P59 dbc 3bar turbo Silverado tune.

[bbowerman]

Hey guys I haven't posted here in a long time but I have a problem I just can't seem to figure out. I have tuned many gm vehicles from nitrous to cam only to supercharged and turbocharged and they all have started and ran fine. I finished this truck a couple months ago and it's a monster it does 4wd burnouts until you let out and rolling 70+mph 2wd burnouts. The ve and timing are dialed in and it runs perfect. However I'm having a startup issue. The truck does not like to start for some reason. Anyways here's a rundown of the truck and what I have tried so far.
Truck info
1999 Silverado 5.3/4l80 4wd manual tcase p59 dbc ecm swap with 3 bar OS and flex content sensor working.
10:1 5.3
Tbss intake
G-plus 92mm dbc throttle body (eBay)
Ported 706 heads
Elgin e-1840p cam
7875 1.25ar vs turbo
88lb injectors (flow matched oem decaps)

My buddy has a suburban that is very similar other than 9.5:1 a e-1838 cam and p01 ecu that I tuned and it works wonderfully that's what has me puzzled.

What I have tried
1. Raf was dialed in
2. Iac vs effective area was tuned using a user math to match idle desired and dynamic airflow
3. I've added a ton of startup airflow and taken a ton away both show no change
4. I've modified the cranking ve up and down with no change
5. I've modified the cranking fuel FA mult table values up and down a little at a time until they where double and then they where half no effect.

I notice that when I start the truck if I give it gas pedal and allow air in it will start up but I have to help it for a second sometimes. Once it starts its gold. When I do a datalog and try to start it the desired airflow is really high and the stit go way high. I've also noticed an inconsistent iac counts. Sometimes I start it and at 72? with an ambient temp the counts are at 50-60 then I can kill it come back later and they are at 120-125 with the same afr and ambient temp reported. Both datalogs taken the same day. I thought it could be the cheap eBay TB iac is too small so I ported it to death redid my raf and effective area it gained some flow on the effective area chart before counts where maxed but still doesn't want to start. I then opened the throttle body up to where the iac counts at operating temp are 0 and the stit goes way - so I disabled the - ltit learning and it will start that way. Basically the engine is wanting a ridiculous amount of air to start up and idk why. My mind says it has too much fuel at startup but I've modified that so far down theres no way it was getting too much fuel. I'm at the point I think it may be an issue with the ecm or something else.

[bbowerman]

At operating temp I can use the scanner and the iac is able to idle the truck over 1750rpm so it's moving some air. I'm thinking maybe an issue with one of the segments I swapped as this ecm was originally an express van 4.3 ecm. It has a flex fuel Tahoe segment in it. I've even tried copying every value from my buddies suburban into mine then modifying that with no luck also.

[kevin87turbot]

Post the tune when you get a chance. I'm sure we can help you.

[bbowerman]

attached is the tune file. the raf isnt 100% dialed on this one because i was making changes to the TB but it is pretty close. thats not my issue though its only startup thats giving me fits. this tune is scaled for timing control thats why injector flow rate isnt correct but ve is great and all within 1-2% done with a wideband.

[bbowerman]

23-01-08 17-54-29.hpl here is a datalog of trying to start it. Tps voltage is low because its a 92mm TB that ive had for about 4 years now. when i first started tuning I drilled a hole in the blade to help with tuning. I now realize i didnt need to do that but it still works fine and I used it on this combo a few years ago except with a p01 ecu and it worked fine for me then. it does function 0-100%t tps like it should.

[bbowerman]

Also the harness on this is aftermarket and goes behind the passenger side dash. The powers from it come from the starter post but I don't think that is causing any type of issue because it's made to be like this. And ever since I swapped this ECU into the truck it's had a cmp/ckp variation not learned. I have tried relearning in the scanner multiple times and multiple different ways but it never does anything. It's never caused any issue driving whatsoever but I forgot about it until just now.

[Fast4.7]

Also the harness on this is aftermarket and goes behind the passenger side dash. The powers from it come from the starter post but I don't think that is causing any type of issue because it's made to be like this. And ever since I swapped this ECU into the truck it's had a cmp/ckp variation not learned. I have tried relearning in the scanner multiple times and multiple different ways but it never does anything. It's never caused any issue driving whatsoever but I forgot about it until just now.

I have a P59 that was struggling to fire when the engine was cold and would idle really rough on a slightly warm restart. I discovered the PCM was commanding a cranking air/fuel ratio of about 3:1 when this was occurring. I ended up having to adjust the Fuel Air Multiplier under Cranking Fuel and actually decrease the fuel. If adding airflow is helping it start, your mixture is probably too rich.

Have you actually logged the commanded air/fuel ratio and pulsewidth during cranking?

[bbowerman]

Yes Its logged in that log I uploaded. And mine does that too. It commands a super rich afr. I adjusted the cranking FA mult stage 1 vs time and it helped a lot. I almost feel like I'm burning the book at both ends tho. I think it has too much fuel and once I remove the fuel it has too much air because of the amount of air I'm putting in it currently to help it start. I'm waiting on a new charger for my laptop mine broke yesterday of course lol once it makes it in I'm going to try lowering that and the air both to see what happens

[kevin87turbot]

How did it start before you scaled the IFR/VE tables? Typically, when you scale like this, you'd also need to scale the cranking fuel table by the same amount.

[bbowerman]

I scaled the cranking ve the same as the primary ve. This setup went from 4.3 express van to 5.3 Tahoe flex segment 3 bar scaled in one write never ran it unscaled.

[bbowerman]

I didn't scale the FA Mult stage 1 vs time though. I've never had to before on the p01 ecus but maybe so on this p59

[bbowerman]

I'm going to try and remove a bunch of afterstart enrichment and cut back the startup airflow to stock setting plus 1 gram and see what happens. It's not commanding an overly rich afr. It has 56% ethanol content in it right now which is around 11.25-11.3 stoich. It was commanding a low 10 afr and started then the commanded afr went down a little into the 9s and that's when it wants to die that's why I removed the afterstart enrichment at that temp. And cut it significantly in other areas.

[bbowerman]

Laptop was almost dead but I was able to write those adjustments and I opened the Throttle blade some because it still wouldn't start with iac counts at 310 and commanded afrs are fine. it will start now and idle fine but the issue I'm having is the iac counts will go down to like 90 at idle and up to temp with efans running which is good. If I kill it and come back in 5 mins and do a datalog the iac counts up to temp are at 0. I don't understand why they change like that one datalog they are at 80-90 the next one they are at 0. I can leave it like this for now because it does work but the iac thing bothers me and i am one of those people that can't just leave it alone even though it works I need to know why the iac counts are doing this. When they do this it makes the raf log off in a different direction everytime because the calculated airflow variation through the iac throws it off. I can even retune the iac vs effective area and it won't matter this still happens

[reubone]

Try modifying your IAC Steps vs Effective area table. Take the numerically lower portion and make them read up to your desired minimum. That may take care of some of your issue. Screenshot (83).png

[bbowerman]

I may do this to keep it from bottoming out the idle trims I could force it to a minimum of 35-40 counts and ignition will still hold the idle. Timing can control the idle fairly well on this setup. A few days ago just for informational data purposes I commanded the iac closed unplugged it and opened the throttle blade, it started and idled with nothing but under/over speed ignition timing. I had to set the idle slightly higher to achieve this but it worked lol

[bbowerman]

So my pretty sure the issue is the eBay throttle body. It worked on a previous setup but Ive modified and ported it to make it work. My friends turbo suburban I tuned worked fine with this same throttle body so it had me scratching my head. I looked at his vs mine today they look identical except they changed the iac port design over the years. I ordered one from the same place he got his and will be trying that. If all else fails I'll do what reubone suggested

[reubone]

Any updates on this?

[bbowerman]

Any updates on this?

my laptop charger broke and I just got my new one in today. I have a new throttle body that should be here today, so I can start with a fresh unmodified one, however I noticed that the startup was getting even worse. I had a thought to check the spark plugs because they where put in a few months ago when the truck was first built and I tuned it with them along with having a leaking set of injectors on them that I changed. they where definitely bad. I swapped those and it started by itself but still kinda stumbled at first. I should have it solved this weekend for sure.

[bbowerman]

So I did a few things that improved the startup drastically. 1 I took about 25% of the startup flare control out of it. 2. I quit listening to my wideband under 1000rpm (because I have a very minor leak at the v band on the back of the turbo) I suspected the 14.7-14.8 I was showing is actually 13.7-13.8 adjusted ve until it read 15.7-15.8 at that areas. 3. I did the iac effective area minimal mod like shown by reubone. And it's way better. Still not 100% but for sure liveable/useable

[bbowerman]

Got the new throttle body in a long with he other changes and it's fine. Just needs an raf adjustment to be fine tuned and it will be great.