Announcing ECUtune Stage 2v4
Ok, we recently changed the stage 2 software from nitrous oxide tuning to tuning for using a z32 maf meter. The main impetus for this change was to make it possible for the engine management system to measure more airflow and open the doors to forced induction on the SVX; however, there seemed to be significant interest in using this modification on naturally aspirated SVX's and there seemed to be good reason to expect good results could be attained with some revisions. The recently released stage2v3 has thus been revised and with these revisions we have been able get a nice increase in torque while expanding the power output that can be met by the stock injectors.
This software now not only paves the way for supercharging, turbocharging, and running higher rpms but improves performance on a stock SVX.
It is based on the Stage 1v4 software and thus has the same fuel map modifcations and ignition advance revision table modifications which greatly improve around the town drivability and part throttle responseiveness. In the Stage 1 software the base ignition timing map was left unaltered in order to avoid any problems for people who live in areas where 93 octane is not available. This software is specifically geared towards those much more performance oriented and thus base ignition timing advance is modified to take advantage improvements in accuracy of airflow measurements and of changes we've made in afr to increase torque.
The Stage 2 software allows the use of a z32 maf meter on the SVX. The airflow on a healthy stock svx is reaching the limits of the factory SVX mass air flow meter. Airflow at 6400 rpms reads as 4.4 volts on our demo car with the SVX mass air meter which is capable of putting out from 0 to 4.8 volts. The z32 meter is capable of measuring much higher airflows, above 500 hp worth of air. Airflow at 6400 rpms reads as 3.7 volts on the z32 maf meter.
The voltage from the maf meter is used by the ecu to look up a value in a translation table which reprsents airflow. This value is later scaled by a constant. We've adjusted both the translation table and the constant.
This is what the factory translation curves look like. They give a value for every .08 volt of maf voltage. The values in the svx table are higher than those of the z32 table but the z32 table values are multiplied by a larger constant. It's the result of the table value times the constant that results in comparable #'s
There aren't enough digits available in the svx ecu software to make the constant big enough to match the z32 maf meter so we have multiplied the difference through the translation table values. If we were going to leave it at that, as we did in the stage2v3 software this is what the table would look like:
In version 4 we've made further adjustments to the translation table which bring the afr down at lower airflows and bring it up at high airlfows. In the stock svx the car runs richer than necessary at high rpms. By bringing the translation table values for higher voltages down we are able to provide fuel for higher airflows before reaching the limits of the fuel injectors. Because this meter measures high airflows much more accurately there are no voltage fluctuations at high ouput which cause variation in afr between cyllinders and revolutions which necessitate a lower afr and less ignition advance. This is what the table looks like after our adjustments.
Once multiplied by the ratios of the constants used you can see the airflow being measured by the z32 meter in comparison to the svx meter.
The result of our modifications of the translation table are that the afr at wot throttle is now in the range of 12.9 to 12.4 on our demo car which has a walboro fuel pump. A stock svx will run slightly leaner, an svx with an impreza fuel pressure regulator will run slightly richer, and an svx with both a walboro fuel pump and an impreza fuel pressure regulator will run richer still. All scenarios should work fine with this software.
Having richened the afr at low airflows and increased the accuracy of the afr control and ignition advance control at high air flows we were able to substantially increase ignition timing advance for torque gains.
The stock ignition advance table looks like this:
The stage2v4 ignition timing table looks like this:
We made some pulls on the dynapack dyno at mastro to see our results and posted some very nice #'s. All measurements are very accurate and were repeated with extremely tight tollerances. We have a comparison plot between the tsb rom software and the stage2v4 software. With the walboro fuel pump both performed very well but stage2v4 posted some very nice torque gains and was able to maintain power at high airflows despite our leaning out the afr. The factory tsb rom actually did really well with the addition of the walboro fuel pump. (wrx's with manual transmissions put down 168 on this dyno, with an extra 5% loss we're obviously doing well better than either a stock wrx or stock svx and it was 93 degrees today) The added fuel pressure really seams to help with the stock software. I'd have to say that a walboro fuel pump or impreza fpr would be a good modification for those with 96 and 97 svx's who don't yet have the option of getting our software. It has about the same effect on afr so wide open throttle performance is basically the same as stage1v4 is on a stock svx although you won't see the around town, part throttle performance enhancements seen from the ignition revision table modifications which our software offers. Back to the goodies......In the plot you can easily see how much more acurate the z32 meter is at measuring high airflows by the absence of jaggedy thingys at high rpms. With the stage2v4 software power and torque is increased all the way through 5900 rpms with substantial low and mid end torque gains.
