Roll-On throttle Leaning Out - Matt Kramer?

[cygnusx1]

I have the car running really well. The timing and the mixtures are all in the safe zone and it has no burps or surges anywhere in the driving range.

 

I have one issue and I don't quite understand it. I will try to datalog it this weekend but for now I will explain.

 

I have the AE set as close to perfect as I can get. It's really pretty good. The problem is only when I SLOWLY roll the throttle on at a STEADY rate. Example would be going from off throttle to 1/2 throttle in about 4 or 5 seconds. A really slow throttle roll on, as in getting back on the gas while approaching and rounding an apex. When I first tip-in the pedal, the AE gives me a nice AFR but after that wears off, the mixture leans out to 14-15 during the steady roll motion of the pedal. The mixture settles back to normal when I stop the pedal movement. This happens at all RPM's and loads.

 

A steady pedal motion, produces little or no "Kpa/sec" so the AE goes away for the duration of the pedal movement.

 

I use 100% MAP blend on the AE and it works well.

 

Are there any functions for steady state pedal movement enrichment? What would cause this leaning out? Could it be lag factor in the MAP reading set too low?

 

Thanks,

Dave

[Matt Cramer]

If the problem's not happening with MAP based AE, I'd stick to that.

 

If it is, could you please post a data log and MSQ?

[cygnusx1]

Matt, I run 100% MAP and it does this. I will datalog it tonight and post both the current msq and log file.

 

Thanks.

[cygnusx1]

MSII, v2.687, 3bar sensor, WB O2, GM IAT, Nissan CHT

 

It runs pretty steady AFR's until I wave the throttle around a bit. There are a few very lean spikes in the datalogs that could be misfires? I couldn't really duplicate the lean on throttle climb very clearly but if you look closely you will see alot of 14:1's during some throttle roll on's. If you have time to take a look and comment it would be appreciated. The factory fuel pressure regulator is connected to a 3 foot vacuum line and may be lagging. The fuel rail is dead headed.

 

Return Line down through the regulator.

Fuel supply up the filter and to the rail.

 

 

 

 

Thanks,

Dave

datalog.zip

v2_687 msq.zip

[Matt Cramer]

Dave,

 

I saw a few bits of tach noise in the data log, but most of what I saw looked like it could be cured with some careful tuning of the acceleration enrichments. You've got a good clean TPS signal, so you might want to blend in some TPSDot.

 

I saw the lean spikes, too - it's hard to tell if they are from too little acceleration enrichment, or so much that it caused a misfire.

[cygnusx1]

Matt I will look into the tach noise. Maybe I will add another metal brade over the wires involved. I didn't even notice the noise. I will play some more with the AE settings to observe how the datalogs react to more and less. I can also try blending in some equivalent TPS signal as you said. TPS is something I haven't really spent much time with yet.

 

Thanks your help is much appreciated!

 

-Dave

[datman]

Dave have you tried using X-Tau? to sort the lean spikes? I have the same probelm and no matter what I ste the AE for I still get a lean spot as I step on the gas, I've read XTau can help so I'm going to spend a few hours on it today.

[datman]

I've tried lots of different settings but can't stop this lean spike...any ideas guys?

The problem seems to be when I accelerate in 3rd or 4th it starts to pink, if i push the pedal all the way to the floor it goes past the lean spot and richens up.

should I just keep raising my VE numbers until it stops?

[cygnusx1]

Dave,

 

I saw a few bits of tach noise in the data log, but most of what I saw looked like it could be cured with some careful tuning of the acceleration enrichments. You've got a good clean TPS signal, so you might want to blend in some TPSDot.

 

I saw the lean spikes, too - it's hard to tell if they are from too little acceleration enrichment, or so much that it caused a misfire.

 

 

This is an older thread but I never felt the results of the tach noise that Matt saw, until this weekend. I put about 100 miles on the Z this weekend and a couple times I experienced a sudden, split second, drop of power. It felt like the engine turned off while cruising around 3000rpms. I happened to catch, out of the corner of my eye, the tach needle bouncing around for a split second. I was not datalogging but I suspect this is what Matt saw in my datalog. I am going to look back through the log and see if I can find it.

 

What can be done to improve/reduce noise on the tach signal? Is it all about wire shielding?

 

This is how I wired it:

http://www.diyautotune.com/tech_articles/how_to_megasquirt_your_280zx_turbo.htm

 

 

 

My lean spikes were pretty much fixed with more careful tuning.

[datman]

I

[datman]

I had noise from my single wire temp sensor....I'm running a fixed resistor in the relay board at the moment until I get a 2 wire sensor. I also had noise from the electric fan into the crank sensor....when the fan was running with the engine off but ignition on the fuel pump would start running! took me ages to figure that one out.