Tuning AFR on 1.8L w/DJET Options

[Spoke]

I bought a Zeitronix ZR-2 Wideband AFR to tune my 911 and decided to use it first to tune the 914.

I am datalogging to my laptop since I didn't get the gauges.

The ZR-2 is temporarily connected to the engine until it's tuned properly then it will end up installed in the 911.

I picked up the 1.8L engine a while back and mounted the original DJET FI from this car. The engine seemed to run lean so I am "fooling" the FI by adding resistance in series with the CHT sender. Right now I have about 400 ohms in series with the CHT sender. The goal is to get the AFR right by either tuning the MPS or changing the CHT sender if it is low in resistance or both.

I need to check the fuel pressure before making any changes to the MPS or CHT sender.

The ZR-2 is just sitting in the trunk for now. I have the data cable running out of the trunk and into the passenger window with the PC in the passenger seat.



Since I'm not permanently mounting the ZR-2, I didn't want to cut into any wires to get 12V. So I used the unswitched 12V from the 25A fuse and just connect and disconnect power to the ZR-2 when testing. I was able to get power from the relay connector for the rear window defroster and held it in with a tiny screw.



The throttle position sender was a little tricky to figure out. I mounted a potentiometer to the throttle body then rigged an idler arm to rotate the pot when the throttle is opened. Everything fits around the return spring and intake boot. The rotation of the pot is only about 30% of its throw so WOT is at 30% of potentiometer rotation.



The AFR sensor is mounted on the exhaust tip.