Holiday reading for Diesel-heads

I think the EGR valve is purely a pollution controll measure, and has no positive effect on power or economy. I recall reading an article on the Patrol 4.2 TD, where it explained that it was the only bit of electronic gear on the 'old tech' motor, which was easily (and illegally) disabled, suposidly to give a little more power and better economy. Perhaps someone with better mechanical knowlege will be able to ellaborate on this.

Cheers Andrew

Hi Guys,

Here's a bit of a blurb I wrote about EGR in a post a few months back:

"The dreaded EGR (Exhaust Gas Recirculation) - never been able to work out the logic of it meself...

The theory goes: very high combustion temperatures cause nitrogen and oxygen in the combustion air to combine to form oxides of nitrogen (I think the bad ones are NO & NO2,). Whichever ones, these are the major culprits in forming photo-chemical smog in large cities, so the powers that be have declared that vehicles must put out less than a certain % of oxides of nitrogen to meet emission standards. And the method they use: dilute the combustion air charge to the engine by mixing some of the exhaust gases back into the inlet system under certain conditions.

The result: combustion temperatures are reduced because the effective percentage of oxygen in the combustion 'air' is now less than the
'natural' level of about 21% - and a lower PERCENTAGE of oxides of nitrogen is present in the exhaust gas. BUT, I've never been able to reconcile the fact that EGR, by it's very nature, reduces the operating efficiency of the engine and therefore, the engine must use more fuel (and overall, produce more exhaust products!) to accomplish the same job!

It's always seemed to me to be a bit self-defeating. I mean, the manufacturers use turbo-charging, high-pressure, extremely finely atomised injection systems and precise electronic controls on injection timing and duration to get the maximum possible efficiency out of modern diesels - than slap on EGR to undermine their best efforts??

Getting a bit off-thread here - back to you question about the TD42Ti Nissan engine. From the horses mouth (Nissan technical bulletin):

"EGR (Exhaust Gas Recirculation) has been adopted to the TD42Ti. EGR is added to improve emission performance, ie; lower the NOx emissions.
The EGR lowers engine combustion temperatures which has the added benefit of reducing the NOx emissions.
In the case of the TD42Ti part of the EGR piping is a water cooled unit."

and

"To assist in maintaining lower combustion temperatures, the exhaust gas that is recirculated back into the engine via the EGR system is further lowered in temperature by an EGR cooler." [and more unnecessary load on the cooling system??]

Now, far be it from me to suggest anyone remove such an important anti-emissions device, but that EGR cooler looks like it could be easily converted into a nice camping shower hot water heater...

One last point: should anyone remove the EGR system (for, say, off-road competition??), be aware that your full load combustion temperatures will rise, as will the maximum exhaust gas temperature [EGT] - simply because you are now burning your fuel in 'real' air."

Hope this helps. Perhaps I should elaborate on this as another "Turbo Talk" topic?
Ian

Gday Ian

Does the EGR actually decrease the EGT as you state, I understand it should, but in the reduction of the O2 in the combustion chamber therefore increase the fuel/O2 ratio increasing the EGT?

Andrew

Well there you go, I was going to ask you your opinion on EGR valves but someone beat me to it!! In the surf it's a vacume operated mechanical type valvue (as far as I understand) that closes under low vacume pressure (idle) and opens under full load. a "friend" of mine has blocked his vacume hose with a screw and has found his vehicle performs much better both power and economy wise and blows a lot less black smoke under load.
Interesting about the EGT temps being higher, something I will have to watch out, I mean tell him to watch out for. ;-)

G'day again mate. I have been poring over this a bit since Bruce sent me the addy last night on intercoolers. I reckon its worth reading through as it has definitely confused me. You will need to look down the page to "Intercoolers Must Read!! You want to know more?"

I had been attracted to looking at the grey imports to replace the tiddly one in the GU but I would have to be very careful. Some reduce the air pressures of the turbo by 2-3 psi on the back side of the intercooler. Hardly an enhancement :-(

An observation of three friends all driving turboed GUs to Cape York this last year. Fuel economy didn't vary between the intercooled one and the other two non intercooled ones. Nor did it appear power did either. They are all unmodified in the engine but maintained by one guy who is the mechanic in our local community. Funny how we have been sold on these intercoolers on the 4.2. It may be slightly denser air they ingest. I would look forward to some info to reinforce or argue the case

WHAT! You Haven't Got one?

Look out Annette, he is going to raid the kids piggie bank to get one, and maybe his super fund and his poor old mums purse.

I am absolutely p i s s e d and amazed that you don't have one these Roachie.

What happened, SA in the 4WD dark ages and they burn any literature on such a nasty god fearing piece of apparatus.

Annette censor all you Mags in fear of you placing the family in the Bankruptcy courts.

You are just lucky they don't have/run debtors courts like they used to in good old mother England.

I'll take a breath now and look forforward to seeing a brand new sparkling, air rammed via bonnet scoop intercooler in your rig next time I visit.

Ooooooooooooo! you are such good value.

By the way I was out driving arounf in the Troopy today, all 3.2T of her in 39C heat.

Air-Con blowing chilled air on me and cruising up and down a hill or two five times steeper than any Humock you can find.

Guess what. Temp guage never moved from usual spot and Ian's EGT gauge only got to 430C with the speeds varying from 60 - 100kph.

Power steering pump all ok! however thats a camp fire story that one, after I've had a few and feel like sharing.

Gday Rob

I cleaned mine on the 2.8 the other day. Nissan Dealer advised to clean it with Brake Cleaner(aerosol) and compressed air. Be carefull though, I dont think you'll get much change out of $1000.00 for a replacement. Brake cleaner is similar to carbie cleaner, but is supposidly less abrasive. Good Luck! Oh, and don't do what I did and unscrew the panel on the side to see where the wires go - that will break soldered jounts and require you to do some surgery to get at the circuit board within the unit to solder them back on, provided the 3.0l unit is similar to the 2.8.

I did this after a post I did with good responses concerning poor fuel economy. from the guage only, I seem to have about a 10% improvement there, but I'll fill up on Wednesday when I get home from work and post the first result.

Andrew

You can also get electrical contact cleaner in a can from the auto store. Probably would advise against using a cloth, but you dont need compressed air , you can let it air dry .

Again not sure of the construction of the sensor , some have the wire inside a glass bulb and are more robust.

Hope this helps

Glenn.

Your other post went on for days Motherhen. I think has some interesting points - enough to ring to talk with one of the forum members this morning. LOL

I particularly laugh at the last comment you made here though. I actually gave a mark of 11/20 for the careers teacher at the local school to have my dearly beloved put the business stamp on it and sent it to the principal :-(

and? So you are going to spend money on two devices x several that won't do anything for you except lighten your pocket are you Mr Lucy?

You would be better to mull some wine then mull over it until the thought went away. Could mull over some wine if you came this way....

Have a prosperous New Year sir

well, umm, actually......

With my previous vehicle (GQ TD42), after I had the (AXT) turbo fitted, because it was doing the job just so-o-o much easier, IF one drove within the posted speed limits, it was good for close to 100kms more per 95L tank than before the turbo was fitted.... True!!!...
which demonstrates that a turbo *can be* a fuel-saving device, but that's not why we fit 'em, is it????

Of course, the picture changes once ya start to USE the extra power, and "let it have it's head" a bit;-)))

Firstly - Moses

You leave my dabbling in 'high technology' alone and git back to those cows. I am sure they would love to 'mull a wine' or two with you. (LOLO)

Just leave this high tech stuff to us city slickers.

Now! if it was for the heat wave, I most probably would have been calling in tomorrow. However, it will be home in the Air-con until it 'blows over'.

Second - ED. C.

Precisely my point.

You utilze a turbo for power to do what ever it is you have to or need to do.

Why would you buy/put a turbo on ( $3500 - $6000) to see if you can drive it a few cents cheaper.

If thats what you want/crave, then buy and drive a Hyundi Excel or a Vesper motor scooter.

Even better - walk as its the cheapest of the lot.

You better come down here and walk to the shops a couple of times a day Lucy. You would be thinner than ever and never get anything else done. LOL

Been thinking of a motorcycle here too but a Vespa? My dad had a Hyundi but my feet tended to cover two pedals and they were too easy to hit the wrong one as my mother proved, God rest her soul. I need another garage to make that practical. I do have a car that is economical if I am to travel anyway. I think friend ED C has some other objectives too with the turbo apart from, but as well as the better economy. No need to hand chit on him over that. LOL

I am glad Moses has a turbo as he would be sluggish at his weight unless he had a 6 litre motor or something. Turbos actually make smaller motors more powerful so the weight advantage is there without the heavier chassis.

Am to be here by the aircon too Lucy. Have a good one, Dierdre too, won't you.