Am I asking too much of my tuner????
07-24-2009, 12:44 AM
#1
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Am I asking too much of my tuner???? I have a heavily modified 99 corvette. It’s been tuned so far by two different local tuners, but not satisfied with how it runs.... The cold start is bad, it hunts for idle all the time, stalls frequently, smells like fuel, and it feels lazy and just not crisp.... The motor alone dynoed at 621 crank hp at 6200rpm and 569 tq at 5000rpm ...
Do I have a bad combination? I'd like it to be crisp and clean without surging to find an idle and just run fairly smooth without stalling.... Are these issues just characteristics of having a big cam or can these be worked out? My cam is 242/251 650/650 114 lsa... I think this is a great cam for my 300 shot, but need it to be drivable around town NA…
THE QUESTION IS AS FOLLOWS: CAN THIS CAR BE TAMED TO DRIVE NICE ON THE STREET BUT STILL GOES 9s ON THE STRIP? AM I ASKING TOO MUCH? IiF NOT, ID LIKE TO HEAR SOME GREAT LS TUNER RECOMMENDATIONS… ANY SUGGESTIONS??? THE REST OF THE COMO IS BELLOW...
Forged 402 with a big cam and Trick Flo 235's - Dragon Slayer crank - JE Calico coated pistons - Tony Mamo ported Fast 92 intake and ported 92 throttle body with Nano assisted Pro Flow direct port Nitrous - dedicated fuel system -1 7/8 AR headers
Do I have a bad combination? I'd like it to be crisp and clean without surging to find an idle and just run fairly smooth without stalling.... Are these issues just characteristics of having a big cam or can these be worked out? My cam is 242/251 650/650 114 lsa... I think this is a great cam for my 300 shot, but need it to be drivable around town NA…
THE QUESTION IS AS FOLLOWS: CAN THIS CAR BE TAMED TO DRIVE NICE ON THE STREET BUT STILL GOES 9s ON THE STRIP? AM I ASKING TOO MUCH? IiF NOT, ID LIKE TO HEAR SOME GREAT LS TUNER RECOMMENDATIONS… ANY SUGGESTIONS??? THE REST OF THE COMO IS BELLOW...
Forged 402 with a big cam and Trick Flo 235's - Dragon Slayer crank - JE Calico coated pistons - Tony Mamo ported Fast 92 intake and ported 92 throttle body with Nano assisted Pro Flow direct port Nitrous - dedicated fuel system -1 7/8 AR headers
Last edited by stonabones; 07-24-2009 at 03:13 PM. Reason: errors
07-24-2009, 10:52 AM
#2
From my experience it is always best to use the tuner that made the combination...if you build your own combo and then bring it to someone to tune that is not familiar with it they will have a much harder time tuning it than if its something they build day in and day out.
I've heard of the best tuners getting stuck on combinations that people bring them so picking the best corvette tuner may not help you in the end other than to lighten your pockets further.
Just food for thought.
I've heard of the best tuners getting stuck on combinations that people bring them so picking the best corvette tuner may not help you in the end other than to lighten your pockets further.
Just food for thought.
07-24-2009, 11:47 AM
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The things you are talking about, are things that require a lot
of "seat time" to {log, understand, tweak, repeat...}, at least
for someone who's dealing with a one-off combo and doesn't
have a known-good-last-one to work from. Hell, I'm still in mine
every other week touching up stuff from a much milder cam
(& intake, other parts, yadda yadda).
You might consider seriously, taking the reins yourself. Because
time is money (his, yours) and the more of a perfectionist you
are, the less happy you are likely to be with a journeyman's
work, ever.
of "seat time" to {log, understand, tweak, repeat...}, at least
for someone who's dealing with a one-off combo and doesn't
have a known-good-last-one to work from. Hell, I'm still in mine
every other week touching up stuff from a much milder cam
(& intake, other parts, yadda yadda).
You might consider seriously, taking the reins yourself. Because
time is money (his, yours) and the more of a perfectionist you
are, the less happy you are likely to be with a journeyman's
work, ever.
07-24-2009, 12:13 PM
#4
I have a heavily modified 99 corvette. Its been tuned so far by two different local tuners, but not satisfied with how it runs.... The cold satart is bad, it hunts for idle all the time, stalls all the time, smells like feul, and it feels laxy and just not crisp.... The motor alone dynoed at 621 crank hp at 6200rpm and 569 tq at 5000rpm ...
Well if you are only pushing 6200 rpms it really shouldn't smell like fuel because I am assuming the cam isn't to big and stalling jsut shouldn't happen. A good tuner doesn't need alot of time to get it running decently.
Idle hunting is kind of strange too it shouldn't be doing that if the idle speed and fueling is set up correct. Cold start depends on how hard it starts.
It wont be perfect from them because they usually just do a wot tune but they should touch up idle and some part load stuff so that you have no stall. Alot of shops from my experince say they know how to tune but have no idea. i have seen so many cars that run and smell like crap that the shop says runs awesome.
Find a good shop and they will work with you its worth making the travel for someone who really knows their stuff. IT might take the every day person a while to fine tune his car but a shop where the tuner is tuning everday for years should pick up on things and know what to adjust immediately. You want a specialized shop that tunes mostly specifically your motor or series of motors.
Well if you are only pushing 6200 rpms it really shouldn't smell like fuel because I am assuming the cam isn't to big and stalling jsut shouldn't happen. A good tuner doesn't need alot of time to get it running decently.
Idle hunting is kind of strange too it shouldn't be doing that if the idle speed and fueling is set up correct. Cold start depends on how hard it starts.
It wont be perfect from them because they usually just do a wot tune but they should touch up idle and some part load stuff so that you have no stall. Alot of shops from my experince say they know how to tune but have no idea. i have seen so many cars that run and smell like crap that the shop says runs awesome.
Find a good shop and they will work with you its worth making the travel for someone who really knows their stuff. IT might take the every day person a while to fine tune his car but a shop where the tuner is tuning everday for years should pick up on things and know what to adjust immediately. You want a specialized shop that tunes mostly specifically your motor or series of motors.
07-24-2009, 03:22 PM
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Thanks for the comments... I am picky when it comes to how the car drives on the street... That's why the tuner had the car for 3 days to road tune it for drivability first. It hasn’t been tuned for WOT yet. We are dyno tuning on Friday to get some numbers. From what I understand the air flow coming into the MAF is turbulent? I have a Vararam going directly into the Ligenfelter 92 MAF then thru the smooth air bridge then into the ported 92 TB... We are now moving the MAF directly in front of the TB to see if this helps keep the AF from jumping into so many cells? Has anyone dealt with this in the past? Any thoughts?
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07-24-2009, 10:26 PM
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THE QUESTION IS AS FOLLOWS: CAN THIS CAR BE TAMED TO DRIVE NICE ON THE STREET BUT STILL GOES 9s ON THE STRIP? ...
AM I ASKING TOO MUCH? IiF NOT, ID LIKE TO HEAR SOME GREAT LS TUNER RECOMMENDATIONS… ANY SUGGESTIONS??? THE REST OF THE COMO IS BELLOW
07-24-2009, 10:28 PM
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That cam should be tuned in open loop speed density, or an open loop idle/closed loop hybrid tune.
07-25-2009, 02:26 AM
#11
I would go with frans no tuner is that competent without knowin his ****. Let me just say i have a 67 camaro ss with 650 hp. THe effer drives unbelievable with a demon carb. Crisp throttle response power to move at a grand plus with 256/262 at .05 and .625/626 lift I believe I would have to look to check and afr 210's on a 383 small block. I cannot even give it a third of the pedal in idle before its already at 5 grand. Its there before I can pull the pedal out thats how crisp it is.
If the carbed motor can respond like that with that big of a cam then a fuel injected can it just needs a tune. I agree with boosted they only focused on power no off throttle.\
I would personally do a maf tune on your car and disable closed loop. Open loop maf doesn't really mean anything if SD is enabled and wrong (open loop is set up to run rich from the factory to help light catalyst with the aid of AIR under first start up but also pulls of VE tables) and once the ecm realizes the engine is warm it goes into closed loop which pulls off ve (it learns fueling values for a 3d engine operation table) and oxygen sensors and tunes according to narrowband readings and learns long term fueling to where it switches which for narrow band is 14.7. So it will use these values and as long as it is not below its base learning to populate PE (power enrich). Basically the computer takes control of the tune on anything under full throttle and relearns pe curves above usually 60-70% throttle range. It doesn't relearn the complete curve only the starting point. SD disables maf.
If you have an open loop tune it runs completely off maf and disregards o2 sensor readings assuming SD is turned off which in older pcms is accomplished by disabling closed loop. That way under part throttle you can get lean cruise (normally enabled on close loop for fuel economy) and can tune your car to always run rich in under certain airflows or curises beccause it still enables you to do PE. Usually there is a way to enable enrich above rpm point and it will have a few points that you can pick afr at and it learns a curve for it. Or it will use load and dump fuel according to the table.
Open loop tunes without SD are way easier to tune because you do not have to test every point on the speed and load curve which can be hundreds of points because it is speed and load dependent for fueling only. Maf uses airflow based fueling and PE to adjust AFR's. It uses resistors that mesaure the voltage required to keep the maf sensor at a current tempature along with IAT data to correct the airflow reading. To determine the amount of fuel. Therefore once the car is tuned for an airflow it does not matter speed or load the ecu dumps the same amount of fuel making it easier to tune. Most production cars use this and speed density is back up except chrysler the still use speed density. It is important to keep air straight going through the maf sensor. And far enough from the tb that there is no way for reversion to affect it with a big cam. It also will need corrections if resonators are taken out because it creates more pressure waves within the intake system.
Sorry for the long reply but thats the complete explanation.
A couple of things were wrong like open and closed loop switched at the very beginning. NOT my whole post LOL
If the carbed motor can respond like that with that big of a cam then a fuel injected can it just needs a tune. I agree with boosted they only focused on power no off throttle.\
I would personally do a maf tune on your car and disable closed loop. Open loop maf doesn't really mean anything if SD is enabled and wrong (open loop is set up to run rich from the factory to help light catalyst with the aid of AIR under first start up but also pulls of VE tables) and once the ecm realizes the engine is warm it goes into closed loop which pulls off ve (it learns fueling values for a 3d engine operation table) and oxygen sensors and tunes according to narrowband readings and learns long term fueling to where it switches which for narrow band is 14.7. So it will use these values and as long as it is not below its base learning to populate PE (power enrich). Basically the computer takes control of the tune on anything under full throttle and relearns pe curves above usually 60-70% throttle range. It doesn't relearn the complete curve only the starting point. SD disables maf.
If you have an open loop tune it runs completely off maf and disregards o2 sensor readings assuming SD is turned off which in older pcms is accomplished by disabling closed loop. That way under part throttle you can get lean cruise (normally enabled on close loop for fuel economy) and can tune your car to always run rich in under certain airflows or curises beccause it still enables you to do PE. Usually there is a way to enable enrich above rpm point and it will have a few points that you can pick afr at and it learns a curve for it. Or it will use load and dump fuel according to the table.
Open loop tunes without SD are way easier to tune because you do not have to test every point on the speed and load curve which can be hundreds of points because it is speed and load dependent for fueling only. Maf uses airflow based fueling and PE to adjust AFR's. It uses resistors that mesaure the voltage required to keep the maf sensor at a current tempature along with IAT data to correct the airflow reading. To determine the amount of fuel. Therefore once the car is tuned for an airflow it does not matter speed or load the ecu dumps the same amount of fuel making it easier to tune. Most production cars use this and speed density is back up except chrysler the still use speed density. It is important to keep air straight going through the maf sensor. And far enough from the tb that there is no way for reversion to affect it with a big cam. It also will need corrections if resonators are taken out because it creates more pressure waves within the intake system.
Sorry for the long reply but thats the complete explanation.
A couple of things were wrong like open and closed loop switched at the very beginning. NOT my whole post LOL
Last edited by Radcannon; 07-25-2009 at 11:20 AM.
07-25-2009, 06:19 AM
#12
I would personally do a maf tune on your car and disable open loop. Closed loop maf means nothing because once the ecm realizes the engine is warm it goes into closed loop which pulls off ve (it learns fueling values for a 3d engine operation table) and oxygen sensors and tunes according to narrowband readings and learns long term fueling to where it switches which for narrow band is 14.7. So it will use these values and as long as it is not below its base learning to populate PE (power enrich). Basically the computer takes control of the tune on anything under full throttle and relearns pe curves above usualy 60-70% throttle range.
If you have an open loop tune it runs completely off maf and disregards o2 sensor readings. That way under part throttle you can get lean cruise (normally enabled on close loop for fuel economy) and can tune your car to always run rich in under certain airflows or curises beccause it still enables you to do PE based off of rpm and load.
Open loop tunes are way easier to tune because you do not have to test every point on the speed and load curve which can be hundreds of points because it is not just speed and load dependent. Maf uses airflow based fueling and PE to adjust AFR's. It uses resistors that mesaure the voltage required to keep the maf sensor at a current tempature along with IAT data to correct the airflow reading. To determine the amount of fuel. Therefore once the car is tuned for an airflow it does not matter speed or load the ecu dumps the same amount of fuel making it easier to tune. Most production cars use this and speed density is back up except chrysler the still use speed density.
Sorry for the long reply but thats the complete explanation.
If you have an open loop tune it runs completely off maf and disregards o2 sensor readings. That way under part throttle you can get lean cruise (normally enabled on close loop for fuel economy) and can tune your car to always run rich in under certain airflows or curises beccause it still enables you to do PE based off of rpm and load.
Open loop tunes are way easier to tune because you do not have to test every point on the speed and load curve which can be hundreds of points because it is not just speed and load dependent. Maf uses airflow based fueling and PE to adjust AFR's. It uses resistors that mesaure the voltage required to keep the maf sensor at a current tempature along with IAT data to correct the airflow reading. To determine the amount of fuel. Therefore once the car is tuned for an airflow it does not matter speed or load the ecu dumps the same amount of fuel making it easier to tune. Most production cars use this and speed density is back up except chrysler the still use speed density.
Sorry for the long reply but thats the complete explanation.
You don't disable open loop. Closed loop has nothing to do with MAF or SD. You can run closed loop and run of either MAF or SD. It doesn't automatically run off one or the other, UNLESS THE TUNER SETS IT UP TO RUN OFF ONE OR THE OTHER.
Open loop does not run "completely off MAF". Super wrong info there.
Open loop tuning is NOT easy, it is more difficult because you don't have that automatic correction so after dialing in the VE and/or MAF there's OL vs ECT to get right so A/F stays somewhat consistent, and of course there's IAT filters, charge temp bias, etc. to get straight so your A/F doesn't end up creeping from IAT heatsoak. No, open loop tuning is not easy. Not near as easy as getting one close enough to run in closed loop.
You really don't have a clue.........
07-25-2009, 06:24 AM
#13
Also, cams that big tend to cause idle fueling issues from all the raw 02 in the pipes. I've found it easiest to set the tune up to idle in open loop, even if you run closed loop. That way you can set the fueling to what's best for a nice idle, and you don't have the trims trying to drive it either lean or rich.
So, if I were doing the job, it would be an open loop idle/closed loop, speed density tune.
07-25-2009, 07:03 AM
#14
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Cams that big do funny things with MAFs. Moving it closer to the throttle body as they're planning will likely make things worse.
Also, cams that big tend to cause idle fueling issues from all the raw 02 in the pipes. I've found it easiest to set the tune up to idle in open loop, even if you run closed loop. That way you can set the fueling to what's best for a nice idle, and you don't have the trims trying to drive it either lean or rich.
So, if I were doing the job, it would be an open loop idle/closed loop, speed density tune.
Also, cams that big tend to cause idle fueling issues from all the raw 02 in the pipes. I've found it easiest to set the tune up to idle in open loop, even if you run closed loop. That way you can set the fueling to what's best for a nice idle, and you don't have the trims trying to drive it either lean or rich.
So, if I were doing the job, it would be an open loop idle/closed loop, speed density tune.
Its a big cam so you can forget CL pretty much everywhere as even with it enabled the cam has so much overlap it will just give false feedback.. Going SD makes alot of sense too, as it will offer a more accurate air flow model. On top of that if idle MAP tends to move around a bit I would use Delta N based TPS fuelling for idle and just off idle conditions.
07-25-2009, 07:10 AM
#15
I'll openly admit first off that I know jack-**** about tuning, BUT ed seems to me to be a VERY smart person when it comes to all this. I mean I think I semi-understand some of what he says. And the offer frans made is pretty much unbeatable!
07-25-2009, 07:44 AM
#16
Cams that big do funny things with MAFs. Moving it closer to the throttle body as they're planning will likely make things worse.
Also, cams that big tend to cause idle fueling issues from all the raw 02 in the pipes. I've found it easiest to set the tune up to idle in open loop, even if you run closed loop. That way you can set the fueling to what's best for a nice idle, and you don't have the trims trying to drive it either lean or rich.
So, if I were doing the job, it would be an open loop idle/closed loop, speed density tune.
Also, cams that big tend to cause idle fueling issues from all the raw 02 in the pipes. I've found it easiest to set the tune up to idle in open loop, even if you run closed loop. That way you can set the fueling to what's best for a nice idle, and you don't have the trims trying to drive it either lean or rich.
So, if I were doing the job, it would be an open loop idle/closed loop, speed density tune.
Only thing I would do different is depending on what the vacuum is at idle would be to run the Custom OS from EFILive for TPS vs VE if the low speed has issues. To the OP - I have found most vette guys are a LOT more picky then the F-Body crowd.
The items you listed above are all things that shouldn't happen IMO. There is a difference between being picky and wanting it done right. Now in defense to the other people who have tuned the vehilce. I have tuned cars for about 9 years now and ran into a few that have kicked my ***. Eventually after walking away and starting over for the 100x time they came out fine but there are some that you just wonder WTF is really going on. 
You don't have anything to lose except for time and gas. This offer shows (2) things about the company.
07-25-2009, 10:17 AM
#18
I flipped open and closed loop sorry, it was a 4 am. Everyone knows a big cam throws fuel through it at idle because of the overlap its known. It also allows for reversion depending on overlap and timing events which is the only way to affect a maf sensor at idle but its very hard to believe a cam that big has enough reversion to force air out the tb at idle and affect maf, the osciallations might have a slight affect but not enough on the v8 the pulses are too evenly distributed.
Fueling is not adjusted till closed loop. And maf is alot easier than VE because VE is based at every rpm at every map which becomes ten times harder for boosted applications say up to three bar. If you disagree with that then I am not sure you tune. Its alot more than just ECT, IAT, speed bias and spark. The modern day PCM has over 300,000 variables. With thousands of tables.
SD and MAF work together. How they are both independent fueling systems?? GM uses it for quick TPS variations to correct for pressure changes across the maf due to quickly varying throttle but it can be disabled and has little affect on a MAF tune since your TPS variation periods are usually short. Maf means jack if your ve is all messed up and you have done so many mod's that it affects the maf also such as boosting and injector changes if not entered or calculated right within the PCM(pulse width duty cycle determines fuel according to injector specs) and I mean there are a slew of things. The computer will adjust LTM's or BLM's and learn the new values, but is restricted if its trying to run MAF which really is insufficient then because of its inaccuracy. Any tuner he takes his car to will most likely do a closed loop disabled and that means it will not look at the o2 values therefore it has no way to change VE tables. IF the ve tables don't change because BLM's and STM's are turned off (or closed loop disabled) the PCM is completely dependent on MAF if SD is turned off or the completely inaccurate VE tables along with temp corrections and others which will never correct fueling and PE will use the base LTM fuel trim to control its fueling table.
MAF is also the most forgiving as in it uses air flow which is known to fuel and it will allow for little mods for power after (thus all production tunes besides chrysler right now use it). VE will be changed with any adjustment to engine.
*** You have no clue****
You don't disable open loop. Closed loop has nothing to do with MAF or SD. You can run closed loop and run of either MAF or SD. It doesn't automatically run off one or the other, UNLESS THE TUNER SETS IT UP TO RUN OFF ONE OR THE OTHER. -- Every new PCM if the maf is plugged in runs off maf and reverts to SD if unplugged.
I corrected disabling open loop you are right on that. Closed loop has everything to do with MAF and SD. IF it doesnt then how does it adjust any fueling tables. LOL just adjusts spark I guess and the vacuum magically affects fueling. EVERY car is set up to run off MAF from the factory (besides chrysler no maf sensor) with VE as a correction factor and backup in case the maf sensor goes bad. IT will still cause issues in open loop though because the pcm is not "closing the loop" on the O2 sensors therefore it does not look at their readings to adjusting anything so it would not know a bad maf.
Open loop does not run "completely off MAF". Super wrong info there. (You are 100% correct on that) It does not but when you disable VE it does and by completely I mean its the base table once closed loop is disabled which only really adjust the VE values affected by LTM's. Since LTM's are the learning process of the PCM and STM's are the immdediate correction factor that leads to changing in the LTM's due to high or low fueling trends on the VE table in a certain region.
Open loop tuning is NOT easy, it is more difficult because you don't have that automatic correction so after dialing in the VE and/or MAF there's OL vs ECT to get right so A/F stays somewhat consistent, and of course there's IAT filters, charge temp bias, etc. to get straight so your A/F doesn't end up creeping from IAT heatsoak. No, open loop tuning is not easy. Not near as easy as getting one close enough to run in closed loop.
You don't have the automatic correction factor. EXACTLY you dont want that. IF VE IS OFF... IF IT IS OFF not right the pcm pushes the LTM's to extremes because it is looking for the best response from the narrowband IE switching. It picks iterations at the very outskirts of what it believes is its max allowed variation (user can change). This will lead to stalling, sputtering, poor idle characteristics. Except under enough load to lock LTM's and enter PE which is roughly 60-70% TPS on NA motors. STONABONES this is probably the reason why you are having issues can't gaurantee it though. Closed loop is probably enabled with a hybrid form of MAF/SD and is trying to learn fueling. It should get better after a while but I prefer a full MAF tune on any upgraded car. Just because its easier and harder to mess up if you take it somewhere to get done. SD will cost a decent amount more but will be better for every day driveability especially if the tuner is good at it. Also if you are going in the nine's there is a good possibility that you are saturating your maf so the shop had to do a SD tune. Which will DEFINITELY explain your issues.
EDCmat I do not know how you can disagree with that.
Fueling is not adjusted till closed loop. And maf is alot easier than VE because VE is based at every rpm at every map which becomes ten times harder for boosted applications say up to three bar. If you disagree with that then I am not sure you tune. Its alot more than just ECT, IAT, speed bias and spark. The modern day PCM has over 300,000 variables. With thousands of tables.
SD and MAF work together. How they are both independent fueling systems?? GM uses it for quick TPS variations to correct for pressure changes across the maf due to quickly varying throttle but it can be disabled and has little affect on a MAF tune since your TPS variation periods are usually short. Maf means jack if your ve is all messed up and you have done so many mod's that it affects the maf also such as boosting and injector changes if not entered or calculated right within the PCM(pulse width duty cycle determines fuel according to injector specs) and I mean there are a slew of things. The computer will adjust LTM's or BLM's and learn the new values, but is restricted if its trying to run MAF which really is insufficient then because of its inaccuracy. Any tuner he takes his car to will most likely do a closed loop disabled and that means it will not look at the o2 values therefore it has no way to change VE tables. IF the ve tables don't change because BLM's and STM's are turned off (or closed loop disabled) the PCM is completely dependent on MAF if SD is turned off or the completely inaccurate VE tables along with temp corrections and others which will never correct fueling and PE will use the base LTM fuel trim to control its fueling table.
MAF is also the most forgiving as in it uses air flow which is known to fuel and it will allow for little mods for power after (thus all production tunes besides chrysler right now use it). VE will be changed with any adjustment to engine.
*** You have no clue****
You don't disable open loop. Closed loop has nothing to do with MAF or SD. You can run closed loop and run of either MAF or SD. It doesn't automatically run off one or the other, UNLESS THE TUNER SETS IT UP TO RUN OFF ONE OR THE OTHER. -- Every new PCM if the maf is plugged in runs off maf and reverts to SD if unplugged.
I corrected disabling open loop you are right on that. Closed loop has everything to do with MAF and SD. IF it doesnt then how does it adjust any fueling tables. LOL just adjusts spark I guess and the vacuum magically affects fueling. EVERY car is set up to run off MAF from the factory (besides chrysler no maf sensor) with VE as a correction factor and backup in case the maf sensor goes bad. IT will still cause issues in open loop though because the pcm is not "closing the loop" on the O2 sensors therefore it does not look at their readings to adjusting anything so it would not know a bad maf.
Open loop does not run "completely off MAF". Super wrong info there. (You are 100% correct on that) It does not but when you disable VE it does and by completely I mean its the base table once closed loop is disabled which only really adjust the VE values affected by LTM's. Since LTM's are the learning process of the PCM and STM's are the immdediate correction factor that leads to changing in the LTM's due to high or low fueling trends on the VE table in a certain region.
Open loop tuning is NOT easy, it is more difficult because you don't have that automatic correction so after dialing in the VE and/or MAF there's OL vs ECT to get right so A/F stays somewhat consistent, and of course there's IAT filters, charge temp bias, etc. to get straight so your A/F doesn't end up creeping from IAT heatsoak. No, open loop tuning is not easy. Not near as easy as getting one close enough to run in closed loop.
You don't have the automatic correction factor. EXACTLY you dont want that. IF VE IS OFF... IF IT IS OFF not right the pcm pushes the LTM's to extremes because it is looking for the best response from the narrowband IE switching. It picks iterations at the very outskirts of what it believes is its max allowed variation (user can change). This will lead to stalling, sputtering, poor idle characteristics. Except under enough load to lock LTM's and enter PE which is roughly 60-70% TPS on NA motors. STONABONES this is probably the reason why you are having issues can't gaurantee it though. Closed loop is probably enabled with a hybrid form of MAF/SD and is trying to learn fueling. It should get better after a while but I prefer a full MAF tune on any upgraded car. Just because its easier and harder to mess up if you take it somewhere to get done. SD will cost a decent amount more but will be better for every day driveability especially if the tuner is good at it. Also if you are going in the nine's there is a good possibility that you are saturating your maf so the shop had to do a SD tune. Which will DEFINITELY explain your issues.
EDCmat I do not know how you can disagree with that.
Last edited by Radcannon; 08-08-2009 at 07:18 PM.
07-25-2009, 12:27 PM
#19
Ah, a good bit more wrong, or partially incorrect info there.
1: Closed loop or open loop are completely independent of MAf or VE in that they are an automatic fuel correction that can or can not be used in either MAF or SD mode. To say open or closed loop is directly linked to one or the other is nonsense. You can run open loop MAF, open loop SD, closed loop MAF or closed loop SD, or a variation of each in a single tune.
I don't know where you're going here. You must be outta your mind if you think a MAf is going to be anywhere near accurate at 3 bar. Or hell even 2 bar. I'm not sure you tune.
Ve tuning with either EFIlive or HPtuners, using their histograms to plot a VE, it ain't so hard anymore. Maybe upgrade from "Edit" and you'd know this.
Trims DO NOT change tables. They are a percentage correction to fueling. The table is what it is. ST trims makes changes in the here and now to keep fueling oscillating above and below stoich. In the case of short terms trending in one direction for a given period of time, long terms take over, in effort to keep the short terms from having to move as far away from stoich. The goal being rapid "rich lean rich lean" switching to assure 02 saturation of the catalyst bed.
The PCM doesn't use 02 sensor input to determine a bad MAF. How bout you brush up on your enable criteria? These computers are very specific in what they do and don't want to see, and what they use for as far as failure criteria. It is completely possible to still set any of the 3 MAF fail codes in open loop.
1: Closed loop or open loop are completely independent of MAf or VE in that they are an automatic fuel correction that can or can not be used in either MAF or SD mode. To say open or closed loop is directly linked to one or the other is nonsense. You can run open loop MAF, open loop SD, closed loop MAF or closed loop SD, or a variation of each in a single tune.
Ve tuning with either EFIlive or HPtuners, using their histograms to plot a VE, it ain't so hard anymore. Maybe upgrade from "Edit" and you'd know this.
The PCM doesn't use 02 sensor input to determine a bad MAF. How bout you brush up on your enable criteria? These computers are very specific in what they do and don't want to see, and what they use for as far as failure criteria. It is completely possible to still set any of the 3 MAF fail codes in open loop.
07-25-2009, 01:04 PM
#20
I pretty much said all that. MAF's saturate at around 500 g/s give or take some. I corrected my above posting too if you read that you would see where I said that its probably a hyrbid SD tune because with 9's hes probably saturating the maf. hAHA but i guess that was a bad analogy but I do know a friend who broke the computer code and was running double maf's but thats another story. And I would say open loop and closed loop are linked. You will never get closed loop if the engine doesn't warm up and other enables are turned on. Closed loop will adjust fueling tables due to its "automatic correction" or its feedback from o2 sensors. Your pcm does not revert back to base fueling tables when you key cycle. IT uses the LTM's at different speed load points it previously learned on the VE tables in the past closed loop cycles. Thus a bench tuner will say drive the car a few times in order for it to "learn". Its learning its fueling tables but it will always adjust that to some degree if the base tune is off by a fairly decent amount. It should still settle into a trend though and drive better after enough key cycles and long enough closed loop runs.
"Trims DO NOT change tables. They are a percentage correction to fueling. The table is what it is. ST trims makes changes in the here and now to keep fueling oscillating above and below stoich. In the case of short terms trending in one direction for a given period of time, long terms take over, in effort to keep the short terms from having to move as far away from stoich. The goal being rapid "rich lean rich lean" switching to assure 02 saturation of the catalyst bed."
I said that in the earlier post. ST are immediate changes that with trends change LTM's. Depending on the PCM depends on weather or not it adjust the VE tables on a percentage basis. It depends how the programming was done. Most are percentage based.
"The PCM doesn't use 02 sensor input to determine a bad MAF. How bout you brush up on your enable criteria? These computers are very specific in what they do and don't want to see, and what they use for as far as failure criteria. It is completely possible to still set any of the 3 MAF fail codes in open loop."
IF the cal table is bad because the wrong injector size is inputed or an aftermarket maf is used the pcm won't necessarily know until it gets o2 sensor input and start correcting. Yes there are codes that can be set without going into closed loop though. We could go back and forth all day PCM's are different and we are talking about pretty much the same thing. I said I was wrong in my first post and corrected.
"Trims DO NOT change tables. They are a percentage correction to fueling. The table is what it is. ST trims makes changes in the here and now to keep fueling oscillating above and below stoich. In the case of short terms trending in one direction for a given period of time, long terms take over, in effort to keep the short terms from having to move as far away from stoich. The goal being rapid "rich lean rich lean" switching to assure 02 saturation of the catalyst bed."
I said that in the earlier post. ST are immediate changes that with trends change LTM's. Depending on the PCM depends on weather or not it adjust the VE tables on a percentage basis. It depends how the programming was done. Most are percentage based.
"The PCM doesn't use 02 sensor input to determine a bad MAF. How bout you brush up on your enable criteria? These computers are very specific in what they do and don't want to see, and what they use for as far as failure criteria. It is completely possible to still set any of the 3 MAF fail codes in open loop."
IF the cal table is bad because the wrong injector size is inputed or an aftermarket maf is used the pcm won't necessarily know until it gets o2 sensor input and start correcting. Yes there are codes that can be set without going into closed loop though. We could go back and forth all day PCM's are different and we are talking about pretty much the same thing. I said I was wrong in my first post and corrected.
Last edited by Radcannon; 07-25-2009 at 01:17 PM.