Quote:
Originally Posted by splinter
Yep. I understand about adding a return line. Unless one does away with the OE filter on the supply side, the fuel rail will still only reach its regulated maximum pressure.

Perhaps there’s more to this modification than has yet been shared…

Fuel pressure can be regulated after or before the rail. Look at it this way.... Fuel, like air, is lazy. It will travel the path of least resistance. Most vehicle adjust post rail if a return system, where as returnless system use fuel pump modulation on a diaphragm type filter to change pressure. Im just 100% sure what out system is from the factory. Obviously if its a return system its easier to modify.

I think Splinter is on it. We have a return line, it is located on the filter/regulator. next to the fuel pump. the change would have to occur there.

 

Ok thanks for the heads up. Im sure something can be done, Ill play around next weekend. I have the fuel rail adapters to put a fuel pressure gauge on the rail. May be a long process to develop a returnline but I will do it.

 

My next post was to question the church, the 2005 SRT does not have a return line and I believe the rest are the same.

THe regulator fitting is just a vent hose and a boost signal can be added there , I have tested up to 20 PSIG.

Woody Enjoy

 

Woody for President!

 

Not to start an argument, But the 2005 SRT manual clearly states that there is a return line from the regulator to the tank, to maintain correct fuel system psi.

I have not looked at the system on the car. it is possible the manual could be wrong

 

This is why I posted the "Question the church", Woody

 

Oh really?? I will have to try this.

 

If it works without issue. Fabulous

 

So the ECU doesn't operate in closed-loop mode using the O2 sensor at WOT? If it were, the O2 sensor readings would compensate for any rich/lean condition and adjust fuel trims accordingly.

 

TRUE.

I have found that the stock fuel map is too rich for WOT operation, I am at 11.7. I am going to reduce the fuel pressure so that the Zietronic data logger can indicate when to add in additional fuel to keep the A/F in a good range.
I was too rich and then too lean (IN WOT operation), To work my scheme needs to be on one side of the lean/rich chart and have a control correct toward the normal '12.5 for power' setting.

Been too cold and busy...Woody

 

Tom,

My engineering skills are nowhere near as advanced as Woody's, but let me see if I can decipher into a 'for dummies' version, as you put it.




So here we have a small graph... The Y-axis is the Air/Fuel Ratio (A/F) and the X-Axis is Boost. Now the bottom left corner of the graph is "0" and the values increase as you move outwards along both axes (NOTE: sorry about the green dot, should be on the y-axis representing 0psig boost)

Moving on. The black line is the current results of the a/f ratio as boost is increased towards woody's 20psig. As boost increases the a/f ratio decreases because the fuel delivered to the engine is basically the same (non-linear increase in relation to boost across the entire spectrum) at all times. This is not necessarily good as when higher boost is reached there is not enough fuel in the engine for proper combustion.

The red line represents Woody's current situation (correct me if I'm wrong Woody). With the addition of his FPR (fuel pressure regulator) he has helped to increase the A/F ratio average across all boost. Now as Woody stated he still sees a lower A/F ratio at full boost then he would like to see. So this is the cause for the drop off at full boost (however, the actual A/F loss may come at some other point in the boost curve)

The blue line is the ideal A/F ratio across the entire boost curve...This is what he Woody is ultimately striving for to maintain peak engine performance and fuel delivery at all times....

Looking back that may not have been 'for dummies' enough....




Basically, you want an A/F ratio with little variation at all amounts of boost. This is what woody is working for.

 

Pretty much correct.

From Idle to 17 PSIG boost I am rich, I need to pull back on the fuel rail pressure so that I could lean there also

Now I will be lean everywhere. THe car fuel air ratio I ment.

Now with the controller "man-ing the rudder" the WOT will be sensed with the Zietronics data logger, and if it is lean, a control will increase the pressure signal to the fuel pressure regulator. THe FPR will increase the fuel pressure causing more fuel thru the injector and reducing the lean condition up to the alarm 'setpoint'. I should be able to control the setpoint and have the data logger drive the fuel rail pressure to give me what I want say 12.5.

I know that the s/c boost will just overdo the fuel mixture as I was 17:1 before I added the boost signal to the FPR. After the hose was added, the F/A readings fell to about 10.7 to 1 !!!!!!!!!!!!!!!!!!!!!!!!! That is way way rich, meaning I can go from lean to rich just by adding a CONTROLLED boost signal to the factory fuel pressure regulator (FPR). BTW the book is wrong as there is no return hose from the fuel system rail, everything is done inside and at the fpr under the passenger seat area. Inside that big plastic cover just front of the axle on the passenger side.

As the computer used to say "WORKING" , more soon.

Woody

 

http://store.summitracing.com/partde...?part=msd-2350

 

Thanks GDC-SRT and Zahanama for the explanations. I got lost in the talk of fuel rails and such.

I have another question, which may be obvious, but obviously not to me. I've seen A/F graphs other people have posted that were rather flat and at the ideal A/F ratio across the RPM spectrum. I believe this was achieved with an ECU tune - no parts required.

So, my question is: why go to all the trouble of reinventing the wheel and managing a fuel pressure regulator?

Don't get me wrong, I'm just trying to understand. I'm not knocking what Woody is doing. He's a pretty amazing guy in the mad scientist sort of way.

 

How about a DC-DC voltage convertor to "step-up" the voltage to the fuel pump in response to FAR? As a practiing electrical engineer, I could probably come up with a simple design fairly easily or better yet adapt an off-the-shelf part. It seems that this approach might have a quicker response than a pneumatic-mechanical one ?