Once you have the new percentages in the VE table, what difference will it make in closed loop? It seems to me this only makes life easier on the narrow band oxygen sensor and feedback-fewer corrections to make. I think I can see where adjusting this table would benefit a stock Prom on an engine w/ a cam or head change (VE increase), but what about a stock Prom on a stock engine? How do you get the stock prom on a stock engine to run richer (like 12.5:1) for more torque at each RPM (especially under 3K)? Does the answer lie in changing the VE table or is it in another table?
Supreme Member
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It seems to me this only makes life easier on the narrow band oxygen sensor and feedback-fewer corrections to make. I think I can see where adjusting this table would benefit a stock Prom on an engine w/ a cam or head change (VE increase), but what about a stock Prom on a stock engine?
How do you get the stock prom on a stock engine to run richer (like 12.5:1) for more torque at each RPM (especially under 3K)? Does the answer lie in changing the VE table or is it in another table?
There are alot of variables, so without knowing all of them, it's hard to say.Originally Posted by tee-boy
Once you have the new percentages in the VE table, what difference will it make in closed loop? It seems to me this only makes life easier on the narrow band oxygen sensor and feedback-fewer corrections to make. I think I can see where adjusting this table would benefit a stock Prom on an engine w/ a cam or head change (VE increase), but what about a stock Prom on a stock engine?
How do you get the stock prom on a stock engine to run richer (like 12.5:1) for more torque at each RPM (especially under 3K)? Does the answer lie in changing the VE table or is it in another table?
Closed Loop tries to maintain a 14.7:1 AFR.
As long as your running closed loop, and have resonable BL's, then there will be little change.
Get a WB, disable closed loop, and start tuning.
BTW, when not in PE mode, there's no reason to run that rich.
Richer then Stoich. (14.7:1) is only to aid, in cylinder cooling.
TGO Supporter
Yes, there are benefits to tuning a stock engine. Before I started to modify my L98, I honed my tuning skills on my stock engine. I was able to get the car to do the quarter in high 13s, improve it's driveabilty and improve it's fuel economy (I hit 30 US mpgs on the highway).
I found tuning the VE tables improved the driveabilty more than anything else. There are many instances when the engine is NOT in closed loop (or drops out of closed loop), that's when a properly tuned VE table is important.
As for increasing the AF Ratio, the ECM strives for 14.7:1, which is a combination that yields the compromise between fuel economy, emissions and longevity. As Bruce/Grumpy suggests, many guys who get seriously into tuning, tend to run "open loop" and usually tune for a bit richer - where the engine seems to prefer to run. But generally not too much richer than 14:1 (for part throttle).
In WOT, the ECM goes into P/E and the ECM no longer runs in "closed loop" (well I'm lying, but it's a long technical explanation). The important thing, the ECM now relies heavily on those VE Tables (and P/E tables) and you run much richer.
Truthfully, the stock programming is far too rich if anything. I have found most "stock" engines with the stock programming runs somewhere around 11-12:1 (far richer than optimal). I've even seen a few that were running in the 10s. Most stock engines need to be leaned out when in WOT (P/E).
So yes, there are definite advantages to tuning a stock engine. But the best one, it gives a "newbie" a chance to start learning his craft while having his stock eprom as backup. Most guys get into eprom burning because they have already modified their engine - and then they are faced with the problem of having to make massive changes without having any idea where to start.
If you start with a stocker and hone your craft - you'll know what to do when you decide to modify your engine.
I found tuning the VE tables improved the driveabilty more than anything else. There are many instances when the engine is NOT in closed loop (or drops out of closed loop), that's when a properly tuned VE table is important.
As for increasing the AF Ratio, the ECM strives for 14.7:1, which is a combination that yields the compromise between fuel economy, emissions and longevity. As Bruce/Grumpy suggests, many guys who get seriously into tuning, tend to run "open loop" and usually tune for a bit richer - where the engine seems to prefer to run. But generally not too much richer than 14:1 (for part throttle).
In WOT, the ECM goes into P/E and the ECM no longer runs in "closed loop" (well I'm lying, but it's a long technical explanation). The important thing, the ECM now relies heavily on those VE Tables (and P/E tables) and you run much richer.
Truthfully, the stock programming is far too rich if anything. I have found most "stock" engines with the stock programming runs somewhere around 11-12:1 (far richer than optimal). I've even seen a few that were running in the 10s. Most stock engines need to be leaned out when in WOT (P/E).
So yes, there are definite advantages to tuning a stock engine. But the best one, it gives a "newbie" a chance to start learning his craft while having his stock eprom as backup. Most guys get into eprom burning because they have already modified their engine - and then they are faced with the problem of having to make massive changes without having any idea where to start.
If you start with a stocker and hone your craft - you'll know what to do when you decide to modify your engine.
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Closed Loop tries to maintain a 14.7:1 AFR.
As long as your running closed loop, and have resonable BL's, then there will be little change.
Get a WB, disable closed loop, and start tuning.
BTW, when not in PE mode, there's no reason to run that rich.
Richer then Stoich. (14.7:1) is only to aid, in cylinder cooling.
Thanks.Originally Posted by Grumpy
There are alot of variables, so without knowing all of them, it's hard to say.Closed Loop tries to maintain a 14.7:1 AFR.
As long as your running closed loop, and have resonable BL's, then there will be little change.
Get a WB, disable closed loop, and start tuning.
BTW, when not in PE mode, there's no reason to run that rich.
Richer then Stoich. (14.7:1) is only to aid, in cylinder cooling.
three more questions:
Will tuning the VE table to minimize closed loop corrections make any positive changes (increased fuel mileage or torque or both)?
Do you think maybe the answer to the above question is a function of how out of wack the BL's are?
Do you suggest running in closed loop or open loop for daily driving?
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I found tuning the VE tables improved the driveabilty more than anything else. There are many instances when the engine is NOT in closed loop (or drops out of closed loop), that's when a properly tuned VE table is important.
As for increasing the AF Ratio, the ECM strives for 14.7:1, which is a combination that yields the compromise between fuel economy, emissions and longevity. As Bruce/Grumpy suggests, many guys who get seriously into tuning, tend to run "open loop" and usually tune for a bit richer - where the engine seems to prefer to run. But generally not too much richer than 14:1 (for part throttle).
In WOT, the ECM goes into P/E and the ECM no longer runs in "closed loop" (well I'm lying, but it's a long technical explanation). The important thing, the ECM now relies heavily on those VE Tables (and P/E tables) and you run much richer.
Truthfully, the stock programming is far too rich if anything. I have found most "stock" engines with the stock programming runs somewhere around 11-12:1 (far richer than optimal). I've even seen a few that were running in the 10s. Most stock engines need to be leaned out when in WOT (P/E).
So yes, there are definite advantages to tuning a stock engine. But the best one, it gives a "newbie" a chance to start learning his craft while having his stock eprom as backup. Most guys get into eprom burning because they have already modified their engine - and then they are faced with the problem of having to make massive changes without having any idea where to start.
If you start with a stocker and hone your craft - you'll know what to do when you decide to modify your engine.
Great reply. Thanks. I have been reading up on PCM's and tuning for about 6mo's. I just purchased all hard/software for logging and tuining, and have burned a couple of logs. You have definitely cleared up some of the questions that were still lingering in my mind.Originally Posted by Grim Reaper
Yes, there are benefits to tuning a stock engine. Before I started to modify my L98, I honed my tuning skills on my stock engine. I was able to get the car to do the quarter in high 13s, improve it's driveabilty and improve it's fuel economy (I hit 30 US mpgs on the highway).I found tuning the VE tables improved the driveabilty more than anything else. There are many instances when the engine is NOT in closed loop (or drops out of closed loop), that's when a properly tuned VE table is important.
As for increasing the AF Ratio, the ECM strives for 14.7:1, which is a combination that yields the compromise between fuel economy, emissions and longevity. As Bruce/Grumpy suggests, many guys who get seriously into tuning, tend to run "open loop" and usually tune for a bit richer - where the engine seems to prefer to run. But generally not too much richer than 14:1 (for part throttle).
In WOT, the ECM goes into P/E and the ECM no longer runs in "closed loop" (well I'm lying, but it's a long technical explanation). The important thing, the ECM now relies heavily on those VE Tables (and P/E tables) and you run much richer.
Truthfully, the stock programming is far too rich if anything. I have found most "stock" engines with the stock programming runs somewhere around 11-12:1 (far richer than optimal). I've even seen a few that were running in the 10s. Most stock engines need to be leaned out when in WOT (P/E).
So yes, there are definite advantages to tuning a stock engine. But the best one, it gives a "newbie" a chance to start learning his craft while having his stock eprom as backup. Most guys get into eprom burning because they have already modified their engine - and then they are faced with the problem of having to make massive changes without having any idea where to start.
If you start with a stocker and hone your craft - you'll know what to do when you decide to modify your engine.
TGO Supporter
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three more questions:
Will tuning the VE table to minimize closed loop corrections make any positive changes (increased fuel mileage or torque or both)?
Depends. Because it's closer to what's really needed you will probably find it has better drivability when it's transitioning. But if you get the VE Tables closer in conjunction with the P/E tables & spark tables, you probably will notice better performance.Originally Posted by tee-boy
Thanks.three more questions:
Will tuning the VE table to minimize closed loop corrections make any positive changes (increased fuel mileage or torque or both)?
For better fuel economy you will either need to tune the Highway Mode Tables or tune for Open Loop.
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Do you think maybe the answer to the above question is a function of how out of wack the BL's are?
I'm not really sure what you are asking here.Do you think maybe the answer to the above question is a function of how out of wack the BL's are?
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Do you suggest running in closed loop or open loop for daily driving?
Ultimately, you should strive to tune for open loop and control everything yourself. Don't expect to do it overnight or even a weekend. It will be a "long steady process and a labor of love".Do you suggest running in closed loop or open loop for daily driving?
Initially you will probalby find the "closed loop" version runs better - but that's a good indication that your tables are off. You know you are getting closer, you will probably find the car starts to run better in open loop than closed loop.