Hey guys,

Now that the weather is starting to cool down I can start tuning the really cold starts and warm-ups w/ my bank-bank FAST w/ wide band.

Here's my setup:
502"
10.2:1 compression ratio
242/248@.050", .541/.562 lift, 112 lobe seperation
1000cfm TB
40lb/hr injectors

My issues:

The engine runs really well when fully warm. It's the cold starts and warm-up that I'm having problems with. It seems that the problem is w/ the IAT enrichment. With the coolant temp and IAT around 35*, it'll start right up, and run for about 1/2 second, then die. When I start it up again, it stays running, always stays running on the second go around. My revs before after start enrichment vs coolant temp is at 5revs all the way across the board, and decay is pretty high across the board, it seems like it has worked best that way so far. My enrichment % is pretty high as well, my after start vs CTS is around 55-60% at 35*. My warm-up enrichment vs coolant temp is at 22% at 35*. Is it common to have really low warm-up enrichments, say less than 10% at really cold temps?

I can have the coolant temp enrichment near 0% and it'll still runs rich when cold, and slowly leans out. I'm pretty sure it's the ECU reading the IAT, adding fuel when cold, and leaning out as it increases. I've heard to leave this table at 0%, but it seems that my ECU is adding too much fuel when cold, and taking too much out when it gets hotter than when I tuned. My IAT sensor is in my open air filter element, so my IATs are probably higher than normal w/o a cold air intake type. It's not going into closed loop until 150*.

Any tips or suggestions would be appreciated.

Thanks,

 

What is your injector lag trime set at? If its long the the fuel will be to rich. If its set at say 1ms try going down to .9-.8 ms and see what happens. Then retune maps.

 

Okay,

After looking at the sensors more closely, it seems that it's showing my AFT% to be at 35% for a long period of time, like 5-10 minutes, and then slowly leans out.

On the After Start Decay Rate vs Coolant temp, how long does it take? I do not have a crank reference sensor, so how does the ecu know when to decay the after start enrichment out?

 

If the engine cranks soon enough for you then don't change your "cranking fuel".
If it dies right after it cranks you need more " afterstart enrichment VS CTS". This will be slow to get right because after you crank one time and it dies the next time it will probably stay running with the old setting. I would bump it up at least 10 to start.

I like my WB 02 correction to start at 120*. That will help you smooth out sooner.

I do run my IAT correction at 0 all the way across.

I run 5% warm up enrichment at 5 degrees and taper down to 0 at 120 degrees. So this could be part of your fat problem dring warm up.

What is your start IAC position at that temp (35*)
What is your throttle follower setting at idle? And does your iac mach your follower at idle withthe engine warm?

I would be happy to look at your .gct if you want. Just email it to.

Lots of questions I know. I have one more.

 

What do you have your After Start Revs vs Coolant temp at? Mine is at 5 revs all the way across the board, and I have my afterstart enrichment at 35% from 0 to 60*, but the AFT enrichment seems to be staying in for a long period of time, I think that's where all my extra fuel is coming in. I want it to decay out faster, but how fast is each "rev"?

My IAC position is around 60 at 35*, throttle follower is pretty low, less than 10, and the IAC matches it when warm.

My laptop is an old POS (no floppy/CD-RW/modem), so there's no way I can get the .GCT from the laptop to my PC.

 

Aft revs- 60 at 16 degrees, 33 at 39 degrees, 15 at 61 degrees, 8 at 64 degrees.

My afterstart enrichment is set at 35 at 16 until 60 degrees then tapers to 20 at 140 degrees.

 

Your cam has 10 degrees more duration that mine but you also have 120 more cubes also. Okay now I really feel bad.

I am going to bed post up and I will read Friday and reply.

 

Is this your After Start Revs or After Start Decay rate?

I'll try taking the decay rate down some, and see what that does.

 

That is my revs. Put yours there. But my decay rate is about the same. I would focus more on getting the fuel you need it the "after start enrichment" to keep the engine running. Sounds like you have the cold crank right but not enough afterstart fuel.

Let me know. I really enjoy tuning with this system.

 

I think I found the problem. I had my decay rate WAY too high, and was keeping the afterstart enrichment applied for too long. I got it where it would start up and stay running when coolant was at 45*, it's at 62* afterstart enrichment.

 

That does not sound right to me. What you explained in the first post was that it cranked and ran for a second or so then died. Then ran when you restarted. That is surely an "Afterstart enrichment" problem. The only way it would die from that is by flooding out or not getting enough fuel.

Wait 12 hours and crank again. Then adjust. Wait 12 more, adjust again until you are happy. Then you can adjust your "start iac" position to get the couple seconds of high idle, then down to normal that cars have.

 

Hey,

I got the afterstart enrichment problem solved. My other problem was that the decay was there for too long, got that fixed also.