I have 91 CRX HF. When I purchased the CRX the previous owner removed the original D15b6 and dropped in a SOHC ZC motor (no VTEC). I know it's a common swap but what’s unique about the setup is twofold: he kept the HF tall geared transmission and he retained the HF intake, injectors and ECU. This combination is unique as is – a medium between better performance and good gas mileage. I’m averaging mid-30’s in the city, and mid-40’s on the highway.

On to my dilema. My daily commute to work consist of climbing two grades on the highway. When I'm ascending the power seems to slowly give and I would have to drop to fourth to somewhat sustain my current speed. I've been patient for about a year until I was passed up recently by a Geo Metro.

So far I have installed an SiR muffler and had a muffler shop put in 2.25" piping from the muffler to the cat. And I also just put in an AEM CAI. There was a fractional gain, but I can honestly say there wasn't much of a difference when climbing these grades.

I know the HF tranny is killing. But is there any other way around that, that I can do to give my rex some ***** when going uphill and not get passed up by a metro?

 

Did the previous owner retain the 8V head as well or are you running the 16v head?

 

8v

 

Is the check engine light on?

Do some maintenance just to make sure all is in good working condition before you go changing parts. Injector cleaner, new filters, spark plugs, etc etc.

I'm not surprised that you have to drop into 4th on a steep climb to sustain speed. The HF was built to deliver some low end power and not so much on the high end. This probably explains the difficulty you are having sustaining speed and accelerating on climbs.
If you swapped out the intake manifold, injectors, and ECU for Si parts, it would be less than $100 and give you some extra go power. If the head is still the 8v as Todd00 was asking, then swapping that out as well is going to help, but that is up to you. I would go after the previous parts first and see how you like it.
Follow up with a nice exhaust header if you going for it.

I'm not mentioning the transmission because I'm pretty confident that you can still make your commute climb and mpg friendly by just upgrading the bottlenecks of motor.

 

opened the thread, saw CRX HF

 

Well I've always wondered how an 8valve head would perform with a 1.6 block (all else being equal) so you answered that for me. Aside from that, now that you've stated you're running the 8valve head all I can say is that's just life with an 8 valve. I've daily driven my 94 CX which basically uses the same engine for probably a decade. It just doesn't have any usable power. It's really the perfect definition of a "Point A to Point B" type of car.

So now that you know that, really outside of a turbo the only thing worth doing while retaining your existing block is swapping to a 16valve style head (VTEC or non-VTEC, either will be a HUGE jump) and find another transmission. An Si transmission is preferable but a DX/LX is still light years ahead of the HF transmission.

 

Even with the 1.6 block you will maybe only have a few HP more than the stock 1.5 configuration. And the HF was a sloooow car in the first place.

An intake and exhaust won't help the fact that your still running all of the 8v HF top-end parts.

Switch to the 16v head and needed parts and you'll see a good improvement. Otherwise, everything else is a waste of money (like your exhaust and intake).

 

16 valve for lyfe brah

 

Thanks, I'll start searching for those parts and make the changes.

I'm unable to make the header upgrade unless I swap out the tranny. The way the tranny was built on the HF somehow is different from the DX/Si models and the header is routed or mounted differently.

I'll try those mods and keep you posted.

 

That just doesn't sound right.


On the outside they are all the same.

 

lol, just swallow your pride and let people passs you man.

 

Header passes under the oil pan and comes nowhere close to the tranny to interfere.

 

Secondary LOL: You will pass these people while they are at the gas station...

 

LOL, you guys are funny. All these cars passing me now whether I like or not. Sometimes I feel like I can hop out the car and run faster.

I took my friends word about the header not fitting and I wish he would have showed me what exactly was in the way or would not allow an after market header to fit. On another note, I came up on CL for an 89 Si ECU, intake manifold and fuel injector for a $100. I asked the seller to take a photo of the ECU nomenclature on the unit to verify that it is a PM6 model. If that is not the correct model please correct me. These parts should be in my hands Sunday evening.

Thank you everybody for the help and tough love.

I'll keep y'all posted

 

Todd00 has a great point regarding the 8v / 16v head.
While you have the intake manifold off, it would be a great benefit to swap heads too.

 

make sure you get two more injector clips! theres a few really good writeups for the process too, one of the better documented processes ive found.

 

I'm going to (hopefully) assume you are buying these parts to go with a 16v head that you'll be purchasing soon.

Otherwise, you are wasting your money again.

 

yes i assume he's gonna get a 16v head ?

 

The guy that was gonna sell me the parts never contacted me back. So, I'll be looking elsewhere. I'll be looking for that 16v head also. Back to CL.

 

I just came up on the intake manifold w/fuel injector intact and a PM6 ECU. He's also willing to part with his D16A6 head w/dizzy. What are your thoughts on that head? anybody...

 

If you have a shop near by - they can do vacuum test of the head and tell you if your valves are sealing or not. Other than that - without taking it apart to inspect the cam, I would flip it over and looked carefully at the valves as well as mating surface of the head. If you have any scoring or scratches that you could identify w/fingernail - head milling is in order, if you could check for warpage with a straight edge - that would be great, if there are nicks and gauges in the surface that are deeper that resurfacing could take care off - this head is junk.

Google around for effects of damage on valve appearance to get an idea problems you may be looking for. Although I have never done it before, I kinda imagine it would be like troubleshooting based on spark plug appearance.

 

After doing some thorugh research on the D16A6 head, its intake manifold w/fuel injectors, and PM6 ECU; I found there would be no gain at all as the ZC head is slightly tuned better with an aggressive cam timing. So I found the best fit would be a D16Z6 head along with its components across the board. If there are any objections please let me know. This will take time to gather parts becuase parts are not as cheap. I found a Z6 head for $250 on CL. I'll keep looking a bit longer until I can find something cheaper.

 

A6 head is perfect.
The other heads might be better, but A6 is a 16v and will be great for what you seem to want to do.
Z6/Y8 heads have vtec and then you are asking for an OBD1 conversion to use them properly.