Power commander Wiring+ race mode

[ducati]

So.... I have new bosch 431 injectors,[350cc@43.5psi] a PC3usb, fuel pressure at 40psi, race mode enabled, resistor bridge between PC and OEM computer, set the throttle % in the pc to run slightly below atmospheric at idle, and adjusted the TPS to give me a reasonable idle.
810 wisecos, HT12 turbo, single pipe to small muffler.
I have tried to sort this myself [without a dyno run.....],by using the engine temp sensor feed, connected to a pot, so I can lean/richen the mix on the fly, and learn where to alter the map.I managed to get a fair tune, enough to run on the race track wide open,[ 36psi fuel pressure at the time] and no pinging.
The topend seems weaker,[too rich?] but the midrange is/was much improved. I KNOW I should get it to a dyno, but in Darwin there is no-one I trust to do the job properly, so I'm sorta stuck with a self tune situation.
With race mode enabled you get 20% more fuel over the entire range.....right?? So the PC map must be in the negative to allow for the larger injectors, plus consideration for racemode.
Should I put a resistor to the brown wire, or just leave it disconnected, and alter the PC to suit? My memory of race mode is that it does not cut fuel on the over run, yet I am getting serious backfires, never had this pre PC.
As it is, I am having trouble getting consistancy from the fueling. One day it's nearly perfect, the next day the damned thing won't even idle, and seems stupidly rich? to the point it misfires above six, and surges badly off boost. My fuel pump is good, fuel filter clean.
I have now gone with a minus 10 map over the entire range, zeroed the PC buttons, and set the tps to get some kind of idle happening to learn what is going on. It runs okay, but still backfires bigtime on the over run, which suggests to me it is lean??
To my thinking, there is only the 0% column to adjust the off boost fuel settings, yes?
Help!!

[Lorcan]

The topend seems weaker,[too rich?] but the midrange is/was much improved. I KNOW I should get it to a dyno, but in Darwin there is no-one I trust to do the job properly, so I'm sorta stuck with a self tune situation.

If you're not going to get it mapped on a dyno you seriously need to get a wideband lambda gauge like a Wideband Commander. You are going to be chasing your tail forever mapping it based on what it feels like - you need DATA!

With race mode enabled you get 20% more fuel over the entire range.....right??

No. No-one knows exactly what the fuelling changes are, but to give yourself a baseline reset the TPS to the stock position, reset fuel pressure to stock (as fuel pressure rises give diminishing returns), and get rid of any race mode resistors - you don't need them any more.

So the PC map must be in the negative to allow for the larger injectors, plus consideration for racemode.
Should I put a resistor to the brown wire, or just leave it disconnected, and alter the PC to suit? My memory of race mode is that it does not cut fuel on the over run, yet I am getting serious backfires, never had this pre PC.

Yes the PC map will start in the negative, probably around 30-40% neg at low/zero boost rising up to zero or single digit numbers at 30psi (if you ever go that far). Race mode does cut the fuel on the overrun - listen to my dyno video!

I have now gone with a minus 10 map over the entire range, zeroed the PC buttons, and set the tps to get some kind of idle happening to learn what is going on. It runs okay, but still backfires bigtime on the over run, which suggests to me it is lean??

A single number right across the map is no map at all, it will be bloody awful like that. Start with one of my maps (or one of the other posted ones) - that should get you in the ballpark, then use across the map +/- percentage figures to get it closer for your size injectors, then finally map individual cells.

To my thinking, there is only the 0% column to adjust the off boost fuel settings, yes?

Correct, assuming you have the PC connected to the pink boost wire, not the TPS.

[Lorcan]

A bit more of an explanation about fuel pressure, and why you should stick with stock fuel pressure (36psi) IF you want to start off with one of my maps.

Firstly, it gives the fuel pump an easier time. Running higher fuel pressure is great for atomization at the injectors - F1 cars run 250psi+ - but the poor old pump will struggle if you dial 45psi in then add 30psi boost, compared to stock that's a total of 75psi (45+30) instead of 45 (36+9)! And as flow from a pump decreases with increased pressure (like putting your thumb over the end of a hosepipe) you will soon run out of flow.

Secondly, it buggers the map up. It's easier if you start thinking in absolute pressure, rather than gauge pressure, to understand this. 0psi absolute is like it is in space - no air pressure at all. Here on earth we are used to seeing tyre pressure gauges and the like reading 0psi, but actually air pressure here is 14.7psi (roughly), it's just that we set our gauges to read zero. So 0psi gauge pressure is actually 14.7psi absolute pressure.

Now then, stock fuel pressure is 36psi (gauge). If you raise your fuel pressure to 43psi (gauge) that's an increase of 20%. However, what you've actually done is raise the absolute pressure from 50psi to 57psi, an increase of just 14%.

And it gets worse.

Because fuel flow is NOT proportional to pressure. In fact you have to square the pressure to double the flow. So the more you increase the baseline fuel pressure, and then alter the numbers across the map to compensate, the more wrong the map will be as you increase the boost. So you'll end up building a whole new map to allow for the diminishing returns increased fuel pressure gives.

Good luck with that, especially if you don't have access to a dyno

[ducati]

You've answered a lot of questions that make the whole deal a lot clearer.........

I had it running fairly well with a -10 @ 1250/0% to to +10 @9000 18ish psi/60%, 36psi fuel, map on the track, but the top end was missing, it sounds as though I need to reduce the fuel flow over all.
I will reset the fuel to 36psi, and stay there.......
The racemode brown wire will remain disconnected....

I have your maps , and others here,[ thanks for that], I will try them.
My injectors are rated 350cc @43.5, so running them at 36 rates them lower?, at 290cc, so they aren't really much larger than stockers.............correct?
Hence running 40psi.......320cc, that was the thinking anyway.

I went to a virtual zero map to start again, and have no influence on the original OEM, except -10% to allow for the 'slightly larger injectors'.

Thanks Lorc that's great info

[Lorcan]

If I remember rightly the stock injectors are around 270cc at 43psi, and 230cc at 36psi, so your 350s are around 30% bigger than stock. It's not a direct comparison though, as high impedance "saturated" injectors have different circuitry driving them to the old low impedance "peak and hold" injectors, so may (or may not) take more time to open and close. The period when the injector is being told to open (and how fast) but isn't actually open yet is known as dead time, and when you are talking milliseconds it can have quite a dramatic effect on the performance of an injector. It's also affected by fuel pressure...

Don't guess though - get a wideband lambda on there and see what's really going on :rockbanana

[Würstchens-Turbo 810]

Aaaahhh
Hey Duc .

Thats perfect , you use exact the same Injectors like me .

If you have a map for this Injectors please inform me , so i have a really good starting point

Cheers Horst