel certain its all a balancing act to get the power, economy and drive-ability characteristics they wanted. All engines fall on their face at some RPM, what's the difference where it is if the car has the performance the manufacturer is shooting for?

Also, if you understand the relationship between torque and horsepower, you know that there are usually tradeoffs. In this case, with 450 lb ft of toque, to get the peak horsepower and RPM's up higher it is very likely that they would be dealing with cylinder pressures that could create problems. The car has an unusually high combination of turbo boost and compression ratio that helps give it more responsive acceleration and the 450 lb ft of torque.

Originally Posted by jjsC6

That is clearly a simplification. I'm pretty sure BMW engineers are smart enough that they didn't wake up one morning and realize they put on an intake that was not right for the car.

I feel certain its all a balancing act to get the power, economy and drive-ability characteristics they wanted. All engines fall on their face at some RPM, what's the difference where it is if the car has the performance the manufacturer is shooting for?

Also, if you understand the relationship between torque and horsepower, you know that there are usually tradeoffs. In this case, with 450 lb ft of toque, to get the peak horsepower and RPM's up higher it is very likely that they would be dealing with cylinder pressures that could create problems. The car has an unusually high combination of turbo boost and compression ratio that helps give it more responsive acceleration and the 450 lb ft of torque.

Don't forget, a lot of the intake design is due to sound absorption and baffling. WHich is not necessarily good for airflow.

Having two big turbos on top of the engine is prone to making a lot of noise. Not what most BMW customers want...

Originally Posted by Needsdecaf

Don't forget, a lot of the intake design is due to sound absorption and baffling. WHich is not necessarily good for airflow.

Having two big turbos on top of the engine is prone to making a lot of noise. Not what most BMW customers want...

Good points.

Originally Posted by jjsC6

That is clearly a simplification. I'm pretty sure BMW engineers are smart enough that they didn't wake up one morning and realize they put on an intake that was not right for the car.

Have you ever seen the intake on the 550i/X5 50i? In case you haven't, I can post pics, but in the mean time I'll give you the basics...it's a jumble of tubes. Air enters through two narrow channels off the grille and curves up and then down as it goes back to the back of the engine, diving underneath the airbox, changes directions 180 degrees and goes up through a restrictor plate with integrated air filter, then back forward to the front of the engine, where it changes directions 180 degrees again before entering the turbo inlets. The net result of that is that the air flow is slowed down and restricted. If you look at the M engine, the air pathway is wide open and goes straight off the grille into the airboxes at the front of the engine and then into the turbos.

I'm not saying BMW put on an intake "that was not right for the car." I'm saying that BMW purposely limited airflow for a couple of reasons...

1. To restrict max power so that the horsepower isn't close to the M engine. They are the same basic engine design after all. If you look at the dyno graphs, the power is very close until 4500 rpm when the 50i flattens of and the M keeps going up.

2. To decrease intake and turbo noise. This is supposed to be the more refined version, so less noise would be the goal.

If you understand the relationship between horsepower and torque, you will understand that horsepower is a function of torque. As revs go up, horsepower increases linearly with revs as long as torque is a constant...which it pretty much is in a turbo engine like this. The only way to prevent power from continuing to rise is through limiting airflow, which they did.

The engine is tuned for good low-end power, but that's normal with a turbo engine. Torque peak always comes early when the turbos spool up. The boost levels on a stock N63 are actually quite low for a modern turbo engine...only around 9.8 psi (with a compression ratio of 10, which also isn't high). The M motor makes around 17 psi stock with only a slightly lower compression ratio (around 9.3, if I recall).

Originally Posted by TahoeM3

Have you ever seen the intake on the 550i/X5 50i? In case you haven't, I can post pics, but in the mean time I'll give you the basics...it's a jumble of tubes. Air enters through two narrow channels off the grille and curves up and then down as it goes back to the back of the engine, diving underneath the airbox, changes directions 180 degrees and goes up through a restrictor plate with integrated air filter, then back forward to the front of the engine, where it changes directions 180 degrees again before entering the turbo inlets. The net result of that is that the air flow is slowed down and restricted. If you look at the M engine, the air pathway is wide open and goes straight off the grille into the airboxes at the front of the engine and then into the turbos.

I'm not saying BMW put on an intake "that was not right for the car." I'm saying that BMW purposely limited airflow for a couple of reasons...

1. To restrict max power so that the horsepower isn't close to the M engine. They are the same basic engine design after all. If you look at the dyno graphs, the power is very close until 4500 rpm when the 50i flattens of and the M keeps going up.

2. To decrease intake and turbo noise. This is supposed to be the more refined version, so less noise would be the goal.

If you understand the relationship between horsepower and torque, you will understand that horsepower is a function of torque. As revs go up, horsepower increases linearly with revs as long as torque is a constant...which it pretty much is in a turbo engine like this. The only way to prevent power from continuing to rise is through limiting airflow, which they did.

The engine is tuned for good low-end power, but that's normal with a turbo engine. Torque peak always comes early when the turbos spool up. The boost levels on a stock N63 are actually quite low for a modern turbo engine...only around 9.8 psi (with a compression ratio of 10, which also isn't high). The M motor makes around 17 psi stock with only a slightly lower compression ratio (around 9.3, if I recall).

To your first point, of course they limited the horsepower to 400. That's the power they wanted for the car - doesn't matter why.

Of course I understand the relationship of hp and torque - that was my point. The more you increase the RPM's to make more horsepower, the more you have to contend with the cylinder pressures of a turbocharged engine with a 10-1 compression ratio.

I get everything you are saying, and you no doubt know something about engines. But to say the intake is the limiting factor doesn't really make sense. My point was that they designed the engine to meet the parameters they were looking for in the car and there are many ways to give or take power. The car runs the 1/4 mile in the very low 13's at up around 109mph. That's the part that counts - not how many RPM's it turns. Those are all tradeoffs to get the end result they were looking for.

As to the M engine, you know damn well that they also had to spend a lot of money to put components in the engine (and the rest of the drivetrain) that can hold up to the durability testing that nearly 600 hp (or whatever it really has) requires.

TahoeM3

I want to follow up to our earlier discussions. As I thought about this later in the day, I do think I took your original response out of context. I think what you were saying is that the intake manifold is the best source of easy hp and I took what you said to mean that the intake was the problem on the car.

I apologize if you and I were looking at it from two different angles.

Originally Posted by jjsC6

TahoeM3

I want to follow up to our earlier discussions. As I thought about this later in the day, I do think I took your original response out of context. I think what you were saying is that the intake manifold is the best source of easy hp and I took what you said to mean that the intake was the problem on the car.

I apologize if you and I were looking at it from two different angles.

No worries...it's both but really more the intake design itself. When you see it, you'll realize they BMW clearly designed it to be restrictive and difficult to modify. There have been a few discussions on this. I'll post the pics.

I suspect that they designed the engine with certain goals in mind, then detuned it for the 550i/X 50i. It's easy to do if you cut back boost and limit airflow. That's why Dinan was able to get back an easy 95 hp by cranking up the boost. Beyond increased boost, the next limiting factor is going to be airflow...on the intake and exhaust side (esp downpipes). We will see what the tuners can come up with.

It's just not very BMW like to me. Drove an E60 M5 yesterday and probably going to buy it Monday. As the motor spins faster, the more and more power you get. A seriously awesome engine. Also has more low end than you would think.

Originally Posted by nwilson44

It's just not very BMW like to me. Drove an E60 M5 yesterday and probably going to buy it Monday. As the motor spins faster, the more and more power you get. A seriously awesome engine. Also has more low end than you would think.

The E60 M5's V10 essentially a Formula One motor in a sedan. The more you rev it the more power it produces. But it has little power around town and off the line and I often used to smoke that car in my E60 550 up to about 40 miles an hour from a Stoplight

The Dinan Stage 2 doesn't have the same drop-off. It's a more natural linear curve with a higher drop off.

That said, the engine has so much power I rarely see the need to rev it that high. That's what I love about this car is you can shift at 3500-4000 rpm and get superb acceleration without stressing the engine.

Originally Posted by Stealth.Pilot

The Dinan Stage 2 doesn't have the same drop-off. It's a more natural linear curve with a higher drop off.

That said, the engine has so much power I rarely see the need to rev it that high. That's what I love about this car is you can shift at 3500-4000 rpm and get superb acceleration without stressing the engine.

The Dinan tune on my X5 50i still has a drop off at higher rpms, especially compared to the M version. It's not as noticeable, but it's still there. An intake will make a lot of difference on this engine.

The E60 M5 has a soul though that's what i liked. For the same price I could get a 2012 550i, but the engine not only has no soul, it falls on its face at around 5500. The F1 derived V10 is simply amazing. I admire the low end torque, just not at the expense of a soul and the anti-BMW flat top end.

Originally Posted by nwilson44

The E60 M5 has a soul though that's what i liked. For the same price I could get a 2012 550i, but the engine not only has no soul, it falls on its face at around 5500. The F1 derived V10 is simply amazing. I admire the low end torque, just not at the expense of a soul and the anti-BMW flat top end.

This is complete garbage.

Originally Posted by nwilson44

The E60 M5 has a soul though that's what i liked. For the same price I could get a 2012 550i, but the engine not only has no soul, it falls on its face at around 5500. The F1 derived V10 is simply amazing. I admire the low end torque, just not at the expense of a soul and the anti-BMW flat top end.

I couldn't agree more. Really wanted to get the F10 550i, but ultimately it didn't put a smile on my face so ended up with an M5 with 6K miles for basically the same price as a new 550i. Drawbacks for the M5 are: clunky (and eventual maintenance cost) of SMG-equipped cars (though I didn't want the manual, as this car would be for commuting) and fuel consumption.

I will keep my 550, with a dinan stage 2, there are few on the road that can keep up and can still get decent gas milage on long trips.

Originally Posted by Steamer

I will keep my 550, with a dinan stage 2, there are few on the road that can keep up and can still get decent gas milage on long trips.

I actually think the Dinan's are getting better gas mileage than stock. That is, the one's with owners with some resemblance of self-control.

As far as the high rpm performance fall-off I believe it is a combination of the air-intake and the single size turbos. This is where the straight sixes with the dual and tri-turbo designs have an advantage.

Originally Posted by dunderhi

I actually think the Dinan's are getting better gas mileage than stock. That is, the one's with owners with some resemblance of self-control.

Self control, I have heard of this, I believe I saw it once but just can't remember were.

Maybe the new M5 is better with regards to high RPM pull.

Yeah but open up the ten throttle bodies and damn lol the surge and sound is incomparable.

Sent from my PH44100 using Bimmer App

Originally Posted by nwilson44

Yeah but open up the ten throttle bodies and damn lol the surge and sound is incomparable.

Sent from my PH44100 using Bimmer App

The sound is indeed great. Will say this in defense of the 550i: lower in the RPM range, and in everyday traffic, the 550i feels considerably faster. But the M wasn't really built for everyday traffic, so you could almost forgive it this shortcoming. Per Top Gear, the E60 M5 will do 204 mph - it pulls effortlessly at higher speeds, but is a little less impressive at everyday speeds. Still love it, though. It's a great deal of fun to drive - even though it sounds like a diesel when it starts up!

Originally Posted by nhs156

I couldn't agree more. Really wanted to get the F10 550i, but ultimately it didn't put a smile on my face so ended up with an M5 with 6K miles for basically the same price as a new 550i. Drawbacks for the M5 are: clunky (and eventual maintenance cost) of SMG-equipped cars (though I didn't want the manual, as this car would be for commuting) and fuel consumption.

The SMG is dead. The impressive thing about the new M5 is that it is actually smoother than the F10.

Yeah until you drive the M like its a manual transmission with a clutch, that happens to be computer controlled, then its jerky. But once you learn it It's great. Idk. I liked the new 550i until I hit it at 80 MPH. don't get me wrong it wasn't slow it just didn't pull like other BMW'S I've driven. Nice car though.

Originally Posted by nwilson44

Yeah until you drive the M like its a manual transmission with a clutch, that happens to be computer controlled, then its jerky. But once you learn it It's great. Idk. I liked the new 550i until I hit it at 80 MPH. don't get me wrong it wasn't slow it just didn't pull like other BMW'S I've driven. Nice car though.

I still don't understand your issue about pulling. I am 100% my 550i could hammer your M5 in a drag race. I know because I have done it before.