Learning to use AEM and engine map in general

[arnout]

if you got the lean spot when you tap the throttle, I would dig into the accell fuel tabling first. The base map is used when you don't really accellerate.

[TLicense]

The thread from the dead....

[b_have]

So what was the upshot Tony? Would be interested to know, did you go to Thor? Any dyno results?

[TLicense]

Well, as it happens.... no.

 

As I've got a lightweight flywheel, it makes the gearbox rattle like a goddamsonofabitch at anything below 1000rpm. So I raised the idle to 1100 which quietened it all down (still there though, just better than it was) This meant that I was no longer driving through the "flat spot", so basically I've done nothing else about it.

 

To be honest, I need to look completely at rebuilding a map for my car, as I'm not happy about it at all. I've been driving a few other cars (not supra's) over the past couple of weeks, and they are about a million times smoother on light throttle than my supra. I don't know if this is down to the mapping or the flywheel, but I get a hell of a lot of "bucking" when applying small throttle. I'm confident it's not DFCO, (although this does make it marginally worse when it is on).

 

I'm sure it's something that a top mapper could sort out in a matter on minutes, but I really can't afford their prices, and I would really like to fix it, and learn some stuff, myself.

[eyefi]

bucking is not the flywheel, it's the tune.

 

do you want me to send you my stock twins & fuel IGN & INJ maps. they ran like stock on my powerfc, not that i'd recommend just dumping them in and using them blindly.

[TLicense]

It would be interesting to compare the ignition map, but unfortunately the fuel map would be next to useless, as I know that Leon raised the fuel rail pressure, and I had a rising rate fuel regulator fitted. So lord only knows how much fuel volume is actually entering the cylinder for 1ms of injector opening.

 

The bucking I could best describe as if on v.light throttle there is just an on/off switch on the throttle pedal. ie off is 0% throttle on is 5% throttle. I know that my TPS is set correctly and the conditions to enter the idle feedback conditions area OK (plus it happens all over the rev range not just those that would mean it would drop into idle feedback with a 0% TPS signal)

Dimitri hinted in another thread that I have too much fuel on the main map, too much accel fuel, and that my igntion table is far too aggresive. I'm not sure about too much fuel though as I'm actually running a little lean if anything. Maybe it's the accel fuel that's causing me problems. I don't fully understand the mechanism the AEM uses for calculating exactly how much extra fuel to add when accelerating, it's fairly complexed, and I don't know how sensitive the engine is to changes in this value, so any suggestions on the magnitude of changes I should be making would be greatly appreciated.

 

Cheers

[Alex]

Mine (emanage/650's/stock FPR) will sometimes go lean at very low rpm if I just eek the throttle open a smidge. IMO this is down to a lack of resolution in use in the map in that area, to dial it out with more fuel.

 

I used to run 0, 3, and 5% TPS down low but 3-5 was nigh on the same so i've now changed the 3 to be 1% and this IMO has improved the low down pick up...but sometimes it still chuggs - creeping at low speed quite hard to map as it's a very fine line between too much and too little fuel. You're probably only a fraction out (like me), but some ECU's/piggybacks arn't accurate enough to make the ultimate adjustment.

[eyefi]

you would never be able to run the fuel map as is, but you can look at it and see how it's setup and you may be able to scale it and have a reasonable basemap.

 

is the bucking happening all over the rev range and load range? just on part throttle? do you have a log of it happening (usual parameters)?

 

are you using the base aem ignition map? if i remember correctly the timing on that map is quite mild (certainly compared to mine, which is quite aggressive)

 

can i have a look at your map?

[Guest Usmann A]

Tony, what does your TPS vs accel look table look like?

WHat sensitivity % is the the accel pump set at?

[TLicense]

Cheers for your inputs guys.

 

I've posted my map before, here

 

Unfortunately the car is not available at the moment to do any runs, and I don't think I've got any logs, as pretty much all of my logs are WOT, where this isn't a problem. The bucking, chugging or whatever you want to call it only really happens at low throttle positions, all over the rev range, but because it's low throttle it's only off boost that I've noticed it.

I'll see if I can post up a few screenshots of accel fuel template as it stands.

 

Cheers guys

[TLicense]

Here are the screen shots of accel fuel - throttle and accel fuel - load.

 

Any comments???

[Ian C]

Yeah, what do those graphs show Can you describe what the axis and line means, e.g. top left you have engine speed as x and a percentage as y, but %age of what? Current duty cycle? And how the graph interact with each other

 

-Ian

[TLicense]

This is where cut and paste from the AEM manual saves me a lot of typing

 

Tuning Throttle Accel

The operating principle is pretty standard. When the throttle is moved, the dTP value is

calculated. It gives a number proportional to the rate of change of the throttle. If this value

is above the user-specified threshold Accel dTPS Trigger option, then the acceleration

pump is enabled. But, since the TPS signal is usually noisy, the accel pump would be

triggering all the time. So we need to filter it before the threshold test is performed. The

filter specification can be set with the Accel TP Sensitivity option.

Once a dTP value is generated, the corresponding accel pump size is looked up from

the dTPS Accel table. This table gives a % accel pump size, versus the dTP value. This

% size is relative to the current injector pulsewidth (PW). So if the current PW is 1,400

uS (1.4mS) and the % value was 75%, the base accel pump size would be 75% *

1.4mS = 1.05mS.

Once a base accel pump size is generated, it is immediately multiplied by the Accel

Modifier table. This is a TPS based table and serves to scale the output based on the

throttle position when the accel pump was activated. This table usually starts at 100%

and decreases to 0% at high throttle value. This yields an accel pump value that varies

by throttle angle and is usually large for throttle movements near closed throttle and small

for throttle movements near WOT.

Next, it is multiplied by the TPS Accel Factor table, which is the RPM based correction

for the dTP component. This table usually starts at 100% and then decreases to a

smaller value (sometimes 0%) at RPM values. This makes sense because the fuel delay

is smaller at high port velocities; hence the accel pump can be smaller.

To recap what's happened, a filtered throttle position change has been detected and

from this value, a base % accel pump was determined. Then it was corrected for TPS

and RPM.

Now, it is checked against the user option Accel Limit. If it is larger than this value, then

it is reset to this value. This percentage is multiplied by the current injector PW, giving a

time in uS, and is applied as the starting value for the accelerator pump.

Once the pump is applied, the EMS decreases the pump size to zero, assuming there

are no more accel pump actions in the meantime. This is controlled with the AccelPump Sustain option. On a fixed time basis, the EMS comes back, and multiplies the

current value of the pump by the decay percentage, yielding the new, decayed pump.

Thus, a larger value makes the pump decay slower.

 

Tuning Load Accel

The dLoad pump works on exactly the same principle as the dTP pump.[/Quote]