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Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
4/30/10 10:11 a.m.

I am in the process of spec'ing out a Megasquirt setup to replace my dead ECU on the E30 of doom... seems I can do a whole MS-II kit for what a junkyard unit + custom burn would cost for the S52. I do love a cost effective opportunity to frustrate myself for weeks!

Its looking to be kindof a PIA to get sequential firing to work as the factory cam angle sensor is not supported. I can't really think of a downside to running wasted spark except that there is just more wear on the plugs and it will burn any unburned fuel before it goes back to mother nature. This is a race-only application - is there any high RPM consequence I'm not aware of or am I over-thinking it and should just roll with the easy answer?

Also, any noob advice is welcome. I'm pretty electronics saavy and can see clear to the end of the installation quite easily but I'm new to tuning vtables - so if you have the "idiots guide to foolproof setup" I'd be much obliged so as not to hole a piston the first time I hit the track.

Keith
Keith SuperDork
4/30/10 10:14 a.m.

Almost every Miata runs wasted spark. Maybe your plug wires will wear out earlier, but I don't see a big downside myself.

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
4/30/10 10:21 a.m.

@Keith - its a COP setup so no wires... coils might heat up more though. I'm honestly not sure if BMW doesn't use wasted spark by default for emissions.

Anyone know?

Dr. Hess
Dr. Hess SuperDork
4/30/10 10:24 a.m.

Harley's have run Wasted Spark since before time began. SBC's do it. Esprits, Camrys, Corollas and Tacomas too. It's actually easier and better because you have fewer moving parts. Never replace a rotor and cap again and get full voltage through from the coil to the plug instead of losing a bunch at the gap between the cap and the rotor.

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
4/30/10 10:28 a.m.
Dr. Hess wrote: Harley's have run Wasted Spark since before time began. SBC's do it. Esprits, Camrys, Corollas and Tacomas too. It's actually easier and better because you have fewer moving parts. Never replace a rotor and cap again and get full voltage through from the coil to the plug instead of losing a bunch at the gap between the cap and the rotor.

Well, I had no moving parts - the car had Bosch injection with coil-on-plug and a hall sensor pickup on the crank before - I'm just trying to estimate if there is any issue at all with sparking the exhaust at 8k rpms and it does not sound like there is - which is sweet because its easier to wire and leaves me extra i/o on the ms board for triggering other cool idears I had.

Dr. Hess
Dr. Hess SuperDork
4/30/10 10:35 a.m.

Yeah, I don't see a problem with that. You're still only firing the coil a fraction of what it would if it was trying to fire all the cylinders.

itsarebuild
itsarebuild Reader
4/30/10 11:19 a.m.

from what i rember reading in the mega manual (if you can remebre anything after reading 100+ pages of a manual) the only time wasted spark would be an issue is if you turn enough rpms that the time to charge the coil is less than the time between firings. if i recall correctly the manual estimated that this doesnt happen until about 20K rpms in most single coli applications (they were discussing putting it on crotch rockets) . given that you have a coil for each plug i guess you could multiply that 20K by the number of coils to find your rpm limit.

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
4/30/10 11:47 a.m.
itsarebuild wrote: from what i rember reading in the mega manual (if you can remebre anything after reading 100+ pages of a manual) the only time wasted spark would be an issue is if you turn enough rpms that the time to charge the coil is less than the time between firings. if i recall correctly the manual estimated that this doesnt happen until about 20K rpms in most single coli applications (they were discussing putting it on crotch rockets) . given that you have a coil for each plug i guess you could multiply that 20K by the number of coils to find your rpm limit.

Well, then in this case... id be firing 2 coils for each rev of the crank, so each coil would fire once every 3 revs. The limit is 7800rpms, so 2.6k/mi is ~44x/sec. I will have to research the rise time for the bosch coils but that seems like a pretty long time spent doing nothing so I think it will be ok even though its double the rate of sequential.

foxtrapper
foxtrapper SuperDork
4/30/10 1:09 p.m.

Japanese motorcycles have run wasted spark ignitions for as far back as they've had motorcycles. They've made plenty of screaming rpm engines that worked just fine with that setup. I don't think you've anything to fear from it rpm wise.

GameboyRMH
GameboyRMH SuperDork
4/30/10 1:21 p.m.

I did some research on it once and couldn't find any real downsides. I'd heard of some aftermarket systems using dual coils or coil-on-plugs but single coil setups on cars seem to be pretty common.

Upside: It might be a little more enviro-friendly.

44Dwarf
44Dwarf HalfDork
4/30/10 1:24 p.m.

Most motorcycle motors run wasted spark and they spin 14500 so i can't see it causing any problems. So little power goes to the no working plug i doubt you'd see a difrerance in wear infact you might find they last longer do to running cleaner.

44

Paul_VR6
Paul_VR6 Reader
5/2/10 7:44 p.m.

Just run the COP's in waste pairs, unless you need a Berkleying huge dwell, it'll work great.

PS: whats the cam wheel look like? Usually if you can get it wired up and get logs they'll write code for it if you ask real nice.

MadScientistMatt
MadScientistMatt Dork
5/3/10 9:10 a.m.

It's not the shape of the wheel as much as it's an abnormal sensor type, neither Hall effect nor VR. The wheel itself is a normal 1 tooth cam wheel.

sobe_death
sobe_death Reader
5/3/10 1:26 p.m.

Contact DIYautotune about it. I'd ask my friend with DIYPNP on his e30 what he has setup but he's out of country right now. Pretty sure it's wasted spark

Paul_VR6
Paul_VR6 Reader
5/3/10 1:53 p.m.

There's only so many choices for what that cam sensor could be. If he's got one to send out, I could probably get it to work somehow.

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
5/3/10 1:56 p.m.

@sobe_death... I had been talking to DIY but you know... gotta see what the board thinks too.

On the subject of DIYAutotune I'd like to thank Matt for answering all my inane questions and Nanette for putting the last available harness in my order [ I mean it... I'm not just greasing you guys up for a barrage of future questions when the box arrives... ;) ]

These guys are a fine example of how customer service should be done.

MadScientistMatt
MadScientistMatt Dork
5/3/10 3:13 p.m.
Paul_VR6 wrote: There's only so many choices for what that cam sensor could be. If he's got one to send out, I could probably get it to work somehow.

It's a variable transformer with the two coils connected at one side. The stock ECU drives one with a high frequency sine wave and measures the phase shift of the response on the other side. Very weird.

sobe_death
sobe_death Reader
5/3/10 4:02 p.m.
Giant Purple Snorklewacker wrote: @sobe_death... I had been talking to DIY but you know... gotta see what the board thinks too. On the subject of DIYAutotune I'd like to thank Matt for answering all my inane questions and Nanette for putting the last available harness in my order [ I mean it... I'm not just greasing you guys up for a barrage of future questions when the box arrives... ;) ] These guys are a fine example of how customer service should be done.

Yeah they are good people. They are also the tuners of the E30 I mentioned above!

pres589
pres589 Reader
5/3/10 4:25 p.m.

I know it's not as sexy and you give up some control of the engine management but couldn't the stock ECU be kept around for spark control and use the MS for fuel? This is assuming you don't mind giving up rev limiter control.

It's what I am considering if I ever get the guts to rip into my VFR and use a Microsquirt. Maybe a good winter project and it avoids this kind of issue.

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
5/3/10 4:46 p.m.
pres589 wrote: I know it's not as sexy and you give up some control of the engine management but couldn't the stock ECU be kept around for spark control and use the MS for fuel? This is assuming you don't mind giving up rev limiter control. It's what I am considering if I ever get the guts to rip into my VFR and use a Microsquirt. Maybe a good winter project and it avoids this kind of issue.

THe stock ECU died, so... rather than pony up ebay money to get another one and then have to pony up again to have someone provide a custom tune I decided to remedy the problem once and for all. I'm stoked for my box to arrive, I even bought a new tip for the iron just for the occasion.

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
5/3/10 4:49 p.m.

As a self-threadjack - anybody know where to source Bosch pigtails/clips for BMW 2 & 3 wire sensors and injectors so I don't have to dismember a good engine harness? (Aside from the junkyard to dismember one I don't already own, I mean)

pres589
pres589 Reader
5/3/10 4:56 p.m.

Ouch, duh, point well taken.

erohslc
erohslc Reader
5/3/10 5:23 p.m.

In reply to MadScientistMatt: Ahh, industrial proximity sensor technology. (but for God's sake, why?)

Paul_VR6
Paul_VR6 Reader
5/4/10 7:38 a.m.

Eagleday has most of the connectors, but after you look at that you'll head to the junkyard with your snips!

If you have a good double crimp tool, I probably have those connector pins here somewhere.

Matt, thanks for the info. Interesting way for them to do it, but pretty clever. I guess it's used to detect the VVT actuation as well, hence the need for the phase shift.

Tetzuoe
Tetzuoe Reader
5/4/10 9:25 a.m.

I thought there was no dark side since its sparking then.

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