HPTuners SD Tune (VE Table) Hesitation

[rrrocketman]

Hey everyone I'm wondering if other Camaro owners have noticed the same. I've tuned in my VE table more than half a dozen times so that my trims were all pretty close to +/- 1. It was really smooth and perfect. Then some time passed and the tune started to fall out of calibration even though I changed nothing with the car. Now I've heard that with an SD tune, the fuel trims should be exceptionally stable unless you change something physical with the setup, as opposed to a MAF tune. Aside from that, I'm getting little blips in the power band. What I mean by that is, I'll mash the gas and the car will hesitate ever so briefly at certain points, almost like it's hiccuping or something. It's pretty weird. I just don't understand why it does that when the tune has been previously dialed in to a high degree of precision. Finally, I'm getting some hot idle surging... up and down, up and down on the tach as it hunts back and forth between about 500 and 700. Sometimes it damps itself out but sometimes it'll go like that for minutes. None of these symptoms occurred on my MAF tune but the MAF tune has far lower resolution than the VE table can offer. It should be vastly superior. Anybody seeing this with their car?

[Rhino79]

What the engine wants on transient fueling vs what it wants during steady state/load is 2 different things. The maf offers great stready state function, and the ve coefficients can be utilized to over seamless tip in response. But even in SD the ve table can be dialed in to not hesitate. Sometimes you have to put the wideband, the o2s and all that aside and tune for what the engine wants.

[rrrocketman]

Thank you for the explanation. I had assumed that tip in fueling was managed by other tables or functions, similar to how the old GM PCMs used acceleration enrichment to do so. Are there any specific tips or techniques you would employ in SD mode AFTER having dialed in the VE table for excellent steady state operation? I should mention I have also calibrated the temperature table so that heat soak won't change my VE values.

[thahemp]

Do you have any logs of what is happening when it hesitates? I would figure out what is causing the problem you're feeling first, then figure out what to modify in the tune to fix it. Is there are reason you are trying to run VE only?

[Ryne @ CMS]

i second transient fueling.... play with the transient fueling and you'll fix it

[rrrocketman]

I can't say exactly what's causing the hesitation because a bunch of parameters seem to change simultaneously making it hard to identify the root-cause. As for VE only, it's one of the HPTuners upgraded OS that allows 1.75 Bar of boost, which I am going to need. On top of that, the number of cells in the VE table vastly exceeds the number of cells in the MAF, making it a much finer resolution matrix to control fuel with. Third, it's less sensitive to fouling and weather, once properly tuned, so I've heard.

When you talk about "transient fueling", to which specific table are you referring withing the HPTuners suite? There are a ton of multiplication tables and such and I just want to make sure I'm adjusting the right one. I tend to agree though. If the spark is too high in a given cell and there's a bit of KR, a spurt of gas might alleviate that.

[Rhino79]

For example, if you are at 1200 rpm cruising, you tip in to id mid throttle and map kpa goes from 45 or 50 kpa up to 75-80 kpa and you feel a delay/hesitation between throttle input and actual acceleration, I would bet its lean during that tip in. Add 5-10 percent at that higher load kpa, save the file as a new file and try it. If it helps, tune it by feel as far as the tip in goes, at the end of the day, fuel trims and wideband accuracy on certain setups just aren't good at lower rpms where the engine isn't efficient. Sometimes the overlap of camshafts will cause false trimming of fuel, and on boosted setups, you have to think you may be going from 50 kpa to 110 kpa or more on tip in. Lead the fueling on the ve table a little bit and try it, or in other words intentionally make it a little rich and see how it acts.

[Rhino79]

Also make sure your PE enable throttle is set low enough to add PE fueling at high loads, and not need 60% throttle to go into open loop.

[2010_camaro]

Clean the MAF. I had issues with my fuel tables cause the MAF was throwing things off.