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Discussion Starter · #1 ·
I am playing around with the idea of building a super efficient crx. I would like to get over 50mpg. But I don't want a stock Hf - 70hp is kind of little, and I want a newer more reliable engine.
What chasis / engine should I use?
I am thinking Hf (offcourse) with a d15 vtec-e from the vx. Should I even consider attempting this with my Si?
The 3 stage would probably be much better, but it seems like they are hard to come by, the ecu is rare, and they are obdII.
If you have some useful info or ideas on this, please post.
 

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Discussion Starter · #3 ·
Also, I'd like to keep total costs (if buying an engine and chasis) under $3000. So that rules out the hybrid. That and I would not be able to do it. I want to do most work myself, but I've never done a swap. Probably shouldn't be too complicated - d series to d series. The hardest part will probably be getting the wiring and ecu codes worked out.
 

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You don't have to get too fancy to get 50mpg from a CRX HF.
Stick with the 13" wheels preferibly some VX 13" and inflate the tires to 38 psi. Don't use the AC. Drive conservatively, don't do any fast take offs. I had for a long time a d16y7 with DX transmission on a 90HF. I got several times 50+ MPG on road trips by not going over 65mph, (cruised at 60mph) no AC and very easy on the gas pedal. easy.
 

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the first thing you need to figure out is what is your average speed going to be. are you going to be doing all highway? or are you going to have to climb hills often?

either way i would look at 88 89 crx hf

mostly all highway. get a vtec e engine with an hf tranny

lower speeds and lots of hills vtec e engine with a dx tranny

to wire up a vtec e motor and obd-1 ecu into an hf isnt hard at all.

scarponze
 

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You don't need an ultra conservative engine to get great fuel economy. I think Integra Type Rs are still rated at 32mpg highway, which shows that weight plays a more significant role.

You want to get the weight down as low as possible, so the best starting 2nd gen body would be an 88 HF. You can gut the interior of parts you don't need/use, and lower the car to reduce frontal area and clean up the aero. Then you just drive gently. Don't speed, don't accelerate or brake aggressively, shift to keep the RPMs as low as possible without "lugging" the engine.

I saw something on TV one time, a team of engineers got a Focus ZX3 up to 82mpg, and they didn't alter the drivetrain at all. They just gutted it, removed extraneous exterior accessories like the antenna, side mirror, etc. and covered the gaps with duct tape. Then I guess they drove it like gas was sold out. :)
 

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Check out this site... http://www.gassavers.org/forum.php. Several people there have put the VX engine in their CRXs. I found the site while researching the swap for my 88 HF, and I just bought a 92 VX last week. I'm planning on fixing it and driving it until I'm ready to do the swap.

The advantages of the CRX, specifically the 88 HF, over the Civic VX include lighter weight, taller gearing, and better aerodynamics, and I'm hoping combined with the better engine and ECU of the VX to get 60mpg.
 

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crxter said:
I got several times 50+ MPG on road trips by not going over 65mph, (cruised at 60mph) no AC and very easy on the gas pedal. easy.
One of the biggest and false myths out there about gas milage and running AC. I saw on television, i think on motor week some time ago, that running AC has almost NO effect or nearly no effect on gas milage.

If anything it should help you. Ac will keep you cool in the sunmmer on long road trips which keep you from rolling the windows down, creating drag and resistance. Keeping the AC on and windows up, you should get somewhat better milage.
 

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the 3 stage 5 SPEED p2j ecu is near impossible to find... and if you do they'll make you pay what an a6 is worth... i've been quoted $350 :shock:

The VX is the choice indeed... for mileage anyway!

Interms of weight affecting mileage, i've read different perspectives to this... and it depends on the type of weight too... i would say it affects city mileage alot more than highway mileage...

And i actually read an article that discussed the advantages of having your window down as opposed to A/C around the city... it was concluded that for city driving its more efficient to have your window down... on the highway its more efficient to run your A/C... due to the reduced speeds in the city, along with stop/go, you experience less drag than with the windows down on the highway (obviously)... Drag affects mileage significantly...

www.gassavers.com is a great place to research!
 

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Discussion Starter · #14 ·
The goal for me is to consistenty get 45+ mpg without trying hard. I drive conservative (slow) now. I rarely push it past 4k.
I guess my goal is the to have a car that gets great mileage and is practical for me and my girlfriend. I have a car and its great! I only drive it like 5k mi per year. My girlfriend has a 2000 VW Cabrio. Its expensive, not as reliable as a honda, hard to work on, and is not very efficient. So the car would be more for her/us than me. She won't go for the VX - its a bubble butt, I don't like them much either. Probably the easiest, and smartest thing for me to do would be to buy a Civic HX. Its fairly inexpensive (around 5-6k for a 97/98), should get over 40 mpg, and my girlfriend will be happy with it (maybe... she loves her Cabrio).
I've considered hybrids, but they are just too expensive, at least 10k.
 

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andrey320 said:
The goal for me is to consistenty get 45+ mpg without trying hard. I drive conservative (slow) now. I rarely push it past 4k.
You could easily get this kind of mileage in a bone-stock HF, but I can see not wanting 70HP -- but if you never take the car above 4k RPM, you're not getting much HP out of ANY of the Honda engines we swap into these cars. We've had long discussions about this before, but a lot of people claim to have gotten 40mpg with D16A6 or swapped engines (ZCs, etc.). I've gotten right around 40mpg on a DOHC ZC and a SOHC VTEC ZC (current setup), although the way I drive means I usually get "only" 33 or 35mpg. Why not run a SOHC engine like an A6, Z6, or the cheap DOHC ZC with an HF (or a hybrid) transmission?

With a focus on gas mileage, I think a lot of common setups could probably get you 45mpg. Run a really thin tire at a high tire pressure. Reduce weight as much as you can. Maybe fab up a light sheetmetal or coroplast belly pan to reduce drag, and smooth out the aerodynamics any other way you can. Remove the passenger-side mirror if your car isn't an HF (but a lightweight 88 HF would be the best starting point). Tune the car (mixture, timing, etc.) purely for fuel economy. Maybe even add on an external piggybacked air/fuel controller or have a chip burned with the focus on using less fuel, especially in the RPM ranges where you will be cruising. 45 is very feasible with a variety of engines if you can force yourself to drive that way and do a few simple tricks/mods to your car.
 

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Discussion Starter · #17 ·
Thanks for the input. I appreciate everyones opinions and advice. If I did not have a crx si right now and was looking for a car, I would deffinetely get an hf and drop a vx engine. But I have to be practical and economical (thats the goal after all). So I have to think long term. The car will be more for my girlfriend and a "family" car. So a crx is not an option. The cars left to consider are mostly hybrids and the civic hx. I know the coupe is not really a family car, but it does have a back seat and an airbag. Its also at least 2 times cheaper than hybrids. So now I just have to convince my girlfriend to sell her cabrio and we'll get an civic hx coupe. No swap needed, light wheels already there. Weighs around 2400 pounds. Maybe I'll be able to get it down to 2300 and do some aerodynamic improvements and tuning.
Any more hints on tuning for economy and making the car "slicker"?
Thanks.
 
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