The ECU doesn't appear to give you any feedback about knock at all. This is my current area of research, so hopefully we'll have some answers soon. Front steering angle, yaw sensor are both viewable through the ABS computer on our 350Z but you have to have VDC (stability control) for these sensors to be present. I haven't seen any mention of an accelerometer but there is a side-G sensor.

 

I've been doing some datalogging on the dyno over the last few days, and wideband sensor 1 is ALWAYS significantly lower than wideband sensor 2, up to about a 1.0 difference in air/fuel ratio. Is everybody else seeing this? This seems a bit odd to me that they'd lean out one bank like that.

 

I agree. Are you sure measurement error isn't part of it? 1.0 is a lot...

Can you datalog injector duty cycle on each cylinder to see if there is a coorelation to the A/F? This would help indicate what is going on.

The good news is that if this is true, more power can be made by fixing it.

 

UpRev hasn't posted back here on the subject, so I can only assume that their data coming from the sensors is correct...

Good idea on the injector cycles, I'll check that next time I head out. The interesting thing is that the AFRs are basically identical all the time except at WOT. And the injector cycles could turn out to be the same while one bank gets a higher air massflow than the other.

 

The only way to get that much of a difference in air mass flow rate is if there was asymetric intake valve cam timing for the different banks.

This could be another item to measure... Duty cycle of the cam actuators... They are also PWM controled.

I can see this turning into a real research project. But at least it would be good to know.

 

Interestingly enough, during my dyno run (on a Mustang dyno) I logged most everything. I logged the cam timings, not the actuator modulation, but I assume they are decently correlated. As you can see, they are pretty dead on, but the wideband offset is still there:

 

Awesome job on the data logging! I love it. Its rare to see.
I always say, when doing any test, you may as well aquire all the data possible.

Now that the above data shows valve cam timing to be the same for each bank, it doesn't seem likely there would be that much of a difference in bank to bank air mass flow rate.

I know from testing, the plenum runner pressure drops arent all that much different from bank to bank. And I would assume the valve port diameters and pressure drops are generally the same for each bank. Although it can't be ruled out, it would be hard to imagine that much difference in air mass flow rate difference would exist for similar geometries.

Differences in injector duty cycle could easily cause the difference, but why would Nissan do this?... I don't know. Testing could show what is going on there.

If the difference was attributable to measurement error of the sensors, that would make for a easy explanation.

Can you switch your A/F sensors to their opposite sides and do a couple of WOT runs on the road and see if you get the same results? You don't even need to put it on the dyno, but this would help show one way or another if the differences are sensor related.

 

I love data. Basically we should all just compare MAF curves versus RPM as an indicator of potential power (aside from tuning). For example, you could post before and after MAF curves for your MREV or plenum spacers. :P Or I could do this for you.

Regarding the bank variance, well the other possibility I can think of is if there is some mechanical issue, like bad ring or valve seals changing the amount of air burned in one bank.

What would be the point of separate injection cycles for each bank (given a single MAF sensor) if it wasn't doing closed-loop control of the AFR for each independently? So basically if there is a mechanical issue causing different airflows, I should see it in a difference between long term fuel trims for each bank.

Regarding switching sensors, do you mean litterally plugging one sensor harness in to the other? I haven't looked but I wouldn't assume they would reach.

 

I have A/F data for many spacers and MREV's but for the most part, it doesn't change the A/F all that much. Its not untill many mods are stacked up that it begins to make a significant difference.

Bad rings could leak air on the compression phase, but it would also leak fuel vapor by the same leak path. Hence it would maintain the same A/F ratio. But even if it didn't, it would also cause a big loss of HP that would probably be noticable on the dyno.
For a leak that bad, I would expect to see a big loss of power.

Come to think of it... since the ECU trims each bank independantly, it may be triming it like that intentionally because of calibration differences in the stock A/F sensors...

Not switching harnesses. Unscrew the wideband sensor from bank one and put it into bank two. Take the sensor from bank two and put it into bank one. Then plug your harnesses back in like normal.
If the calibration of the sensors is good. It should measure exactly the same.

If it doesn't... well... we would need to look at the data and think about what is different, where it is different and the magnitude of change. The data could suggest a range of different things.

 

I was suggesting logging MAF sensor data before and after the spacers and MREVs, not AFR data. To make more power they need to bring in some additional airflow, so this should show up directly in MAF sensor logs on the street.

 

Oh... OK. I assumed it was related to the Bank 1 & 2 A/F issue.

I suppose it could be done, but the difference would be on the order of 5% for a spacer.

 

I did a quick WOT log in 3rd gear and here are the results for wideband and injector pulses:





So the injector pulses are the same... the plot thickens. So either there is a flow issue where one bank is seeing more air than the other, or the sensors output different voltages only at WOT. At ALL other times besides WOT the widebands read virtually identically... Hmmmm...

 

I was hoping to have time today to switch WB and have dyno done with 17 degrees - but didn’t, perhaps next Saturday. Below is short street pull I made tonight.

 

Wow, according to your wideband voltages you're in the low 14s to mid 13s at WOT! That's quite a difference from my car. Interestingly enough you have similar injection times (maybe 1 ms less) and very similar MAF rates.

 

Oh Thank God that smart people are looking into ways to squeeze out a few more hp in my G. Tony, when you have figured it out, please put the upgrade on the market. My 1/2 spacer has been fantastic and I'm ready for another under the radar performance upgrade!