So much potential....
 

Hi everybody. I think this site is just what I've been looking for. I've spent a lifetime modifying nearly every car that I've owned to get more power, and now I've decided to tackle a fuel sipping gas miser. Kind of a change of direction for me, but it should be a fun endeavor.

Anyway, I just picked up an '88 Honda CRX DX (automatic) to use as rolling stock. This is pretty much the lowest FE version of the CRX family, but I still managed to get 46 mpg highway on a recent road trip from Albuquerque to Flagstaff (that's 325 miles, gaining 2000 ft altitude and ending up at 7000 ft asl), so I figure I've got a chance of doing some good things with the car.

For starters the auto trans has got to go. I've got my eye open for either a standard DX or an HF trans to go into it. But I'm open to suggestions on what else to do. Any suggestions and hints will help.... especially if they're vehicle specific.

By the way, the car has about 180K on it right now and it still runs like a top. I'm not planning on replacing the engine unless I find a deal on an engine/trans combo. But changes in the efi, either to another stock system or maybe even a standalone (I've got an MS system sitting on the shelf) system isn't out of the question. A cheap low boost turbo system may be in the cards as well. I think I have the disclipline to keep my foot out of it if I go that route.....

Anywho, thanks in advance for all the good advice I'm sure you're all about to bestow on me;)

another cool toy is the scangauge which will tell you your MPG in realtime. you can't use it because it only works for '96 and newer cars with the OBDII port but there are other options out there. I don't know what they are because all my vehicles are 96 or newer.

just figured I'd put that bug in your ear about it. you could read up on it. I have a truck that will do a 14.5sec qtr (not bad for a truck) so I know what you mean about keeping your foot out of it. the scangauge helped me a lot because I could see what affect my driving had on the MPG.

I have also heard of people swapping in the VX motors into the CRXs to get lean burn. other models have lean burn as well. good luck to you and the manual tranny is a good idea too. I am stuck with an auto and don't want to put the time or effort into changing. sometimes it costs to be a lazy man.

OH and welcome to the site

Hi!

I'm not totally convinced that a manual tranny is always best, particularly if you end up with with the same or lower final drive with a manual. In city driving, practically any standard will save a bunch, but if it stretches it's legs on the highway much, I'd look carefully at the options for the final drives. Modifying automatics with severe duty shift kits appears to me to take quite a chunk of inefficiency out of them, for instance with the shift kit mods on my auto, from 0-60 times vs stock I appear to have gained 10HP at the wheels, this would be about 7% of the power output, so drivetrain loss now has to be in the range for a manual.

Of course the manual allows some highly efficient techniques that the auto doesn't, but if you've got a pure highway pound with heavy traffic, that sort of thing is gonna be difficult to do.

I was rather shocked when I found that a number of 5 speeds are needing over 3000RPM to cruise at 60, my 3 speed auto with the TC locked up takes just ~2600.

MegaSquirt, you say? Cool. :)

Hmm...does MegaSquirt do OBDII?

What? My minivan (Hyundai Entourage) is barely scraping 2000 RPM at 60MPH. I can run in 5th gear at 45MPH @ 1100RPM. It has a 5 speed auto "with manual-shift gate". I don't generally use the manual feature.
(I don't put the Hyundai in the garage w/gaslog because lots of other people drive it, and it tends to get 14-15MPG because they can't keep their foot off the d$%m pedal).

My previous ride (a VW Jetta Wagon TDI) would be around 2200RPM at 60MPH, IIRC. I know it was well over 3000 @ 80MPH and pushing 4k @ 110MPH. Redline was low, around 4500-5000. No, I don't drive that fast anymore.

Man, I miss that car, but I don't miss replacing the starter every 9 months, and other electrical parts around every 10000 miles.

My VW is 3000rpm at 70mph, and in a similar discussion on another forum folks are reporting 4000rpm at 70mph for Hondas.

Well obviously there are 5 speeds with decent ratios, I was just saying to research them, rather than blindly rushing into a "5 speed is always better" trap.

If you're modifying a CRX, a question & a few suggestions.

1) Does it have door-mounted seatbelts? If not, you've got the early 88 version and it's lighter, a plus. If not, oh well.

2) Put in a VX engine and start with an HF transmission.
3) Once that's done, modify a Honda Civic Wagovan transmission for even better results. Wagovan is a 5-speed plus granny gear. Can be modified to turn into a 6-speed. Start with the 1st gear from an Si and end up with a .55 "6th" gear, HF final drive. Will give you most power with the VX engine D15Z1 and the Wagovan modified transmission. You should be able to turn out MPG over 80 with this setup.
4) Lighten the vehicle as much as you can - carbon fiber or aluminum hood, doors, etc., but make sure safety is not compromised. Use a donut spare in the trunk, etc.

Good luck!

Welcome to the club of former Honda power modders now turned FE modders!

101mpg: Hm, my 90 Si had door mounted seatbelts. Wasn't a CRX though.

Most Hondas (except the VX) run about 3000 RPM @ 70 mph, 3500 @ 75, and 3800 @ 80mph. That has been my experience with 4 and 5 speeds, manual and automatics. RPMs are not always bad for FE. Sure, if that were a Mustang, those would be ridiculously high RPM and you'd be wasting gas. But on a Honda with a 7000 redline, airflow through the engine at 3000 RPM has been tuned for efficiency (but not volumetric efficiency). If you were to modify the final drive to the point that you were cruising at 2000 RPM I guarantee you would lose FE (mainly because it would require more throttle to keep the car at speed). Again, the VX is an exception.

More throttle would merely reduce pumping losses and shouldn't reduce FE.

holycow, I don't think that megasquirt does obdii but I know it has capabilities to show just the same data.

a friend of mine just got his kit the other day. if you are thinking of doing megasquirt though, be advised that it comes as a complete do it yourself kit. a raw circuit board with no components on it and many MANY tiny baggies of parts to solder on the board. from what I understand, it isn't that bad but if you aren't expecting it, it will throw you for a loop.

also you need a laptop for it so why not just use that for data.

All 88 and most 89 had the pillar mounted seat belts...90-91 had door mounted ;) plus they 88-89 didn't have the door crash beams in them reducing weight but reducing safety too...This is for CRXs i believe it may hold true for the EF Civics too but not sure

101mpg do you have info about this 6 speed conversion....the wagocan 6 speed was the 4WD trans and the SL gear was to the far left and up so shifting from SL to 1st wouldn't really be a smooth transition plus it uses a cable shift instead of the hard linkage most Hondas use...I have heard people discuss the option of using this trans as a 6 speed but haven't seen any proof or evidence that it would work like you are suggesting...plus being able to find on is super rare anymore...not doubting you just would like some more info on it...

Hal9000 I'd say look for an HF trans, once you swap that in you should see some difference...plus doing a DPFi to MPFI will give you some more room for various motors and an OBD1 conversion may allo wyou some better tuning options...I'd say ideal swapping a D15z1 w/ HF trans or using a cable to hydro conversion and using the CX/VX trans will ultimately give you the best FE but that is a fair amount of work, but would probably pay off in the long run...GL and keep us posted!

Wow... Let me stop my head from spinning and see how many replies and new questions I can get out there in one post.....

In order of appearance:
1) Beef: I'm pretty old school. Rather than mess with a scanguage, I'll probably just mount an old vacuum gauge that I have lying around and shoot for the highest vacuum... It might not tell me my exact gas mileage, but it'll sure tell me when I'm getting the best FE. Thanks for the tip though. Maybe some time in the future...

2) RoadWarrior: The stock Honda auto is not very nice to drive in my opinion. I'd rather just be rid of it. FWIW, 70 mph is about 3200 rpm, and 75 is around 3400 with the auto. Not bad, but not great. The HF trans is pretty tough to find, so I'll probabl just pick up a DX or SI trans and install an HF diff in it for starters. That should be a vast improvement over the stock auto-box.

3)HolyCow: The MS unit I have is actually slated for the Cosworth/Mercedes that I've been building up for bonneville. I may never get that project done at the rate I'm going. But I have all the necessary parts, my unit is assembled and ready to go and I could easily throw it into the CRX if I decide to.... I'm not sure if I want to go that route yet though.

4) 101mpg: My CRX does have the seat belts on the pillar and not the door. Sounds like there's some confusion about what that means though... Anyway, can you tell me more about the wagovan swap? Also, I'm actually new to Hondas. Is there any primer info for the VX engines floating around? Why are they better, Could I build one with just a head swap (a lot of the D series engines seem to share the same bottom end), and what donor vehicles did they come out of? etc etc. The more info the better.

5) Suspended: Any suggestions for a Honda newbie? My power days were in VW's and Mercedes. I'm still learning the ins and outs of my CRX. Any tips in general would be appreciated (even if it's just to avoid breaking some tab on the back of the door panel)

6)Loserkid: What all is involved in the MPFI swap, and what cars should I look at for donors? Also, regarding the various engine/trans swaps. Do I need conversion mounts for the D15Z1 engine, and will it bolt to the standard HF/DX trans? Also, what's involved with teh cable/hydro conversion for the CX/VX trans and what's the payoff?

Thanks for all the help guys. The more you talk the more I know what direction I'm going to go......

Clarification - '89 CRXs did NOT have pillar mounted seatbelts. Only half of the '88s did. I've done my homework on this. Glad to know you have the early '88. I'd like to get one myself, currently have a 1989 DX.

VX engine (D15Z1) comes whole, and you'll need to do a complete engine & computer swap to effect this. Also requires some wiring modifications. There are harness kits you can buy.

The D15Z1 only comes out of the Honda Civic VX, 1992-1995. Basically it's the CRX HF hatchback, an extension of the HF technology. The engine is more powerful AND gets better mileage than the HF engine. The D15Z7 is the same engine from Japan, and in almost all situations less MPG, slightly more power. The D15Z1 is the best engine for this swap, not the D15Z7

If you're doing a full engine rebuild you can buy custom pistons from theoldone.com that will increase mileage further for the CRX & VX engines. "Roller wave" pistons on the components page.

Search these forums for CRX VX D15Z1 swap, also use Google for the same terms and you'll find the necessary info. Same for the Wagovan transmission swap.

Yes, going from granny gear to 1st is odd with the Wagovan "6-speed", but doable with the wagovan tranny. Also have seen people do a 4WD CRX with the same transmission. I don't have a primer on it, but I do have a guy who can do the transmission work for me, just saving up to do it. Requires a couple of custom-machined gears, and final drive from an HF transmission, plus the entire transmission rebuild.

So, you'll need to buy:
Civic Wagovan transmission
Civic VX engine & computer
Wiring harness conversion kit
HF transmission
custom gears (.55 is "6th" and needs to be fabricated)
Oxygen sensor from Civic VX, wiring should be in harness kit
possibly a few other things

After this you get into custom parts like carbon fiber / fiberglass / aluminum hoods, doors, etc. Also the VX wheels are a good thing to use.

This will give you the highest mileage CRX.

Let me know if I can help in any other way.

The wagovan conversion sounds like a lot of work and money to invest but i'd like to see it when you are done...I am converting my CRX to 4WD using the rear of the wagovan along with a CRV trans and whole mess of custom parts...but thats not my FE project thats my power project ;)

Anyways I'll post a link that should help you, MPFI swap is fairly easy if you are car savvy, most civics will have the stuff you need to do the conversion (except for 88-91 DX) the 88-91 Civic/CRX SI and HF were both MPFI and anything 92+ is MPFI (92-95 is also OBD1) OBD1 civic's used saturated high resistance injectors where the OBD0 used a peak and hold low resistance injector (which requires resistor) you just need to make sure have the right ones for which ever route you decide to go...

A basic parts list:
MPFI Intake Manifold
Injectors x4 (and resistor box if needed)
MPFI Dizzy
MPFI ECU
Injector wiring harness for plugs

I couldn't see paying more then $100 for all of this and even less if you have a "U Pull it" yard near you, I'd say it would be $60 for all that at my local one, if you do decide to go with the D15z1 you should convert to OBD1 and the swap should include all the stuff you need, just have to do some wiring...

Any D series ("D" in the begining of the engine code) 88+ use the same bell housing bolt pattern and will bolt to your motor (1G integras had a D16a1 I'm not 100% sure if that would bolt to it but the trans frame mount is different so stay clear of that) I know for my 94 Del Sol I needed a Auto-Manual Conversion mount since the frame rail mount is different between the auto and manual chassis, I'm not sure about the EFs looking at a parts diagram it looks like the just used a different rubber mount for the top mount and a different bracket for the rear mount...to use a 92+ hydro clutch trans you will need a conversion kit...it should include the mount and a bracket that allows you use a cable clutch instead of the hydro, hasport sells a kit and I'm sure some other companys do too...Might be worth going that route if you find a complete VX swap, its probably easier to track down a CX/VX trans then an HF, most people were giving them away a few months ago but with gas prices now they might have gained some value...


FAQ section for EF Civics/CRXs
https://www.honda-tech.com/zerothread/1508680

HTH and GL

Thanks guys. I think for now that the wagovan and VX conversions are a bit more than I'm ready to do, but I'll probably keep my eyes peeled for the necessary parts down the road. For now I just want to drive the car. Maybe when I'm done remodeling my house and building my garage I'll throw some real time into the project.

For now, I just picked up a DX trans for $75 and I think I've found an HF final drive section to swap into it. My concern with the HF trans has been that the DX engine appears to be more of a revvy engine, and I was afraid that the mis-match would actually hurt more than it helps. I figure that for starters, a DX trans with an HF final drive will be a good compromise. The gears are a little shorter, but the HF final drive is so much higher than the DX that it should compensate for that pretty well.