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> Going to Megasquirt, More questions
Montreal914
post Sep 12 2021, 12:25 PM
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For ITBs, you have probably read that some people have all 4 vacuum ports on the manifolds connected to a small plenum box, then a line from that box to the modern MPS.

Also, there are 3 typical "GM" MPS pressure available: 1, 2, and 3psi if I recall. All can be used but I believe 1 psi will be more accurate, but I am all going from memory here, so I might be completely off... (IMG:style_emoticons/default/dry.gif) I am sure the real knowledgeable guys will comment. (IMG:style_emoticons/default/biggrin.gif)

As others have posted before, you can find all sorts of China made IDF style ITBs and other TBs here:

https://www.aliexpress.com/wholesale?catId=...f+throttle+body


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bbrock
post Sep 13 2021, 08:26 AM
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Good to know about the MAP sensors. Looks like most megasquirt oriented sites only sell the 3 bar version so will look at where you sourced yours.

I've made a couple decisions:

- I'm going to follow @JamesM 's idea and use the stock throttle body setup but build the harness to be able to work with ITB if I don't like the throttle response with the stock setup. Buying ITBs for this project doesn't make sense because even the cheaper ones look like will cost more than I could get for my carbs. Doesn't pencil out given my carbs would make fine throttle bodies. However, the stock setup will not only be easier, but I could then sell my entire carb setup with air cleaner to recoup a nice chunk of the EFI setup. I'm pretty sure the stock throttle body will be fine with my stock 1971cc build.

- I am going ahead with my plan to add a CAM sync and run sequential spark and injection. There are a couple reasons. One is that once this is running well, I'd like to try iridium plugs which should last longer than I'll have the car - thus eliminating another maintenance item. They are fairly spendy though and doubling their life by sparking only on compression stroke would pay for the CAM sensor. Second, reading the articles linked in Greg's blog about sequential injection convinced me it is the right way to go for my project. Remember that efficiency and emissions are AT LEAST as important to me as performance. I know that's kind of a foreign concept on this forum (IMG:style_emoticons/default/smile.gif) Getting better fuel economy and drive ability around town will be worth the expense and slightly added complexity to me. I want to bring this system into the 21st century, not just the late 20th. Looking back at the old mileage records for this car in stock (although well-worn) condition, I was getting great highway mileage but pretty poor city mileage. It will be interesting to see what I get with this upgrade. Unfortunately, it looks like that means going to Megasquirt 3 which adds another $200, although I saw there is a daughter board for Microsquirt I need to learn more about.
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GregAmy
post Sep 13 2021, 10:28 AM
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QUOTE(bbrock @ Sep 13 2021, 10:26 AM) *

Good to know about the MAP sensors. Looks like most megasquirt oriented sites only sell the 3 bar version so will look at where you sourced yours.

I bought mine from NAPA, it's a common part. ~1996 Corvette?

Note the 1-bar sensor and plug is keyed differently than the 3-bar:

https://www.ebay.com/itm/222831611980
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JamesM
post Sep 13 2021, 04:46 PM
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QUOTE(bbrock @ Sep 12 2021, 08:49 AM) *

@JamesM
Thanks again for sharing your knowledge. I do enjoy the crisp throttle response I am getting with the carbs and stock dizzy with vacuum advance. It's been too long since I've driven a 914 with D-Jet to compare though. Definitely something to consider.

I've also done more reading about MAF and unfortunately have concluded it isn't feasible for me. A big plus of heated wire MAF is that it measures air density directly so compensation for temperature and elevation changes are automatically embedded in the measurement. The problem is placement to get laminar flow of filtered air through the sensor. I found a good article that says that ideally you want a length of straight, smooth intake at least 5x the diameter of the sensor on both sides. There are screen and honeycomb diffusers to shorten those requirements but the idea of replacing the connector between the stock air cleaner and TB won't work even with diffusers due to being right next to the throttle plate. Likewise, I could mod the intake snorkel on my air cleaner to accept a MAF, but I think the sensor would get contaminated rather quickly with unfiltered air - especially considering the 3 miles of gravel road between my house and pavement.

I'm not giving up on MAF yet, but it is looking like speed density will be the preferred metering strategy which brings up manifold vacuum signal. Is there a number I should be looking for? Like I said, I get enough manifold signal from a single carb throat to pull the vacuum retard diaphragm in and have the tubes to add ports on the other side or even all 4 throats if needed. I'll measure the vacuum I'm getting now but it would be helpful to have a target.



If you are going to go with the shared plenum/single throttle body I don't think the vacuum signal for speed density will be a problem. This more becomes an issue when running ITBs. Getting a vacuum reading probably wont tell you to much as it isnt a matter of the engine producing vacuum at idle, in fact you can have poor idle vacuum and still run speed density, the issue with vacuum signals and running speed density is if the manifold vacuum being produced is reflective of the load on the engine at any given operating point. With ITBs (especially larger ITBs) your manifold pressure reaches atmospheric at very low throttle movement which limits the usability of the MAP signal for metering fuel across the entire operating range.

Single throttle body running speed density (preferably %baro) is for sure going to be the easiest place to start. I still think you are adding needless complexity (and cost) going full sequential, but very interested to see the end result.
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bbrock
post Sep 13 2021, 07:51 PM
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QUOTE(JamesM @ Sep 13 2021, 04:46 PM) *

I still think you are adding needless complexity (and cost) going full sequential, but very interested to see the end result.


Ha, ha, ha. Boy you aren't kidding about complexity! Digging deeper into what it takes just to get the ecu to support 4 injector channels. Yep - that will be a deep dive. Sadly, the more complicated it looks, the more I'm drawn to it. I'm weird that way.

One happy part is that for the most part, what it adds in cost will mostly be in time because I'll need to build the MS2 myself, then build a peak and hold injector driver board. Combined cost isn't much more than buying a pre-built Microsquirt. One cool thing is that the driver board can run the low impedance stock injectors directly without having to run them through resistors.

I need to step back and think about this part of the project a little more before fully committing, but dammit this looks like my kind of challenge.
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JamesM
post Sep 13 2021, 11:07 PM
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QUOTE(bbrock @ Sep 13 2021, 05:51 PM) *

Sadly, the more complicated it looks, the more I'm drawn to it. I'm weird that way.



Believe me, I understand the feeling...

For 15 or so years I ran various Megasquirt builds through a 100% unmolested d-jet wiring harness just to show it could be done. It was a continuous evolution that I kept hacking new features into over the years.

This was the final version I pulled out of the car last year to replace it with a Microsquirt and fully custom harness. There was more I was going to add to it but decided it was time to switch over to something a little more "sane'

You probably wont recognize the board because its not an officially licensed MS board but rather a custom board based on the early 2.2 circuit diagram.

Dont try this at home...

Seriously, after 15 years I can give you all the reasons you dont want to do something like this.

Attached Image

This was how it originally looked before the additional inline hacks to add more functionality.

Attached Image

I wont show you the earlier versions I ran using the official Megasquirt 2.2 board as they were not at all pretty. I was in my 20s, poor, and still had a lot to learn. Think my first running MS conversion cost me somewhere around 100 bucks. Things have changed a lot since then.




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falcor75
post Sep 13 2021, 11:14 PM
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I went the ITB route for my 2.3 but my car isnt built for daily driving or milage. Its more of a autocross and country road dasher. I got the camsync for mine and its installed and hooked up but we didnt end up using it. The reason is that the car drives fine without it in Alpha-N and wasted spark. My yearly milage between april and october is around 1k or less.

What I'm most happy with my set up is the noise and the crisp response and the bluetooth monitoring that allows me to display engine data in a tablet on the dash.

What I'm not happy about is the low idle at startup for the first minute untill the engine heats up a bit. With my ITB's I would need to add an idle air control valve to really sort that out.
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Superhawk996
post Sep 14 2021, 05:38 AM
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QUOTE(JamesM @ Sep 14 2021, 01:07 AM) *

QUOTE(bbrock @ Sep 13 2021, 05:51 PM) *

Sadly, the more complicated it looks, the more I'm drawn to it. I'm weird that way.



Believe me, I understand the feeling...




@bbrock (IMG:style_emoticons/default/happy11.gif) Love the craziness -- the dream of getting a 914 to be 21st century maintenance free (IMG:style_emoticons/default/lol-2.gif) but what are you doing to do about the maintenance of oil leaks. (IMG:style_emoticons/default/av-943.gif)

@JamesM Impressive - love the idea of getting the controls into the stock D-jet ECU box! Circuit minaturization of the the years is amazing.
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GregAmy
post Sep 14 2021, 06:00 AM
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QUOTE(falcor75 @ Sep 14 2021, 01:14 AM) *
What I'm not happy about is the low idle at startup for the first minute untill the engine heats up a bit. With my ITB's I would need to add an idle air control valve to really sort that out.

I spent a lot of time managing startup, controlling the AFR with WUE and idle RPM with ignition timing control (Idle RPMs Advance Timing)...and mine starts foot-off, with no aux air valve, and pretty much cores it.

It can be done w/o an idle control valve.
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ClayPerrine
post Sep 14 2021, 06:54 AM
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If you don't have manifold vacuum at idle, but it runs fine at speed, you can run microsquirt in hybrid mode. It can use alpha-n at idle to accommodate the lack of vacuum, and speed density when driving to make it more efficient.

Look at the documentation, it is covered there.

Clay
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jd74914
post Sep 14 2021, 07:10 AM
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QUOTE(GregAmy @ Sep 14 2021, 07:00 AM) *

QUOTE(falcor75 @ Sep 14 2021, 01:14 AM) *
What I'm not happy about is the low idle at startup for the first minute untill the engine heats up a bit. With my ITB's I would need to add an idle air control valve to really sort that out.

I spent a lot of time managing startup, controlling the AFR with WUE and idle RPM with ignition timing control (Idle RPMs Advance Timing)...and mine starts foot-off, with no aux air valve, and pretty much cores it.

It can be done w/o an idle control valve.

(IMG:style_emoticons/default/agree.gif)

The key is controlling idle speed with timing as Greg said. A bit of ignition trough to settle the engine in works quite well, particularly if you increase the map resolution a bit in that range. Note that while optional with a TB/plenum you really need to do this with ITBs unless you want a lot of plumbing complication.

Since you have a really nice air box, I would highly recommend using a Bosch TMAP (temperature/map sensor) installed in a boss for the barometric correction. They aren't too expensive, hide well, and are very robust. If you want to go really crazy... some motorcycle MAP sensors, 1 per cylinder, with a IC used to pull the max manifold pressures would give a really good input to speed density. From what I've seen, the failing of most ITB speed density is that a physical signal average (4 tubes from each manifold running into a plenum) is a) highly damped and b)biased downward so it's not really a true MAP representation. Someone used to make a board to do that processing, though I haven't seen one in years.



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VaccaRabite
post Sep 14 2021, 08:13 AM
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James is the man, and I'd take his thoughts as gospel.

What I would suggest though (and the way I wish I had done it) is to start with fuel and then do the spark. Don't do it all at once.

With my engine, I had the #$@ing fuel regulator plumbed backwards, which kept me from getting my first start. Since I had done fuel and spark at the same time, the troubleshooting as to WHY it would not start was extensive until I finally put a pressure gauge on the fuel rail.

Also, make sure you have a fuel pressure dial on or near your fuel rail. You are going to want this anyway when you are tuning to make sure your fuel pressure is correct.

My current MS setup is pretty different then what you are wanting (I'm using a throttle body and using MAP readings instead of a hybrid). My next one will have ITBs - but that's still to come.

Zach
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bbrock
post Sep 14 2021, 12:05 PM
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@JamesM I like it! How did mounting the boards inside the stock ecu case work? I have a couple spare D-Jet ECUs and would like to do the same.

I've had a couple crazy electronics projects. When we bought Nest thermostats for the house, I didn't like that they didn't interface with our high efficiency Mod/Con boiler with outdoor temperature reset (ODR). So I built a daughter board for a Raspberry Pi to continuously poll the Nest data and boost the boiler output temp when the system was recovering from an overnight temperature rollback. It does this by introducing resistance in stages to spoof the ODR circuit into thinking it is colder outside than it really is, and then boost output temps to catch up from the nightly rollbacks quicker.

(IMG:http://www.914world.com/bbs2/uploads_offsite/raw.githubusercontent.com-20845-1631642703.1.png)

Then I didn't like the stupid way the controller for our heat recovery ventilation system worked so I used a logic sniffer to reverse engineer the logic signals and built an arduino-based controller to automate de-humidification and ventilation using sensor feedback. The control panel is now a wall-hung (not to be confused with well-hung) tablet and custom controller app. Before starting that project, I had never heard of a logic sniffer or Arduino; and had never attempted to write an android app!

Attached Image

Attached Image

Let the craziness begin!

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JamesM
post Sep 14 2021, 01:08 PM
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QUOTE(bbrock @ Sep 14 2021, 10:05 AM) *

@JamesM I like it! How did mounting the boards inside the stock ecu case work? I have a couple spare D-Jet ECUs and would like to do the same.


A very low tech solution, I just used gel epoxy to attach some nylon studs to the d-jet case.
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Montreal914
post Sep 14 2021, 09:09 PM
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QUOTE(bbrock @ Sep 14 2021, 11:05 AM) *

@JamesM I like it! How did mounting the boards inside the stock ecu case work? I have a couple spare D-Jet ECUs and would like to do the same.

I've had a couple crazy electronics projects. When we bought Nest thermostats for the house, I didn't like that they didn't interface with our high efficiency Mod/Con boiler with outdoor temperature reset (ODR). So I built a daughter board for a Raspberry Pi to continuously poll the Nest data and boost the boiler output temp when the system was recovering from an overnight temperature rollback. It does this by introducing resistance in stages to spoof the ODR circuit into thinking it is colder outside than it really is, and then boost output temps to catch up from the nightly rollbacks quicker.

(IMG:http://www.914world.com/bbs2/uploads_offsite/raw.githubusercontent.com-20845-1631642703.1.png)

Then I didn't like the stupid way the controller for our heat recovery ventilation system worked so I used a logic sniffer to reverse engineer the logic signals and built an arduino-based controller to automate de-humidification and ventilation using sensor feedback. The control panel is now a wall-hung (not to be confused with well-hung) tablet and custom controller app. Before starting that project, I had never heard of a logic sniffer or Arduino; and had never attempted to write an android app!

Attached Image

Attached Image

Let the craziness begin!



WOW! Really impressive! (IMG:style_emoticons/default/pray.gif)

...Then again, not surprising based on the rest of your restoration work! (IMG:style_emoticons/default/smilie_pokal.gif)
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bbrock
post Sep 14 2021, 10:36 PM
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QUOTE(Montreal914 @ Sep 14 2021, 09:09 PM) *

WOW! Really impressive! (IMG:style_emoticons/default/pray.gif)

...Then again, not surprising based on the rest of your restoration work! (IMG:style_emoticons/default/smilie_pokal.gif)


Thanks. But you really shouldn't encourage this kind of (IMG:style_emoticons/default/stromberg.gif) (IMG:style_emoticons/default/biggrin.gif)

But... yeah. I think I'm going ahead with sequential injection. The problem is that as far as I can learn, no Megasquirt board supports sequential injection without modification. The easy route would be Megasquirt 3 with the M3X expansion card. It's also the most expensive option and is overkill because it provides eight additional injector channels for high impedance injectors.

The other option is to modify a Megasquirt 2 board according to the "sequential mod" instructions in the hardware manual. This removes some unused components to create two additional injector channels for a total of four. The new channels need to have a driver circuit and the solution I've decided on is this peak and hold driver board from JBPerf.com This board drives 4 low impedance injectors which will let me use my stock injectors without having to run them through a resistor pack. The board has to be assembled and will cost ~$60 for the PCB and components. To keep the total cost down, I'm going to by the MS2 board as a kit - especially given that the sequential mod would require removing components from a pre-assembled board. The overall cost, not counting my time, will be in the ball park of an assembled microsquirt board so not adding much extra expense.

I guess the first order of business is to ship my injectors off to Mr. Injector to make sure they are serviceable. If they check out, I'll probably start ordering parts in late October or early November. Hopefully Mario will have online ordering turned back on by then as everything is on hold now.
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bbrock
post Sep 15 2021, 08:08 AM
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QUOTE(Superhawk996 @ Sep 14 2021, 05:38 AM) *

@bbrock (IMG:style_emoticons/default/happy11.gif) Love the craziness -- the dream of getting a 914 to be 21st century maintenance free (IMG:style_emoticons/default/lol-2.gif) but what are you doing to do about the maintenance of oil leaks. (IMG:style_emoticons/default/av-943.gif)


@Superhawk996 I tried, but can't let this slide. Please shut your face about leaks! So far my girl doesn't seem to realize she is supposed to be dripping black pools onto the garage floor, and I'd rather not jinx it (IMG:style_emoticons/default/lol-2.gif)

Really though, back in the day, most of my low quality time with the car was spent in the engine bay either doing routine ignition maintenance which I hate, or chasing down fuel problems on a system that was well past its prime. Eliminate those and you are mostly down to oil changes and valve adjustments which I don't really mind. And of course, chasing down those rogue fluid pathways we won't mention. (IMG:style_emoticons/default/whistle[1].gif)
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Superhawk996
post Sep 15 2021, 08:41 AM
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QUOTE(bbrock @ Sep 15 2021, 10:08 AM) *

I tried, but can't let this slide. . . .


(IMG:style_emoticons/default/tooth.gif) mission accomplished
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Mike D.
post Sep 15 2021, 10:31 PM
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OK, It runs now, and pretty good too!
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Ahhh, yes! The beginning of another 7 year thread!

(IMG:style_emoticons/default/poke.gif) (IMG:style_emoticons/default/happy11.gif)

Sorry, just piling on. Good Luck! and Have Fun!
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ClayPerrine
post Sep 16 2021, 06:21 AM
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QUOTE(bbrock @ Sep 14 2021, 11:36 PM) *

But... yeah. I think I'm going ahead with sequential injection. The problem is that as far as I can learn, no Megasquirt board supports sequential injection without modification.


Check out the MS3 Pro Module. It is a board to put in your own case, and it supports full sequential injection, plus a host of other add on items like traction control.


Clay
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