1990 CRX HF - rebuild d15b6 or "upgrade" to d15z1?

[Jonathan_ed3]

If this is in the wrong forum please move it.

First post here but I've been trolling for years and years.

I currently have a 1990 d15b6 with 200k miles. No clue whatsoever about service history. I actually bought the thing for parts bc the car had no title and had been sitting in a field for at least 5 years with the windows down and had major wiring issues due to rodents.

I threw the motor into another crx HF shell I had. Topped the oil off bc it was basically at E on the dipstick and had a expandable rubber drain plug that I've not yet investigated. Filled the radiator up with coolant bc the system waa basically empty and rusty.

Surprisingly, it fired right up! To my surprise, no bad noises, no knock, doesn't overheat, transmission shifts good etc.... It idles, runs and drives great. Only CEL is bouncy idle (probably bc I didn't bleed coolant)

Now onto my dilemma. I'm restoring a different crx as a mpg/ semi daily cruiser. I originally intended to rebuild this above mentioned d15b6. Then I found out about the internal parts availability problem.

I've seen how hard it is to rebuild a d15b6 due to parts availability and I would hate to get the b6 torn down only to find out I can't rebuild it. If it came down to it I could sell this d15b6 and the car its in as a running/driving car and use those funds towards the crx I'm restoring. I would hate to lose that $$$ opportunity by tearing down a motor I wont ultimately use.

I would like to stay obd0 for simplicity sake and to keep costs down but again, I would hate to pick this route and get screwed halfway in with parts availability.

On the flip side, I think upgrading to d15z1 will net better fuel economy and will certainly have parts availability but will probably cost more by the time it's all said and done. The z1 also has more power (should I ever need it for passing etc)

Question: what are the real world expectations for mpg difference at highway speeds between the b6 and z1 in an HF using the HF trans?

I found the guy with the burgundy crx page who details his z1 swap but he wasn't b6 equipped already. I Would like an apples to apples comparison.

Some background info: I'm extremely mechanically inclined and have done just about every Honda or V8 swap imaginable but lack time. I could only devote a few hours a week to this which leads me to the next issue.

I figured I could get someone to make me a plug n play harness but nobody is interested. Monotech said no. Rywire said no. And another big name eBay wiring guru said he wasn't interested either. Another knock against the z1. I don't really have the time or desire to do all the wiring. I'm at a point in my life where I would rather outsource that kind of work.

I've read a lot of z1 swap threads dating back 5-6 years and MANY of them never run right. How much of that Is bad wiring, I don't know. But it always seems none of them got resolved. Either it runs perfect from the get go or never does. This scares me. At least I know a b6 will run correctly bc nothing will be tampered with.

I really have no desire to do the wiring. I can do it if need be, but it'll add weeks to the build. I'm looking to kind of throw everything together in a day or two.

I don't think theres any way to properly wire and shield that z1 oxygen sensor circuit without introducing interference. A stock d15z1 engine harness might need to be hacked up and spliced in to maintain O2 sensor integrity.

Most of the threads seem to be back from 08-09 when gas prices were much worse. I'm not having much luck with recent ones.

My powertrain/motor budget will be around $1,500-$2k. I have enough to go either route, but I'm looking for some advice from the experts.

Driving route is 80-100 miles daily, 95% highway at 60mph. Very rarely 65mph. Wheels are HX wheels with Michelin tires of yet to be determined size.

I think its important to note that, I will be doing NO mpg driving techniques. Just driving moderately at a moderate speed, so keep that in mind!

[Baltothewolf]

Definitely go D15Z1, if you can find it. At 60MPH lean burn shouldn't be hard to get into.

[Ecky]

Lean burn nets you a large amount of the benefit you'd get from pulse and glide, just by driving in a straight line at a constant speed. Given the parts availability factor, my vote is to try your hand at the Z1 too.