So I went out last night to do some base 3rd gear pulls and datalog the results with my new system. I have a weird issue that I don't recall ever seeing(or maybe just not noticing). At 4k the motor bogs and just sits there for a second. Every time with out fail. Looking at the logs later it actually would hit 4k then back down to 3.9k then go foward from there. Ignition was not being pulled and I can't figure this out for the life of me. Also I would like some advice on where to proceded on how to tune. I ran really rich up top, 5500-6500, other than that I was pretty good I thought. Also how much further can I advance my timing for realistic for power gains. Also the timing would swing up and down so I don't know if the cars being conservaticve or if it has to do with any variable parts, ie..vias, cvtc, etc..

Thanks for the help as always.

 

Can we get some background on what the car has done to it?

 

Just has an Intake and downpipe. Will shortly be putting a Catback on.

 

What are you tuning with? How is it setup?

 

I am not tuning yet, first I'm gathering info. I do have a utec standing by but want to by as informed as possible before I play with it.

 

As posted in your thread on the .Org, that dip in intake cam angle at 3800 rpms is normal for cars with a dual stage IM, at least from the few datalogs we've seen.

 

Well the dip being normal is good, I'm more concerned with the bog at 4k though.

 

I would like to see some logs with MAF voltage in them and with timing.

Everything in those graphs looks good.

 

MT or AT?

 

It's an auto, I'm going out tonight and will log AFR, IGN, TPS, IPW, IAT, MAF.

 

Here's tonights runs, same issue. Motor bogs at 4k then continues. I'm lost.

 

The first thing I notice is that the MAF voltage is dropping where you are stumbling. Something is causing less air to get to the motor. I would suspect it might have something to do with the VVT of the motor. Your throttle is staying open (according to the log) so the valves in the motor are the only thing that I can think of that would restrict air flow.

 

The power valve is supposed to open around 3800. I wonder if this is from it activiating and changing the air flow geometry. I don't see why the motor would stumble from this but speed does climb constantly still.

 

The power valve? Can you elaborate on this?

 

He has the FWD dual stage IM... or variable intake, if you're familiar with the Nissan terminology. There is a power valve in the intake manifold that is shut from 1800-3600 rpms to increase runner length for more low end torque, then it opens past 3600 to shorten the runners.

 

Exactly, the disturbance happens right after the valve is supposed to open so it would correlate very well with KPiersons' theory that the airflow is changing. I don't understand why this would cause the motor to stumble though.

 

I've never heard of this stuff!!!

Disconnect that solenoid valve and make a few runs. That will be the easiest way to eliminate it from being a suspect.

With airflow mods the engage point of the solenoid may need to be changed.

 

Oh, and its not KPierson's 'theory' that airflow is changing, your MAF shows that it changes!!!!

 

I don't remember seeing this intake manifold valve when I put my spacer in. I have an 04 auto. Where is it? Do you mean the EVAP canister purge volume control solenoid valve? I thought that was for crankcase oil vapor recirculation (just like the one up front)... I don't see how it would shorten runner length either.

 

I don't think our '04s have this!