Question about compression and AFR

[mazikowski]

My CA is running, and running fairly strongly at that. I did a compression check and it did worry me slightly to see all cylinders running between 105-115. This just seems a bit low to me. Is that an "acceptable range" or is that nearing a dangerous low? Like I said, the engine runs fine (nice and strong) as far as power and response are concerned.

Now to the AFR question. The AFR (theoretical according to my APEXi Pen TT reading narrow band O2 voltage) hovers in the mid-14s most of the time unless I do really hard acceleration. Under hard accel, it will drop as low as 11.5 or so. Well, running mid-14s at 3500-5400rpm seems a bit lean to me. Is there something wrong with this? Also, when I decelerate quickly and drop it to 0% thorttle, it will lean out really bad. I'm talking so lean that the AFR reading flashes 20.0 (it doesn't read higher than that) and unless I drop it into neutral it will backfire like an M-80. I'm thinking some of this could have to do with a pinhole boost leak I have in my hotpipe and/or the fact that my exhaust ends with the S13 O2 housing (or whatever you call that pipe that bolts directly to the turbo and the O2 sensor screws into)... It's FWD by the way, so that pipe is angled slightly forward =/

[r34 gtr]

Thats exactly what it should be doing. Near stoich unless you put your foot into it and then it goes nice and rich. When you let off it cuts fuel, just like it should, and since its all air going in and no fuel you are of course going to read full lean. Your car is running exactly like it should, don't worry man.

Compression is a bit low, but it all seems to be in good shape. No big fluctuations between cylinders, so even though its low its still definitely usable.

backfiring is normal especially when you have all of 3 inches of exhaust.

[bentvalves]

do compression test when the engine is nice and hot.

[float_6969]

Compression test needs to be done on a hot engine, with the throttle fully opened, and fuel pump disabled.

If you did it that way, those numbers are kinda low.

The AFR's are behaving exactly as they should.

[bentvalves]

I like disabling the pump and CAS so injectors dont get a signal.