Ok, basically, i have the injectors set up as staged, but the secondaries arent firing (rpm only setpoint, set around 3k rpm just to test).

To start, the primaries are high-imp and the secondaries are low-imp (the 1000cc japanese ones on www.injector.com). To get around this, I wired one of the stock injector resistor boxes inline with the injectors, so that the total resistance for the secondary branch was 14 ohms. Then the settings on the basic constants page are set for high imp injectors. This may be one problem, and I was thinking of just ordering new low imp primaries.

However, I was looking thru megatune and noticed that I had the injector staging set as "alternating" and the number of injectors as "4", all in the basic settings page. I think this last one just affects the req_fuel value, but would the "alternating" affect staged injection, or does staged take precedence? Id like to avoid ripping the harness and UIM off to redo the primaries if i dont need to. Thanks!

 

Set number of injectors to 2, simultaneous. Your mix of low and hi-z injectors should be fine as the resistors you are using effectively convert the low-z to hi-z. To test the secondaries, ground the secondary output pins on the DB37 harness (with fuel pump disabled!), and listen for the clicking. That will verify that they are actually wired correctly.

 

ah, that sounds like a much better way than what I was planning on doing. I'll do that during my lunch break to try it out. I hope thats it, and I dont need to get a new set of primaries (enough $ into this car already...)

 

well, trying that out, and switching to simultaneous didnt do anything, so I ordered a set of low imp 570cc injectors to match, and will just cut out the resistor pack. The 550's on there seemed to be working fine, but no harm in replacing them (besides to the wallet)

 

missed the edit window time... so just to check, the scaling factor for staged injection is:

primary flow * 255 / (primary + secondary flow)

right?

 

The staged injection setup details are here:

http://megasquirt.sourceforge.net/extra/stagedinj.html

 

oh... 512... not 255... oops, lets go try that!

 

nope, still not firing. low-imp it is

 

Ok, to resurrect this thread, I just got the new low-imp 570cc primary injectors (to match the low-imp 1000cc secondaries), and installed them. All 4 are new Marren fuel injectors, from www.injector.com

Now, im playing around with megatune doing the whole PWM adjustment business, and at 1ms opening time, I can adjust the PWM% all the way down to 0 and it keeps running. Ok, so its running completely on the opening time. So after lowering this first to .9ms, and then to .8ms, I could still bring the PWM down to 0 without affecting the idle. However, if i set the opening time to .5ms it would die and not want to start again. I set it back at .8ms opening time and 25% PWM cause my laptop was going to die (and stupid me forgot the charging cable at my apt in brooklyn), so i can use the car to get to work tomorrow. Does this sound normal at all?

Also, while doing this, I hit alt-b (on settings that i knew worked) and suddenly the car died. Trying to start it after that was just pushing a TON of gas fumes out the exhaust (lotsa white smoke). I deflooded it, and it started right up like nothing happened. What could have caused this?

The secondaries are also not working still, even after taking the resistors completely out of the loop with the low-imp settings. This is the bit thats really getting me annoyed. Any thoughts now?

 

I've never run low-z injectors without resistors, so I can't comment on your pwm tuning comments.

When hitting alt-b, it's normal to have the engine hiccup a bit. I can't comment on why it stalled and flooded. I haven't seen this behavior before.

As for secondary operation, does it work properly on the stim? Also, did you check your harness thoroughly, and try grounding the secondary pins to test injector operation? If you are running low-z without resistors now, make momentary connections, not continuous, or you could smoke the injectors.

 

I don't know if it works properly on the stim cause i was using a stim I built for my school's FSAE team, and having graduated, I cant really use it too easily. Megatune displays a PW2 signal when conditions for staged injection are met, and hooking up a voltmeter between Battery V ref and one of the injector wires between the injector and resistor, I get 0 V before conditions are met, and about 1 volt when they were (this was still with the high-Z settings, high-Z primaries and resistors in line with the low-Z secondaries). I couldnt really get a great reading because the engine would rev past the setpoint by about 2 or 3 hundred RPM then studder and fall about 8 or 9 hundred RPM below the setpoint, so it was hard to pin down what the actual equivalent voltage would be.

When you ran low-Z injectors, what resistance did you use? I wired these up thru a stock injector resistor (I had to get one from an earlier car, mine was high-Z stock), and when i checked it with a multi-meter the whole circuit was 11 ohms.

 

If you've checked all the wiring, and you're absolutely sure it's right, and the software is showing the proper values for pw2 when staged injection engages, then the only things left are bad injectors, or bad components in the MS.

Ken

 

I'm going to re-try the pin-grounding idea that renns proposed with a friend to listen for the injectors since I had a hard time doing it myself, and then try to verify the signal from the MS (or at least something happening on the MS end). we'll see how it goes.

 

So I tore the UIM off again and it turns out the wiring was fine, the injectors worked fine, and the MS had no problems... the error was me. Somehow I managed to swap the primary and secondary injector plugs, so I was idling and running the car on the 1000cc/min injectors, and when it tried to stage, it was trying to bring the 570cc/min injectors on. That also smoothed out the weird un-solvable acceleration enrichment stutter, and the warmup is working a lot better too. I had to readjust the VE table, but all is running much better now. I just need to re-tune the VE table for the smaller injectors.

It does a bit of stuttering whenever the secondaries come on now, what have you found (settings-wise) works well to solve this. I have a staging time of 20 cycles on, it triggers off of either RPM>3600 or MAP>80 kpa

 

If you have a full-span TPS, set up staging to occur after the secondary plates have opened a bit. That eliminates the transit delay issues associated with squirting fuel into stagnant runners.

 

no, its the stock S4 TPS. How easy is it to retrofit an S5 TPS onto the S4 TB?

 

If you have the narrow range TPS, you can set it up to stage when that's at 100% open...

If it's set up right, it should go to 100 right around when the secondary throttle plates open.

 

yea, i was thinking of trying that. That and an RPM switch at about 3.6 - 4k, so it'll be a little bit out of the normal range of speeds I see on the highway. I'll set it up for my commute home and see how it feels.