93 Honda Civic VX horrible fuel economy

[benfrogg]

Imjustplayin-
How do I know if the tranny is hydraulic or cable operated? Would the cable operated HF bolt up to the D5Z1 block? This is definitely a D5Z1 block. It is also definitely the federal model.

On your website, which tranny represents the VX and which represents another like the DX? That's the transmission I assume that I have. The tires are 165/70 R13. (stock size)

What is throwing me off and telling me it's not a VX is what PDXCHRIS gave for numbers of his car that was getting better MPG, the red one. Assuming no one changed out his final drive (which is certainly possible), then my transmission is not the stock version. Is it possible that the vx came in a high altitude version?

So, all VX'ers and DX'ers, would you be so kind as to give me some data about rpms and mph? That would be super handy!
Thanks
B

[GasSavers_Erik]

cable or hydraulic refers to how the clutch is disengaged- ie. what type of connection there is between the release arm and the clutch pedal- a wire cable or a hydraulic line.

[benfrogg]

This is definitely a hydraulic activated type.
Thanks!
B

[imzjustplayin]

Originally Posted by benfrogg

Imjustplayin-
How do I know if the tranny is hydraulic or cable operated? Would the cable operated HF bolt up to the D5Z1 block? This is definitely a D5Z1 block. It is also definitely the federal model.

On your website, which tranny represents the VX and which represents another like the DX? That's the transmission I assume that I have. The tires are 165/70 R13. (stock size)

What is throwing me off and telling me it's not a VX is what PDXCHRIS gave for numbers of his car that was getting better MPG, the red one. Assuming no one changed out his final drive (which is certainly possible), then my transmission is not the stock version. Is it possible that the vx came in a high altitude version?

So, all VX'ers and DX'ers, would you be so kind as to give me some data about rpms and mph? That would be super handy!
Thanks
B

Regardless of whether or not there was a high altitude VX (there wasn't), since your MPH corresponds with a MPH that is inline with a VX transmission and not any other transmission, I'd say you have a VX tranny. For the '92-'95 the civic CX and VX had the same transmission and there were no other variants. It's possible you have california emissions instead of federal but even then, the fuel economy improvement with the Federal over california isn't monumental.


To confirm, at approximately 60mph, your engine RPMs are around 2100RPM? Cause if you had a DX transmission, your RPMs at 60mph would be around 2600RPM. Yes I am aware that the speedometer is 2mph slow on the Civics but that wouldn't mean the large difference like 2600rpm and 2100rpm.

OP, I just re-read the OP, and I'm wondering, how did you not come to the conclusion that your O2 sensor is messed up and or the problem you have has something to do with the ECU or the O2 sensor? You said your mileage dropped when you changed the sensor yet all I hear you doing is looking to other things as the issue when that should obviously be the issue. The problem couldn't be more obvious. Check to make sure you don't have a California ECU in that car instead of the Federal and or make sure whether the car is California or Federal car. Call a Honda dealership with your VIN and ask them. Also take out the ECU and post the sequence printed on it so we can decode if you have the appropriate ECU for your car or not.

[slogfilet]

Ben - Here's what I got on my way home today:

gear @1500rpm @2000rpm
2nd 19 mph 25 mph
3rd 30 41
4th 38 51
5th 45 63

Running 175/70-13 tires instead of the stock 165/70-13.

EDIT: Note that these speedo readings are uncorrected for the different tire size. Probably within margin of error, though.

[benfrogg]

Imjustplayin-
I'll take a photo of the ECU later tonight. I have a spare ECU out of a known vx, so if for some reason I have the wrong one, I'll be able to swap it out.

I replaced the 02 again already with the NTK (NGK) model 24300 wideband sensor. This did help FE by a small margin (+ or- 5%). During the summer, I'll know more of it's effect. The MPGUINO does tell me that lean burn is occurring. On flat ground at 60mph, I can hold 75mpg indefinitely. Trouble is, Maine is not a plains state and I have hills to go up and down.

Okay, so again, my numbers for speed/rpms are this:
1500rpm 2000rpm
gear 2: 17 24
gear 3: 29 38
gear 4: 36 47
gear 5: 44 58


Compare that to Slogfilet's numbers from his VX:
gear @1500rpm @2000rpm
2nd 19 mph 25 mph
3rd 30 41
4th 38 51
5th 45 63

He is running very slightly larger tires (1% difference or so). This is the second VX owner with about the same speeds that are significantly (3-4mph) faster in the same gears than mine is. That says to me that my transmission is not a VX. The page you have has info for the VX and CX tranny, but is it accurate? I'm not saying you are wrong, I just don't understand.

Is it possible that certain VX's had different final drives than others?

Thanks for the input!
I've PM'd a couple of users to give their mph/rpm readings. Hopefully that will clear up this issue!
B

[imzjustplayin]

Originally Posted by benfrogg

Is it possible that certain VX's had different final drives than others?

Absolutely not. All VXs came with the 3.25 final drive, just like the CXs...

Originally Posted by PDXChrisVX

Sorry I'm so slow with this process...I finally went through the gears on the red car (the one with good mileage at 266k miles), and I did NOT get the same numbers as the blue car... second gear looks more or less the same, but then they skew a bit as I go up the gears.
@1500rpm @2000rpm
2nd 18 25
3rd 31 41
4th 39 52
5th 48 64

Granted the tires are different on the two cars (different makes), but they're nominally the same size 175/70-13. I went through this exercise with the studded snow tires still on the red car, and now I've mounted the vx wheels with the new 165/70-13s The difference seems significant enough to me to reckon it's not just slight difference in tires size among brands.

Anybody out there with 175/70 13s willing to go through this for me? Speedo read at 1500 and 2000 rpm in 2nd through 5th gears. Might be helpful to know how a cx or dx or other does with the same test.

Should I be back to the swapped tranny conclusion?

thanks,
Chris

Looking at those numbers, it would appear that your first "VX" actually has HF transmission internals while your second VX has the original VX/CX transmission. http://fatboyraceworks.com/gears/ind...raph&Compare=1

If you look, the transmission with the 3.25 final drive is the VX/CX/HF High altitude/HF California transmission is 59mph at 2000RPM while the transmission with the 2.95 final drive (CRX HF Fed) is at 65mph at the same 2000RPM. That's pretty sweet setup you've got there if that's actually what is going on since the HF tranny is cable driven while the CX/VX is hydraulic, which would mean you've either got an adapter on that HF transmission in the VX or they rebuilt the VX transmission to use the HF internals! This is exactly what I've always wanted to do!

[benfrogg]

Correct me if I'm wrong, but didn't Slogfilet just come up with the exact same scenario in his VX? That's two VX's with a specialized rebuilt HF transmissions? What is the likelyhood of that?
PDXchrisVX is from OR. Slogfilet is from WA.

I think we need more data from more users with VX's. Two cars with the same results seems pretty rare.

What do you think?
Thanks again for the input!
B

[benfrogg]

Oh, and the numbers from the ECU are:
3782-P07-A00
670-109615

The spare ECU I have from another VX is:
37820-P07-A00
670-107324

My VIN for the current car is:
2GHEH2378PH508176

Is that not a Federal VX ECU?


Also:
I'm going to post a data collection thread for all VX users to enter their gear/rpm/mph chart.

B

[imzjustplayin]

Originally Posted by benfrogg

Oh, and the numbers from the ECU are:
3782-P07-A00
670-109615

The spare ECU I have from another VX is:
37820-P07-A00
670-107324

My VIN for the current car is:
2GHEH2378PH508176

Is that not a Federal VX ECU?


Also:
I'm going to post a data collection thread for all VX users to enter their gear/rpm/mph chart.

B

Yup, that's a federal ECU.. Bad wiring somewhere? Any check engine codes? It's possible you have some bad grounds? Have you cleaned out the EGR chambers, control box, etc. etc? The again these are aged engines..

Originally Posted by benfrogg

Correct me if I'm wrong, but didn't Slogfilet just come up with the exact same scenario in his VX? That's two VX's with a specialized rebuilt HF transmissions? What is the likelyhood of that?
PDXchrisVX is from OR. Slogfilet is from WA.

I think we need more data from more users with VX's. Two cars with the same results seems pretty rare.

What do you think?
Thanks again for the input!
B

Actually seems possible considering there is a prominent transmission shop in Oregon that one could drive to from WA in order to get work done. There are a number of possible reasons why the guy running the shop would put in HF internals into a D-series transmission shell.