Just about to start my MS project, and wanted to re think my injector situation. What setup seems to work the best. A setup for a decent sizedturbo to make good power. I have a MS2 v3. Added VR sensor. I made the harness, no adapters. Created my own 12V circut for the injectors.

I was going to use my greddy 720s for my primarys, but they are low impedence. I used resistors when I used them as secondarys for my s5 when it was stock. I came accross these 1000cc that were high imp, but I later found out they are Venom, and I wouldliketo go with 1200cc.

What sizes are reccomended, and High or low impedence? Are there MS settings I can change for this? Still a newb th this MS. thanks guys

 

The sizes you want depend on what size turbo you're running and how much boost you're planning on running, etc...

I would recommend keeping the primary and secondary sizes closer together if possible, as this can help with a smooth stage (at the expense of slightly worse low-load/idle tunability).

720 primaries with whatever size secondaries (depending on your application) are probably fine.

Ken

 

Finally use High-Z where possible because the Megasquirt will have a whole lot less issues with noise.

 

well, the high-z vs low-z thing has points on either side. High-z gives you better, more precise control over the injector, and can get a little bit more fuel flow out of it since it opens more quickly. Low-z is easier to do (but since MS does both, this is a moot point), and has less noise associated with it.

Also, its usually a lot harder to find anything over 850cc/min in high-imp, they're usually low-imp because you need the large current spike initially to get them open, since there's a bit larger area inside that they're exposed to the fuel pressure

 

you got that backwards. (unless "high-z" means low impedance )

...except for the part about the noise.

Also, you have to modify the megasquirt in order to run low impedance injectors, I have 2 pairs of low impedance injectors and am still running them with resistors just because it's less of a hassle.

 

you're right, i was getting them mixed up. How it should have read:

well, the high-z vs low-z thing has points on either side. Low-z gives you better, more precise control over the injector, and can get a little bit more fuel flow out of it since it opens more quickly. High-z is easier to do (but since MS does both, this is a moot point), and has less noise associated with it.

If you build the flyback protection circuits when you're assembling the MS (and both kits that i've gotten had the components necessary), then its not really any more work.
Also, its usually a lot harder to find anything over 850cc/min in high-imp, they're usually low-imp because you need the large current spike initially to get them open, since there's a bit larger area inside that they're exposed to the fuel pressure

 

With only two injectors per driver, using low impedance is no problem. Just use the default PWM settings and you will be fine.

I'm quite surprised that you found 1000CC injector as high impedance. Normally all big injectors are low impedance.

 

So Do I leave my setup alone and try it as is? w/ 720 prim low imp. with resistors, & my high 1000s? Or can I remove the resistors? get new low sec.?

Seems like this thread got some qwick attention & responses, maybe we can gety some MS expiriences with injectors?

 

LOL You guys all say, no problem... blah blah :p

Well I can tell you my megasquirt does have a problem with 2 low-z injectors on the secondary injector bank. Its not enough to cause the ECU to reset, or considerably alter the injector opening time correction, but there are spikes of 3v in the datalogs since using low-z injectors without the resistor pack. It is FACT that using High-Z is going to be a more robust solution. Of course this may not be possible if this guy needs more than 4x550cc.

 

check out t1raceparts.com

 

I'm using 2x 570 low imp and 2x 1000 low imps on mine, and it really is not causing any large noise issues (certainly not 3v spikes). I did try to tune my PWM's so that it matched the manufacturer's recommended profile as closely as possible, and I dont know whether this made the difference, but they seem to work great.