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Question for those who have added an aftermarket EMS (Electromotive, Megasquirt, etc)
I've read a number of threads on Megasquirt (there doesn't seem to be any about Electromotive), and in one it was mentioned that they don't need the AFM. Is that true for Turbo cars only, or is it also the case for N/A engines?
True for any engine... AFM-less on my early NA. The reason is that the algorithm the ECU uses to determine the amount of fuel to inject is different. With the stock Motronic, obviously it uses the AFM to look at air flow into the engine. That flow of air mass determines how much fuel is needed to maintain a target air/fuel mixture. With most standalones like Electromotive or MS, you use an approach called "speed density" where you don't need the AFM's input. It uses manifold air pressure (MAP), intake air temp (IAT), the speed of the engine, and a programmed "volumetric efficiency (VE)" to get to the same conclusion. However, you can program a standalone to use an AFM or a MAF if you wanted to for some reason.
True for any engine... AFM-less on my early NA. The reason is that the algorithm the ECU uses to determine the amount of fuel to inject is different. With the stock Motronic, obviously it uses the AFM to look at air flow into the engine. That flow of air mass determines how much fuel is needed to maintain a target air/fuel mixture. With most standalones like Electromotive or MS, you use an approach called "speed density" where you don't need the AFM's input. It uses manifold air pressure (MAP), intake air temp (IAT), the speed of the engine, and a programmed "volumetric efficiency (VE)" to get to the same conclusion. However, you can program a standalone to use an AFM or a MAF if you wanted to for some reason.
Great info - thanks very much! Does the MAP get installed on the manifold itself? As for the intake hose from the air filter to the manifold, can it now be a single, uninterrupted run from the filter to the throttle body? And would there be any advantage to also using a MAF - would maybe you maybe get a more accurate reading?
The MAP sensor can go anywhere between the throttle body and the individual intake runners. Your goal is to get a smooth/steady pressure reading of the manifold. On my NA I physically mounted it on the throttle body and ran a small vacuum line to one of the nipples on the side of the throttle body. It's the same vacuum port that the FPR and damper use, so it's easy to tee into. But you can see that there is flexibility with where you put it which is nice.
As for the intake hose from the air filter to the manifold, can it now be a single, uninterrupted run from the filter to the throttle body?
yes, but don't forget about things like the PCV and brake booster vacuum connection. If you want to retain that functionality, make sure they can still get vacuum. On my setup, I just left it all as-is and replaced the AFM itself with a blank tube. I stuck the intake air temp sensor in that tube, it looks clean and is effective.
The MAP sensor can go anywhere between the throttle body and the individual intake runners. Your goal is to get a smooth/steady pressure reading of the manifold. On my NA I physically mounted it on the throttle body and ran a small vacuum line to one of the nipples on the side of the throttle body. It's the same vacuum port that the FPR and damper use, so it's easy to tee into. But you can see that there is flexibility with where you put it which is nice.
yes, but don't forget about things like the PCV and brake booster vacuum connection. If you want to retain that functionality, make sure they can still get vacuum. On my setup, I just left it all as-is and replaced the AFM itself with a blank tube. I stuck the intake air temp sensor in that tube, it looks clean and is effective.
Great - thanks very much! Is there any advantage to running a MAF instead of or in addition to a MAP?
Last edited by AkechiMotors; 12-13-2015 at 04:56 PM.
Any good standalone will support both, and in most cases blending. For example, using MAF at low engine speeds and then blending in MAP calculations later on. I have no issues with only MAP on my 2.5, I looked at MAF (as I had one from Rogue) but passed on it. For an NA both are going to get the job done better than the AFM ever could in terms of accuracy, sampling rate, response time, reliability, repeatability, hysteresis, and not impeding the intake tract.
Any good standalone will support both, and in most cases blending. For example, using MAF at low engine speeds and then blending in MAP calculations later on. I have no issues with only MAP on my 2.5, I looked at MAF (as I had one from Rogue) but passed on it. For an NA both are going to get the job done better than the AFM ever could in terms of accuracy, sampling rate, response time, reliability, repeatability, hysteresis, and not impeding the intake tract.
Very helpful link - thanks. It looks like there aren't really any significant advantages to going with one over the other (or blending both) in most street applications. I was going to do a MAF conversion and EMS later, but it looks like I can skip the MAF conversion and put that money to EMS.
One last question: My car has airbags and ABS - do those run off the DME, or are they controlled by something else? I'd rather not lose them if I can help it.
12-13-2015, 12:44 PM
Question for those who have added an aftermarket EMS (Electromotive, Megasquirt, etc)
