How is injector timing calculated?

[DSteck]

Not much to explain. You need to convert a length of time into degrees of rotation.

[HRD]

Not much to explain. You need to convert a length of time into degrees of rotation.

That's the easy part.
I guess what I'm asking is are you timing the injector based on the start time and evc or end time and ivc.
I'm thnking I need to end injection x degrees before the intake valve closes to allow time for the fuel to travel from the injector through the valve. I realize that x is going to be a function of port velocity, distance from injector to valve, and engine speed. But, I'm not sure if I should push it all the way to the last possible ms that fuel can enter the valve.

[DSteck]

I based it off of exhaust valve close. You have plenty of time to inject it all. Just don't change the boundary if you're concerned.

[Blingole]

My head hurts thinking about this.

[carlrx7]

Already did.

http://www.hptuners.com/forum/showthread.php?t=37532

Without the exact cam events, it's guessing for sure.

lets see that voodoo excel magic do some work!

[IDRIVEAG8GT]

I'm actually pretty damn happy. Recently towards the end of this semester in my technical math seminar for college, we got into some trig that was perfect for this, so I'm not completely lost now. Glad this thread got started, hopefully you guys don't mind if I partake.

[HRD]

Steck,
So it looks like you are determining you want the start of injection to be just after the EVC then backing out EOIT using pulse width converted to degrees of crank rotation. If that's the case, what pulse width are you choosing for the calculation? Because we know that varies with load, rpm, etc... Not to mention the same pulse width takes more degrees of rotation with increase in speed. ie. 5 msec @ 1000rpm is 30 degrees and @ 2000 is 60 deg.

Here is my thinking and someone let me know if you disagree. I'm thinking I should try to inject fuel after exh valve closing and before intake valve closing. However with a long duration cam there will be reversion toward the end of the intake event at low speeds and low map, especially abdc when the piston starts coming back up and the intake valve is still open. Probably not a good idea to spray fuel at the charge when it's pushing back out of the int valve so I set my Boundary at BDC intake or 540 degrees. Then use the adder tables to back up from there. How much? I'm still trying to decide. I am also still trying to find a good explanation of makeup pulses and if I need to allow for them.

Here's a quicky excel sheet with the conversion from msec to crank degrees.

[HRD]

Well I tried three different EOIT yesterday all while watching O2's with a wideband in open loop. Test 1. Stock injector timing. Test 2. EOIT just before BDC intake stroke. Test 3. Starting injection just after EVC.
Honestly they all looked the same on the O2's and the engine didn't seem to care.

[DSteck]

Smell is where you notice it the most. They tend to feel smoother idling too. That's just been my experience. Most people probably won't notice.

[blkscooby]

I think I finally have mine dialed in. I will have to load up my spreadsheet that I used but my latest EOIT is just past BDC and the injectors should always fire after the EVC except at high RPM when IPW is at its greatest. Seems to have helped my MPG about 2 points at idle and in town.

[Kyne]

DSteck, Where would you get your pulse width number to work with? I can figure out how many degrees a msec is at each RPM (y=0.006x) but not how many msec is needed at each RPM. Would it not change with different sized injectors? Or do you just log that? Right now I'm working on making an injector timing calculator rather than doing calc HW.

I can see how large the window to inject it is, even on a decent size cam Im looking at which EVC at 370* so 150* of window. At what RPM does it start to not matter?

[DSteck]

I get pulse width from the scanner and manually add the voltage offset and short pulse adder.

I think you're missing some structure in your equation to convert pulse width to crank rotation.

[Kyne]

I get pulse width from the scanner and manually add the voltage offset and short pulse adder.

I think you're missing some structure in your equation to convert pulse width to crank rotation.

Ok that makes sense, I figured you had some way of figuring it out regardless of injector used.

and for the X i meant the two variables, RPM*msec so degreesRotation = .006*RPM*msec. Using HRD's numbers 5*1000*.006=30, 5*2000*.006=60

ie. 5 msec @ 1000rpm is 30 degrees and @ 2000 is 60 deg.

[HRD]

Does anyone really understand "Makeup Mode" and "Makeup Pulse" and should we be accounting for these in our EOIT calcs?

[carlrx7]

im still waiting for dave to PM me the numbers i should use. now thats thinking smarter not harder! until then, ill stick with 32.5 at idle

[Kyne]

1. Boundary - ECT - RPM

2. 0* is TDC between compression and combustion.

Am I retarded? I keep coming up with a high number for 0 rpm and the numbers get smaller as RPMs increase

Right now I'm looking at boundary -ECT -RPM -EVC(of 720) -PW*

so at 0RPMs PW would be 0, 520 -110 -370 -0 =40, the first 3 stay the same so as RPMs increase the answer gets smaller.

[DSteck]

Ok that makes sense, I figured you had some way of figuring it out regardless of injector used.

and for the X i meant the two variables, RPM*msec so degreesRotation = .006*RPM*msec. Using HRD's numbers 5*1000*.006=30, 5*2000*.006=60

Ah, yea, I was going to say you're missing a variable.

im still waiting for dave to PM me the numbers i should use. now thats thinking smarter not harder! until then, ill stick with 32.5 at idle

I'M NOT YOUR MONKEY!

Am I retarded? I keep coming up with a high number for 0 rpm and the numbers get smaller as RPMs increase

Right now I'm looking at boundary -ECT -RPM -EVC(of 720) -PW*

so at 0RPMs PW would be 0, 520 -110 -370 -0 =40, the first 3 stay the same so as RPMs increase the answer gets smaller.

I don't know whether or not you're retarded. I'm not a doctor.

Don't even bother with 0rpm. If you're hovering around 0rpm, then your tune sucks. I use the same value for EOIT at idle speed and everything underneath.

[Kyne]

Ah, yea, I was going to say you're missing a variable.

I don't know whether or not you're retarded. I'm not a doctor.

Don't even bother with 0rpm. If you're hovering around 0rpm, then your tune sucks. I use the same value for EOIT at idle speed and everything underneath.

I'm doing a Monaro swap on my GTO so it's at my body shop for a while and I don't have a car to check PW on so I was dummy checking my math on the spread sheet, since at 0 the PW will be 0 as well. Plus I like my idle rough so I get the RPMs low

Also thanks for the help this far.

[carlrx7]

I'M NOT YOUR MONKEY!

DANCE FOR ME PUPPETS!! oh ok, send me the excel and ill type the numbers in myself. lol

[DSteck]

Go fish.


And by fish, I mean fist yourself.