Going to Megasquirt, More questions Options

[bbrock]

After about 1,700 miles of driving my freshly restored car with rebuilt engine, I’ve decided I’ve had my fun with Weber carbs and distributor-based ignition and am ready to step up to modern EFI and coil on plug ignition. Even with the jetting that came out of the box leaving the carbs running rich, the performance has been fantastic. What is not fantastic is the garage stinking of gasoline, no compensation for altitude, and being generally too fiddly to set up for my taste. My trials with the ignition are documented in another thread. Yes, I know a 1-2-3 would solve those problems but for the money, I’d rather invest in modern COP ignition as part of an EFI upgrade.

My goal is a smooth, efficient, and reliable street machine that I can drive from sea level to 11,000 ft. without starving or choking on fuel. Efficiency is at least as important as performance. As long as I can get at least the stockish 100 hp, I’ll be happy and beyond that, I’d like to wring as many mpg out as possible.

The engine is a mostly stock euro-spec 2L engine. The only mod is a fairly mild Elgin 6048 camshaft with 256 duration for the carbs. A source of pride of this build is this custom 911/914-6 inspired air cleaner I made which I think looks cool and really silences the carbs.



Now for the questions:

• Single throttle body or ITB? I think I’ve made a decision but still interested in thoughts. I was thinking about welding injector bungs onto the carb manifolds and using my carbs as throttle bodies. The main appeal is that I would keep my cool air cleaner to make the other kids jealous. However, it seems the stock throttle body would greatly simplify the conversion. Also, even though the custom intake is designed to allow access for servicing and easy air filter replacement, it does crowd an already crowded engine bay and makes working in there just that much more of a challenge. My stock TB needs some TLC and might have to be sent for professional refurbishing. I think I could sell my carb setup to cover that cost but not sure. The upshot is that I’ve all but decided to go back to the stock TB, but curious what others think.

• N Alpha, Speed Density, or MAF? I’ve been reading up on this and think I understand pros and cons, but still a little confused about sensors needed. With my efficiency goal, I think MAF is the way to go. It looks to me that cutting off the tube connecting the stock air cleaner to the TB and replacing it with a MAF could be a really slick way to add MAF in stealth fashion. Has anyone done this? If not, how does one find the right MAF to use? Other than dimensions, what else needs to be considered?

Another question is about MAP + MAF vs MAF only. I’m a little confused about advantages or when a MAP sensor is needed if you have a MAF.

• Barometric correction – this is an important feature for my location, but the hardware needed to implement it is a little confusing. It seems like if you are running a MAP, then barometric correction is obtained by adding a second pressure sensor (another MAP?) to read reference atmospheric pressure to make corrections to the fuel mixture. How does it work with MAF? Do you only need one pressure sensor to read atmosphere? Or do you still need to reference it against manifold pressure? I assume a lot of this is done in the software but I haven’t looked to far into the tuning part yet. I’m more trying to figure out a shopping list for parts at this point.

• Anyone running a CAM sync and sequential spark and injection? Again with the efficiency goal, this is appealing. Looks like Mario is working on a new version which isn’t available yet, are there alternatives available? It seems people say you still need a crank position sensor even with a cam sensor in the mix. It isn’t entirely clear why though. Lastly, and this is mostly just curiosity, but is it correct to think that the lifespan (in miles) of spark plugs are cut in half with wasted spark?

I have many more questions but this is already too long so will save them for later.
TIA

[bbrock]

@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!





Let the craziness begin!

[Montreal914]

@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!





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)

[bbrock]

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.

[ClayPerrine]

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