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johntrhodes81

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Member #: 11718
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10th Mar, 2018 at 07:36:33pm

Moving the non-Mini content from: http://www.turbominis.co.uk/forums/index.p...id=416587&fr=50

On 10th Mar, 2018 jbelanger said:
Rod, your assumption was correct. The siamese code is limited to a 4 cylinder engine and the 2 additional channels are for staged injection. There may not be an error code thrown if you try an 8 cylinder setup but that still won't work correctly.

Thinking about it, it would be possible to use the MS2 with 4 channels and set it as a 4 cylinder fully sequential injection. That would allow using it as a single pulse setup the same way MS3 is being used. The advantage of using the MS3 is that you don't have to cheat and you can configure it as an 8 cylinder but you do waste half of the injector outputs (but you get the other MS3 features).

Jean


Jean,
Thanks for your helpful reply and recommendation of going MS3X. I assume you meant use high impedance injectors and like the MEMS system use all 8 injector channels but driving only 4 injectors? But I assume that even going the MS3X route won't allow for 8 cylinder sequential injection using 4 injectors plus an additional 4 injectors staged? I assume to do that would require using 2 MS2 setups with them each running half of the engine? Both think it is only a 4 cylinder engine.

However at 25% duty cycle a 1,275 cc/min injector would support the likely power 400 hp from 8 cylinders, similar to 200 hp from a A-series. I guess that with that size injector it wouldn't idle well without major adjustment to fuel pressure which would make tuning tough?

Thanks,
John R.

John R.

jbelanger

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10th Mar, 2018 at 08:52:48pm

John,

Actually, the way the MS3 injection is done is by using only half the injector channels and injecting once at the overlap between the intake events of the 2 cylinders sharing the same port. That's what we call the single pulse injection method because a single pulse fuels both cylinders.

There has been talk about using 2 injector channels per injector as per the MEMS but this is still a work in progress. Paul S would be better placed to elaborate on this.

So in your case that would mean using injector channels A,C,E,G and leaving B,D,F,J disconnected. And the only way to do staged injection would be to use the 2 main board injector drivers in a wet manifold setup; I have no idea how well this would work though.

To do a real sequential staged setup, you could indeed use 2 MS2 setups with one controlling cylinders 1,2,7,8 and the other controlling cylinders 3,4,5,6 (from your firing order). You would have all the flexibility you can want but I don't know how easy/difficult that would make tuning.

Jean

http://www.jbperf.com/

johntrhodes81

16 Posts
Member #: 11718
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10th Mar, 2018 at 10:27:21pm

Thanks that is super helpful. From this it seems like MS3X would definitely be the most straight forward way to do this if staged injection isn't needed.

From researching this board, it seems that 1000cc injectors are the biggest that support decent idle in the A-series. It seems like they support 150 HP so 300 in my application. I would feel safer if I had enough fueling for 400 hp to be safe. But 350 hp is more likely. Has anyone gotten and A-series to idle on 1,275 cc injectors?

Best Regards,
John R.

Rod S

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11th Mar, 2018 at 07:28:40am

On 10th Mar, 2018 johntrhodes81 said:
 Has anyone gotten and A-series to idle on 1,275 cc injectors?

Not that I'm aware of.
If you consider it's only in a true port injection setup using timed injection through open valves that requires such low duty cycles that very large injection capacity is required, the obvious answer becomes staged injection.

I can't remember the exact timeline in the early days of developing the MS2-E siamese code (I wasn't involved right at the beginning) but the addition of allowing the two individual pulses to switch to one long pulse overlapping both valves (the so called hybrid mode) and adding staged injection were the ways of squeezing a little bit more out of small injectors or just adding more injectors.

The hybrid mode actually came about because in the early days we found that if the two individual pulses grew in width to touch each other accidentally they didn't always merge nicely (plus you didn't really know what was happening with close/open times at that point) but it did mean you could have a total duty cycle a bit larger than the "safe" limit for two individual pulses. And staged injection just makes it easier still.

We didn't find out until a fair bit later that switching between two individual pulses and a single long one was what Rover had also done with the MPI MEMS.

Use of an MS3 as pioneered by Paul to just use a single (timed) pulse came later because the MS3 came later....

So given those options on a 4 cylinder there is no need to exceed 1000cc.

Out of the people I'm most aware of doing anything like this (and that includes use of other ECUs which also allow timed injection) I think I'm the only one using 1000cc and that's only because I still haven't completed my staged injection manifold.

My idle is fine but, IMHO, there is more to it that just the injector size - I believe the injector characteristics and drive circuitry play a significant part in their performance at the very low pulse widths you need for idle with large injectors. In our scenarios the idle pulse width is almost certainly going to be in the non-linear range and an area where the manufacturer doesn't even document the performance because you shouldn't be there. But my only real justification for saying that is Graham T borrowed my spare pair of 1000cc injectors and my spare MS2 (different drive circuit to his because my injectors are low-z) a few months ago and did a comparison against his (slightly smaller) high-z ones. But it's all rather subjective, no empirical data, plus different manifold, different cam, lots of other differences, how good do you need your idle to be ???

Final thing to bear in mind before I ramble on too much, there are very few people doing this (timed port injection on siamese ports) - most people take the easier option of some sort of throttle body/wet manifold/electronic carb, whatever you want to call it and just live with charge robbing, just like with a carburettor. And when you use that kind of setup you're back to 85-90% duty cycle and "normal" size injectors.

Schrödinger's cat - so which one am I ???

johntrhodes81

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Member #: 11718
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11th Mar, 2018 at 03:11:51pm

Rod S,

Thanks for the reply. I understand what you are saying to be that 1000cc injectors idle due to being low z. And if high z something less like the 875cc that someone else is using is probably better.

Jean, was saying that the staged injectors for my MS3X setup would need to be a wet manifold setup. But the extra fuel needed isn't much and I don't know how often it will get used, just don't want a setup that could go lean up top and break something.

Thanks,
John R.

johntrhodes81

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11th Mar, 2018 at 04:14:13pm

Rod S, I was reading some of you other posts on idle, what spray pattern are your injectors?

Thanks,
John R.

Rod S

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12th Mar, 2018 at 02:46:54pm

On 11th Mar, 2018 johntrhodes81 said:
Rod S, I was reading some of you other posts on idle, what spray pattern are your injectors?

I'll let you know what info I have later in the week when I'm back home - I'm the other side of the Irish Sea at the moment (seeing relatives) and no access to my files (and very little access to the internet...).

Schrödinger's cat - so which one am I ???

johntrhodes81

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Member #: 11718
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13th Mar, 2018 at 11:26:42am

Jean,
If I understand the MS3X setup correctly. Basically the ECU thinks the engine is 2x the actual size, but half the injector outputs aren't used? Basically for a 1275cc. MS3X thinks it is a 2550cc 4 cylinder but 2 injector outputs aren't used?

Thanks,
John
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