My CRX SI has a stock D16b engine and has had persistant head problem and now I am looking at just putting a D15 engine in it .... I mostly do highway miles and fuel expense will benifit my bottom line Is this a simple swap, I will procure a jmd engine for it . any advice is appriciated in advance...

 

Going with a smaller, less powerful engine does "not" mean you will get better fuel mileage. It often means the engine has to work harder to perform.

When i did my very 1st engine swap back in 1996 in my 89 crx Si, i installed a dohc zc engine which made 130hp stock, as well as more tq. The result was a gain of close to 50-60 miles per tank in better mileage! Why, because the engine worked less hard to et up to speed, and maintain it....something to think about

 

If you want mpg's just swap in an HF engine (D15B6). Get the HF tranny for the taller gears and you'll be getting 55+ mpgs.

 

I had a single zc in my civic before I did a dohc zc swap. it was pretty simple as it is the same in a crx cuz all the sohc motors are pretty much the same in the older models. you will get better mpg with a jdm sohc zc because it does have more hp and torque then the d15 and d16. Making it easy to get up to speed faster resulting in better mileage. Your tranny plays a big factor too if your wanting a excellent commuter. IMO go with the jdm dohc zc swap. great gas mileage and when ya wanna have fun its all right there when ya need it.

 

The difference in mileage between 2 identical D16b's will likely vary as much as a D15 vs a D16. If you want to get better mileage, keep the D16 and just make sure it is running right. Getting the car tuned would surely get you 10%+ improvement, but the cost would take a while to recoup in fuel savings. You could also add a front lip to help your aero, my makeshift one made from a chevy truck lip i found got me about 5% mileage gains on my integra.

 

If you are swapping the motor as a cheap way to fix the head issue, just swap in the D15 long block and keep the MPFI fuel injection, dizzy and all the accessories. Heck, you could just swap in the D15 head, if your D16 bottom-end is still good.

If you want better mileage, swap in the tranny from either an HF or an 88 DX hatch. Both have longer final drives than what you are using now. *That* will increase your highway mileage substantially since your 5th gear cruising rpm will drop significantly, yet the motor will still have plenty of power to hold that speed.

--Andy

PS: I just happen to have an 88 DX tranny in perfect condition sitting idle. I also have the matching clutch disc that will allow it to swap right into your 89 CRX. PM me if interested.

 

I'd be more than happy to take the d16 trans from the OP. Would love to have a non LSD spare.