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Discussion Starter #1 (Edited)
Maybe this has already been reported, but I noticed this weekend that the ability to stay in lean burn seems to be a function of how long you maintain lean burn.

I drove home from Fresno tonight and noticed that after driving 30 minute straight in lean burn, the Insight seems to just stay in lean burn no matter how I stepped on the gas. I discovered this when I mashed the pedal trying to pass a truck and the car would not drop out of LB. I swear it felt like I got to around 50% throttle. It's like the car learns that if you're constantly in and out of LB, it'll adjust itself to be more sensitive to TPS changes. But if you stay constant on the pedal, it'll let you mash it once in awhile without dropping out.

Anyone else notice this?

By the way, because of the LB behavior, I had my personal best of 80.3MPG across 236 miles averaging 60MPH in 40F weather and over the nasty 4000ft Tejon pass. Snapped this when I got home.

This car is amazing!

 

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Hey Randomfire,

Breaking into the 80s is great, my best so far is 76. You were mentioning TPS, normally I know that as Tire Pressure Sensor, is that was you mean? the first generation cars do not have a tire pressure warning system. Also I'm curious when you cruse in lean burn are you getting your NoX burns every couple of minutes?
 

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Hey Randomfire,

Breaking into the 80s is great, my best so far is 76. You were mentioning TPS, normally I know that as Tire Pressure Sensor, is that was you mean? the first generation cars do not have a tire pressure warning system. Also I'm curious when you cruse in lean burn are you getting your NoX burns every couple of minutes?
I believe he may have been referring to Throttle Position Sensor. I monitor that function on my ScanguageII along with the lean-burn X-Gauge I programmed and the load gauge probably the most on highway trips.
 

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If the Insight had the "TPS mod" built in, then it wouldn't be a modification and there would be no need to perform the "mod". ;)

The behavior you describe sounds a little odd, but it's difficult to tell unless you have an OBDII reader. Over 30% TPS, and it will drop out of leanburn every time.
 

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Discussion Starter #6
What they said... The TPS mod specifically is a RC circuit that dampens sudden changes to your throttle position. Here's the original source explaining the theory behind it: TPS MOD

At 60MPH, I do get NoX purges every few minutes, but they only last for ~5-10 seconds. Much shorter than what a lot of people are reporting. I back off the throttle during the purge to keep it at 105MPG and step on it again after the purge. Again, I was able to move the pedal pretty freely up and down even during the purge cycle without worrying about it dropping out of lean burn. It was weird.

Hey Randomfire,

Breaking into the 80s is great, my best so far is 76. You were mentioning TPS, normally I know that as Tire Pressure Sensor, is that was you mean? the first generation cars do not have a tire pressure warning system. Also I'm curious when you cruse in lean burn are you getting your NoX burns every couple of minutes?
 

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If you can monitor the first o2 sensor, it will give you a better "feel" of lean burn.
I can't see the G1 running (down the road) 30min. in lean burn, as designated by the manufacturer.

Willie
 

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On my 543 mile highway trip last week, I did see a few cases where I had lean burn at a TPS over 30. One of the times it was at 34 or 35 for several seconds (15-20?). I was so surprised to see this that I failed to note what the LOD was. One thing I noticed about those rare instances was that when it did drop out of LB, it always went immediately into assist and it always seemed harder to get back into LB than the simple let off the pedal method during a NoX purge.
 

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The car doesn't lean burn during a purge cycle. It wouldn't be able to purge then.

The Scangauge and OBDIIC&C Gauge are big Insights into lean burn. Don't assume that just because you're over 100MPG you're in lean burn. It's easy not to be.
 

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Discussion Starter #10
If the Insight had the "TPS mod" built in, then it wouldn't be a modification and there would be no need to perform the "mod". ;)
Yes you're right. I was going to do the tps mod, but with what I saw last night, I feel like I don't need to now. The car already has one! :D

The behavior you describe sounds a little odd, but it's difficult to tell unless you have an OBDII reader. Over 30% TPS, and it will drop out of leanburn every time.
I agree it sounds a bit weird so was hoping someone can confirm what I saw. I do know the pedal felt much heavier because I was pressing on the accelerator a lot harder than I normally do. Maybe there was just a heavier load on the ICE and so it felt like the TPS was further down than it really is??? :dunno: I plan to hook up a ScanGuage before my next long drive and record it on video.

Besides the 30% TPS, the most surprising part to me is that I didn't have to baby the pedal to keep it in lean burn.

David
 

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I have felt what you describe with a nice tail wind. Lean burn seems almost limitless, and it at least feels like you can press the pedal down further.
 

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Discussion Starter #12
... I can't see the G1 running (down the road) 30min. in lean burn, as designated by the manufacturer.

Willie
I should clarify, the Insight did still go through its normal purge cycles during those 30 minutes. I guess I meant to say that there wasn't a driver induced event that caused the car to drop out of LB in those 30 minutes.

I recognize the behavior when a driver caused it to go out of LB. One will have to back off the accelerator significantly and wait until LB kicks in again while often losing speed in the process. I don't think that happened last night.

David
 

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David:
I'm not being sarcastic, just trying to get the old brain working. How did you determine the "purge" cycles? Watching the second 02 sensor or pedal feel. (TPS)
(Questions is the start of knowledge)
HTH
Willie
 

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Discussion Starter #14 (Edited)
Willie, no worries. There are no bad questions. :)

I determined the "purge" cycle by feel mostly. I didn't have any monitoring tool in the car. During those long stretches, I barely moved the pedal (I have a cramped leg to prove it. :D) The FCD was showing 105MPG during that time. Every few minutes, I would feel a surge of power on the car and the FCD would drop down to 75MPG. I'd back off the pedal slightly until the FCD showed 105MPG again. ~10 seconds later, the car would do the slight "jerk" that we're all familiar with followed by what feels like a loss of power and the FCD would go back up past 150MPG. I'd step on the accelerator again until the FCD showed 105MPG.

I thought maybe I had dropped out of LB a few times during the purge (edit: to clarify further, I meant I couldn't determine if dropping out of LB was due to a NoX purge or driver induced) so instead of letting off the pedal, I kept it at the same position with the FCD at 75 to see what would happen. And after a few seconds, the car would jerk and go back to 105MPG. Not an exact science, but that's how I was gauging it. :)

David
 

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Thank you. That's correct. Take Ballerina lesson and you will soon be an expert without leg cramps........HEE HEE
Good luck
Willie
 

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Keep hearing about "Lean Burn". Not sure how to tell if this is happening. Is there a light that goes on or is this just a term used when getting high MPG. Only had this car a month and don't have it quite figured out yet. Thanks
 

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Keep hearing about "Lean Burn". Not sure how to tell if this is happening. Is there a light that goes on or is this just a term used when getting high MPG. Only had this car a month and don't have it quite figured out yet. Thanks
No.. there is no light.. Unless you have the OBDIIC&C Gauge. ;)

The engine in the manual transmission Insight is a Stratified Charge("Lean Burn") engine. It is capable of running Air/Fuel ratios of 24:1+.

Normal engines do everything they can to maintain a stoichiometric air fuel ratio. With gasoline, this is 14.7:1. This means 14.7 parts air to every 1 part fuel for an optimal burn.

Normally, an engine that is running lean will quickly self destruct. The trick is that lean burn is possible at low engine loads. At low engine loads, the Insight's engine will enter lean burn mode.

The engine has two distinct modes, regular and lean burn. You'll often feel a slight hiccup when the engine enters lean burn mode, followed by a subsequent loss in power and your instantaneous Fuel Consumption Display shooting upwards even though you aren't moving your foot. If you then very slowly adjust your foot to where you are maintaining speed, you can maintain lean burn mode.

High MPG on the iFCD is not 100% indicative of Lean Burn, though if you're cruising along at over 100MPG on flat ground you most likely are in lean burn.
 

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No.. there is no light.. Unless you have the OBDIIC&C Gauge. ;)

The engine in the manual transmission Insight is a Stratified Charge("Lean Burn") engine. It is capable of running Air/Fuel ratios of 24:1+.

Normal engines do everything they can to maintain a stoichiometric air fuel ratio. With gasoline, this is 14.7:1. This means 14.7 parts air to every 1 part fuel for an optimal burn.

Normally, an engine that is running lean will quickly self destruct. The trick is that lean burn is possible at low engine loads. At low engine loads, the Insight's engine will enter lean burn mode.

The engine has two distinct modes, regular and lean burn. You'll often feel a slight hiccup when the engine enters lean burn mode, followed by a subsequent loss in power and your instantaneous Fuel Consumption Display shooting upwards even though you aren't moving your foot. If you then very slowly adjust your foot to where you are maintaining speed, you can maintain lean burn mode.

High MPG on the iFCD is not 100% indicative of Lean Burn, though if you're cruising along at over 100MPG on flat ground you most likely are in lean burn.
Thanks for the info. Noticed the hiccup and instant mpg increase today. This car just keeps getting better and better!!!
 

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Lean burn to the max?!!

The engine has two distinct modes, regular and lean burn. You'll often feel a slight hiccup when the engine enters lean burn mode, followed by a subsequent loss in power and your instantaneous Fuel Consumption Display shooting upwards even though you aren't moving your foot. If you then very slowly adjust your foot to where you are maintaining speed, you can maintain lean burn mode.

High MPG on the iFCD is not 100% indicative of Lean Burn, though if you're cruising along at over 100MPG on flat ground you most likely are in lean burn.[/QUOTE]

I am hoping that there are some more hints to keep in lean burn. I'm usually driving flat land for almost 30 miles and figure I should be able to do better than 55 mpgs in 30 to 40 degree weather here in Minnesota. So TRICKS TRICKS TRICKS, anything is helpful. I have some cold weather modes and just hooked up half of the calpod switch (the part to the clutch) and think I can do better. So lean burn is possible at speeds around 55 mph? When I feel the hiccup should I just keep a constant pressure even though the mpgs are down?

Thanks for this conversation!
 

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So lean burn is possible at speeds around 55 mph? When I feel the hiccup should I just keep a constant pressure even though the mpgs are down?

Thanks for this conversation!
Yes, lean burn is definitely possible at 55 mph unless you have an exceptionally heavy headwind, wet/snowy road, hills, etc. I have seen lean burn at speeds well north of 60 mpg under good conditions. However, at the higher speeds, it takes less extra load to make lean burn drop off.

I think it was Eli that mentioned that when you feel the hiccup and the mileage drops, you can just let off the pedal enough to keep the mpg's at around 100 or so until the NoX purge is over and. When the purge is over, there will be another hiccup and the mpg's will shoot to well over 100, at which point you will have to reapply some throttle to keep your speed up. I have not been on a trip since hearing about this but from what I saw on my highway trip the weekend before Christmas, I see no reason why Eli's method won't work.
 
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