Surging and LTFT questions on LS1

[Alvin]

There is not going to be a solution that will automatically work when the cam has so much overlap.

I'd suggest reducing ECM 12480 and increasing ECM 12470. You can find these by searching in the navigation bar.

I can't even make all setups drive OK with stock narrow bands. You got to remember a stock o2 sensor isn't meant to report back its 5% rich.. It just reports a rich/lean and how often its rich or lean drives the fuel trims up or down. For that reason there is no nuance between what the o2 sensor thinks is correct and what is correct.

If this was a standalone system with a wideband you could make the idle 15.3:1 and the cruise 14.4:1 and the wideband would chase that with fuel trims and that might make the car drive perfect... You can't do that with a OEM system.

[edcmat-l1]

In addition to the cam overlap causing issues, you've got 100 lbs. per hr. injectors that when varying in pulse width due to the trims +/-/+/-/+/- you can actually feel. The trims alone can cause some surge. You can help that some with injector timing and some other changes but between the cam and the big injectors it's always going to have some herky jerky feeling to it somewhere.

Tuning it to run in constant open loop and run well under varying conditions takes quite a bit of work and even after getting it as best it can be is not as good as running in closed loop. And if you have functional cats forget about open loop.

[abc]

Alvin, makes perfect sense to me now. I cut my teeth on an entry level Holley stand alone and keep forgetting what the NBO2's are not capable of. I will look into the two tables/parameters you mentioned and likely run some tests. I assume as I am now tuning with E10 fuel and reading in lambda, going back to CL will require a major overhaul of the base fuel map due to the NBO2's switching at 14.7:1 AFR?

Ed, your explanation of the 100 lb/hr injectors and the STFT varying the pulse width also now, makes perfect sense to me, thank you. My intention is to turn it into a flex fuel system for E85, hence the reason for the ID1050x injectors and fuel pumps to supply them.

I'm guessing the two tables you mentioned will answer some of these questions but is there a way to slow down the response rate of the STFT's? Basically as the NBO2's switch from lean to rich, rather than add 5% fuel in milliseconds, slow it way down and add that fuel over the course of a 1/2 second or so, then of course do the same for when it switches from rich to lean. I also assume with the info. you guys have provided, you have already explored this scenario and will tell me why or why not this may be an option. If the answer is in the tables you mentioned, then I guess if you read this before I get back to you, just tell me to go look at the tables.

Thanks again for your help.

[abc]

I found this: https://www.youtube.com/watch?v=5hjzI8wSItk
Have any of you guys implemented this strategy for cams that are on the edge or over the edge of too much overlap for good drivability below 2000rpm and if so what was your experience with it?
Seems to me to be a very good basic explanation of what's going on with cams that significantly change the valve events and alter the drivability due to what the ecm is seeing/doing.

[gtstorey]

Silversurfer77 is Cringer on this forum.

[mild7]

I will look into the two tables/parameters you mentioned and likely run some tests.

I'm guessing the two tables you mentioned will answer some of these questions but is there a way to slow down the response rate of the STFT's? Basically as the NBO2's switch from lean to rich, rather than add 5% fuel in milliseconds, slow it way down and add that fuel over the course of a 1/2 second or so, then of course do the same for when it switches from rich to lean. I also assume with the info. you guys have provided, you have already explored this scenario and will tell me why or why not this may be an option. If the answer is in the tables you mentioned, then I guess if you read this before I get back to you, just tell me to go look at the tables.

Thanks again for your help.

Some info about tuning STFT's :https://forum.hptuners.com/showthrea...g-with-headers post#4&6