QUOTE(TitanRev @ Mar 17 2015, 01:07 PM)
I don't feel any lag in my throttle respond. Step..Go...Step..Go..
Your fuel pressure is regulated by the Fuel Pressure Regulator (FPR), on stock car the stock FPR controls the pressure via a spring attached to a diaphragm not the ECU. ECU only monitors the fuel flow rate and pressure then adjust the PD (Pulse Duration) of injector to control how long the nozzle to stay open and the PD reduces as engine RPM increase. For Borsch injector they are reliable up to 85% of their duty cycle anymore and they will start to fail.
By now you should understand how the injector works and how it is controlled. So you ask will the EU compensate the higher flow rate. The ECU will only control the PD of the injector. Your fuel flow rate will increase once you swap to a high pressure high flow FP. The FPR will detect the higher pressure due to higher flow and regulate it. But due to the higher flow rate even with the FPR trying to bring down the pressure to stock set level. Technically speaking your fuel delivery /hr is still higher than stock pump hence your whole fuel line is has a higher pressure than stock.
The ECU has it's own fuel mapping but it will change slightly to match with the increased fuel but to an extend only. As I have not fully let the Walbro run at higher efficiency so the stock mapping still an coupe with the changes but from my usage I've noticed Fuel Consumption has increased.
Why I change to a high flow fuel pump is because on dyno my AFR is showing leaning issues at Mid to High rev range and overall the AFR is on the lean side starting from low. As I'm preparing to redo my entire fuel delivery system (returnless to return type) I drop in the Fuel Pump 1st then later on will put in an adjustable FPR to regulate and increased the fuel pressure where the stock FPR will not be able to handle anymore.
I drop in the Fuel Pump as a testing actually wanted to see how a high flow FP whether will help to reduce the leaning issue to a certain level and it did. My Mid to high rev now is much stronger compare to before where I can feel the engine starving for fuel. The stock FP was not able to deliver quick enough to supply the engine needs hence on dyno the graph shows a constant ----- only instead of keep going upwards until the fuel cut off kicks in.
Since not much info have gone into detail of the problem, I took things to my own and use my own car as a test bed. I've tried using a SR20 fuel rail but it was not a fit. injector outlet was off by few MM and with the stock pump it will not able to supply enough pressure at all to the larger fuel rail so with now the increased pressure. I'm dropping in bigger fuel rails and see what happens.
Throttle lag for mine would be sometimes when starting in 1st gear, has to be slightly earlier press on throttle, if not sluggish. Sometimes on double clutching on rev-match I do experience throttle opened not big enough though my step on throttle is a lot, it came to a point where I now consider on electronic throttle controller to maybe up the sensitivity of the throttle.
Maybe going for dyno would see some figures, do report on any improvements. I believe after some time the ECU would recompensate on your higher fuel pressure, hopefully would give a positive outcome, ultimately the best would still be a modified ecu eh?
When going for next dyno? Feel wana join, hopefully on a Saturdeh so that I want to know how is my own gaga feel, in numbers; readable and compatible.