Question for the tuners on FI and Dyno - .: XT660.com

Skunkmoto · # 1 12-08-10, 12:42

Ok lets ignore most of the other stuff in a FI system and the million and one things that determine engine performance/efficiency.

In very simple terms, you have fuel and air going in, a bang, and gases going out.

The bikes ECU will have a stock fuelling BASE map that is fixed and determines how much fuel gets squirted in (multiplied by correcting factors, depending on information from the various sensors, and too many variables to mention here).

The O2 sensor in the exhaust, this gives feedback to the ECU to allow for some on the fly adjustment of the fuel going in eg for a given set of constant conditions the ECU gives X amount of fuel, but the O2 sez you need more/less than X depending on the real time O2 reading?

So in a stock XTZ while the bike is running, the FI system will constantly be tuning itself within some small tolerance to an optimum O2 reading?

When on the dyno what to you tuners use as the base for tweaking the fueling is it the AF ratio?

richardsracingmad · # 2 12-08-10, 13:10

I see Kevs online...but, being a forum I'll say may thoughts....

From what I understand, the Dyno take a reading of your AF Ratio, then adjust it to the optimum setting. (providing their AF meter is accurate, of course)

They adjust the AF by changing the fuelling.

Kev · # 3 12-08-10, 13:22

[quote=Skunkmoto;135524]Ok lets ignore most of the other stuff in a FI system and the million and one things that determine engine performance/efficiency.

In very simple terms, you have fuel and air going in, a bang, and gases going out.

The bikes ECU will have a stock fuelling BASE map that is fixed and determines how much fuel gets squirted in (multiplied by correcting factors, depending on information from the various sensors, and too many variables to mention here).

The O2 sensor in the exhaust, this gives feedback to the ECU to allow for some on the fly adjustment of the fuel going in eg for a given set of constant conditions the ECU gives X amount of fuel, but the O2 sez you need more/less than X depending on the real time O2 reading?

So in a stock XTZ while the bike is running, the FI system will constantly be tuning itself within some small tolerance to an optimum O2 reading? Not quite correct the O2 sensor tunes for 14.7:1 which is for emission control not the XT's optimum A/F ratio of around 13.2:1.

When on the dyno what to you tuners use as the base for tweaking the fueling is it the AF ratio. The tuner should be tuning for the best Hp & Torque across the whole rev range, the A/F ratio is a guide line to what the motor is doing. It is a well know fact that 99% of motors run best between 12.5:1 to 13.5:1.

richardsracingmad · # 4 12-08-10, 13:35

Kev, is it possible for them to optimally tune it if they have NO AF RATIOS?

richardsracingmad · # 5 13-08-10, 05:21

Well, this is sounding very similar to our earlier discussions, but still belongs on here as......

The Dyno may not tune your bike for best performance and torque, if the AF Ratios look too far out.

When I had a dyno, the best HP figure was when I brought it in, but as the AF Ratio looked too far out, they tuned it to 1.2hp less than I had.

Kev · # 6 13-08-10, 09:05

Quote:

Originally Posted by richardsracingmad

Well, this is sounding very similar to our earlier discussions, but still belongs on here as......

The Dyno may not tune your bike for best performance and torque, if the AF Ratios look too far out.

When I had a dyno, the best HP figure was when I brought it in, but as the AF Ratio looked too far out, they tuned it to 1.2hp less than I had.

If the dyno equipment is working correctly it all comes down to the tuners input to how the motor is tuned.

Freez · # 7 28-08-10, 09:32

Guys, I am going to "argue" the opposite point of view

There is no way on earth that a tuner can take a FI bike and tune it correctly without air fuel ratio meters.

with dyno tuning there is only one thing that is important. Air Fuel ratio.

Once you hit the perfect ratio, HP and torque will automatically be at maximum. There is no such thing as tuning for most HP and torque. HP and torque is a direct result form a perfect combustion and that is directly related to the best possible A/F ratio.

Here is the biggest problem with guys in South Africa and maybe elsewhere in the world. The guys use a standalone lambda sensor, attached to a thick pipe that they hang behind the exhaust. The O2 sensor is in direct contact with fresh air, so the A/F reading they get is bogus (showing way leaner than what the motor actually burns). So they refer to manual tuning, and just simply ignore the A/F ratio because if they tune for 13:1, with stray O2 at the sensor, the bike runs very badly, as they normally over-fuel the bike.

If you have the correct equipment, A/F ratio is critical, and once tuned, the ratio is constant for all throttle inputs and RPM ranges. That's what you want.

Another problem guys have in SA is that the Powercommanders are way to complicated for them to tune by hand, especially without an A/F ratio. Their dyno also have no load control, so they also cannot tune partial throttle inputs. They sell TFI units to clients. TFI have no throttle input, so it is only good for full throttle and it has 4 screws to set. Easy to tune if you have 4 screws to turn, and you can do a few runs to see which setting is best, without A/F ratio. 99% of the other throttle settings are ignored and is guaranteed to be out. They give you a full throttle dyno run, riders think they got a great deal and end up with a badly tuned bike for normal riding.

There are only one ways to tune a FI bike correctly and that is:

Use a powercommander with a dynojet dyno equipped with Tuninglink software.
2. Buy a PC or simmelar device with an Auto tuner on it. (note this can also be a problematic device if not installed correctly)

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