druidesque

I just acquired a 97 Honda Civic 4dr.

It had a blown motor...so i swapped it for an hx longblock (e-vtec).

However, since i wanted to do this swap on a budget (i have less than 1000 total into the car) i swapped everything from the d16y7 onto the longblock.

Basically, the setup is as follows.

Hx longblock.
d16y7 (non vtec) intake manifold, distributor, exhaust manifold, stock intake, stock ecu.
No cel's, stock exhaust, stock everything else including new air filter.

Auto transmission with 86k miles on it.

Otherwise, the car is 100% stock, all accessories including ac, power steering.

What kinda mileage do you think i can get out of this car?

If the ecu setup doesn't work well and mileage is poor I will run a non-vtec head...just curious to see how this setup will do...

Linked

i never knew there was a 100% surefire way but i always do this

find out how big is your gas tank (my eg was like 11.9)

fillup

reset your tripmeter

drive highway or drive street

when you run out (you wont run dry but wing it for the most part), read your tripmeter

divide that by your gas tank size (11.9 for me)

thats your MPG

i usually get about 340-350 highway on my ex (auto trans at 80mph)

350/11.9 = 29.4 MPG which is low for highway miles,

i need to do a tune up

94EG8

Meh, the only way to get good mileage out of an HX engine is to use the complete HX setup including the wideband O2 sensor ECU and a manual tranny. (only the 5 speed HXs used a wideband O2 sensor) It will get half decent mileage but it wont be anything spectacular. To calculate mileage, fill the tank, reset tripmeter, drive till you've used at least half of the tank. refill (preferably at the same pump) divide the number of gallons pumped by the number of miles on the trip meter.

Vindicator9000

hrm. yeah, I think I agree with him ^^

What ECU are you planning to use? I would think an auto HX ecu won't work right on a non-CVT transmission, and a DX ecu won't run the vtec-e right.

Yeah, convert it to manual and wideband, and I bet you could get damn near 40mpg on it. I used to get 38 on a stock manual 2000 EX. As it is, I suspect that you're going to be chasing CELs until you get sick of it. If everything did work right, I don't see why you couldn't get 35mpg+ out of it... maybe as much as 40.

Really though, 70% of mileage depends on how you drive. There's a guy on here who's getting close to 40mpg with a B16 engine/transmission. I get about 30 average/ 32 high on a gsr with a B16 transmission, which is very good considering I still wrap it to 8100 a few times per tank. In fact, I'd almost guarantee that I can get better mileage than most people given the exact same car.

You just gotta be disciplined and know the tricks. Pulse and glide behind a semi works wonders, as does never using your brakes.

Oh, and get a scanguage. It will *REALLY* open your eyes to how your driving habits affect your mileage. Plus it'll let you clear CELs! Woot!

honda.lioness

Curb weights an HX and 4-door DX differ by only 5 pounds, per kbb.com.

From fueleconomy.gov --
HX, vtec-e, you have the engine
29/35 (31) gov test, city/highway
individual reports, 3 reports: 32/37 (34.7), hi/lo

DX, non-vtec, you have the dizzy and ECU
25/32 (28)
13 reports: 22/36 (31.2)


The non-vtec ECU is going to "lock in," so to speak, a single cam profile for each valve, as though it were running a non-vtec engine. How does the locked in vtec-e cam profile compare to the non-vtec engine's cam profile, for one?

I would aim for the DX fuel mileage but not be surprised if it were worse.

ruthless013

you're close.

fill tank to max, reset trip.

drive.

stop for gas when you see fit. note mileage on trip.

fill tank to max again. note how many gallons you just put in.

divide miles by gallons.

reset trip. start again.

druidesque

A few notes.

First, the car is together and running and does not have any CEL's. I used everything from the DX setup including all sensors, wiring, etc...

The only difference is that the DX ecu will not be capable of running vtec.

My understanding is that hx vtec motors are designed to engage vtec at 3000 rpm for maximum efficiency.

If i'm conscious about not running over 3,000 rpm i'm thinking the cam profiles will be very similar to that of the DX cam which is what came out of the car.

Kista20

From what I can tell your mpg's should be right there with the y7 and any difference would be negligible. With my 97 hx w/ 5 speed I usually avg. around 40-43 mpg. So did you use the whole y5 engine but with the y7 im, tb, harness, and ecu? Difference's that I know are different would be the egr, 5 wire o2 sensor, and exhaust manifold.

If I had to guess I would say you will be in the mid 30's around 33-35 at best... the automatic isn't the greatest when it comes to fuel economy.

98civdx

my auto y7 gets 22-25 with mixed street and highway,

druidesque

Everything is DX except the longblock itself. I switched over every sensor including the intake and exhaust manifolds.

Basically, the vtec cam will never be activated because of the DX ecu/harness.

I will keep everyone posted on the MPG results.

tazeat

Your using the wrong fuel maps with the DX ECU, but since you kept the DX auto tranny you have no choice. Although closed loop + partial throttle the maps are probably close enough, the no vtec-e at the 3000ish rpm mark is going to make it a gutless engine though. I hated the HX engine as it comes stock when I had it, not even getting vtec-e at 3000 I think it would be worse. I ended up getting worse gas mileage since I would drive it so much harder.

But I'm guessing low 30s completely depending on your driving style.

Kista20

actually vtec-e comes in at 2700 rpm. The op has a good powerplant that has potential for some pretty good mpg's and just needs to finish out the conversion for it to become a 4 door hx. I like my y5 and I'd much rather have it than the anemic y7.

tazeat

It actually uses a different rpm value based on high or low load as well if you want to get picky.

Regardless it's still terribly slow and the fuel maps and vtec engagement still will not be right anyway with that ECU.

druidesque

I don't mind having a motor with no power...as long as i'm getting good fuel economy.

I figured the two ecu maps would be off...not sure if its to the point where it'll make a difference.

The results will be interesting...as I'm going to do my best to get maximum fuel economy out of it.

alphalanos

I get around 30mpg mixed highway/city in y7 auto. highest was 35mpg all highway.

druidesque

I'm also looking to run vx wheels w/ smaller tires.

I'm thinking they'll be best for maximum efficiency.

Kista20

the hx's are 14" but the vx is 13"

personally imo 14's are much better looking than 13's.

tazeat

Smaller tires? As in diameter so you will rev higher on the freeway? wat?

druidesque

I should have been more specific.

By smaller I meant thinner. VX rims are super light and with 13inch tires they'll provide less resistance going down the road. As far as diameter, I want to run as close to stock as possible.

98civdx

hx's are super light as well, and look better then 13's any day.

druidesque

I know, 12lbs vs 9lbs...the differences are probably close to zero.

If i find a clean set of hx wheels with good tires i'll run them.

druidesque

I picked up a set of vx wheels today. Super light and the car handles great...but I'm not sure I like the way the car looks.

druidesque

Just filled the car up for the second time after running through the old fuel.

(i don't drive much)

I went 99.6 miles.

2.71 Gallons.

MPG = 36.75.

I still need new spark plugs and I'm going to bump the tire pressure up. One other factor to consider is this.

Stock tire size for a civic (i think) is 185-65-14.

I'm running 205-60-13's on the VX rims.

The difference is 3.3%. According to miata.net tire diameter calculator the car is going 58mph when speedo says 60mph.

Doing some simple math.

58mph/60mph x miles/99.6 miles.

X = 96.28.

96.28/2.71 = 35.52 mpg.

So, I'm probably getting between 35 and 36mpg.

This is with AC running 75% of the time on 1st or 2nd fan setting...not taking the car over 2800rpm...no sudden starts...etc.

I want to get 40mpg...which probably isn't possible with the auto trans.

lponcian5799

drop that bish.

98civdx

it looks goofy...
lower it please.