The cat needs unburned fuel hydrocarbons in order to catalyze the NOx into more 'harmless' substances.
The current Gen-1 Insight design to accomplish this is with the occasional ICE purge cycle... and the cat stores the NOx between purge cycles.
Here is a alternative where they bypassed the ICE and pumped unburned fuel directly into the cat.
This would allow for NOx purge events without ICE purge events ... meaning you could stay in Lean Burn without the purge cycles.
I wonder where the break even point would be? ... OEM Gen-1 Insight Design has a % of the fuel energy content is used in the ICE during the Purge event cycle , but the ICE % efficiency as a whole is lower ... where the bypass method doesn't lower the whole ICE % efficiency , but gets 0% of the energy content of the bypassed unburned fuel in the ICE.
Interesting ... if the amount of bypassed fuel use is small enough it might be a net more energy efficient option ... although I have my doubts about being able to safely modify a OEM Gen-1 Insight cat to handle pumping fuel directly into it ... and it would be too expensive to sacrifice cats to try experimenting with ... still interesting idea.
IamIan, sounds like an interesting idea. I suppose you could plumb a line to the cat but you would probably have to find out a couple of things. Such as: 1) How does the car determine when it's time for a purge" 2) How does the car decide when lean burn can resume? From the amazing things the people on this board have come up with to help improve these cars, I see this idea of eliminating the purge cycle.
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Silver '00 MT
85.5 LMPG
80+ psi in RE92's for the past 2 years without incident
Calpod switch
Warm air mod
Grill block
EPS fuse removed
FAS/fuel injector interrupt circuit
grid charger
OBDII C&C gauge
It sounds good, but I have to think that if it was a better way to do it, either Honda or VW would have done it, in VW's case with their diesels. Of course, bigger diesels use urea injection, and while diesels are a little different than our cars, they are both doing the same thing: burning up the extra nox from lean burn. If I am going to use fuel to burn off the nox, I would rather it push me down the road too.
The problem at the moment is we have no control/idea of when the car enters lean burn or purges after a lean burn session.
We have no access to the ecm programming so have no idea other than by observation of the results how the software is constructed or working.
How is lean burn achieved? What I mean is what physical control input changes are made to the engine/fuel configuration for the car to go into what we call LB.
Is it
1) Simply the fuel injectors shorten there pulse duration?
2) The above combined with an EGR valve position change?
3) Some other stuff as well?
We need to gather data on the injector timing and egr valve etc for a start during some driving when car is moving in/out of lean burn.
Once we have that data it would be possible to use some very fast logic or a pic to manipulate the injectors directly. so the ECM - > Our Gizmo -> Injectors
We could just replicate what the car does in LB, we would also need to fake both the O2 sensors as well to keep the car thinking it has undergone a purge cycle at the reqd times.
The problem at the moment is we have no control/idea of when the car enters lean burn or purges after a lean burn session.
We have no access to the ecm programming so have no idea other than by observation of the results how the software is constructed or working.
How is lean burn achieved? What I mean is what physical control input changes are made to the engine/fuel configuration for the car to go into what we call LB.
Is it
1) Simply the fuel injectors shorten there pulse duration?
2) The above combined with an EGR valve position change?
3) Some other stuff as well?
We need to gather data on the injector timing and egr valve etc for a start during some driving when car is moving in/out of lean burn.
Once we have that data it would be possible to use some very fast logic or a pic to manipulate the injectors directly. so the ECM - > Our Gizmo -> Injectors
We could just replicate what the car does in LB, we would also need to fake both the O2 sensors as well to keep the car thinking it has undergone a purge cycle at the reqd times.
Very difficult to get all that working together.
From my work with race cars I strongly suspect, with no real survey data, that the Insight like most cars varies the injector pulse width. It would be fairly easy to verify by having an small oscilloscope and operator in the right seat, and swing the pickup lead out a partially opened window to reach an injector test point.
It would be an interesting but very engine unfriendly experiment to "manipulate the injectors directly." Dangerous because getting too lean under the wrong conditions is an invitation to burned pistons. Since "lean is mean" I've seen a lot of racing pistons burned in this manner. Injecting extra fuel to cause a purge is an interesting idea, and probably safe enough, but provoking an "artificial" lean burn would, IMO, be very dangerous. This line of reasoning could lead there.
We have direct access to the 1st O2 sensor data so could monitor the AFR directly in real time. We are not thinking about making it leaner than it already is, just making it run lean more of the time. I agree it would be easy to gather the data which as you say will be mainly concerened with the injector pulse width captue.
We have direct access to the 1st O2 sensor data so could monitor the AFR directly in real time. We are not thinking about making it leaner than it already is, just making it run lean more of the time. I agree it would be easy to gather the data which as you say will be mainly concerened with the injector pulse width captue.
Yes, I was afraid that this was where the discussion was going The problem with running an engine on the lean side is that the impending failure doesn't really come with any really strong warning or flag waving as to when you are getting into trouble. It is true that the key lies in the AFR, but you don't know the limit, for any given set of circumstances. If you get it wrong you get to buy a new motor, a pretty high price for a bit of knowledge.
I just returned from the dyno with my race car. My tuner, who has rebuilt plenty of blown race engines, likes to keep the full power, WOT, AFR to around 12.5 at worst. It is true that the car will make a bit more power at leaner mixtures, but the race car is run in a variety of environmental conditions, and one must tune for the worst. Of course this argument is only for amateur racers who can have their season terminated by a blown motor, but the argument for many Insight owners isn't much different.
The motivation is clear enough. Leaning it out would improve fuel economy and allow us to get bigger numbers, but I think I'll leave this experiment to the first half dozen or so enthusiasts to find the limit. It is quite different from tinkering with a few OBDII bits
We wont be effecting the load condition to initiate lean burn nor pushing a leaner AFR ratio than is already governmened by the Engine Control Module (ECM) just trying to remove the NOx purge thats slightly richer than stoichiometric 14.7:1 AFR, of course this will make our cars more polluting due to the NOx adsorbing catalyst becoming saturated but would reduce fuel costs.
I guess if we could fool the ECM to control the injectors with lean burn fuelling we still might create an issue from spark timing if the purge changes the ignition timing aswell.
Data needed on that for a series of steady state load sites in lean that shift to NOx purge
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Lean Burn without Purge Cycles
The problem with running an engine on the lean side is that the impending failure doesn't really come with any really strong warning or flag waving as to when you are getting into trouble. It is true that the key lies in the AFR, but you don't know the limit, for any given set of circumstances. If you get it wrong you get to buy a new motor, a pretty high price for a bit of knowledge.
