'89 Honda CRX Si Versus HF weight
 

I've really been itching for a CRX swap: '88 or early '89 (i.e. prior to 89.5 when they changed the seatbelt setup for the heavier doors). I have an early '89 HF, but I've always been jealous of the Si moonroof. Anyway, I thought if I could find one of the early Si cars I could swap my HF motor & transmission in. I have three questions with regards to this:

1) would the CRX's open moonroof be detramental to good FE? (bear in mind they do have that nice little tilt to them to help w/airflow, when open.

2) Is there a WEBSITE ANYWHERE that can tell me the difference between the weight of an '88 Si and HF? (All of them just seem to bunch all of the 88-91's together...but I know I have the lighter 2nd gen HF...not the heavier one that came with the seatbelt changes and whatnot).

3) I figured if the Si body's (since I'll be swapping my engine, remember) is about the same weight as my HF, I would want to know if I can get away with a straight up swap with keeping the Si's wiring harness intact. ...These cars are supposed to have the same wiring harness (Si & Hf).

1. Yeah, prolly, how much Iono.
2. Check the honda-tech EF forum faq thread
3. HF also has egr, correct? Incorrect? I'm starting to forget all this crap...but it should be a straight swap with only one or two things...

HF has EGR, will require transferring over the EGR "Black Box" not hard to do.

From personal experience owning a 91 CRX Si and removing the Sunroof and replacing it with a 3 lb fiberglass plug, I dropped 28 pounds from the top of the car. I also removed ~20 lbs of sound deadening that was in the Si model as opposed non in the HF model. Taking in account of the differences in and under the dash between the two models, HF has no clock, usually no A/C (which means no A/C components under the dash, no tilt, no Dead Pedal, no rear wiper controls... this ends up being about a 150lb difference in weight between an 88 HF and an 88 Si model. Taking in account the door mounted seatbelts, bigger Door impact beams (88s didn't even have them) and a few other reinforcement differences (HFs have a different front bumper support, WAAYY different/lighter) The difference between an 88 Hf and 91 Si was just under 300lbs difference. Even the 91 HF was ~150 heavier than the 88 model.

You can swap out the 90-91 doors for the 88 model doors and install pillar mounted seatbelts into a door mounted system (requires welding in one or two nuts per side) As well as swapping over some of the Delete plates and vents that the HF uses.

Having the sunroof open disrupts the airflow over the top of the CRX badly when it is in it's fully open (slid back) position. It hangs over the hatchback a ways and creates a bi eddy behind it.

Hope some of this info helps.

hmm. That does help. Thanks a lot!

I'm with TomO: the external tilt & slide sunroof on the CRX would easily make a measurable difference in FE at highway speeds because it destroys the airflow down the otherwise ideally shaped hatchback of that car.

If I had to rank sunroof designs from bad to terrible, aerodynamically:

bad: internal sliding with no permanent "deflector" ahead of it & pop-up deflector when open
worse: same as above, but with permanent external deflector
terrible: external tilt & sliding

I understand that this thread is as old as dirt, but I was just wondering how much of a difference in mileage the weight difference makes between the two. I just need a rough estimate to see if it is worth purchasing a si shell or to keep searching for a hf shell which is becoming harder to find.

A couple of MPG per 100 pounds with the HF powerplant. The problem is putting an HF engine & tranny combo into the Si body is a bad thing.

You are MUCH better off putting a VX engine & tranny into an Si body. Bit more complex but much more bang for the buck.

That's exactly what I'm doing but I'm having a hard time trying to find an HF, especially the 88. I have the engine and ECU ready and am picking up a harness soon. It's like having a VCR with no TV.:(

1989 HF: 1834 pounds
1989 SI: 2138 pounds

The BIG reason for this large weight difference is that 1989 CRXs are unique in the sense that the HF has no door seatbelts, while the DX and SI DO.

If you cannot find an early HF, I suggest finding a 1988 DX model. DXs are MUCH easier to find, since SO many people have such a GREAT fear of the DPFI-MPFI conversion (which isn't even hard). And the 1988 DX is the ONLY 2G CRX DX that does not have door mounted seatbelts. It weighs 1922 pounds. And because it has no sunroof, it is not at all hard to bring the weight down to HF levels simply by swapping bolt-on parts.

What about a 90 hf? I just found one for sale that looks pretty clean inside and out. He wants $500 for it and it includes some nice wheels, stock si engine, and a b18 with tranny. Problem is that I have to drive about 4 1/2 hours to pick it up on friday. How much of a weight difference between an 88 and 90 hf?