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[TTC]

Has anyone experienced any idling problems with large injectors and do the two different impedance style injs perform differently. 

Reason im asking is some guy I know who blows money like no ones business bought this AEM inj driver box thing. ( peak and hold inj driver or some shit)

Fucked if i know what it does, i use a megafail.

For the record I highly doubt hes running anything over 750cc.

[patsmx5]

you can idle bigger injectors better. My miata runs 62 PSIG fuel pressure all the time, so at idle, there's a 62 PSI + whatever vaccum the engine creates pressure delta between the injectors. I run 550s (rated at 3 bar delta) RC engineering low ohm and they idled great, I could lean it out till it misfires at idle no problem. I could also swith the MS from 2 squirts/cycle to 4 squirt/ cycle and it would still idle great (much smoother too, and response was MUCH improved) and could still lean it out till about 16:1 before the injectors messed up.

Now I have the resistors they came with wired in (did it troubleshooting, then left them in) and they idle fine at 2 squirts/cycle, won't idle at 4 squirts/cycle. Can still lean them out to 16:1 even with the resistors and a large pressure delta. FWIW, MS2 can do low ohm injectors stock.

[bigwig]

Pat,

I'm surprised you don't run your MS with sequential injection.  The add on board is $40, but IMO it's not that much.  The new MS3 was finally released and does sequential up to 8 injectors which is pretty fantastic.  It will really bring Megasquirt up a level.  Also, I'm pretty sure the whole "megasquirt can run low z injectors" thing is a bit of a stretch.  It can run the injectors, as long as you run a resistor box.  Just like any other ECU in the world.  I think it's a bit misleading.  In reality, in order to run low z injectors natively, you need an injector driver board from JB Performance.

As for the OP, the injector box allows the injectors to get fed a true peak and hold voltage signal vs the hacked up crap we send when using resistors.  Not worth $300, but maybe worth $100 to get a unit from this frenchy: http://www.jbperf.com/p&h_board/v2_0.html

If you have a decent way to control the injectors you should be able to idle anything within reason.  It's easier to idle richer than leaner.  Remember, anything richer or leaner than 14.7:1 requires additional ignition timing.

[TTC]

Pat, you run 2 or 4 squirts per cycle?

[patsmx5]

ms2 can run low ohm injectors, it has the correct drivers already. I built an MS2 and ran low ohm injectors for a year. No injector driver board, it has the PWM shit onboard already.

I'm running 2 squirts/cycle now with the resistors wired in. This summer I'm going to rewire some stuff and take the resistors out and go to 4 squirts/cycle. POssibly go to MS3 if the software is decent by then.

[patsmx5]

after reading a bit about MS3, I'm DEFINATLEY going to MS3 this summer.

[TTC]

I was running 4 squirts, but went down to 2. I can't remember why tho lol.   I remember now I think, iirc my afrs will be stabler, ill lower pw's and increase headroom on my injs.  It seemed to idle better as well.

[TTC]

I reaaaaaaaaly want to go with AEM.

[bigwig]

ms2 can run low ohm injectors, it has the correct drivers already. I built an MS2 and ran low ohm injectors for a year. No injector driver board, it has the PWM shit onboard already.

I'm running 2 squirts/cycle now with the resistors wired in. This summer I'm going to rewire some stuff and take the resistors out and go to 4 squirts/cycle. POssibly go to MS3 if the software is decent by then.

You're right Pat.  My bad.  I didn't think MS2v3 could run Low Z injectors.  It basically does the same thing as a resistor box from what I can gather.  It's not really running the injectors in true peak & hold.  I could be wrong.  Documentation on Megasquirt is kind of all of the place.

As for MS3, it definitely seems like a pretty great product.  I'm kind of surprised they are doing all the work with their PNP stuff, yet are using the MS2v3 board.  It seems more logical to wait a bit and then offer it with the MS3 board, but what do I know?

[patsmx5]

It actually does have the peak and hold, it runs them correctly. MS2 does anyway. You have to setup all the injector opening time, % current for PWM, etc. I thought it was causing noise problem with my electrical system so I wired in the resistors to try to fix it, but it didn't help, but then I never removed the resistors.

From what I can tell, MS3 is just a daughtercard that you add to replace the processor. MS1 = the computer. MS2 = MS1 + MS2 daugtercard. MS3 = MS1 + MS3 daugtercard. So any older MS can be updated to MS3.

[t_cel_t]

my 2.2 is just 1 board, are you sure thats how they are?

[TTC]

IIRC you can upgrade any v3 board to v2 with a daughter board. OR you can buy a v2 as 1 board.

[Aero]

ms2 can run low ohm injectors, it has the correct drivers already. I built an MS2 and ran low ohm injectors for a year. No injector driver board, it has the PWM shit onboard already.

I'm running 2 squirts/cycle now with the resistors wired in. This summer I'm going to rewire some stuff and take the resistors out and go to 4 squirts/cycle. POssibly go to MS3 if the software is decent by then.

You're right Pat.  My bad.  I didn't think MS2v3 could run Low Z injectors.  It basically does the same thing as a resistor box from what I can gather.  It's not really running the injectors in true peak & hold.  I could be wrong.  Documentation on Megasquirt is kind of all of the place.

As for MS3, it definitely seems like a pretty great product.  I'm kind of surprised they are doing all the work with their PNP stuff, yet are using the MS2v3 board.  It seems more logical to wait a bit and then offer it with the MS3 board, but what do I know?

As he said wrong.  It has the peak an hold drivers.  Even MS1 does, its only the old revision board themselves that lack the drivers.

[Joseph Davis]

Has anyone experienced any idling problems with large injectors and do the two different impedance style injs perform differently. 

Yes and no.  Bigger injectors tend to have a bigger variance in flow between injector @ low opening, unless you are laying out the cash for bling ID1000's or the same-shit-different-brand stuff Sewell sells a little cheaper.  Most of the bigger injectors are also low-Z, as high impedance big guns like the newer Bosch cores are still pretty pricey.

You'll notice this variance @ idle in some of the "Precision" 880/1000cc units, not always but every so often you get 1-2 of them that are way out of synch and to get the intermittant pop/stumble out of the idle they have to be idled in the 13's.  What's happening is you are getting one cylinder into the 15's so that it smooths out and carries itself, the other three are 11's to stoich and your wideband is reading the average.  It sounds less than ideal - I really don't like it when I have a car doing it - but there's no load at idle so nothing's hurt by it, and these cores are cheap and expedient.

Big stuff like the Bosch 1600's are absolute crap for small displacement engines that require small injector opening events.  You idle and part throttle the injectors in the 11-12's or else the engine spits and sputters and bucks as the leanest or richest cylinder(s) does and doesn't fire.  E85/alcohol help with that some since it requires more fuel for a given load, but they can be trying and definitely aren't good on gas.


I've generally been as displeased by big (old) cores with driver boxes as without them.  They all hiccough and spit or run super rich at light loads, great for a budget drag queen but not a street car.  Best experience I ever had was a 2JZ Supra on an AEM without a drive box, those inline 6 engines are simply super smooth and you can tune individual cylinder trims vs RPM which helps LOTs with that sort of thing.

[TTC]

Thanks jd.  So ideally if you had to use large injectors which do u prefer for quicker opening times to get decent idles with big injectors?

Are high Z injs generally better?

i

[Joseph Davis]

Thanks jd.  So ideally if you had to use large injectors which do u prefer for quicker opening times to get decent idles with big injectors?

Any of the Precision/FIC rebranded stuff is your bang for the buck.  You can get great idles out of their 880/1000cc lineup, but one in five cars will want a 13.5-13.8:1 AFR to idle smoothly.

Actually, decapped WRX topfeeds and I suspect uncapped SRT-4 injectors are probably the bang for the buck.  I tuned a KA24DE turbo on decapped WRX injectors and the car starts and idles smooth, likes a stoich AFR at idle.

Are high Z injs generally better?

For no other reason than they are also newer designed cores, and there are always improvements made to newer items which have nothing to do with their impedance, per se.

I really like RC's high-Z cores, they atomize fuel very well - which only matters for NA cars or for part throttle mpgs, a turbo car will take a poorly atomized solid pee stream of gasoline and completely atomize it in the combustion chamber and still get a better bsfc than most NA cars if the engine's setup is efficient.  They are a bit steep in price for the RHMT budget, or even mine which is the RHMT budget except for a few things I'm super anal about (fresh engines, OEM turbos, good electrical systems, proper tuning).  I tuned more high-Z RC 750's at Blueridge than anything, if I found a set cheap/used for a pumpgas setup I'd snag them in a heartbeat.  Hell, I'd miss an evening in bed with Spiker's mom to go get them, wouldn't even call the bitch to tell her I wasn't showing up.

[98vtec]

those 880's i texted you about took high 12's to idle nice 

[Joseph Davis]

those 880's i texted you about took high 12's to idle nice 

Sounds like tuner error.