Injector Phasing Information

[Shu]

My method for determining teeth.

Note: HONDA - OBD0 - Distributed - 16 teeth

(1) Base maps should get you running then sync timing.

(2) Now set the ignition sync to 0 but reset the Ignition tooth accordingly (car should still have properly synced timing)

(3) The ignition tooth should now be TDC for one of your cylinders.  To find out which one it is, watch with a timing light while you adjust individual cylinder trim for #1.  Using this method I determined my cyl #3 was TDC at 1.8 teeth.  AEM considers #3 physical as #1 in software.

(4) now I sync the injectors.  I set injector #3 to 1.8 to sync to TDC followed by each injector in FIRING order. (NOTE AEM injector x may not be physical x; check your application notes wiring diagram).  

3  1.8
4  5.8
2  9.8
1  13.8

NOW the calculations in my spreadsheet can be used.  If you don't understand or don't use that spreadsheet DON'T change anything.

[Shu]

Having just reread through all these posts my spreadsheet may need adjusted.  I assumed (made prefect sense to me) that if injector phase was 0 then the injector would fire at the sync point.  It seems from reading this that by using my spreadsheet the injector would be firing 360 degrees early.

I'll have to adjust the spreadsheet and then test to see if the car agrees.  Unfortunately it won't be running until spring.

[Shu]

OK then. A number of 357 represents no advance and -360 representing maximum advance. I'm sure this makes sense to someone

So if I were writing a CAL file for a custom set up and put in exact injector tooth locations for inejction event from TDC, I need to put 357 in all cells in the table as a base case for injecting at specified events.

After this point, once the motor is running, I would need to determing how much advance verus RPM verus load I needed in degrees and SUBTRACT these numbers from the base of 357.

357 is maximum ADVANCE. A smaller number would fire the injector later.

[FWombat]

A missing piece of information for each application is the location of the tooth reset point right?  Maybe AEM should start publishing that information in the instruction manual for each new application.  Yes?  

I think that would be really useful.  It took me some careful examination of the tooth patterns and your description in the first post to finally figure out where things fell on my car...at least I think I got it figured out.    Knowing where the tooth points fall on each application might save people some headaches.

- Brian

[Enthalpy]

Typically, we tune the Injector Phase option to get good throttle response and idle quality and sometimes you'll see advance maps sloping upward with engine speed.

Otherwise you have to tune it by "feel" which is usually what we do.      

SA

Can I ask what might be a dumb question?  How do you tune this by "feel"?  Can you give perhaps a methodology to start out with?

[WadZii]

Can I ask what might be a dumb question?  How do you tune this by "feel"?  Can you give perhaps a methodology to start out with?

get on a load bering dyno.. hold it at a specific load point.. move injector timing till you reach max power.


for cruise and drivability where max power isnt necessacarly what you want just move a few deg, see if it leans out or drives better, etc..  sort of the same way you would tune low load ign timing on the street as well as accel fuel.. mess with it till it drives right/gets good milage

[SA]

Can I ask what might be a dumb question?  How do you tune this by "feel"?  Can you give perhaps a methodology to start out with?

That's not a dumb question.  Your engine will let you know when it's happy...especially at idle.  Just experiment with it.  While at idle, start moving the Injector Phase option around and feel how the motor reacts.  You should hit a sweet spot where the idle smooths out a little, RPM rises, manifold pressure drops, etc.  Throttle response will improve as well when you get this dialed in.

SA

[Enthalpy]

Thanks for the replies, guys!  

get on a load bering dyno.. hold it at a specific load point.. move injector timing till you reach max power.

If I'm seeing 75% duty cycle at max power, doesn't that mean injector phasing makes little, if any difference?  At really high duty cycles, the difference between batch and sequential diminishes, right??  What are your thoughts on my statement?  

That's not a dumb question. Your engine will let you know when it's happy...especially at idle. Just experiment with it. While at idle, start moving the Injector Phase option around and feel how the motor reacts. You should hit a sweet spot where the idle smooths out a little, RPM rises, manifold pressure drops, etc. Throttle response will improve as well when you get this dialed in.

Okay, so I'm going for engine smoothness and deepest vacuum at idle, much like idle ignition timing.  This makes sense to me.  

How to you take that information and start to do the drivability portion?  This is the real tricky part, right??  WadZii's method is not scientific enough (/opinion) because mileage will vary based on so many things, and it is difficult to get immediate readings.  

Lastly, what did you mean by the injector angle will "slope up with engine speed"?  Higher engine speed means faster airflow rates, which would overcome the issue of time it takes the fuel to get to the engine, right??  

Your thoughts?

[Erik88GT]

It actually depends on where your cam sync falls relative to TDC. This is best explained using an example:

If option Inject Tooth #01 = 0.00 teeth
and the Inj Adv Map = 357 degrees
and option Injector Phase = 0.00 teeth

The injector will open at the first significant crank edge following the cam sync edge. If the falling edge is your significant edge, the opening time will correspond to the first falling edge of the crank signal. The Inj Adv Map has a range of -360 degrees to +357 degrees. The smaller the value, the later the injector fires.

So on the Mustang, the table and options are how you explain above. And if I wanted to inject earlier I would start back at -360 and go up from there (since I can't go higher than 357)?

Why is the max 357 and not 360?
Would the next significant edge (for a Mustang) be 360/8= 45 degrees?
I have no clue wether it is falling or leading edge and what the tooth count reset is and can't seem to turn up any info in the search.

I'll have to play around with it tomorrow and see what numbers the motor likes. I'm assuming a linear table with RPM, but does anyone know what is a good ballpark delta advance per every 1000 rpms?

[Enthalpy]

A bump in hopes of an answer to my question.  I am really curious about this.  Do you guys sit there dividing your hp by your pulsewidth to estimate some semblance of BSFC while setting injector timing??

[WadZii]

you are right, at higher pulsewidths it dosnt really matter.

what im talking about is once you get the injector phase number set (what SA is saying to do) then you can use my methods to tune the inj advance map itself, not the injector phase option.

its not scientific.. but there isnt a whole lot about tuning a car that is. you can do all the calculations you want, but knowing exactly how the engine likes its fuel delivered isnt something a formula is gona tell you.  some engines may want all the fuel injected while the valve is open, some may want fuel sprayed on teh back of a closed valve... it all depends.

at higher rpms the air does move faster.. but the valve opens and closes faster as well.

[Enthalpy]

Make no mistake about it, you can calculate and model every last aspect of an engine, including combustion kinetics, charge stratification and intake resonance!  

When I was in college, I saw a very impressive demo at ASME that was modeling cycle-to-cycle variations.  They then compared that to lab-measured ion sensing data and it came out to be VERY close!  

However, the real-world varies enough that we can't use those calculations alone.  The real-world also varies in ways we don't measure and take into account (cylinder airflow variations, humidity, fuel temp, fuel composition and the like).  This is why tuning is required.  

I am hoping someone can give me a pretty good method so I don't have to burn the dyno time figuring out my own method.  That's all.

[SA]

If I'm seeing 75% duty cycle at max power, doesn't that mean injector phasing makes little, if any difference?  At really high duty cycles, the difference between batch and sequential diminishes, right??  What are your thoughts on my statement?

At very high duty cycles, injection timing doesn't matter.    

Okay, so I'm going for engine smoothness and deepest vacuum at idle, much like idle ignition timing.  This makes sense to me.  

How to you take that information and start to do the drivability portion?

Hard to answer that question.  It depends what you're looking for.  OEM manufacturers a looking for best economy and/or emissions just off throttle and at very light loads (where most vehicles spend 99% of their time).  They will tune injection timing to get the most efficient burn of the available fuel.  

 
Lastly, what did you mean by the injector angle will "slope up with engine speed"?  Higher engine speed means faster airflow rates, which would overcome the issue of time it takes the fuel to get to the engine, right??

As a rule of thumb, injection timing advances as engine speed increases but again...this depends on your engine...intake runner length, injector position relative to the valve, etc, etc.  

SA

[twoqik4u2]

You can calculate what the timing is theoretically going to be.  But guess what.  I did that and you still end up tuning the good old trial method.  It is easiest to just keep everything the same except the fuel timing (or in this case phase of each individual injector) and watch what happens to you afr or power on a dyno. I say spend a day at the dyno vs. many days of calculations and a half of day at the dyno.

[Enthalpy]

You can calculate what the timing is theoretically going to be. But guess what. I did that and you still end up tuning the good old trial method. It is easiest to just keep everything the same except the fuel timing (or in this case phase of each individual injector) and watch what happens to you afr or power on a dyno.

I'm not sure if you were arguing with me, but we agree.  Perhaps I wasn't clear in my first post.  Let me restate it:

I merely said modeling will get you close, but the real-world varies in too many ways, most of which are unmeasured by our EMSes to go by calculations alone.  

I say spend a day at the dyno vs. many days of calculations and a half of day at the dyno.

Whoa now!  Not everybody is you!  I love getting into the modeling.  (Yes, I'm a geek and proud of it!)  I find it much more fascinating than any drag slip time or peak power figure.  I love seeing my theories proved (and disproved) on the dyno.  

Besides, after doing all of this, my understanding has increased exponentially over time!