Engine likes running at <11:1 in PE mode
04-19-2012, 09:29 PM
#21
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Ur truely wasting ur time if not data logging. Recently pulled a lot of hair because while I thought the tune was calling for big numbers @ WOT, a scan showed timing pulled all the way back to 4 or 5 degrees! Would not have figured it out if I was depending on the ECM to provide the timing I asked for. Like all computers, it was doing what I told it....I just did not know what I was telling it. GMs settings and algorithms are VERY consertavtive. If Ur actual timing is not what you expected, check: Burst Knock settings (ECM anticipates knock even if your sensor is inop), Knock Retard Limits, Smoothing OFF, and ECT/IAT tables/modifiers. Also set all Torque Limiting settings to max values. My problem was Torque Limiting and ECT modifiers. Finally, the ECM ANTICIPATES where spark is going (just like it learns fuel trim numbers). So you have to look to the extreme edges of your High Octane Spark MAP 'cause the ECM will average spark settings from several cells away. The ECM does not like maps with steep slopes on the curve.
I've been down the burst knock road before, we took care of it while setting up the tune for this car.
The rest, I'll have to check once I have my own software.
The tuner's comment was 'Your chart does not have the dip/dips attributed with knock typically'
The 13:1 run you see above was made with injector 3,4,7 and 8 assigned the wrong banks (has to do with the LT1 engine / LS1 ccomputer combo),
which made the tailpipe show 13:1 but O2s were telling me that Bank 1 was crazy lean while Bank 2 was extremely rich.
When we fixed it, both sides evened out but made considerably less power until we richened it up.
I don't have it or the cable/software needed to download it.
Although, it's probably time that I just buy myself a copy of HPT and start working on this myself.
I just didn't want an engine I spent this kind of money on to be my learning mule.
Last edited by James Montigny; 04-19-2012 at 09:39 PM.
04-26-2012, 05:20 PM
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Ok, now I am even more confused.
I went back and looked at the runfiles from the dyno session and found one where we put down 385 at 13:1.
That was before we started messing with the timing.
I wonder if we didn't have it at 36* the whole time.
Based on what BLK02WS6 was saying, that is backwards.
We should have been using a more conservative value.
This doesn't explain why I am so low on power, but it does make the rich condition
seem like is is a symptom of poor tuning decisions rather than a mechanical condition.
I went back and looked at the runfiles from the dyno session and found one where we put down 385 at 13:1.
That was before we started messing with the timing.
I wonder if we didn't have it at 36* the whole time.
Based on what BLK02WS6 was saying, that is backwards.
We should have been using a more conservative value.
This doesn't explain why I am so low on power, but it does make the rich condition
seem like is is a symptom of poor tuning decisions rather than a mechanical condition.
His response was that althought he is not a tuner by trade;
"In open loop (and power enrichment) the injector bank assignments are irrelevant (remember “injector bank assignments” are not “firing order”). Again, so many variables, but with the wrong bank assignments, and before wide open throttle for your dyno pull, the fuel trims will be all over the place. Transition into wide open throttle and fueling is already off."
I'm missing something here somewhere....
I just ordered my own copy of HPT Pro, let's see it I can sort this out.
Last edited by James Montigny; 04-26-2012 at 05:36 PM.
06-16-2013, 03:20 PM
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So, another year has slipped by. I've messed with the car a few times hoping to find the issue, but no luck. I have a laptop with HPT, I'm trying to figure out how to log so it can be of more use to me.
Any advice on where to begin would be appreciated.
Any advice on where to begin would be appreciated.
06-17-2013, 12:44 PM
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Your peak HP comes pretty early, and if you keep
keying on that lower RPM range, rich may indeed be
where it's at.
But HP ought to come from RPM, if your airflow can
support it. At higher RPM though, a very rich mixture
may not burn quick enough and you blow power out
into the pipe instead. One size may not fit all. You
may want leaner at higher RPMs and fat at peak
torque & below. And of course positioning your spark
to suit, meanwhile.
keying on that lower RPM range, rich may indeed be
where it's at.
But HP ought to come from RPM, if your airflow can
support it. At higher RPM though, a very rich mixture
may not burn quick enough and you blow power out
into the pipe instead. One size may not fit all. You
may want leaner at higher RPMs and fat at peak
torque & below. And of course positioning your spark
to suit, meanwhile.
06-17-2013, 07:59 PM
#28
Do you guys, that are telling James that 36 degrees is too much timing, tune a lot of fast LT1s?
I would check the timing with a light to verify the reluctor is correct, and the timing is what you think it is. An NA LT1 that appears to like ~30 degrees has an actual timing issue.
36 to 38 is correct. I have tuned several with DFI, Holley, BS3, and FAST using a crank trigger and verified with a TDC pointer and degrees dampener. 34 degrees is the least I have seen one like, and that was at 12-1 on pump gas.
I would check the timing with a light to verify the reluctor is correct, and the timing is what you think it is. An NA LT1 that appears to like ~30 degrees has an actual timing issue.
36 to 38 is correct. I have tuned several with DFI, Holley, BS3, and FAST using a crank trigger and verified with a TDC pointer and degrees dampener. 34 degrees is the least I have seen one like, and that was at 12-1 on pump gas.
Last edited by Ed Wright; 06-17-2013 at 08:11 PM.
06-19-2013, 08:55 PM
#30
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Quick cruise around the block. Log and tune attached.
O2s seem happy
Runs a little warm while driving, doesn't want to cool down until I put the charger on it. (Yes, I run an EWP)
Since it also doesn't like to start without being charged, I suspect that there's an issue in the charging system.
Replacing the alt didn't help, nor did trying a different battery.
Fans work fine, I run a stock-style Tstat and fans are set to come on accordingly.
I need to go back to the 160 someday, but it's not at the top of my priority list. I took it out when I was troubleshooting.
O2s seem happy
Runs a little warm while driving, doesn't want to cool down until I put the charger on it. (Yes, I run an EWP)
Since it also doesn't like to start without being charged, I suspect that there's an issue in the charging system.
Replacing the alt didn't help, nor did trying a different battery.
Fans work fine, I run a stock-style Tstat and fans are set to come on accordingly.
I need to go back to the 160 someday, but it's not at the top of my priority list. I took it out when I was troubleshooting.
06-20-2013, 11:51 AM
#31
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If system voltage is lower than usual (i.e. than when-
tuned) then you're depending on some obscure things
like the injector response vs voltage to keep the main
delivery as-expected; odds are, though, that nobody
has touched this stuff and the info to do it right, can't
be had.
55PSI is a bit low relative to stock LS1 fuel systems
and needs to be factored into the IFR table (there are
spreadsheets for this). Not real clean to do because
at WOT, fuel fade follows RPM rather than the MAP
(BARO-MAP) dependence of the IFR table. So you
have to fake intention, rather than model reality.
If you can't get heat out, that's probably not the 'stat.
Unless it's totally failing to open. And a radiator full of
debris ought to only require more time to cool down
once load is removed, not fail to come down at all.
What about the possibility of steam pockets in the
heads, which once formed can persist indefinitely?
tuned) then you're depending on some obscure things
like the injector response vs voltage to keep the main
delivery as-expected; odds are, though, that nobody
has touched this stuff and the info to do it right, can't
be had.
55PSI is a bit low relative to stock LS1 fuel systems
and needs to be factored into the IFR table (there are
spreadsheets for this). Not real clean to do because
at WOT, fuel fade follows RPM rather than the MAP
(BARO-MAP) dependence of the IFR table. So you
have to fake intention, rather than model reality.
If you can't get heat out, that's probably not the 'stat.
Unless it's totally failing to open. And a radiator full of
debris ought to only require more time to cool down
once load is removed, not fail to come down at all.
What about the possibility of steam pockets in the
heads, which once formed can persist indefinitely?
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