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I will explain to the best of my abilities on what I have searched and tested so far on my 95ttz. To spare you the trouble here are the pertinent engine upgrades that may have some adverse effect on the problem. 740cc injectors
JWT ECU upgrade programmed with (740cc, federal, dual intake single MAS program)
JWT 530bb turbos
Dual MAS upgrade per FAQ on tt.net (functioning properly, verified by another tt.net member with the same setup and by fuel controller)
Apexi II Fuel controller (set up to “average” function)
Grid Dual solenoid boost controller (tested and verified working properly)
Snow Performance Water/Methanol injection (using 18-25% methanol mix) Deleted EGR (using a resistor on the unused harness plug to prevent code 32)
Deleted Carbon Canister
Bypassed ECU boost sensor to prevent code 26
Idle control unit duty cycle set to 20% (good, smooth, stable idle)
Throttle sensor voltage @ around .40 to 0.42 volts
No trouble codes present at this time
No vacuum leaks, used boost leak tester. First I need to get a stable signal. I tried measuring a number of ways using conventional timing light (verified it’s in good working order on another Z). All rpm measurements are performed using the digital RPM reading on the Apexi fuel controller.
1) Used PTU loop, no dice :( I get wild fluctuating results, +/- 3-8 degrees)
2) Tried wire harness going to #1 coil pack, works better but on occasion it will miss a revolution every now and then, somewhat temperamental.
3) Tried extending the high voltage side of the coil pack, very good results, stable, and consistent. So now after finding a reliable method of measuring here are the timing results:
1) @ 900 RPM with idle control plugged in, jumps between 15 degrees 80% of the time and 20 degrees 20% of the time.
2) @ 900 RPM with idle control un-plugged, same results as above.
3) @ 700 RPM, idle control un-plugged, 20-25 degrees, fluctuates a little less at this rpm.
4) @ 750 RPM, idle control un-plugged, 18-22 degrees, still bouncing around a little bit.
5) Watching the timing when I just barely move the throttle, instantly jumps to 30 degrees regardless off idle control’s current state. I initially said to myself, holy cripes I’m way too advanced so I marked where the CAS was and then adjusted it so I would see 15 degrees @ 700 rpm. As a result the fluctuating timing issue disappeared and was getting a rock solid reading. So then I took the car out for a drive boosting @ 16psi without any water injection to see how the car is running. It ran REALLY bad. The car would not build a consistent boost, severe loss of power with an inconsistent power band, yuk. Just for kicks I immediately checked the timing again (@ 900 rpm, with idle control plugged in) it read 8 degrees. I took my tools with me and drove the Z slowly advancing my timing to see at what point the car runs better with a strong consistent boost. The CAS ended up being clocked about 1-1.5mm retarded to where my original mark was. I don’t know what to try next. I have absolutely no idea if the timing is correct. I drove some more with the water injection turned back on and increased boost back to 20 psi. The car was running good with a little less power so I advanced the timing back to my original mark, back to a fluctuating base timing. Just for kicks I swapped some parts (known to be in good condition) from another ttz to see if it made any difference. I swapped out my ECU with an 8 bit ECU with same JWT upgrade minus the dual intake single MAS. When I made the necessary adjustments to the fuel controller there was no change in timing consistency issue. Cleaned the PTU, CAS, TPS, AAC, IACV connections and also verified that the ECU harness is properly seated in the ECU, no change. Tried swapping the CAS thinking there might be a problem there, no change. Tried adjusting the TPS to 0.45 Volts, no change. I compared the CAS position to my friends ttz, mine looks a little more advanced by about 2-3mm. So after all of this, what next? Any ideas, questions? There has got to be an explanation to this…….
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