StealthNB

OP

If you want to keep things simple, consider upgrading the crank pulley to like ATI and or the Supermiata but with the OEM crank pulley on your pre-95 miata you are not 100% safe.

deezums

iTrader: (3)

If you want to keep things simple, do nothing at all. It's worked for thousands of turbo 1.6 miata and countless other early 1.8 miata.

The only time it don't work is with this pro level tuner. Then you are 100% unsafe.

bmxfuel007

iTrader: (21)

You don't absolutely need the 99 cam wheel and cam sensor, and use the CAS for the cam sensor signal.

Can get the 99 crank pulley with timing wheel and crank sensor and wire that into the respective wire for the crank signal to the megasquirt. the stock 4 tooth wheel is pretty accurate and a 36-2 or -1 isn't quite necessary unless you want to brag about it.

The CAS o-ring does leak a lot, so deleting it by going with a cam sensor would solve that headache. Would keep the back of the engine a lot cleaner

deezums

iTrader: (3)

Yes, now lets loose the cam trigger, or buy another extra valve cover, or weld a cam trigger in.

All because this tuner is a moron, and the cas might leak.

Great!

bmxfuel007

iTrader: (21)

why would you loose the cam trigger? it'd eventually fall out....

Deezums, why do you have so much animosity towards this his tuner? Were you a previous customer that got burned or something? He sounds like someone who runs a business and isn't willing to do a job where he considers it a compromise, whether you consider it one or not

aceswerling

Oh, I didn't realize that a cam trigger is different than a CAS.

FWIW, I already had a SuperMiata crank pulley installed as part of this build. So I'm all set there. I refrained from getting a crank wheel and sensor based on Dimitris's suggestion I didn't need it.

deezums

iTrader: (3)

Because it's part of the CAS you stupid freaking ****.

I have animosity towards this tuner because from what I've seen and read from him thus far, He's a ******* idiot.

You've clearly no idea what's going on, either. It'd be super easy to mislead you to believing anything, as I believe this shitty tuner is to cover his own incompetence.

Instead of just admitting that a CAS trigger for crank and cam is fine, yet not the pinnacle of automotive triggering, this tuner has chosen to either lie or make **** up about the consequences of not wasting more money for performance that may not be required.

That's why I don't like him.

Savington

iTrader: (31)

Holy ****, this thread is bad.

Your tuner is incorrect. The CAS outputs both cam and crank sensors. Every single 1994-1997 Miata uses the pattern from this sensor to run sequential fuel, and every 1990-1993 Miata is capable of doing the same.

In other words:
.022 plug gaps will cause shitty idle. If .022 plug gaps are required to avoid spark blowout, something in the ignition system is malfunctioning. You aren't the first person to have issues with that particular ignition system.

Yes, which is why sequential ignition is used particular in high-RPM and high-boost applications. Your car is neither, and you should be able to batch-fire your coils without issue.

Every 94-97 Miata uses the CAS to run sequential fuel. It's not "fake" sequential or "bandaid" sequential or whatever - it's true sequential fuel. You can use a Megasquirt to run full sequential spark off the 90-97 CAS as well. No qualified statements, no asterisks, no BS. It can be done safely, and people do it.


The OEM harmonic damper has absolutely nothing to do with the inaccuracy of the 90-97 CAS.


In short:


OP, I rarely run cars with sequential spark. On a race car that sees sustained high-RPM use, or on a car that's running coils that require a lot of dwell (like 6ms+), then yes, it can be beneficial, because you want to give the coil time to cool down between charging/firing cycles. For most street cars, it's just not necessary.

aceswerling

Thanks again for the help. It turns out I was incorrect about the plug gap. We're at .032, not .022. John said he knocked down the gap to .032 to help prevent the spark blowout. The idle quality got a lot better once I switched to sequential injection and I'm satisfied with how it's running now.

Regarding the Fab9 kit, perhaps in retrospect I should have gotten Savington's Toyota-based CoP system since that avoids the ignition controller. But since I've got this one I'd like to try and make it work.

I'm hearing that sequential ignition isn't really that important at the power levels I'm making. Honestly, that's not too surprising since Dimitris said from the very beginning that it's totally optional. Still, it sounds cool for the reasons I mentioned before. Maybe it helps, maybe it doesn't, but I think it's an interesting experiment. I'm glad to hear the CAS will be sufficient. Perhaps I'll add a crank sensor at some point if I want a project to play with.

Thanks also for the confirmation that the crank pulley isn't going to make a difference with timing. I got that since I was led to understand it'll help dampen crankshaft vibrations. I figured that was also optional based on my relatively low power levels, but I thought it would be a good move for safety.

Eipgam

http://members.rennlist.org/951_race...atchFiring.pdf

FUEL-DELIVERY AT HIGH-RPM
Under high-RPM operation, the fuel-injectors have longer duty-cycle periods. At redline, they are close to their maximum capacity and the differences in fuel-delivery is only 20% for a complete 720-degree 4-stroke engine cycle .

Another interesting tidbit is that the sequentially-fired injectors spend just as much time firing fuel at the back of a closed intake-valve as the batch-fired arrangement.

CONCLUSION AND DISCUSSION
Upon viewing a graphical display of the fuel-injector duty-cycles, one can see that the two methods of fuel delivery are not all that different. At low-RPM operation, the volume of fuel metered is minimal given the time available that these two systems have identical performance. At high-RPM operation near redline (where maximum-power is generated), the two systems are even more similar in fuel-delivery characteristics.

The only difference is really at which time during the closed-intake period to squirt fuel at the back of the intake-valve. Therefore, we can conclude that the differences in maximum power output is similar as well. This is supported in real-world cases of minimal differences.

The last scenario is not often used due inefficiencies in controlling the injectors at idle and low-RPM operations (because of minimum injector duty-cycle). High-RPM operation is also compromized because double the fuel has to mix with the same volume of air flowed making atomization difficult. Race cars that employ this configuration have resorted to pre-heating the fuel prior to injection and some even aim the injectors upstream to face the full brunt force of the incoming air for violent turbulence and maximum vaoprization.

These factors (and others) are probably the reason the majority of fuel-injection systems use batch-fired or semi-batch-fired fuel-injection(pairs staggered 360-degrees).

Another very simple explanation on the Cam/Crank angle sensors: https://www.hpacademy.com/technical-articles/how-does-an-ecu-know-what-cylinder-is-firing/

Joe Perez

iTrader: (8)

For a change, I agree with Savington. This thread makes my head hurt. So much half-correct information...

It's already been said, but I'm going to re-state for clarity:


All Miatas from 1990-2005 are capable of running fully sequential injection and ignition on just the stock sensors, provided that the ECU knows how to interpret the signals produced by the sensors. The output pattern of the NA CAS is a little unusual if you come from the old school of a crankwheel and a one-pulse-per-rev cam sensor, but it's just a different way of expressing the same information.



Adding a crank sensor improves the accuracy of the spark by eliminating the flex inherent in the cam belt (in EE terms, it decreases jitter), but this is a totally separate matter from running fully sequential vs. wasted-spark ignition. The spark will be just as accurate (or inaccurate) on a '90-'97 CAS whether you're running wasted-spark or sequential.



The aforementioned tuner is sadly misinformed. The '90-'97 Miata CAS produces both a crank reference and a cam reference. What the tuner is saying makes no sense at all. It's like he's thinking backwards. It would be impossible to run fully sequential on an engine with on cam sensor (eg: Ford EDIS-equipped engines), but whether an engine has a discrete crank sensor or one integrated into a cam sensor is irrelevant. Saying "you need a crank sensor to run sequential" doesn't make any sense at all. The fact that the engine ran in stock form at all (without a distributor) means that it must, by definition, already have a crank sensor or something equivalent to it.

I'm sure the guy is skilled with some piece of software, but he doesn't seem to know much about how engines work.








Doesn't really matter whether the ignition controller is built into the coils (eg: Toyota) or in an external box (Fab9). In terms of wiring and configuration, the two are basically the same.









Pretty much. The theories have already been covered, but the fact is that until you're running such high RPM that your cycle time is less than 2x the required dwell time, there's no signifcant advantage to fully-sequential ignition. If the coils have enough time to dwell, they're going to fire properly. Assuming a 4.5ms dwell time (stock coil), you'd have to run a wasted-spark engine at over 13,000 RPM before the cycle time impinges on the dwell period.



(Fully-sequential injection is a different story. The benefits there are real and observable, and are most significant at idle and low-load cruise. )










This thread is about ignition coils, not fuel injectors. Totally separate discussion.

codrus

OTOH, there's no real disadvantage to it either. You need to run a couple extra wires, but unless you're cutting the connectors off the factory harness (ick) you're doing that anyway.

Yeah, and the linked page appears to be about some weirdo 944 Porsche thing that doesn't work the way the megasquirt does either.

--Ian

Joe Perez

iTrader: (8)

Correct. No disadvantage, unless it causes you to needlessly spend money.




It also contains bad advice. Here's an excerpt from the section discussing the conversion to fully-sequential injection:





Notice where the end-of-squirt is relative to crank and intake valve position.

Mech5700

From my own experience, the fab9 coils worked great from NA up to about 10 psi. When I went up to 15 psi, j would get really bad breakup at higher rpm, full boost. I was using MS3 and wasted spark. I tried both versions of the igniter, tightened plug gaps down to low 20s, changed dwell and related settings, 2 different sets of plugs of different heat ranges, and could not get rid of the problem. I ended up cutting the white and yellow wires on the fab9 harness and ran them to the MS, and changed the settings to sequential COP. It helped slightly, but definitely did not make a big difference. I was able to find a set of toyota coils and a pnp harness someone had made up and tried that out, switched settings back to wasted COP and changed the dwell to the generic recommended Toyota COP settings posted on this site, and that finally solved my issue.

I don't think sequential is really necessary for most applications, and I also believe there is a somewhat common problem with the compatility of fab9s COP kit and MS3. I know fab uses his kits on some crazy high hp builds, but he also uses AEM for engine management...

Braineack

iTrader: (62)

Braineack

iTrader: (62)

Honestly, people would have a lot less issues if they stopped buying FAB9 coils*.


*I'm not saying this to bash a vendor, or to be an ***, but it's a clear fact they are more trouble than they are worth if they can't actually work correctly and provide better spark than stock coils.

Braineack

iTrader: (62)

you don't like to squirt fuel on a closed valve?

aceswerling

Ah, Mech5700 wins the prize! That was the information I was looking for. So the problem sounds like it's the Fab9 kit and not with batch vs. sequential ignition.

Mech5700, I'm sorry to hear about your trouble but I'm grateful you could help me avoid more of mine. I'm also happy if we can help others avoid this problem in the future.

I'll plan to remove the Fab9 kit and replace it with Toyota CoPs.

Braineack

iTrader: (62)

and like I asked before, are your FAB9 coils using the new or old module?

They made some sort of revision to the product after all the reports of simple coils not being able to work with MS (even though it can run any other coil on the planet)

aceswerling

I just bought this kit so I assume it's the "new" module. There are no markings on it so it's hard to tell exactly what it is.

I sent an email to Fab9 asking them to comment on this thread.