Just about finishing the tune in my b20z im just having some issues with startup afr. On a dead cold start its like 10.8-11.4 for the first 30-45 seconds till it slowly comes up to around 14:1. I Can remember hearing somewhere that its ok to run a bit rich to prevent rapid piston expansion and possible wear but idk if thats too rich and going to cause issues. Ive tried leaning it out but that causes issues on warm starts. Even though I have startup rpm set at 1500 it runs at like 1000 rpm for a sec right when it fires up

For what its worth its running around 30 degrees timing.

 

What is your post start trim set to currently?

 

Its going between 2 and 3 . 4 makes it too rich. Ive also been trying to use the ect corrections I have the 31 degree lower than the 67 column to try to help too. Its been around 30 when I go to work but gonna be in the high teens the rest of the week

 

I'm having something similar with Neptune. With my current post-start values, summer startup is perfect. But in the winter, my post-start AFR's are wicked rich - like in the high 9's sometimes. Its like the colder the IAT's, the richer post-start trims the fuel. Why is this? I have ECT and IAT values tuned to perfection for all temps, its just that darn fluctuating post-start trim!

What I end up having to do each winter is drop the post-start values a little to compensate, and then take them back to what I had for summer. It's getting more annoying as the seasons come and go. Is there no IAT dependent post start trim feature anywhere?

 

well i got it to the mid 12's it was a bit picky.

im still curious about how rich especially at idle you need to be to cause damage. i once had a very reputable tuner tell me that 11s at idle was not an issue because it was physically a small amount of fuel to get that afr with the very small load the motor has at idle

 

Is this Neptune?

 

yeah. ive been using it for many years now, got it i both my turbo car and daily driver

 

Are you running stock injectors?

 

just as an oddball thought, do you think the af gauge is accurate until it warms up? I know they usually have about 30 second warm up time

 

Then start your vehicle and let it run for at least a minute. Your wideband will take some time to warm up (it has built in heater control, and it will need to stabilize).

posted from xenoncron.com

 

well, they are prelude 290's.

i turn power on but dont start the car for a minute until the wideband reads lean not 14.7.
after that its up and running about 2 seconds after the car starts.

i have myself squared away for the most part at the moment, so i guess this is just a conversation about theory - how rich at idle before it causes damage for any one

 

usually wide bands read LEAN when warming up though.

 

haha so it sounds like it is either your tune, or possibly the gauge?

 

it was the tune. i fixed it. at this point im just curious about the theory of too rich at idle for any car to the point where you start running into trouble.

 

I am as well. Guess thats why we tune for 14.7. My engineer buddy at cummins tells me 12.5 would potentially be dangerous for long term use at idle

 

My car starts at 14.7 hot or cold dunno what the tuner did hah

 

Some of the best tuners will say 11-12 is ok under light load if u gotta drive to see the tuner... Same for running 17+... Apparently not hurting anything short period of time.

Rich mixture def kills rings tho

 

In my opinion 11:1 would be as rich as I would want to get on cold start ups. Washing rings can happen rather quickly but I base my opinion on exhaust smell. Another thing people continuously overlook is the start up decay rate. You adjust this as well for fuel enrichment drop off. Most cars run pretty rich (even lower than 11:1 in some cases) from the factory on cold start ups and have a slow decay rate. To each his own...

Every engine will want something slightly different due to fuel, compression, restrictions, etc... I can tell you i have one motor in particular that gets pissed off if it's leaner than 12:1 when it is cold haha. Thing wants it's fuel. Speaking of which, E85 gets to be a real PITA during the teens / single digit or less type weather.