mgilorma

I just started tuning and have got my VE tables looking good when the car is all warmed up, but since it just started getting cooler here in the mornings I realize that I need to learn how to tune for cold startup.

The car idles a little rough and almost stalls out as soon as I try to get moving in first gear. Its a LT1 cam swap in a 305 with 8746 and 61 mask.

Thanks in advance!

grdpdr305

I just had the same prob the other morning in Michigan. 40 deg. morning made all my BLM's jump to 130's-140. I've got the same setup you have w/ a 210/214 .474/.474 cam. I know there's a couple tables for IAT vs. BPW correction but I'm not sure which way goes fatter/ leaner.

mgilorma

I guess what I am trying to figure out is tuning in open loop? I thought I read somewhere that in open loop the BLMs are locked at 128??? I guess I'll just keep searching and see what I can figure out.

Ronny

iTrader: (1)

When I added IAT I just used stock tables(IAT vs coolant temp) for 305. My open loop VAC tables I enrichened. For instance I multipled table by .95 factor. That put 14.7 at 14.0. There is also a coolant based table to modify A/F based on coolant temp. They are a negative number. Higher neg# I recall is a leaner A/F.

I use CL for my tuning but did change the above somewhat as I have a cold intake with fuel dropping out on cool start especially when environ temps are <60dF.

mgilorma

I reduced the values in the "Choke - AFR subtracted vs Coolant" table by 1, that seemed to help a little as far as the driveability when cold. Although it still wants to fall on its face when starting out.

From what I gather, its "OpnLp - Open Loop AFR vs Engine temp" + "OpnLp - Open Loop AFR vs Load" - "Choke - AFR subtracted vs Coolant". So when I decreased the Choke table, I actually raised the AFR, right?

Can I tell from looking at my datalog if I am heading in the right direction?

Ronny

iTrader: (1)

Choke may only be in effect for a few seconds. then it decays out.

open loop logs may not be of much help. Unless a WB A/F is in log. Coolant based modlifier is what you need to look at after choke is decayed.

I forget how the choke tables work, But if I hazard a guess the values shown for choke are subtracted... Like table is -2.2 at 40d F so 2.2 is subtracted from OL tables after coolant temp mod is done.

mgilorma

How would I know when the choke is decayed? According to the choke table it goes away at 198 degrees.

According to my datalogs it goes into closed loop at 187 degrees, at which point my idle BLMs are way rich (113). So I guess I'll have to do some more reading on that issue.

Ronny

iTrader: (1)

That cant be right. Some days my car will never see 198 degrees. Choke cant be on continuously. I am of believe choke is on for seconds when environmental temps are above 50dF. There is a decay(filter?) somewhere for choke function. But if it is on continuous that is of no help.

I have CL threshold set to 160 d F. In cold environment maybe 170 is better.

mgilorma

Well I'm sure the "choke" isn't "on" at 198 degrees. I'm using TunerPro RT with 61v2.xdf. There are two constants and three tables that reference Choke.

What I was referencing before was the AFR subtracted vs Coolant table, which if I understand it correctly is in effect as long as the car is in open loop.

Is there anyway to tune open loop without using a wide band O2 sensor? Once the car gets out of open loop it runs better. While in open loop it just about stalls out when starting out in first gear. Actually if I am under 1500 rpms in any gear it just about bogs out.

Ronny

iTrader: (1)

Possibly when at 198dF there is no choke available. That would be a restart when car fully warmed. That makes more sense now that I think a bit.

Reducing the values would reduce the A/F or lean it out when choke on. I believe that is accurrate

I would look at the OpnLp - "Open Loop AFR vs Engine temp" table to enrichen A/F under 100F coolant temps. maybe enrichen 5%.

Then add some enrichment in the "OpnLp - Open Loop AFR vs Load". Maybe 5%. Be carefull as some tables are VAC and some are MAP. 0 VAC=100MAP