When driving on the highway recently, under light load and away from the transition points for staged injection, the car seems to stutter a bit. This is reflected in the datalogs as looking like a not exactly noisy, but consistantly spikey signal. I can hear and feel it when driving as well, it seems like the engine is missing every other cycle. However, AFRs stay mostly around 15 (light cruise at about 3000 rpm), and as soon as i open the throttle more, it evens out and the car pulls nicely (altho i still have a hiccup when the secondaries come on). Im not sure what could be causing this. Im trying not to run the car too lean, but for cruise 15 should be good. I've attached my msq and a datalog of the commute home.

staged injection comes on at 105 kpa and 3800 rpm

Thanks

 

Hey Topless your running boost right?

 

Low amplitude tach noise is evident throughout that log. What hardware are you running again? You may want to try adding a load resistor across the VR leads.

There is also intermittent accel enrichment kicking in, even when TPS is constant. Try bumping up the TPS Accel threshold a bit to eliminate that issue.

 

Im using the stock CAS with a second LM circuit. MS1/V3. I noticed the tach noise, but I thought it was something else since i felt a vibration in synch with it, and the pressure was doing the same. It evened out when I hit the gas tho. Im not sure what you mean by a "load resistor" Do you just mean a high-resistance resistor, or a capacitor to smooth it out, or what?

I'll increase the TPS threshold, its at .4 v/s right now.

Yea, i'm running boost, but only up to about 6 lbs since im still on the stock S4 wastegate, altho I plan on turning it up to about 10 after I get the cold air box done and finish the FMIC.

 

I've added a cap across the second trigger (G signal) input to successfully get rid of noise so bad that I couldn't even get sync (no rpms).

 

how big of a cap?

 

.01 uF I believe.

 

i'll give that a shot. Did you attach it at the MS or at the sensor?

I was looking thru some of my older logs and the stuttering didnt seem to happen there, and didnt manifest itself in the pressure trace or physically in the way the car sounded and drove either.

 

I did it on the daughtercard.

 

Is the tach signal calculated from the G or NE sensor? If there is noise on that signal, wouldnt it make sense to add the cap across the one that generates the signal?

 

The tach signal is generated from a combination of the two, but noise on the G signal will often cause worse problems than noise on the Ne signal. Also the Ne signal has pots you can adjust inside the MS to help remove noise.

Also, you don't want to put a cap on the Ne signal wires as that will shift the signal from the CAS a bit, causing timing to change a lot more as RPMS change.

Ken