1998 Civic LX to HX D16y5 conversion has begun!

[firehawk618]

Originally Posted by Chrysler kid

It really depends on driving style. If this is a long commuter all highway miles very few stops he would see more benefit from the taller gearing and steelies with disc covers

If this is a mixed city and highway driving there really is not much point. City driving you would want shorter gears and the light weight wheels from a hx or vx to require less effort to accelerate.

With my d15b s40 lsd trans on my hx this winter I'm getting 36.8 mpg all city driving. Lean burn kicks in at 52mph and with 45mph speed limits I can usually hit a clean lean burn atleast once on my trips for a few minutes

There is also a thread back in the depths of this forum where a hx member did install a vx trans into his car, I believe he was hoping to turn 2k rpms at 60mph similar to a vx model but noticed he was still turning close to 2200 rpms. He concluded that the trans swap which he intended as an upgrade was more work than it was worth and didn't really net him any benefit.

Lean burn is rpm and speed sensitive on the hx ecu. It only engages in final gear during certain conditions above 2300 rpm or 55mph-78mph. There was also a member who did install a few resistors into his vss sensor to trick the ecu but again I don't recall him updating his posts or fuel log after that

Now if his factory lx trans is on the way out then I would say yes to swap them but he hasn't mentioned that

You make some good points.

My DX trans is fine, ISB is nice and tight and the trans is very quiet.

I did not know that the lean burn factored in speeds. I have read the opposite but it really seems to be quite the mixed bag of theories.

I will have MPGUINO + Ultra gauge. I will keep a close eye on things and come up with my own theory on what parameters the ecu likes to get into lean burn.

I do not drive a lot of highway on my daily commute, a short stretch here and there so a really tall FD would probably be more frustration than it's worth at this point.

Who knows, I may do this whole swap and see zero improvement.

We shall see.

[firehawk618]

On a side note, I ended up working late tonight then to top it off I realized that I had locked my keys inside my Heep.....sooooo ended up bumming a ride home from work.

Any gumption I had to start tearing the motor out of my Civic went bye bye.

Looks like my new target finish date will be this weekend.

On a positive note, my Ultragauge arrived today!

Just waiting on the MPGuino to arrive. It sure takes a long time to come from.....whatever country he shipped it from.

[Baltothewolf]

Chrysler kid, that was me that put the VX Transmission into my HX. Yes, it did completely screw lean burn in fifth gear. Hence why I told OP to down his tire size if he went with a VX Transmission.

OP, lean burn in the D16Y5 will only engage above 2600rpm, no exceptions. This is why I told you VX tans +RE92'S are your best bet at success with your quest for MPG. The VX trans will lower your RPM, but the Re92's will offset the lower gearing, improve your city acceleration and give you lower rolling resistance. If you go Taller gearing, go 3.73, nothing lower unless your going to go Re92's. I almost wanna say 3.73's with RE92'S would be the best combination, but testing or some math would be required to know what speed 70mph would be.

[firehawk618]

So you're saying that lean burn is dependent on throttle position, map sensor, coolant temperature, rpm's and probably some built in timers but not speed?

And yeah, I'm quite ok with the gearing I had in the DX transmission. The only reason I'm running the EX transmission right now is because I have a y8 head on it + Neptune ecu.

The shorter geared EX definitely is a good match to the y8 head.

[firehawk618]

It kind of baffles me, I always thought the lower RPM's is better for efficiency......but they engineered this engine to only kick into lean burn >2.6k rpms.

Do you happen to know the specs of the HX injectors?

Are the HX/DX/LX all the same flow rates?

Edit: I may have found the answer here, assuming this information is correct.

http://www.injectorwarehouse.com/inj...linjectors.htm


The reason I was asking is I have a couple sets of LX injectors and was going to send a set out for cleaning if they were the same as HX.

[Chrysler kid]

Originally Posted by Baltothewolf

Chrysler kid, that was me that put the VX Transmission into my HX. Yes, it did completely screw lean burn in fifth gear. Hence why I told OP to down his tire size if he went with a VX Transmission.

OP, lean burn in the D16Y5 will only engage above 2600rpm, no exceptions. This is why I told you VX tans +RE92'S are your best bet at success with your quest for MPG. The VX trans will lower your RPM, but the Re92's will offset the lower gearing, improve your city acceleration and give you lower rolling resistance. If you go Taller gearing, go 3.73, nothing lower unless your going to go Re92's. I almost wanna say 3.73's with RE92'S would be the best combination, but testing or some math would be required to know what speed 70mph would be.

2300 rpms' for this little 96 lean burner, it will enter lean burn at 55mph with a steady foot and then be very easy to get back into at 52mph. I've been thinking my cheap little short ram intake actually helps get into lean burn easier because the exposed filter element does not restrict air flow like a stock air box with the air silencer. Only have a vacuum gauge and my speedo reads about 3% over actual, I'll hook up my scanner this week to get exact numbers but it's pretty easy to tell when I'm in or out of lb with the vacuum gauge. My modifications are the s40 LSD trans, iridium plugs, and no name short ram intake. No fuel additives or grille blocks

I've never seen lean burn in 4th gear I believe that is a pure myth

What I really want to know is if the hx cvt ecu has speed restrictions programmed into it, if not the federal cvt trans ecu would let you lean burn in every gear

My 1998 hx would need to be at 65 mph and I was getting 38 mpg with 50/50 highway city. Yuck, that was with cheapo Walmart tires

[firehawk618]

I didn't think any CVT HX's had lean burn. I do believe none of them came with the 5 wire primary o2 sensor.


Long night in. Started at 5pm. Old engine out, new engine in.

All that's left is re-install axles, add fluids.


2 things I have noticed that are NOT plug and play.

The vacuum line for my CC had it's own port on my y8 intake. On this intake that port is not drilled. Not a big deal as I'll tee off of the fuel pressure regulator vacuum line.

The second is my car has the evap canister under the hood with a solenoid / sensor on it. The HX engine harness does not have this plug.

I will figure out what i need to do IF I end up with a CEL for missing evap control / tank pressure sensor.

[Chrysler kid]

Originally Posted by firehawk618

I didn't think any CVT HX's had lean burn. I do believe none of them came with the 5 wire primary o2 sensor.


Long night in. Started at 5pm. Old engine out, new engine in.

All that's left is re-install axles, add fluids.


2 things I have noticed that are NOT plug and play.

The vacuum line for my CC had it's own port on my y8 intake. On this intake that port is not drilled. Not a big deal as I'll tee off of the fuel pressure regulator vacuum line.

The second is my car has the evap canister under the hood with a solenoid / sensor on it. The HX engine harness does not have this plug.

I will figure out what i need to do IF I end up with a CEL for missing evap control / tank pressure sensor.

I can look in a few minutes to verify where my evap solenoid is located.

[firehawk618]

Originally Posted by Chrysler kid

I can look in a few minutes to verify where my evap solenoid is located.

That would be great. If it is in fact on top of the canister then I am simply missing the connector that's hiding behind the intake.

It was a late night and could easily be over looking it.

[Chrysler kid]

The purge valve is bolted onto the back of the fuel rail. My car and all hx were obd2a, and I think 98-00 (non hx) were all obd2b. The evap location may have been a 98 change up