Which d series is best for mpg and hp?

[914turboford]

I have been driving my d16a6 powered AWD 1974 Civic for 3 months now. I drive just under 100 miles a day on my commute from Pollock Pines to Orangevale, CA. I have been getting 25 to 29 mpg with an average of about 27. At some point I want to put in a later d series engine. I would like to get more hp and better mpg if possible. Would a SOHC vtec be the best choice? I am going to stay d series other wise I would have to use a CRV transaxle and I don't want to go to the trouble.

Brian Roth

 

[Slammed90Lude]

the best fuel economy would come from the vtec-e motor D15Z1

however you're gonna lose horsepower over your current motor that way

the most powerful of the d series motors is the JDM d15b, following closely by the d16y8 and then the d16z6

all of those motors are vtec and you shouldn't have a problem getting better gas mileage with them, assuming you can keep it off the high lobes-
not that the vtec on the sohc motors is particularly aggressive or fuel thirsty

 

[phunky.buddha]

I would seriously look into getting a D16Z6 and convert your ECU setup to OBD1. The OBD1 ECU has more precise fuel maps, so it meters out gas to your engine without running it as rich as the non-OBS systems. You can also run a custom tuning system like Uberdata or Hondata to tune the fuel maps a little leaner to pick up more power and fuel economy. Factory maps tend to run a little on the rich side for safety. Tune out some of the "safety net" and make sure you don't do something stupid like put junk gas in the tank and you'll be fine.

 

[914turboford]

Do I have to have two of those ultra expensive O2 sensors (before and after cat) to run OBDI? I don't have a cat right now. The d16z6 is the dohc motor, right? I'd also like to be able to run regular gas. The d16a6 is supposed to run premium but I run 87 octane with no apparent problems. That jdm d15b sounds interesting. What kind of ecu do I need for that. For that matter, would changing the ecu on my current d16a6 get me better mileage without sacrificing power?

 

[phunky.buddha]

OBD1 just uses one sensor before the cat, and you can use the $40 Bosch sensors that you pick up at AutoZone if you really want. With a custom tune on Uberdata or Hondata, you can tell the ECU to ignore the O2 sensor and run off the fuel map without any closed loop correction too.