Going to Megasquirt, More questions Options

[Superhawk996]

Check out the MS3 Pro Module.
Clay

(IMG:style_emoticons/default/yikes.gif) Spendy. Card alone is almost 25% of the complete DubShop Kit!

Pretty cool though. I really don't like the form factor of MS boards other than the MicroSquirt. I also see they have a newer MicroSquirt with higher current driver circuits.

The DIY FI space is getting pretty interresting. (IMG:style_emoticons/default/idea.gif)

[bbrock]

Check out the MS3 Pro Module.
Clay

(IMG:style_emoticons/default/yikes.gif) Spendy. Card alone is almost 25% of the complete DubShop Kit!

Pretty cool though. I really don't like the form factor of MS boards other than the MicroSquirt. I also see they have a newer MicroSquirt with higher current driver circuits.

The DIY FI space is getting pretty interresting. (IMG:style_emoticons/default/idea.gif)

Yeah, it's a chunk of coin but competitive with a an assembled M3 with M3X and in a more compact form factor. It would still require a resistor pack or P&H driver card to run stock low impedance injectors. I'm still thinking the MS2 route seems most practical for me.

Speaking of injectors, I came across this post kind of lobbying against using old D-Jet Benz injectors. Wonder about people's thoughts relative to a 914.
https://www.benzworld.org/threads/megasquir.../#post-18055685

[jd74914]

They're certainly right in terms of the poor spray pattern/atomization. That said, the importance of all of that really is somewhat dependent on your intake design, mixing distance from valve, etc. Modern injectors are objectively better. The temperature thing is true too, high-impedance do run cooler generally, though I'm not sure that's why they are oversized. Personally, if you're comfortable adding a real fuel rail with anchors and not the hose-end style of OEM, I think new injectors are a worthy upgrade.

[jd74914]

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.

The JBPerf stuff works well (everything he makes that I've seen anyways). I don't think you can go wrong there.

If you go MS3 you get a n [unloaded] loop execution time of ~0.20 ms vs. ~0.33ms of a MS2. Think about that potential extra 0.13 ms of engine crispness. (IMG:style_emoticons/default/shades.gif)

I have an MS3X waiting to go in, but that's mostly because I got a really good deal on it [used] and am spoiled by having worked with a lot of higher end stuff (LR F88, etc.).

[Superhawk996]

Modern injectors are objectively better. . . . I think new injectors are a worthy upgrade.

(IMG:style_emoticons/default/agree.gif) Yeah - what he said. (IMG:style_emoticons/default/biggrin.gif) 50 years of learning and improvments in injectors since 1970. Why leave that on the table? Especially if you're going sequential.

If just dumping fuel on the back of a closed intake valve with batch injection it doesn't matter as much. Sequential is a whole different ball game if pushing for the last bits in performance and emissions.

[bbrock]

Modern injectors are objectively better. . . . I think new injectors are a worthy upgrade.

(IMG:style_emoticons/default/agree.gif) Yeah - what he said. (IMG:style_emoticons/default/biggrin.gif) 50 years of learning and improvments in injectors since 1970. Why leave that on the table? Especially if you're going sequential.

If just dumping fuel on the back of a closed intake valve with batch injection it doesn't matter as much. Sequential is a whole different ball game if pushing for the last bits in performance and emissions.

You guys sure are good at spending my money (IMG:style_emoticons/default/lol-2.gif) It makes sense though. Kind of a side point out of curiosity, Maybe I'm way off, but it seems like the injector location on the stock runners would be better for taking advantage of the better spray pattern of modern injectors than mounted higher in ITBs. It just seems like the ITBs would have more time for the fuel vapor to fall out of suspension or wind up stuck to the manifold walls. Maybe the velocity is enough that it is insignificant. I know nothing.

Also, I'd like to hear more about the influence of fuel rails for realizing benefits from modern injectors. A plus to ease the sting of losing my cool custom air cleaner is reverting to a mostly stock (although less cluttered with vacuum lines) look in the engine bay. I'm wondering what I sacrifice by sticking with the hose-mounted rails.

Other than a further drain on the wallet, it looks like upgrading injectors would just require swapping the P&H driver board for this one. Then there is the matter of selecting the right injectors which I know nothing about (IMG:style_emoticons/default/blink.gif)

[bbrock]

An additional 800 miles of seat time in my car hasn't lessened my desire to ditch the carbs and dizzy. I continue researching how I want to approach this and have more questions.

- Do I need a crank sensor? To go full sequential I need a cam position sensor for sure. I've read that cam sensors are not as accurate as crank sensors but that is because of chain or timing belt slack. Type 4 cams are gear driven. Is there enough gear lash in distributor drive mechanism to affect position accuracy? I have no issue with adding a crank sensor, but it is the only part that will require dropping the engine so the question of whether it is necessary if I have a cam sensor has to be asked.

- I'd love to hear thoughts on whether modern injectors would be worth the cost if I don't upgrade the fuel rails. Still not sure what I want to do, but curious why modern fuel rails would make a difference.

- Anyone know when Mario plans to open online ordering on The Dub Shop site? It's been closed since June so he can catch up on orders and restock parts. Sure, I could reach out directly but seems counterproductive to pester a guy who is already swamped. I know some of you are in touch with him so wondered if you've heard anything.

That's it for now. There will be more.

[Superhawk996]

- Do I need a crank sensor? To go full sequential I need a cam position sensor for sure.

I’m gonna get flak but who cares.

No -- you don’t need a crank sensor in the technical sense.

Yes - agree you need a cam sensor for full sequential. If you know where the cam is, then you know when to fire the spark. You can infer where the crank is if you know where the cam is, but, the opposite is not true.

Case example. Early 90’s Miata NA 1.6L engines (timing belt driven cams) have a cam angle sensor only and they run great! Full sequential. However that crank angle sensor on a miata is actually sort of absolute position encoder. It is a $200+ sensor. That car uses to fire up literally in 1 crank shaft revolution or less because of that sensor. Most FI systems need a couple crank revolutions to work out the signal timing between the seperate crank and cam sensors to figure out where to put the spark.

Found a decent link on the Miata crank angle sensor signal if you care:
http://www.rivercityroad.com/garage/cas.htm

Eventually Mazda went to a more conventional Hall Effect crank sensor + Hall Effect cam sensor, probably due to cost and to become more consistent with OBD2 regulations.

The problem with cam only is if someone sells a sophisticated enough cam sensor off-the-shelf and who has the software to run cam only for a T4.

I’d talk with Mario if you get serious about it to understand what his cam sensor was, what he's doing with the signal, and what software he's running with it.

In the limited digging I've done, he seems to have what I'd consider the minimum for easy DIY success:

1) He's done it before with T4
2) He has a dyno
3) He offers a complete kit.

Not negating the great work done by the guys on this site either. Lots of good information here too but the further off the rails you get trying to do non-standard MegaSquirt, the more you're on your own


On your other question

- I'd love to hear thoughts on whether modern injectors would be worth the cost if I don't upgrade the fuel rails. Still not sure what I want to do, but curious why modern fuel rails would make a difference.

I don't think it will net you any performance. I haven't seen anyone saying the OEM fuel rails are a flow bottleneck. Personally, I'm just not a fan of how the weight of the fuel rails, and associated fuel hose are not well supported. Basically just cantilevered off the injectors. It works, but, it wouldn't fly by modern engineering standards and road load testing. That's my opinion.

@bbrock

[nditiz1]

I have only seen the crankfire setup that McMark was selling from Original Customs. With that said what is the adv to running the cam sensor?

If it was easier to install/cheaper big a significant amount/better signal/easier to setup I might entertain the idea. Are any of those advantages present? Also, I know Al Kosmal is currently working on a T4 - EFI setup.

[bbrock]

I have only seen the crankfire setup that McMark was selling from Original Customs. With that said what is the adv to running the cam sensor?

If it was easier to install/cheaper big a significant amount/better signal/easier to setup I might entertain the idea. Are any of those advantages present? Also, I know Al Kosmal is currently working on a T4 - EFI setup.

The advantage is that I like to over complicate things (IMG:style_emoticons/default/biggrin.gif) An objective is to get the best economy (especially in town) and lowest emissions I can. A cam sensor let's you go full sequential for spark and injection which in theory can give a little better driveability and economy at lower speeds, reduced emissions, and smoother idle. I know going sequential isn't going to gain me that much, but I like this kind of challenge.

The descriptions for Marios' old NLA cam sync sensor says it must be used with a crank sensor. I'm not sure if the same will be true for the new one which will have a trigger wheel instead of flying magnet. If it were possible to get by with just a cam sensor and no crank sensor, you wouldn't have to drop the engine to do the conversion. I guess that might simplify the install regardless of spark and injection mode.

[Frank S]

I have only seen the crankfire setup that McMark was selling from Original Customs. With that said what is the adv to running the cam sensor?

If it was easier to install/cheaper big a significant amount/better signal/easier to setup I might entertain the idea. Are any of those advantages present? Also, I know Al Kosmal is currently working on a T4 - EFI setup.

The advantage is that I like to over complicate things (IMG:style_emoticons/default/biggrin.gif) An objective is to get the best economy (especially in town) and lowest emissions I can. A cam sensor let's you go full sequential for spark and injection which in theory can give a little better driveability and economy at lower speeds, reduced emissions, and smoother idle. I know going sequential isn't going to gain me that much, but I like this kind of challenge.

The descriptions for Marios' old NLA cam sync sensor says it must be used with a crank sensor. I'm not sure if the same will be true for the new one which will have a trigger wheel instead of flying magnet. If it were possible to get by with just a cam sensor and no crank sensor, you wouldn't have to drop the engine to do the conversion. I guess that might simplify the install regardless of spark and injection mode.

Mario's cam sync is working togeher with the crank sync only. But you can run a missing tooth sensor in the dizzy for sequential ignition and fuel, so no need for the crank sensor. The dizzy sensors are also much easier to service if the sensor is failing...

[JamesM]

- Do I need a crank sensor?

If you want to run any ignition control it is highly recommended. If you want to run full sequential i believe it is mandatory.

I highly recommend Mario's crank trigger setup for multiple reasons, however as you mentioned it does pretty much require you drop the engine in a 914 to install and/or service it. Well, maybe not required but you are going to want to.

More recently I have came across this crank sensor setup that looks like it would be easily serviceable with the motor in the car, but i havent personally run it so i cant speak at all to how well it works. Also its expensive and looks like it probably uses a VR sensor (one of the reasons i prefer Mario's setup is it uses a Hall sensor that gives a nice clear square wave output)

https://www.clewett.com/index.php?main_page...;products_id=31

- I'd love to hear thoughts on whether modern injectors would be worth the cost if I don't upgrade the fuel rails. Still not sure what I want to do, but curious why modern fuel rails would make a difference.

I see no need to swap out the fuel rails.

These are my preferred injectors when running stock intake runners

https://www.fiveomotorsport.com/a280-a380-h...-fuel-injector/

Lots of advantages in my mind:
They are pretty much plug and play to the stock intake runners and fuel rails.
They have locking EV1 connectors
They are high impedance so no need to use inline resistors or run PWM control
They run at higher pressures for better atomization
They come documented with flow specs and voltage correction datasheet
They are brand NEW

Only potential downside is that you will most likely want to run them with a newer style fuel pressure regulator to run at higher pressures, but there are a few options there that easily install in place of the stock regulator.

I think the deciding factor though should really involve asking yourself the question, do i trust 50 year old injectors and if so, for how long?

A few years ago I was driving behind @StratPlayer out of Salt Lake on the way to RRC and wound up getting my car covered in oil when a sticky stock injector holed a piston in his brand new 2056. Given all the other modernizations you are putting in, i see no reason to stick with old injectors. Not to mention, the stock 2.0 injectors are absolutely HUGE for a 2.0L motor resulting in very small injector pulse widths at idle which produces less accurate fueling. In fact, back in the VERY early days (pre MS2) I had to run a special "hi-res" code variant to gain the resolution needed for proper idle control with the stock injectors. If you do want to run d-jet injectors the ones off a 1.7 are much more appropriately sized for the application.

[ClayPerrine]

Add a 36-1 wheel behind the fan replacing the spacer, and use a Vanagon hall effect distributor for the cam sensor.

The vanagon distributor is a drop in for a Type-IV.

Clay

[bbrock]

This is all great info everyone! Looks like I'll be adding a crank sensor which was the original plan anyway, but seeing that his new cam sensor will have a trigger wheel (I assume missing tooth) got me thinking.

Thanks @JamesM for pointing me toward those injectors. I wasn't very clear before but I had already decided to go with new injectors. The question was whether to upgrade the fuel rails which I'd rather not do to keep the stockish appearance. I agree that going to all this trouble and running old injectors doesn't make much sense. I figured I'd need to replace the stock pressure regulator too.

You raise an interesting question about injector size though. I read somewhere that for running full sequential injection, it is better to err on the larger size for injectors. The rationale was that larger injectors allow for a shorter pulse width that allows for more of the squirt to go into an open intake valve and therefore could spread the benefit of sequential a little higher up the rpm range. Made sense to me but wonder what others think.

The vanagon distributor is an interesting idea. Didn't know that was an option.

[JamesM]

You raise an interesting question about injector size though. I read somewhere that for running full sequential injection, it is better to err on the larger size for injectors. The rationale was that larger injectors allow for a shorter pulse width that allows for more of the squirt to go into an open intake valve and therefore could spread the benefit of sequential a little higher up the rpm range. Made sense to me but wonder what others think.

I think the theory is sound, shorter pulse width will buy you more time firing on an open valve. You could probably run some math to figure out what the exact rpm difference would be between a larger and smaller injector. Looking at the math before though was what made me loose interest in sequential in the first place, at least for my autox car. Only gains are in emissions/economy at idle/lower RPM and once past a certain injector duty cycle and depending on your cam duration you are firing on a closed valve either way. Given how my autox car is normally driven, wouldnt have had any advantages for me.
Also with these motors usually having to be tuned on the rich side everywhere, including idle anyways i don't know if it would wind up making any measurable difference at all.

[bbrock]

Okay, here's some fun with math. I calculated the theoretic time injectors on my engine need to be open to spray a dose as a percentage of the time the intake valve would be open. Not 100% sure my math is right but I got help on calculations here:

https://www.team-integra.net/threads/calcul...se-width.46738/

and here:

https://www.physicsforums.com/threads/findi...ns-open.584241/

The target AFR numbers are very tentative based on some earlier threads on the subject. I'm assuming I'll want the leanest mix at idle and cruising around 3000 rpm. Between idle and 3000 rpm would mostly be mild to moderate acceleration under load, and above 3K will mostly be WOT. I've barely dipped my toe into learning about managing mixtures, so those numbers might change as I learn more about AFR and how megasquirt can adjust timing and fuel dose in response to CHT. I think they are reasonable for this thought exercise though.

[Data Corrected]

Anyway, here are the results:

[Superhawk996]

I didn't check your math. I'm impressed though. No one bothers to do the math. Engineer at heart I guess! (IMG:style_emoticons/default/happy11.gif)

I sure hope it's snowing out there . . . otherwise you're wasting valuable driving time doing injector math. (IMG:style_emoticons/default/biggrin.gif) Just sayin'.

(IMG:style_emoticons/default/popcorn[1].gif) Great discussion.

[bbrock]

I didn't check your math. I'm impressed though. No one bothers to do the math. Engineer at heart.

I sure hope it's snowing out there . . . otherwise you're wasting valuable driving time doing injector math. (IMG:style_emoticons/default/biggrin.gif)

(IMG:style_emoticons/default/popcorn[1].gif)

Predicting a foot of it tonight. Trying to get a project done before it gets cold enough to freeze in our greenhouse so no driving this weekend.

[bbrock]

Found a major error in my calculations. I accidentally included a wrong column in the pulse width calculation. The corrected results are more interesting. It looks like with 26 lb injectors, it would start spraying part of the charge onto the backs of closed valves starting at about 1,500 rpm but with 36 lb injectors, that wouldn't begin until about 2,200 rpm. At 5k rpm about 29% of the charge from a 26 lb injector would spray into an open valve and that increases to about 40% with a 36 lb. injector.

Based on that, it seems like maybe larger injectors would be the way to go, but there must be a down side. Thoughts?

[JamesM]

Found a major error in my calculations. I accidentally included a wrong column in the pulse width calculation. The corrected results are more interesting. It looks like with 26 lb injectors, it would start spraying part of the charge onto the backs of closed valves starting at about 1,500 rpm but with 36 lb injectors, that wouldn't begin until about 2,200 rpm. At 5k rpm about 29% of the charge from a 26 lb injector would spray into an open valve and that increases to about 40% with a 36 lb. injector.

Based on that, it seems like maybe larger injectors would be the way to go, but there must be a down side. Thoughts?

With larger injectors you lose some level of precision in fuel metering. I experienced this first hand when a early version of the MS1 code was unable to control the larger injector well enough for a decent idle.

At higher duty cycles both batch and sequential are putting the same amount of fuel though the open valve just as a result of how long the injector is firing for, so the only real difference is going to be seen below the point where the sequential starts firing on the closed valve.

So when comparing 26lb to 36lb injectors with sequential injection we are basically looking at a trade off between fueling precision across the entire operating range vs possible improvement in the 1500-2200 RPM range due to firing 100% on an open valve, and honestly how much time do you spend driving in that range? I think I would go with the smaller injector either way.

You really took me seriously on the math there! I cheated when i looked into it and just used recorded duty cycles across the RPM range for my setup from my datalogs, wound up with a similar result though, if I recall in my case the the cutoff was going to be somewhere around 1800rpm which for my purposes wasn't worth the effort/cost.

You give up the potential for some features going with Microsquirt but i think that platform has some advantages as well and in my mind it is the better compromise.