Pfc data logit don’t connect
 

There are two types of DataLogit boxes.
The first, oldest, and no longer made is the FD3S beige colored box. This is only for RX-7s.
The newest is the Universal black box that can be used on many cars.

In your laptop software, you must set it up properly and tell it which box you are connecting between the PFC and our computer.

Getting 850 primaries to idle then drive properly is very hard. 550/850 = .647 and then you enter 64.7 into the injector front primary % and 850 into size.
No matter what you do to the idle fuel it will run very rich but will drive fine from idle. The only way to lean out the idle is with negative lag.
But when you do this do get a lean idle, the engine stumbles or dies when you try to accelerate.

That is why for years some of us have said to do not use them, stay with the 550 or go with ID750s.

To use the Bosch 850s, you will have to trick the PFC. You still have to use the negative lag for leaning idle.
Try playing around with the inj % or size in Setting 5. Some have gotten them to work. Ask for direct help with this on the single forum.

Yes, listen to chuck. The benefit vs the struggle of an 850 over a 550 is not worth it. I ran 850 primaries for a couple years and hated every minute of it. No idea why I didn't do anything about it. I'm doing 550/1600 now and it's the greatest. Trying to fiddle with the 850 primary isn't worth it. You absolutely can get it to work but not without a lot of compromise. Switch to the 550 and everything will be better without a noticeable change anywhere else while maintaining a normalish idle and low load driving ease.

Yes and no. Apexi back engineered the PFC for the RX-7. But for some things they frigged up. I does not allow you to go below a certain fuel setting for idle no matter what values you entered and is saved.
This causes the 850 idle problem. Some tables you can change the centigrade temperature points and some not.
Idle control does both air and fuel adjustments, to keep a stable idle along with a fixed AFR with the air pump working.. You can not run it for only idle speed only.