N54 Injector limits?

[Flinchy]

so in another thread the topic came up (again) of fuel system limitations.. now talking about finding a solution to the HPFP issue once and for all, so injector limitation came up

with the specs available here: http://www.conti-online.com/www/down...cts_pdf_en.pdf (page 25)

Wanting to get info from people with more experience in the field

How much has already been achieved on them, especially E85 only? High RPM's too, not the usual HPFP dive midrange.

At what stage(s) of the cycle does the N54 inject fuel? purely homogenous (ie intake stroke)?

are we potentially very close to the limit of the injectors in upper RPM's, especially now that big turbo stuff is more commonplace?

The injectors ARE very impressive, given 100% (or 80%) duty cycle over 4 strokes they could flow something close to 3000hp as a set.. but with limited combustion windows, even at stock redline, that rapidly drops (someone care to work it out from the info given?) to something a LOT less exciting.

[mjmarovi]

2,000 HP?

[Flinchy]

2,000 HP?

at least, yeah.

if only -_-

[mjmarovi]

at least, yeah.

if only -_-

Not that I trust anything on the other forum, but there was this exact same discussion over there and the consensus was 1,000 hp. Crank

[Flinchy]

Not that I trust anything on the other forum, but there was this exact same discussion over there and the consensus was 1,000 hp. Crank

was there any working out done or just wild guesses?

[mjmarovi]

was there any working out done or just wild guesses?

There was some thought behind it, but I'd say if on a scale, it'd be tipping toward the wild guess side...ya know as usual over there...it's funny cause I feel more like a novice on this forum but in the rare occasion I go over there (get a PM notified by email for some reason) I feel like a $#@!ing automotive engineer...

[Flinchy]

There was some thought behind it, but I'd say if on a scale, it'd be tipping toward the wild guess side...ya know as usual over there...it's funny cause I feel more like a novice on this forum but in the rare occasion I go over there (get a PM notified by email for some reason) I feel like a $#@!ing automotive engineer...

I just can't see a way using the specs given (not assuming they're understated like they almost certainly are), to get the gas numbers over 750-800 tops @7k (with 1.5 strokes used to inject), and much over 550 on E85 (which is not cool, and doesn't sound right to me)

I'm just hoping i've done the math wrong, or there's a TON of headroom left in the injectors unstated lol.

[Sticky]

Wish I could remember which thread it was that I read somebody mapped it out. It was probably @DBFIU. I haven't see him browsing in forever though.

[Eleventeen]

Okay, so how how many cc/m does 35 g/s equal? I'm sure there's more to it that than, but curious to know.

[Sticky]

Okay, so how how many cc/m does 35 g/s equal? I'm sure there's more to it that than, but curious to know.

I didn't stop taking math courses years ago for you to spring a pop quiz on me.

[Flinchy]

Okay, so how how many cc/m does 35 g/s equal? I'm sure there's more to it that than, but curious to know.

I think one of the other threads worked out that disregarding everything to do with injection window, if you could flow the full 35g/s out of all 6 injectors it's enough fuel for something like 3000hp~.. as for CC/min?

Hold on...

.711kg/liter, 2100g/min, that's 2955cc.. so 3000cc/min injectors in that measurement right?

However, the whole can only inject for 25-50% of your RPM thing puts a damper on that

[brusk]

I would imagine that the only limitation to the injector would be the software give DI can have way more time to spray than port injection.

[Tony@VargasTurboTech]

This reminds of the threads I read about people trying to figure out when the motor was going to break using math, equations, and crap. Lets just wait and see when these things tap out and go from there? Anyone anyone?... Just kidding, I actually like reading this stuff.

[mjmarovi]

I would imagine that the only limitation to the injector would be the software give DI can have way more time to spray than port injection.

Yes, and pressure. At 7500RPM you won't be able to spray as much fuel as at 5000RPM since the window opening to actually spray fuel will be much shorter. Higher pressure will help.

[Sticky]

I think the answer is somewhere on this board:

[V8Bait]

There was a thread a few years ago about the HPFP that turned into other stuff, and there was an engineer familiar with the DI system on the N54 that was being communicated with. He had a lot of correct information that nobody else had heard of before, so it seemed legit. Even E85 testing results (and the reason for the newer style oil cooled injectors alluded to before they were available for the car, go figure). There was lots of talking about homogenous mode vs stratified mode, the DME capabilities for each, why piezo injectors etc etc etc. I don't remember much from back then but there was lots of maths.

Some things I remember were the injection window was small but larger than I thought, but with risk of wall wetting increasing proportionately. The DME is capable of any injection strategy, don't remember which one is uses or if it can be changed. The injectors can vary their spray pattern and flow rate dynamically, incredibly precisely, and very quickly... much more than the N55 solenoid injectors. That's all I remember.

[Flinchy]

I would imagine that the only limitation to the injector would be the software give DI can have way more time to spray than port injection.

yes, and working out even if it can inject RIGHT up to combustion from TDC intake, 1 full RPM, 50% duty cycle in effect... they still can't (according to the specs) flow anywhere near enough on E85, and even on race gas it may not satisfy *everyone*.

How can DI have more time to spray?

PI can spray through all 4 strokes, DI, best case scenario, has 2 strokes to spray through.. and i'm not even sure the N54 can do all intake all compression.

This reminds of the threads I read about people trying to figure out when the motor was going to break using math, equations, and crap. Lets just wait and see when these things tap out and go from there? Anyone anyone?... Just kidding, I actually like reading this stuff.

at least working this out may have a semblance of reality compared to trying to work out block strength with only half the info

I agree, even if it's not going to be accurate (like the initial 'N54 will break apart at 500hp'), it's interesting.

The only hope i can see is the injectors being fairly underrated?.. you're right though, hopefully we'll see soon enough with your HPFP work

There was a thread a few years ago about the HPFP that turned into other stuff, and there was an engineer familiar with the DI system on the N54 that was being communicated with. He had a lot of correct information that nobody else had heard of before, so it seemed legit. Even E85 testing results (and the reason for the newer style oil cooled injectors alluded to before they were available for the car, go figure). There was lots of talking about homogenous mode vs stratified mode, the DME capabilities for each, why piezo injectors etc etc etc. I don't remember much from back then but there was lots of maths.

Some things I remember were the injection window was small but larger than I thought, but with risk of wall wetting increasing proportionately. The DME is capable of any injection strategy, don't remember which one is uses or if it can be changed. The injectors can vary their spray pattern and flow rate dynamically, incredibly precisely, and very quickly... much more than the N55 solenoid injectors. That's all I remember.

do you have a link to the thread? the only one i can find with a continental engineer was pretty basic stuff, with non-specific window stuff saying 'yeah it COULD run stratified' and saying that it only runs homogenous (which according to the flow specs is impossible at current power levels, as 4MS at 7k rpm is nowhere near enough for any fun)

with you mentioning wall-wetting, i think we're talking about the same thread maybe lol.

Today i had my follow up conversation with the tech guy at continental. Here are the questions and answers. Enjoy !

Are the pistons forged pistons ?
- Don’t know

Does the N54B30 use homogenous or stratified charge under high load ?
- The engine was developed to run in homogenous mode. The N53 engine was to run in a stratified mode. Although the engine is capable of running in stratified mode, it currently does not.
It uses an outward opening injector.

Have you experience with this engine and E85 fuel or do you have any thought on it ? Can e.g. the injectors handle alcohol ?
We have a lot of experience with E85. Currently, we have an issue that if the injector is hotter than 100 Celsius, we are seeing melting of the fuel filter in the injectors. As long as the temperature of the injector stays under the 100 Celsius, this engine is perferctly capable to run E85. As a matter of fact, it will run E100 without any problem under cold conditions. There is no need to preheat the fuel.
We are investigating the filter issue, and we hope to have a solution next year. Whether or not we will create injectors for this engine, depends on the market (read: BMW).
It is not possible to replace this filter yourself; you cannot open the injector to get to that part.

Is the HPFP pressure of 90 bar constant or is it controlled by the MSD module ?
It is constant but indeed controlled by the module. The engine has been tested to up to 200 bar. If you keep the HPFP pump below that number, you could inject a lot more fuel. The relation between the amount of fuel sprayed and the pressure is not a linear relation but a Bernulli equation.

In our earlier conversion, you mentioned that under high load the TI is about 2 ms ? Correct ?
Yes maximum is 2 ms. Notice that the engine runs under homogenous mode and that means that the injection start in the intake phase. With this engine, it is no problem to keep injection into the compression phase, but not too long; it would be bad for emission. However, if the pressure of the HPFP is increased, this may not be needed.

The injectors have a maximum of 40 mg/ms spray at 200 bar. This is an increadible amount of fuel, much much more than any solenoid injector. It is this high, because when we designed the application, BMW insisted that the engine must be able - in limp mode - to only use the LPFP pressure, which is 5 bar, and still drive the vehicle at 170 km/h.


If correct, do you agree then that considering the ti in the compression phase, we can get it up to 4 ms for 7000 rpm ? Can we use the full compression phase ?

You would have to calculate it, but yes, there is extra time at mentioned before.
The injector can inject a lot of fuel into the cylinder. When increasing the injection time, and also when injecting in the compression phase, look out for cylinder wall wetting. This is dangerous. It would wash away the oil on the walls, causing wear. One way to check for wall wetting is to check the engine oil if it has fuel in it. Another way would be to check if the vapor of the exhaust gas recirculation (EGR) and see if there's fuel vapor.
The risk of wall wetting may be reduced by running higher boost, as it affects air flow inside the cylinder.
Running the HPFP at higher pressure may increase the risk again.

You said we should tune the TI duration of the ignition pulse. Can we also tune with the MSD via a reflesh when the ignition time starts ?
There is indeed a calculated ignitition start time in the MSD. It is not a map, but i'm not sure.

How does the ECU measure a knocking problem ? Does it use voltage ? Does it do it for all 6 cilinders individual ?
Each piezo injector has a knocking sensor. It measures vibration. By looking at certain frequencies, the knocking signal is sent.

EDIT: seems that the engine also has the standard knocking sensors in place.

De community is desperate to lean more about the MSD80. We would love to have information that can help us reflesh the unit to tune to engine for 600 PS. Can you help ? Can you direct us to a colleague (do you have a name ?) This is vital for my own project too !
I don't know about the MSD80. I'm an injection / fuel system engineer. I will talk to some colleagues and see if i can help you with anything. We have to make sure we're not infringing any copyrights and i think BMW owns the rights to the information on the MSD.


Can we buy this information ? Who should I talk to to ?
there may be a legal way to buy this information, i will talk to some colleagues and mail you back.


All of us want to invite you to join our forum N54tech.com. An engineer like you would be incredible value to the forum, may I mail you an invite to join ? It’s free of course !
Thank you for the invitation. I will think about it. I have to be careful not to share information that my company doesn't want us to share.

is that what you were remembering?

not sure how wall wetting could be an issue injecting into compression, high powered cars drink much more fuel all the time... but this doesn't really tell us anything useful, mostly vague and the performance specs are the same as can be found in the pdf >_<

[V8Bait]

Yeah that was one of the threads I remember. There was another one from before that one too, I don't remember where it was from... or maybe I'm confusing that thread and one I was reading on LS1tech back then about DI on the turbo 4pot.

That thread seems familiar though. There have been so many fuel threads, I can't keep them straight LOL

[Eleventeen]

I think the answer is somewhere on this board:

http://www.60-130.com/images/im...00033651-1.jpg

That picture reminds me of my old job. I was a janitor at Harvard and one of the professors used to put these impossible problems up on the board and I used to solve them. Then one day he caught me and thought I was just messing up his work. And there was this chick and some doucher was trying to hit on her and I says to him, I says, do you like apples? And he was all like yeah, and I was like that's cool.

[Flinchy]

Yeah that was one of the threads I remember. There was another one from before that one too, I don't remember where it was from... or maybe I'm confusing that thread and one I was reading on LS1tech back then about DI on the turbo 4pot.

That thread seems familiar though. There have been so many fuel threads, I can't keep them straight LOL

there's also

60sec/6000rpm gives you about 10ms to inject fuel on an intake stroke at 6k rpm. The problem has always been the fuel injectors take time to open and close. Thus on port fuel injection engines, 75-80% duty cycle was the max fuel flow.

BTW, I found the Continental info pdf on the fuel injection systems again (finally!): http://www.conti-online.com/generato...cts_pdf_en.pdf

These are the specs on the injector:
System pressure 50 up to 200 bar
Working flow range > 50
Static flow > 35 g/s
Dynamic flow 14.5 mg/ injection 10% at 0.4 ms PW
Min. dynamic flow < 2 mg/stroke
SMD size ~ 15 µm
Opening/Closing time = 150 µs
Spray angle 94°/98°± 4°
Temperature range – 30 up to +140°C

and on the HPFP:
Max. fuel pressure up to 200 bar
Supply pressure 4.5 up to 6 bar
Temperature range – 40 up to +130°C
Control flow controlled
Drive end of camshaft or belt driven
Maximum flow up to 240 l/h (at 3500 rpm, depending on the # of pistons 2 up to 6)

So, assuming these numbers are accurate and keeping mind they are static flow numbers, using some rough calculations:
35 gm/sec = 277lbs/hr
277lbs/hr * .5lb/hr for 1HP = 554HP from a single fuel injector.

There is probably more to the story restricting how long the injector can actually open because BMW put about 3000HP worth of fuel injectors in a 300HP engine.

The HPFP is 240LPH so, 1.64lbs/L * 240L = 393lbs/hr = 785HP (@ .5lb/h per HP).

Pretty rough numbers (BSFC is wrong) but the general point is there's supposedly a lot of fuel available via the injector and HPFP if their dynamic supply numbers are close to say 80% of their static flow numbers.

This doesn't seem to match up to the real world though so other factors are undoubtedly influencing fuel delivery (lines and fittings, fuel rail, etc).

which i think the only incorrect bit is that at 6k rpm each stroke is 5ms, rather than 10.

his calculations also don't take into account injection window (hence not matching real world lol) which is why i started thinking about this in the first place.

and the HPFP being 240lph @ 3500rpm capable? i'm guessing that's the HPFP itself spinning that fast, not engine RPM. i wonder what the ratio is between crank speed and vac pump/hpfp speed.

[Sticky]

That picture reminds me of my old job. I was a janitor at Harvard and one of the professors used to put these impossible problems up on the board and I used to solve them. Then one day he caught me and thought I was just messing up his work. And there was this chick and some doucher was trying to hit on her and I says to him, I says, do you like apples? And he was all like yeah, and I was like that's cool.

I'm just trying to piece together where I saw this before.

[nitehawk]

I'm just trying to piece together where I saw this before.

Good Will Hunting...?

[Flinchy]

Good Will Hunting...?

ahh i didn't want to spoil the joke for anyone hahahahha

[Sticky]

Good Will Hunting...?

It's based off that obviously but I mean the way that was written.

[brusk]

PI can spray through all 4 strokes, DI, best case scenario, has 2 strokes to spray through.. and i'm not even sure the N54 can do all intake all compression.

Assuming the standard PI using two events per revolution and not using 100% of that cycle to limit the fuel pooling around everywhere. But I've never had a chance to look at the tuning on turbo car running that kind of power to see what tricks are required.