Vishnu N54 Fuel System Research Part 2

farbmw · 04-12-2011, 05:32 PM

Shiv that is excellent my man, but I need to see part 3 ASAP!!

Doug007 · 04-12-2011, 05:47 PM

Shiv,

Can you go into a bit more detail about how the amount of fuel fed to the HPFP is controlled?

The HPFP is an engine driven positive displacement pump, unlike the LPFP which is centrifugal and variable speed. Fuel is incompressible so the HPFP should be pumping an amount that is proportional to rpm (since it's engine driven) all the time. I don't really understand how a valve can affect the amount of fuel "gulped" by the HPFP.

Even if it reduces the pressure of the fuel, pressure has a negligible effect of fuel density so the HPFP would gulp the same amount that would only really change with engine speed.

Is the displacement of the HPFP pistons variable somehow? What am I missing?

Slidewayz · 04-12-2011, 06:03 PM

Quote:

Originally Posted by phazedkid

+1
Also keep in mind that the 1 yr old pump is from Vishnu's shop car. It was probably working overtime from day 1.

Not saying all other pumps should be fine. We just shouldn't generalize the durability of all LPFPs from a sample size of 1.

Although I'll admit that I personally find it a bit alarming.

It would be great to see 10 used LPFPs tested and the results plotted on a graph against a control group of maybe 5 new LPFPs...maybe BMW's done that already? It would be an expensive test, but the data would be really solid versus what we have, which is suggestive but not definitive.

BobS · 04-12-2011, 06:12 PM

Good stuff shiv!

Maybe i'm off, but from what i'm reading, it seems maybe these cars that are eating through HPFP after HPFP might actually have a bad LPFP that is causing the HPFP to cavitate or fail. Would you agree shiv?

wren57 · 04-12-2011, 06:17 PM

Cliff notes? The pump doesn't pump fast enough?

TT3 iN NyC · 04-12-2011, 06:38 PM

This is one of the reason I went PROcede over other tunes. Great job. Can't wait to push the N54 to its limit!

klipseracer · 04-12-2011, 07:06 PM

135i · 04-12-2011, 07:11 PM

can't wait to buy this when its out. whoop.

Brey335i · 04-12-2011, 07:12 PM

Can't wait for part 3!

secretsquirrel · 04-12-2011, 08:44 PM

Quote:

Originally Posted by BobS

Good stuff shiv!

Maybe i'm off, but from what i'm reading, it seems maybe these cars that are eating through HPFP after HPFP might actually have a bad LPFP that is causing the HPFP to cavitate or fail. Would you agree shiv?

Very possible. My HPFP was fine for 55k miles until the LPFP switch died. My HPFP died a couple of months after that.

JoeyFiasco · 04-12-2011, 08:53 PM

I wonder what the end result of this will be..

Mark313 · 04-12-2011, 08:59 PM

Quote:

Originally Posted by JoeyFiasco

I wonder what the end result of this will be..

600rwhp on pump gas stock turbos.

Ulrich · 04-12-2011, 09:06 PM

Quote:

Originally Posted by Mark313

Quote:

Originally Posted by JoeyFiasco

I wonder what the end result of this will be..

600rwhp on pump gas stock turbos.

Gyeah right.....

AYF80 · 04-12-2011, 09:53 PM

So, even a new pump can only supply 430 HP or so of Fuel?

I guess i don’t understand. If our pumps push more volume than most other car pumps, then why do they not push enough fuel for High HP numbers?

WDBi · 04-12-2011, 10:43 PM

http://www.rceng.com/technical.aspx
this is a pretty good read and they have a pretty nifty calculator at the bottom

sneaks · 04-12-2011, 10:44 PM

need one of these for each cylinder.. crazy it starts at idle flow

WDBi · 04-12-2011, 10:48 PM

with a flow rate of 500 lb/hr you could make over 700hp is that correct

JoeyFiasco · 04-12-2011, 10:49 PM

Quote:

Originally Posted by sneaks

need one of these for each cylinder.. crazy it starts at idle flow

yikes..

Sniz · 04-12-2011, 10:50 PM

Quote:

Originally Posted by sneaks

need one of these for each cylinder.. crazy it starts at idle flow

wow

havand · 04-12-2011, 11:37 PM

Quote:

Originally Posted by Doug007

Shiv,

Can you go into a bit more detail about how the amount of fuel fed to the HPFP is controlled?

The HPFP is an engine driven positive displacement pump, unlike the LPFP which is centrifugal and variable speed. Fuel is incompressible so the HPFP should be pumping an amount that is proportional to rpm (since it's engine driven) all the time. I don't really understand how a valve can affect the amount of fuel "gulped" by the HPFP.

Even if it reduces the pressure of the fuel, pressure has a negligible effect of fuel density so the HPFP would gulp the same amount that would only really change with engine speed.

Is the displacement of the HPFP pistons variable somehow? What am I missing?

I had this same thought when I read part 1.

So, if the system regulates the input to the pump... seems bad. If it literally cuts the supply of fuel, the pump is pulling against a vacuum at high rpm, low load situations, (ie, coasting your speed down) or if the low side pump cannot supply enough fuel. To me, this seems like the root problem, not necessarily just a lowside fuel supply issue. It is a design flaw. The fuel supply issue could contribute, but even with a massive lowside supply pump, high rpm and low load would still do the pump in over time.

I am surprised that they do not circulate the excess fuel/pressure from after the hpfp pump back to the lowside supply. Running a pump with a dry input is bad. Especially if is force driven by the engine.

EDIT: I am kinda thinking what you are missing is causing the damage to the pump. Just my guess though and I could definitely be wrong.

PKumarM3 · 04-13-2011, 12:00 AM

his pdf was 7 pages. what we've gotten is around 2 full pages. u do the math

KyLu II · 04-13-2011, 12:02 AM

Good read, can't wait for part 3 of the series.
And about DAMN time!

04-12-2011, 05:32 PM	#45
farbmw Brigadier General 432 Rep 4,501 Posts Drives: 2015 M4 6SPD MANUAL! Join Date: Aug 2009 Location: Toronto iTrader: (11)	Shiv that is excellent my man, but I need to see part 3 ASAP!! __________________ Have BT Tool professional, will scan and clear codes on your BMW. And now I am able to code my 2011 335is and M4 Link to my M4 euro delivery! http://f80.bimmerpost.com/forums/sho....php?t=1006526
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04-12-2011, 05:47 PM	#46
Doug007 Second Lieutenant 6 Rep 291 Posts Drives: Spacegrau 2009 335i 6MT Join Date: Feb 2010 Location: Houston, TX iTrader: (0)	Shiv, Can you go into a bit more detail about how the amount of fuel fed to the HPFP is controlled? The HPFP is an engine driven positive displacement pump, unlike the LPFP which is centrifugal and variable speed. Fuel is incompressible so the HPFP should be pumping an amount that is proportional to rpm (since it's engine driven) all the time. I don't really understand how a valve can affect the amount of fuel "gulped" by the HPFP. Even if it reduces the pressure of the fuel, pressure has a negligible effect of fuel density so the HPFP would gulp the same amount that would only really change with engine speed. Is the displacement of the HPFP pistons variable somehow? What am I missing? __________________ 2009 Spacegrau 335i
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04-12-2011, 06:12 PM	#48
BobS Colonel 98 Rep 2,002 Posts Drives: M3 Join Date: Feb 2009 Location: Southern NJ iTrader: (0)	Good stuff shiv! Maybe i'm off, but from what i'm reading, it seems maybe these cars that are eating through HPFP after HPFP might actually have a bad LPFP that is causing the HPFP to cavitate or fail. Would you agree shiv? __________________ ESS 650 ACM-R Upgrades
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04-12-2011, 06:17 PM	#49
wren57 Roll Tide 605 Rep 2,363 Posts Drives: 335i Join Date: Jul 2010 Location: St Louis iTrader: (10)	Cliff notes? The pump doesn't pump fast enough? __________________ Fix your broken/stripped cowl bolts with this elegant brass solution! http://www.e90post.com/forums/showthread.php?p=20230306
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04-12-2011, 06:38 PM	#50
TT3 iN NyC Colonel 249 Rep 2,567 Posts Drives: F80 M3CS Join Date: Aug 2007 Location: NYC iTrader: (9)	This is one of the reason I went PROcede over other tunes. Great job. Can't wait to push the N54 to its limit! __________________ 07 e92 335i - Retired 18 F80 M3CS - Retired 21 G20 330i M-Sport - Current
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04-12-2011, 07:06 PM	#51
klipseracer Banned 228 Rep 3,012 Posts Drives: 2007 E90 335i, 05 E46 330i Join Date: Aug 2009 Location: Arizona iTrader: (27) Garage List 2007 335i [0.00] 2005 330i [0.00]
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04-12-2011, 07:11 PM	#52
135i Cobb Stage 2+/ICarbon/HPF/Stett 41 Rep 488 Posts Drives: E92 335i 6MT Join Date: Aug 2007 Location: Deep in the Heart iTrader: (0)	can't wait to buy this when its out. whoop.
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04-12-2011, 07:12 PM	#53
Brey335i Banned 118 Rep 4,771 Posts Drives: e46 ///M3 Join Date: Oct 2009 Location: Austin, TX iTrader: (11)	Can't wait for part 3!
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04-12-2011, 08:53 PM	#55
JoeyFiasco Major 26 Rep 1,211 Posts Drives: '09 Coupe Join Date: Aug 2008 Location: P'boro, UK iTrader: (0)	I wonder what the end result of this will be..
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04-12-2011, 09:53 PM	#58
AYF80 Major 82 Rep 1,142 Posts Drives: 2015 AY F80 Join Date: Sep 2009 Location: Nashville, TN iTrader: (0)	So, even a new pump can only supply 430 HP or so of Fuel? I guess i don’t understand. If our pumps push more volume than most other car pumps, then why do they not push enough fuel for High HP numbers?
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04-12-2011, 10:43 PM	#59
WDBi Captain 126 Rep 739 Posts Drives: a car Join Date: Aug 2010 Location: over there iTrader: (2)	http://www.rceng.com/technical.aspx this is a pretty good read and they have a pretty nifty calculator at the bottom
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04-12-2011, 10:44 PM	#60
sneaks Lieutenant 17 Rep 431 Posts Drives: '08 335xi Join Date: Apr 2008 Location: 24 Sussex iTrader: (1) Garage List 2008 335xi [0.00]	need one of these for each cylinder.. crazy it starts at idle flow
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04-12-2011, 10:48 PM	#61
WDBi Captain 126 Rep 739 Posts Drives: a car Join Date: Aug 2010 Location: over there iTrader: (2)	with a flow rate of 500 lb/hr you could make over 700hp is that correct
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04-13-2011, 12:00 AM	#65
PKumarM3 Air India 147 Rep 1,834 Posts Drives: 2018 Dodge Durango Join Date: Dec 2007 Location: NJ iTrader: (8)	his pdf was 7 pages. what we've gotten is around 2 full pages. u do the math __________________ PKumarM3
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04-13-2011, 12:02 AM	#66
KyLu II FREE DREAMK 164 Rep 9,321 Posts Drives: the shiiit! Join Date: Aug 2009 Location: Vineland, NJ iTrader: (6) Garage List 2011 Lexus LFA [3.76]	Good read, can't wait for part 3 of the series. And about DAMN time! __________________ Last edited by KyLu II; 04-13-2011 at 10:39 AM..
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