1997 Civic CX to HX engine/VX trans swap! 63 MPG @ 62 MPH

[California98Civic]

Originally Posted by turbovr41991

Very cool! Glad to see anyother D16Y5 swap out there.

Last time I checked northwest was trying to get $400 ish for their chipped ECU, tune, and jumper harness. You also would not need to run these expensive 5 wire O2 sensors, EGR, and several other things that are alot of $$$. So while it might cost a little up front, at least you don't have to buy $200 O2 sensors anymore and make it a much more predictable drive.

Nice deal and set up. I almost want to experiment with this, but I don't want to lose my OBD2 port's functionality. I have looked at SAFC2 units, which can be even cheaper, but seems to require some splicing. I have not been willing to take the leap (yet). Anything I do will have to be reversible for the emissions inspection. And swapping from the DX to the CX transmission was a ig enough task for this month.

[MakitaDiesel]

$400 is a bit high for my budget minded build, but if it eliminates the $ O2 sensor & $ EGR AND increases MPG then it may well be worth it. I'm running an Ultragauge so that function I would have to go back to a basic vacuum gauge or some other OBD-1 friendly instant readout. I'm new to tuned ECUs & am curious how one can delete these 2 important sensors & return better driving & mileage, my guess is at the expense of emissions.

Do you leave the 5-wire O2 in the bung or swap it for a simpler 1-4 wire?

Did the power/response increase as well?

I'm also curious if running a tuned ECU for a long period of time would affect engine longevity otherwise everyone looking for mpg gains would be after it...

Thanks for the info

Mak

[California98Civic]

Have you had to make any adjustments to your odometer readings since adding the much taller VX tranny? I'm running the CX tranny (same gearing as the VX) with the DX ECU and gauge cluser and 14" wheels, and my distance readings are crazy under counts, if my measurements are correct. I calculated a 14% under count today! Can't be right. What's your experience?

[turbovr41991]

Originally Posted by California98Civic

Nice deal and set up. I almost want to experiment with this, but I don't want to lose my OBD2 port's functionality. I have looked at SAFC2 units

I would be careful with this. the OEM D16Y7 was not designed to run very lean. The HX engine (D16Y5) was designed to run lean without any problems. I am only running 17.5 air fuel ratio, so nothing too crazy. The timing was also set to be on the safe side of lean as well.

Oh, I also kept all my OEM hardware so I could revert to stock if needed for inspections or anything else.

Originally Posted by MakitaDiesel

new to tuned ECUs & am curious how one can delete these 2 important sensors & return better driving & mileage, my guess is at the expense of emissions.

Do you leave the 5-wire O2 in the bung or swap it for a simpler 1-4 wire?

Did the power/response increase as well?

I'm also curious if running a tuned ECU for a long period of time would affect engine longevity otherwise everyone looking for mpg gains would be after it...

Thanks for the info

Mak

I was told by the tuner that honda cars read better off the MAP sensor than they do the O2. He can run the car with or without an O2 sensor. If you choose the O2 sensor route, he uses a 5 wire wideband for better monitoring. I think he said the sensor was $50 or less and recomended a good brand to go with.

Emmissions are sacrificed any time you are in lean burn. That is eccentially why these cars are no longer made. I still dont get why a Hummer is street legal in California while these lean burn civics were not allowed. It just shows where their priorities are... Helping the oil companies!

Power is noticably better over 3k if you choose to use it. The shops original goal was to sell 300+ HP turbo cars that were fun to drive, but still got 60-70 mpg on the highway when you were just cruising.

I have not noticed any side effects for the long term use. I believe the state of lean burn it is in is not as agressive as the one from the factory. I head insights getting into 24-25 ratios, where this one is only at 17.5. The tuner even said there was alot more room to gain, but if I choose to go more lean he would want EGT gauge to monitor cylinder #3 (I guess it is the one that gets the hottest). I might go this route down the road as I have a couple extra EGT gauges laying around, but for now I am just enjoying the lassle free lean burn.

[turbovr41991]

Originally Posted by California98Civic

Have you had to make any adjustments to your odometer readings since adding the much taller VX tranny? I'm running the CX tranny (same gearing as the VX) with the DX ECU and gauge cluser and 14" wheels, and my distance readings are crazy under counts, if my measurements are correct. I calculated a 14% under count today! Can't be right. What's your experience?

Really? Which sending unit are you using? I am using the OEM 97 CX sending unit and mine seems to be nearly dead on. 14 inch tires with stock tires size as well. I have the HX cluster installed so I could have a tach, but that should not make any difference. Mine is within 1-2 miles of a GPS for distance traveled. I think I remember reading that the DX sedan transmissions were geared slightly worse than the hatchback, but I don't know if that would mean it would have a differen sending unit.

[California98Civic]

Originally Posted by turbovr41991

Really? Which sending unit are you using? I am using the OEM 97 CX sending unit and mine seems to be nearly dead on. 14 inch tires with stock tires size as well. I have the HX cluster installed so I could have a tach, but that should not make any difference. Mine is within 1-2 miles of a GPS for distance traveled. I think I remember reading that the DX sedan transmissions were geared slightly worse than the hatchback, but I don't know if that would mean it would have a differen sending unit.

Right now I just am using the 93 CX's VSS unit that was already in the trans, but I have been learning a lot from a thread I started over on honda-tech.com (awesome site, really). Though the 1993 CX was a 13" wheel and that should make a difference, there is no way my 14% figure is correct... around 2% is more likely. I gotta try again.

You are right, from what I have read online, that the sixth gen DX hatch had the same gearing as the CX and HX of that generation... the DX coupes and sedans were a bit shorter at 4.058 FD. But the final drive, the VSS unit, and the gearing generally should have no impact, I'm told on honda-tech in a way that is easily believed. So I'll chart another route tomorrow and continue testing to see what I get. Maybe the old VSS is just lousy... it has been a little bouncy sometimes.

[hungryhunter]

Nice, Now I really miss my old HF. Again, Nice job and write up.

[MakitaDiesel]

Nice info, might look into this, esp. running no O2 period & save 75% of HX driving headaches & cost down the line. I've got another (slightly off-thread) question pertaining to California98Civic's problem. I recently acquired what I was told is a '92 Civic CX trans with a bad input bearing for $25. Now, I'm running a '98 Civic DX Hatch, HX everything important (engine, trans, VSS, Cluster, ECU) so could I fix the CX trans & just swap the HX VSS into it, put it all back in the car & be where you were at before the tune? The main question is will a '92 CX trans + '98 HX VSS = same odo/speedometer readout with all other variables constant? I'm also curious as to whether the shop could tune my other lean burn mule, an '89 CRX HF + '95 VX (D15Z1 running bits)...

Thanks,
Mak

[California98Civic]

Originally Posted by MakitaDiesel

Nice info, might look into this, esp. running no O2 period & save 75% of HX driving headaches & cost down the line. I've got another (slightly off-thread) question pertaining to California98Civic's problem. I recently acquired what I was told is a '92 Civic CX trans with a bad input bearing for $25. Now, I'm running a '98 Civic DX Hatch, HX everything important (engine, trans, VSS, Cluster, ECU) so could I fix the CX trans & just swap the HX VSS into it, put it all back in the car & be where you were at before the tune? The main question is will a '92 CX trans + '98 HX VSS = same odo/speedometer readout with all other variables constant? I'm also curious as to whether the shop could tune my other lean burn mule, an '89 CRX HF + '95 VX (D15Z1 running bits)...

Thanks,
Mak

Neither the VSS nor the black or white speedo gears in the transmission should make any difference in terms of your odometer and speedometer. I learned about it on honda-tech.com (a great site, though with too many "haters" making static you'll have to ignore). My earlier calculation of a 14% under count was completely wrong, due to a mapping error. Two runs with accurate mapping since have revealed about a 5.5% under count, which must be due entirely to tire sizes. When I check tire sizes on tirerack.com I find there are 4-6% differences between 13" and 14" tires depending on brand (my tires are not on the site).

Below, two pics posted by 98EG8 on honda-tech.com document the "black" and "white" speedo gears to which the VSS's gear connects. He took these in his shop himself, and although the measurement in the pic is different because the caliper slipped as he tried to get a decent photo, the measurement had actually been identical: 90.6 mm for each. So all speed and odometer measuring instruments are THE SAME across the 92-00 D-Series transmission. Only your tire size will change the reading.

You can read my honda-tech.com thread on this yourself and notice especially 94EG8's comments in post #19 and #20. But the critical statement is: "All '92 - '00 D-series transmissions use one of two speedo gears. EX/Si/HX use a the black speedo gear. Everything else uses the white speedo gear. All models use the same VSS gear. The speedo gear is pressed directly onto the differential carrier. The transmission gearing is totally irrelevant since this comes after it. For all intents and purposes the speedo gear is directly connected to the axles. Transmission gearing absolutely does not have any impact on the speedometer/odometer."

My guess is that Honda resolved the problem of matching the speedo readouts between the 13" fifth gen wheels and the 14" sixth gen wheels through tire brand and tire revs per mile and then simply accepted "close enough" speed/distance readouts as "accurate" enough for mom and pop.

Black speedo gear (94EG8 photo):


White speedo gear (94EG8 photo):

[MakitaDiesel]

Thanks for the clarification California98Civic, after buzzing around H-T after your post I've concluded all '92-00 D-series VSS units are interchangeable, just pick the one that meets the OBD-status of your engine harness for ease of use. I'll crack open the trans I bought in the coming weeks & see what the damage is, replace what is necessary, & swap them out for (I'm banking on) a consistent 50 mpg given my driving style/commute. The tune will come later (before the O2 dies, hopefully).

Mak