does anyone run on stock fuel system 20 psi boost? need info , thanks

 

You will go lean as 20# reduces the NET EFFECTIVE FUEL PRESSURE so youll go lean. need to have a compensated regulator to work, see NEEDSWINGS for assistance. I have and designed as compensated boost control for the fuel regularor. Its Physics but simple. Enjoy Woody

 

only with regulator i can run 5 bar fuel pressure with stock pump?i can fit s55k cl55k fuel pump maby it has inner 5 bar regulator?

 

Forgive me if this is too much information for you....

Stock fuel pump is a risk at 20psi - depends on age and OEM filter cleanliness.
For 20psi you need 160Lph (42 GPH) and the limit of the OEM pump at 3.9bar OEM pressure (in filter) is 165Lphr.

SL55 internal 5bar FPR = negative, there is no FPR in the pump - I think the pressure is controlled by the Pulse Width Controller and a pressure sensor loop attached to drive the pump. But don't quote me on this - others may know more.

Back to the SRT6....
Some have reported success with
A) a simple pump change
B) others go for larger injectors ...or
C) =A+B

PUMP CHANGE
Go for a WalbroGSL392 (255Lphr) = $150 it'll give you 205Lphr or an extra +20% head room flow at stock FPR of 3.9bar.
An SL55 pump will give you 340Lphr or +100% head room at 3.9bar. IMO this is overkill and $$, plus extra wasted amps with a lot of flow just going back to the tank.

For OEM condition you need about 135L/hr from the pump.
As mentioned above for 20psi and WOT you need around 160L/hr (42USGal/hr)
The stock pump can do 165Lphr at the OEM 3.9bar, but drops to 115Lphr at 5.5bar.
The WalbroGSL392(255) does 205 at 3.9bar and 165 at 5.5bar.
I worked this back to 5.5Bar 'cause there is a case for using the stock injectors at 5.5Bar Fuel Pressure (see below)
-----------------------------------------------------------

INJECTORS
NOW....To work this back to the injectors...
Divide the 160Lphr by 6 injectors and 60minutes per hour, then multiply by 1000cc/Litre and your stacked 20psi case of 160Lphr goes to 444cc/min.
You then need to divide by 80% duty cycle to give you 555cc/min.

The performance of an injector is normally rated at 3bar across the injector from inlet to outlet and rated for a maximum of 80% duty cycle.
In our case, our inlet manifold has back pressure supplied by the supercharger. So you need to work out the differential from Fuel Rail pressure to Manifold Pressure.
I have tried to do this for 4 case scenarios in the attached table and for 2 different fuel rail pressures of OEM and 5.5Bar. But I have subtracted 0.3bar due to the fuel line friction losses form the pump to the inlet manifold. The actual differential across the injector is highlighted in Blue as D

You can see from the table - if you can get your head around it...;
a) the stock injectors duty cycle is 94% even for the 65mm SC case - but the fuel pump should be okay.
b) the stock injectors duty cycle is 104% for the 65/178 20.2psi boost case and the fuel pump is pretty much maxed out (depending on newness and filter cleanliness).
c) The late2006 E55 injectors (Bosch 0280156304, MB 1130780123) will work with the stock fuel pressure but show 89% Duty cycle for the 21.0psi case - that's getting up there.
d) The 550cc/min 52lb injectors (Bosch 0280158117) commonly used will do the business off the stock pressure of 3.9bar (corrected to 3.6bar).
Lastly for the lower 4 cases at 5.5bar fuel rail pressure (corrected to 5.2bar).....
e) You can get away with retaining the stock injectors but you'd need to boost the fuel rail pressure to 5.5bar to get the need flow out of them.

BOTTOM LINE
-Get the WalbroGSL392 & new filter /w internal 3.9FPR
-Get the Bosch 0280158117 injectors
-Get a tune
That's the way I'm heading.....

Note1: Changing injectors does have some complexity with the adaptive nature of the ECU's closed loop tune and a retune would be recommended. Some have reported LTFT's correcting after an injector change (eg: Tunaglove) - but I'm not sure this will help during WOT.

Note2: Woody mentioned a "climbing" pressure regulator which is connected to the manifold pressure. He's made this available through his connections with Needswings and reportedly worthwhile. The technique is employed in the pre2000 SLK230's (here), however in our case, I'm not sure if the continually changing injector output screws with the closed loop ECU tune which is adjusting pulse width - probably not. Woody can comment further on this.

Update 09/20/2016 - I added Bosch 044 pump data to pump chart

 

A lot of racers all over the world use the Bosch 044. It is the better Walbro. Make a search on Google.

For those who live in Australia :

? Brand New Bosch 044 Racing External Fuel Pump 0580254044 E85 Race Genuine | eBay

Flow chart

http://i241.photobucket.com/albums/f...flowchart1.jpg

Good thing: you can run the 044 even on a higher fuel pressure level without a significant loss in flow. Probabely no need to change injectors. I would rather fit an external fuel pressure regulator and adapt the pressure to the desired fuel requirement.


Steven

Berlin Germany

 

thank u billy, thanks steven , for that post,i have 100k miles on and changing fuel filter at time,car systems in perfect condition. maby i try with stock pump injectors and see afr on dyno? no one have sucess at stock fueling? i just dont want retune my car, many of you report about rich afr after changing injectors..

 

No2Fast
- Popular pump and seems slightly more efficient than the Walbro - ie: pulls similar amps but produces more flow (at nominal volts of 12V). This is sometimes an indication of better engineering.
However - the extra flow is not needed here unless someone is thinking of more psi.....;>)

I've added data to pump chart in previous post.

Note: There are 2 versions of this - a high perf. and the std. one which I've quoted.

 

Hi all ,very interesting informative thread good stuff

Here is my roadsters last 2 dyno results
my Dashcommand reports 20psi at 6150rpm so hopefully of interest.

Dynolog blue lines are with the stock pump, mods and eurocharge tune , it went lean .

Better is the second go round in red, now with a Pierberg 55amg pump , it good for 340lph. plus a rear cat/h pipe delete and Fat X pipe in place .

I think the figures a bit low for the mods it has but i am assured this is normal on the Mainline dynos , they tend to be 15% less the other dynos and that would make sense given the figures.
Anyway, car Goes like cut snake !

i will see if Eurocharge can squeeze a bit more out with a touchup tune

Not sure if i want or need injectors and a stacked sc yet .
a wavetrak diff i Do need!

any comments welcome

dave

 

The AFR's much better....

You dont mention what your pulley setup is.
How are you getting 20psi if you arent already stacked?
A 65mm will only give you 17.5 and a 62mm maybe 18+ a nudge.

Also the Nm seem way too high.
Stock they do 450Nm at the crank let alone at the "Torque Rear" which I presume means the rear wheels.

I'm guessing by the mBars this is at Sea Level.

 

Pulley is a 178 as per my sig.
yes sea level or close (Lismore NSW)
torque yes it was at the wheels Its too good ?

edit: i just spoke with the dyno operator re the torque figure. he said both pulls were in 3rd gear.

 

Sorry missed it some how...- just to confirm - 178 ASP + a 65mm SC pulley?
Your 178 - is it like this one...?

 

Standard sc pulley+ 178mm crank pulley

Yes it is the same as the 178mm cp in your link

I do have a spare stock sc pulley that i may get shaved a couple of mil. :-)

re my 20psi reading ,it was via the obd on dashcommand so may not be exact.
I know Les says he has seen 19psi at sea level with just the 178 crank, so its close.

 

Yes - the reason why I question it is see BB's dyno here.

These are the numbers I'm more familiar with.