How does altering the afm signal using piggybacks affects the ecu timing?

Q

queenskid926

Tires yeling @ every Lite
Jul 27, 2007
1,112
0
0
35
New York City
www.myspace.com
Im not sure if this should be posted in piggyback or the ecu section so sorry in advance mods if it has to be moved.

I've read that when using for example an safc, where it allows you to tune the amount of fuel by altering the maf signal to the ecu, that when you alter the signal, the ecu adjust its timing based on the input that its receiving.

Knowing this, How is the timing affected if say I'm adding fuel with the safc or when I'm taking fuel out from the afc.

Is it better to use an adjustable fuel pressure regulator to add too much fuel and fine tune it to take fuel out?

or to add fuel pressure just under what is needed and fine tune it to add fuel where need to be?

Either way i think its best to not have anything dratic like 30% gain or loss on the safc right?
 
pln

pln

Get the gate!
Apr 10, 2007
107
0
0
eskilstuna.SWEDEN
I am not sure exactly what the oem ecu does when maf signal is manipulated, but it doesnt compensate correctley and at 1.4bar timing distroyes many 7mgte engines with piggybacks.. even with enough feul etc.
I was carefull not to go over 1.3bar and I started with rich a/f and cut more and more until i reached good numbers. I would recommend adjustable linjear fuelpressure regulator with piggy.
 
3p141592654

3p141592654

90T
Oct 11, 2005
3,815
13
38
Thousand Oaks, CA
Its complicated, there are many inputs to the ignition timing equation including a knock sensor. At a very basic level, the MAF is used to compute engine load, actually volumetric efficiency is what it calculates, but that is called the "load".

The Lexus/550 mod (or piggyback/550) makes the ECU think that the engine is running under a lower load than it really is, and so it runs the timing more advanced than it would with the correct inputs. That pushes you closer to detonation, although the knock sensor is there to back it off. The problem is how fast the KS can react to catch a problem. Based on people's experience, it is not fast enough under very high load.
 
supranasty

supranasty

Yo Daddy
Apr 12, 2005
374
0
0
jamaica ny
3p141592654;1485341 said:
Its complicated, there are many inputs to the ignition timing equation including a knock sensor. At a very basic level, the MAF is used to compute engine load, actually volumetric efficiency is what it calculates, but that is called the "load".

The Lexus/550 mod (or piggyback/550) makes the ECU think that the engine is running under a lower load than it really is, and so it runs the timing more advanced than it would with the correct inputs. That pushes you closer to detonation, although the knock sensor is there to back it off. The problem is how fast the KS can react to catch a problem. Based on people's experience, it is not fast enough under very high load.
Click to expand...

Is that what the Apexi ITC is for ? To correct timming at a given rpm.
 
JimR

JimR

Supramania Contributor
Mar 30, 2005
304
0
0
Canada
Yes you can, however that will make your power and fuel economy suffer under low and medium load... the vast majority of your driving. It works well in a pinch though.

The next step is to look at a more advanced piggyback system (the maftpro, for example) which will let you control timing as well.

I retard the timing between 3 to 5 degrees under high load / high rpm conditions.

When you're tuning, try to keep close to the fuel cut threshold by tuning richer. That will give you the safest operation because the ecu will 'see' close to full load when you're at WOT, and retard the timing appropriately. The leaner you go, the more timing advance the ecu will give, because it 'sees' less airflow, and thinks the load is less.
 
Q

queenskid926

Tires yeling @ every Lite
Jul 27, 2007
1,112
0
0
35
New York City
www.myspace.com
IJ.;1488230 said:
Time for a Standalone QK... ;)
Click to expand...

I know lol,
I'm actually been looking at Aem and the Wolf ems. I would really like to finish the body work before I spend the money on a standalone though. I just want a nice steady clean 375-400hp for right now on a conservative tune.
 
I

IJ.

Grumpy Old Man
Mar 30, 2005
38,728
0
0
61
I come from a land down under
queenskid926;1488314 said:
I know lol,
I'm actually been looking at Aem and the Wolf ems. I would really like to finish the body work before I spend the money on a standalone though. I just want a nice steady clean 375-400hp for right now on a conservative tune.
Click to expand...

Out of the 2 I'd go AEM....
(ex Wolf user here)
 
sk6471

sk6471

Quietly Lurking
May 28, 2005
91
0
0
Texas
queenskid926;1485570 said:
so being that the ecu is going to run the timing more advanced, cant a person compensate that by retarding the base timing? bump it from 10* down to 9*? or even 8*?
Click to expand...

If you retard the timing by turning the CPS, it not only retards the timing across the board even when you don't want it to, but it retards when the fuel injectors fire. Also moving the base timing 2 degrees won't help your problem if the ECU is advancing the timing 10 degrees because it doesn't think the engine is under load.

There are other reasons why you need to control the timing as well. If you are using a slower spooling turbo, Your engine won't be under as much load at lower rpms and could use more advance to not feel so sluggish. And on the other end of the tach, if Toyota advanced the timing above 6000 rpm to compensate for the poor flow of the CT26 at that range you might need to remove a lot of advance.

You should look at the timing control function on the MAFTPro. There isn't much about it on SM, but it's the only piggyback unit that I've heard of with any ignition control.
 
supranasty

supranasty

Yo Daddy
Apr 12, 2005
374
0
0
jamaica ny
sk6471;1489272 said:
If you retard the timing by turning the CPS, it not only retards the timing across the board even when you don't want it to, but it retards when the fuel injectors fire. Also moving the base timing 2 degrees won't help your problem if the ECU is advancing the timing 10 degrees because it doesn't think the engine is under load.

There are other reasons why you need to control the timing as well. If you are using a slower spooling turbo, Your engine won't be under as much load at lower rpms and could use more advance to not feel so sluggish. And on the other end of the tach, if Toyota advanced the timing above 6000 rpm to compensate for the poor flow of the CT26 at that range you might need to remove a lot of advance.

You should look at the timing control function on the MAFTPro. There isn't much about it on SM, but it's the only piggyback unit that I've heard of with any ignition control.
Click to expand...

Apexi ITC Piggyback
 
You must log in or register to reply here.
Top Bottom