Correct D15Z1 leanburn info - Fuel Economy, Hypermiling, EcoModding News and Forum

greasemonkee · 07-05-2011, 11:12 PM

I finally got my vtec-e up and running. This was an hmotors jap engine so I had to round up the oil cooler and throttle body to make it a real, complete d15z1. No doubt this is a neat little engine.

This is a low mileage engine, but the O2 sensor has about 130k so it may be slightly out of calibration, but it is the original L1H1.

I've found so much false information about the leanburn operating parameters on this site and many others that I'm going to post my own recorded data in this thread.

Here's a little data I've observed from my previously-turbo car setup (hence all the gauges) :

- EGT's are roughly 250 degrees F cooler in leanburn mode

- Air fuel is 22-23.5 while in leanburn mode (measured with a new Innovate XD16 and LC1)

- Engine will stay in leanburn up to approx 4 in.Hg (which is nearly ambient manifold pressure) in all gears but 1st

- leanburn engages only between idle speed and 2650 rpm. When in any gear (including neutral) other than 1st, a manifold pressure of approx 4 in.Hg can be a achieved in leanburn until 2500 rpm, over that rpm manifold pressure must be ramped down as RPM increases to 2650.

- car must be moving a certain speed for leanburn to activate, it will activate in neutral if over idle speed and vehicle speed over 5 mph???

- Closed loop remains active under all conditions except for on a cold startup, it is possible to fully load the engine at stoichiometric fuel ratios up to 3000 rpm. Under 3000 rpm fueling richens in stages, not gradually, this is based on load and it appears to be based on throttle position at its richest and final stage. So fueling ratios go from 14.7 then steps to 13-13.5 then steps to 12.3-12.5/full rich at WOT. After 3000 rpm air/fuel continues to run 12.3-12.5 up to rev limit (regardless of throttle position) when coolant temp under approx 197* F. if temp is over 197* air/fuel richens to 11.5. Needless to say, stay under 3000 and don't let the radiator fan come of if you have to hammer down on it.

- oil temp seems to be very well regulated with this engine due to the oil heater/cooler. Even coming up the mountain and full throttle for 5 minutes I have yet to see oil temps over 210 degrees at 85* ambient temps.

Here are the parameters, very close to what the ecu requires for leanburn:

- NO Leanburn in 1st gear

- 2nd-5th gear:
rpm: 800-2400 manifold pressure ~4 in.Hg max. / 2400 rpm 5in.Hg tapering off to 8 in.Hg @ 2650. Over 2650 - no leanburn
(Seems best to shift at 2500 max with VX gearing)

- Coolant temp: Unsure of exact temps, but leanburn will activate in 5th gear or neutral before full operating temps, probably about 140*F. All other gears require full temps before engaging leanburn.

- After engine restart, even at normal operating temps, leanburn will not reactivate until after 10 seconds or so

VTEC parameters -

Low load engage - 3000 rpm
High load engage - 2250 rpm
High load disengage - 2000 rpm

Note: No leanburn while vtec active.

The leanburn difference? I drive a lot of miles per week with my D15Z1 and have done a bit of testing. The difference between ignoring leanburn/normal burn and trying to stay in leanburn whenever possible seems to be only about 3 mpg. What I have found to make the most difference is keeping the rpm under 2800.

Hope this clears some of the mis-info up, may be back to add or edit.

Link to maximizing lean burn thread (leanburn at idle and ambient manifold pressure)

http://ecomodder.com/forum/showthrea...nda-23288.html

cbaber · 04-12-2012, 10:59 PM

This thread is old but I have something to add. In another lean burn post it was mentioned that the cat needs to warm up to temperature in order for lean-burn to activate. I know for a fact (for the HX atleast) that you do not even need a cat in order to use lean burn. You dont even need the secondary o2 sensor. After I swapped my engine with a new one I had to replace the exhaust manifold. Long story short, I needed to wait until I got a new direct fit cat for another model to have it cut and welded in to my exhaust. I drove without a cat or secondary o2 sensor (check engine light on) and was still able to go into lean burn. Just thought someone might want to know that cat temperature or emissions past the first o2 sensor have nothing to do with lean burn.

It seems intake temperatures have a huge impact on lean burn. Or atleast for me. Its been about 60 degress or less this week and my car does not want to stay in lean burn for long. No matter how careful I am to keep throttle position low. On monday it was above 75 degrees and I stayed in lean burn the entire trip on the highway with no problems. So it would appear that colder air intake temps can keep you out of lean burn. Can anyone else confirm this?

drmiller100 · 04-13-2012, 02:02 AM

this is REALLY good info.

turbothrush · 04-13-2012, 08:00 AM

I missed this too. Really great stuff. Thanks for posting. Nice to the AFR confirmed by someone with a gauge.

turbothrush · 04-13-2012, 08:16 AM

Quote:

Originally Posted by cbaber

This thread is old but I have something to add. In another lean burn post it was mentioned that the cat needs to warm up to temperature in order for lean-burn to activate. I know for a fact (for the HX atleast) that you do not even need a cat in order to use lean burn. You dont even need the secondary o2 sensor. After I swapped my engine with a new one I had to replace the exhaust manifold. Long story short, I needed to wait until I got a new direct fit cat for another model to have it cut and welded in to my exhaust. I drove without a cat or secondary o2 sensor (check engine light on) and was still able to go into lean burn. Just thought someone might want to know that cat temperature or emissions past the first o2 sensor have nothing to do with lean burn.

It seems intake temperatures have a huge impact on lean burn. Or atleast for me. Its been about 60 degress or less this week and my car does not want to stay in lean burn for long. No matter how careful I am to keep throttle position low. On monday it was above 75 degrees and I stayed in lean burn the entire trip on the highway with no problems. So it would appear that colder air intake temps can keep you out of lean burn. Can anyone else confirm this?

I can confirm the vx does not need a working cat either. I get leanburn in cold temps but not as much. I just figured it may be do to the car moving thru denser air , colder fluids, higher alt load etc.

greasemonkee · 04-13-2012, 09:09 AM

Quote:

Originally Posted by cbaber

This thread is old but I have something to add. In another lean burn post it was mentioned that the cat needs to warm up to temperature in order for lean-burn to activate. I know for a fact (for the HX atleast) that you do not even need a cat in order to use lean burn. You dont even need the secondary o2 sensor. After I swapped my engine with a new one I had to replace the exhaust manifold. Long story short, I needed to wait until I got a new direct fit cat for another model to have it cut and welded in to my exhaust. I drove without a cat or secondary o2 sensor (check engine light on) and was still able to go into lean burn. Just thought someone might want to know that cat temperature or emissions past the first o2 sensor have nothing to do with lean burn.

It seems intake temperatures have a huge impact on lean burn. Or atleast for me. Its been about 60 degress or less this week and my car does not want to stay in lean burn for long. No matter how careful I am to keep throttle position low. On monday it was above 75 degrees and I stayed in lean burn the entire trip on the highway with no problems. So it would appear that colder air intake temps can keep you out of lean burn. Can anyone else confirm this?

With the P07-A01 ecu (probably all 92-95's) intake air temps are not a factor in switching to leanburn - at least down to ambient air temps of 20 degrees F

As long as manifold pressure does not pass that threshold of 4"hg it will stay in leanburn if the other abovementioned conditions are met.

Unfortunately, the later generations are severely emissions restricted.

Ryland · 04-13-2012, 11:23 AM

That was going to be my question, you did these tests with a stock ECU, not a JDM part, right? because it's the ECU that controls lean burn, the sensors on the engine are just telling it what the engine is doing.
For those of us who are a little fuzzy on what the different amounts of vacuum are, could you expand on the vacuum gauge readings and how that translates for those of us without a vacuum gauge.

drmiller100 · 04-13-2012, 11:27 AM

there is absolute pressure, and vacuum. if you are interested, go read about it on Wiki.

4 inches of mercury vacuum is dang close to WOT.

cbaber · 04-13-2012, 12:27 PM

Quote:

Originally Posted by Ryland

That was going to be my question, you did these tests with a stock ECU, not a JDM part, right? because it's the ECU that controls lean burn, the sensors on the engine are just telling it what the engine is doing.
For those of us who are a little fuzzy on what the different amounts of vacuum are, could you expand on the vacuum gauge readings and how that translates for those of us without a vacuum gauge.

You could use a vacuum gauge or scanguage and they both tell you engine load. 0 vacuum on a vacuum gauge would be 100% load on a scangauge. Most people say around 22 in vacuum is idle. So basically as you go from 30 to 0 that is basically engine load that you would see on a scangauge.

Quote:

With the P07-A01 ecu (probably all 92-95's) intake air temps are not a factor in switching to leanburn - at least down to ambient air temps of 20 degrees F

As long as manifold pressure does not pass that threshold of 4"hg it will stay in leanburn if the other abovementioned conditions are met.

Unfortunately, the later generations are severely emissions restricted.

Thats odd that they would add in IAT for HX. I have seen a few other people talk about IAT affecting lean burn on the HX so I know its not just me. Must be emissions, like you said. During those nights after it took me out of LB it would not let me back in. I had to do some EOC and then about a minute after turning on the engine it would go into LB for a short amount of time before kicking me out. When it kicked me out I was following all the parameters that allow lean burn on warmer days and for seemingly no reason it would just kick me out. Last night I tried various ways to "reset" the LB so that I could get back in without shutting the engine off. I found that if I went WOT for a few seconds and then went back to regular cruising LB would kick back in within a few seconds. I wonder if that is because the engine heated up a bit more, or if going WOT resets some function of LB.

greasemonkee · 04-14-2012, 01:02 AM

Leanburn engines have been a challenge to automakers from the beginning with NOx levels being difficult to control, and as each year goes on the emissions restrictions become more aggressive. Now we have NOx converting catalysts, but with a cost.

If you '96+ vtec-e guys have determined the IAT's are the culprit, bluffing the ecu into staying in that critical window may not be that difficult. Since resistance of the thermistor goes down with increasing temps, using a fixed resistance "simulator" with a SPDT switch may be an option. I doubt there are any appreciable ignition corrections that would cause a problem for the intended application, and since we ecomodders tend to live in closed loop, fuel would correct itself.

And 4 In.Hg. is nearly full throttle, where mine stays 90% of the time, and even has the throaty intake tone to go with it. A vacuum gauge is a powerful tool with LB engines.