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Originally Posted by turbovr41991
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.
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Common mis-conception that running an engine lean of peak is dangerous or will melt things. LOP means lean of peak (EGT) or lean of power (the two are essentially the same idea) this is exactly what you're trying to do.
The key with the VX or vtec-e design was that the head was designed to increase swirl to permit efficient lean running - which means it can run leaner without misfiring. The swirl also allows you to run more EGR to reduce pumping losses. At cruising RPM and MP you can run any honda engine as lean as you want and it will make 0 difference in longevity.
Extra fuel is added for cooling at higher RPM and higher load. Even so I've tuned over 1000 honda engines, have seen some pretty shotty tunes but the engines put up with being run lean (even at higher RPM) quite well.
Quote:
Originally Posted by turbovr41991
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.
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The trick with a wideband is that you also need a wideband controller. There was one built into the P07 (obd1 VX ecu) but I'm not sure about the HX ECU since they always went into the trash. A Bosch LSU is about $50-$80. Most controllers are about $150ish. Techedge in AU used to make a DIY kit and I built several in early 2000 when widebands cost over $2000.
Given all the limitations of the technology you're using there isn't too much that can be done. The average cell phone has many times more processing power than a honda ECU. If I remember correctly (been over 10 years since I worked on that ECU) it was 32k. Modern ECUs now have over 1mb of data.
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Originally Posted by turbovr41991
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!
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The EPA standards are based on engine size and category of the vehicle. It is probably the most fair way to do it. We expect an 8 seat people hauler to require a larger engine thus pollute more. Why should something the size of a Smart car be permitted to pollute the same amount as a Hummer?
There are always politics involved but I've spoken to the EPA people enough over the years to know that most of them really are interested in saving the environment. This is most effectively done through dealing with the law of averages. More and more strict regulations are making a difference. Even in the past few years we're seeing new vehicles with EPA ratings in the 60mpg range. Unheard of even 5 years ago!
Quote:
Originally Posted by turbovr41991
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.
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It's not as aggressive as factory because it's most likely non-existant. It's not the easiest thing to get a chippable ECU to run EGR. It's also unlikely that you'll get a honda engine, even a HX/VX to run efficiently or smoothly in the 24-25:1 range.
On honda engines (most engines for that matter) the EGTs will be approx 75-100 degrees lower at 17.5 than 14.7. If you can get it to run at 19:1 you will probably see an additional 50 degrees dropped. If they were not insanely expensive I'd suggest getting a 4ch EGT off an airplane since we use them pretty routinely to lean out for cruise.
One way you can really increase fuel economy is through cylinder balance. Most OE vehicles are not terribly good at this but in your case you'll have tuning issues since per-cylinder fuel trims is reserved for modern cars and sport bikes... For fun you could try 4 individual fuel pressure regulators but it would be very very difficult to tune.
If you google them up check out GAMI as they have some good articles on the subject of cylinder balance.
-Michael