vx vtec-e experts?

[97-civic-ex]

Originally Posted by 83gs1100g

hey guys thanks for the help!

dont quite on me now! please respond!

maybe i was thinking this wrong after all maybe not? please bear with me on this.

is vx and hx operate the exact same? from idle to what ever rpm its in 12v mode?(i understand when it hits crossover rpm and goes to 16v mode)

so what happens to a vx if its already in 12v mode and it goes into lean burn? i thought that was what it did when going into lean burn?

so does the hx go into lean burn like the vx?

Yes, they are activated in the same manner. They both start 12V and the vtec solenoid kicks in 16V. It is a mechanical activation by the solenoid that opens an oil passage way and the pressure activates the pins in the valvetrain to lock in the 16V.

Lean burn is software controlled that will change the air fuel ratio from stoic, i.e. 14.7:1 ,... to honda's lean burn which I've read is above 22:1. This lean burn mode will only kick in when certain requirements are met,.. i.e. car is up to temp, no CEL, in 12V mode, engine load is below a certain amount,.. and others.

Yes the HX also has lean burn, but from what I read the Cali version ECU will not go into lean burn as much as Fed version due to the cali smog requirements.

[California98Civic]

Originally Posted by 97-civic-ex

... the HX also has lean burn, but from what I read the Cali version ECU will not go into lean burn as much as Fed version due to the cali smog requirements.

"As much as" is interesting to me. Do you mean that the Cali HX engines/ECU were set up for a "lean burn light"? Is that what you read? I know from I think MetroMPG that the gen 1 Insight had lean brn even in Cali (got a ULEV rating in fact). So maybe the HX improved on the VX lean burn somehow, sorta on the way to where they got the Gen1 Insight?

[97-civic-ex]

Originally Posted by California98Civic

"As much as" is interesting to me. Do you mean that the Cali HX engines/ECU were set up for a "lean burn light"? Is that what you read? I know from I think MetroMPG that the gen 1 Insight had lean brn even in Cali (got a ULEV rating in fact). So maybe the HX improved on the VX lean burn somehow, sorta on the way to where they got the Gen1 Insight?

From what I have read/remember:

The VX cali vs fed was narrowband/wideband O2 sensors and ECU differences.

The HX got the roller cam over the VX model and
Cali ECU has more restrictions in going into lean burn
Fed ECU goes into lean burn easier.
Both are same lean burn, just easier to get into and stay in on fed.

My brother has a cali HX and when he swapped to fed ecu he said he "thinks" it gets into lean burn easier, but it could all be just a butt dyno effect. So for now I am just saying its all based off memory of what I have read.

Again from memory,... the lean burn mode changed from altering AFRs from pre 2001 to just altering throttle control to post 2001.

Meaning true lean burn was no longer available for 2001 + model HX civics,... but I have read some conflicting reports that it is still offered even now. I haven't confirmed any of this myself, but I have done a lot of research on lean burn, vx, hx, 3-stage for pre 2001 models and am pretty confident what I wrote is true.

PS, I have decided to run my y8 with a 3-stage head on a p2j-003 ecu(already found and purchased) which took advantage of all the above mpg/lean burn/vtec,.. except roller cams.

[California98Civic]

I think the Cali HX primary O2 sensor is not the wide band, 5 wire type. Without the wide band sensor, I don't think the ECU could do much... I think.

[vrmouseyd15b]

I would imagine they do the same thing. look up the motors vs transmissions on the two cars "bone stock" they probably run the same motor, and different tranny gears or something dude.

[California98Civic]

Back to the 1992-1995 vtec-e, I am reading the USDM factory service manual covering that engine. The relevant part is the early pages of section five. I noticed something interesting. The description of the control system, the parameters are load, rpm (2500+), coolant temp (min 22.5* F), and speed. The minimum speed is just 3mph! Three. Seems almost as if you could get to lean burn at light load in first gear in this very tall tranny. Certainly second gear.

[83gs1100g]

Originally Posted by California98Civic

Back to the 1992-1995 vtec-e, I am reading the USDM factory service manual covering that engine. The relevant part is the early pages of section five. I noticed something interesting. The description of the control system, the parameters are load, rpm (2500+), coolant temp (min 22.5* F), and speed. The minimum speed is just 3mph! Three. Seems almost as if you could get to lean burn at light load in first gear in this very tall tranny. Certainly second gear.

ya i noticed that to when i downloaded the manual. i go into lean burn in 2nd easily when just crusing thru town or in traffic.

[97-civic-ex]

Originally Posted by California98Civic

I think the Cali HX primary O2 sensor is not the wide band, 5 wire type. Without the wide band sensor, I don't think the ECU could do much... I think.

On the VX that is true.

On the HX O2 sensors are the same for both cali and fed. Only ecu is different. Again, i did the research for my brother's 2000 HX that is currently running a fed ecu and nothing else is changed. And if you do a search you will find a member on this forum has done the same thing and passed ca smog with fed ecu.
If o2 sensors were different you would not be able to swap ecu's without swapping O2 sensors as well.

Edit:
Oh and a lean burn motor doesn't 'need' a wideband. The 3-stage p2j ecu runs the d15b with a single wire narrowband o2 sensor just fine with lean burn. It all operates in open loop anyway, which means the o2 sensor is out of the equation and it controls fuel based off a predetermined map/setting.

[California98Civic]

Originally Posted by 97-civic-ex

On the HX O2 sensors are the same for both cali and fed. Only ecu is different. ... If o2 sensors were different you would not be able to swap ecu's without swapping O2 sensors as well.

Yup. You're right. I was just searching. And both the Cali and the Fed MT HXs had the 5-wire wideband. But it seems the CVT HX had the 4 wire narrow band O2. So not all the HX models had that 5 wire! It's just that Cali/Fed was no longer the important distinction. MT/CVT was.

Originally Posted by 97-civic-ex

Edit:
Oh and a lean burn motor doesn't 'need' a wideband. The 3-stage p2j ecu runs the d15b with a single wire narrowband o2 sensor just fine with lean burn. It all operates in open loop anyway, which means the o2 sensor is out of the equation and it controls fuel based off a predetermined map/setting.

Seems this is true too. So interesting! Here is a guy with lots of gauges who swears lean burn is closed loop operation in all conditions except cold: http://ecomodder.com/forum/showthrea...tml#post248581

But if you look further down on that first page you'll see Ryland state essentially what you have said, that it's open loop in the US market. Lots of variation. I guess the ECU uses stuff like the O2 and the knock sensor to keep abreast of what's happening with the engine while in lean burn so it can adjust other parameters to protect against engine damage?

[darcane]

Originally Posted by 97-civic-ex

Again from memory,... the lean burn mode changed from altering AFRs from pre 2001 to just altering throttle control to post 2001.

Meaning true lean burn was no longer available for 2001 + model HX civics,... but I have read some conflicting reports that it is still offered even now. I haven't confirmed any of this myself, but I have done a lot of research on lean burn, vx, hx, 3-stage for pre 2001 models and am pretty confident what I wrote is true.

For what it's worth:
I have an '01 HX. From what I've read, you can tell when it enters lean burn mode by watching the secondary O2 sensor output (should drop to zero) and you will feel a... stumble. I see both of these on my HX, and it is a California model. It has a wideband O2 sensor.