Understanding the '92 - '95 Civic CX and VX

[manderson99]

What were the major differences between the CX and VX Civics between '92 and '95? I understand that the engines were different (d15b8 for CX, d15z1 for VX), but what else? Didn't the VX have 13" alloy wheels or something, and if so, what did the CX have at stock?

I don't own a Civic yet (this is still up in the air) so I'm a bit new to the models and their differences, so any help for this nub would be appreciated. Thanks!

 

[phyregod]

They are both economy models with next to zero horsepower, but they both get incredible gas mileage.

I know the VX had aero mods, such as a rear diffuser. It also has Vtec that is tuned for fuel economy instead of power, and also has a Lean Burn mode that allows the motor to run very lean while cruising, which sips gas. As well as roller rockers to reduce rotating resistance in the motor. The CX has none of this, but still achieves incredible fuel mileage.

The VX has 92hp, and the CX has 70hp. The CX, I know from owning one, is horrible to drive. Less pep than a 3hp go cart.

 

[manderson99]

They are both economy models with next to zero horsepower, but they both get incredible gas mileage.

I know the VX had aero mods, such as a rear diffuser. It also has Vtec that is tuned for fuel economy instead of power, and also has a Lean Burn mode that allows the motor to run very lean while cruising, which sips gas. As well as roller rockers to reduce rotating resistance in the motor. The CX has none of this, but still achieves incredible fuel mileage.

The VX has 92hp, and the CX has 70hp. The CX, I know from owning one, is horrible to drive. Less pep than a 3hp go cart.

Interesting, so the VX has a modified body for lower CoD? I knew the engines were different (non-VTEC vs VTEC-E) but that was the only thing of which I was aware.

So a CX could probably get very close to a VX's fuel economy with a d15z1 swapped in? From what I've heard/read, they seem to have the same transmission.

As far as aero is concerned, well, there's always the Aerocivic mod.

 

[K2e2vin]

The only VX aero mod is the rear diffuser IIRC. Otherwise, the VX is basically a CX with a motor swap.

Yes, the transmission should be the same. They're both very long and obviously biased towards low-rpm cruising.

 

[eg6sir]

rear diffuser?? my vx didnt have one... but i'm sure it had been molested and removed before i got it

but yea, basically the same car.. oh and the VX came w/ a tach in the gauge cluster, the CX didnt

 

[K2e2vin]

May have been an VX-only option then.

Also, I forgot about the VX wheels! They're lighter than the steelies on the CX.

 

[phyregod]

I believe the CX gets better mileage than the VX did. The VX was more of a super efficient DX kind of a thing, where the CX was a stripped out base-economy model made for nothing but good gas mileage.

And the rear diffuser wasn't anything special or beautiful, It wasn't a ferrari style thing.. it was just a plastic piece that kept the rear bumper from scooping air. You could easily fabricate one with coroplast and rivets. Coroplast is that plastic that looks like corrugated cardboard, and is used for cheap signs, etc.. Readily available from any sign shop, and super cheap.

If you are looking to make a Hypermiller, you should hit up Fuel Economy, Hypermiling, EcoModding News and Forum - Ecomodder.com Fuel Economy Forum
Those guys are bat shit insane with mpg tips and tricks. Front and rear diffusers and a grill block can really cut down the cd of a car.

If you are going to buy a car for hypermilling, I would certainly go for the VX. You can do things to that motor that make it amazingly efficient, re-tuning it, keeping it in lean burn, etc.. A vx motor in a crx makes for a 60 to 70mpg rig.

 

[josh_crewdson@y]

roller rockers? please... d series didnt come with those...

 

[manderson99]

Thanks for the feedback!

phyregod, if I can get a CX at a decent price (something that seems rather difficult), I will probably have a d15z1 dropped in there for good measure and go from there. I'm actually very interested in having a 3 or 4-lobe roots supercharger slapped on the d15z1 if it can be done at a reasonable price (which is questionable). Call me crazy, but I have my reasons . . . and I'd only want maybe 6-7 psi of boost anyway.

Aero is something I'd look at after getting the engine squared away, but I've got boatloads of help in that department.

 

[K2e2vin]

If you're going boost, it's better to go with turbo as you can still retain just as good(or even better), mpg. There's some guy hitting like over 50mpg IIRC with about 230whp on a boosted D15 or D16.

 

[Briansol]

does the vx have a rear wiper? i know the cx doesn't.

 

[manderson99]

If you're going boost, it's better to go with turbo as you can still retain just as good(or even better), mpg. There's some guy hitting like over 50mpg IIRC with about 230whp on a boosted D15 or D16.

Normally I'd agree with you. The parasitic losses from running a turbo are lower, too.

However, the goal would be to try and get the engine under boost at the low end. One option would be to go the route this guy mentioned in his speculative post:

Using boost for mileage [ Archive] - GasSavers.org - Helping You Save at the Pump

Not sure how much trouble it would be to go with low-compression pistons in a VX engine, but that sure sounds like an interesting idea.

There are other reasons why I'd like to tinker with boost in the low-end but that's another story altogether.

 

[K2e2vin]

You can boost on the low side with a turbo, too. Simply, just use a (very)small turbocharger. I've seen one somewhere, came out of some European car(Audi or VW I think) but it was pretty small and would probably fit the bill well. May have been a T15 or something equivilent.

For reference, far left is a T15(with battery on it)

and some specs: http://members.iinet.net.au/~johnh/garrett2.htm

Don't bother lowering the compression; the Z1 pistons are already dished and since you're not running high boost, it should not be a problem(FYI, the Z1 pistons are probably the lowest CR D-series pistons). You'd probably lose efficiency doing that anyway(from a performance standpoint, lowering the static compression just allows you to run more boost safely; but since 6-8psi is the goal that's really not a huge concern).

As stated before, someone is already running a high-mpg turbo setup. I'll try to find the thread for you.

Here it is: *64mpg and biased towards performance: http://www.d-series.org/forums/forced-induction/117099-i-did-some-fe-testing-64-8mpg.html

 

[K2e2vin]

Just thought I'd add this in here since I've thought about doing it something similar to you: Use motorcycle injectors(Denso's, like ones from a ~99 TL1000R or CBR600), bump up pressure to compensate flow, and see if you can angle it more towards the valve that fully opens during VTEC-E operation.

Bike injectors seem to have better atomization properties(multi-hole type) and bumping up the pressure helps with atomization also.

 

[manderson99]

That's a lot to chew on, thanks! I have slightly different goals in mind than rrussell, but it just goes to show that you can go a long way with a lean tune. That's a And thanks for the pointer on the T15 and the bike injectors. If I could get a T15 to spool up by 1500 rpm then that would suit my needs nicely . . . maybe that's asking for too much, maybe not, but running a turbo would be preferred.

Not sure if the bike injectors idea is economically feasible but I'll be sure to look into it. Injectors shouldn't be too expensive, I wouldn't think. Especially not small ones.

Also, it seems that you've pretty much answered my boost questions, or at least set me in the right direction . . .

 

[phyregod]

Lean burn + a turbo would certainly blow the motor to bits!

 

[K2e2vin]

Lean burn + a turbo would certainly blow the motor to bits!

You check out that FE thread on D-series? Guy is running about 18:1 AFR lean; he said he went as far as 20 or 22 IIRC. but pulled it back just in case.