MSefi.com read only forum (Jan.15,2018)

Sorry about newbie question...

What's the (dis-)advantage of high vs low impedence injectors?

I'm looking at the Siemens 55lb injectors and it seems that I can get them in high or low impendence. Price is different, but is there performance differences?

thanks...

Does anyone know how other ECU's like Haltech, Motec, Electromotive ect handle this? Do they run everything through a flyback cirucit?

Thanks for the quick & very useful response Lance...

I'm just about committed to getting the MS and in fact deciding on v2.2 or v3.0 (stability vs functionality).

Even if I decide on v2.2, I think I'll rather live with the small "hassle" and get the right performance

Just my two cents here. If you do go with the low imp. style be sure to use the flyback. I ran mine without and never fried the board but always had starting and idle problems. I also could not run more than one squirt per cycle. The car ran great otherwise! I have since switched to nearly identical flow high imedence injectors and all my problems went away. I am quite sure a flyback board would have fixed my ills too but this was easier for me at the time. All I am saying is your "third option" being low imp and no fly back sucks in comparison!

Todd

the # of injectors and available current capacity for ms were my primary factors. my app uses 8 injectors with a low supply power availability. i started with lo imp 55lb units like you, but had numerous probs. when a driver fet fails, it almost always shorts the injector to direct +12v. this will burn out a low imp injector bank($) very quickly, which can flood and hydraulic an engine. my first experience with lo imp was to tow my car home, yank and replace my rings/bearings. bummer
after getting custom hi imp 60lb units, my ms current consumption dropped almost in half, with no more driver snafus.
bottom line is, hi imp are much more forgiving in a DIY environment.

I'm planning on a V3 board to run my 95 Talon TSI with the extra code and staged injection to avoid drivability problems. There would be 8 total injectors. The injectors that I would be using are low Z injectors, both the 42 lb stock ones, and the 52lb RC's that I am using now with the stock ecu. Are there any drawbacks to using these with the resistor pack that my stock ecu uses?

Aero, i was just thinking/wondering the same thing. Can you use the resistors in line with low z inj and make it work with a V1 or V2 board and no flyback?

LigonierA1 wrote:Aero, i was just thinking/wondering the same thing. Can you use the resistors in line with low z inj and make it work with a V1 or V2 board and no flyback?

That's the way i'm running my 4g63T. V2 with inline resistors 72# injectors no flyback.

Thanks for the reply. Can you give any more details about your setup? Did you use the 1g CAS? If you did, do you know what year it came off of? Optical or Hall effect? Does it idle well on the 72# injectors? How is your gas mileage? Is it in a awd or fwd dsm?

aero wrote:Thanks for the reply. Can you give any more details about your setup? Did you use the 1g CAS? If you did, do you know what year it came off of? Optical or Hall effect? Does it idle well on the 72# injectors? How is your gas mileage? Is it in a awd or fwd dsm?

Yes used the 1g cas out of a 92 (optical). It idles not bad with the 72# injectors, almost like i have a set of cams. I should be able to tune it out better just haven't had the time yet. Gas mileage so far is around 28 MPG but that's with getting on the boost all the time so i can tune it so it's most likely better. And the car s a 94 Colt that i swapped a 4g63t into as well as AWD, along with a 60 trim T3/T4 and a water to air I/C.

Sounds like a cool setup. Are you running just fuel or spart also? If so did you use the stock dsm coilpackand powertransistors? What kind of mods did you have to do to the base MS?

Good information. So back to the topic...I have 160lb low imp injectors. They WILL work with a V3 main board? And I should be able to get them to idle?

Thanks!

IcantDo55 wrote:Good information. So back to the topic...I have 160lb low imp injectors. They WILL work with a V3 main board? And I should be able to get them to idle?

Thanks!

Those are some big injectors. I just got my 72#'s to idle way better last night. The one thing that made the difference for me was the injector open time in the constants section. I had to bmp it up from 1 ms to 1.3 and the idle is pretty nice now it hunts about 30 rpm up from 900 but steady no lump any more.

Clinton_H wrote:

IcantDo55 wrote:Good information. So back to the topic...I have 160lb low imp injectors. They WILL work with a V3 main board? And I should be able to get them to idle?

Thanks!

Those are some big injectors. I just got my 72#'s to idle way better last night. The one thing that made the difference for me was the injector open time in the constants section. I had to bmp it up from 1 ms to 1.3 and the idle is pretty nice now it hunts about 30 rpm up from 900 but steady no lump any more.

I don't really need 160's but I got a deal on them so if I can tame them for the street I'll get them. I could prob use 72's like you. Whats your engine combo?

Clinton,

Hmm, I think you are dancing around the problem by setting the injector open/close time that high. I'm guessing that what you see now for idle PWs is a steady 1.3 ms, which is probably just above the true IOC time.

Since the PW equation looks like PW = reqFuel*this*that + IOCtime, the shortest possible pulsewidth is IOCtime (at least for old B&G code), so if the IOCtime is longer than what it takes to actually open and close the injector, then you'll have a modest amount of fuel delivered whenever you have a "zero" calculated portion for PW.

If this works, well ok, but the intention is that the injector open/close parameter describes the physical device, and is really not a tuning parameter (i.e., if you were to swap injectors, you should be able to reset reqFuel, IOCtime and few other things, then drive away with no retuning).

If it were me, I'd be inclined to set the IOCtime back to 1.0 (that's more likely correct for your big lo-z injectors), and mess with the VE table around the idle point. I make sure all the VE entries are equal around my idle plateau, I've found that stabilizes the idle quite well. On the other hand, you might need the MS-II's better PW resolution to completely resolve idle issues, but it's probably a secondary concern on an engine with such large injectors, isn't it?

Eric

Thanks Eric, i wasn't sure if that was the right way but it seemed to work. I'll set it back and play some more. I did edit the table so my idle values looked like this.

45 47 47 47

30 47 45 47

15 47 47 47

500 800 1200

But it didn't seem to help as much as i'd like. Your probably right about needing the better PW res of the MS-II, which is most likely what i'll end up doing in the near future. I fully expected to have a lumpy idle, 2.0lt with injectors that large it's expected i think.

IcantDo55 wrote:

Clinton_H wrote: Those are some big injectors. I just got my 72#'s to idle way better last night. The one thing that made the difference for me was the injector open time in the constants section. I had to bmp it up from 1 ms to 1.3 and the idle is pretty nice now it hunts about 30 rpm up from 900 but steady no lump any more.

I don't really need 160's but I got a deal on them so if I can tame them for the street I'll get them. I could prob use 72's like you. Whats your engine combo?

Here's my setup. viewtopic.php?p=65893#65893

guys I need clarification. the manual seems to suggest that v3 has a flyback board built in.

does this mean I can run 8 low impedance injectors without any other hardware?

Yes, the V3.0 has a built in flyback board.