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Aem Ems: Gotchas?

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Old 07-07-2004, 03:30 PM
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Default Aem Ems: Gotchas?

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I am planning to replace my VAFC with EMS. What standard/stock features or functionality will I lose? (I recall reading that I'll lose the immobilizer)

And will I still get system warnings? For example, while I have complete faith in the tuner to make the car run smoothly and safely, I don't trust myself with user errors and would like to get thrown a CEL warning for not tightening the gas cap, etc.

TIA
Old 07-07-2004, 03:34 PM
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Since the EMS is not OBDII legal, you will not have any DTC's for the catalytic convertor, air pump, or evaporative emmisions systems. You also won't have a coolant temp gauge in the stock cluster that works. The EMS doesn't support an output to the stock cluster. As you already know, no immobilzer.

I'm sure there are more, I just don't remember them all.
Old 07-07-2004, 05:07 PM
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No ODB-II means you'll never pass emissions testing. When you have your emissions tested, you need to put back your stock ECU and setup.

At least in IL, if the ODB-II doesn't work, they wont even test your car. Also, first thing the dealer does when you bring your car for some trouble is check DTC's via the ODB-II computer. They may not be able to troubleshoot your problems without knowing the fault codes. So you better be good with the wrench.

Furthermore, your idle may not be as good as the stock ECU. Stock ECU does lots of things to ensure good idle. I think there may be capability in the AEM EMS, but knowledge of what to have it do and when is what's key.

Also, some protection will be lost. I.E. no limp home modes and so forth when something does give out.
Old 07-07-2004, 10:50 PM
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i thought u could add perimeters to it to make a "faux" limp mode
Old 07-07-2004, 11:16 PM
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Just got my AEM and am concerned about some of these issues. OBDII is no issue as we don't have it on Aus cars.

But the coolant gauge is. My tuner suggests running the stock ECU in parallel but not letting it control the injectors or ignition. That way it will still control the cluster and other functions, but the AEM will control the tuning. I'm having VTECFROG make up a special harness so I can tap the wires I need for the oem ECU and leave the rest disconnected.

Any thoughts?
Old 07-07-2004, 11:45 PM
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instead of going through all of that .........
why not just get a coolant gauge?
Old 07-08-2004, 12:53 AM
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I'm not sure that's going to work with two ECU's. It's going to be tough to figure out which signals to go to which control. And in some situations signals may need to go to both, which may not work with current and resistance changes running them in parallel.

What most people do is just throw a CEL if the ECT gets too hot. It's not as good as a working gauge, but it works.

Also, check out http://www.gauge-tech.com for a gauge idea that plugs into the EMS. I give it two thumbs up. I'm looking at putting a dash with AEM. But for now that display is great.

Haven't had problems with idle with an S/C.

Also, plan on getting a wideband O2. You will need it for O2 feedback. Actually, idle will suck without a wideband O2. That may be why some people have problems with idle.
Old 07-08-2004, 01:56 AM
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I don't want the whole 'gauge in pod' look. I might go for the Defi VSD Concept HUD gauge, but if I can get the stock cluster working I will be very happy.

My tuner has done this already with a Motec on an S2000 so it isn't exactly uncharted territory.
Old 07-08-2004, 02:54 AM
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How much does a wideband O2 cost? I am about to do the whole set up soon. thanks
Old 07-08-2004, 08:23 AM
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Thanks for the feedback. It's making me reconsider eManage.


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