LT1 24x help with low load/ low rpm driveability and cold start

I've managed to fix nearly every issue except this low load/ low rpm bucking. The only thing that seems to consistently help is running richer. I increased the VE table values in the cells that correspond to city driving (25-40mph) and that helped a lot. I wanted others to look at my file and make sure I'm on the right track.

The other issue I have a question about is cold starts. The closer the engine is to operating temp, the faster it will start. From 100-185* I turn the key for a split second and the engine is running. When it's cold it has to crank for a few seconds. What table do I need to change and how do I change it?

The attachments are: my current tune; 2101566VE is driving on the freeway with MAF disabled (I have since reduced the 50-100kpa cells in the 1600 and 2000rpm columns); 21015MAF is driving on the freeway with VE disabled; 21715eburg is a drive I did last night with everything enabled. It starts with city driving and a WOT pull, then I'm on the freeway for the rest of it.

For the starting issues:

One of the areas I would look at is the Afterstart Enrichment in the fuel tab. It took a little trial and error, but the LT1 wants less fuel on cold start than the LS1.

One other thing I noticed is that your cranking VE and your primary VE are not even close. Mine starts fine cold or warm but my cranking VE table is a lot lower than yours:

Attachment 48794

I'll look at your log files and see if anything jumps out.

I think my Ultradyne (230/236 .565/.565) is larger than your CC503 and I don't have any bucking. Can you point out some specific area in a log where the bucking is occurring?

I'll post my latest tune in the next day or so for comparison.

Thanks,
Jason

Your B1 vs B2 LTFT are way off. Is there a reason for that? Just a shot in the dark w/regard to the bucking....

Jason

Yes, your cam is larger. Mine is a 224/230 .503/.510. If my speed is below 45mph in any of these logs, the car is bucking. As far as the blm split, are you talking about when I'm cruising at 73mph? Not sure why it's split like that but it was silky smooth. Thanks for responding!

So mine should act a lot bigger since mine is still 350ci. Maybe back the timing down a little? Mine is lower in those areas of the timing table by 4-6 degrees than yours. I only have a tune from a month ago at work, so I'll post a more recent tune tomorrow so you can compare it to yours. One other thing I noticed, I don't typically drive at 1500 rpm. So I may be avoiding the bucking areas of my tune. Have you tried running 2K+ around town?

Thanks,
Jason

Good idea with the timing but I've had it as low as 28* and it actually gets worse. I just set it for maximum vacuum. I usually cruise around town at 1800-1900 rpm, I only hit 1500 rpm doing 60 on the freeway. Looking forward to seeing your tune.

Here is my current tune. Still a ways to go and I've done NO WOT tuning at this point since I haven't gotten my WB installed yet.

Attachment 48806

Looking through your file, how did you set your zone rpm and map boundaries? Otherwise I see our MAF and VE tables are very different. How are you tuning those?

They're the same zones I was using in LT1 edit and they seemed to work well. With the stock zones you just don't get to all the cells anymore.

I set the VE table to what I had tuned in LT1 edit as a starting point and then disabled the MAF and tuned the VE. MAF was the reverse. I did notice that your VE table is much smoother than mine. How much smoothing have you done? I would expect there to be differences since the displacement, heads, and cam are all different. As I noted, I've done NO WOT tuning so the VE tables at higher RPM / flow are not complete

Did you look at the cold start differences?

Your injector data is a lot different than mine too. I haven't spent as much time with anything but the injector flow rate table.

Thanks,
Jason

Didn't know that about the zones, thanks! As for the VE table, since it's around 60* outside right now I'm aiming for cells values from -5 to -7. Now that I've got the basic shape of my VE table, the columns usually match pretty well. If there's an outlier I figure I didn't hit that cell long enough and smooth it over. For the cells I didn't hit I just mold the VE table so it maintains the same trajectory. What kind of BLM numbers are you getting? It was my understanding that larger displacement engines have smaller VE table values but mine are larger than yours.

I cut my afterstart enrichment and that didn't seem to help. I'm wondering if the cranking fuel tables are what I need to mess with instead.

Someone here posted that injector data from the Banish dvd so I just copy/pasted since we were using the same injectors.

I tried messing with the spark again and decreased it to 19* but that didn't help at all. I smoothed over that hump in my VE table and tried increasing the MAF curve but that actually made it worse. Strange since making things richer has helped in the past. I feel like I'm either missing some tuning concept or procedure, or I have a hardware issue. People keep saying their car is smooth with larger cams so something clearly is not right. Especially when all the tried and true advice like reducing spark advance isn't working.

I'm just starting to go back into closed loop after VE table and MAF tuning. So I don't have a lot of data. What I do have is mostly -2 to +2. So I do plan to do a global tweak to move that more toward -3 - 1 or so. The VE table values are a function of displacement, heads, intake, exh and cam. So looking at your setup and mine, I would expect your table to be flatter than mine. IE, larger values at lower RPM and maybe similar to smaller values at higher RPM / MAP due to the size of my cam vs yours. And that is more or less what it looks like.

Yeah your cranking VE looks too large and doesn't match your primary VE.

What fuel pressure are you running? From what I remember the LT1 pressure is higher than what the SVO inj were rated at 30lb.

Have you tried just running around town above 2K? In your previous log you do spend a bit of time at 1500 around 45mph. I do get some surge if I try that.

Thanks,
Jason

Didn't know that about the VE table, thanks. I haven't matched the cranking VE yet because I haven't felt like my primary VE is done. Once I feel like I've got it where I want it, then I'll match it. I'm running at 43.5psi but I've calibrated for that with the injectors. I have tried driving around in 3rd which puts me at 2300ish rpm and that doesn't make a difference. Still get those little jerky sensations.

Yeah, I'd at least get the cranking VE closer and you can finalize it once the Primary VE is finished. This should at least help the cold start. Or just copy and paste my cranking VE and see if that is better than what you have.

You have the "Red" SVO 30lb injectors? I think my FP was ~44 or 45 from memory. I'll check it again. I may be running the wrong injector constant then....

Good info on the surge. Mine is good in 3rd above 2K. So something is definitely going on.

Thanks!
Jason

I have the fat red tops. There's a newer Ford 30# injector that is entirely red and skinny. I'm at work so I can't link where I got my info from but I can send that to you later. I'll also be able to get some more tuning done in the next few days.

Cool. Those are the same inj I have. I'd appreciate the info.

You dont have an aluminum flywheel do you?

yes, and I considered that. However, running richer helps smooth things out and running open loop almost fixes it completely. I can also hear faint pops in the exhaust while under low load/ low rpm conditions and during those instances when it runs smooth (either richer or on the freeway), those pops aren't there. Makes me think the flywheel is contributing minimally to my problems.

I received some helpful responses on another forum that I wanted to ask about here. The guy is running an LT1 PCM so the tables and options have different names for him. Is there a way to adjust individual injector trims with hptuners? He suggested getting an IR thermometer and adjusting the trims so each cylinder is the same temperature. Also is there a way to adjust the O2 sensors to compensate for headers? He mentioned O2 delay but I don't think hptuners has anything like that either.

Quote:

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He mentioned O2 delay but I don't think hptuners has anything like that either.

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Yes, its call transport delay, you can add to the existing number and it may help since you have LT's and the 02 sensor is further than factory.

No way to adjust individual cylinders in the LS1 ECU.

Are you talking about "closed loop integrator delay"? That's under Fuel > Open & Closed Loop. Then there are two tables: Airflow Mode and O2 Error Mult. It looks like O2 Error Mult is what you're talking about. There doesn't seem to be a lot of discussion about these tables after google searching but it looks like you increase the O2 Error for headers to compensate for different O2 location. Anybody know about this?