PalmettoZ Posted January 24, 2011 Share Posted January 24, 2011 (edited) I have recently installed a MS II ECU in my Z and am using Tuner Studio to run it. The motor that I have is a 3.1L stroker that has a fairly large Isky camshaft with .535" lift and 305 degrees duration. Torque peak is around 3600 rpm on the Dyno. Default settings on the program suggest a 50/50 % in regards to the TPS vs Vacume, and I am wondering if this is a good idea for this type of cam. Should I be setting it more towards the Vacume driving the enrichment with such a large cam instead of TPS? Wanted input since I don't see any difference when I change the settings to 40% TPS. Also the motor is stumbling from 1700 thru 2800 rpm in low load driving, (feels just like a lean stumble) although the O2 sensor says that it is running around 11. I tried leaning it out but the situation gets worse. Thanks Scott Edited January 25, 2011 by PalmettoZ Quote Link to comment Share on other sites More sharing options...
dga280z Posted February 5, 2011 Share Posted February 5, 2011 My thought would be to use mainly TPS until about ~2500-3000 rpm. The large cam can cause vacuum variances at lower rpm. This causes distortions to the MAP readings which, in turn, can cause rough fuel management at these lower rpms. This may be particularly true under lower loads. Once load or rpm increases enough, this all smooths out making MAP based management more reliable. The bigger the cam, the more this impact expresses itself. As an experiment, try 100% TPS to 2500 rpm and then transition to mixed TPS/MAP above 2500 rpm. Let us know. Quote Link to comment Share on other sites More sharing options...
PalmettoZ Posted February 5, 2011 Author Share Posted February 5, 2011 Thanks for the input. As far as I know, you can only change the % of TPS to vacume thruout the entire RPM range. I don't see a way to adjust the RPM in Tuner Studio. Am I missing something? Quote Link to comment Share on other sites More sharing options...
dga280z Posted February 5, 2011 Share Posted February 5, 2011 (edited) Hi I don't use that software so I cant help with the specific setup. But I thought that the mix of TPS/MAP input could be varied over the full operating range in MS-II. In any event, try mainly/all TPS and see if it smooths out in the trouble range. If it does, then it would appear that the big cam is causing the MAP sensor some issues. If not, then big cam vacuum distortions at light load/low rpm would appear not to be the case. Don Edited February 6, 2011 by dga280z Quote Link to comment Share on other sites More sharing options...
PalmettoZ Posted February 8, 2011 Author Share Posted February 8, 2011 Figured out the problem with the Tuner Studio. I experimented with the % settings going from 50% all the way to 0 then back up to 100. At 0% the motor would barely accelerate at all. At 100% it would rev up great just using the throttle and not driving the car, but I couldn't drive it like this since the motor would stall immediately. It seemed to perform best at 50/50 ratio. As far as the stumbling goes, it was just too lean at that particular vacum / RPM range. As soon as I increased the VE table at the stumbling range the problem went away. Although it seems as though this engine likes to run rich in order to run at optimum. Maybe its the big cam, I dunno. Quote Link to comment Share on other sites More sharing options...
dga280z Posted February 8, 2011 Share Posted February 8, 2011 A little extra fuel in spots can really smooth out some rough patches. Glad it worked out! Quote Link to comment Share on other sites More sharing options...
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