MS-II Simultaneous or Aternating?

[mobythevan]

Double poster and asks forbidden questions

 

 

ha ha, just messin with you

 

 

I could try some different settings on my talon with 850cc injectors on 2.0L engine, but I drive it everyday so I'm gonna hold off until the celica is going then I will try some experiments. I can't even remember on it if I have all four injectors on one bank or 2 on each?? Its been over a year since the install, I have forgotten just about everything on the setup.

[Brad-ManQ45]

We're talking about idling now, and yes, sequential would ideally be the way to go in order to be most efficient and less emissions. But at higher rpms, the injectors are open longer than the valves anyway so it makes much less difference.

 

I agree messing with the injector open time setting, alternating and 2 squirts will net you a bit, but if the injector is large enough, you'd be better off with simultaneous - as long as you have the fuel pump necessary to keep the pressure up!

[Gavin]

We're talking about idling now

 

But at higher rpms, the injectors are open longer than the valves anyway so it makes much less difference.

 

So then wouldnt it matter most when things are heppening more slowly, like at idle?

 

I think people who found a better idle with simultaneous perhaps did not have 1-3-4-6 and 2-5 paired together.

 

 

----- **** me! I meant 1-6 and 2-3-4-5! I thaught they were paired differently...

Im gonna edit that just to not cause confusion.

 

 

-------------------------------------------------

 

Feel free to ignore the crazy person in the corner talking to themself, but heres what Im thinking now-

 

I think three simultaneous injections would actually be ideal, since the cylanders are split in the timing of the squirts, and also because there are three of them to smooth things out. However, this reduces the maximum duty cycle of the injectors. I still think two alternating squirts are better than two simultaneous because the timing of the squirts is much more uniform.

[Brad-ManQ45]

Well, the stock engines do fine with simultaneous squirts - not the BEST for emissions, but still fine.

 

Depending on injector size, alternating can work - especially if you go to 2 injections per cycle.

[cygnusx1]

After spending some time at the MS forums, I think it makes sense for me to run Simultaneous-3 squirts. This will give my injection a nice "resolution" for throttle response. The only pitfall is that the idle pulsewidth might be down around 1.7ms with the 440cc injectors, which is pushing the lower limit of tuneability.

 

By "resolution" I mean that the time between reaction of the throttle plate to the next squirt is small with a high number of squirts/revolution. This theoretically is better for throtle response. Being more of a road-course type of driver, throttle response is important to me for rev matching, and heel & toe.

 

In the case that I may run alternating, I am using both injector banks and will wire cylinders 1,2,3 to Bank1 and 4,5,6 to Bank 2.

[clint78z]

As you mentioned you may run into problems running at those small pulsewidths for idle. 1.7ms-1.0ms for open time gives you .7ms. The resolution may not be good enough for deal with idle changes. Of course you could switch to high res code if you really want to nail it down.

 

So the people who ran alternating how did you wire the banks of injectors??

[cygnusx1]

This is how I read to wire the banks.

 

Firing Order

1-5-3-6-2-4

1-2-1-2-1-2

Bank

 

That puts 1,2,3 on Bank 1 and 4,5,6 on Bank 2. This way the banks alternate after each fire event.

[TrumpetRhapsody]

Hate to bump an old thread, but the search engine isn't feeling very generous tonight.

 

I'm running 2 squirts alternating with 440cc injectors, 7.2 req fuel, and I idle around 1.6-1.8ms pulsewidth with VE values of around 6-10. Not very much wiggle room or resolution down there. Has anybody experimented or come up with something conclusive on this and I'm just missing it?

Edited May 2, 2012 by TrumpetRhapsody

[Zmanco]

Cut Req Fuel iin half and double all the values in the VE table.

 

But I'm surprised at how low your VE values are at idle. I have essentially the same setup as you and run with req fuel = 3.5 and have VE at idle ~80. You may want to check that you have the correct injector opening time for your injectors. If it's set too long, even by a small amount, then you'll have very small VE values at idle. It won't make as much difference under higher load.

[TrumpetRhapsody]

I've always been surprised too, kinda always figured something might not be right but it's always run well enough not to mess with it. Now I'm in the "thinkering with my tune" phase where I start messing with stuff I should just leave alone xD

 

My injector specs are:

Deadtime - .9

Volt Corr - .2

PWM - 30%

Time Thresh - 1.2

PWM Period - 50

 

I've been wary to deviate from the recommended /calculated Req. Fuel, especially since so many others seem to run at the 7.2 level with these injectors, but now i'm thinking it might be worth playing with.

[SleeperZ]

Please keep us up to date with how that works. I will be applying power to my new MS-III maybe as soon as this weekend. I have my 440cc injectors wired in two banks as Cygnusx1 mentioned, and it would be great to have some tested numbers to program in from the start.

[Zmanco]

I've always been surprised too, kinda always figured something might not be right but it's always run well enough not to mess with it. Now I'm in the "thinkering with my tune" phase where I start messing with stuff I should just leave alone xD

 

My injector specs are:

Deadtime - .9

Volt Corr - .2

PWM - 30%

Time Thresh - 1.2

PWM Period - 50

 

I've been wary to deviate from the recommended /calculated Req. Fuel, especially since so many others seem to run at the 7.2 level with these injectors, but now i'm thinking it might be worth playing with.

I'm afraid I can't help you with deadtime as I no longer run PWM, even though I have low impedance injectors. I had repeated issues with the drivers overheating and temporarily shutting down at the track. I added resistors and never had an issue with it again.

 

That said, one way to set deadtime without a scope is to tune a stable idle with 2 squirts, then switch to a single squirt and see if the AFR changes. If you have the dead time set correctly, it won't change. If dead time is too short, then the AFR will go rich. If it's too long, the AFR will go lean.

 

Dividing req fuel by 2 and doubling the VE table (use the TS tools to do this so you don't have to manually edit each cell) will result in exactly the same PW. But you will obviously have double the precision to adjust VE. Try it and see.

[Zmanco]

Please keep us up to date with how that works. I will be applying power to my new MS-III maybe as soon as this weekend. I have my 440cc injectors wired in two banks as Cygnusx1 mentioned, and it would be great to have some tested numbers to program in from the start.

 

Don't forget that unless you and TrumpetRhapsody have the same injectors, it's unlikely that they will have the same dead time.

[TrumpetRhapsody]

You know actually, I do have a scope... I just haven't learned how to use it properly yet xD I'll play with the deadtime first, then give doubling the VE's a try, though my max VE values are already in the 180 range. I wonder if my pw resolution is high enough to warrant doubling the VE resolution... *ponders*

[Zmanco]

If the max VE values are in the 180 range then you cannot double the VE table as the max is 255. But that is also clear evidence that you have the dead time set too long.

 

I also have an old scope, but in order to measure dead time I believe you need a current probe and good ones are not cheap. My method IS cheap, as long as you don't value your time too highly

 

Google the injector part number and "dead time" or maybe "opening time" or "open time" and see what you find. You may get lucky and find someone who has measured the opening time (dead time).

[SleeperZ]

Don't forget that unless you and TrumpetRhapsody have the same injectors, it's unlikely that they will have the same dead time.

I've researched the Supra 7MGTE injectors and have the baseline numbers. With 12V applied, opening time is 1.15mS, at 14V it is 1.05mS. Closing time is 1.1ms. I'm not sure how to get the deadtime with those numbers, it doesn't look like TrumpetRhapsody added them.

 

I am going to try 30% PWM after 50uS.

[macambra]

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.

 

I'm running 440cc high-z injectors simutaneously, and I run best on 3 squirts/cycle. I think that I'm going to rewire mine to 1,5,3-6,2,4 and reset mine to alternating. My idle could still use fine tuning and I think it's because of the drop in fuel pressure-watching the gauge it's all over the place.

[Tennesseejed]

Hate to bump an old thread, but the search engine isn't feeling very generous tonight.

 

I'm running 2 squirts alternating with 440cc injectors, 7.2 req fuel, and I idle around 1.6-1.8ms pulsewidth with VE values of around 6-10. Not very much wiggle room or resolution down there. Has anybody experimented or come up with something conclusive on this and I'm just missing it?

 

I believe that going to two squirts simultaneous will double your PW. 1.6 - 1.8 is pretty short.

 

I experimented with every possible to injector setting (1 simultaneous to six simultaneous) last year while trouble shooting some idle issues. Quite frankly, I found two squirts was best and there was no difference between simultaneous and alternating.

Edited May 3, 2012 by Tennesseejed