imzjustplayin

I realize the HX weighs 100lbs more, has a lower speed ratio, and a 1.6litre engine over the 1.5 on the VX. I'm also pretty sure there are other changes but I don't know enough about civics to know. So, anybody want to help me figure out and or just speculate why the HX gets 10-15mpg less than the VX? I'm thinking that there could have been ECU changes as well for emissions. Biggest reason for wanting an HX over the VX is the HX is safer, how much safer, well it seems a lot more but I could be wrong. I was thinking that if the transmission in the HX is the largest culprit in the mileage, I could swap the HX tranny with a CX tranny from a '92-'95.

I do not own any civics yet, but I do have things in mind for changes I would do. The largest would be getting a 3 stage D15B engine and swapping it into what ever civic I want, second would be making sure I have a CX/VX tranny. I know that the likelihood isn't that good, even getting a CX tranny isn't that good either, so buying a car that I can live with would be necessary.

However, I'm not sure what price point for an HX/VX would have to meet to make the purchase of a DX,LX,EX at a lower price and then swapping parts into that be necessary.


please don't give up on my dream!

hushypushy

The VX is more aerodynamic (?) and has smaller wheels, which originally came with low rolling resistance tires (not sure if the HX had those tires too). Gear ratios probably play a part too. Hey, you said to speculate.

If you're gonna do a swap, that kind of negates the point of getting a VX or HX. In that case, I'd just get a CX hatch or DX coupe.

imzjustplayin

Well, part of the "risk" which sort of is equivalent to price (higher risk could mean higher price, like buying a $500 car "as is" could cost more than buying a safe $2500/$3000 car) and the risk is, not getting the parts, parts being no good, and me being unable to complete the swap successfully. Also I need to make sure I'd be saving money by going with any other model and getting the parts I need than going with the model I need and then "maybe" doing what I want to do.

I'm pretty sure it's going to be hard to get a 3 stage Vtec with ECU.

hushypushy

Well, don't take this the wrong way, but when you phrase it like that, you're probably better off just buying a car with the swap already done. You can probably get it cheaper, too--car + swap is usually less than a swapped car (check my sig for a prime example).

And I don't think I've ever seen a 3stage VTEC D15 for sale, so yeah, good luck on that one.

imzjustplayin

Right, finding a car with a 3 stage vtec would be very hard because it's JDM and most people don't care about fuel economy like I do. Since I'm not guaranteed to even get the engine, I want something I can enjoy as itself in the mean time.

thursday

how much does an hx actually weigh? My bone stock 93 vx weighed in just shy of 2000 lbs w/o me in it with a full tank of gas, does the hx really only weigh 100 more lbs? I'm skeptical.

imzjustplayin

No, the HX over the VX does in fact weigh more like 200lbs more.

http://autos.msn.com/research/...id=-1
http://autos.msn.com/research/...id=-1

But if you compare against a similar model like a hatchback/hatchback or coupe/coupe, you can see either small (less than 100lbs increases) to less than 200lbs increase. CX hatchback '95 manual, 2108lbs, CX hatchback manual '96 2222lbs. Though the DX Coupe '96 manual is 2231lbs while the DX coupe '95 manual is 2262lbs, so there was a weight decrease. It really depends, but thanks for asking that question as I did not notice that the Coupe weighs more than the hatchback.

hushypushy

Something else to consider...

https://honda-tech.com/zerothread?id=150315

hondaman1212

IVE SEEN PLENTY OF THOSE 3 STAGE VTEC D15S OUT SEARCH ON GOOGLE YOULL FIND ONE.

suspendedHatch

The D15B aka D15Z7 motors are quite common. Many importers don't know what they are or don't tell you what they are. But if it looks like a D16Y8 but with two VTEC solenoids and EGR then it's a 3 stage. I got mine for $600.

Don't search for "3 stage VTEC" or "dual VTEC". The people that list them under those names are trying to charge $800.

The P2J ECU however is quite rare. It's only rare because importers are too stupid to pull the ECU when they pull the motor. I'm running my motor on an AEM EMS.

The federal VX used a wideband O2 to run extremely lean. The CA VX did not. The HX does not, and the D15Z7 does not.

The D16Y5 and D15Z7 came paired with either a 5 speed or a CVT, and the CVT's performed better and got better mileage.

However I bet that if you put a D16Y5 into a VX you'd get similar mileage to the CA D15Z1. I'm currently getting 35mpg mixed driving (44mpg highway) out of my D15Z7 swapped VX with a LSD tranny (shorter gearing), AEM EMS and an AEM UEGO but I have a lot more tuning to go. I don't drive it like a grandma. I'm getting 119whp by the way.

teal_dx

The HX's equipped with a CVT did not have wideband o2 sensors. HX's equipped with a 5 speed did come with a wide band o2 sensor.

Relic1

VX vs HX
weight
lean burn still present in HX but a shadow of VX's version (hence need for wideband)
gear ratios longer in VX trans (lower RPM on highway)
aerodynamics not as clean on HX
options standard on HX makes it heavier and pull more power from the engine
1.6L VS 1.5L


if you're trying for mpg (hyper-milling) pick up a stock 92-95 VX (fed spec, not cali spec)
do some slight mods to help with aerodynamics even more and drop the car an inch.
Keep the rims and tires stock and drive the wheels off the thing.
55-60mpg highway is not unheard of on a stock VX.

randerson0248

Because of stricter emission requirements the HX is not quite as lean as the VX.

randerson0248

I would think that the transmission has the least to do with the difference. The HX has taller tires, which makes up for some of the gearing difference.

imzjustplayin

I was looking at the MPG rating of the 49 state VX, california VX and I believe the 50 state HX. There is about a 7mpg drop in fuel economy I'd say from the federal VX and the california VX then there is a 5 mpg drop from the california vx to the HX. Now I'm thinking that the reason for the lower drop is because the HX which I think is 50 state has the same lack of agressiveness in lean burn as does the VX from california. I know the HX has shorter gearing, heavier, and a 1.6 litre engine so I think that is what the 5mpg is, from the California VX at least.

Now I was thinking, what exactly prompts the ECU to enter into lean burn? Is the initiation of lean burn in the ECU for all the cars done by what the O2 sensor says or does the O2 sensor simply tell the ECU whether to enrich or lean the mixture? If it's the latter, then wouldn't it be possible to simply make the ECU think it's richer than it really is, ever so slightly, so that it effectively brings it back to the lean condition of what ever you'd get with the federal VX?


or...

Tune the HX ECU so that it supports a 5 wire O2 sensor and support leaner conditions?

Relic1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by imzjustplayin &raquo;</TD></TR><TR><TD CLASS="quote">I was looking at the MPG rating of the 49 state VX, california VX and I believe the 50 state HX. There is about a 7mpg drop in fuel economy I'd say from the federal VX and the california VX then there is a 5 mpg drop from the california vx to the HX. Now I'm thinking that the reason for the lower drop is because the HX which I think is 50 state has the same lack of agressiveness in lean burn as does the VX from california. I know the HX has shorter gearing, heavier, and a 1.6 litre engine so I think that is what the 5mpg is, from the California VX at least.

Now I was thinking, what exactly prompts the ECU to enter into lean burn? Is the initiation of lean burn in the ECU for all the cars done by what the O2 sensor says or does the O2 sensor simply tell the ECU whether to enrich or lean the mixture? If it's the latter, then wouldn't it be possible to simply make the ECU think it's richer than it really is, ever so slightly, so that it effectively brings it back to the lean condition of what ever you'd get with the federal VX?


or...

Tune the HX ECU so that it supports a 5 wire O2 sensor and support leaner conditions?</TD></TR></TABLE>
the P07(VX ECU) uses the wideband to control the leaner mixtures, the ECU enters lean burn mode when all the conditions are correct. (low throttle position, over a certain mph, no CELs, etc) Unfortunately I don't have a VX anymore to play with to try to map out what actually has to happen for it to run lean like that.

Logically you could run a wideband with an adjustable narrowband output to make the ECU think that 15.5:1 is really 14.7:1, but you'd also have to keep the EGTs in check by adding ignition timing to compensate for the leaner mixture.

The HX ECU is not tune-able. (neither is the 49-state P07)


eCtune and crome both have the option of reading a wideband for closed loop operation, the option to properly follow the lamda table in closed loop is in the works. So essentially you could have the ECU run any mixture you want where ever you want in the maps.

imzjustplayin

So why would the 49 state VX ECU not be tunable just like the HX ECU? The california VX ECU is tunable though? Is the reason why people like OBD-I civic is because they're more tunable than OBD-II?

baller status

The 49 state P07 has a wideband controller built in and thus a different board than the rest of the OBD1 ECUs. I have read also that the entire code (language?) is different. But this is not my area of interest so I digress.

The ECU determines when to go into lean burn mode based on coolant temp (must meet a minimum requirement), engine load, and RPM.

The wideband O2 is used to monitor and correct the mixture, not initiate it.

Tricking sensors is not a good way to alter AFR. For one thing, O2 feedback will correct the mixture back to what the ECU wants.

You would never want to make a blanket change to AFR anyway. Running lean under certain conditions is not only dangerous for your engine, but may also reduce fuel economy.

AFR is only part of the FE equation. Big changes in AFR require a change to ignition timing advance.

There's a collection of VX fanatics over at http://www.gassavers.org