KR Problem & Timing?
02-29-2004, 11:52 PM
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KR Problem & Timing? I really need some help with a stubborn KR problem that I can't seem to get rid of and have a couple of questions...
Here's the rundown:
- 2000 C5 with A4 tranny
- 382 stroker
- mild cam 230/.570 114 single pattern
- 10.8:1 compression
- MAF is stock & descreened
- NGK TR6 plugs
- Lucas/Delphi 36lbs injectors
- running on crappy 91 octane CA gas...
- WOT timing set to 27* and am not experiencing any knock under WOT
- The remainder of the timing table has been reduced 3-4* from stock
and from what I'm seeing I may need to go another 3-5* in these problem areas.
LTFTs -4.1 in load FTCs 6-14
LTFTs 0 at WOT
WOT O2s .895
My problem is in the lower to mid RPM ranges (1200-3600 RPM) from .08gms/cyl to .56gms/cyl, I'm getting alot of knock.
Its not false knock and detonation is occassionally audible especially under agressive tip-in.
No KR occurs under WOT.
My question is this: Is it common to have to remove alot of timing from the lower RPM and gms/cyl ranges???
If not, any suggestions on how to remedy this KR or places to look?
Here's the rundown:
- 2000 C5 with A4 tranny
- 382 stroker
- mild cam 230/.570 114 single pattern
- 10.8:1 compression
- MAF is stock & descreened
- NGK TR6 plugs
- Lucas/Delphi 36lbs injectors
- running on crappy 91 octane CA gas...
- WOT timing set to 27* and am not experiencing any knock under WOT
- The remainder of the timing table has been reduced 3-4* from stock
and from what I'm seeing I may need to go another 3-5* in these problem areas.
LTFTs -4.1 in load FTCs 6-14
LTFTs 0 at WOT
WOT O2s .895
My problem is in the lower to mid RPM ranges (1200-3600 RPM) from .08gms/cyl to .56gms/cyl, I'm getting alot of knock.
Its not false knock and detonation is occassionally audible especially under agressive tip-in.
No KR occurs under WOT.
My question is this: Is it common to have to remove alot of timing from the lower RPM and gms/cyl ranges???
If not, any suggestions on how to remedy this KR or places to look?
03-01-2004, 02:19 PM
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I'm assuming that you already have programming to account for the stroker/cam setup.
It may not be purely a timing problem. Depending on what has been done, you might need to tweak your VE table to take care of the part throttle stumbles. For my personal tune, I have found that there are certain "jumps" in the VE table around 50-60 MAP that are important for smooth part throttle acceleration.
It may not be purely a timing problem. Depending on what has been done, you might need to tweak your VE table to take care of the part throttle stumbles. For my personal tune, I have found that there are certain "jumps" in the VE table around 50-60 MAP that are important for smooth part throttle acceleration.
03-01-2004, 03:26 PM
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Well, we took care of the other tuning areas for the stroker/cam...
We had to make some significant canges in the VE table and over the course of a few weeks ended up doing a average/calculated VE table. - I may try to tweak this further...
My other thought was in regards to injectors - I'm still using the stock offsets and am wondering if these things are firing fast/long enough even though LTRMs appear OK...
We had to make some significant canges in the VE table and over the course of a few weeks ended up doing a average/calculated VE table. - I may try to tweak this further...
My other thought was in regards to injectors - I'm still using the stock offsets and am wondering if these things are firing fast/long enough even though LTRMs appear OK...
03-02-2004, 04:57 PM
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The injector offset table is supposed to be the time lag between commanded open and the injector actually opening enough to begin flowing fuel. I would think that this value is specific to the injectors, not the PCM.
I have stock injectors and have not messed with this table myself. I would think that different brands/models of injectors would have different offsets. The reasons I said that correct offset is important are 1) see above explanation of injector offset, and 2) BigTex has been trying to get a new (correct) table for his larger injectors, and I respect his opinion.
cheers
I have stock injectors and have not messed with this table myself. I would think that different brands/models of injectors would have different offsets. The reasons I said that correct offset is important are 1) see above explanation of injector offset, and 2) BigTex has been trying to get a new (correct) table for his larger injectors, and I respect his opinion.
cheers
03-03-2004, 12:16 AM
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I tend to agree.
While I have gotten and understand the comments from racetronix & mototron, I'm not buying it.
Prior to moving to my current setup I was running the SVO 30s.
the tune was OK with the stock offset, part throttle was greatly improved and LTRMs were not so erradic with the updated table and that table was a drastic change from stock.
Unfortunately I haven't been able to locate a table for the Lucas 36s.
Its my understanding that they fire faster than the Bosch/SVO & even stock but I'm not sure and don't have a definitive answer.
Based on where I'm seeing my issues although slim it maybe a possibility.
Currently I'm richening up even further, working the VE table and reducing timing further to eliminate my problem, but, I would be curious if and accurate offset table might produce more reliable results.
While I have gotten and understand the comments from racetronix & mototron, I'm not buying it.
Prior to moving to my current setup I was running the SVO 30s.
the tune was OK with the stock offset, part throttle was greatly improved and LTRMs were not so erradic with the updated table and that table was a drastic change from stock.
Unfortunately I haven't been able to locate a table for the Lucas 36s.
Its my understanding that they fire faster than the Bosch/SVO & even stock but I'm not sure and don't have a definitive answer.
Based on where I'm seeing my issues although slim it maybe a possibility.
Currently I'm richening up even further, working the VE table and reducing timing further to eliminate my problem, but, I would be curious if and accurate offset table might produce more reliable results.
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05-30-2004, 02:52 PM
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FRP Tech, so did you find the cause of your pinging problem. I am asking because I have exactly the same thing with my 382 stroker c5 now. No pinging at WOT but severe pinging (even 12 degrees of KR) at 0.2-0.6 g/cyl 1000-3000 rpm. But I do suspect it is false pinging as I tried to lower the spark advance values in the table by 12 in this area and I still got the same amount of pinging... 
05-30-2004, 03:21 PM
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Have you removed EGR? The area where you
seem to be having trouble, is where EGR
"should" be diluting the charge (as far as
the PCM believes) and based on this the
spark might be well more advanced, stock
tune, than a modded one with a lungfull of
clean air & crappy gas can take without
pinging. If you see no sign of misfueling I
would just keep taking out spark, surgically,
trying to keep the rollon / rolloff semi-smooth
as you go across & down the table.
seem to be having trouble, is where EGR
"should" be diluting the charge (as far as
the PCM believes) and based on this the
spark might be well more advanced, stock
tune, than a modded one with a lungfull of
clean air & crappy gas can take without
pinging. If you see no sign of misfueling I
would just keep taking out spark, surgically,
trying to keep the rollon / rolloff semi-smooth
as you go across & down the table.
05-30-2004, 04:51 PM
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marcink
As it turns out my issues were MAF related.
Went through several MAFs(portted, 85mm, descreened, screened & stock) before finally getting a brand new AC Delco unit which solved my KR problems...-Best $150 Ive spent in awhile
Dont get me wrong - we still did a fair amount of tuning i.e. IFR, timing, VE & even TQ and tranny. But, bottom line is it was the MAF and even my original stock MAF was apparently no good...
As it turns out my issues were MAF related.
Went through several MAFs(portted, 85mm, descreened, screened & stock) before finally getting a brand new AC Delco unit which solved my KR problems...-Best $150 Ive spent in awhile
Dont get me wrong - we still did a fair amount of tuning i.e. IFR, timing, VE & even TQ and tranny. But, bottom line is it was the MAF and even my original stock MAF was apparently no good...
05-31-2004, 12:11 AM
#12
Originally Posted by FRPTech
marcink
As it turns out my issues were MAF related.
Went through several MAFs(portted, 85mm, descreened, screened & stock) before finally getting a brand new AC Delco unit which solved my KR problems...-Best $150 Ive spent in awhile
Dont get me wrong - we still did a fair amount of tuning i.e. IFR, timing, VE & even TQ and tranny. But, bottom line is it was the MAF and even my original stock MAF was apparently no good...
As it turns out my issues were MAF related.
Went through several MAFs(portted, 85mm, descreened, screened & stock) before finally getting a brand new AC Delco unit which solved my KR problems...-Best $150 Ive spent in awhile
Dont get me wrong - we still did a fair amount of tuning i.e. IFR, timing, VE & even TQ and tranny. But, bottom line is it was the MAF and even my original stock MAF was apparently no good...
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05-31-2004, 01:36 AM
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Originally Posted by FRPTech
marcink
As it turns out my issues were MAF related.
Went through several MAFs(portted, 85mm, descreened, screened & stock) before finally getting a brand new AC Delco unit which solved my KR problems...-Best $150 Ive spent in awhile
Dont get me wrong - we still did a fair amount of tuning i.e. IFR, timing, VE & even TQ and tranny. But, bottom line is it was the MAF and even my original stock MAF was apparently no good...
As it turns out my issues were MAF related.
Went through several MAFs(portted, 85mm, descreened, screened & stock) before finally getting a brand new AC Delco unit which solved my KR problems...-Best $150 Ive spent in awhile
Dont get me wrong - we still did a fair amount of tuning i.e. IFR, timing, VE & even TQ and tranny. But, bottom line is it was the MAF and even my original stock MAF was apparently no good...
06-06-2004, 11:04 PM
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Originally Posted by jimmyblue
Have you removed EGR? The area where you
seem to be having trouble, is where EGR
"should" be diluting the charge (as far as
the PCM believes) and based on this the
spark might be well more advanced, stock
tune, than a modded one with a lungfull of
clean air & crappy gas can take without
pinging. If you see no sign of misfueling I
would just keep taking out spark, surgically,
trying to keep the rollon / rolloff semi-smooth
as you go across & down the table.
seem to be having trouble, is where EGR
"should" be diluting the charge (as far as
the PCM believes) and based on this the
spark might be well more advanced, stock
tune, than a modded one with a lungfull of
clean air & crappy gas can take without
pinging. If you see no sign of misfueling I
would just keep taking out spark, surgically,
trying to keep the rollon / rolloff semi-smooth
as you go across & down the table.
Where is the area EGR would be diluting the charge? How can you tell if the removal of EGR is what is helping to cause KR?
What should be logged?
What should be changed?
07-30-2004, 12:50 AM
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Originally Posted by Cheatin' Chad
Where is the area EGR would be diluting the charge? How can you tell if the removal of EGR is what is helping to cause KR?
What should be logged?
What should be changed?
What should be logged?
What should be changed?
have you found this information yet? I am also having issues with KR while accellerating in part throttle. This is between 1.2x.28/1.2x.48 - 1.6x.28/1.6x.48. Is this where !EGR would cause a decrease?
