I have analyzed the test runs that we did at my garage this weekend and promised I would give you some results to use to help show the problem and to help resolve it.
Two test runs were done with outside temperature of 85 degrees.
Each run consisted of 12 miles of 15 miles of distance, using all RPM, gears, and throttle ranges. This included stop/go city and highway driving while I monitored and collected PCM functions status while you drove the car in the manner you do.
Both test runs used the exact same roads and distance to limit any changes and 2nd run was done within 10 minutes of completing first test run.
The following is what I determined via PCM data collected via a Ease enhanced powertain scanner connected to the PCM.
] Mark's Z06 Test Results
NOTE: the trace consisted of over 3,600 PCM read cycles, but to make this viewable using less screen space, the above was sorted to show knock and lean AFR issues. Also content important has yellow background.
Your surging issue is due to your long term fuel trim being 22 percent too lean. The removal of the MAF screen itself did not drive the leanness to that high of a level, but the other mods combined took your Z06 from being a performer, to high heat generating engine.
Even with the MAF screen installed, the existing mods drove the AFR out of a performance window.
You can see within this results sheet :
LTFT far to lean
Lean condition drove engine knock high, for both WOT and normal driving conditions). Cell 22 is WOT when TPS ( throttle) is greater then 99.5% on. Cells 1-19 are when you are pushing on the gas pedal, but not to the floor.
As seen knock is ocurrung in all cells and TPS position.
causing lessor performance at WOT due to timing on;y being an averge of 25 degrees ( about 3 degree loss, that also lowers maximum torque).
As seen by the injector pulse width, the PCM was attempting to go richer but could not achieve better then the 22 % lean average.
Intake Air Temp (IAT) was 5 degrees hotter then outside temps, thus air intake needs to be improved for IAT should equal outside temps when moving fster then 20 MPH.
The engine water temps spiking 220 degrees further hinders a lean condition, and the lean AFR itself helps drive the engine temps up due to hotter internal temps due to too lean buring AFR forcing pistions, sparkplugs, etc to run much hotter.
You'll notice engine knock was present no matter if the RPMs or speed were low or high.
The surging issue was clearly due to the leanness and to test this and to also reduce the knock issue. I hardwired in a MAF translator and simply set the AFR to reduce from a 22% lean down 5% to 16%.
Apon doing that and then repeating test run, knock went from being triggered 43 times to only 14 and all surging was gone ( but not totally when A/C is on).
By further adjusting AFR with the MAFT, both ill conditions can overcome the mods causing the conditions but I do not agree in total to this type pf fix.
The reason is to fight off a lean condition this far off of being perfect ( a LTFT of zero) you have to drive the PCM to go richer which them means it also drives WOT timing down that will also reduce performance.
You can either resolve the mods causing this over lean condition by vendor correcting or removing such mods.
Use the MAFT to drive LTFT as close to zero, but lean enough to maintain about 28 degrees of WOT timing, but not at the expense of increasing knock, which wold retard that timing
Or as I and others have done go with a larger injector such as SVO 30s, and tune out richness, that means going leaner, drives WOT timing up.
I suggest for next testcase, you adjust base of MAFT another 5% richer and re-scan PCM to determine if that is a short term correction.
Feel free to contact me for more idepth information of test results.
Originally posted by EvilZ06 Hi,
Over the weekend I removed the screen from the MAF on my 2001 Z06. I also drilled a hole in the throttle plate as per Halltech's instructions and completed the idle relearn process.
I certainly don't have any problems with surging at idle, BUT i do have significant surging when in motion. Example: I was crusing along the freeway yesterday at 65-70mph, around 1500-2000 rpm in 6th, and the car was surging quite badly. Under acceleration the car performed well, the problem seems to be when you back throttle.
If I pressed the gas pedal to bring my speed up a little, and then let off, the car would buck and surge and felt generally very rough.
I called Jim this morning and he told me that this is to be expected with a 2001 with no screen and that the problem is caused by a lean fuel condition. My car is NOT throwing any codes though. I am going to try the NEW Halltech Z1000 filter to see if this improves things any.
Is anyone running a Halltech TRIC with a 2001 and no MAF screen that has fixed the surging?
Anyone else have any suggestions???
If I can't fix it then the screen will have to go back in because I can't live with the car the way it drives now! :-?