How big of an engine can run on Factory FI
 

How big of a four cylinder 914 engine can be run with a factory 2.0 liter D-Jetronic system and what modifications are needed to run a larger engine?

2056cc is pretty easy. It can take some tweaking of the system to make it work well, and those adjustments (especially of the MPS) can be very fiddly. I haven't heard of people going any larger than that with D-jet in quite a while. There are reports of people running up to 2.5 liters with D-jet, but I would be very cautious of that and probably would want to spend some real quality time with a Wide-Band O2 meter to make sure the mixture isn't going crazy.

D-jet is not the most easily tuned system out there, so it can be a challenge for it to run well on anything but a totally-stock motor.

--DD

When (if considering) choosing an upgraded camshaft you need NOT to get too radical on overlap, lift specs; as this will disrupt the vacuum signal which is most important on the MPS. You don't want to wind up with an engine that idles at 1,200 rpm and "Hunts"

can the same be done with 1.8 liter, or?

Do you mean putting the 1.8's L-jet onto a 2056cc motor, or do you mean putting D-jet onto a 1.8 motor?

Supposedly the 1.8's L-jet can handle 2056cc fine. I would want to make sure that it doesn't go lean at high RPM and throttle settings, so a Wide-Band O2 meter I think would be a must.

D-jet can be used on a 1.8 motor. It might take some tweaks; the 1.8 will flow slightly more air for a given RPM and throttle setting, but extract less power due to lower compression.

--DD