Silo

iTrader: (1)

Hello guys,

as we have noticed on various dyno runs with OBD scanner connected the ECU controlls the throttle by it's own means, and we never ever got a 100% open throttle through any run. Throttle opening is always sloping down to 85% towards the end of each run.

Anyone know if this can be altered with any of the available piggy backs (EU, UTEC etc).

Thanks!

Old School

iTrader: (28)

really? I didn't know that....interested in the answer.

Sharif@Forged

iTrader: (92)

85% is WOT on most scanners...its about 4.7-4.8V. I have never seen the slope that you mentioned. But I do see 85% on some of my scanners. I can assure you the throttle plate is completely open. Take your intake tube off, and put the key in the on position, and you can see it for yourself.

Silo

iTrader: (1)

Sharif, that's a good idea but I guess that there is a difference if you do this without the engine running, at light load or at high load. However, it will help determine if the OBD scanner will show 100% at horizontal throttle position or not and this in return will either confirm my theory or yours.

Silo

iTrader: (1)

Here is a dyno graph showing the slope in throttle position although the accelerator was fully depressed:

Sharif@Forged

iTrader: (92)

Thats a good point. However, if the throttle plate is 100% open with the engine not running, at 85% TPS signal, I would think that a steady 85% under load would also mean it is open.

Maybe different spec vehicles are controlling the throttle differently?? You'd think those German spec vehicles would be even better than the USA spec.

Silo

iTrader: (1)

BTW, I actualy think that there are two signals but maybe someone with a Cypher unit can confirm this. One would be the accelerator pedal position the other the actual throttle position. I am positive that the signal we scanned is the actual throttle position as the accelerator was floored as usual on dyno runs.

I don't think that the german spec Z's are better, in fact they are rated 7hp lower than the US spec cars. But both have the speed limiter at 250 kph (156 mph) which is controlled by actual throttle position and as you can see on the dyno the slope stabilizes as speed is approaching 250 kph.

The car dynoed is our STILLEN supercharged project car. One could think that if my above assumption is correct why does the slope sink so quickly, but this could be due to the fast raising speed. The ECU is probably smart enough to recognize how fast the car is accelarating and adjust the throttle position accordingly for a soft speed limiter approach.

dovla

Actualy there are 4 signals: Pedal Position 1, 2 and Throttle Position 1,2

Zoom in Throttle 1 vs Pedal 1


Zoom in AFR


Zoom in Cams & Timing

Silo

iTrader: (1)

Thank you for confirming... OK, this tells us something but not everything.

a. the two voltage curves are parallel meaning that the input was translated in a 1:1 throttle behaviour (but under what load conditions was this recorded?)

b. the throttle voltage is 0.3V below the pedal voltage, both do not reach full 5V for some reason (does it mean the throttle is not fully opened = horizontal position? and is this a M/T or A/T?)

dovla

It is MT. Data for above chart was logged during my most recent Dyno, unfortunately I didn’t log Calculated Load but I am guessing it was ~90% (+/- 2%). Below chart was logged few moths ago during previous Dyno session.




Silo you are correct, in my case throttle voltage went up to 4.2 V so I guess it was not fully opened.

Silo

iTrader: (1)

Thank you again for the additional info!

So we can resume that the throttle doesn't open up all the way in both cases. However, our car shows a different behaviour than yours - your throttle position seems stable through out the run and our slopes down.

We still do not know what throttle voltage corresponds to what throttle angle (or percentage) since you only have the voltages logged and we only have a percentage logged. We need a way to correlate the two values to each other.

Sharif@Forged

iTrader: (92)

Good information for everyone. The 4.7V-4.8V max is the reason that many scanners show 85-90% TPS....since they assume a standard 0-5V signal.

With respect to Silo, I am not sure why your signal is slopping downward. On my personal car, and many of the cars we tune, we have eliminated the speed cut. Maybe you are correct, in that the ECU gradually begins to close the throttle in the higher gears, in anticipation of hitting the speed cut.

dovla

Disclaimer: Opinion and info in my posts are with best intentions of G35 enthusiast and amateur without tuning experience.

There might be a reason why would ECU slop TPS downward.

Silo, can you tell us more about your STILLEN supercharged project car? BTW, you posted very nice chart. What does AFR look like? Injectors: size, pulse, duty?

SIRCRASHALOT

The Technosquare ECU flash also changes the electronic throttle control setting.
Even if you push the gas pedal to floor, it doesn't mean your throttle is opening 100%.



http://www.technosquareinc.com/Nissanintro.htm

dovla

Could be, but I still have speed limit and on all of my charts, speed reaches either 105 mi or 135 mi (+/- 5mi), dynoed in 4th or in 5th gear while Silo’s graph have TPS slope at the beginning of graph from 50 to 150 km/h (30 to 90 mi/h).

Silo

iTrader: (1)

Yeah, the slope is realy starting early and if there was not an intentional difference in the throttle controll of Euro spec cars dovla's log should show at least a similar behaviour.

Unfortunately we had not recorded A/F ratios on that occasion. The engine is completely stock, stock injectors too. The STILLEN kit has an additional injector integrated into its inlet. It's controlled by a black box that also alters ignition under boost (probably a SplitSecond unit).

dovla

I think "black box" is your answer. They probably didn’t want to risk running lean.

Silo

iTrader: (1)

Yeah, it appears old fashioned to use an additinal injector upstream but with the returnless fuel system of the Z it is a good alternative and allows a better A/F tune compared to other solutions (e.g. secondary inline fuel pump and voltage controller to raise the fuel pressure).

But what you mean that this is my answer? What was the question?