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Login to post Forums » Grassroots Motorsports » AEM EMS vs. Megasquirt PNP

March 31, 2009 10:37 p.m. MattP New Reader

Haven't posted here in a while, but I've got a 1.6L Miata with ITB's with the AEM EMS currently. It's tuned pretty decent, if a bit rich. The AEM software isn't the most user friendly in the world though. Still needs a little tuning.

I've got a 15% off coupon (up to $100) on eBay that expires the 2nd. I'm considering buying the MS PNP ECU off eBay, which would be at a price of $600, rather than their normal $700. I've heard good things about Megasquirt's software, particularly the logging and autotune functions.

Trying to decide if I should get the MSPNP and swap over to that, and sell the AEM.

Anybody have any experience with both or either engine management?
April 1, 2009 7:02 a.m. flexi New Reader

No personal experience with Megasquirt, but the guys at miataturbo.net have lots of experience with it. Check out their site. It is not as genteel as here.
April 1, 2009 7:15 a.m. RobL Reader

I like the AEM - used it to tune a 400+HP turbo MR2. It is a more powerful and complex EMS than the MS so I'm not sure that I would downgrade.
April 1, 2009 7:22 a.m. m4ff3w Dork

RobL wrote:

I like the AEM - used it to tune a 400+HP turbo MR2. It is a more powerful and complex EMS than the MS so I'm not sure that I would downgrade.

What makes AEM "more powerful and complex"? What exacty can one does with AEM that one can not do with MS2 (especially MS2/Extra)?
April 1, 2009 8:01 a.m. YaNi Reader

AEM does sequential injection if that matters.
April 1, 2009 8:30 a.m. Paul_VR6 New Reader

Have you been tuning the AEM yourself, plan to do the same with MS? What exactly is holding you up with the AEM?

I don't like the AEM at all, and quite a few other standalones like anything from Electromotive and DTA.

I've been working with MS for a long time, and at the very least you'll be able to find someone to help with your problem for free over the internet. It's hard to buy that with another system.
April 1, 2009 9:42 a.m. fiat22turbo SuperDork

I believe sequential injection is only really useful for idle emissions and idle NVH. Once you get farther up in the rev range of the engine, sequential only gives you slightly better tuning per cylinder (which should only be needed on poorly built intake manifolds)
April 1, 2009 10:16 a.m. RobL Reader

Well, the AEM does sequential injection. Which is more powerful than batch. It's not just emmissions, it's also power/efficiency in the lower rev range. If you have an injector spraying onto the back of the valve, that fuel is not vapor anymore and it will give a less consistant burn and you can't run as much timing. The less consistant burn is what affect emmissions. MS says idle to low speed cruising but, in my case with big injectors, I found it happened midway through the rpm range and slightly into boost.

I was also running traction control, launch control, two-step limiter/flat shifting, high and low boost settings, agressive/non-agressive fuel and timing tables, etc. I could let my wife drive the car to the store and it would be quiet and sedate to drive - hell she could fill it with 91 octane gas. But when I sat down (and with race gas in the tank), I could throw a couple of switches and run 11s.

If all you're doing is changing the fuel/spark tables, maybe the MS is for you. But I was doing more and needed the more powerful EMS.
April 1, 2009 10:46 a.m. fiat22turbo SuperDork

If you read my message, I alluded to that.

BTW, I could run 11's using a turbo-dodge running stock, batch fire electronics and still get decent mileage around town! I know of a minivan that regularly drives the kids to school and can run 11's later that night. That is the magic of turbocharging and electronic fuel injection.

All of your software may have made it easier to launch without having to make your right foot more intelligent, but MegaSquirt can do launch control, anti-lag, flat shift, alternate tables, boost control, etc. Just get the necessary source code, hardware and set it up.

It all comes down to what your skill set is and where you want to spend your time. MegaSquirt isn't for everyone as it is somewhat limited in its capabilities at times. Sequential injection is a huge issue for many people, especially people who are really trying to maximize the area under the curve.

Don't get me wrong, I'd love some sequential injection, but it isn't important enough to me to spend the extra money to get there. I'd rather start out with batch injection and work upwards from there. Eventually someone will figure out how to add sequential injection to MS and by then I'll be ready to make that switch.
April 1, 2009 10:52 a.m. Paul_VR6 New Reader

Sequential does spray at the back of the valve when it's closed, otherwise it would wash the far side of the wall of oil, and lead to abnormal wear.

From a power perspective batch vs seq doesn't seem to matter. Here is a same day dyno of a very good chip tune of Bosch Motronic 2.9.1 vs Megasquirt. The Bosch system is seq:

The dyno doesn't start THAT low but you can see there are no losses of low end, at least none that weren't remedied with tuning. The real gain with seq in my mind is doing very accurate accel enrichments, and the AEM ecu doesn't even include the tools to do such schemes.

I'm not sure about the PnP setups, but Megasquirt (with extra code) can do all that. The board/mods I run in my personal car include launch control, flat shift, tach output, table switching, fan control, two shift lights, and an experimental output (boost control) that I'm doing some vvt work with.
April 1, 2009 10:58 a.m. MattP New Reader

Wow, thanks for the responses, this is very instructive (and of course it's not making the decision any easier).
April 1, 2009 11:01 a.m. MattP New Reader

And I've been kind of picking up where the previous owner left off with the AEM. It's tuned very well right now for full throttle full load situations. It does tend to hesitate when the throttle is opened suddenly (like a carb with a too-large accel pump jet), or at constant speed at low load.
April 1, 2009 11:39 a.m. Raze Reader

Getting off-idle and part power response 'right' is one of the hardest jobs on any tune using any controller IMO...

It took us probably 3 times more time to tune the lower part of the map than it did the upper, and we had to increase the resolution down there to improve response, this is with a MS-I V3.0 board w/MSnS code...
April 1, 2009 12:28 p.m. Paul_VR6 New Reader

Agreed, tip in is a killer especially with throttle bodies. Generally though if it's a stutter, you're too lean. If it feels like a bog, you're too rich. If you can post up a log, or even rpm/tps/wideband values I can give suggestions.

Even though I do most of my work with MS, I can appreciate when you want to try and make something that you already have work right.
April 1, 2009 12:33 p.m. evildky Dork

I say run what you are comfortable with, megasquirt does have a learning curve, but can be very rewarding, and as others have pointed out isn't for everyone, but does have a fantastic support community, I have no experience with the aem but I find the ms to be quite rewarding and user fiiendly once you get your head wraped around it
April 1, 2009 1:49 p.m. fifty New Reader

I have Megasquirt in ma hooptie, a fellow autocrosser has the AEM in his Miata. Although the MS may be plug and play, the AEM had launch control/flat shift as standard and knock sensing retard(MS PNP does not, to my knowledge). We fine-tuned the Miata maps last year at an event and it seemed easy enough.

I have the MS-Extra board with all the missing features of MS PNP. It's only a $50 - $120 board (depending on the features you want) but it's not exactly "plug 'n' play" , esp. for a new-comer.

I'd say keep what you have.
April 1, 2009 7:43 p.m. MattP New Reader

Thanks everyone for your help! I did a bit more reading and I think I just need to do a bit more learning the AEM software. I think if I was getting something where I had nothing, I'd get the MS system, just because of the comparative cost.

I'm sure at some point in the future, I'll end up putting Megasquirt on a car, though. Particularly one that didn't originally come with EFI.
April 1, 2009 8:14 p.m. ronbros New Reader

some standalone EMS cost only $700, and some systems can cost $7000. now you mean there is no difference between them,,,thats hard to understand.
April 2, 2009 8:45 a.m. Paul_VR6 New Reader

There are differences, obviously, but it really depends on what you're trying to do and with what kind of budget.

In my mind there are two choices Megasquirt and Motec. Everything else in between isn't worth not having the best instead of the most powerful per unit dollar.
April 2, 2009 1:03 p.m. Xceler8x Dork

flexi wrote:

No personal experience with Megasquirt, but the guys at miataturbo.net have lots of experience with it. Check out their site. It is not as genteel as here.

That's like saying Antarctica isn't quite as warm as Death Valley.

Go to miataturbo.net at your own risk. You might have more luck either talking to www.diyautotune.com directly or rummaging around the megasquirt forums.

I just installed an MSPnP into my Miata. Tuning with mega log viewer is almost automatic. Drive around, datalog the drive, let mega log viewer analyze it, save the msq file. The msq file is where MsPnP get it's settings from. Go about it this way and it tunes itself.

MSPnP also has:

~ flat shift

~ traction control

~ launch control

~ etc.

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