Why do I go lean after start up for a few seconds?

[echo412]

Hi guys, would love to hear your opinions on these questions:

1. Why do I go lean for a few seconds after start up. It does it every single time right after I fire the thing up.
2. Based on the quick pull (15:53 minutes into the log), do I have a too big of rear gear?

Some additional info:
-Car is 85 RX7 FB GS and probably with me in it weights ~2700lbs
-LS1 5.7, LS6 cam/intake, 317 heads, 60 lb injectors, T56 m6, meth comes on at 5lbs and runs on 93, OLSD
-I asked for 3.55 rear when I got my 8.8, but I now doubt it and feels more like a 4.10.
-I am a novice tuner and never tuned a car before this car, so any other "constructive" feedback is appreciated

Running Tune - change file 23 - Meth Tune.hpt
8-6.hpl

[2xLS1]

Does this mean you're not buying Cliff Clavin's explanation on the other forum?

[echo412]

That is one man's opinion. As I said over there, it's an interesting thought. I need to hear more opinions on this.
What are your thoughts on this condition?

[anniversaryss]

Is it on cold start or after the cars beem running already then restarted? I cant loook at the log right now.

[echo412]

Cold start. I have noticed it doing milder episodes of going lean after a restart but it's very rare. Mostly, when I start it up first thing after it's been sitting for a day or more.

[kingtal0n]

when an engine is cold, fuel doesn't vaporize easily. The colder the intake/valve/cylinder the less fuel will vaporize. The ralationship is governed by something called a partial pressure, which is dependent on temp and pressure. Having a larger cam means the pressure is higher at all times near idle (closer to atmospheric) so immediately all else equal extra fuel needs to be injected even when temperature is warm. So extra fuel needs to be injected for the full amount necessary to achieve the chemical stoichiometry, both because of pressure and temp.

This can be accomplished using the "EQ ratio" (or something like that) button where it shows values that range from say 1.15 to 1.00 at fully warm temps. Simply adjust the numbers up 1.01 to 1.xx+ at the pressure and temperature displayed, i.e. 80*F and 50KPA 1.15 to 1.20 is a typical value for gasoline with a cam.

note that it doesn't hurt anything to run lean ratios near idle when cold, 15 and 16:1 is fine for the engine. I let mine run 16.5 for a bit, its not an issue. Saves some fuel. As long as the engine response doesn't suffer. Yours might because being a manual transmission you might notice the difference when stepping down. But mine is auto so there is very little difference to me noticeable.