Is this normal with an A/T?

toojung2die · 06-13-2005, 10:26 AM

I've begun logging my engine with stock fuel management so I have a good idea of how things look when everything is "normal". My profile lists my current mods and boost is mild ~12-13 psi. I fixed a lot of boost leaks I found in the intake manifold area; injector seals, T-body gaskets, T-body shaft seals, hoses etc. I currently have no leaks. I installed new 3g lifters. What a difference, my idle has never been this smooth. It sits at 740 rpm and doesn't waver at all. The best gas I can get around here is 91 octane.

Here's the problem. My timing drops to 0 degrees for a split second every time my trans shifts into the next gear and then jumps back up. This inverted spike happens at the moment the gear engages. I have no trans mods and shifts feel smooth.

I don't have any good WOT logs saved but this one should serve as an example. It's just a normal take off from first to third, not accelerating hard at all:

RPM Timing TPS O2
908 9 7.07 0.1
1848 10 38.9 0.92
2144 21 57.76 0.08
2240 21 70.33 0.92
2420 20 70.33 0.92
2636 20 69.16 0.92
2904 17 55.8 0.92
3292 15 51.08 0.82
3792 12 42.04 0.96
4268 13 40.47 0.96
4708 13 39.69 0.96
3680 15 39.29 0.96
3468 0 39.29 0.98
3660 10 39.29 0.96
3844 10 39.29 0.96
4048 11 39.29 0.96
4204 13 39.29 0.96
4280 14 39.29 0.96
3380 0 39.29 0.98
3432 11 39.29 0.96
3516 11 39.29 0.96
3508 11 37.33 0.98
3364 23 20.04 0.86
3052 29 9.43 0.86
2816 34 1.18 0.94
2424 34 1.18 0

I want to get this running right before I start messing with bigger injectors and tuning.
Thanks

doug · 06-13-2005, 02:58 PM

Timing drop between shifts is completely normal for an A/T. That's one of the things DSMLink is good for-- they eliminated that from the ECU. To be honest, though, I can't tell much of a difference.

toojung2die · 06-14-2005, 09:13 AM

Thank you, I'm very glad to learn that it's normal. I wonder why that would be designed into the ECU. Or, maybe it's something they neglected to correct?

When I look at my WOT timing advance it's lower at peak rpm than other logs I see posted here. The max advance I see is ~16 degrees. Is this because I'm not tuning yet and tuning with an AFC removes air mass seen by the ECU and results in more timing advance?

Last question. Is there a way to increase the shift rpm at WOT with an A/T without a chip or DSMLink? My TPS is 1 at idle, 98 at WOT and my shifts are at ~6800 rpm. No slack in the throttle cable.

Like I said, I think it's important that everything works as it should stock before changes are made. If there is something that I need to correct I want to know about it. I see why having a pocketlogger is indespensible. Your experience is appreciated.

doug · 06-14-2005, 11:18 AM

My understanding is that it was designed that way to reduce stress on the tranny during shifts.

As far as shift points, when you're doing a WOT run, just shift it manually. Also, 16 degrees timing isn't bad.

tmizer · 06-16-2005, 02:34 PM

You should see significant gains by shifting manually. You'll need to practice as the shifts don't happen instantly, and the 1-2 and 2-3 shift delay are a little different. I use a shift light to help.

toojung2die · 06-16-2005, 04:36 PM

I'll practice the manual shifts. I may begin by leaving it in 2nd for the launch and manually hit 3rd. I plan to be back at "The Strip" Friday night. I was mostly concerned about the timing I'm seeing with WOT stock tuning. If 16 degrees and .98V from the O2 sensor @6800 rpm with stock boost levels is within expectations then I'm good to go with further modifications. I was afraid I might already be getting pulled timing with what looks like a rich enough mixture.