[Subscribe to Daily Digest] |
Members do not see ads below this line. - Help Keep This Site Online - Signup
Here is little something for those people want to know a little more what heppens in a T7 car when HW parts are being swapped with out making any adjustments to the software.
Firstly we need to understand a little more about the system, one dyno sheet with some results do no tell you anything. Power gain or loss can be explained in tons of ways but I wont get into that.
The T5 system is a pure pressure related system (feels only the boost in mbar) and the intake air temp to adjust (slightly). NO CORRECTIONS TAKE PLACE IN BOOST LEVEL, so if the ECM is programmed for a target boost of 2000mbar (absolute) at a certain rpm, the ECM will control the PWM up to this boost (if reachable).
NO BOOST ADAPTION AT ALL.
The T7 system is a pure airflow (mass) related system, boost (mbar) is not used (only for backup functions). The only systems using both (airflow and pressure) is Bosch ME7 (and 9).
Therefore the boost pressure cannot be specified and changes everyday, depending on atmospheric pressure (this on T5 too)and on intake temperature (hotter=more boost). So if you start with the morning and the intake temp is 40°C, the requested airmass say 1000mg/comb, you could have say 1900 mbar boost (abs). After driving a while in the traffic, the intake temp raise to 60°C and the boost goes up to 2000 mbar on still 1000 mg/comb. Lower density of the air is corrected by the higher boost. This doesnt mean that you get out the same power!!!!!!
Hotter air is more knock sensitive (less efficient), the VE is lower (due to the increased duty cycle of the turbo) and the ignition is reduced.
These are basic functions.
The adaptions, boost or fuel are not so long term. They are adjusted all the time, constantly when u drive in the "adaption windows".
The boost adaption is not really power affecting. On steady load the PID will take care of any kind of positive or negative adaption on boost. SO THE POWER RESULT IS NOT AFFECTED. But on transients (short acceleration) you "feel" it. Negative adaption will cause that you never reach the target boost in the short term (its used to prevent "overshoothing" the request).
The fuel adaption (mult) is affecting the power output. Now, if you have a car that runs "lean" in the closed loop (the lambda integrator has to add fuel to get lambda 1), you will have a positive fuel adaption.
This % value of added fuel will be added on the request in the open loop (out of lambda control).
RICHER MIXTURE=LOWER OUTPUT
Well, I think for the moment its enough and it explains why you "loose" power when you "upgrade" hardware parts on the T7 engines.
The system is programmed to give a "fixed" fuel amount depending on rpm's and airmass. The airmass is a value coming from the original (initial) calibration of the Airmassmeter. If you change a hardware part (airfilter, exhaust...) you affect this calibration, therefore the measured value is not "correct" anymore ( 1 is not = 1 but perhaps 0.99 or 1.01 or whatever). So the lambdaintegrator will need to adjust the lambda 1 factor back (adding or subtracting) and therefore you have a fuel adaption.
Hardware changes have enormous impact on the MAF calibration
Also one should keep in mind that once you change one HW part of the car to a custom piece you will be in this mess fore ever if you dont have the possibility to custom tune your car at some tuner. In the future if you decide to tune your car more, no stage sets will mix with the custom HW part.
My point is not to keep people from buying custom HW parts, I just wanted to shine a little light ower this issue, since "custom part shops" will definetly not give you this infromation.
Just my two cents.
posted by 81.197.20...
, Mon, 13 Dec 2004 04:24:44, Sun, 12 Dec 2004 16:34:12
, Mon, 13 Dec 2004 19:54:30
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
