MS-II Simultaneous or Aternating?

[cygnusx1]

How should I go about wiring/programming my MS-II on my L28ET with 440cc injectors, high impedance.

 

My gut feeling is to use simultaneous injection for all six injectors, 2 injections per cycle, and wire all injectors to one bank. (like Nissan did it).

 

If I use alternating, and wire 3 injectors to each bank, then I will only be using half the flow capacity of my injectors?...no?

 

I confused. Someone please set me straight!!

[Tony D]

I wired three to one driver, and three to the other driver.

 

My logic: if one driver dies, I can jump the wire over to the other and run it home, or at least run it on three cylinders to a safe parking spot.

 

In reality, depending on which year Nissan you have, they actually had six drivers. they only supplied POWER to one wire. The grounds were individually run to drivers that pulsed the injectors through gating the ground.

 

You can run simultaneous and wire three injectors to each driver. They are not mutually exclusive. The Req Fuel constant will determine pulsewidth and deliver accordingly, regardless of mode selected.

 

it's just that some engines will run better alternating two squirts, and others simultaneous two squirts---it depends on your fuel delivery and pressure fluctuations. Alternating one squirt seemed to keep my idle smooth and fuel pressure constant as opposed to simultaneous two squirts.

 

Clear as mud now? LOL

[cygnusx1]

Okaaaay. Hmmm. So if I do alternating, single squirt per cycle. The single squirt will be a larger squirt. Actually double the size it would be at two squirts per cycle. That would make the ReqFuel pulswidth longer at idle which is better for bigger injectors. Right?

 

I think it makes sense to do what you did then.

 

 

EDIT:

Okay back again! When I try to set Megatune to Alternating, 1 squirt. I get a message telling me that I cant do that with this number (6) of cylinders.

[z-ya]

You can't run alternating on a 6 cylinder with MS. You would need 3 injector outputs to do it. Wire three to one output, and three to the other. Like Tony said, if one fails, you can limp home on three cylinders. If they are high Z injectors, no series resistors are required, and you can turn PWM off.

 

So set your MS for simultaneous, and start with 3 squirts. With 440cc/min injectors you may need to drop it down to 1 or 2, but start with 3.

[cygnusx1]

Okay, sounds like a plan. I will use both drivers on Simultaneous as you say.

 

Thanks, soon I will be paying you a visit up there in New Hampshire! Fingers crossed.

 

Yup PWM is set off already thanks. I have read the manual top to bottom about 12 times already and some things I learned...but...I won't really learn it until I start turning the key. I still have some fabrication to do before the wiring. I have all the parts lined up. Three or four more days of fab. and about a week of wiring before it's ready to fire. I can only afford about an hour a day so I am moving slowly.

[z-ya]

We have a club dyno day scheduled in June, and you are more than welcome to come. Keep informed on your progress and I'll reserve a spot for you.

[mobythevan]

You can't run alternating on a 6 cylinder with MS.

 

Now I'm lost because I always ran alternating on my L28et. It idled much better with alternating. The installation guide shows to use alternating. I am not saying it is right, but if we can't do it should an update be made? I remember discussions about fuel rail pressure pulsation and injector size trade off, but no one ever said it couldn't be used.

 

What would happen if all the people using my inital values had everything else the same, but used simultaneous instead of alternating? Would that account for everyone saying it is really rich because with alternating I had more of the time used up during opeining and closing so not much gas. But now with simultaneous they spend more time with the injector just open so its rich? Just rambling, but run through the reasoning so I can figure out what makes sense.

[cygnusx1]

I think that if you run alternating, 2 banks, with a six cylinder, the math doesnt work out evenly. In otherwords the frequency of fuel being injected doesn't match with the 4-cycle of the motor and you would get an interference pattern, or "beats" as they say in wave interference-ology. Of course, the math should be done to prove or disprove me, and I need a drink to do that but I am at work, so I can't drink.

 

Anyhow the Megamanual says you can run alternating, 2 squirts with a 6cylinder engine. I will have to see what that makes for my idle PW because it might be too small....confusion takes hold again.

 

FROM THE MEGAMANUAL:

Note: if you choose alternating for port injection, make sure your number of squirts is an even number (2,4,...) and evenly divisible into the number of cylinders. For example, with an eight cylinder engine, you could use alternating and 2, 4, or 8 squirts/cycle. With a six cylinder, if you choose alternating, you MUST use 2 or 6 squirts/cycle. Also, the only possible combinations for an odd-cylinder count engine are either 1 squirt/simultaneous or N squirt/simultaneous combination, where N is the number of cylinders."

[mario_82_ZXT]

I'm running alternating as per the sticky as well...

 

Fuel pressure fluctuated less and idle was also improved...

Mario

[mobythevan]

cygnus, thanks for the update from the manual. It appears that alternating 2 squirts is acceptable. That is what I was using and had put in the sticky so I just wanted to make sure and I wanted someone else to verify since I can't check my own work.

[cygnusx1]

In Post #4, Z-YA, I think, means that you CAN'T run Alternating, "1-squirt", on MS.

 

OK Alternating banks, 2 squirts per cycle, gives me a Lower ReQ fuel matching the upper ReQ fuel of 7.2ms. This should result in an acceptable idle duty cycle for the 440cc injectors and also minimize the rail pressure drop during injection. I can't wait until all the bench-tuning becomes real-tuning. A few more days and let the wiring begin!

 

The coolest thing is that with this "Hamachi" network program, I can tune my MS-II from anywhere in the world with an internet connection. I am at work on lunch break right now and downloading/uploading .msq files and tweaking them to the MS-II that is in my livingroom on a wireless laptop also running "Hamachi" 40 miles away!

[mobythevan]

In Post #4, Z-YA, I think, means that you CAN'T run Alternating, "1-squirt", on MS.

 

Yeah, that could be. I wasn't trying to discredit his post, but just make sure I understood the issue.

[z-ya]

I've never been able to use alternating on an even fire 6 cylinder. My reasoning for this is the firing order:

 

1st and opposed (6)

2nd and opposed (5)

3rd and opposed (4)

 

So with only two injector outputs, you can't fire the injectors like this. I've always run sequential with 2 or 3 squirts and a very smooth idle was the result.

 

 

What injector drivers are firing what cylinders? I always drive three with one, and three with the other.

 

OK, I just spent a bunch of time looking at the injector outputs, trigger input, and ignition output of MSn'Extra code on my scope, and it is not making a lot of sense. No matter if I run alternating or simultaneous, the injector outputs alternate. This is going to take more investigation. I'll let you know what I find out.

[Gavin]

Z-ya, by sequential, I take it you mean simultaneous?

 

I have always used alternating, and heres my reasoning.

 

Although you are correct in pointing out that there are three pairs of cylanders and only two banks, I dont see how simultaneous injections could occur at the same time during each cylanders cycle without six seperate squirts (btw, why not try that?). With three simultaneous squirts, each of these squirts can only occur at exhaust TDC for three cylanders and compression TDC for the other three — Thus creating the largest possible difference in the time the fuel in injected between each pair.

 

With alternating, a squirt will be happening at both Ex TDC and Comp TDC for two pairs of cylanders. The remaining pair would still be receiving two squirts at the same time.

 

Six simultaneous squirts would be the only way of being consistant across all cylanders with MS, as I see it. Am I wrong?

 

 

--- Although I guess in the case of three simultaneous squirts, the extra squirt could help to smooth things out... Whoa, this is complex. So, alternating is the only way of having the timing of the injection uniform across four cylanders, where as the three simultaneous squirts would only allow this for three of them.

So, which is better?

Perhaps it would be best to test this at the dyno day before concluding anything.

 

Sorry for my stream-of-consciousness rant.

 

 

---- Ok sorry now I have to add to it... And please forgive me as I may be straying farther from whats going on if I'm still confusing myself over something..

I was thinking of squirts per REV, but since its squirts per CYCLE, alternating 1-6 and 2-3-4-5 should the only way to get something remotely consistant between cylanders......

 

Although each cylander is ony receiving two seperate squirts over the simultaneous three, there are four squirting events going on in the engine per cycle.

 

Someone tell my why Im still wrong?

[z-ya]

Yes, I meant simultaneous.

 

Simultaneous works just fine. Smooth idle, great performance.

 

I will look into this later as I really want to understand why the MS alternates the injection cycles even in simultaneous mode. When I figure it out I will let everyone know the outcome.

[Gavin]

Simultaneous works just fine. Smooth idle, great performance.

 

I will look into this later as I really want to understand why the MS alternates the injection cycles even in simultaneous mode. When I figure it out I will let everyone know the outcome.

 

Probably because I'm right! jk

I'm intirested as well. I'll try not to have a seizure over this in the meantime.

[z-ya]

I use 2 or three squirts with simultaneous. It doesn't run well with 6 squirts for some reason.

 

My point is that the injector outputs alternate even when in simultaneous mode. I've measured the injector cycle with a scope, and they are the same if in alternating or simultaneous mode. This is where I'm confused. Any insight into why this is the case (besides a bug in the extra code)?

[Gavin]

Trying not to ask the forbidden question... But did you try it with the normal code?

[Brad-ManQ45]

Let me think here:

 

Alternating is set up to fire one injector driver, then the other. Simultaneous is fire both at the same time. Up to you to determine which cylinders on which injector driver. May not make much difference, as at high speeds the injectors are on a lot longer than the valve is open.

 

Alternating will keep fuel pressure steadier. Minimum of 2 pulses per cycle.

 

As I read it, if you are using large injectors (high boost turbo), you are probably better off with simultaneous and 1 squirt per cycle. This keeps the idle pulse as width as small as possible, where alternating with 2 pulses per cycle could be too much fuel at idle.

 

So Turbo'd w/large injectors may need simultaneous and 1 pulse per cycle.

 

Any normally aspirated engine should be better off with alternating and at least 2 pulses per cycle, providing you don't have too large an injector. Turbo'd engines with slightly larger injectors/lower boost would fall in the same category as NA engines.

 

Is there anything wrong with this thinking?

[Gavin]

Heres why I think that approach works fine, as has been proven, but couldn't be theoretically ideal.

 

Well, actually, I dont know how well 1 squirt per cycle would work, but with that aside.

 

Although it is true that the valve is often open for a shorter period than the injector, is the injector necessarily even firing during this time? The mixture sits behind the intake valve for an extremely short period before it opens, and therefore the engine runs just fine this way. However, wouldnt it be ideal for the injector to be opening at the same times for each injector, therefore making the time between the first squirt, second squirt, and valve opening the same for each cylander? Obviously this is true (sequential injection), but the fact is with out three banks we have to make due.

 

If you went from one pulse to two pulses per cycle, MS would simply cut the pulsewidth in half, giving the same amount of fuel. If it does run rich, you should check your Injector Open Time value.