Prius in Singapore

It can happen to any high mileage car that uses exhaust gas recirculation. Try google "throttle body cleaning" and you will find other makes as well.

 

I don't quite understand your question. Could you re-phrase it?

 

I think you might have mistaken Exhaust Heat Recovery from Exhaust Gas Recirculation. Although both make use of exhaust gases, they perform totally opposite function.

Most modern engines have EGR which is to reduce Oxides of Nitrogen (NOx) by lowering the engine temperature. You can read up below link:

http://www.autoshop101.com/forms/h61.pdf

When the engine is cold, Gen 3 introduces a new feature, EHR, that makes use of the exhaust gases to raise the engine temperature.

I think the key point is the amount of exhaust gases involved. EGR uses small amount to dilute the A/F mixture whereas EHR uses large amount to warm up the engine coolant.

 

OK, I understand now.

It may not get sticky again until a few years later but once you started cleaning it and it is not difficult to do, I 'll just add it to my maintenance list. Once it becomes a routine, you don't have to worry about loosing a physical list anymore.

 

That is correct.

That may be for conventional four-cycle engines. There are times when fuel enrichment is necessary to cool the exhaust gases to prevent degradation or destruction of the catalytic converters. With the Atkinson cycle, the expansion/power stroke is longer than the compression stroke so that combustion energy can more effectively used for production of engine power. This results in lower exhaust gas temperatures and minimizes the need for fuel enrichment.

If it just need to cool the combustion chamber, why not use outside air that has much lower temperature than the exhaust gases? That is why I think besides the cooling function, the exhaust gases also serve to dilute the A/F mixture. Exhaust gases have no O2 so the diluted A/F mixture will have less combustion and less heat will be produced.

I agree. The cooled EGR uses an EGR cooler to cool the exhaust gas before it is sent back to the intake passage of the engine. Sometimes, when the vehicle is running at a high speed or when the vehicle is in a cold environment, if this excessively cooled coolant is supplied to the EGR cooler, the exhaust gas is also excessively cooled, resulting in an excessive decrease in the temperature of an intake air in an intake passage. This may cause misfires in the engine, adversely affecting the drivability. So, in such conditions, the flow control valve may direct the coolant to the bypass passage to bypass the EGR cooler.

 

The main objective of cooled EGR is to lower the combustion temperature. Of course if you recirculate those unburnt stuff (HC, CO & NOx) into the combustion chamber, they will be burnt off. However, these unburnt stuff would also cause the A/F mixture to be off stoichiometry. As a result, another unburnt stuff will be formed again. So, I don't think cooled EGR is a good idea to get rid of unburnt stuff.

TWC (3-Way Catalytic Converter) is designed for this purpose. In Catalyst Reduction, NOx gives up its O2 when combine with CO to form N2 and oxidation of CO to form CO2. In Catalyst Oxidation, HC and CO continue to burn with O2 to form H2O and CO2.

 

I still don't get it. Both are being fed to the intake manifold, so how is it that EGR can reduce pumping loss which fresh air can't? Would you mind to elaborate, please?

 

Thanks Mike!

Is the cEGR coolant sharing the same coolant as engine? My understanding is that they are separated because there are times when stuck in heavy traffic, the engine coolant may not be sufficiently cooled and if this coolant is also sharing with EGR cooler, the exhuast gas cannot be sufficiently cooled.

 

At 114,300 km, an error message flashed on the MFD for a brief moment. It disappeared very quickly so I didn't get a chance to see what it was. Then I heard the ICE rev. up to charge the HV Bty. It didn't stop charging even though I was stopped at a traffic junction. After sometime, the SOC reached Full and then the Master Warning Light, M.I.L. and the Hybrid System Warning Light came on. I pulled to the side and restarted a few times. The warning lights would still stayed on. I was able to continue driving but the SOC would vary between 1/4 to Full rapidly. After sometime, the HV Battery Warning Light finally come on and ICE would rev. up and loose power. I restarted and the HV Battery Warning Light would go off but the other 3 still stayed on. Now, the car seems to go into "Limp mode"; HV Battery is not discharging so only the ICE is providing the driving force.

I went to buy a pair of electrician gloves rated 1kV and started to take apart the HV Battery. The Busbar were full of corrosions!



After removing the Busbar, I was shocked to find that there were no resealing done at all!



According to SSC-40G, they would have stick an absorbent sheet for every +ve terminals and apply sealant over the Busbar. The absorbent sheets would absorb excess sealant flowing down.



I found another photo showing the sealing posted by Mjolinor here:http://priuschat.com/forums/generation-1-prius-discussion/72029-warning-lights-4.html

I did got recalled to go back to BM on 22 Jun'04. Apparently, BM either did nothing or simply replace another HV Battery without resealing!

I measured every modules about 7.93V ~ 7.94V, so they are quite even. However, module #1, #33, #37 & #38 have voltages to the chassis. So, DTC P3009 must have been logged. I used vinegar diluted with water to clean away the KOH on every modules. This take care of the short to the chassis. Then I apply some sealant on all the terminals.



After assembling back the HV Battery, the 3 warning lights are still there and car still seems to be locked in "Limp mode". So far, the HV Battery Warning Light did not come back, so it seems P3009 has been fixed.

I 'm ordering the Scangauge II to try to reset the DTC. I 'll report back when it arrives.

 

The shipment of the SGII from US has been delayed due to the Lunar New Year. It may arrive next week.

Every now and then, the Brake System Warning Light would come on and the ICE would rev. up just like previous symptom. I had to pull to the side to restart. Same as before, the BSWL would go away temporarily. So now, instead of the HVBWL, it has changed to BSWL.

Last weekend, I decided to dismantle the HV Battery for the 2nd time. All the modules are OK and no more leak to the chassis. However, after assembling back one of the Busbar (with the voltage sensor connectors), some modules were giving voltage readings to the chassis! I checked the connectors and found one of the pins already corroded and broken.



I measured several pins with a Multimeter and found some resistance between the pins. So it seems the KOH has seeped into both the plug and socket and caused some of the pins to be shorted.



I desoldered the Battery ECU socket. Then I soaked both the plug and socket in vinegar. However, the short still exist so I decided to cut away those shorted pins and connect the sensing wires directly to the PCB.

Success! All the warning lights are gone now. The HV Battery can be charged and discharged as normal.