problem with injection timing

[dontz125]

8hp = 1.33% of 600hp...

[Wergilius]

yes the gains in hp is small and not the reason

I hope for more even EGT and AFR since i noticed much lower EGT and AFR on cyl 4 compared to cyl 1.

But would it also be more HP they are very welcome as well

[pit_celica]

Nice thread.

Some months ago, I did a spreadsheet to build an injection timing table based off the intake cam informations :

http://www.msextra.com/forums/viewtopic ... 40#p250356

I've used the injection timing map without any evident problems (end-of pulse for me). Read the entire post for an how-to about this spreadsheet.

Let me know if you need more info!

Sam

[piledriver]

Nice spreadsheet, but I think it may need an additional input for injector placement or something.

I tried the calculated numbers, but they (for the first time) magically found that "bad" spot in injection timing at idle, mixture adjustments were only marginally helpful, and it needed a lot more fuel at 153 BTDC than the -240 I had it at previously across the board.

I used the same start/end spread and retarded the whole table so as to -150>0 (just using the L&R columns and scaling, as MS2 only has 6x6 for injector timing) and the idle mix/idle speed>off idle>light cruise performance jumped noticeably.

With the numbers from the spreadsheet, mixture changes had little effect, and I had to up the mix about 10% just to run ~anywhere.
Once I shifted away from these, mix adjustment "feel" started working normally.

I hope to start attempting to actually work through truly optimizing the injector (and light load ignition) timing at some point.

I have tried it only shooting while the air is moving, and only while the valve is closed... for idle/off idle/light cruise performance, it seems it likes as much resident time as you can give it on the back of the valve.

(considering switching to timing from the beginning of pulse for this reason, in spite of the pile of expert opinion that says otherwise)

[Peter Florance]

(considering switching to timing from the beginning of pulse for this reason, in spite of the pile of expert opinion that says otherwise)

I'd give yourself more credit. Your work seems to agree with research I've read.

I always felt I wanted to specify end of cycle when cranking, but the MS2Sequencer I'm beta-testing only specifies beginning of injection and it starts just about as quickly as any other MS system I've used. So my concerns are probably not valid re: cranking.

[tpsretard]

i have what has got to be the most screwed up looking injection table in the world, but it works

injection timing.PNG

I guess i should describe why thinking a little.
The low valve at low rpm and low vacuum is for throttle response, now it is a bit of a give and take, to low and the idle will hunt, as it is now every so often there is a little hunt, not bad, but there is.

It then goes back up and this is for cruising and to make sure there is no stumbles or missing, but i have to run a lot of EAE in this area, then on boost if i run anything other than 360 i have to increase my pw to keep the AFR's stable.

The engine is an EJ20k Subaru engine, and yes i do get close to 300kpa.

The main perpous for this post of mine is to remind you every engine type is different and every install is different, hard to get a excel sheet to get it right, just like timing, it can be used as a guide, but it will not be right, not out the box at least.

[hassmaschine]

I think if we got the physics of what is actually happening down (transit time, evaporation, pressure effects, velocity effects, etc. etc.), then we could come up with a basic set of assumptions that should at least get close - engines might react a bit differently, but the physics are always the same.

At least until this thread, it seemed more like wild ass guesses (at least my table was).

[piledriver]

OK, trying to get to sleep I had my my "engine simulator" running in the amusement park of my mind, and I think I figured out my "bad" injection timing (and probably more importantly) why it may be a bad time to spray, by going back to basics.

I was setup with end pulse timing, with the setpoint just after IC, which basically goes like this:

Visualize the otto cycle, and you are coming up on the IC event, at idle... low PW... spray...overlapping the IC event.

OK, at idle/low speed, what's happening? Some of the small shot will go stay in the cylinder, poorly vaporized and or as liquid, as there is no positive air velocity or time to help matters. end result==high% goes out tailpipe.

Some(most?) that IS finely atomized or vaporized already will get burped back out on any practical cam, even stockers.
The remaining "burped back" fuel gets well vaporised somewhere in the port (assuming it didnt get burped all the way back up the pipe, wetting out...), but (most?) of it gets sucked out (or heavily mixed with EGR) at overlap.
End result? Same.

Remember, the compression stroke started many degrees ago, and all that lovely ram tuning is doing you absolutely no favors at all at idle/low speed..
(Even with a rediculously mild stock cam and little overlap, IC is still well past BDC)
At any other time window, you may still lose fuel to overlap, but you have more of a full load to start with.

I'm visualizing straddleing overlap with a low PW to be as bad, but probably not much worse.

The only better time might be to take the shot just before and into the peak velocity of airflow at ~30 ATDC, to give only some burpback (there is a correct term, but forgive me) to overlap and get the most mixing/vaporization time in cylinder.

The only fix, of course is direct injection, I still want to try an air assisted setup possibly firing the air solenoid with the higher res ignition code, using a separate ignition.

[piledriver]

Just did another 80 mile RT commute, outbound started spraying at EVC, corrected it some for 1/2 the trip home, then rest inbound shooting just after IVC.
(into opening vs just closed intake valve) only logging for post analysis in MLV rather than jacking with the VE tables.

Shooting just at IVC, the fuel sits resident in the port for the remainder of the compression, power and exhaust cycles.

I guess I'm old school, I had to draw out the engine cycle chart and add my cam timing to it to really get my head around it.
I'm running a Webcam 73 in a 1.8L VW T4.
Injector tip is ~70mm from back of valve FWI, port is a ~straight shot and ~the whole valve is unobstructed shot from the injector drilling.
Using new ND pico injectors for a 160HP 1100cc Yamaha Jet Ski.

Valve timing: EVO 40ABDC, EVC 4ATDC, IVO 4BTDC, closes 40ABDC. (224 degree@.050, 108LC, ~8.5mm lift at valve)

IIRC that worked out to ~330 and 240 degrees timed at beginning of injection, respectively, with some advance for higher MAP and RPM in the table.
My idle PW is ~4ms, and at 70MPH cruise at ~3200RPM it's ~7ms, 12.3:1 target.

The WBO2 didn't see much different, but it feels like a whole different engine under 3K, and it felt a bit different at 70MPH too.

I still somewhat expected shooting into moving air was better than it was.
The IVC shot drove and idled much better.

I switched to a "flat" 12.3:1 AFR everywhere but idle and drove it a bit the other day with VeAL, so the table was reasonably close to start with using the 153 end injection timing, will do and post post analysis after getting some sleep, but I at last feel I have something of a grip on this now.

The logs are ~1 hour ea, so I'm not sure how big they will be.

[Fabius72]

Hi all. This is a very interesting discussion for me, because I have non finished my bike setup yet: I had some problems and they stop so far.
Last year I wrote a question (read this short thread http://www.msextra.com/forums/viewtopic ... 58#p261258) and pit_celica has shown to me a new point of view (for me).
I hope this will help someone, and I think shauer's methodology is the best way to find better injection table.

Have a nice day.
Fabio.

[piledriver]

Hi all. This is a very interesting discussion for me, because I have non finished my bike setup yet: I had some problems and they stop so far.
Last year I wrote a question (read this short thread http://www.msextra.com/forums/viewtopic ... 58#p261258) and pit_celica has shown to me a new point of view (for me).
I hope this will help someone, and I think shauer's methodology is the best way to find better injection table.

Have a nice day.
Fabio.

I tried that but the WBO2 didn't see squat, which makes sense as it's going to tune to make the AFR setpoint.
If you played with THAT you might get somewhere, or maybe not.

My butt dyno certainly did notice a definite difference between IVO and IVC timings, at least on my "big heads/little cam" setup, an accurate Tq/HP calc in MLV should tell the tale.
(20-30hp with as much noise in the signal currently at ~70% MAP, accelerating at part throttle to 70 MPH in 3rd)

Starting injection ~at IVC, i have a reasonably fuel efficient, snappy motor that pulls hard/clean from any reasonable RPM to redline.
(I can almost dump the clutch in second, tripping "cranking" and it still just pulls itself out of the hole with no throttle, or at WOT)

All else being the same, advancing to start at ~IVO, it's a slug by comparison, and even "switching over" to IVO timing at 4k just makes it trip over its own feet at 4K and above..


"Ending" timing at other timing produced middling results. YMMV. Severely.

[Fabius72]

Hi piledriver
see these two images: (are from a log made before write my thread I shown you, and I have not finished yet because I had some various problems)



On the bottom you can see Injection timing and this is the only thing I changed between the tests: from +270° to -340°

I know, you are right and I forgot to tell "the best way is to go on the dyno but who can't, shauer's methodology is the best home made mode."

Probably our engine are so different, however I hope to go on the bench asap so we can compare all our results!

Please, I know my English is not very good, but what does this mean?
"...YMMV. Severely."
I can't understand a lot of acronyms
Thank you.

Fabio.

[dontz125]

YMMV = Your Mileage May Vary -> your results may be significantly different...

[Vicoor]

On the bottom you can see Injection timing and this is the only thing I changed between the tests: from +270° to -340°

Fabio, go back and look at the beginning of this thread, and the reason I posted. I was having issues with the transition between negative values and positive values. I posted some modified "visual aids" to show how you can eliminated the negative values and just run 0 to 720.

Hope this helps.

[Fabius72]

YMMV = Your Mileage May Vary -> your results may be significantly different...

Thanks dontz125! Now I have understood. Wasn't easy

Fabio, go back and look at the beginning of this thread, and the reason I posted. I was having issues with the transition between negative values and positive values. I posted some modified "visual aids" to show how you can eliminated the negative values and just run 0 to 720.

Hope this helps.

Vicoor, I have already saved on my documentation folder your images you have posted here, some days ago!
I have read all the pages of your thread and I didn't understood that you had tuning problems, but only a bad graph of the injection table.
My friend Luca (how has my same bike and setup) gave me his msq file with VE tables already made to easily begin my tuning.
After few time, last year he has broken the engine and he don't know the really reason yet.
He made some VEAL session with -340° injection timing (20° before the intake valve opens) and all seemed to work fine... but a bad day a piston said bye bye.

http://www.youtube.com/watch?v=PUeyO4lvaeo

http://www.v-max.it/cgi-bin/yabb2/YaBB. ... 4608279/45 (on the middle of the page you can see the piston)

was probably this issue the reason?

However, before stopping my transformation, I put his msq file into my cpu and I tried different injection angles. I noticed very different response of the engine between two timing, and I posted here my question about that.
I don't see the time to run the engine again and try adding 720° to negative number as you told me, to see how the engine runs injecting at IVC!
EDIT: Understood that with a fixed timing (-340 or +380) nothing will change.

Thanks a lot.

Fabio.

[Vicoor]

I wouldn't think injection timing problems would result in engine damage.

If you are running a fixed negative value them you may not notice any problems. The issues I had were engine stumbling during the transition between negative and positive values on the timing table.

[Fabius72]

I wouldn't think injection timing problems would result in engine damage.

Ok, ours is probably a wrong think. We thought that because while I decided to try a fixed End-Of-Pulse 270° (all of fuel sprayed is aspirated, also that part injected at IVC), he put Start-Of-Pulse -340, so at WOT some or a lot of fuel is injected after intake valve closes. Mixture lean? Is this enough to have a single brutal detonation at WOT? I really don't know. I have not much experience and probably this is a very stupid think!

The issues I had were engine stumbling during the transition between negative and positive values on the timing table.

Now I have understood all, thank you.


Another couple of month and I can play again with setup

Fabio.

[Vicoor]

when running at wot and higher rpms, the injector is spraying most of the time and injection timing becomes less of a factor.

If you think about it, when we were running batch fire injection, timing wasn't even a consideration and we were not blowing up engines then.

Victor

[hassmaschine]

when running at wot and higher rpms, the injector is spraying most of the time and injection timing becomes less of a factor.

If you think about it, when we were running batch fire injection, timing wasn't even a consideration and we were not blowing up engines then.

Victor

unless of course, your injectors are sized large enough so that you don't pass a certain duty cycle threshold - then you can time them to your hearts content. at 40% DC and a max PW of about 7ms, I calculated that I can time my injections just fine all the way up to my redline of 7500.

and with modern injectors becoming more efficient/faster, it's possible to oversize them a bit without losing idle quality..

[piledriver]

On my widdy-bitty (currently NA) 1.8 and Yamaha R1 injectors, (actually the marine version) I hit ~35% max.
max rated pressure is 73 psi, I'm running 42... think I have some headroom ;-)