DIYPNP + Low Impedance Inj
 

I've just set up my DIYPNP with the sequential mod board from DIY. I am using MS2Extra 3.1.1 firmware.

I thought that this would allow me to use my low impedance EVO injectors in peak and hold mode, but the PWM settings are grayed out when I select 'Additional Drivers'

My understanding was that the sequential mod allows four low impedance injectors to be used. but having searched the forums it seems that the MS can't do peak and hold with additional drivers. It's very confusing though what with MS1/MS2 and several different versions of software.

Has anyone got this setup working? I know I can use inline resistors but I don't want to.

I've emailed DIY but if anyone can give me a quick solution it'll save pulling the injectors and putting the old ones back in.

adding two extra injector drivers for seq. =/= supporting low ohm.

As above. RTFM noob! :-P

Seriously though if you want to retain peak and hold functionallity you'll either have to build 4 new injection driver circuits in the proto areas, or buy and use one of JPBerf's peak and hold driver boards, this will necessitate hacking onto the uS card to bypass it's 2 internal injector drivers mind.

LOL, me thinks the noob *was* the one who read the manual. ;)

The DIYPNP injector drivers can support up to 4 high impedance injectors each OR 1 low impedance injector each. The drivers have built in current limiting. There is no software setting. Should be good to go for you giblets.

In saying that, wouldn't you need to think about the wiring and whether it would cope with low impedance injectors? My thinking is the extra current could be over what the DB15 or other paths might be able to cope with - e.g. what is the expected max current expected to be seen over the harness with low impedance at full RPM ??

as for this, the pwm menu you want for this is under the injector characteristics menu.

The DIYPNP won't use PWM current limiting though.

I do not recommend this. On a car I prepared an enhanced DIYPNP for (and tuned it), we had huge problems (the car would misfire at idle and TS would disconnect all the time) and couldn't figure it out. At some point, one injector driver got burnt. Turns out the 1000cc injectors were low impendance. We swapped them for high impedance 775cc EV14 injectors, all problems solved.

Touche ;)

I was under the impression the uS module has the same injector drivers as the MS3X which can't handle low impedance injectors.

Happy to be proved wrong mind.

Interesting and unfortunate, but I also think isolated. I'm sorry to hear you had problems with that install. We have not seen similar behavior in both on car and bench testing. I believe the VND's are rated for 5 amps.

I do prefer high impedance injectors however. Less heat and less noise.

That might be the reason. These were 2.1Ohm injectors, and the enhanced DIYPNP runs the alternator at 14.5V.

ah i see what Ben was saying.

Ahh, yeah that may have been a bit sketchy without current limiting resistors.

We've worked the VND's over very hard both on car and on bench, and have not been able to make one fail. We have been able to make them thermal, but they always come back once they cool down.

Customer said the injector died on a 4th gear WOT pull. 20psi on a 2871, 1.8 w/VVT. He though he had lost a cylinder. :rofl:

Thanks for the response.

So I will ignore the PWM settings and see how it goes.

Does this mean that the PWM setting have zero effect on the DIYPNP?

Not sure, but this is worth reading http://www.megamanual.com/megatune.htm#sn

Having done a bit more research I think I get it now. The DIYPNP injector drivers don't peak and hold but just limit the current so effectively the same as putting resistors in line. well It'll do for now.

I guess this is going to effect injector dead time because that would be related to the current through the injector? Does the VND keep a constant 5amps regardless of voltage or does it just limit the current to 5amps? I'm wondering what effect changes in battery voltage would have on the current/injector dead time.

Update: tweaked REQ_FUEL and injector opening times, enabled sequential fuel/additional drivers etc.. and things are running very well.

Not sure I needed the 510's but my previous 330's were seeing uncomfortably high dutycycles and I haven't noticed any ill effects with the larger injectors.

Thanks for the help.

Robert,

Sorry to kick the dust on this a whole pregnancy later, but I will do some oscilloscope current scoping when I get do my turbo/MS project. I've seen some very interesting PWM operation on new GDI cars to mimic "peak and hold" on a 65V injector circuit and I really want to get a handle on the Megasquirt's as installed injector driver capability so we can choose the right injectors for our builds. I also have a ASNU bench to flow what we're running.

Glad to see your car is running OK.

Dave

Regarding low impeadence injectors