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

[BeatNavy]

Brent, you'll enjoy the challenge and learning associated with Microsquirt. And knowing your abilities, you'll have it running like a top quickly. I wish I could do justice to your very specific questions, but I simply don't have the breadth of experience with MS. I'm not sure how many of us here do. I think most of us using MS have it running for our specific application, but there's probably at least a few here that have knowledge that is both broad and deep enough to comment intelligently.

Random (unintelligent) thoughts WRT your questions (that you probably already know):

ITB's are going to be harder than stock TB for getting a good signal for speed density/MAP (or MAF, I would think, although I have no experience with MAF). You almost have to go Alpha N at that point. Alpha N can work from my experience. I've run both Alpha N and speed density on my stock TB setup, and they both provide slightly different experience across the driving spectrum. What's nice is it's easy to go back to one or the other. Part of the reason I swapped back and forth was trying to get my Raby 9950 cam to hold a better cold start idle, and my AFR numbers at idle were highly suspect with the exhaust I had at the time. Your ultimate setup may depend on the characteristics of your specific cam. FWIW, I'm running pure speed density for the time being.

I would think you could meet your stock HP and efficiency goals without any problem. Having said that, it seems (to me at least) that simply putting MS on a Type 4 won't easily trump what those crafty Porsche engineers did with analog/primitive D-Jet (or L-Jet) back in the day. In other words, maximizing what you can get out of the Type 4 is a bit of an art, IMO. The strength of MS is you have the ability to perform finer adjustments, get better feedback data, and do situational tuning (e.g., the ability to have a 'max efficiency tune' or a 'max power' tune that you can swap out with a click of a button).

From my understanding wasted spark (which I run) can have an impact on plug service life, but it should be a small impact if the correct plugs are used (e.g., those with platinum).

Have you joined the MS forum yet?
Some of these questions may best be asked there:
https://www.msextra.com/forums/viewforum.ph...bf40220c725d0db

[Morph914]

Brent, I will be watching this closely as I may switch over as well. I have been taking a break through the hot humid weather as it is too hot to work in my shop. If I can’t get the d-jet dialed in properly, I’m going to switch over.
(IMG:style_emoticons/default/beerchug.gif)

Cheers,
John

[Chris914n6]

I'd run Speeduino over MS as it's a newer design with newer hardware. The software is the same, TunerStudio.
I'd pick a factory system to steal parts from, like a Miata, that is already in the software. MAF for driveability.
You can keep the carbs as itb as it connects to the same plenum for the maf. Most itbs don't run thru a plenum thus no maf.

[Superhawk996]

Just sayin' . . . .

https://thedubshop.com/dual-throttle-body-f...gnition-type-4/

Mario has great reviews and he now has a dyno!

Should work with your air cleaner with minimal mods. Don't screw with trying to make your carbs into ITB's.

(IMG:style_emoticons/default/happy11.gif)

[r_towle]

Buy ITBs that look like carbs
Buy manifolds with injector ports
Go vdub route for the rest, it’s been done a lot

Cbperformance has all the hard parts

Yah, go for a kit like what was posted above!!!

[JamesM]

Throttle Body? Given you already have the cool airbox setup and the manifolds and linkage, and not knowing how your cam will react with a shared plenum intake, I would just pick up a set of ITBs.

Fueling Algorithm? This is going to depend on if you decide to go with a single throttle body or ITBs as well as well as what sort of vacuum your cam produces. Also the MSExtra firmware (that you will want to run) has additional fueling algorithms that I would recommend over the above mentioned. Single throttle body you are most likely going to want to use "% Baro" which is basically speed density scaled to your current altitude. ITBs if your vacuum signature allows I would recommend "% baro" but with ITBs it usually wont, in which case I would run "hybrid Alpha-n" which is somewhat more difficult to initially tune but gives you the best of both worlds.

Barometric correction is always applied however i believe what you are looking for is "Real time Barometric correction" which requires a 2nd MAP sensor if you are using the 1st MAP sensor for your fueling. With a single MAP sensor the MS takes a barometric reading before you start your engine and uses that for the entire run time so if you have a drastic change in altitude over your drive your fueling will be off. Adding a 2nd sensor allows it to get a constant baro metric reading. This is a really easy thing to add when building your harness.


My thoughts on CAM sync and sequential injection are that it is really overkill for these cars. The impact of it is extremally minimal and only makes a slight difference to emissions at lower RPMs as at higher RPMs the injection time required means you will always be squirting on to a closed valve anyways. It does add a lot more complexity to the build and tune though, which is already going to be a steep learning curve if you have never done this before.


Plug life with wasted spark? That all depends on what you are referring to as wasted spark. An actual wasted spark coil pack where 1/2 of your cylinders get fired with reversed polarity has the potential to more than double the wear on the 2 plugs that get fired in reverse, especially if you run stock plugs. This was one of the reasons for some of the exotic metal plantings they stared putting on the electrodes. You can run coil per plug or a 4 coil pack in 2 channel batch fire which is the same as wasted spark in that you have a wasted spark, however all 4 coils still fire with standard polarity so you dont get that extra plug erosion.

[930cabman]

Throttle Body? Given you already have the cool airbox setup and the manifolds and linkage, and not knowing how your cam will react with a shared plenum intake, I would just pick up a set of ITBs.

Fueling Algorithm? This is going to depend on if you decide to go with a single throttle body or ITBs as well as well as what sort of vacuum your cam produces. Also the MSExtra firmware (that you will want to run) has additional fueling algorithms that I would recommend over the above mentioned. Single throttle body you are most likely going to want to use "% Baro" which is basically speed density scaled to your current altitude. ITBs if your vacuum signature allows I would recommend "% baro" but with ITBs it usually wont, in which case I would run "hybrid Alpha-n" which is somewhat more difficult to initially tune but gives you the best of both worlds.

Barometric correction is always applied however i believe what you are looking for is "Real time Barometric correction" which requires a 2nd MAP sensor if you are using the 1st MAP sensor for your fueling. With a single MAP sensor the MS takes a barometric reading before you start your engine and uses that for the entire run time so if you have a drastic change in altitude over your drive your fueling will be off. Adding a 2nd sensor allows it to get a constant baro metric reading. This is a really easy thing to add when building your harness.


My thoughts on CAM sync and sequential injection are that it is really overkill for these cars. The impact of it is extremally minimal and only makes a slight difference to emissions at lower RPMs as at higher RPMs the injection time required means you will always be squirting on to a closed valve anyways. It does add a lot more complexity to the build and tune though, which is already going to be a steep learning curve if you have never done this before.


Plug life with wasted spark? That all depends on what you are referring to as wasted spark. An actual wasted spark coil pack where 1/2 of your cylinders get fired with reversed polarity has the potential to more than double the wear on the 2 plugs that get fired in reverse, especially if you run stock plugs. This was one of the reasons for some of the exotic metal plantings they stared putting on the electrodes. You can run coil per plug or a 4 coil pack in 2 channel batch fire which is the same as wasted spark in that you have a wasted spark, however all 4 coils still fire with standard polarity so you dont get that extra plug erosion.

Looks awfully confusing. Is the Weber setup that bad?

[JamesM]

I'd run Speeduino over MS as it's a newer design with newer hardware. The software is the same, TunerStudio.
I'd pick a factory system to steal parts from, like a Miata, that is already in the software. MAF for driveability.
You can keep the carbs as itb as it connects to the same plenum for the maf. Most itbs don't run thru a plenum thus no maf.

I probably wouldn't

Zero advantages but plenty of reasons not to

Megasquirt has a lot more development and people running it.

The Speeduino hardware isnt really any newer, sure the original megasquirt has been around MUCH longer (which is a good thing) but the hardware and software are both constantly being updated. The MS system I run today is 100% different than the MS system I was running in 2005.

Speeduino was/is just a project to do basically the same thing as MS but using an Arduino as its core. While MS systems were designed specifically to be fuel injection systems the Arduino was not, its just a generic tinkering/project platform that someone decided to build an injection system with, probably to avoid the Megasquirt licensing. Not sure if any of the components on the Arduino itself are even automotive grade, let alone able to survive an 914 engine bay.

There are ecu options other than megasquirt/microsquirt you could go with, not sure i would do Speeduino though.

[JamesM]

Looks awfully confusing. Is the Weber setup that bad?

The difference between a d-jet setup and a GOOD megasquirt(or any programable EFI) install is night and day.

The difference between webers and a GOOD megasquirt install will absolutely blow your mind.


Notice i emphasized GOOD. Its a steep learning curve and there are a lot of ways to screw it up.

[Montreal914]

Will follow this thread with great interest. (IMG:style_emoticons/default/popcorn[1].gif)

I had to pause my MS conversion because I decided to pretty much redo the whole car... (IMG:style_emoticons/default/rolleyes.gif) Things are moving along but it is quite an undertake as you obviously know. (IMG:style_emoticons/default/smile.gif)

Very nice intake setup BTW. My understanding is that ITBs are more of a challenge, but it would be sad not to use your nice design!

Good luck! (IMG:style_emoticons/default/beerchug.gif)

[GregAmy]

I go to all the trouble to write this stuff up...

https://tgadrivel.blogspot.com/2020/03/on-m...914-part-1.html

[bbrock]

I go to all the trouble to write this stuff up...

https://tgadrivel.blogspot.com/2020/03/on-m...914-part-1.html

And I have read ALL of it! In fact, I blame you and your blog for getting me into this trouble (IMG:style_emoticons/default/happy11.gif)

Thanks everyone for all the feedback so far. A lot of great stuff to ponder.

I'm surprised by the discussion on ITBs. I really though the overwhelming advice would be to ditch the fancy air cleaner and use the stock TB. So let's talk about this a little more. My second stop on this journey (after Greg's blog) was looking at the Dub Shop kits. It didn't take long to rule those out. Yes, the ITBs are sweet but are as expensive as a set of carbs and more than I think I could sell my carbs for. Also, I cannot assume they would be compatible with my air cleaner. Yes, the ITBs are the same dimensions as 40IDFs so no issue there, but what about the manifolds? If they are as much as a half inch different and total height than mine, then the geometry of the cleaner intakes will be off and they won't fit correctly. To me, if I went the ITB route, it makes more sense to just use the carbs as throttle bodies. Others have done it. Why would that be a problem. It would eliminate a major expense.

As for the cleaner. To be honest, that was a personal challenge. I'm very proud of that cleaner, but now I've done it and won't cry if I pass it on to someone else to enjoy. Working in the engine bay will be a little easier with the stock TB and cleaner setup. Then again, the point of doing this is to greatly reduce the need to work in the engine bay.

WRT vacuum signal. I guess I should measure what I have. All I can say now is that I'm getting good enough signal from a single barrel to actuate my vacuum advance (port vacuum) and retard (manifold vacuum). My cam is pretty mild. Basically stock lift with a bit longer duration. Enough that it would run rough with D-Jet which is why I'm not just refurbing the D-Jet system. I don't have an appetite to split the case on a freshly rebuilt and running well engine to swap cams.

So the real question WRT ITBs is, what advantage do they bring other than looking cool and letting me keep the cool air cleaner? Honestly, I need more than that. I imagine they provide significant advantages in big displacement engines, but would they do anything meaningful for my little hundred pony power plant?

Re: barometric correction - Yes, I'm talking about real time correction. Where I live, I can easily drive through 8000 ft. of elevation change on a single tank of gas. I'd like to be able to cruise over high mountain passes without missing a beat.

WRT if the Weber setup is that bad. In a word - yes. I would say I hate them. Just the stench of gasoline in the garage they cause is enough to get rid of them. I have 3 fuel injected cars dating back to MY 1991 with a combined total of nearly a million miles on them. All of them have performed flawlessly through those miles. Starting in all conditions, running well at all elevations and temperatures, and all that with zero tune-ups among the 3 of them. I want that for the 914.

[bkrantz]

Brent, welcome to the club. You may make progress faster than me, since my Dubshop kit is still in boxes.

[bbrock]

Brent, welcome to the club. You may make progress faster than me, since my Dubshop kit is still in boxes.

Ha ha. You have no idea how jealous I was when I saw that kit on your thread!

A couple more questions:

I know a lot of people set up Microsquirt only without adding ignition control. I assume, but am not sure, that it could be done in reverse. I'd like to convert my my ignition to MS controlled COP first, and once that is running, turn to fuel management. Any problem doing it that way?

Also, I've seen some cool installs that hide the MS ECU and Lambda controller inside a stock D-Jet ECU box. Anyone who has done that care to share how it has worked? It doesn't exactly comply with recommendations for mounting either unit but has a lot of appeal to me and I don't see why it wouldn't work.

Oh, and Rob asked if I've joined the MS forum yet. The answer is no, but I've stalked it quite a bit. I'll join as I get closer but thought I'd start here with the fine folks with 914 specific experience first. And thanks for your vote of confidence. Someday we may meet in person and you will realize how misguided it is (IMG:style_emoticons/default/lol-2.gif)

[Montreal914]

In case you haven't seen/read my partial adventure, enjoy! (IMG:style_emoticons/default/smile.gif)

http://www.914world.com/bbs2/index.php?sho...42361&st=60

That being said, it stands today exactly where I stopped on the last post because I started to rebuild the whole car. I am looking forward getting back to this as rust repair isn't really appealing to me...

So, although there might be a good portion of the setup in place, nothings has really been tried. (IMG:style_emoticons/default/dry.gif)

[JamesM]

Mario at the dubshop makes some awesome parts and kits, but some of the parts he supplies (specifically ITBs) are sourced from other vendors and available cheaper, at least they were last time I looked. Using your carbs as throttle bodies is totally acceptable, it just requires some custom fabrication as no one makes manifolds with injector ports. Reasons I suggested ITBs over the stock d-jet intake is that your cam is a bit of an unknown, you already have most of the parts to do it along with that cool airbox, and its likely that going from 4 throttle plates down to 1 you are going to loose some throttle response which some people may not like and may interpret as a loss of power (though you may wind up gaining some midrange torque). Great thing about aftermarket injection though is that if you build your wiring harness with enough slack to accommodate either configuration you could easily swap between either intake setup down the line. If you already have the 2.0 intake bits by all means go for it, it will be less work and less complicated to tune. No harm and easy enough to swap later if you like.

Advantages of ITBs? Better throttle response. They can be a work around if your single plenum design isnt compatible/ideal for your engine config. This is a pretty in depth subject so ill let you google it rather than get into it here. Also they definitely can allow for more flow than the stock intake IF your motor needs it, but it sounds like yours may not. They have some potential disadvantages as well, may loose some drivability, especially if they are not sized correctly, may loose the ability to run speed density, possible loss of some low/mid range torque, more difficult to tune, more complicated linkage, having to get them synced.

Thanks everyone for all the feedback so far. A lot of great stuff to ponder.

I'm surprised by the discussion on ITBs. I really though the overwhelming advice would be to ditch the fancy air cleaner and use the stock TB. So let's talk about this a little more. My second stop on this journey (after Greg's blog) was looking at the Dub Shop kits. It didn't take long to rule those out. Yes, the ITBs are sweet but are as expensive as a set of carbs and more than I think I could sell my carbs for. Also, I cannot assume they would be compatible with my air cleaner. Yes, the ITBs are the same dimensions as 40IDFs so no issue there, but what about the manifolds? If they are as much as a half inch different and total height than mine, then the geometry of the cleaner intakes will be off and they won't fit correctly. To me, if I went the ITB route, it makes more sense to just use the carbs as throttle bodies. Others have done it. Why would that be a problem. It would eliminate a major expense.

As for the cleaner. To be honest, that was a personal challenge. I'm very proud of that cleaner, but now I've done it and won't cry if I pass it on to someone else to enjoy. Working in the engine bay will be a little easier with the stock TB and cleaner setup. Then again, the point of doing this is to greatly reduce the need to work in the engine bay.

WRT vacuum signal. I guess I should measure what I have. All I can say now is that I'm getting good enough signal from a single barrel to actuate my vacuum advance (port vacuum) and retard (manifold vacuum). My cam is pretty mild. Basically stock lift with a bit longer duration. Enough that it would run rough with D-Jet which is why I'm not just refurbing the D-Jet system. I don't have an appetite to split the case on a freshly rebuilt and running well engine to swap cams.

So the real question WRT ITBs is, what advantage do they bring other than looking cool and letting me keep the cool air cleaner? Honestly, I need more than that. I imagine they provide significant advantages in big displacement engines, but would they do anything meaningful for my little hundred pony power plant?

Re: barometric correction - Yes, I'm talking about real time correction. Where I live, I can easily drive through 8000 ft. of elevation change on a single tank of gas. I'd like to be able to cruise over high mountain passes without missing a beat.

WRT if the Weber setup is that bad. In a word - yes. I would say I hate them. Just the stench of gasoline in the garage they cause is enough to get rid of them. I have 3 fuel injected cars dating back to MY 1991 with a combined total of nearly a million miles on them. All of them have performed flawlessly through those miles. Starting in all conditions, running well at all elevations and temperatures, and all that with zero tune-ups among the 3 of them. I want that for the 914.

[moto914]

Hi. Running Microsquirt with ITBs here.
The knowledge that gets shared on this site is fantastic. Thanks ! Personally embarked on the MS path for the learning process and a mindset that it wouldn't necessarily add power. The experience has been fine
Your airbox looks great. Was really thirsty for that kind of setup before running ITBs.
You could offsett expenses If you made one that can be fit the standard dual carb manifolds.
There may be buyers.
My setup started with monitoring only.

[GregAmy]

And I have read ALL of it! In fact, I blame you and your blog for getting me into this trouble (IMG:style_emoticons/default/happy11.gif)

(IMG:style_emoticons/default/drunk.gif)

ITBs are airflow. You'll flow more air with four 40mm(?) bores than with a single 55mm(?), though one can legit argue only one hole is pulling through the stock TB at a time...and as noted above the shorter run gives you throttle response.

I will also note that I'm not seeing a significant drop in manifold pressure as the car revs to redline, so I'm pretty sure the stock setup is not a big restriction. FAT 2056cc with a FAT fuel injection cam.

I've been mulling the idea of replacing my 40DRLAs on the historics race car with Mario's setup, but $$$ and time have allowed me to procrastinate. Plus I'd have to re-do my fuel system (it's single feed line, not recirc) and I'd have to install a voltage manager (I don't run an alternator). But I think it would make for a better race car.

I would not be surprised if you can use your air cleaner with Mario's system; he's using CB Performance throttle bodies which I'm pretty sure are based on Weber IDF carb bodies. Uses the same manifolds, IIRC.

GA

[bbrock]

@Montreal914 Thanks for that link! I remember reading it before and thinking it was interesting, but didn't understand most of it. Now I can see the wealth of info there and will be referencing it often!

@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.

@moto914
Thanks for the compliment. IFAIK there is no standard for carb manifolds for the 914 but could be wrong. I've seen tall and short manifolds and it looks to me like total height dimensions could vary by manufacturer. Mine are what was sold in the old Weltmeister kits way back in the 20th century. The issue is that the center air box mounting height needs to be matched so the intakes mate squarely with the carb housings. Changing the airbox or carb heights relative to each other but much more than a quarter inch changes the angle and creates gaps. Now it could be that my manifolds are the same height as many that are commonly sold now - I just don't know.

Here's a video I posted some time ago with more detail on the air cleaner. The comment I make in the vid about fitting under the rain tray was foreshadowing. It did NOT fit and required going back in and chopping down the bracket holding the air box about an inch and reworking the intakes to restore the proper fit.


https://www.youtube.com/watch?v=Xm-LOk_IBpg