I'm contemplating swapping a 1.8 into my '92 Miata and running it with Megasquirt. I'm brand new to Megasquirt. What's it like to live with a Megasquirt on a daily driver? Will I end up with a reliable workhorse? Or a science project that's never 'quite right'?
I've watched a buddy struggle with another brand of aftermarket ECU for years. I'm looking for an ECU, not a years-long time killer.
How reasonable is it to want the following out of a Megasquirt?
Want:
Easy starting (hot starts too)
Passing emissions doesn't become a major headache
Charcoal canister purge valve works similar to stock.
ECU knows to bump idle when A/C is on.
After learning the software & some dyno sessions, to have a car that runs well and is reliable.
Dont Want:
A car that runs well most of the time, but is flaky somtimes
A car that constantly smells of raw fuel because the evaporative emissions controls no longer work.
I know MS3Pro will do ALL of that because I've done installs that kept purge control.
Emissions testing is tricky. You may have to do some experimenting to get an ignition timing curve that doesn't blow NOx out of the water. But that, closed loop control at stoich, and a GOOD three way cat will always pass a sniffer test.
I've had MS on my RX-7 since '08ish and it's fine. OLD school MS, Bowning & Grippo base code in a 1.01 group-buy box. Turn key and drive. The only issues I generally have are related to the engine, not the tuning. (You can't start a nasty engine with heat range 10 plugs and expect it to warm up without some nursing)
All of my installs have been on older cars without evaporative emissions bits. I have about 5 years of daily driving MS1 and MS2 installs. Never any issue besides being vastly superior to what ever was there before (carbs and Kjet)
92 is pre OBD2 which means in Oregon a visual check for a cat and gas filler restrictor, and an idle sniff test.
Late last year I ran a mid 80's 740 +T with MS2 through DEQ and left the MS out on the floor and a lap top with a TS window open on the pass seat. Passed on first try.
I don't think a 92 has electronic purge control even if it does you can easily set it up to purge in closed loop cruise.
Idle strategy is easy with closed loop idle and a bump in the timing map below target idle.
Not sure what a Miata uses for an Idle valve but you can always do a Bosch 2wire or a GM 4wire.
I would not hesitate to run MS on a daily, I don't think much of the CAS but you can easily do a crank trigger and wasted spark.
bentwrench wrote:
I would not hesitate to run MS on a daily, I don't think much of the CAS but you can easily do a crank trigger and wasted spark.
What's the down side of using the CAS?
I just don't care for a distributor, tail wagging the dog...
Distributors can integrate into EFI just fine.
The Chrysler JTEC PCMs have dummy distributors from the factory on most of the engines they came with (no advance mech in the distributor or anything). They have a crank sensor that determines when it fires spark, and a cam sensor in the distributor that determines TDC on cyl 1 for injector timing.
Weirdly, this means that turning the dist doesn't affect ignition timing (which is all controlled via the PCM), but it does affect injection timing (which can't be changed in software). Kinda weird, but it works.
Ran it for a few years in my ITB'd 79 Porsche 924 as a daily.
Worked great, passed emissions without issue.
Any issues I had with it were either the car itself or my own idiot self for making too many changes to the engine itself (cam, header, ITB's, ignition and EFI, etc.), once I stepped back to a single throttle body the drivability improved greatly.
Wasted spark has more dwell time thus more spark energy.
MS2 will do COP sequential spark on a 4 cyl or COP wasted spark on an 8 cyl.
Jumper K. Balls wrote:
All of my installs have been on older cars without evaporative emissions bits. I have about 5 years of daily driving MS1 and MS2 installs. Never any issue besides being vastly superior to what ever was there before (carbs and Kjet)
All cars that had K-jet had "evaporative emissions bits" if they were sold in the US. IIRC it was introduced in California in 1966 and 49-state in 1968.
Granted it WAS very crude. But at the same time, all those vacuum hoses and switches and stuff were there because they couldn't simply pulse a purge solenoid yet.
I'm planning on adding that stuff to the RX-7. Actually, I am also planning on using a vent solenoid as a PCV valve, since teh bridgeport simply Does Not Work with a PCV system, the vacuum leak makes the idle way too variable, and the simplest solution is to have a computer controlled crankcase vapor purge. I mean, I could have a vacuum operated diaphragm that uses ported vacuum and a thermal switch to only allow PCV action when the throttle is cracked open and the engine is warm, but that isn't as elegant.
Current breather setup is "a tube sort of goes up near the air filter" and fuel tank evaporative system is "a hose sort of ends at the firewall and sometimes dumps raw fuel on the header, which evaporates it". FPO deleted the emissions rack because he was afraid of hoses or something, and I never got around to fixing it.
Well, it's been like 8 or 9 years since I bought the car, if I haven't done it yet then I probably won't do it ever...
LuxInterior wrote:
bentwrench wrote:
I would not hesitate to run MS on a daily, I don't think much of the CAS but you can easily do a crank trigger and wasted spark.
What's the down side of using the CAS?
On an RX-7, jitter and lag. This is with a CAS driven directly by the crank, not a belt driven camshaft.
Someone with MS (the disease) could be offended seeing the title, then again, ppl with MS probably don't frequent automotive racing forums... So it works.
I'm glad this is about Megasquirt. When I saw the thread title I thought "Crap; now the GRMs that aren't getting the cancer are getting Multiple Sclerosis".
motomoron wrote:
I'm glad this is about Megasquirt. When I saw the thread title I thought "Crap; now the GRMs that aren't getting the cancer are getting Multiple Sclerosis".
Ditto. I know a couple people with MS. not good stuff
fwiw both of my dailies run MS2e. Neither one has purge control, but I haven't had any issues with smelling like gas. My only reliability issues have been surrounding the Innovate widebands. The E30's has actually been alive for awhile now after killing a few sensors in a row, but the wagon just ate its first sensor after only 5k miles.
Not an Innovate fanboi, but they don't make the Bosch sensors.
Is there another MFGR?
Some notes- not specifically about MegSq (and yes, the MS part threw me off, too...).
Most purge systems I've worked with do some specific flow compensation for both fuel and air when it's on. Some it's really a big deal, others, it's not. But the important thing is that some adjustment is needed, as you are changing the fuel.
So- for it to be pretty robust without any compensation- I'd suggest running a WB set up- that way, the extra fuel/air added is easier to trace.
I also don't know if MS does any learning- so that the air or fuel flow is slowly adjusted over time to account for any sources of drift. If it does, you need to make sure it's not running when doing the purge work- that would not be drifting- that's introducing a known errors state that you don't want to compensate for.
As for the flaky running- unless there are some serious electronic issues with MS (which I don't think there are anymore) the quality if how it runs is entirely up to how good the calibration is. Just like production cars.
motomoron wrote:
I'm glad this is about Megasquirt. When I saw the thread title I thought "Crap; now the GRMs that aren't getting the cancer are getting Multiple Sclerosis".
Thought the same thing...
I've only driven on my MS3X-run 4AGE for under an hour but it's rock-solid reliable so far 
Aren't you right up against the point where the 92 doesn't have to pass emissions anymore? Isn't this year or next your last emissions test?
Harvey wrote:
Aren't you right up against the point where the 92 doesn't have to pass emissions anymore? Isn't this year or next your last emissions test?
Just because you don't have to doesn't mean you don't want to. I'd like to put emissions hardware on my '73 Alfa, as I'm tired of the smell and headache with driving it.
Harvey wrote:
Aren't you right up against the point where the 92 doesn't have to pass emissions anymore? Isn't this year or next your last emissions test?
Colorado requires emission tests on cars all the way back to the 1982 model year.
Colorado requires emission tests on cars all the way back to the 1982 model year.
Oh, ew.
Also, I drove my Miata on an MS3x for a while and never had an issue with starting.
