Low Z noise problems

[svocapri]

[/quote]
good question. I'd say Q3 but I would want to try it each way[/quote]

Um... I am a bit confused by your answer?

Q3 -> 47uf_cap -> Q9 (which is lifted and connected to 12v outside of megasquirt)

or

Q3 -> 47uf_cap -> Megasquirt board at the Q9 12 volt hole

I guess the question is, does the cap filter noise within the Megasquirt or does it absorb the energy from the PWM flyback and thus prevent noise from being generated in the first place?

[Peter Florance]

good question. I'd say Q3 but I would want to try it each way[/quote]

Um... I am a bit confused by your answer?

Q3 -> 47uf_cap -> Q9 (which is lifted and connected to 12v outside of megasquirt)

or

Q3 -> 47uf_cap -> Megasquirt board at the Q9 12 volt hole

I guess the question is, does the cap filter noise within the Megasquirt or does it absorb the energy from the PWM flyback and thus prevent noise from being generated in the first place?[/quote]
It filters noise from the injectors

[kubeq_sq]

as i have problems reaching the same place in megamanual twice... i can't find the place when it was written about low Z inj and wasted spark.... sorry

[kubeq_sq]

could You tell me, couse i read in ms III manual, that with low z injectors i shoul use about 3ohm resistors... could you tell me if i can use same resistance for PCB in MS II?? because the calculator on the side told me to use 10ohms, but injectors don't want to open... i tried also 5ohm, but also they do not open. i wanted to use resistors with low Z injestors to use double fuel in semisequence (two channels working on both maps, theinjectors would be switched by the relays) but my low Z don't want to open with reccomended resistors. i would try with lower resistors, but don't want to burn anything in ms

[Peter Florance]

could You tell me, couse i read in ms III manual, that with low z injectors i shoul use about 3ohm resistors... could you tell me if i can use same resistance for PCB in MS II?? because the calculator on the side told me to use 10ohms, but injectors don't want to open... i tried also 5ohm, but also they do not open. i wanted to use resistors with low Z injestors to use double fuel in semisequence (two channels working on both maps, theinjectors would be switched by the relays) but my low Z don't want to open with reccomended resistors. i would try with lower resistors, but don't want to burn anything in ms

Your settings should be set for high Z if you use resistors. Are you using the correct settings?

I don't bother; I use low z injectors with the recommended settings. If you use enough ground wires and add the capacitor I mentioned above, you should not have a problem.

[Tjabo]

Peter,

Are you saying you run the Low-Z injectors directly off the MS3-X board with some suggested settings, or using the PWM function of the V3 main board? Sorry for my confusion...

FWIW, I tried a set of Low-Z injectors running via PWM from the V3 mainboard, and had NO noise issues at all. It was a very pleasant experience. Unfortunately, I had damaged a rod bearing about the same time that I tried the bigger injectors, so I didn't get to fully "test" them. More soon though!

Thad

[kubeq_sq]

i.m running them now as a low z injectors using pwm and flyback boards build in PCB v3.0.... but i wonted to run them as high Z, because my petrol injectors are high Z, so can i use 3ohm resistors with my 2 ohm ijnectors (3 connected per channel)will ms board last out that current? about 7 Ampers per channel??

[Peter Florance]

Peter,

Are you saying you run the Low-Z injectors directly off the MS3-X board with some suggested settings, or using the PWM function of the V3 main board? Sorry for my confusion...

FWIW, I tried a set of Low-Z injectors running via PWM from the V3 mainboard, and had NO noise issues at all. It was a very pleasant experience. Unfortunately, I had damaged a rod bearing about the same time that I tried the bigger injectors, so I didn't get to fully "test" them. More soon though!

Thad

No, V3

I am also running them on the V1.04 MS2Sequencer, which is the same output hardware as MS3X

[racingmini_mtl]

I am also running them on the V1.04 MS2Sequencer, which is the same output hardware as MS3X

You mean you're running low-Z injectors in saturated mode? And nothing gets too hot? How much duty cycle are you running on these?

Jean

[Peter Florance]

I am also running them on the V1.04 MS2Sequencer, which is the same output hardware as MS3X

You mean you're running low-Z injectors in saturated mode? And nothing gets too hot? How much duty cycle are you running on these?

Jean

I'll have to look at a log. Injectors are fairly small, so I'd say probably 70-75% when I'm flogging on it.

Fully sequential so maybe there is more time to cool?

I'm not the first person to run these exact injectors on a sequencer.

[racingmini_mtl]

I'll have to look at a log. Injectors are fairly small, so I'd say probably 70-75% when I'm flogging on it.

Fully sequential so maybe there is more time to cool?

I'm not the first person to run these exact injectors on a sequencer.

I don't think this is a good idea. The fact that it runs and hasn't caused issues yet doesn't mean it's correct. Running sequential doesn't give more cooling time because at 75% duty cycle, no matter how many squirts you use you have 25% of the time to cool off. And actually with a single pulse, you will be in current limit mode for a longer period so it may even be worse.

The reason I don't like it is that this will have an impact on the dead time because you shut down the injectors with 5A running through them. Also, if the drivers ever go in thermal shutdown, it's going to be at the worse possible moment. It will be at high load/RPM when duty cycle is high and likely the temperature is also high. If they go in complete shut down, it's not too bad since it would basically be fuel cut. But if they go in shut down during the pulse (and even worse, repeatedly) then you get a (sustained) lean situation. This is a nice recipe for engine melt down.

So I would never recommend people do that and this is also the recommendation for MS3 as far as I know. Relying on a safety mechanism for normal operation is not a good practice.

Jean

[jsmcortina]

I tested 2.5R low-z injectors with the MS3X and while I didn't get into thermal shutdown mode, the board was hot enough that you could smell it and the injectors boiled water.

That's why I state that resistors MUST be used with low-z. However, I don't think you need to use a very large value three to four ohms seems like a good compromise.

James

[Peter Florance]

I'll have to look at a log. Injectors are fairly small, so I'd say probably 70-75% when I'm flogging on it.

Fully sequential so maybe there is more time to cool?

I'm not the first person to run these exact injectors on a sequencer.

I don't think this is a good idea. The fact that it runs and hasn't caused issues yet doesn't mean it's correct. Running sequential doesn't give more cooling time because at 75% duty cycle, no matter how many squirts you use you have 25% of the time to cool off. And actually with a single pulse, you will be in current limit mode for a longer period so it may even be worse.

The reason I don't like it is that this will have an impact on the dead time because you shut down the injectors with 5A running through them. Also, if the drivers ever go in thermal shutdown, it's going to be at the worse possible moment. It will be at high load/RPM when duty cycle is high and likely the temperature is also high. If they go in complete shut down, it's not too bad since it would basically be fuel cut. But if they go in shut down during the pulse (and even worse, repeatedly) then you get a (sustained) lean situation. This is a nice recipe for engine melt down.

So I would never recommend people do that and this is also the recommendation for MS3 as far as I know. Relying on a safety mechanism for normal operation is not a good practice.

Jean

Jean, I don't recommend for or against it on MS3x. I'm beta testing to find out how it does.

On V3 boards, it absolutely works. I don't understand why all the hacked up boards, lifted and separated 12v lines etc.

[racingmini_mtl]

I tested 2.5R low-z injectors with the MS3X and while I didn't get into thermal shutdown mode, the board was hot enough that you could smell it and the injectors boiled water.

I'm just curious. Did you scope the outputs to see if you were actually getting the full pulse width and not some shortened ones?

And just as a note, the heat will come from 2 sources: the over-current limitation and the flyback. With inline resistors, you will completely eliminate the first and significantly reduce the second (which is proportional to the square of the current).

Jean

[Peter Florance]

I tested 2.5R low-z injectors with the MS3X and while I didn't get into thermal shutdown mode, the board was hot enough that you could smell it and the injectors boiled water.

I'm just curious. Did you scope the outputs to see if you were actually getting the full pulse width and not some shortened ones?

And just as a note, the heat will come from 2 sources: the over-current limitation and the flyback. With inline resistors, you will completely eliminate the first and significantly reduce the second (which is proportional to the square of the current).

Jean

No not yet.
I was working more with the new VR circuit testing. The Monkey had many miles with the same output hardware, so that was not my first concern.

[kubeq_sq]

ehh, could You help me, couse i;ve made today some driving at low z injector setting at lpg and when my flyback board turns on my car starts struggle, as it has gas in fuel rail, i can't accelerate, i have loss syncs... i've made upgrades told by ryniobl and that's how looks my board :

if You see anything wrong please tell me... my low z just don't work with resistors, they don't open :/
if i would like to use resistors with them what resistance whould they have?

[Peter Florance]

ehh, could You help me, couse i;ve made today some driving at low z injector setting at lpg and when my flyback board turns on my car starts struggle, as it has gas in fuel rail, i can't accelerate, i have loss syncs... i've made upgrades told by ryniobl and that's how looks my board :

if You see anything wrong please tell me... my low z just don't work with resistors, they don't open :/
if i would like to use resistors with them what resistance whould they have?

I'm guessing something is not functioning correctly
Can you scope the outputs and post a picture?

[kubeq_sq]

and here is a problem... i haven´t got a scope :/ the biggest chances are that i shuold change which part?? if it is necessary i will go on scopy to my friend, but You have to write my step by step how to scope and what, because i've never done it... :/

[jsmcortina]

On V3 boards, it absolutely works. I don't understand why all the hacked up boards, lifted and separated 12v lines etc.

I agree. Seems there are a lot of urban myths flying around.

James

[Peter Florance]

and here is a problem... i haven´t got a scope :/ the biggest chances are that i shuold change which part?? if it is necessary i will go on scopy to my friend, but You have to write my step by step how to scope and what, because i've never done it... :/

scope middle leg of Q1 and Q5

that's all I need to see