injector timing map? -350 what gives?

[savagerocco]

Injector timing map? All set to -350 what is this for, why would we mess with it? Just curious as to what and why.

[gurov]

it's for sequential setups and placing start/middle/end of injection cycle at a specific point in the crank rotation. if you have a preference of spraying open/opening/closed valve, this would be the place to do it.

-350 is prolly some default value.

[muythaibxr]

Yeah, it's the same as saying 360, or 10 degrees BTDC on the end of the exhaust stroke/beginning of intake stroke.

EDIT: Oops, this should've said 370 not 360.

Ken

[savagerocco]

Ok, I am fully sequntial, I just didn't find anything in the documentation as what to do with it. I guess that will be filled in later as we go...

[muythaibxr]

Yep, it's on my list of things to document.

Since sequential injection is pretty new to us as well, that section of the docs is likely to change quite a bit as we get more experience tuning it.

Ken

[myk777]

I've been playing with this lately and trying to read up on the subject. Anyone have any good tips for tuning or any good links for reading material. I've only been able to tweak with the idle settings and my motor likes 210 which is placing the injection in an open intake valve (ignoring any transit times), this produces the highest idle rpm/lowest AFR. It was interesting that there are values that the motor absolutely hates, barely runs etc... I've read that it doesn't make much difference at WOT, but that low and part throttle areas can see a benefit. My motor is a single cylinder, itb, big cams, etc...

[jsmcortina]

Even at WOT it makes a difference. Maybe 1% power.

James

[braineack]

here's my map:

is it ideal? dunno.

I started at 375 static since that's 10* before my intake valve opens, which seems to be the accepted starting point. I built my map around theory and was actually able to pull some fuel out of most my VE table. At 900 rpm it takes 4.629 milliseconds for the crank to travel 25 degrees from 10 degrees before TDC to 15 degrees after TDC. At 6,000 rpm this movement takes just 0.694 milliseconds. Since it takes the same amount of time for the injectors to open and then squirt fuel, you alter the injection timing, much like ignition and the position of the flame front, to make sure your fuel ends up exactly where/when you want it at a given rpm/load. Typically you want it to end up in front of the intake valve just before it opens.

[preston]

This thread is good:

http://msextra.com/forums/viewtopic.php ... 4007a1815b

I've played with it a bit at idle on my V8, and so far it seems to idle worse when I change it from -350 in either diection. Haven't tried it driving or been very scientific about it though.

Question - I get confused with the -350 which is 350 degrees ATDC, or 370 btdc. CAn I switch the values in this table to 370 with no ill effects ? I understand you don't want to swap from - to + values in adjacent cells. I tried switching relevant cells to +370 but it seemed to run worse, although like I said it seemed like every thing I changed in this table degraded or had no effect on idle anyway. But if I play with it more, its easier for me to understand -350 as 370. Then 380 means injecting earlier before the intake stroke, +350 means injecting later in this case 10 degress into the intake storke. Does this matter ? Does it need to be in ATDC ie negative degrees to function properlY ?

[hassmaschine]

what about injecting into an open valve at idle?

I haven't used anything yet since MS3 isn't in my car yet, but this is a preliminary map I've come up with, injecting into an open valve at idle and then before the valve of course everywhere else:

(end of squirt timing)

I suppose I should develop another map that doesn't inject into an open valve and try both..

there's also good info here:
http://www.extraefi.co.uk/Seq_MS3.html
http://www.extraefi.co.uk/sequential_fuel.html

which I used to develop my own timing graph so I could wrap my mind around it:
http://www.325ix.com/megasquirt/2010/Me ... G-FULL.png

[preston]

braineack, are you using "injector angle represents end of squirt" with this table ?

[myk777]

Here is my cam profiles and the red line indicates the end of injection angle where is idles the best/lowest AFR. This is clearly injecting into an open intake valve, the pulse width at idle is 2.3ms. This engine idles at 2k, single cylinder 480cc with 3intake valves and 2 exhaust, its amazing how much a difference the injection angle makes at idle, at some angles it will barely run. I've only played with the fixed timing at idle...interesting stuff for sure. I've read several articles that talk about injecting on a closed valve like several of the charts above are showing that with angles in the 300's+, but my engine just hates that for whatever reason?

FYI - I believe -360 and 360 accomplish the same thing? I tried it and it seemed to.

[preston]

Yes, but that is a very different engine than a V8 loafing over at 800 rpm that's for sure !

[hassmaschine]

yes 360 and -360 are the same thing, but I think 0-720 is a bit easier to follow.

[braineack]

braineack, are you using "injector angle represents end of squirt" with this table ?

yes, sorry I didn't mention it.

[muythaibxr]

Here is my cam profiles and the red line indicates the end of injection angle where is idles the best/lowest AFR. This is clearly injecting into an open intake valve, the pulse width at idle is 2.3ms. This engine idles at 2k, single cylinder 480cc with 3intake valves and 2 exhaust, its amazing how much a difference the injection angle makes at idle, at some angles it will barely run. I've only played with the fixed timing at idle...interesting stuff for sure. I've read several articles that talk about injecting on a closed valve like several of the charts above are showing that with angles in the 300's+, but my engine just hates that for whatever reason?

FYI - I believe -360 and 360 accomplish the same thing? I tried it and it seemed to.

With my rx7 and the corolla, the injection timing at idle barely made any difference at all. Almost no difference that I could tell as far as idle quality and AFR.

both are more responsive when the injection timing is "correct" though.

Ken

[braineack]

I have noticed that when I run seq. that the engine "shakes" more and feels like i need new motor mounts, but in batch it seems to go away. So I've tried numbers all over the place to find a sweet spot it likes...dunno why/how, but no really change in quality at any specific angle.

[muythaibxr]

What increments have you tried in.

The "sweet spot" could be a 5-10 degree difference.

That shake could probably be tuned out a bit with ignition advance too.

Both of my engines run smoother sequentially than batch, but they don't change much when timing is changed.

Ken

[braineack]

yeah, I don't even know how to explain it. It could be in my head for realz. Maybe I can show you one day. We are all going back to York on Nov 13th if you're game.

[muythaibxr]

Will have to see, having surgery on my rotator cuff at the end of Oct so not sure how long I'm not going to be able to drive after that.

I'll be in a sling till Dec.

Ken