Back from the dyno and disappointed

[Billy Mild]

My secondary vacuum doesn't run very when the isn't running. Once a minute or so.

My top end is stock. No porting of any kind. I would be shocked if the cam timing has been changed. Records that came with the car made no reference to that. If my secondaries weren't opening all the way is there a way to check that without pulling the plenum?

Sent from my Nexus 6 using ZR-1 Net Registry mobile app

[RussMcB]

Somewhere I read you can observe the servos opening without removing the plenum by just peering down into the valley while tricking the system into opening.

It is sort of implied at the end of this article:

http://www.zr1specialist.com/HAT%20W...5%20Engine.pdf

[XfireZ51]

As an FYI, cam phasing will change due to slippage of the sprocket and chain stretch over time.

[bdw18_123]

Originally Posted by XfireZ51

As an FYI, cam phasing will change due to slippage of the sprocket and chain stretch over time.

And, according to Marc, the factory method of setting the timing is "subject to variation". According to his timing article, his '93 LT5 was found to have the left exhaust cam set 4 degrees out of phase with the others. So cam timing is definitely something worth checking, though it is far from an easy process.

http://www.zr1specialist.com/HAT%20W...t%20Timing.pdf

[We Gone]

Originally Posted by RussMcB

Somewhere I read you can observe the servos opening without removing the plenum by just peering down into the valley while tricking the system into opening.

It is sort of implied at the end of this article:

http://www.zr1specialist.com/HAT%20W...5%20Engine.pdf

The how to is in Dynomites sticky. You can also do this with a flashlght. he has so much information I could not find the exact link.

http://www.zr1.net/forum/showthread.php?p=187361

[mike100]

My car also ran 13.1 AFR with a cat-back and a chip as measured at the muffler with the external wideband.

These cars run rich and don't need much fueling change to accommodate the usual bolt-on's...why is yours so rich?? I would still check fundamentals like the fule and spark, but also the possibility that the intake duct is collapsing limiting you to 5500 rpm pulls and cutting off the air part of the air-fuel ratio. Either that or you got a bad muffler or something very unconventional happening.

[Billy Mild]

I did a little test drive today around town. The car seems to run pretty well overall.

Marc told me to perform a test to see if the car is misfiring at all. Do a WOT pull from 40 MPH in 4th gear. It should pull cleanly without any hesitations or issues. When I did this in Open loop before the car was fully warmed up I did notice a bit of a hiccup right at the beginning, but it overcame that.

When I did the same test fully warmed up the car pulled without issue. Even when the car is warmed up I heard a bit of gurgle coming from the exhaust when decelerating. I'm curious if that points to anything or if these cars should sound like that.

On my scanner I saw the BLM at 133-136 when at idle, but it was 126-129 while driving. I didn't get to see what it said when at WOT. I need to get a datalogger or at least TunerPro with a ALDL adapter.

[Hog]

WOT info doesn't mean much from the narrowband O2 sensors as it will read rich. For accuracy the wideband is needed.

It would have been nice to be able to compare some 1/4 mile speeds as compared to mods.