Problems with surging and stalling??

[blow03ss]

I recently installed a 408 stroker into my silverado ss and the thing runs great 99% of the time. I have had it dyno tuned and it runs at a solid 12.5 AFR at wot all day, but the day to day driving is really bad at times. However the truck is my daily driver and is proving to be a challange at times to drive in traffic. It will surge and then stall out on me with small stabs of the pedal in parking lots or reverse then drive. It is unsafe at times. Can anyone point me in the right direction on this problem or what to look at. Thanks

Im also willing to drop the truck of with someone for a few days of daily driving tuning. Is there anyone local to me in Philadelphia that offers service for this kind of tuning?

[WS6FirebirdTA00]

Can't point you in any direction without scans and a tune...

[blow03ss]

sorry about that. If you look at the log you can see it die on me at about the 340 frame. This parking lot driving.

[WS6FirebirdTA00]

you need to log idle spark advance, throttle cracker airflow, and throttle follower airflow.

[Russ K]

Do a cold start scan with this idle config file. Just let the engine idle in park till operating temp. Then do a cold start scan with the engine idling in gear. You could also do a scan while driving around, then coming to a stop to see what is wrong with the tune.

Russ Kemp

[blow03ss]

Thanks guys, I will give this a shot. And so it begins with the troubleshooting of my problem. I was going to just chalk it up to be PITA 60lb motrons. Thanks

[WS6FirebirdTA00]

those injectors will work fine.

[MNR-0]

Without decent log data its too hard to advise. Until you do, try this spark map for the cells 400-2000RPM and 0.04-0.48g/cyl.

50 39 28 18 18 18 18 18 18
50 39 28 18 18 18 18 18 18
50 39 28 28 25 25 28 38 46
50 39 28 28 28 33 38 41 43
50 39 28 28 28 35 37 40 41
50 39 28 28 28 33 35 38 39
50 39 28 28 31 33 35 36 37
50 39 28 25 27 30 32 33 35
50 39 25 23 25 28 31 32 33
50 39 22 21 23 26 29 31 32
50 39 19 18 22 25 27 29 31

That should stabilise your spark off idle. Also stamp those cells into the hi-lo octane tables as well as the spark advance in gear/neutral.

The rest is running airflow and controlling interference from the cracker and follower.

Note that your VE MAP shoudl be pretty spot on before even attempting to tune idle. As you will be fighting what the cars wants naturally by way of fuel.

This should help you along anyway.

[MNR-0]

Dude, whats up with your idle RPM table? Idle increases as temps rise above 80*C?

1180 1180 1180 1155 1125 1030 985 980 940 900 840 875 925 975 1065 1115
1455 1405 1355 1280 1250 1155 1110 1055 965 925 865 900 950 1000 1090 1140
1300 1250 1200 1125 1045 965 920 905 865 785 750 825 875 925 990 1050
1125 1125 1125 1100 1070 975 930 925 885 845 810 845 895 945 1010 1060

Other pointers:

Zero out your entire cracker table
You need airflow for your fans
With your VE MAP, VE values should be numerically decreasing with less manifold pressure. At idle RPM your VE values rise and fall in each RPM column. Blend in values with their surrounding cells, use the smooth feature, and follow the normal shape of a VE MAP.

[blow03ss]

Im a little confused here guys. I tried taking the idle config file above and saving it to use for my scanner and it will not scan anything. It will not register in the pid log. What am I doing wrong? Do I need to create my own config file with those pids on it? Just thought I could use the one posted.

[blow03ss]

Here is a idle log from cold start to warm up. Anything over 10minutes in the log is me pulling out of the drive way.

I also bumped up my stall saver and it helped things out but I think its just a band aid for things. When I come to a stop it feels like the truck wants to keep moving foward.

[Russ K]

There are a lot of problems with your tune. Why is the Stoich AFR changed to 14.577, and the PE set to 1.057? So 14.577/1.057 = 13.79 commanded AFR.
Your LTFT rpm & map boundaries are still stock, these need to be matched to your idle map & rpm since your idle & map is now higher than stock. The help files explain this. Your throttle follower in gear table is way lower than stock which will also cause the idle to hang. I always zero the throttle cracker table & max out the enable speed.

If your trans is stock it's not going to last long since you have stock shift pressures and the torque management is disabled. And 27* spark timing At wot is way too high. Not sure about using 60# injectors on a NA engine, and the IFR table should be flat. What mods are done to the engine?

And you didn't use my idle config file, as your not logging STIT.

Russ Kemp

[blow03ss]

That sucks cause I paid a guy $450 to dyno tune it! I have no idea where to start now, I thought I just had to tune my daily driving now it seems I have to retune the entire truck

[blow03ss]

So should I zero the throttle cracker table & max out the enable speed. Is this where I start at now. You have me worried about the Stoich AFR and the commanded AFR. I would think that someone could post up a 408 tune for me to look at and see how much different mine is from it.

[Quik]

this is a tune that was written by Ed wright for a 408 with ported ls6 heads, 30svo injectors, ls6 intake, ported TB, 4400 stall,410s and 11.1 cr and the cam is very similar to yours


60s are high IMHO, i run 42s and so far after one log im at 73% duty cycle

[blow03ss]

Thanks Quik, can someone help me scale a set of 60lb motrons to this new tune please. I know that the 60lbers are a little much but I had planned on putting a blower on this motor, but in the mean time its what I have to use. I would think that all I have to do is scale my injectorts to this new tune. I guess we are running the same amount of fuel press.

[Quik]

in your help section i think in hte tools part of it. it will help you scale them

type in injector rate, type in rated psi, type in your psi and then it will scale them. and for yours it should be one set number across the board




and if your motor is setup for a blower then youll be down on power now. but with that large of a cam im not sure if it will owrk good with a blower and what was your SCR again

[S2H]

sorry...to see that you got dyno scerewed...
I personally wouldnt just put somebody elses tune in there...
if you have the tools...which you do...other than a WIDEBAND(get one now)
then you can tune it your self the correct way
dop some reading...lots of how to's on here..
get your wideband
set the PE to command what you want for AFR..
dial in VE and MAF tables
dial in spark tables
dial in idle tables..
you will find out that your dyno screwer has done a LOT wrong in that tune
then you can take a good tune back to him...along with the one he put in....and fight toget your money back...
if you can get it done quick enough you could even take him to small claims court if you wanted to(probably not worth it)

sorry I had to rant...
I just had to fix a tune the other day that was a local dyno tune screw job...luckily the guy here was able to just go back to the guy and get his money back...the tuner flashed him back to stock and he came straight here after that and I tuned him...
I'm sure that tuner hates me cause I have redone so many of his tunes locally over the years

[blow03ss]

Yeah well the real bummer here is that I just got rid of my LM1 unit! Im just sick of having a damn laptop, wideband, fuel press gauge....blah blah blah. I just don't fell like having all that crap in my truck, so I took it to someone to have a safe dyno tune put on it so I could daily drive the thing.

Quik, the truck is 10:1 and it will not see a blower of spray for some time to come but I put the injestors on there with that in mind. I may not feel right about throwing another tune from another motor on it just due to the money I have in the motor. On the other hand I would not mind getting this thing running like it should so I could stop thinking about trading a 408 stroker for a stock LS2!

[jimmyblue]

As posted in the other big idle surging thread, I think you will
find the most relief in fixing the spark table. The values in the
one snippet seem high to me but the idea is right; you want
two things primarily. One, zero Y-axis (MAP / CYlAir) variation
in spark. Two, a flat spark to the right of idle RPM and an up-
slope to the left so it's got a natural tendency to return to
proper RPM. The flat Y dimension really cuts down MAP
oscillation (surging). Bouncing MAP gets into fuel and spark
and it's too messy.

Zero the overspeed idle spark correction. Make sure underspeed
is not insane, that it leaves you alone out to -100RPM and that
the value never decreases as you go negative all the rest of the
way out.

Raise your base running airflow to the value of Dynamic Airflow
you see at a steady idle.

Check whether any residual surging tracks A/C compressor
cycling. The A/C torque value can be large especially at high
IATs and add excess air, then you track (STIT) to it, and then
when it cuts back out you are short on air. My car cycles a
lot at idle when the fans are not running. Trucks with a
mechanical fan, maybe don't do this; seems to be a limit
cycle on mine.