Here is (yet another) spreadsheet I was working on a few nights ago but forgot to post...

I guess the question here is should SOI be adjusted to compensate for Rail Pressure adjustment?



Sheet 1: Standard Values (for reference)
Sheet 2: Tuned rail pressure, the difference in injection times with tuned rp from standard, the time difference in degrees (rough)
Sheet 3: Ignore this for now.. it is just SOI before and what the SOI would be with the time difference in degrees applied.

This makes sense but I have never seen a tune file or reference on the internet of the timing being retarded... so that is why I begin to think that somehow this is wrong. I would just like to know why this is wrong.

Thoughts...? :wtf:

Trying to read this in open office... filled with bad data that use references.
Evidently openoffice dont support interpolate function :(

So no comment :lol:

I was thinking about soi the other day to.
If you increase rail pressure you also increase fuel temp.
If you increase fuel temp...you reduce flow at the same pressure.
So is scaling duration by rail pressure the correct way to do this without considering fuel temp ?

Might make next to no major difference on density...just throwing it out there.

Ill copy your idea and upload a PDF too... So people can see the result of the formulas at least...



My GUESS would be that temperature does not affect flow rate enough to matter, as surely if it did, there would be another calibration map for adjusting the injection duration depending on the fuel temperature.

The only reason I think rail pressure makes a difference to SOI is that according to these (admittidly rough) calculations the injection duration could be upto 4 degrees shorter on high IQ high RPM requests just by increasing rp to 1400 bar from 1350... and 4 degrees shorter duration is a lot of advance.

Again please ignore page 3 - this is not finished yet.. !

I dont disagree...increasing rail pressure increases flow for the same duration....so the EOI will/should be earlier.
Only way yo keep the same EOI is to inject later and closer to TDC.

Carry on :D :lol:

Before I carry on I need to know why no other tuners seem to compensate for this ;) I don't want my car to turn into a mobile firework dispaly lol

Because from what I have seen on other forums ..."dont touch soi"

Evidently oem normally is conservative with soi and wont advance a much as necessary for best power.....more for economy and noise or emmissions.
So when the rail pressure is increased it actually make the soi more accurate according to some.

Take the egr for instance.
Soi has to be earlier with EGR on as its more difficult to burn and takes longer.
Switch it off and the SOI is too early...but if it was conservative anyway...its probable more accurate with regard best power.

Personally I wouldnt touch SOI without a dyno....unless it was maybe smoothing some rough areas.
Set soi to give peak power.....and then retard 2 degrees later or so.

I agree that a dyno with this is preferable otherwise your going at it blind.

I also know that there needs to be an advance to work better when emissions are not considered. I guess I was going to try and and advance the timing a couple of degrees on high IQ requests and a degree at low IQ, then factor in rail pressure.

Tuned SOI = Standard SOI + 1 or 2 degrees - Rail Pressure Difference (in degrees),

At high IQ/RPM requests this would retard SOI a bit and advance it in other areas...

Another option, is just dont adjust rail pressure ;) it would be a shame though as this has benefits

Definitely has benefits...definitely better...just wont be optimum without a dyno.
You'll no doubt delete EGR and that anyway....so probably best just working from the pressure change as you said originally.
Better that then advance too far beyond MBT and braking the piston instead of accerelating it.

Bit disappionted the mods had no comment on this.

Could I just ask directly to the mods: Has this affect been considered in the maps that you do for people? I would just like to know that it is not something that has been overlooked before say I payed £X00 for a map?

rlees85 wrote:Bit disappionted the mods had no comment on this.

Could I just ask directly to the mods: Has this affect been considered in the maps that you do for people? I would just like to know that it is not something that has been overlooked before say I payed £X00 for a map?

rlees85, i hope i will explain you well and you will take it right way.

We saw all of your posts, here and on the other forums, you would be very disappointed when you would decrease SOI,
but we assume that you did not test nothing at all,
figured out based on your last question & comment or comments based on turbo knowledge on other forums...

You have to be aware that you will inject more fuel than stock (without fuel no power),
how do you think the nozzles will inject that kind amount of fuel in same time?

You increase Rail pressure to get also advantage in duration but duration still has to be higher at higher IQ (to inject all that fuel - this does not mean you have to increase duration, you have to recalculate it for different IQ and change axis!)
and also SOI has to be +, not - :crazy: , considering also you do not change axsis on SOI (70 is last column) and leave it stock -axis.

Your affects +- few microseconds are irrelevant, you did not take to consideration other changes.

If you remember we took a look at your mods on your ECU also made some comment to you if i remember well.
Your progress was good, but you have more important things to learn in comparison of the impact you are talking about.

You really have to do some practise job, this is not only a theory job,
you really have to know how the car reacts after your calculations and modifications.

When you make 300+ flashes in practise you will know what we are talking about, theory is one thing practise is another,
but it goes together theory + practise.

If you want mild tune, ECO version that car has very good consumption and no power, than your theory could work and soi go to - ...but you want more power not less.

But if you think your theory is right, make test bin and try to drive it :)