Best Mod to Date - Trans Swap (1997 Civic HX)

[Cobb]

Give up? I think you are doing excelent in mpg for such a vehicle going 70 mph.

Short of buying a prius 3 or a few other vehicles on the road, you cant beat that. I rented a prius 3 for a week and could maintain 50 mpg doing 70mph. Doing over 70 in my geo metro I was under 40 mpg.

[PAFirefighter11]

Originally Posted by Cobb

Those guys are ---king stupid. If they knew anything about volumetric efficiency they understand the gearing part and driving WOT. You want to lug the engine to at least 80% if not engage the lean burn if equipped for mpg.

Since I just woke up I'm not sure if this is sarcasm or not lol... I shift prior to the upshift light engaging. I'd assume that's only around 20% or less.

[Xist]

Originally Posted by PAFirefighter11

I finally had some free lift time so my buddy and I swapped the stock trans back in (It was included separate with the car)

Do you think you ever would have considered this had the HX transmission not been free? I forgot this part and wondered if you would have considered the previous generation's CX\VX transmission.

[PAFirefighter11]

Originally Posted by Xist

Do you think you ever would have considered this had the HX transmission not been free? I forgot this part and wondered if you would have considered the previous generation's CX\VX transmission.

CX/VX models are hard enough to find around here, let alone their parts. HX's are more popular and thus a better salvage yard market for them. I would have researched it prior, I'm sure, but most likely would have done an HX trans anyway.

[slownugly]

I have 2 trannies sitting in my shop along with enough parts to build 3 lean burn cars. If you ever have the trans out again and want to consider it give me a shout.

[PAFirefighter11]

Originally Posted by slownugly

I have 2 trannies sitting in my shop along with enough parts to build 3 lean burn cars. If you ever have the trans out again and want to consider it give me a shout.

Thanks for the offer! I'm assuming the VX is geared even lower than an HX? And the main cause of the better VX FE is due to weight and gearing? 2094 lbs for the VX versus 2339 lbs for my HX.

I do see a CEL light every few hundred miles. P0420. Which, in my experience, is either a cat or upstream o2. Do you happen to have either or both of the above laying around that'd work with my HX if I so desire to replace them?

[slownugly]

Yea the vx tran is very low. I'm at 2k at about 65mph. It's becoming a popular swap with hxs. I believe it requires some driving style changes so a scan gauge would help a lot. I think it allows more flexibility with lean burn because guys were having trouble keeping their hxs in lean burn. I've never driven an hx so do some searching around. One build In particular was returning 60+ mpg.

Yea the 420 is a cat code. I've never seen an o2 cause a cat code. If an O2 is staying lean or rich it would throw a code specific to that. If you've ever seen data pids for oxygen sensors the front sensor normally switches between .2-.8 volts. The rear o2 looks for a change in voltage which indicates a chemical reaction and the converter is working properly. If both voltages are identical or almost identical it will throw a cat code because the ecu senses that the cat is no longer performing a chemical reaction. Check for exhaust leaks too. That may have the capability of throwin the code.

Our wideband o2s do not operate in the normal .2-.8 range but the cat monitoring is the same principle. I have 1 cat attached to one of my engines but I'm pretty sure it won't fit the hx.

Edit: plus the chemical composition of it is pre obd2 so it would likely throw a code even if it fit.

[PAFirefighter11]

Originally Posted by slownugly

Yea the vx tran is very low. I'm at 2k at about 65mph. It's becoming a popular swap with hxs. I believe it requires some driving style changes so a scan gauge would help a lot. I think it allows more flexibility with lean burn because guys were having trouble keeping their hxs in lean burn. I've never driven an hx so do some searching around. One build In particular was returning 60+ mpg.

Yea the 420 is a cat code. I've never seen an o2 cause a cat code. If an O2 is staying lean or rich it would throw a code specific to that. If you've ever seen data pids for oxygen sensors the front sensor normally switches between .2-.8 volts. The rear o2 looks for a change in voltage which indicates a chemical reaction and the converter is working properly. If both voltages are identical or almost identical it will throw a cat code because the ecu senses that the cat is no longer performing a chemical reaction. Check for exhaust leaks too. That may have the capability of throwin the code.

Our wideband o2s do not operate in the normal .2-.8 range but the cat monitoring is the same principle. I have 1 cat attached to one of my engines but I'm pretty sure it won't fit the hx.

Wow, 60+ on an HX? That's insane. I'd be happy with 50. I may have to consider selling the HX trans for one of your VX's.

Thanks for the info on the o2's/cat. My scan tool doesn't read quick enough to see the switching, so I need to go to my buddies who has a nice Snap-On scanner (He's a Master Tech) if I ever need to check that. I'll start looking for a new cat at this point.

I'm still trying to do some grill blocks, rear bumper underblock, better front lip once I raise the car, and fix some stock aero issues (Removal of mud flaps, new driver side fender liner as it's missing, fix a rust hole, etc.). Having so many vehicles, a house, a fiance, and a Husky that's accident prone makes any mods hard to afford!

[slownugly]

It was a 96-00 cx hatch with an hx engine/vx tranny. Very awesome combo. The car was in the for sale section. Its probably a little lighter than the hx but weight savings isn't everything. I embrace the weight in my sedan. It helps me coast better than my vx. And with the vx drivetrain it still returns 50+mpg. Now I'm just rambling.

Yea he should be able to tell quickly if it's the cat. Remember it's a wideband o2 upstream so the voltage is going to be different than the .2-.8. If you couldn't tell I'm a tech as well and have a small 2 bay shop.

I hear ya. I'm in the same boat as you. I work in the Bethlehem area but I live in Scranton. I have the same mods planned for my sedan but it's just a pain to find the time to do them. I'm going to make a custom winter/summer front bumper. It will be fully closed in the winter and have a removeable panel by the rad for the summer.

[PAFirefighter11]

Originally Posted by slownugly

It was a 96-00 cx hatch with an hx engine/vx tranny. Very awesome combo. The car was in the for sale section. Its probably a little lighter than the hx but weight savings isn't everything. I embrace the weight in my sedan. It helps me coast better than my vx. And with the vx drivetrain it still returns 50+mpg. Now I'm just rambling.

Yea he should be able to tell quickly if it's the cat. Remember it's a wideband o2 upstream so the voltage is going to be different than the .2-.8. If you couldn't tell I'm a tech as well and have a small 2 bay shop.

I hear ya. I'm in the same boat as you. I work in the Bethlehem area but I live in Scranton. I have the same mods planned for my sedan but it's just a pain to find the time to do them. I'm going to make a custom winter/summer front bumper. It will be fully closed in the winter and have a removeable panel by the rad for the summer.

Hmm, that does sound like a great combo. Do you have any other FE mods or just that trans swap that got you into the 50's?!

I have a post up seeing if anyone else has a personal experience of doing an HX to VX trans swap and what the FE increase was with just the swap. If it's beneficial enough and can get me into the mid to upper 40's, or low 50's at the very least, I'm going to do it.

For reference purposes:
96 CX manual is 2222 lbs
97 CX manual is 2304 lbs
98 CX manual is 2295 lbs
99 CX manual is 2395 lbs
00 CX manual is 2395 lbs

So not too far off from the HX models.

Could definitely tell you're either a tech or well versed in automotive information. Either way, it's good to see someone with a lot of first hand knowledge out there.

Ouch, that's a long commute! I do 63 miles round trip (Springfield Township, MontCo. to West Chester, ChestCo). 90% highway and during off peak hours which eliminates traffic barring an MVA. That block you're talking about is exactly what I am planning as well. I'm excited to get something done, but as you said, free time is a PITA to find!