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Old 02-05-2012, 05:20 PM   #71 (permalink)
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This is a bit like the spiritual biographies once popular a century and more ago. "Purity" has a price, it's own pitfalls. Yet there is no other way once started.

However the decisions on this come out one can assume (I think it fair to say) that the whole thing -- driving, personal transportation -- is now in the realm one might wish it to have been from the beginning.

My own take is that I wish for the vehicle to last as long as is possible. That means there will be trade-offs, some for fuel consumption and some for emissions. Then there is the practicality of ones personal situation which can make a mess of all of it. But I learn more as I learn more is both the "salvation" and the conundrum.

As Old Mech said, it's a great thread.

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Old 02-06-2012, 10:26 AM   #72 (permalink)
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I wonder if a block heater would help.
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Old 02-06-2012, 10:56 AM   #73 (permalink)
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A block heater would definitely help.
Increasing cat heat retention (insulation) would help.
Grille block would help.
Warmer intake air temp would help.
All potential uses of normally wasted heat energy would mean higher cat temperatures and better function.

It would be quite an accomplishment for Sentra to be able to maintain his fuel mileage,
AND
Satisfy his desire to not be a contributor to increased pollution.

It also means that the most dedicated hypermilers may be driving in ways that cause increased emissions. If that is resolvable then you have super high mileage and significantly lower total emissions than any normal driver., both in percentage and total volume. A smaller footprint it total, and certainly deserving of a dedicated effort.

It certainly is a goal worth pursuing and an admirable sense of ecological responsibility.
A tip of the hat to a man who is dedicated to both goals.

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Old 02-06-2012, 01:07 PM   #74 (permalink)
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Quote:
Originally Posted by Old Mechanic View Post
A block heater would definitely help.
Increasing cat heat retention (insulation) would help.
Grille block would help.

Warmer intake air temp would help.
All potential uses of normally wasted heat energy would mean higher cat temperatures and better function.

It would be quite an accomplishment for Sentra to be able to maintain his fuel mileage,
AND
Satisfy his desire to not be a contributor to increased pollution.

It also means that the most dedicated hypermilers may be driving in ways that cause increased emissions. If that is resolvable then you have super high mileage and significantly lower total emissions than any normal driver., both in percentage and total volume. A smaller footprint it total, and certainly deserving of a dedicated effort.

It certainly is a goal worth pursuing and an admirable sense of ecological responsibility.
A tip of the hat to a man who is dedicated to both goals.

reagrds
Mech
I have often wondered why with all the rules that auto manufacturers must follow and all of the devices they must include for safety, pollution etc.

Why the law does not require a simple 5lb $20 device on every car that reduces pollution and increases FE, a block heater.

Honestly I can't understand why every US made combustion engine car does not have one given how effective they are, not to mention like an EV you could "preheat" your car before you drive.

Penny wise, pound foolish.
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Old 02-06-2012, 01:08 PM   #75 (permalink)
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Quote:
Originally Posted by Old Mechanic View Post
A block heater would definitely help.
Increasing cat heat retention (insulation) would help.
Grille block would help.
Warmer intake air temp would help.
All potential uses of normally wasted heat energy would mean higher cat temperatures and better function.

It certainly is a goal worth pursuing and an admirable sense of ecological responsibility.
A tip of the hat to a man who is dedicated to both goals.
All true. But I wonder how much it would help. I think keeping the cat above "light off" temperature (~500F) with engine off would help emission efforts. However, when the cat reaches this temp, it then relies on chemical conversion to get to up to its operating temp of >1000F. So under normal operating conditions, inlet temp is [let's say] 600F and outlet temp is 1100F. The heat increase is mainly the result of adding O molecules to H and C molecules (to get CO2 and H2O). The cat needs to be >500F for this to start happening, keeping it >500F with heat wrap would make the reaction occur sooner.

BUT....by shutting down the engine, the cat will always drop to ~500F and have to restart the chemical reaction reheat to 1000F over again, so I am wondering if raised emissions is unavoidable no matter how much heat we try to retain. I wonder if an HC doser (aka extra fuel injector) and metered aftertreatment combustion air injected into the manifold when the engine is off would work. Diesel engines have a doser after the turbo to get the catalyst over 1000F for DPF regeneration.
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Old 02-06-2012, 02:32 PM   #76 (permalink)
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I don't think he has the option of modifying the emissions system in order to pass the required test, so everything he does needs to be quickly reversible (posted earlier by Sentra).
While injecting extra fuel may help light the cat faster, I don't think he can do that and make it easily reversible, so he risks automatic fail of emissions testing, plus the cost of the modification, with potentially no benefit.
Eliminating any engine off coasting may be the only option, but it may be possible to combine heat conservation and accomplish the same thing with EOC. I don't know if that is possible, but DFCO allows oxygen to flow through the cat without fuel, so it would seem like that would cool the cat off more quickly than shutting the engine off, with no O2 passing through the cat.
How long can you allow EOC versus engine running before you pass the threshold of temps required for proper cat performance?
How long does it take the cat to cool off beyond it's design parameters?
The best method of answering those questions might be to monitor the second O2 sensor which is there to monitor cat function. This would give him a voltage input that should show whether the cat is working properly or not.
It's funny that he had not post cat O2 sensor codes, but that may be the ECU "thinks" every restart is a cold start and expects no proper reading without a certain run time period.

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Old 02-06-2012, 03:26 PM   #77 (permalink)
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Old Mech -

Quote:
Originally Posted by Old Mechanic View Post
How about the advertised exhaust wrap for the converter, and possibly a temp probe that would read the temp of the outer converter heat shield. Then you could drive normally where you know the cat is lit and get a reliable reading for the external temp of the heat shield.

...
Assuming for the moment that this temp probe would be a good candidate :

High Range Adjustable Temperature Switch with LCD - Jaycar Electronics

Are you saying that the probe would be inserted *between* the heat shield (8) and the outside of the catalytic converter (1)? :

Magnaflow Catalytic Converters - Car Sound Catalytic Converters from BestInAuto.com


That would get you as close to the cat as possible without compromising/damaging the cat.

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Old 02-06-2012, 03:41 PM   #78 (permalink)
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Emission testing weirdness aside...

Leaving the heat in the cat sounds like an interesting solution, i.e. wrap and not dfco (forcing "cooling" air through the converter).

Main thing is not running it so hot that you destroy the substrate, i.e. extended cruise. If you want to get fancy add liquid cooling to the TWC (that could get dangerous with 1000+ degree coolant) and manage the TWC heat better that way.

i.e.
you are driving, too much heat building up in converter, move some heat to a small radiator.

Engine shuts off, leave hot liquid mass around the converter and inlet, put some liquid in a thermos for restart.

Figure out a way to let it heat up "dry" when cold, coolant added to thermal mass as TWC efficiency allows.

Chemical bootstrap or no, the bottom line is getting back up to temp quickly.
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Last edited by dcb; 02-06-2012 at 03:46 PM..
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Old 02-06-2012, 03:43 PM   #79 (permalink)
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All you need to do is cut a hole on both the inlet and outlet of the cat. Weld temp probe bosses onto these holes. The afertreatment systems in diesel engines have them because the ECM is constantly monitoring temps. Temp probes are generally straight thread with an angled metal to metal seal where they seat in the boss. The aftertreatment temp sensors that I work with are thermocouples and are fairly cheap, maybe $80 each. You would just need to interpret the signals. I can get the Cummins part number if you want.
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Old 02-06-2012, 03:58 PM   #80 (permalink)
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dcb -

Quote:
...

Leaving the heat in the cat sounds like an interesting solution, i.e. wrap and not dfco (forcing "cooling" air through the converter).

...
Good point on DFCO. I hadn't thought of that.

Here's a low-tech idea. This would not be viable for the regular joe, but how about an insulated cover where you pull a lever and the cover keeps the cat hot while you coast? The cover could be a single part that "slides over" the cat or a double door aka space shuttle doors that cover the cat.

Powered and automatic would be nice, but no-power and manual would save energy, be a good version 1.0, and allow you to test the mod. You'd still need the temperature probe.

CarloSW2

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Last edited by cfg83; 02-06-2012 at 04:04 PM..
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