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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Shiv, where's the LPFP?



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      10-09-2012, 08:18 AM   #23
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Originally Posted by Sered View Post
Fuel is matched to airflow, doesn't matter if its one hair-dryer or two. Explain to me how two turbos flowing the same amount of air as one turbo will magically need more fuel (assuming relatively equal powerbands)?
Not entirely, burn time of the fuel and many other variables can come into play. But my point is the lmassive low end torque of the RB's would require quite a bit more fuel than Shiv's single. Peak torque at low RPM's is brutal.
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      10-09-2012, 11:04 AM   #24
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Originally Posted by Fully_Bolted View Post
Ok, so if somehow a set of RB's magically could produce enough volume to reach 650whp - your telling me that they would not require more fuel than your single turbo setup? Please explain
No one said that. But,

RBs don't magically produce enough volume to reach 650whp and because the power is 500whp rather than 650whp, they don't need any more fueling than single despite of the worse BSFC.

If the RBs would magically produce enough volume for 650whp, they would flow similarly and be similar to the single in all the aspects, BSFC included.

Btw. for some reason you talk about RBs all the time. Obsessed? OP has stockers and nobody is talking about RBs here except you They are awesome and worth talking about though, I give you that.

This upgrade is useful for being able to use high concentrations of e85 no matter which turbos you run.
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      10-09-2012, 11:22 AM   #25
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Uhh.. what's BSFC?
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      10-09-2012, 11:50 AM   #26
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Uhh.. what's BSFC?
Just a guess from wiki:

Brake Specific Fuel Consumption (BSFC) is a measure of fuel efficiency within a shaft reciprocating engine. It is the rate of fuel consumption divided by the power produced. It may also be thought of as power-specific fuel consumption, for this reason. BSFC allows the fuel efficiency of different reciprocating engines to be directly compared.
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      10-09-2012, 12:32 PM   #27
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Quote:
Originally Posted by jippii ensio View Post
No one said that. But,

RBs don't magically produce enough volume to reach 650whp and because the power is 500whp rather than 650whp, they don't need any more fueling than single despite of the worse BSFC.

If the RBs would magically produce enough volume for 650whp, they would flow similarly and be similar to the single in all the aspects, BSFC included.

Btw. for some reason you talk about RBs all the time. Obsessed? OP has stockers and nobody is talking about RBs here except you They are awesome and worth talking about though, I give you that.

This upgrade is useful for being able to use high concentrations of e85 no matter which turbos you run.

I could care less about RB's, I believe OP has Vargas stage II's on order hence why i was referencing RB's for conversation.
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      10-09-2012, 12:41 PM   #28
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The sooner you can spool or the lower in the rev range you move peak torque the more fuel volume it's going to need. Just look at where STFT and LTFTs are currently maxxing out on non-flashed cars.

If OP is willing to run the pump why not let him "beta" test it?
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      10-09-2012, 01:04 PM   #29
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Quote:
Originally Posted by Fully_Bolted View Post
Not entirely, burn time of the fuel and many other variables can come into play. But my point is the lmassive low end torque of the RB's would require quite a bit more fuel than Shiv's single. Peak torque at low RPM's is brutal.
Torque means nothing in fuel consumption... HP does. And if there was a need for more low end capacity it would be HPFP related, not LPFP
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      10-09-2012, 01:05 PM   #30
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Torque means nothing in fuel consumption... HP does. And if there was a need for more low end capacity it would be HPFP related, not LPFP
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      10-09-2012, 01:16 PM   #31
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Originally Posted by Joshboody View Post
Torque means nothing in fuel consumption... HP does. And if there was a need for more low end capacity it would be HPFP related, not LPFP
Care to elaborate? I'm all ears
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      10-09-2012, 01:22 PM   #32
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Quote:
Originally Posted by Fully_Bolted View Post
I could care less about RB's, I believe OP has Vargas stage II's on order hence why i was referencing RB's for conversation.
BSFC of those is zero
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      10-09-2012, 01:24 PM   #33
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Quote:
Originally Posted by Fully_Bolted View Post
Care to elaborate? I'm all ears
Because HPFP is rpm dependent.

BSFC that you took up is fuel consumption divided by the power - not torque.
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      10-09-2012, 01:35 PM   #34
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Quote:
Originally Posted by Fully_Bolted View Post
Care to elaborate? I'm all ears
Torque is work and doesn't reference time. HP is power, which is work over time. Torque will equal amount of fuel in the cylinder only, not the total being used over time.

jippii answered the second part.
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      10-09-2012, 01:59 PM   #35
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It's nice to see real tech on a forum.
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      10-09-2012, 02:05 PM   #36
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Quote:
Originally Posted by Joshboody View Post
Torque is work and doesn't reference time. HP is power, which is work over time. Torque will equal amount of fuel in the cylinder only, not the total being used over time.
That's what I thought, too. The fuel injectors are open longest at peak torque, but the amount of fuel used is max at the HP peak, at least that's what I thought.
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      10-09-2012, 02:22 PM   #37
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Quote:
Originally Posted by JamesM3M5 View Post
That's what I thought, too. The fuel injectors are open longest at peak torque, but the amount of fuel used is max at the HP peak, at least that's what I thought.
The injectors are open the longest per ignition cycle at peak torque, but the injector duty cycle should follow the HP graph. (Unless my ideas are way off. )
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      10-09-2012, 02:25 PM   #38
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Quote:
Originally Posted by JamesM3M5 View Post
That's what I thought, too. The fuel injectors are open longest at peak torque, but the amount of fuel used is max at the HP peak, at least that's what I thought.
Keep in mind most tunes will richen the AFR's at higher RPM's.
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      10-09-2012, 04:36 PM   #39
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The injectors are open the longest per ignition cycle at peak torque, but the injector duty cycle should follow the HP graph. (Unless my ideas are way off. )
Duty cycle is function of engine speed. Injection time is a funtion of actual time.

At maximum torque output, the injectors are open the longest in relation to the intake stroke, i.e. a longer duty cycle.

At maximum power output, the injectors are open for a shorter period during the stroke, i.e. shorter duty cycle, but are open for more strokes during a unit of time. That's why maximum power takes the most fuel, but maximum torque takes the longest amount of injector open time during the intake stroke.
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      10-09-2012, 05:56 PM   #40
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Yeah you guys have taken this to a tech level far beyond my comprehension. It has given me a new topic to read though. My sole purpose of the pump is not turbo related. Yes, I have put a deposit on Vargas stage 2 turbos and hope to install them next month. My current quest though is to run 100% e85. Yes, I have a Cobb AP and am running a flash with my jb4 g5 board. My current limitation is the LPFP. AFRs are solid at e60 but FP is tanking. My LPFP quest continues.
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      10-09-2012, 10:47 PM   #41
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Quote:
Originally Posted by JamesM3M5 View Post
Duty cycle is function of engine speed. Injection time is a funtion of actual time.

At maximum torque output, the injectors are open the longest in relation to the intake stroke, i.e. a longer duty cycle.

At maximum power output, the injectors are open for a shorter period during the stroke, i.e. shorter duty cycle, but are open for more strokes during a unit of time. That's why maximum power takes the most fuel, but maximum torque takes the longest amount of injector open time during the intake stroke.
I have not learned this much from a thread on E90post in like a year
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      10-10-2012, 07:02 AM   #42
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Good stuff fella's.
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      10-10-2012, 03:57 PM   #43
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Quote:
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Care to elaborate? I'm all ears
Back to Physics 101 with you! More power requires more fuel.

And I concur, it's nice to see people who know what torque is (and what it isn't).
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      10-11-2012, 09:24 AM   #44
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Quote:
Originally Posted by Sered View Post
Back to Physics 101 with you! More power requires more fuel.

And I concur, it's nice to see people who know what torque is (and what it isn't).
Well, generalizing, yes thats true. All of the BSFC curves i've seen have been from NA motors, and they are generally U shaped, or shaped like a bathtub really. I havent found an accurate one for a small turbo boosted engine, but im curious what it would look like. Needless to say the guys that posted presented great info, im leaving this one alone.
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