Yet another question about Throttle Cracker

[workingdog]

I enabled Throttle Cracker and it fixed my stall when coming to a stop, but now I have a bit of a hang. So, I finally need to understand decay rate and decay delay. My decay rate is .06 g/s and my decay delay is .08 seconds. What does that mean? Is it taking an additional .06 g/s out of the added airflow every .08 seconds? So, for a cracker airflow value of 4 (2200 rpm at 22 miles an hour for the stock tune of my truck) that would take 5.3 seconds?

To make it decay faster I can increase the step size or increase the decay rate? Have i got that right?

If I cut my cracker airflow table in half (making it 2 g/s at 2200 rpm and 22 miles an hour) and increase the step size to .1 and the decay rate to .1, then it will take 2 seconds to remove the cracker - that sounds like a reasonable amount of time to hold the idle up.

I will give it a try and report back.

[workingdog]

So, throttle cracker stop the stumbling coming to a stop, but now I have a hang at speed before I get to the stop. I already reduced the throttle airflow table by half and I reduced the delay and decay. But it's still doing it. So, I'm considering radically reducing the airflow over 15 or 20 mph and see what happens.

[dmaxs10]

Sub for info. Have same issue.

[Pitbull]

Disable the throttle cracker and work on the overspeed/underspeed tables. +6 degrees undershoot and -4 degrees overshoot is a good place to start. Around 8.5 gm/sec drive and 8 for P/N is where the last 5.3 with a middle of the road cam I did was happy, his first complaint was the hanging idle you described, disabling the throttle cracker and setting over/underspeed settings took care of it.

[C5 2000]

pull some timing out from Idle Spark Advance in Drive and in park in the 1200 and 1600 RPM

[workingdog]

I'll disable cracking and work on overspeed and underspeed.

I actually had to add idle spark to get the thing to stop stumbling when coming a stop, it helped, but I was using crack to try to get rid of what was left - but I'll look at the 1200 to 1600 range and see if I can take some out there.

Why is there so much idle spark above 800 rpm and below .5 airmass? At .12 air mass there's over 40 degrees of spark from 2,000 rpm up.

[C5 2000]

when you flip the throttle it will come back to 1200 and 1600 RPM and you are going to be at the normal idle load rang 1200 and 1600RPM, this is where the hanging is occurring. So you need to pull timing out 4 or 5 degrees out of the range 0.08 t0 0.28 will reduce torque and bring the idle to a normal range

[workingdog]

Thanks C5 2000. I will try it today while everyone else is shopping.

So, do I smooth that change in to 2,000, or leave it abrupt?

[workingdog]

So, I did that, but there's no change in in timing when I'm off the throttle as any speed. How the hell does idle spark work? Should it be the max? I've got spark down to 24 in that range and i'm seeing timing at 50 in the scanner. Do I need to go to overspeed?

[C5 2000]

can your post your file it could be many things like your Base Running airflow or something else

[Pitbull]

you are tuning the closed throttle table right? x2 on the post file request, its too easy to point you in the wrong direction without all of the details.

[workingdog]

Here you go - I appreciate the help

Yes, I believe I've been doing it right - but then, if I were sure, I wouldn't be here
MAF disable, VE tune 3600 and up.hpt
11 23 longer run.hpl

[C5 2000]

can you post your stock tune please, and try to compare files. Start with putting back stock MAF timing and do what I stated above pull some timing out from Idle Spark Advance in Drive and in park in the 1200 and 1600 RPM in the in Drive and in park. did you change Injector?

[workingdog]

Stock tune stock 6 liter tune.hpt

Yes, took some timing out as recommended, you can see the 'divot' in the idle spark table.
Also added a larger negative value to overspeed as well.

My injectors are not stock.

Peter

[workingdog]

Here some runs from today. I added cracker, follower and commanded idle just to make sure they weren't the culprit.11 25 lots of coasting.hpl11 25 more coasting.hpl

I can't see any evidence that is overspeed is having any effect. It should be taking timing out, but it sure doesn't look like it's having any effect.

[C5 2000]

I always leave Overspeed and Underspeed stock in my tunes.

[Pitbull]

I do unless the cam makes the idle too erratic, which looking at his logs it doesn't seem to be the case now that I finally got to see them.

Looking at the tune the follower decay rate is really low, and the delay is at 1.5 seconds. I have around 50 g/s decay rate in park and 40g/s in drive across the board with the delay at .5 on my 6.2 denali and it revs and returns like I want it to, as in it falls like you shut the butterflies on a carb motor. Maybe worth a shot there?

[Pitbull]

Any Luck with it?

[workingdog]

Not really, I'm tracking cracker and follower and they clearly aren't the culprit as you can see follower coming and going very quickly. Cracker is totally disabled. I can't see overspeed taking any timing out. I can see timing sitting at 50 when TPS goes to 0 for quite a while. Far longer than follow stays enabled. It takes a long time for Idle Advance to finally start taking timing out. I never seed overspeed taking any timing out (but then you can't track that, that I'm aware of). So, I'm not sure what to do next, other than to take more timing out of Idle until I get the stall on stopping to come back and then ease a bit back in.

I'm about to take a longer drive to HomeDepot, so I'll see what happens.