Tuning,

-Drive the car in stock form and log the oxygen and fuel trim under heavy loads in a higher gear. Take your time and compare logs making note of weather and temp. Keep good track of your logs to compare with fuel trim as you increase boost.

-Raise or disable the map sensors over boost limit to prevent limp mode from increasing the boost.

-Gradually increase boost and start logging O2 and fuel trim to compare to stock

-Keep an eye on your O2 and fuel trim as you increase boost. If fuel trim goes reasonably out of stock range, increase fuel pressure (find out highest pressure stock injectors can safely handle). Add adjustable regulator or higher output pump or both?

-As trim goes back to stock range by upping fuel pressure, gradually go higher with boost until trim moves reasonably out of stock range again.

-Start editing fuel maps in effort to bring trim back to stock range when you get trim back under control, try to increase boost…

-Repeat until you can no longer bring trim under control. At this point, bigger injectors are needed....

-Back off boost to a safe range for the stock injectors....

-Test minor ignition tweaking, could show improvements….

-If you modify something, always verify fuel trim did not go reasonably out of range.

-If boost will no longer increase, go larger with turbo by selecting a turbo with a compressor map that better matches modifications.

I think  the assumption is you'd accompany the increase in pressure with an increase in KRKTE.

What happens is the trim is increasing because it is asking for more fuel but it is not getting enough fuel based on the stock fuel pressure and curve.

So if you up the pressure, when the trim asks for more fuel, the injectors will be able to deliver more fuel.

Think of it like you have a characterized fuel curve, it is a perfect day and perfect air/fuel mix for a specific air density on that perfect day (like jetting a carburetor).

Now your trim is controlled by the oxygen transmitter and it sees that the following day it is cold and rainy so we need more fuel at certain points of the fuel curve. The trim then tells the injector to spray more or less as needed.

Now there is also load calculation and that is the equivalent of an accelerator pump on a carburetor. It looks at throttle position verses acceleration and adds fuel. It adds much more fuel than fuel trim is capable of delivering.

The key to all of this is fuel trim. Watch the numbers and if you see it going out of a reasonable range in either direction, you are tuning the car wrong.

This is real basic stuff....

This isn't a hack if you tell the ECU the new flow rate. I'm pretty sure rayce isn't suggesting just changing the FPR in isolation. That would be daft.

You would think so wouldn't you? But...

A chap on the previous forum I was a member of (who is not particularly daft) likes to add every possible modification to his car he can afford without thinking through the consequences or getting his map changed. He uprated his fuel pressure regulator to a 4 bar from the stock 3 bar to 'cure' some enleanment issues he was having. However, he did not request the tuner to alter KRKTE to match the increased fuelling. I think he was also still running stock injectors.

Unsurprisingly he then started reporting rough idle because he had effectively increased his fuelling across the board without the ECU knowing about it. When challenged, his response was along the lines of "I'll live with it because rich is better than lean".

Maybe he has finally got a recalibration to his initial recalibration to take account of all the physical modifications he did...

Doug

If you talking about increasing the fueling, then yes either dialing up fuel pressure is an option (to a point).

But your OP is going at it wrong IMO...

If you're going to be operating outside of what your base injectors size and base FP setting can handle, why not just set the base pressure higher in the first place and remap the ECU properly?  IE, change base FP from 3 BAR to 4, 4.5 or 5 BAR (if your fuel system can handle it), and then remap.

turning up the fuel pressure bit by bit and then making ECU changes only to mess with the FP again and starting the cycle over again is not making any sense to me.