druidesque

So my dad has a 91 crx w/ 160k miles on it...and he's looking to get 45+mpg's out of it.

Currently he has two other crx's...one which he drives and is able to consistently get 40+mpg with...basically stock crx si w/ 13inch wheels.

Today we pulled the motor out of the 91 crx.

He has a 93 cx motor he'd like to use...along with an hf transmission...

Now, we have a few options regarding the cx longblock.

Use cx intake manifold...or use the si manifold. My guess is the cx manifold will yield better fuel economy...but the sensors need to be switched over...to utilize the 91 crx si harness.

He only has an si ecu...so keep that in mind. Ideally he'd like to find an HF ecu to use w/ the cx motor...

All of your suggestions are welcome.

CRseXxy

my suggestion and its only a suggestion is to keep the CX manifold. If your gonna do all of this work might as well shell out a little extra for the sensors and ecu... Its been awhile since I last junkyard shopped but u should be able to pick all of it up at one spot... outta of curiousity, what model?

crxcess

45mpg is easily attainable with any model crx. Now if you were aiming for 60mpg, I wouldn't use a 90-91 crx.

scottmog

You are doing it wrong then.

Get a d15z1 civic vx motor with ecu. I've seen a couple of crxs with that, hitting 70+ mpg.

Jenkinsal2

look into removing some weight and do a bit of reading up on aerodynamics you can help a good deal by making a few small modifications to the car shape.

zrickety

iTrader: (1)

pretty easy goal. i did 47mpg in an 89 crx dx with a d16a6 and the dpfi manifold, on stock 13's

JRZ88DX

is the 90-91 heaver then 88-89?

druidesque

A few more details on the setup.

The car is a 91 crx si and we have a good condition cx motor.

I'm going to run that longblock and adapt (if possible) the crx si sensors to the cx intake manifold. If this doesn't work...I'm going to switch the si manifold over to the cx longblock although I'm guessing that will hurt efficiency.

Longblock already has a new timing belt and new clutch...so hopefully the HF trans my dad picked up (with 160k miles on it) will be in good working condition.

I'm going to reinstall everything tomorrow...and see how it all works out.

East_McDuck

I got like 48-50mpg when I had my HF. That was all highway miles, though. Find you an HF, or the transmission from one.

88Hatchy

You won't be able to take advantage of the D15b8 without the correct ecu. It might even get WORSE mileage.

druidesque

...well I spent 4 hours on the car today.

I adapted the EF harness to the 8valve cx longblock. This included bolting the CRX SI intake/exhaust manifolds onto the longblock.

As some of you know, the ports are different on 8v heads...so i opened them up to match the si intake manifold.

Tomorrow i'm going to bolt the HF trans onto the car...swap over the driver side engine mount...and bolt it all back into the car.

As far as the ecu situation...we'll see how it all goes. I'm hoping to find an HF ecu to mate with the car...but I doubt mileage will decrease much considering the fact that my dad already gets 40+mpg out of his other two si's with si transmissions.

I think the biggest key is the gearing...and ultimately the final drive which allows for ultra low rpm's at 40-60mph which is the speed most people drive at most of the time.

He will also be running 13inch wheels with skinnier tires to reduce rolling resistance along with removing all the AC components.

Of course...I'll post results once the car is complete so you guys can see how this setup does.

My guess is 55mpg...maybe 60mpg...mainly because of the gearing.

specialized108

i would assume that you have even thought about chipping an ecu and then taking it to the dyno? i would assume that you have thought about replacing the exhaust with something more efficient than the stocker for more power/efficient fuel consumption. and if i were trying to milk every bit of gas mileage out of a car i would do this just to get rid of the bit of richness that all cars have. couldn't hurt, should help..... right?

detuned

in my 89 HF i swapped the SI motor in with the PM6 ecu and retained the HF transmission (hubs, axles, knuckles, flywheel needed) and got 45mpg city. 50+ highway. Transmission is going to make the biggest difference, I'm not bench racing here, I switched to the DX transmission and it dropped by about 10mpg. HF has the lowest rev's in gear.

And the SI plugs into the HF harness, just reuse an HF dizzy. ECU swaps right on.