problem with injection timing

[davcol]

Hi,
What i have experience with all the injection timing talks is that only the basic really works for me and i am sure thats the same for many of you others out there, all that fancy talks just don't seems to work.
How it works for me is just like in the beginning of the introduction of the injection timing to ms by Jean with the basic setup, you just have your VE table nicely tuned then with the injection table at engine idle you start off with 360 degrees of crankshaft rotation , you will see the the air/fuel ratio gets pretty leaned if you have a wideband system , from there you just advance in increments of 5degrees only till your a/f ratio start to get rich that means you are heading in the right direction , just keep going only till there is no changes in the ratio , then go back till it just starts to get lean again thats where you stop, that would be your engine sweet spot, from there you can adjust the rest of the RPM in increments of 10degrees, I believe this would work for many.

[Timmerklits]

I have played with the values to on my chevrolet 7.4 l semi sequention lpg injectors.

I have it running always at 90 degrees, no problems, changing the degrees didn't change much at idle, just a little bit leaner is some ways.

As allready said I don't think it will change much at wot, or semi loads, because the injectors are spraying most of the time.

[piledriver]

I have played with the values to on my chevrolet 7.4 l semi sequention lpg injectors.

I have it running always at 90 degrees, no problems, changing the degrees didn't change much at idle, just a little bit leaner is some ways.

As already said I don't think it will change much at wot, or semi loads, because the injectors are spraying most of the time.

Agreed, it will likely only make a difference with low duty cycle setups.
It does make a very noticeable difference on my setup but max duty cycle is <30%.

[Timmerklits]

Hello,

Because of to high current reasons, I have put 8 resistors for my lpg injectors.

Now playing around with the injection timing makes a lot more difference.
From 90 to -40 the rpm goes 200 more at ilde. During driving i don't feel that much difference.

[piledriver]

Just posting up my inj timing table , "start injection" just after intakes close on a mild cam.
All of the older images and uploaded bits seem to have been borken recently.

[jsmcortina]

Just posting up my inj timing table , "start injection" just after intakes close on a mild cam.
All of the older images and uploaded bits seem to have been borken recently.

We have to purge old images and datalogs to keep data storage in check.

James

[slyrye]

Just wanna share this "Dynolog" timing diagram and hope we, the Megasquirt community can come up with such valve events Timing Calculator tool really really handy..!

[racingmini_mtl]

This diagram does look nice but unfortunately, it does give you the information you think it does. Without the transport delay (or whatever you call the time it takes for the fuel to go from the injector to the cylinder), the injection timing with respect to the cam timing is pretty much meaningless. And what's worse is that for most engines, it will be impossible for almost anyone to know what the delay is. It will also change with respect to load and RPM.

So it would look nice but it would not provide any meaningful information.

Jean

[slyrye]

This diagram does look nice but unfortunately, it does give you the information you think it does. Without the transport delay (or whatever you call the time it takes for the fuel to go from the injector to the cylinder), the injection timing with respect to the cam timing is pretty much meaningless. And what's worse is that for most engines, it will be impossible for almost anyone to know what the delay is. It will also change with respect to load and RPM.

So it would look nice but it would not provide any meaningful information.

Jean

I chose to differ, if you look closely on the right side there are sliders that you can tweak parameters to somehow come up close to whatever you are expecting for... I fully understand it would not give you the dead exact calculation that's virtually impossible "newtonian physics" an idea somehow

[racingmini_mtl]

Ok. Then tell me how you know that what you are getting is what you are seeing on such a diagram. For example if you want to inject on a closed valve, how do you know that you actually are doing that if you don't know the transport delay? There is absolutely nothing in the sensors you have on an engine that will tell you when the fuel gets to the cylinder either directly or indirectly.

So the only thing you know is when the fuel is leaving the injector. But since you don't know the transport delay and there is no way to actually know what this delay is, such a diagram not only gives you no real information but gives you a false sense of knowing where the fuel is going. And this is worse than actually just guessing and trying the whole range to see what gives the best results on your specific engine setup.

In my opinion, this is mostly bling and can actually be counterproductive if you don't know it.

Jean

[piledriver]

The excel spreadsheet posted here years ago did essentially the same calculations...

Metal gets the only vote, you have to try it and see what it likes best. You get no vote.

[slyrye]

Ok. Then tell me how you know that what you are getting is what you are seeing on such a diagram. For example if you want to inject on a closed valve, how do you know that you actually are doing that if you don't know the transport delay? There is absolutely nothing in the sensors you have on an engine that will tell you when the fuel gets to the cylinder either directly or indirectly.

So the only thing you know is when the fuel is leaving the injector. But since you don't know the transport delay and there is no way to actually know what this delay is, such a diagram not only gives you no real information but gives you a false sense of knowing where the fuel is going. And this is worse than actually just guessing and trying the whole range to see what gives the best results on your specific engine setup.

In my opinion, this is mostly bling and can actually be counterproductive if you don't know it.

Jean

You got a point there, but isn't that what "TUNING" is for? to mitigate on the uncertainty after all the theoretical calculations are presented? let me reiterate that this is a screenshot of a tool I sourced from a DYNOMOMETER software. There are variables that can be tweaked for the sake of well "TWEAKING" and in no reason they would spend their precious time developing such software tool if it is counter-productive...! only in innovation that we can truly expect a revolution...!

[Peter Florance]

Ok. Then tell me how you know that what you are getting is what you are seeing on such a diagram. For example if you want to inject on a closed valve, how do you know that you actually are doing that if you don't know the transport delay? There is absolutely nothing in the sensors you have on an engine that will tell you when the fuel gets to the cylinder either directly or indirectly.

So the only thing you know is when the fuel is leaving the injector. But since you don't know the transport delay and there is no way to actually know what this delay is, such a diagram not only gives you no real information but gives you a false sense of knowing where the fuel is going. And this is worse than actually just guessing and trying the whole range to see what gives the best results on your specific engine setup.

In my opinion, this is mostly bling and can actually be counterproductive if you don't know it.

Jean

You got a point there, but isn't that what "TUNING" is for? to mitigate on the uncertainty after all the theoretical calculations are presented? let me reiterate that this is a screenshot of a tool I sourced from a DYNOMOMETER software. There are variables that can be tweaked for the sake of well "TWEAKING" and in no reason they would spend their precious time developing such software tool if it is counter-productive...! only in innovation that we can truly expect a revolution...!

I always test.

Have pretty good starting table (end of squirt) but no substitute for dyno testing, sweeping the values.