need tips on spark tuning...
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From: stop the fun suckers
need tips on spark tuning...
Now that I;ve got the fuel tables pretty much in line I', moving over to adjusting the spark tables... I've noticed at a rolling idle (car in drive, foot off brake, without pressing the accelorator pedal down - the car begins to move like most cars do... however, it surges.. or should i say rolls.. the rpms go up than down then up then down.. only about a few 100 rpm or so.. but enough that it effects the speed of the moving idle..
I'm not an expert, but it seems to me that would indicate to much timing in this location of the spark table.... also at crusing speeds i think i feel a itty-bitty surge... could that be because of the EGR? I still have the EGR active even though I have a cam with a much larger overlap than stock.. so I try turning the EGR off to try and eliminate this? Also, I'll post my spark table as soon as I convert it to a postable file..
thanks!
*edit*
Here are the spark tables I'm running... see sig for cam specs! (CLICK TO ENLARGE)
Spark. Vs RPM Vs Load (0-4000RPM)
Spark Vs RPM Vs Load (4000-7500RPM)
Coolant Temp vs. Spark
what am I doing wrong?
[Modified by BluByU, 8:10 AM 1/9/2004]
[Modified by BluByU, 8:10 AM 1/9/2004]
I'm not an expert, but it seems to me that would indicate to much timing in this location of the spark table.... also at crusing speeds i think i feel a itty-bitty surge... could that be because of the EGR? I still have the EGR active even though I have a cam with a much larger overlap than stock.. so I try turning the EGR off to try and eliminate this? Also, I'll post my spark table as soon as I convert it to a postable file..
thanks!
*edit*
Here are the spark tables I'm running... see sig for cam specs! (CLICK TO ENLARGE)
Spark. Vs RPM Vs Load (0-4000RPM)
Spark Vs RPM Vs Load (4000-7500RPM)
Coolant Temp vs. Spark
what am I doing wrong?
[Modified by BluByU, 8:10 AM 1/9/2004]
[Modified by BluByU, 8:10 AM 1/9/2004]
Race Director
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From: Texas
Re: need tips on spark tuning... (BluByU)
I've seen it fixed both ways. Some like more timing, some less. I'd pull out 2* at a time. If it's not better by the time you pull 6*, try 2* more advance. Be sure to smooth the timing maps...don't have a value at 28* and then the next cell be 22* where you adjusted and then back to 28*.
Did you put in a different torque converter? That cam is real close to the LT4 HOT Cam. I think most automatic guys run a 2800rpm stall to eliminate the surging.
Did you put in a different torque converter? That cam is real close to the LT4 HOT Cam. I think most automatic guys run a 2800rpm stall to eliminate the surging.
Thread Starter
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From: stop the fun suckers
Re: need tips on spark tuning... (96GS#007)
ohhhh.... I have a stock stall converter.. and yes that cam is VERY close to the hot cam.. just a tad bit more lift and tad less duration.. just the way I like it for the street.. steep ramps! BTW: the cam specs are with 1.5rr not 1.66rr's like the hot cam is advertised..
When I begin pulling out timing to I start at the place i noticed the rolling idle surge? (700-900 rpm, 45-60MAP) and work from there? 2* at a time like you said? Also, do you see anything espeically out of the ordinary about my timing tables?
When I begin pulling out timing to I start at the place i noticed the rolling idle surge? (700-900 rpm, 45-60MAP) and work from there? 2* at a time like you said? Also, do you see anything espeically out of the ordinary about my timing tables?
Thread Starter
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From: stop the fun suckers
Re: need tips on spark tuning... (BluByU)
Also what effect could the "TCC Lock/Unlock %TPS vs. Speed" tbales have on this condition?? (Both low and high gears)
*edit *
another TCC question..
why would you want the TCC to unlock at a lower TPS% than the factory settings at a given speed?
[Modified by BluByU, 1:00 PM 1/9/2004]
*edit *
another TCC question..
why would you want the TCC to unlock at a lower TPS% than the factory settings at a given speed?
[Modified by BluByU, 1:00 PM 1/9/2004]
Melting Slicks
Joined: May 1999
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From: Sarasota FL
Re: need tips on spark tuning... (BluByU)
What car?
I have a stock converter on a 218/224 114 cam.
Idle areas take a delicate balance of fuel, spark, commanded idle, throttle stop adjustment, and sufficient IAC headroom.
My car wanted more timing.
Drive to Sarasota and I'll try to help.
I have a stock converter on a 218/224 114 cam.
Idle areas take a delicate balance of fuel, spark, commanded idle, throttle stop adjustment, and sufficient IAC headroom.
My car wanted more timing.
Drive to Sarasota and I'll try to help.
Le Mans Master
Joined: Jan 2003
Posts: 8,596
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From: Portland Oregon
Re: need tips on spark tuning... (BluByU)
What is your fuel trims looking like in the areas where the surging is taking place? I would be looking there first before messing with the timing maps. Just my two bits worth....:) Has anything else been done? If your car has a MAF sensor did you gut it?
If you are using DataMaster send me a datalog file and advise of where the surging is taking place and I will take a look and see for you :)
[Modified by tjwong, 4:18 PM 1/9/2004]
If you are using DataMaster send me a datalog file and advise of where the surging is taking place and I will take a look and see for you :)
[Modified by tjwong, 4:18 PM 1/9/2004]
Thread Starter
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From: stop the fun suckers
Re: need tips on spark tuning... (tjwong)
I'll record some fuel trim values for the area in querstion and post them here... I just put in a new chip and I disabled the EGR (coolent temp threshold at 240*F) I think that'll take care fo the 45 or so surge.. now its just the surge at between fuel cell 16 and 18... I know cell 16 is on the main fuel map.. what fuel map does cell 18 use?
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From: Texas
Re: need tips on spark tuning... (BluByU)
Once your fueling is ok you need to log timing advance vs load and speed to determine specifically where the surge is occuring. After you know that, you can then go into that area of the timing map and massage the values. I try not to have any cells more 2* apart, so if you're having to make large changes you could affect multiple blocks in the timing map.
Nothing jumps out at me as being out of the ordinary with your timing maps. Just needs a little fine tuning :)
Nothing jumps out at me as being out of the ordinary with your timing maps. Just needs a little fine tuning :)
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Thread Starter
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From: stop the fun suckers
Re: need tips on spark tuning... (96GS#007)
don't they always... :lol:
When tuning a spark map for a modifyed engine where is what is a good way to start (or best method to proceed). Do you just assume you can run more spark if you assume you will always run 93 octane and just bump the whole timing table up a certian % accross the whole board? Also, I noticed in my old PCMforless tuning that they drastically increased the low RPM spark advance.. is there some performance payoff in doing this? or does this jsut mask the idle for engines running bigger cams?
[Modified by BluByU, 6:18 AM 1/12/2004]
When tuning a spark map for a modifyed engine where is what is a good way to start (or best method to proceed). Do you just assume you can run more spark if you assume you will always run 93 octane and just bump the whole timing table up a certian % accross the whole board? Also, I noticed in my old PCMforless tuning that they drastically increased the low RPM spark advance.. is there some performance payoff in doing this? or does this jsut mask the idle for engines running bigger cams?
[Modified by BluByU, 6:18 AM 1/12/2004]
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From: Texas
Re: need tips on spark tuning... (BluByU)
More timing down low improves low end torque. More is better only to an extent however. Too much advance and you can burn valves.
I would not increase the whole map across the board. If you're running a modified version of an LT1 or LT4 timing map from GM, you should be pretty close other than high load/low rpm areas (which have always seemed a little conservative IMO) and where you have cam surge.
Light load areas of the timing maps really boil down to driveability characteristics. If the car drives fine, leave well enough alone. If it surges, fix those areas of the map. Once you're satisfied with the driveability, then it's time to tune WOT. To do that you need a dyno and wide-band O2 sensor. WOT tuning includes fueling changes to optimize the A/F ratio and timing changes. FWIW, I made more power with less timing than stock above 6000rpm.
Unfortunately it is a repetitive process.
I would not increase the whole map across the board. If you're running a modified version of an LT1 or LT4 timing map from GM, you should be pretty close other than high load/low rpm areas (which have always seemed a little conservative IMO) and where you have cam surge.
Light load areas of the timing maps really boil down to driveability characteristics. If the car drives fine, leave well enough alone. If it surges, fix those areas of the map. Once you're satisfied with the driveability, then it's time to tune WOT. To do that you need a dyno and wide-band O2 sensor. WOT tuning includes fueling changes to optimize the A/F ratio and timing changes. FWIW, I made more power with less timing than stock above 6000rpm.
Unfortunately it is a repetitive process.
Thread Starter
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From: stop the fun suckers
Re: need tips on spark tuning... (96GS#007)
If you're running a modified version of an LT1 or LT4 timing map from GM, you should be pretty close other than high load/low rpm areas (which have always seemed a little conservative IMO) and where you have cam surge.
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From: Texas
Re: need tips on spark tuning... (BluByU)
So its good to start with the stock spark advance map, correct? I was thinking since I am running 10.8:1 compression (the same as the LT4 is stock) and running a cam similar to a Hotcam; the stock LT4 spark map would be the best starting place.. correct? better than the stock LT1 map (which only had 10.4:1 pistons in it..
Thread Starter
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From: stop the fun suckers
Re: need tips on spark tuning... (BluByU)
does the increased displacment have any effect on the spark timing? i.e. the 383 vs. 350.. Similarly since I used the 5.7" connecting rods as opposed to the 6" connecting rods the piston stays at TDC less does that make it want more ignition?
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From: Texas
Re: need tips on spark tuning... (BluByU)
does the increased displacment have any effect on the spark timing? i.e. the 383 vs. 350.. Similarly since I used the 5.7" connecting rods as opposed to the 6" connecting rods the piston stays at TDC less does that make it want more ignition?
Thread Starter
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From: stop the fun suckers
Re: need tips on spark tuning... (96GS#007)
I loaded the LT4 spark table into a chip last night.. the car seems to be responding well to it this morning.. I noticed in the low RPM high load areas of my programming I was like 20* more advanced than the stock LT4 programming.. so I split the difference.. seems to likey..
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From: stop the fun suckers
Re: need tips on spark tuning... (96GS#007)
hmm.. I programmed in the GS tables.. the car runs about the same (event with tons less timing) but it still has a slight surge at cruise speeds.. be it 30mph or 65mph.. I thought it could be a leaking TB gasket since I reused it which adjusting the bypass hole.. so i installed a fresh one I had lying around the garage.. this solved nothing.. could this ever so slight surge be caused by the A/C compressor engaging and or the alternator?
I dropped quite a bit of timing (see below) with little effect to performance and or surging.. before that I had tried eliminating the EGR but that didnt help either...
here is the table which illustrates the difference between the GS table which i'm running now and my old table from PCMFORLESS..
values shown are how much less timing i'm running now in the indivated spark cell..
wtf :mad :confused:
I dropped quite a bit of timing (see below) with little effect to performance and or surging.. before that I had tried eliminating the EGR but that didnt help either...
here is the table which illustrates the difference between the GS table which i'm running now and my old table from PCMFORLESS..
values shown are how much less timing i'm running now in the indivated spark cell..
wtf :mad :confused:
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From: Texas
Re: need tips on spark tuning... (BluByU)
If you have the HVAC controls set to the AC function or "AUTO", it's not unusual to feel the compressor engaging and disengaging. I recall that the compressor cycling was a huge cause of warranty claims for surging thru the '96 model year.
I'm not sure of the specifics since I have a 6 speed, but....I've heard of people having similar issues like what you're describing due to the lock-up feature of the torque converter locking and unlocking.
Generally cam surge is in the off-idle to ~1600rpm range.
I'm not sure of the specifics since I have a 6 speed, but....I've heard of people having similar issues like what you're describing due to the lock-up feature of the torque converter locking and unlocking.
Generally cam surge is in the off-idle to ~1600rpm range.
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From: stop the fun suckers
Re: need tips on spark tuning... (96GS#007)
what would cause the converter to unlock and lock.. I think if it was in the programming I would have felt it when it was stock.. anyways.. I'll email you a datalog I took last night if you dont mind taking a peek at it..
*edit*
After looking at my datamaster logs I noticed there is something not right about the fuel trims.. I used to have the cruise trims dead on.. but now it seems the driver side of the engine is running quite lean.. almost a 10 count difference from the right fuel trims... conicnidently, This is the same side of the engine I have a ticking lifter.. I wonder if the lifter collapsed fully and isn't opening the valve enough.. also I suppose this could be cause by a accum leak and or a fuel injector problem.. looks like i'm whipping out the stehescope to check all the injectors are firing again.. intake is comming off tomorrow am so i can replace the lifter.. this should take care of any protential intake manifold leaks.. aggghh..
[Modified by BluByU, 7:28 AM 1/16/2004]
*edit*
After looking at my datamaster logs I noticed there is something not right about the fuel trims.. I used to have the cruise trims dead on.. but now it seems the driver side of the engine is running quite lean.. almost a 10 count difference from the right fuel trims... conicnidently, This is the same side of the engine I have a ticking lifter.. I wonder if the lifter collapsed fully and isn't opening the valve enough.. also I suppose this could be cause by a accum leak and or a fuel injector problem.. looks like i'm whipping out the stehescope to check all the injectors are firing again.. intake is comming off tomorrow am so i can replace the lifter.. this should take care of any protential intake manifold leaks.. aggghh..
[Modified by BluByU, 7:28 AM 1/16/2004]
