Injection Timing Assistance Requested

[barum]

I am to blame for the FRC formula, so maybe a little explanation is in place.

Calculation consists of two main components:

1) calculating the average air flow speed in the intake channel based on
- average intake channel cross section
- cylinder volume
- mean piston speed at given rpm, since the air flow has momentum and peak piston speed is not representative over the injection duration

2) calculating the fuel spray flow speed based on
- Bernoulli speed
- discharge coefficient

These two speeds are summed up to be able to get the time fuel takes to reach the combustion chamber while knowing the length of the intake channel (from the injector to the combustion chamber).

[barum]

Thanks. Your input makes sense to me. Any idea why the RPM table stops at around 4900 rpm?

You're welcome.

I guess it stops there because over that rpm you're typically in PE/WOT or DFCO (which can be neglected for obvious reasons) modes leading to pulse widths which will be longer than the window the intake valve is open.

Things don't change that much from there on, so what ever works at that point will work at higher rpm, too.

[07GTS]

hmmm goes nice now... bigger exhaust and changed gap on plugs now it likes being delayed more then before as its mentioned in the spreadsheet for PD blowers i just set it up like that, one thing i have noticed is the iat seems a little higher then usual (compared to ambient at cruise) can this be a side affect of a delayed injection..? on E85

[GHuggins]

IVT may go up a little, but IAT'S should be the same.

[07GTS]

maby im getting close to the lower iat limit from having the iat sensor in the manifold as the ambient gets toward winter temps might keep an eye on it

[07GTS]

can the EOIT in spreadsheet be double checked on the table view the EOIT (end of injection target) row seems like the make up isnt added to it..? at 1024 rpm my boundary 531 - ect 90 - makeup 30 = 411 but the spreadsheet says =441 its missing the 30 deg makeup advance..? this is on spreadsheet v19

[GHuggins]

Yes, Makeup is only changing SOI for some reason and not EOI?

[scottt28]

I've corrected the formula in version 20.0 of the tool. See attached. Comments welcome

[07GTS]

Yes, Makeup is only changing SOI for some reason and not EOI?

yes should add to soi as an advance like the ect table does

[07GTS]

Make-up should be added to boundary. I've corrected the formula in version 20.0 of the tool. See attached

looks like its gone the other way now added instead of minus, my calc has gone from 441 to 471 instead if 411 or is there something alse at play here ?

[scottt28]

hang on... i see a couple other issues

[07GTS]

please download again and try again

yep that looks good, thanks

[schpenxel]

Can someone explain the whole makeup thing to me super quick? Is it always used or only after a certain point or..?

I thought it was only if it couldn't get the Inj PW inside of whatever window, but otherwise was ignored. The way the sheet is setup now it seems to be using it all the time

Or maybe I don't understand it, I'm doing some reading now

[scottt28]

Two formula corrected

[07GTS]

Can someone explain the whole makeup thing to me super quick? Is it always used or only after a certain point or..?

I thought it was only if it couldn't get the Inj PW inside of whatever window, but otherwise was ignored. The way the sheet is setup now it seems to be using it all the time

Or maybe I don't understand it, I'm doing some reading now

i found it in use all the time as far as i can see kinda like extra deg if needed, just at idle that 30 deg has to be added in mine to get the fuel to stop going out the exhaust if i dont add it then the stock eoit settings added up should be enough to stop fuel out exhaust but they arnt until i noticed the 30 more i needed to delay it must be the 30 in the makeup advancing it further.

ill add i have lowered it from 30 to 20 was ok then 20 to 10 and it didnt like that i started to see strange spikes on the WB so went back to 30 and good again and that was just low duty operation, also im in CL all the time and it still affected it i was thinking it was related to the fuel trims which update all the time may need the extra deg but wasnt the case still not 100% sure on its actual use

[schpenxel]

i found it in use all the time as far as i can see kinda like extra deg if needed, just at idle that 30 deg has to be added in mine to get the fuel to stop going out the exhaust if i dont add it then the stock eoit settings added up should be enough to stop fuel out exhaust but they arnt until i noticed the 30 more i needed to delay it must be the 30 in the makeup advancing it further.

ill add i have lowered it from 30 to 20 was ok then 20 to 10 and it didnt like that i started to see strange spikes on the WB so went back to 30 and good again and that was just low duty operation, also im in CL all the time and it still affected it i was thinking it was related to the fuel trims which update all the time may need the extra deg but wasnt the case still not 100% sure on its actual use

Okay, thanks

I looked around some more and saw a "makeup pulse minimum" table in that same section, so I'm working on the assumption that when inj PW is over the values in this table then the makeup stuff is added in. Mine came set to 0.250 msec so that makes it pretty much in play all the time, assuming I'm understanding it correctly.

edit: reading the descriptions again it almost seems like the Makeup pulse min is saying if the pulsewidth is x beyond what can fit inside the standard window, THEN change the boundary by x degrees, but I don't really have any way of knowing which is actually right. Guess I could 0 it out and see what happens

[07GTS]

hmmm so could be a relation between makeup pulses and for example the missfire recording system where it knows the time when each cylinder should fire but with a cam that varies at idle so the makeup may be used a bit more if it needs to fit it in, not sure just throwing it out there... then there is the makeup pulses single, multiple or none..? mine is on multiple standard i may try single when i can next get the car out, my makeup pulse min is .3 stock i have it on .1 at the moment i was thinking the bigger injectors i should allow a smaller PW

[JDV]

At fear of sounding dumb I'm going to ask anyhow , can you explain how to find injector distance ,spray speed , Would like to try this on my gto used dstecks year or so ago but cam then only had 1 degree over lap . Is there anyone willing to explain how to use this sheet more clearly to me like eoit for dummies? I understand the theory an concepts to a point just don't know where to get some of my inputs. I understand pulling tables from stock tune pasting in inputs an getting the pulse width while at full throttle 1:1 should I lock convertor when getting this also ? adding this to short pulse , well bringing over table and pasting in ... Sorry if this sounds confusing to read but I am confused .

I added my current tune a log but doesn't have a 1:1 pull and my cam sheet from new cam

Scott28, Ed Mowton ,Schpenxel maybe some help on this ?

[GHuggins]

https://www.hptuners.com/forum/showt...for-help/page2


Better to lock converter and get more consistent and precise pw info...

[GHuggins]

The above ^^^ is what this spreadsheet originated from