Help with fine tuning a 402
10-29-2007, 04:30 PM
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Help with fine tuning a 402 Had some good feedback via here and the HPTuners forum, so we'll continue along my quest to tune 
Few questions:
1) How clean can you get the VE? I have put over 200 miles on the car in OLSD, making adjustments after getting nice, full AFR Error histograms, cell counts set to 50. Low RPM cruising is killing me as I try to get it consistent. Same weather, same amount of data collected, I can't get the histogram to keep everything under 5%. For the most part it is, but I still get the occasional cells with 8-9% error.
Am I at the point that I need to quit fudging with it?
2) Calibrating the MAF - On the last 3 or 4 drives I plugged the MAF back in and started logging it's values in order to get the corrections on the appropriate histogram. I started out with the table from a 6.0L truck and have made a couple of adjustments, but it has been fairly accurate (3% or less) across the board.
How accurate do I strive to be here? If I am at the point where I need to quit adjusting the VE, should I be reenabling closed loop and start watching my fuel trims?
3) Returning to idle - This is really confusing me at this point. Working with Russ's input and then slowly moving things around I have gotten it to return to idle smoothly 95% of the time. The other 5% I can't figure out - 2% of the time the idle just falls off and dies, the other 2-3% of the time it hangs up about 300rpms above idle. There are a few times where it falls to idle nicely, but only for a split second and it jumps up 100rpms, then settles back down (Can see this in the log almost every time I come to a stop). If the car does end up dying, the idle hangs 3-400rpms above idle 100% of the time until I reload a tune. (Any time it hangs up high, it does so until I come to a complete stop for a few seconds, then it falls to idle speed).
I'm at a loss here, and can understand why I keep reading that idle is one of the hardest things to get locked in. I notice that the advance locks in solid when coming down to idle (locked exactly where the idle spark advance tables command it to be). Are there any modifiers to that table? It may be that I need to start massaging the idle timings a bit at this point...
4) Slight bucking/surging/cruise control - Approximately between 1600-2000rpms, she does not want to be smooth. This really sucks when coasting around corners, highway cruising, etc. This may have some association with the idle questions above considering it is at such low rpms...
Would the cause of this be related to timing? Fuel? Air? All of the above?
5) Knock retard - I have seen ZERO. I have also heard zero, not that I want to. My maybe flawed searching doesn't pull up much of anything recent (bigger discussions are around 2 years old). After reading about various issues here regarding an LS2 in an LS1 vehicle, what do I need to do? Something I can do to make sure the sensors are working without risking damage?
Specs:
2002 SS with a new 402 LS2
11.5:1 compression ratio
244/250...114 LSA cam
AFR 225 62cc heads
Kook's headers
FAST 90/90 Intake/TB
SLP 85mm MAF
42lb Racetronix injectors (48.83lb/hr @ 58psi)
255lph fuel pump
Manual transmission
Latest tune and latest log are below. You can see towards the end of the log when it dies coming down to idle...
Thanks for any advice.
Few questions:
1) How clean can you get the VE? I have put over 200 miles on the car in OLSD, making adjustments after getting nice, full AFR Error histograms, cell counts set to 50. Low RPM cruising is killing me as I try to get it consistent. Same weather, same amount of data collected, I can't get the histogram to keep everything under 5%. For the most part it is, but I still get the occasional cells with 8-9% error.
Am I at the point that I need to quit fudging with it?
2) Calibrating the MAF - On the last 3 or 4 drives I plugged the MAF back in and started logging it's values in order to get the corrections on the appropriate histogram. I started out with the table from a 6.0L truck and have made a couple of adjustments, but it has been fairly accurate (3% or less) across the board.
How accurate do I strive to be here? If I am at the point where I need to quit adjusting the VE, should I be reenabling closed loop and start watching my fuel trims?
3) Returning to idle - This is really confusing me at this point. Working with Russ's input and then slowly moving things around I have gotten it to return to idle smoothly 95% of the time. The other 5% I can't figure out - 2% of the time the idle just falls off and dies, the other 2-3% of the time it hangs up about 300rpms above idle. There are a few times where it falls to idle nicely, but only for a split second and it jumps up 100rpms, then settles back down (Can see this in the log almost every time I come to a stop). If the car does end up dying, the idle hangs 3-400rpms above idle 100% of the time until I reload a tune. (Any time it hangs up high, it does so until I come to a complete stop for a few seconds, then it falls to idle speed).
I'm at a loss here, and can understand why I keep reading that idle is one of the hardest things to get locked in. I notice that the advance locks in solid when coming down to idle (locked exactly where the idle spark advance tables command it to be). Are there any modifiers to that table? It may be that I need to start massaging the idle timings a bit at this point...
4) Slight bucking/surging/cruise control - Approximately between 1600-2000rpms, she does not want to be smooth. This really sucks when coasting around corners, highway cruising, etc. This may have some association with the idle questions above considering it is at such low rpms...
Would the cause of this be related to timing? Fuel? Air? All of the above?
5) Knock retard - I have seen ZERO. I have also heard zero, not that I want to. My maybe flawed searching doesn't pull up much of anything recent (bigger discussions are around 2 years old). After reading about various issues here regarding an LS2 in an LS1 vehicle, what do I need to do? Something I can do to make sure the sensors are working without risking damage?
Specs:
2002 SS with a new 402 LS2
11.5:1 compression ratio
244/250...114 LSA cam
AFR 225 62cc heads
Kook's headers
FAST 90/90 Intake/TB
SLP 85mm MAF
42lb Racetronix injectors (48.83lb/hr @ 58psi)
255lph fuel pump
Manual transmission
Latest tune and latest log are below. You can see towards the end of the log when it dies coming down to idle...
Thanks for any advice.
10-29-2007, 09:03 PM
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Update from drives tonight...
First log is driving to a basketball game, second log coming home. Resulting tune is attached...
Follows along the same things as above - VE keeps changing, I get seemingly random stall outs, sometimes it idles down fine, sometimes it hangs at 1500rpms...
And, for some reason 3 of the 4 fuel trims shot to -100% on the drive home - no idea why considering they are disabled...
Thoughts?
First log is driving to a basketball game, second log coming home. Resulting tune is attached...
Follows along the same things as above - VE keeps changing, I get seemingly random stall outs, sometimes it idles down fine, sometimes it hangs at 1500rpms...
And, for some reason 3 of the 4 fuel trims shot to -100% on the drive home - no idea why considering they are disabled...
Thoughts?
10-29-2007, 10:09 PM
#3
Just some tips
1. Once you get it close, begin pasting 1/2% error
2. If you are within 3% with it enabled, that is damn close. I usually get it to within 3% and fudge it a bit positive so that trims stay slightly negative.
3. Don't forget about your other airflow tables like the throttle follower, it's delay and decay values, and the throttle cracker table especially. These have lots to do with return-to-idle transitions
4. Cam surge comes from a number of things. If your AFR is fairly close, the next two items to look at are timing at cruise and the IAC's offset. Frequently I end up with "cruise pockets" on the map of timing that may at first glance seem very low. Secondly, if you feel it just as you let off, it is likely an airflow issue. Since you have the TB opened up and the RAF raised, your airflow is a bit higher than expected. In your IAC counts vs. effective area table, try copying the whole table and then pasting it about 5 cells to the right and zero out those 5 cells that you jumped over to paste. Excessive throttle follower airflow can cause this too.
1. Once you get it close, begin pasting 1/2% error
2. If you are within 3% with it enabled, that is damn close. I usually get it to within 3% and fudge it a bit positive so that trims stay slightly negative.
3. Don't forget about your other airflow tables like the throttle follower, it's delay and decay values, and the throttle cracker table especially. These have lots to do with return-to-idle transitions
4. Cam surge comes from a number of things. If your AFR is fairly close, the next two items to look at are timing at cruise and the IAC's offset. Frequently I end up with "cruise pockets" on the map of timing that may at first glance seem very low. Secondly, if you feel it just as you let off, it is likely an airflow issue. Since you have the TB opened up and the RAF raised, your airflow is a bit higher than expected. In your IAC counts vs. effective area table, try copying the whole table and then pasting it about 5 cells to the right and zero out those 5 cells that you jumped over to paste. Excessive throttle follower airflow can cause this too.
Last edited by Frost; 10-30-2007 at 12:55 AM.
10-29-2007, 10:47 PM
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Thanks for the input - all stuff I should know since I've heard by now, but for some reason I don't pull it all back out 
I think at this point I need to start working on the timing tables. I figured out on the drive home what causes it to die, but I don't know why. When it dies, the advance is staying in the main spark tables, and not switching over to the idle tables. I'm not certain what causes it to use either at seemingly the same times (has to be some parameter I'm missing). When it dies, the main tables command 16-18degrees spark, and it just runs out. Idle tables at the same point command 38+ and it smooths down nicely. I presume getting those to closer transition would definitely help out there...
One day I'll get close I suppose
I think at this point I need to start working on the timing tables. I figured out on the drive home what causes it to die, but I don't know why. When it dies, the advance is staying in the main spark tables, and not switching over to the idle tables. I'm not certain what causes it to use either at seemingly the same times (has to be some parameter I'm missing). When it dies, the main tables command 16-18degrees spark, and it just runs out. Idle tables at the same point command 38+ and it smooths down nicely. I presume getting those to closer transition would definitely help out there...
One day I'll get close I suppose
Last edited by LankyLS-1; 10-29-2007 at 10:53 PM.
10-30-2007, 11:13 AM
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Makes sense - question though... Why wouldn't it exhibit the same characteristics at all times? In other words, why wouldn't it fall to that 16-18 degrees in the main table every time I let off and coasted in neutral? Looking at the logs it does not appear consistent as to which it is commanding - hence my thought about some parameter that I'm missing.
Clear as mud
Clear as mud