Why is my injector duty cycle decreasing?

[Quasimondo]

I went to the track last weekend to get some baseline runs. All mid 14's, which was to be expected, all I had was a full 3" exhaust, manifold and exhaust housing ported to 7cm, and a boost controller set at 10, because I creep up to 22 lbs.

After looking at my logs, there were a few things that bothered me that don't seem normal.

1. My o2 values dropped down to zero. I know that you really can't tell if your motor's running lean or rich from the stock o2 sensor, but my values were 1st gear .56; 2nd gear .64; 3rd gear .74, 4th gear .82. In 3rd and 4th gear, the values drop to 0 after 5500 rpms WOT. Coasting back to the pits they were fine, let it idle for 5 minutes to cool down, they were normal. It happend with all three runs.

2. My injector duty cycle never went above 85%. Normally, I would consider this a good thing if I didn't have boost creep, but in 2nd gear, it leveled off at 85%, and in 3rd and 4th gear, it went down after 5500. It never dropped below 75%, but still, I figure with the amount of boost I'm running, it should've been higher.

I'm not using a SAFC and I'm still on an unhacked 1G MAS, (I never hit fuel cut, but I forgot to log MAFS readings) and I didn't get any CEL's. I was just running to get a baseline to see where I'm at before I do any serious modding, and the logs just didn't seem right.

Comments?

 

[BrokenTsi]

you're bone stock, dont worry about it, just drive. but you shouldn't be creeping 22lbs. Fix that problem first. You should be able to hold a steady 15psi = high 13's.

 

[BrokenTsi]

also, injector duty cycle varies upon rpm. As long as you're not maxing them out, you're ok. There is a chart on taboo's site about IPW and IDC. If you're having a problem with creep, try this...... you probably have your boost controller hooked up from the J-pipe and the wastegate actuator. Run a T from the "bov to intake manifold" hose. Its a much better boost vacuum source IMO.

I'm a ninja.

 

[CanadianTSi]

Sounds like your O2 sensor is bad, it shouldn't drop to 0 like that. That is probably why your DC stayed at 85 percent. Replace your O2 and fix your creep

 

[anconover]

set at 10psi, but creep to 22psi? Time to fix whatever ridiculou problem you have, like a welded shit wastegate . Thats far from normal.

 

[Quasimondo]

Yah, I know. I'm replacing the WG actuator and putting on a ported 2G this weekend. The arm barely moved when I put any pressure to it from my compressor. If all works good, I'm going to try to get one more track run in before they close for the season, see if i can improve my et's without having the knock monster kill all of my fun, or my engine.