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pkp4911 pkp4911 is offline
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Join Date: Jan 2000
Location: Evergreen, CO USA
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Porsche Crest Experiencing same 3 codes 594, 356, 358 3.6 engine swap into 986S

Hi, I've posted and dealt with Scott at Softronic over this same recurring issue. A chicken and egg conundrum because thus far, despite several hundred miles, (not yet 1000 miles since swap completed) I've yet to resolve. I have an 03 986S with an 03 M96 3.6 engine swap with Softronic 3.6 performance tune on the 986S 7.8 box. Still running stock exhaust but had to create a basic cold air induction when the shop who did much of the heavy lifting with the swap installed the motor without first mounting the OEM air box/filter. I created a basic cone filter with a relatively sealed airbox which then feeds into stock diameter (3") MAF tube with new Bosch MAF in stock location. I also fabricated a mesh inside the tube to emulate the same screen grid/distance from MAF as the factory did.
Both 986 and 996 use same MAF and it is my understanding that MAF is engineered to cope with either 3" diameter or 3.5" from 996. immediately after MAF I coupled and upsized tube diameter via an elbow to 3.5" which ultimately is attached to the stock 996 TB via alum 3.5 tube and elbow. Flow disruption is minimal except for coupler and elbows. I am also utilizing factory 3.6 intake plenum and all vacuum lines were correctly attached.
TB is squeaky clean and my understanding is that the MAF sends its signal based on incoming (pre) air to ECU. Since this is still the 3" diameter, I don't understand why MAF is confused as to tube diameter which is what Softronic suggests...unless the 3.6 tune needs to see 3.5" air flow? (Until today, have never heard that this can also be tied to carbon canister as stated in response below...)
During swap, we replaced anything we could within reason like OAS, intake gaskets and did a final smoke test to ensure no blatant leaks. Everything went smoothly until we started dealing with ECU/MAF issues. I initially had 3 MAF's go on before we could get the car to run and idle smoothly. Scott forgot I live in Colorado so put a sea level tune on the ECU originally. Tune is now set for altitude, but I keep getting these codes--and then CEL ultimately trips. Over the course of driving with the Durametric, I also got a code for a bad pre cat 02 sensor so I replaced both at same time. The car is not making full power and some of this is due to altitude I'm sure.
What am I missing? The only other thought I have is to upsize the incoming diameter pre MAF to 3.5. The 3.2 that was initially in here (and spun #1 bearing during DE event) made more seat of the pants power per the butt dyno.
The other day I was driving when I came to a stop after sustained highway it died. When I restarted, it ran very rough and would not idle. I was forced to reset but don't remember if the error codes were different then.
Per the Durametric, here is an example of my readings at idle with oil temp at 84.0C:
Top line Mass air flow (HFM)@23 kg/h
Altitude correction runs between 0.80 and 0.76 ( I live at 8000' but Denver at 5200' value drops the higher I go...)
2nd Mass air flow reading at 22.4 kg/h
02 sensor voltage ahead cat bank 1 matches bank 2 at or around 0.72 with mean values both banks 1.01 and 1.02 What do those mean values represent?
RKAT values close to each other at idle at 0.33%. From 2000 rpm to 4k stays around 0.84% I haven't noticed any gross differences bank to bank (I did when bank 1 o2 sensor failed--like I said, I just replaced both at same time.)
These are random but are they close to normal? Can someone give me normal ranges at 1K RPM increments? Does this apply and what variables exist tied to differences at altitude?
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Patrick
Old 03-07-2016, 07:10 AM
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