Why do I go lean after a cold start for a few seconds?
Why do I go lean after a cold start for a few seconds? 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 a cold start.
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
Thanks
1. Why do I go lean for a few seconds after start up. It does it every single time right after a cold start.
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
Thanks
Last edited by echo412; Aug 9, 2020 at 10:37 AM.
TECH Senior Member
Joined: Jun 2016
Posts: 22,291
Likes: 3,616
From: Central Cal.
My guess is that when cold, gas does not vaporize as well, nor burn as completely, leaving more unused oxygen in the exhaust, which would then show as a lean condition. And the fact that it's only immediately upon a cold start, and only for a few seconds, means it's all normal.
your idle fueling is too lean so right at first its not using the fuel trims. Fuel trims kick in, it goes to normal. Add a touch of fuel to the 400rpm and 800rpm range. Maybe Just one or two numbers.
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