shauer's MS3X Beta Testing

[shauer]

Thanks, I can't take credit for much of this as I pulled it together from several sources already out there.

Some of the information I have located has been on web sites that deal with the "high end" injection systems that all appear to use end of pulse timing exclusively so those folks are always doing this pulse width to crank angle conversion to get the short pulses centered. I might play with a spreadsheet over the weekend to help calculate end times that center the short pulses where I want them without the need to hand calculate each point.

I have been looking at the calculations a little more and it looks like you could use middle timing only at the small pulse widths in this application of injection timing.

One example to illustrate this is that at 4000 RPM and WOT my pulse widths are approximately 14ms. That duration injection pulse consumes about 336 degrees of crank rotation. I think it is impractical to use middle pulse timing for such a long duration injection event.

I'm thinking I can get away with centering the injection event on the intake cam lobe up to approximately 4000 RPM and a 4 to 5 ms pulse. That would be between 96 and 120 crank degrees. After that I suspect I want to just ensure the injection pulse ends within the intake stroke and let start time fall where it needs to.

Of course all of this is based on a lot of guess work and assumptions, but my engine does feel like I am on the right track.

[racingmini_mtl]

It is interesting indeed and I'm glad it's my fault.

It will also be interesting to get more data from other engine configurations with different intake types and injector positions to see if they get similar results or if there is a change in the behaviour. That might be why there seems to be so many different ways to view this. Or it might simply be that some don't quite understand it and ignore things like transit time.

Jean

[shauer]

Yes, more data from other engines is absolutely needed.

I have an idea on transit time. Not sure it holds true or not. I'm a computer/software engineer and only know enough about some of this other stuff to be really dangerous...

If you ensure that all the fuel for an intake stroke is injected into the runner early enough into the intake stroke to ensure that the piston will draw in more air volume than exists between the injector and intake valve after the completion of the injection, would it be true that transit time would not be an issue? I'm picturing a cloud of fuel vapor in the intake runner "along for the ride" on the intake air stream. As long as the piston sucks more air volume than exists between the injector and intake valve then all that cloud of fuel should also be sucked in, correct?

[racingmini_mtl]

If you ensure that all the fuel for an intake stroke is injected into the runner early enough into the intake stroke to ensure that the piston will draw in more air volume than exists between the injector and intake valve after the completion of the injection, would it be true that transit time would not be an issue? I'm picturing a cloud of fuel vapor in the intake runner "along for the ride" on the intake air stream. As long as the piston sucks more air volume than exists between the injector and intake valve then all that cloud of fuel should also be sucked in, correct?

What you describe there is basically batch injection. Well not exactly because you're injecting between intake events but that ignores the vaporizing of the fuel which is one of the major aspects influencing the perfect injection timing at least from my understanding. Inject sooner and the fuel vaporizes more before entering the cylinder and takes more volume (therefore decreasing the air volume and mass) but will likely burn more completely. Inject later (but still soon enough to get the whole charge to the cylinder) and the fuel stays in droplets with more air mass going to the cylinder with more of the fuel vaporization taking place in the cylinder resulting in a more powerful charge but with maybe a slightly less efficient or complete burn.

So you do need to take the transit time into consideration to really optimize this for either power or economy. Otherwise you have no idea what the fuel charge is doing. Of course, as you mentioned, the larger the duty cycle the less exact timing will have an influence due to the small amount of time not injecting.

Jean

[pit_celica]

*EDITED ON 02-15-2011 : I edited this post because I saw an error in the previous excel file. I've rebuilt it and I've attached the new file. If you have downloaded this file before 02-15-2011, please delete it and use this one instead.*

*EDITED ON 09-28-2014 : New file location. Now in my DropBox public folder. See link in the post.*

I've built a spreadsheet to calculate a 12x12 injection timing table based on these known values :

https://dl.dropboxusercontent.com/u/130 ... _v3.0.xlsx

Intake cam lobe center (crank deg. BTDC)
Intake cam duration (crank deg.)
A 12x12 kPa/RPM injection effective PW table (ms) (needed only if you want to know the mid-pulse timing)

This spreadsheet generate an injection timing table with End-of-pulse and Mid-pulse that are created using these facts :

-you want the end of pulse to end a little before the intake valve open.
-you want the end of pulse to be earlier as RPM increase (about 10° per 1000 RPM until 5000 RPM). (This can be edited with the offsets)
-injection timing vary only with RPM. This means that the spreadsheet do not use kPa values in the calculations. In a column, all values will be the same.

First, edit your RPM and kPa value in the PW table.
Second, edit the offset for each column so that you have a 10° per 1000 RPM increase.
Third, edit the intake cam values that match your engine.
Optional, fill the PW table with some PW value you are seeing when datalogging. You need to do this if you absolutely want mid-of-pulse timing values.

If you have some questions or comments, let me know!

WARNING, this spreadsheet is not tested on an engine, it's a simple 1-hour late-night spreadsheet, use with caution!

Sam

[UnaClocker]

Step 2.. Integrate that spreadsheet into TS so it can ask the questions and fill in the blanks itself.

[shauer]

I've built a spreadsheet to calculate a 6x6 injection timing table based on these known values :

Sam

Wow, thanks!

I will play with this tonight and over the weekend. I'll let you know how it works out.

I have thought up a test strategy for my engine that will take about a week or so to run. I'll use your spreadsheet as a starting point. I will do a few test drives with VEAL set on the "hard" setting for update and get my VE table dialed in. Then I will go through a series of different injection time tables, scaling the base-line table in 10 degree increments positive and negative. I'll repeat the VEAL tune for each timing table change and then tabulate the results. I should be able to see any significant change in efficiency through the changes required to the VE table. Then I can pick the timings from each operating region that resulted in the least amount of fuel required. I expect I will need to go through 3 or 4 tables in each direction from my starting point.

I have already tested this technique on a couple injector timing table changes and it looks like it will work.

I'm really liking VEAL as a way to measure the effects of tuning changes. When you set VEAL to the "hard" setting it is conservative enough to not introduce a lot of "noise" into the VE table and any changes it makes appear to be real changes caused by tuning and not due to other causes.

Another thought would be to make VEAL capable of playing with the injection timing on its own to achieve the lowest VE bin values for a given RPM/load region while maintaining mixture.

[shauer]

Over the past few days I have run 5 different injector timings in an attempt to quantify what effect the injector timing has on my engine and what a good set of values would be for my engine. Here are the details of what I have done and what I think I have learned so far. I hope this technique can be used by others on their engines.

My test method was to set a baseline injector timing. In my case I came up with a timing table based on a lot of assumptions and guess work that has already been described earlier in this thread. I biased the baseline table further advanced than I thought would be optimal, in some cases not completing the injection event until about half way through the intake cycle.

I established a baseline VE table using VEAL set to the "hard" update setting and ran about 3 30 minute drives to get at least the lower load and low to mid RPM region really solid.

Then I started modifying the injector timing table, adding an additional 20 degrees for each new data set. That is an addition 20 degrees BTDC. For each new injector table I ran the same 25 mile circuit which consisted of about 50% highway cruising and 50% stop/go and low speed driving. I deliberately kept the RPMs low and really pushed the low to mid RPM and low to mid load regions of the tune as this is where I expected the benefits from the injection timing. For each run I reset the VE table back to the baseline and then allowed VEAL to do its thing during the test drive. What I captured was the VEAL modified VE table for each injector timing table.

I repeated the above procedure for 20, 40, 60, and 80 additional degrees of injector timing. I ran each test run on the same roads, same driving style, and same weather conditions in an attempt to eliminate as many external variables as possible.

What I found was that there is a subtle, but measurable change in required fuel due to injector timing. This effect is most significant at low RPM and low load and is completely gone in the mid/high RPM and high load regions of the tune. I can now examine these data sets and locate the injector timing that gave me the least fuel required to maintain mixture. In theory this should be the most efficient setting for my engine and should yield the best torque values.

Here are my VE tables from this test.

Baseline table:


+20 degrees:
Looks like something on the 60% load row between 2000 and 2700 RPM


+40 degrees:
The low load region between 2000 and 2700 RPM shows some measurable improvements


+60 degrees:
The 70% load row between 1300 and 2000 RPM might be interesting on this setting


+80 degrees:
Definitely gone beyond optimal, richer mixtures required in the entire low RPM / low load region


I'm still pulling together a composite timing table from these 5 different runs but it looks like data from the +40 and +60 runs will have the most valuable settings for my engine. If you compare the leanest to the richest values for a few of the VE bins across the 5 runs, there is up to a 10% change in required fuel caused for the most part from injector timing. Most changes were in the 3% to 5% range.

I performed these test drives with the laptop closed so I could not see what VEAL was doing, I did notice a perceptible improvement in the engine on the +40, +60, and +80 runs. The baseline and +20 runs were the roughest running runs.

My next step is to create the new injector timing table and do several test drives with VEAL and see if the changes I saw in the single test drives hold or not.

The optimal end of injection times on my engine appear to be fairly early in the intake cycle, between 300 and 330 degrees BTDC.

[Tjabo]

Awesome data gathering! ! !

Subscribed.

[prof315]

Awesome data gathering! ! !

Subscribed.

Agreed! I'm looking forward to using this methodology on a turbo engine when Peter Florance finishes fixing my boards. It'll be interesting to see what effect if any forced induction has on best injection timing.

[Tjabo]

Yeah, that will be VERY interesting. I guess my first inclination is that it will be like the high kPa, high RPM area only more so, i.e. not much difference. The injection timing seems to be most important where you have relatively low velocities in the intake port, and really short injection events. But like I said, that is just my first blush guess, and I expect to be wrong about most things! LOL. . .

Thad

[Activate]

Replying on a old mail.

I want to try it also and I have dowloaded the Excel file.

I have these Cam info from my cam :

Duration at 50 intake 208 exhaust 212
Lobe lift .9219 .3219
Separation 113
Duration at 006 256 260
Intake lobe 111


I don't know where I must put in witch value?

The engine is running on Propane with a supercharger at 8 PSI.

Thanks and greetings,


Erik.

[pit_celica]

This cam info isn't complete. You need to know when the intake valve is opening when referenced to TDC. By example, my intake valve open 7° before exhaust TDC (or 367° before compression TDC) and have a duration of 240°, so the intake valve is closed at 127° before compression TDC. All the cam input in my spreadsheet are in degree before compression TDC.

Sam

[Activate]

MMmhh that info isn't on the card with the cam.....

[Breastfed]

Did I miss this where can I DL the xls spreadsheet ...I dont see any attached files

Thanks
Breastfed

[wrenchdad]

Kind of wondering about the file myself??

wd

[pit_celica]

I uploaded the file on my dropbox. Link is is in my post above. Sorry for this. I never tried to fine tuning this spreadsheet. Try it and let me know how far from the truth it is right now.

Sam

[wrenchdad]

Thanks!

wd

[bender4601]

Here is another spread sheet.. NOT specific to megasquirt. Specific to a Ford A9L .. Could be worth a look...