Desperate for some Help With Microsquirt, Beyond Frustrated Options

[JamesM]

I can see the logic of both approaches: focusing on the VE table first vs. the AFR table first.

If you're tuning the VE table, it seems to me, you should be open-loop. You then tune via whatever feedback you have available to you (WBO2, dyno, etc) to bring the VE table to 'perfection'. Then you can enable closed-loop, after populating the AFR table with the values you see while running your final tune.

--OR--

If you're tuning via the AFR table, you run closed-loop from the start and then tune via whatever feedback you have available to you (WBO2, dyno, etc) to bring the AFR table to 'perfection'. Then populate the VE table with the values you see while running your final tune.

But I feel like, from the other responses, that I might be missing something from the picture. James? Jeff? Can you correct or add to my understanding?

You set your AFR targets before using autotune or the log analyzer to adjust the VE table. The AFR targets are what tuning the VE table is attempting to achieve. With closed loop + AFR targets enabled extra data points are generated as the close loop functionality is varying the pulse width to try and hit the target. This generates data for multiple pulse widths under the same target bin. The amount of closed loop correction applied is being recorded in the log along with the resulting O2%. The analyzer/autotune then uses this data to correct your VE table to the most accurate result possible.

Look at it like this:
Say hypothetically you are running with closed loop off, cruising under steady load steady RPM (lets say 65 kpa 3500 rpm on your VE map) this would result in megasquirt looking up the value for that VE bin (call it 85%) and then calculating the injector pulse width for those operating conditions (lets say its a 12ms squirt) lets also say that this bin on the VE table is currently tuned too rich so this 12ms squirt occurring at 65kpa 3500rpm produces a burn of 11:1 AFR. You could drive like that for an hour but you would only wind up with a single data point for that bin.

That data point being:
"A 12ms squirt at 65kp 3500 RPM gives you 11:1 AFR"
You can drive forever like that and it will be the only datapoint the analyzer has to work with. The only conclusion the analyzer can make is "needs to be leaner" but there is no data to say by how much.

Now lets set proper AFR targets and turn closed loop on:
Car still holding at 65kpa 3500rpm Megasquirt does the lookup and produces a 12ms injector pulse that results in an 11:1 burn. That is data point #1 BUT now the closed loop algorithm looks at that output and determines the AFR target is not being hit (lets say the target is 13.5 for cruise) Depending on how you have your closed loop set up after a few misses its going to tweak the pulse width slightly so now we have a data point #2 of 65KP 3500RPM 85%VE with a 3% correction applied produces an 11.8ms pules that results in an 11.2:1 burn. Still not hitting the target, closed loop tweaks again and we get yet another data point in the log. After a short while of running like this we will have one of two results. Either A. Closed loop operation will have resulted in a data point that hits on exactly what we are looking for or B. If the VE bin is further out of tune than the closed loop settings allow for correction we will collect data points on all the run conditions up to that correction limit, but even then the slope of that correction data allows the analyzer to predict what the value should be. the analyzer then kicks you back a new generated table based on the data.

Autotune basically does the same thing just with a slower correction rate than closed loop algorithms are usually set to.

With a single data point you just have to keep guessing at how much to adjust which is fine if you don't mind spending weeks manually dialing in your map. I find data collection and automated processing a way more enjoyable way to do it, not to mention faster and more accurate.


If you change your AFR targets after tuning your VE table you should go back and re-tune your VE table to hit those targets otherwise you are constantly depending on closed loop operation to hit them which is slower and not as accurate as a properly tuned VE table. It puts you at risk of being outside your closed loop limits and should your O2 sensor crap out you will be running out of tune. Basically the goal is to get your VE table to a point that the closed loop algorithm never has to do anything. You know your tune is dialed in when you can run a datalog through the analyzer and have it make minimal to no changes based on the data provided.

[Mblizzard]

Thanks to some very sound advice and guidance above and beyond my wildest expectations. I got to drive the car! Still have a few bugs to work out but overall proforem very well. I think there is more to fix and tune but i can say that even in this less than perfect state this systems performs better than the stock system.

Got to recheck for vac leaks, get the idle control valve set, and revise the AFR and VE tables to fill in a few gaps.

Seems to be wandering just a bit on the AFR at times and i have a few values in the current table that just don't work. Going to try and import a table James provided. Thank you sir!

[BeatNavy]

Congratulations, Mike! Just in time for Okteenerfest. I know it's been a long haul, so I'm glad you're almost there. I'm following behind you at some point on the Microsquirt path, but I'm having someone else do most of the hard work. Still, I followed this with great interest. Enjoy! (IMG:style_emoticons/default/beerchug.gif)

[LowBridge]

very cool... and congrats on the milestone!

[jimkelly]

congratulations ARE in order (IMG:style_emoticons/default/thumb3d.gif)

Thanks to some very sound advice and guidance above and beyond my wildest expectations. I got to drive the car! Still have a few bugs to work out but overall proforem very well. I think there is more to fix and tune but i can say that even in this less than perfect state this systems performs better than the stock system.

Got to recheck for vac leaks, get the idle control valve set, and revise the AFR and VE tables to fill in a few gaps.

Seems to be wandering just a bit on the AFR at times and i have a few values in the current table that just don't work. Going to try and import a table James provided. Thank you sir!

[76-914]

(IMG:style_emoticons/default/agree.gif) And thx to James for posting again. I always enjoyed reading your posts James. Even if it doesn't apply to what I'm running. I'm an info freak. (IMG:style_emoticons/default/biggrin.gif)

[Montreal914]

Congrats! (IMG:style_emoticons/default/smilie_pokal.gif)

Enjoy the ride (IMG:style_emoticons/default/driving.gif)

[JamesM]

(IMG:style_emoticons/default/agree.gif) And thx to James for posting again. I always enjoyed reading your posts James. Even if it doesn't apply to what I'm running. I'm an info freak. (IMG:style_emoticons/default/biggrin.gif)

Just glad I could help get another 914 successfully squirted. There is so much to learn with the system and steep learning curve to boot that many get frustrated some to the point of throwing in the towel. I hate to see that happen because if you can make it through the install its always worth it in the end!

[JamesM]

Thanks to some very sound advice and guidance above and beyond my wildest expectations. I got to drive the car! Still have a few bugs to work out but overall proforem very well. I think there is more to fix and tune but i can say that even in this less than perfect state this systems performs better than the stock system.

Got to recheck for vac leaks, get the idle control valve set, and revise the AFR and VE tables to fill in a few gaps.

Seems to be wandering just a bit on the AFR at times and i have a few values in the current table that just don't work. Going to try and import a table James provided. Thank you sir!

The VE table will still need a lot of work especially in the upper range. The change I made to the RPM bins should make that a little easier. I didnt touch the tune, just the scale.

The idle wandering you you may be able to work out just by spending more time on that area, if not a trick I like to do to control idle better is to bracket the RPM bins around your target idle speed. Say you want to set your idle to 950 RPM you can set one of the RPM columns to 800 and the next one at 1200, then set the VE values in both columns the same. What this does is ensure there is a constant VE value for the entire range the car idles in. Otherwise you can experience sort of a runwaway condition at idle. The area between two VE bins is interpolated so if that interpolation creates a slope your idle can be somewhat unpredictable. Bracketing the RPM range with the same values ensures there is no slope for the idle to climb up.

Now you get to the fun part, the never ending quest for a perfect VE table! (IMG:style_emoticons/default/smile.gif)

Given your timing control is mechanical you will probably find you will be unable to get 100% consistant results with the VE table. Timing affects fuel needs and there will always be some variance as to when the advance is coming on. Just as long as your "close" is landing somewhere between 12.5-13.5 AFR in the mid rpm range you should be good. Of course I know you want to go to full ignition control somewhere down the line as that is where the extra power is hiding!

[Mblizzard]

James

Incorporated your changes and I have a car that seems to run quite well. An amazing difference! Need to back out the timing a few degres but ran great on a 10 mile drive tonight.

Can't wait to add ignition control!

[ndfrigi]

Hi Mike, congratulation for making your megasquirt run well after a long patience!
Sorry if I have to hijack your thread, I've been wanting to ask your help or members help on this thread since it is related but I just waited till your issue is fix before asking some help.
Is there a way you can help us make a 71 1.7 megasquirt run after engine rebuilt?Actually it was running before the engine rebuild and after installing back the engine and the megasquirt II system, we are able to run it on idle but hesitation when we tried to rev it. We thought the megasquirt need some tuning since the engine has been rebuilt. Well, we (Bob-new owner) called Diyautotune and they suggested Bob to buy the updated software, so he did bought it and after installing the software to his laptop and hooked it to the car, a new project was requested and now the old project or old program was deleted. Now totally car won't run. Customer support from diyautotune is not helping at all. Just a little history of the car. I bought the car running 3 years ago except with broken rear suspension console. and after fixing the suspension, Bob bought it from me and he drove it for a few months until it needed engine rebuild. So basically we have no idea how the megasquirt system installed. The good thing only is that I acquired the car with running megasquirt.

[ndfrigi]

[JeffBowlsby]

"...i can say that even in this less than perfect state this systems performs better than the stock system"

How so? Specifically.

[JamesM]

"...i can say that even in this less than perfect state this systems performs better than the stock system"

How so? Specifically.

(IMG:style_emoticons/default/poke.gif)
uh oh, here we go...

[JeffBowlsby]

Please do not misunderstand my question, I am an inquisitive person and only seek accurate information, not to start a heated debate. The question is purely rational and not subjective. When a bold claim like that is made it requires justification otherwise the myth that D-Jet is somehow problematic/flawed/inefficient/etc. continues without justification. I have always run D-Jet cars and find them to have no issues and terrific. No doubt other FI systems have their benefits. We have street cars here, not high performance, highly sensitive machines requiring the minutia to be exactly perfect.

From my perspective, any quality made, appropriate to the engine, properly adjusted FI system is as good as another in terms of how the engine performs and functions. With that understanding no FI system will perform significantly better/worse/differently than another, will not be more responsive/give more power/better mileage etc. The best FI system just feeds the engine what it needs and as long as it does that well, whats the difference?

Show us the justification of the above claim or qualify/recant the broad generalization. Its a fair question.

[timothy_nd28]

2 quick benefits over the stock Djet setup would be the ability of having sequential vs batch injection. This would help for a smoother idle, perhaps a lower stable idle. The other benefit is readily available and cheap replacement parts.

[Mblizzard]

Would be happy to help however I can!

[Mblizzard]

Please do not misunderstand my question, I am an inquisitive person and only seek accurate information, not to start a heated debate. The question is purely rational and not subjective. When a bold claim like that is made it requires justification otherwise the myth that D-Jet is somehow problematic/flawed/inefficient/etc. continues without justification. I have always run D-Jet cars and find them to have no issues and terrific. No doubt other FI systems have their benefits. We have street cars here, not high performance, highly sensitive machines requiring the minutia to be exactly perfect.

From my perspective, any quality made, appropriate to the engine, properly adjusted FI system is as good as another in terms of how the engine performs and functions. With that understanding no FI system will perform significantly better/worse/differently than another, will not be more responsive/give more power/better mileage etc. The best FI system just feeds the engine what it needs and as long as it does that well, whats the difference?

Show us the justification of the above claim or qualify/recant the broad generalization. Its a fair question.

Very valid.

First, I think you read too much into my statement. I never claimed better 0 to 60 times, more power, or a higher top speed. My performance reference is to the fuel system not the car.

The D-Jet is neither perfect or seriously flawed. But it is limited in what it can control and the changes it can make. When it comes to keeping an engine within the most desirable operational parameters, modern systems are more flexible, capable of monitoring and controlling more parameters, and have a more realistic capacity to perform better at operating the fuel system over all conditions than the D-Jet even on a stock engine. Additionally, the improvements in modern sensors, the accuracy of the sensors, their durability, and the ability of the ECU to make decisions based on more data results in a very real step up in the performance level of the modern fuel system over the D-Jet.

First as we all know, the stock system lacks sufficient feedback to accurately determine the impact of changes the ECU made had on the engine. If the parameters called for a specific condition the D-Jet blindly supplies fuel for that condition regardless of how it impacts the engine. Regardless of loving or hating the stock system adding an O2 sensor that provides actual feedback to the ECU allowing it to determine the impacts of changes made is a step up in performance of the fuel system.

Next, being able to accurately adjust the various ECU parameters to meet your specific engine requirements directly results in better performance. You very accurately acknowledged it is essential for any fuel control system to be properly adjusted to the engine. I have 96mm pistons, big valve heads, performance exhaust, matched injectors, and electronic ignition. Each of these required adjustment to the D-jet system to account for the change. My ability to adjust the old system to account for these changes was limited and very difficult to accomplish. Adjusting a MPS to account for a engine modification requires a Zen like level of commitment.

I removed a functioning D-Jet system from this car. It is in a box and I will keep it. It worked and performed well. But it was clear based on AFR readings, that there were times and conditions because of my settings and my engine modifications, where it was documented that the fuel system was not performing well. Under certain conditions it was extremely rich (in the 10's) and other times it would be way too lean. Regardless of adjustments made to the stock system it was very difficult for me to reach a state where I had reasonably consistency across the range of engine conditions. I simply had to settle for a level of adjustment that worked reasonably well. It is my opinion that settling did not allow me to take full advantage of my modifications.

With the stock system I struggled to control AFR, cylinder head temperatures, timing, start-up, and other issues. While it has been a bit of a pain, with the new system I can adjust it so well that I can have all of my parameters in the ranges I want under the conditions that I want to specify.

For those few reasons above I think my bold statement about the performance of the fuel system is supportable. I am sure there are some numbers out there from Dyno testing and such that may be able to support higher HP or faster 0 to 60 times but that was never part of my statement.

[poorsche914]

(IMG:style_emoticons/default/agree.gif)

Will be looking at your system closely. Would like to put something similar on my Raby 2056 in place of the carbs.

(IMG:style_emoticons/default/driving.gif)

[Mblizzard]

(IMG:style_emoticons/default/agree.gif)

Will be looking at your system closely. Would like to put something similar on my Raby 2056 in place of the carbs.

(IMG:style_emoticons/default/driving.gif)

I think that adding FI and ignition control would really make your engine more drivable.

I have mine set up so that it is linked by Bluetooth to a tablet. Using MS Droid I have real-time display of parameters and I can change parameters relatively easily and have multiple tunes available.