HF vs DX motor

[StorminMatt]

A short time ago, someone here mentioned slapping an HF top end on a DX bottom end. I was thinking about maybe trying this until I can get a D15Z1 to swap into my 1989 Civic HB. The parts can all be gotten quite cheapy at local pick-and-pulls. But I have to wonder whether this is really worthwhile. Would the economy gains even be large enough to matter? Or am I better off just saving my money?

[FritzR]

That was me with the HF/DX motor. It seems to be working just fine but I only have about 500 miles on it at this point. With the old tires it was getting 50mpg at 60 mph or so. I got it some new tires but it is to soon to tell. It does coast a lot better now. I think you would need to put the HF trans in there though to get the 2000 RPM at 60 MPH freeway mileage

Another option if you don't want to pull the head would be to turn the motor into the 4 speed hatchback motor. It has the lower rpm torque like the D15B6. You would probably still want to use the HF transmission. Still a lot of work probably camshaft, throttle body/injectors, ecu.

D15B1

(Same as the D15B2 engine, but with a mild camshaft, and a restrictor plate between the throttle body and intake header)

* Found in:
o 1988-1991 Honda Civic Hatchback
+ Displacement : 1493 cm?
+ Bore and stroke : 75 mm X 84.5 mm
+ Compression : 9.2:1
+ Power : 70 hp (52 kW) @ 4500 rpm & 83 ft?lbf @ 3000 rpm
+ Valvetrain : SOHC (4 valves per cylinder)
+ Fuel Control : OBD-O DPFI


What kind of mileage are you getting now?

[SVOboy]

What're you waiting for on the z1?

[FritzR]

Originally Posted by SVOboy

What're you waiting for on the z1?

Those motors are very available JDM for $500 or less. If you want to get started in the right direction you'll need the HF trans for the swap. If you just did the trans first that would help by 5 - 10% acording to Gary Palmer here

[StorminMatt]

Originally Posted by FritzR

Those motors are very available JDM for $500 or less. If you want to get started in the right direction you'll need the HF trans for the swap. If you just did the trans first that would help by 5 - 10% acording to Gary Palmer here

Well, I really don't have $500 to spend on a motor. And I am not in any particular hurry here. S I'll just wait and see what I can get. It would always be nice to find a motor that a swapper is getting rid of for next to nothing, though.

As for the HF transmission, I got one a couple of weeks ago at a half off sale at the local Pick-And-Pull. It ended up costing me around $40 - this is seriously the way to go if you want an HF transmission! I actually just got the transmission in the car today. And talk about an eye opener! Third gear is already taller than fifth gear on my ITR CRX. And needless to say, the instantly available power of the ITR is not there. Of course, it never really was before, either. So it's not like it's some kind of major loss. Let's just say that this is not a car for the mountains. On the other hand, freeway cruising sure is nice and quiet. It will certainly be a good, cheap car for, say, drives between Sacramento and the Bay Area.

As for mileage, I have obviously not measured it et. But this will be interesting. The car originally had a 1988-1991 SI transmission. So freeway revs were quite busy. On the freeway, mileage was no better than the ITR CRX - low 30s. But let's see what it will do now.

As for the Civic STD stuff, I actually have everything needed for the swap. I guess this is something to consider for the interim. I'm not sure how much it will help economy, though.

[Danronian]

I would see how your mileage is before swapping in a different motor. The RPMs with the HF tranny will probably be so low that your mileage will go up a lot.

[FritzR]

Originally Posted by Danronian

I would see how your mileage is before swapping in a different motor. The RPMs with the HF tranny will probably be so low that your mileage will go up a lot.

And you should document you results here with a gaslog so the next person will know what to expect if they try it.

[SVOboy]

PM 78si...