Is there a Doc in the house?
#1
06-26-2009, 08:56 AM
Is there a Doc in the house?
Hey Doc,
Didn't want to jump in and cause commotion on your intake thread, but I did read all 27 pages plus on the cold air intake. To be honest, I left any engine experience I had on a 69 Mustang. I am not a engine hound, but I know the basics on the new engines.
From what I understand there is a pretty big debate whether modifying the CAI does anything beneficial - long term.
From other reading, it has been mentioned that there is an initial change in performance for the car, however the computer is self learning (like our Hummers). After a while the computer modifies the new air intake to adjust the fuel air mixture back to "stock". I had read possibly one way around the PCM doing the re-adjustment was to throw one of the Tuner ships on the system to lock in the parameters one would want.
Outside of the better sound, I was curious what you have seen long term and also if you have a tuner chip on your system or running the pcm stock.
Thanks!
Didn't want to jump in and cause commotion on your intake thread, but I did read all 27 pages plus on the cold air intake. To be honest, I left any engine experience I had on a 69 Mustang. I am not a engine hound, but I know the basics on the new engines.
From what I understand there is a pretty big debate whether modifying the CAI does anything beneficial - long term.
From other reading, it has been mentioned that there is an initial change in performance for the car, however the computer is self learning (like our Hummers). After a while the computer modifies the new air intake to adjust the fuel air mixture back to "stock". I had read possibly one way around the PCM doing the re-adjustment was to throw one of the Tuner ships on the system to lock in the parameters one would want.
Outside of the better sound, I was curious what you have seen long term and also if you have a tuner chip on your system or running the pcm stock.
Thanks!
#2
06-29-2009, 03:36 PM
An intake installed on a stock H3 will produce a permenant improvement. Actually, in 200 miles or less, the factory tuned PCM can learn what to do to adjust the fuel trims to most efficiently run an intake. It's called box learning. The maximum amount of learning parameters are set by the default factory tune. It will go back to the parameters it had prior to the intake once you remove it after a similar 200 miles or so with out it.
The stock PCMs are tuned to consistently seek the most efficient fuel, spark, MAF and MAS settings withing the range of their default paramaters and will do so indefinitely. The GM PCMs maintain a memory in this vehicle of a minimum of 300 start cycles, so yes, and intake mod produces a long term performance improvement. As long as the intake is installed, the PCM will retain what it has learned to run it most efficiently and will NOT return to a stock setting (pre intake install) by itself.
I personally have a PCMforless.com custom tune. You can use them, or other mail order PCM tuners, or seek out a local PCM tuner and have them cater the tune to your own needs. These tunes are for much more than just an intake, and control a wide range of variables which are too numerous for the simple answer to your question.
The stock PCMs are tuned to consistently seek the most efficient fuel, spark, MAF and MAS settings withing the range of their default paramaters and will do so indefinitely. The GM PCMs maintain a memory in this vehicle of a minimum of 300 start cycles, so yes, and intake mod produces a long term performance improvement. As long as the intake is installed, the PCM will retain what it has learned to run it most efficiently and will NOT return to a stock setting (pre intake install) by itself.
I personally have a PCMforless.com custom tune. You can use them, or other mail order PCM tuners, or seek out a local PCM tuner and have them cater the tune to your own needs. These tunes are for much more than just an intake, and control a wide range of variables which are too numerous for the simple answer to your question.
#3
06-29-2009, 06:18 PM
It could also depend if your asking about closed loop or open loop power!!!
The stock mass air flow calibration is correct +-4% as long as nothing in the intake tract has been modified. If the MAF meter, air lid, air intake, or air filter has been modified than the MAF Airflow vs. Frequency table will need modification.
To put it simply what's happening is the Mass Airflow Sensor (MAF) is calibrated to expect outside air temperatures and temperature change rates within a specified range. When you add an aftermarket intake you often get colder and therefore denser, more oxygen rich air, than what the MAF is calibrated for. It interprets this as more air than expected when in reality there really isn't. In turn the PCM tells the injectors to stay open for a longer period of time by lengthening the Injector Pulse Width in order to inject more fuel into the combustion chambers. By doing so the air-fuel ratio remains at 14.7 parts of air for every one part fuel. Hence it is neither lean nor rich but rather right where it's supposed to be.
But, when you go WOT the PCM remembers it had to add additional fuel during closed loop and adds this extra fuel in addition to a predetermined amount called for in the Power Enrichment vs. RPM table. This results in a too rich condition at WOT and a loss of horsepower. Or to put it another way: not as much H.P. as you can obtain should that extra fuel not have been added.
For this reason you want the LTFT's as close to zero or slightly negative during closed loop so no extra fuel is added during WOT. You do this by using scanning software and a program such as LS1 Edit, etc. to get the LTFT's correct. Once they are you can then tune WOT using a wideband O2 meter and typically adjust the PE vs. RPM table for the AFR you want. Note: some applications such as nitrous or forced induction cars usually require a richer AFR than a normally aspirated car.
What is closed loop you ask? Closed loop operation means the front O2 sensors (forward of the catalytic converters) are used to help determine the AFR and offer feedback to the PCM as to the current AFR. The PCM then adjusts the injector pulse rate to maintain a 14.7:1 AFR. So it's just that, a closed feedback loop.
What does open loop operation mean? Well, instead of using a closed feedback loop (the O2 sensors are not used for input) the PCM uses a lookup table that, to put it simply, is just a table that says "at this RPM use X amount of fuel." This is called the PE vs. RPM table or "Power Enrichment vs. RPM" table.
For this reason you want the LTFT's as close to zero or slightly negative during closed loop so no extra fuel is added during WOT. You do this by using scanning software and a program such as LS1 Edit, etc. to get the LTFT's correct. Once they are you can then tune WOT using a wideband O2 meter and typically adjust the PE vs. RPM table for the AFR you want. Note: some applications such as nitrous or forced induction cars usually require a richer AFR than a normally aspirated car.
What is closed loop you ask? Closed loop operation means the front O2 sensors (forward of the catalytic converters) are used to help determine the AFR and offer feedback to the PCM as to the current AFR. The PCM then adjusts the injector pulse rate to maintain a 14.7:1 AFR. So it's just that, a closed feedback loop.
What does open loop operation mean? Well, instead of using a closed feedback loop (the O2 sensors are not used for input) the PCM uses a lookup table that, to put it simply, is just a table that says "at this RPM use X amount of fuel." This is called the PE vs. RPM table or "Power Enrichment vs. RPM" table.
One thing to do to learn more is to get EFI Live. The software is free. Just download it from their site and start playing around with it. I have had mine for a while. My H3T Alpha is my 4th motor to tune. For me it is the only way to go. I cannot see how a mail order tune perfectly. Better than stock, of course...perfect, no. There is just way too much going on from state to state and from truck to truck.
Last edited by H3Tex; 06-29-2009 at 09:54 PM.
#4
06-30-2009, 02:34 PM
Now I am a little confused. So an aftermarket intake is not really good unless you tune your pcm?
#5
07-01-2009, 09:03 AM
That last one was one of those more information than needed posts. .. er something like that. To state that recalibration is "needed" is an opinion. While I agree it is the way to do it up right, the whole enchalada kinda thing, it is not required. The opinion was base upon what intakes often do, not what they are actually doing on a specific vehicle... a generalization if you will.
The H3s have O2 sensors down stream from the CATs, nothin up front, so the answer is my second post, at least for our Air Doc Intakes on the L52, LLR and LH8 motors. I'm not hear to bash the competitors' intakes.
A PCM tune will compliment an Intake significantly, but is not needed to enjoy long term improved performance from an intake alone.
There is also a very recent GM bulliten on what "any" PCM adjustments will do to your warranty, and I can assure you, the tuner people do not like that one. So, in a perfect world, you have to ask yourself, do I want to void my entire powertrain warranty for a tune so my intake works as good as it hypothetically can possibly perform, or am I happy with an inexpensive performance improvement that will leave my warranty in tact?
The H3s have O2 sensors down stream from the CATs, nothin up front, so the answer is my second post, at least for our Air Doc Intakes on the L52, LLR and LH8 motors. I'm not hear to bash the competitors' intakes.
A PCM tune will compliment an Intake significantly, but is not needed to enjoy long term improved performance from an intake alone.
There is also a very recent GM bulliten on what "any" PCM adjustments will do to your warranty, and I can assure you, the tuner people do not like that one. So, in a perfect world, you have to ask yourself, do I want to void my entire powertrain warranty for a tune so my intake works as good as it hypothetically can possibly perform, or am I happy with an inexpensive performance improvement that will leave my warranty in tact?
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