Here is what I understand about tuning the TEC3 so far: with typical non-staged installations running on TEC3, we adjust UAP and POT to achieve the raw fuel curve, or until the desired AFR curve and actual AFR curve are as close as you can get them. From there, fine adjustments are made to the VE table to match the desired and actual AFR across the entire MAP and RPM range. Not *too* difficult.

But how does staged injection change this process?

I can't find any info in the TEC3 users manual! I appreciate the help!

Background info:
I have 2x 440cc primary injectors and 2x 440cc secondary injectors, running a 3 bar map sensor on a NA engine (am going turbo in the future). The wizard calculated UAP is 16.544ms (8500rpm max, 4 x 40lb injectors, MIT 0.70ms).

Staged injection does complicate the issue considerably. My suggestion to people trying to do this generally is for people running turbos where it is easy to cut down the horsepower you are making during the tuning process.

It goes like this:
Figure out how much boost you can handle with ONLY the primary injectors. Often times this is up to atmosphere or to some portion of the possible boost.
Tune the system as though you don't have staged injection.
Once you've tuned the primaries, copy the top tuned line in the VE table all the way to the top, now forget about the VE table.
Start turning the boost up and tune in the staging table.

This process is complicated for you by the fact that you neither have a turbo nor enough primary injector to handle the output of your engine even without a turbo.

Adding numbers into the staged table make the secondary injectors activate for that percentage of the primary pulsewidth. Calculating how much fuel your adding isn't difficult per-say, but it involves a lot of steps and can be easy to get lost or make a mistake somwhere that completely throws you off. I guess what I need to do is write a bit of a primer on tuning with staged injection. I unfortunately don't have time to do that now, but I think I can get to it in the next few days.

That's a huge help!

Just so I'm clear; I essentially tune the engine as if it were running on primaries only, in other words, how I described in my initial post. But by doing this, I'll be limited to a certain throttle opening/MAP reading due to the small injector size (let's say 65% throttle). Then that's it for tuning with the VE table. Tuning the secondaries is done by adjusting the values ONLY in the secondary injection table?

I have a set of 640cc low impedence injectors I was originally planning on using, but they are low impedence and won't work with the TEC according to the manual (correct?)

Thanks for the help... this answers a lot of my questions!

Don't forget to copy your highest tuned row all the way to the top of the VE table once your finished with the primaries. Otherwise, yes, that's the method.

I think the manual shows something about not running a single low impedance injector per channel with the purple TEC3s. While we don't really recommend people do that, it hasn't hurt anything for a great many people. We have dealers that do that on a regular basis with no issues. The TEC3rs and TECgt's have adjustable peak current, so running one low-impedance injector per channel is no problem.

This is something I've been looking at as this coming winter's project, and I had very similar questions.

Just so I'm clear on a couple of things...

1) This is going to result in the primaries going static (100% dc) above a fairly low boost pressure/rpm (at least for me). Any issues with that? It looks like this is by design, so I'm assuming not.

2) Once the calculated PW goes past 100% dc for the primaries, what value does the TEC use as a basis for the secondary? In other words if the resulting injector PW value in a particular cell in the VE table would result in a DC of 130%, does the TEC base its calculation on the percentage value in the corresponding staged table cell * 100% DC or does it base it on that percentage * the calculated PW?

My guess on this last point is that the calculation would be based on the resulting PW, and not 100% dc, since the PW calculations don't really look at RPM at all, and it would take a bunch of extra calculations to figure out what PW would result in 100% dc. Obviously the two different methods would yield very different results.

I am interested in this also, as I plan to use staged injection on my Buick motor.

I'm not sure, but I thought I read in one of the manuals that, at the staging point, the primary injectors' pulsewidth is reduced by some percentage so that the total fueling by both sets of injectors doe not take a step at that point. Am I getting E-motive stuff mixed up with some other EMS? I work with several these days.

I need to copy the pulsewidth/ms values in the table, correct? Otherwise I'll go past 100% duty cycle (as mentioned above).



It pretty much says in big bold letters not to run a single low impedance injector per channel. But if you're saying that people have been doing this with no ill effects, than I'll run my two low impedance injectors to simplify matters. How are the MIT values affected when running the low impedance injector?

TimZ: Yes the unit continues to calculate a PW that will go beyond 100% and that is what is used for the secondary injector calculation. The only potential issue with the injectors going static is that if you have big injectors (like the Bosch 160s) that measure about 4.5ohms, there may be issues with the injectors not staying open past about 25-30 ms. But you're running staged injection so you won't need to run 160 primaries, right? If you have injectors that measuer 1-2.5 ohms (real low impedance) or 12-16 ohms (real high impedance), this won't be an issue.

speeder: That is correct. The staged injection table takes a percentage that defines the percentage of the primary pulsewidth. This percentage is allows the injectors to come in gradually. While the fuel flow may not take a step, the VE table can look like it has a big step in it that is needed to keep the transition smooth. The trouble is, that is very difficult to figure out, hence the method I presented here.

B6T: You just need to copy the VE values. Don't worry about the primaries going static. You won't really care about that. In fact, it makes the tuning of the staging table easier because the fuel flow from the primaries will stay constant while you're tuning the staged table. The trouble with running low impedance injectors on the TEC3 purple units with that the peak current is not adjustable. They always run a 4amp peak, 1 amp hold. This is great for two injectors per channel. But if you have 1 injector per channel, there is the possiblilty (under certain conditions) that the channel will never peak. So the injector and the injector driver has nearly 4 amps runing through it for a potentially sustained period of time. This can be a problem. But if your battery voltage stays over at or around 13 while the enigne is running and the injector resistance is less than 2ohms, this should never be an issue. Remember ohms law: V=I*R. So 13v / 2 ohms = 6.5 A. That'll trip the peak current every time with some head room.

Thanks Jon - that's what I suspected, but it's really helpful to confirm. My primaries will be high impedance, so going static shouldn't be an issue.

I think Rick (speeder) was asking whether the TEC pulled pulsewidth from the primaries when the secondaries come in, and I think that the answer to that is "no". As I understand it, the secondaries can come in gradually, but the primaries will just go static. You could try to pull VE from the upper rows, but I think that you'd have a hard time pulling enough from VE in the upper rows to keep from going static.

If that is the case (Primaries' pulsewidth not automatically reduced at the staging point), Then that is disappointing- I'll have to try and figure out some tuning (or hardware) solution to get around it. Not to jack this thead, but I will be using identical sets of 85 pound low impedence injectors on the Buick.

As long as we don't run into issues with the injectors being static, it shouldn't be an issue - I think you'll always have a little bump at the point in the map where the secondaries start firing, due to the non-linear nature of the fuel delivery at really low PWs. I'm afraid that you'd have a difficult time predicting just what that was going to look like and taking out the appropriate amount of fuel from the primaries anyway. Just try to put it in a region where the boost is ramping in so you aren't there for very long.

Also, given the fact that the PW for the primaries will increase linearly as you increase MAP (due to the base IOT/TOG fuel curve), I don't see how you'd be able to avoid them going static at some point.

OK, Maybe primaries going static isn't a big deal - I guess that depends on how well the peak and hold drivers sustain this condition - I'm using a TEC3r, and do understand that it shouldn't be a problem with 2.2 ohm injectors. I just don't like the idea.

In my intended use for the car (Road racing on long, high speed courses), I will almost certainly be running at somewhere past the staging point for extended periods of time.

The injectors I have measure 2.6 - 2.7 ohms
I believe my battery voltage is on the low side at 12v

12v / 2.7 = 4.44 A

Is running these injectors risky?

And if the injectors go static, will that increase the risk of damaging the injector drivers?

This may be helpful to those that are trying to picture how a VE table might look when running a staged aux fuel supply.
Let me explain a little about my fuel system since it's not a simple staged electronic injection system.
I run alcohol and use 160 lb. bosch electronic injectors for the primary system. For the secondary system I have a mechanical fuel injector nozzle pointed down the middle of each intake runner. An 8 psi boost pressure switch opens an electrical lean out valve to allow fuel to the 6 mechanical nozzles. The fuel to the nozzles is supplied by the same fuel system that is feeding the electronic injectors. Same boost referenced pressure.
Due to a small space volume between the solenoid and the nozzles, I have to program a little extra squirt of fuel from the electronic injectors to cover a lean spot as the aux system first energizes. The lean spot is caused by air being purged from the space volume.
When the fuel hits the nozzles, a large cut back of pw must occur with the electronic injectors to keep the fuel supply smooth, as far as the engine sees. The pw of the e-injectors then continues to climb until max duty cycle is reached.
The balance of the correct size fuel nozzles, fuel pressure, primary injector size, boost target, hp target, max duty cycle target, TOG, IOT, and the boost level that I have the aux system turn on are all extremely critical due to the limits put on me by the plus 50 and minus 50 percent range of the primary VE table. Right at the extra shot of fuel where the aux fuel system turns on, the VE reaches +50 percent, then immediately the pw is cut back to -50 percent, so that just in that short part of the table I use the complete range of the VE table at the TOG/IOT combination.
I'm still tuning this engine in, and so far fueling is adequate to 31 psi with the injectors at 85% DC.

This is a video of the fuel table translated to Motec software. I absolutely hate the graphing detail and lack of accuracy of the WinTEC software and have gotten used to using the Motec graphing feature of their software to get a better picture of how the fuel map appears. I'm sure this is going to be very new to some people, as I don't think there are too many people trying to fuel their engine this way. Let me know what you think.

[youtube]http://www.youtube.com/watch?v=fSe0s9q5EEw[/youtube]

Another note. I do not use O2 correction.
The black dots on the fuel map show the present boost trail up to 8 psi.

If I can stage my system, you ought to be able to stage e-injectors much easier.