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Old 05-14-2008, 01:44 AM   #1 (permalink)
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Beater Deluxe v2.0 - '89 Honda Civic DX
90 day: 44.68 mpg (US)
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Yaaaar!

Hi, I like cars.

I have a 305K mile 89 Civic DX, running a D15B7 and OBD1 ECU. She's an old, battered thing that burns oil atrociously. The pertinent figures are 26 mpg city (2700 ft elevation/mountains) and today she netted 39 mpg on a flatland roadtrip.

I've had good luck with getting stock or better FE out of EFI cars with big cams, and am considering going that route with some aero work, see if I can hit 45+. The basic idea is 12.5:1 CR, Crower stage 3 or Zex 59300, free/cheap exhaust, no real portwork or anything of that sort because I am lazy, will net a whopping ~140 whp. I'll keep the dog DX box.

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Old 05-14-2008, 09:20 AM   #2 (permalink)
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What kind of conditions are you looking to hit 45 mpg in?

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Old 05-14-2008, 10:55 AM   #3 (permalink)
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CM400E - '81 Honda CM400E
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Welcome to ecomodder. 40+ should pretty much be a piece of cake in the car with a few changes in driving style, and 45+ shouldn't be too hard either. Definitly look up the tips posted by SVOboy. You should be able to hit that 45+ with just driving changes.

Big cams are actually very detrimental to mileage. It shifts your powerband higher than you should ever really use if your driving to get good gas mileage and reduces power where you need it, low rpms.
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Old 05-14-2008, 01:22 PM   #4 (permalink)
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Beater Deluxe v2.0 - '89 Honda Civic DX
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I want to hit 45 in a highway cruise, flatland. Since I have a creaky wheelbearing causing some drag, etc, I figure it's setting the bar low. Unfortunately 70% of my driving is short distance, in town, mountainous... I'd be very happy to get 30-32 in town.

Daox, disagree. A stock B7 cam is a loss of power over all operating ranges. Also, whether I am getting more or less airflow at a part throttle cruise and at a given rpm due to a cam change is also irrelevant as I am not travelling at WOT. Since horsepower can be expressed as airflow, I merely tailor my throttle angle to the power (airflow) level needed to maintain a highway cruise. Tuning AFRs and timing in the cruise region, especially if the car wants to cruise at a lesser vacuum where the ECU attempts to lodge itself in open loop, is critical... if I was not able to tune the setup, though, you are correct a cam swap would net a pretty big FE loss.
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Old 05-14-2008, 01:36 PM   #5 (permalink)
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I see where your going with the cam. I guess thats just not the way I'd go about it, especially since I use pulse and glide. For steady state cruising I see your point.
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Old 05-14-2008, 06:04 PM   #6 (permalink)
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Joseph -

Welcome to EM! You should post some pictures of your car so we can aero-modify it up the ying-yang.

Wiki wiki wiki ... does it look like this? :



Hmmmmm, there seems to be a 6-speed tranny for this generation (but I don't know if it has a good ratio) :

Honda Civic
http://en.wikipedia.org/wiki/Honda_Civic
Code:
Engine(s) 	
1.3 L D13B I4
1.4 L D14A I4
1.5 L D15B I4 (yours)
1.6 L D16A6 I4
1.6 L B16A I4

Transmission(s) 	
4-speed manual
5-speed manual
6-speed manual
4-speed automatic
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Old 05-14-2008, 07:46 PM   #7 (permalink)
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LOL, no it's a run of the mill metallic blue hatch. The only pictures I seem to have of it are in the background, behind other cars/objects. I'll try to get some, though, I'm curious as to the suggestions I'll receive.

FYI the 6 speed is a RT4wd unit, The extra gear is down low and is meant as a granny first gear for traction in an offroad environment. If the design isn't too alien from the normal FWD units there is a chance it could be fitted with a taller final drive out of the STD/HF, but I'm not crossing my fingers on that.
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Old 05-14-2008, 08:33 PM   #8 (permalink)
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Joseph -

Rats on the tranny but Kudos on the hatch. I really like that design. IMO, the built-in spoiler was always such a clean design element. Maybe you could extend that spoiler out into a Kamm-back after you have established a baseline MPG. Since you are pre-OBDII, you may want to look at the guino real-time MPG calculator project :

guino release one workspace
http://forum.ecomodder.com/showthrea...15.html?t=2115

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Old 08-22-2008, 02:38 AM   #9 (permalink)
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Beater Deluxe v2.0 - '89 Honda Civic DX
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I ended up not going with the cam, and ran a stock Civic HX head instead, effectively making my engine a beefier variant of the Civic GX's. Prurient details below:

D16A6 block
- LS rods
- GX pistons (12.5:1 CR when mated with a Y5 head)
- ACL bearings

HX aka D16Y5 head
- Called "VTEC-E 2" in the OEM parts literature
- roller rocker design

Induction
- D16Y8 intake manifold
- GSR 60mm throttle body
- future plans for a filter on a stick

Exhaust
- DC sports 4-1 header (I wanted 4-2-1, but it was free so meh)
- 2.5" exhaust off a wrecked car. Looks like high end muffler shop work, has cat built in.

Transmission
-ZC/Si hybrid, close ratio 1-4th with a .702 5th gear. Gearing equivalent to an Integra Hype-R, but I cruise in 5th gear 2000 rpms @ 45 mph/3000 rpms @ 70 mph.
- 12 lb flywheel for less rotational inertia (it came with a super low mileage OEM clutch for $75)

Control/misc
- eCtune to fiddle a 92-95 Civic/Integra ECU as I see fit
- 14point7.com JAW wideband for use in a closed loop lean burn system (installed but not enabled yet)
- water injection (pending)


Points of interest:

My IAT is fried. It reads 8-30 degrees F, which explains why the lean burn setup on the old stock B7 got stock (39-40) mpg where others gained 5-8 mpg from fiddling around like I did.

In the interest of thriftiness I decided to tune on 87 octane. I had some pinging at WOT below 1500 rpms due to software limitations keeping me from firing the mix any later than 6 degrees ATDC. I retarded the distributor and fudged the ECU mappings, found the pingies went away at 9 ATDC. Timing in that region is now set to 11.5 ATDC until I dyno the car next week. Power is acceptable, probably excellent given what the engine is. I estimate an amazing 115-120 whp.

I have 130 miles on the setup including some hellraising to seat the rings, a dozen and a half WOT pulls to set AFRs, and a 100 miles of cruising at 75-80 mph. My half tank mileage is 40.1 mpg, and the ECU is in open loop, haha. I'll implement lean burn closed loop, monitor mpg/bsfc both in and out of VTEC, and eventually install water injection. I'd like to do a front lip for aero reasons but I suspect I'd tear it off with how I use the vehicle like it's a truck.
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Old 08-22-2008, 07:54 AM   #10 (permalink)
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high compression vtec-e

very interesting project, but the tranny may hurt you a little for highway cruising if your looking for max fe

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