Project: Mavro Gato - 99 Turbo'd 3L

[warmonger]

Originally Posted by FastCougar

PCM flashed and test driven. My hat is off to Tom on really improving the car's manners. The engine is MUCH more responsive on throttle tip in and there is much more power throughout the RPM band. I am however still getting an intermittent stumble when above 6K RPM, which I am attributing to my plug wires. I'm currently running a set of used Manecores. They will be swapped out for stock wires tomorrow night, then another test drive.

DAtalog these wires first so we can see what effect is tuning and what effect is plug wires please.

[FastCougar]

You mean datalog the Magnecore's before replacing them?

[FastCougar]

Well, I replaced the wires with stock units and the upper RPM stumble is still present. There is definitely an ignition and/or fueling issue above 6K RPM. Below that limit, the engine runs perfect now with the new tune and has plenty of power above 3K RPM.

I just thought of something ... my plug gap! I'm running a stock gap of .054 inches.

Now, keep in mind, I'm running 9:1 CR pistons with bowl work done on the heads, so I'm figuring roughly 8.8:1 CR. Wouldn't I want to adjust my plug gap considering I'm a full point of compression lower than stock? I would figure that I need to increase my plug gap to say .060 inches. Sound right?

[warmonger]

Originally Posted by FastCougar

Well, I replaced the wires with stock units and the upper RPM stumble is still present. There is definitely an ignition and/or fueling issue above 6K RPM. Below that limit, the engine runs perfect now with the new tune and has plenty of power above 3K RPM.

I just thought of something ... my plug gap! I'm running a stock gap of .054 inches.

Now, keep in mind, I'm running 9:1 CR pistons with bowl work done on the heads, so I'm figuring roughly 8.8:1 CR. Wouldn't I want to adjust my plug gap considering I'm a full point of compression lower than stock? I would figure that I need to increase my plug gap to say .060 inches. Sound right?

No, leave it stock or even a tad tighter. The plug gap is set to cause the highest energy spark. Tighter the gap with no changes to the coil voltages and you get a lower energy spark. Raise the gap will give more energy but also maybe a misfire. Lowering the compression will make it spark easier as well but not significantly I think.
If there is a higher rpm stumble then we could have ignition, fuel, air issues...or electrical connection issue that could cause a problem in one of those areas.
We have to have the datalog of every spark related parameter (spark, knock sensor, max allowed, borderline knock, mbt if available, etc), MAF, rpm, throttle position, load, maf counts, IAT, ECT, fuel trims, O2 sensors, and any relevant piece of information you have..

[FastCougar]

I have a wideband O2 sensor. I'll get the gauge all hooked up first, then do some datalogging for you this weekend.

[FastCougar]

I just got done test driving the car after installing the wide band AFR gauge. This thing is sweet!

I had to remove that oil pan bolt in order to fit the sensor. Once in and torqued down, I simply reinstalled the oil pan bolt.



I then ran the wiring up past the rear roll restrictor and then across to the passenger's side wheel well, following the battery relocation wiring.



Rather than drill a hole in the firewall, I came up through one of the floor pan holes by drilling a small hole in the cap.



From there, I ran the wire behind the kick panel in the passenger's foot well, back behind the glove box and then behind the HVAC center holes.



That took care of one set of wires (From the sensor to the gauge). The other set of wires (4 of them, from the gauge to power/ground), where rather simple. I had to find a switched source ... I ended up using this green wire coming from the steering column.



One wire to a switched source, one ground and then two optional wires for data sampling. I'm going to get a serial dongle and hook it up so I can data log it through the XCal2 ... that requires a trip to Radio Shack tomorrow

Here is the finished product



I'll get some video of it working later tonight

After hooking up the gage, I went on a 1 hour test drive. Here are my observations:

I noticed something that I suspect if the cause of my high end stumble.

At light cruise, AFR = 12.5 to 14.5
At light to moderate throttle input (50% at most), AFR = 11 to 12.5
WOT, AFR = 10.0 (it's lowest reading)

After going WOT and it dips to 10:1 (or lower, but I don't know since it will only read 10), if I get off the gas, it will stay at 10:1 for a very long time. The only way to get it to settle into light cruise readings is to lightly open the throttle and then get back off gently.

Could this be attributed to the MAF transfer function or is it pointing to something as simple as a faulty TPS sensor?

[FastCougar]

Here is a video of the Cougar ... I love my Cruise Cam camera holder!

Right Click Save As 15.4MB 640x480 WMV file.

[seaneyo99]

WoW! dont know what eles to say thats freaking awesome!

[warmonger]

Originally Posted by FastCougar

Here is a video of the Cougar ... I love my Cruise Cam camera holder!

Right Click Save As 15.4MB 640x480 WMV file.

Video actually helped combined with the datalog you sent.
Tune Sent.

[FastCougar]

Tune flashed and data logged ... that has to be a record for me. WHAT A DIFFERENCE!!! Check your email.