AEM Engine Management System (Q & A)

[RacerX-21]

I was happy to see the info on the knock sensor calibration, the first time I turned them on they were off the chart… and that was at 11:1 AFR with little timing.

When I’m ready to tune again, I will call you.

About the EGT’s- how many? Or all?

Amazing things can be learned on the dyno, I worked with cam timing to pick up almost 100 HP and better fuel mileage! When I re-dyno’d I had to take a ton of fuel out of it, it didn’t seem to make sense… at first; More Hp = more air = more fuel, but originally I was actually pushing unused boost and fuel out the exhaust. Unfortunately after 17 degrees, I finally ran out of valve clearance so it’s time to rebuild. I cut about .200" more clearance then a stock piston, but who would have ever thought 17 degrees.

For everyone reading- the cam is not stock, but it is a spec cam that I have to make the best of.

 

[HorsepowerFreak]

New products for the AEM EMS...

Here's a pic of the new AEM display we're selling (made by gauge tech). This can be dash mounted. It will provide you with various engine parameters when you don't have your laptop connected. It simply plugs into the same serial port that the laptop plugs into. Very cool.

Take care,
Chris.

 

[Yellow Rose]

Even though I am not an AEM user, this is an excellent thread. The above display is also a very cool feature. That said, I have a few questions about some of the shown data.

Wheel torque of 16 FT-LB, how is this determined?

Injector duty of 196%?

How can idle be 79% when the engine is at 3047 RPM?

Air-fuel ratio of 18:1 at steady-state driving is too lean. It should be +/-14.7:1.

Air and coolant temperature of -54°C = -65°F?

 

[HorsepowerFreak]

Very valid points. Those numbers are erroneous. I believe he was simply testing the unit when he took the picture.

I'll hook one up early next week to one of our AEM cars here and snap some pictures while the car is running.

 

[sjs]

This display head is OK, but rather impractical to look at while driving given the amount of data on a small screen. Even a passenger might find it a challenge. If the layout is user programmable (as is with the PC based displays) then perhaps the entire screen could be devoted to fewer key parameters in a larger font.

Something else I hope it can do is start, stop, and replay the ECU internal data log at the push of a button.

Together those features would put it on my wish list.

 

[HorsepowerFreak]

Here's the list of its functions.

www.horsepowerfreaks.com/productdescriptions/DIGITALDASH.doc

It has quite a bit of functionality. I don't think it can do play-back however.

Chris.

 

[sjs]

Q for Sean & Chris

Back when I was tinkering with my AEM I noticed a pronounced saw tooth shape in the A/F log. I could tune the A/F essentially flat, or at the desired slope, but zooming in revealed a very obvious "wave", approximately 1/2 second peak to peak and more than 1/2 A/F point in amplitude. To be more precise about the wave shape, the top is somewhat flat and the bottom quite V shape pointed. Half square wave, half saw tooth.

It appears at virtually all load and RPM ranges above idle and does not seem to change shape or amplitude under changing conditions.

I was not able to detect a fluctuation in fuel pressure although I thought perhaps the regulator return orifice was being overwhelmed. But then I found it also existed on a second NSX I was tuning, also with an AEM but a differ rent regulator.

Any idea what might cause that?

 

[HorsepowerFreak]

Sean is on a tuning trip in Detroit. I'll see if I can get him to dial in and reply when he's free. Otherwise he'll get back to you on Monday.

Take care,
Chris.

 

[ALIENT]

How does one attend the 'Beginners AEM class' that someone mentioned? I didn't see anything on their site.

 

[sjs]

Here's the list of its functions. ...

It has quite a bit of functionality. I don't think it can do play-back however.

Chris.

It appears to have something close to my first wish, displaying the first four selected parameters in a larger font. That's decent. But the ability to start/stop/playback the internal data log is huge IMO and makes the difference between a useful tool and a mere gadget.

 

[HorsepowerFreak]

Re: Q for Sean & Chris

Back when I was tinkering with my AEM I noticed a pronounced saw tooth shape in the A/F log. I could tune the A/F essentially flat, or at the desired slope, but zooming in revealed a very obvious "wave", approximately 1/2 second peak to peak and more than 1/2 A/F point in amplitude. To be more precise about the wave shape, the top is somewhat flat and the bottom quite V shape pointed. Half square wave, half saw tooth.

It appears at virtually all load and RPM ranges above idle and does not seem to change shape or amplitude under changing conditions.

I was not able to detect a fluctuation in fuel pressure although I thought perhaps the regulator return orifice was being overwhelmed. But then I found it also existed on a second NSX I was tuning, also with an AEM but a differ rent regulator.

Any idea what might cause that?

I just spoke with Sean on the phone. He said email him the log and he'll check it out for you. [email protected]

Take care,
Chris.

 

[Sean McElderry]

There are a few things I can think of that would cause the saw tooth pattern you observed.

1) Noise on the AFR line.
2) Noise on the AFR ground.
3) AFR ground at a different potential than chassis (EMS) ground.
4) Noise in the EMS itself.
5) Bug in the AFR #1 (O2 #1) parameter.
5) O2 feedback altering the mixture.

I've never seen anything like what you described. Do you have a log you can send me?