125shifter

I pulled the lower plugs when I was adjusting the valves before the car goes on the dyno and the left side spark plugs show to be lean. The left side plugs are a very light brown and right are very dark brown. Any idea what could be causing this? Is this something wrong with the fuel system or exhaust or should I just compensate with the ECU?

DonE

A couple of things come to mind - fuel pressure or voltage to that side of injectors. This is how I found out that my bulk head connector was crap - the left side plugs were leaner showing low voltage to those injectors. I eliminated the connector and the voltage was evened out and the plugs showed even spark.

125shifter

The wiring to the injectors does have a separate 12V wire to each side so this could be the problem. I used a good Deutch 42 pin connector. It has gold plated solid connectors so I don't think the connector is the problem but I guess it could be where I spliced the wires to split it to the 3 injectors.

pzull

Fuel pressure drop as fuel lines have a longer way to travel. When I did EFI, fuel trim compensation had to be made for left and right banks

125shifter

I talked to my tuner, he thought it might be cam timing if the chain's stretched a little. Never heard of that before.

A930Rocket

With a new chain? And the engine was just timed? I don't know about that one.....

DonE

If anything, the timing is not correct side to side. I have seen motors that are off by a couple of mm from side to side, but not sure it would give the same results you find - they just don't run all that well.

125shifter

Seems a little weird to me too. I'm pretty **** about cam timing and I've set cams on a couple other 911's to set so I don't think that's it. The first time I didn't believe it could be so easy so double checked with a degree wheel, boy those Germans are crafty. They are new chains.

I'll just adjust the injector trim a little to compensate.

I had a little problem with my Clewett wires (they were a very early set) but they sent me new ones and they're worlds better. I should have it on the dyno this week or next.

DonE

Wires - very good point. My Clewett wires corroded at the plug end and increased the resistance by 4x and 5x. All the spark (wasted spark system) went to the other side.