Exhaust temps - 2LT

[Mr X]

Hey boys & girls,

Just had the pyro installed. What sort of exhaust temps should I be seeing, & what's the upper limit? It's a 2.4TD Bundy with intercooler running 8-9 psi (yeah, I know - would've been good to have the pyro before the i/c...). It's installed in the manifold before the turbo.

I've got a couple of full throttle 80km/h hills on the way to work & she doesn't get much over 500 deg. so far...

Thanks
X.

[phippsy]

Please correct me if I'm wrong, but I thought the pyro went after the turbo, only just after, but I thought the exhaust would get hotter through the turbo??

[eliteforce32]

phippsy ud be correct mate.....pyro needs to be about half a foot form the back of the turbo...... exhuast pipe

[MarkR]

There seems to be a couple of schools of thought about whether a thermocouple should be located before or after the turbo. A somewhat unlikely scenario with modern thermocouples, is that a piece of the thermocouple could break off and hit the turbo impeller. If this were to happen the jolt to the turbo shaft could also severely damage the compressor fan, sending pieces of metal into the engine intake.

The plus to mounting the thermocouple before the turbo is that the pyrometer will show much higher EGTs prior to the turbo than after, thus giving a closer indication of the air temps within the engine. The heat difference from before to after the turbo can be as much as 350-400F. The greater that heat difference, the greater the amount of energy being used to drive the turbo impeller.

[eliteforce32]

hang on my friend talk degrees celcius (sp) but yeah and no, having the pyro probe after the turbo in the exhuast side i believe give a better indication of wether their is something wronge, when the guage starts to rise, and also again say uve been playing with injector pump and fuel screw and having more unburnt fuel lying around will alsogive a better indication of this, but as u said HORSES FOR COURSES!

[MY45]

hang on my friend talk degrees celcius (sp) but yeah and no, having the pyro probe after the turbo in the exhuast side i believe give a better indication of wether their is something wronge, when the guage starts to rise, and also again say uve been playing with injector pump and fuel screw and having more unburnt fuel lying around will alsogive a better indication of this, but as u said HORSES FOR COURSES!

Elite, the diffeance in temp wether it be in degC or F are the same as the scale they run on is the same... just a different # for 0 degC

[MarkR]

Sorry guys, forgot that you used metric (500 deg F sounded awfully cool). We Canadians have supposedly gone metric, but since the U.S is still S.A.E., and they are our main trading partner, we also use that system alot. The chances of finding a metric pyrometer around here are pretty slim . One more thing, I was wrong about the temp difference before/after the turbo ranging from 350F-400F. It is a little less, more like 200F-300F (93 C - 148 C)

As for converting Celcius to Farenheit, There are 1.8 degrees Farenheit to every 1 degree celcius. There is also scale shift of 32 degrees since water freezes at 32 degrees Farenheit.

For example the 500 C that Mr X quoted would work out to;

(500 x 1.8) + 32 = 932 F.

This sounds like a very reasonable temp. From the reading I've done it is generally recommended to keep the manifold (pre-turbo) EGTs under 1100 F (593 C) for the sake of engine longevity.

If for example, Mr X's thermocoupler were located after the turbo, and he was getting readings of 500C, then the manifold EGTs would probably be somewhere around 593 C - 648 C (too high).

What I'm trying to express (in my long winded way) is that is essential to take into account which side of the the turbo that the thermocouple is located when interpreting EGT readings. There is more guess work involved if it is located after the turbo. Some individuals use pyros before and after the turbo ($$$) so they can determine how much energy is imparted to the turbo.

By the way awesome site. 2L-T s are pretty rare in Canada and almost extinct in the U.S., so this is an excellent resource for me.

edit: I just noticed it says at the top 'posted Mon Nov. 15" Hey its only Sunday morning here . Not only are we North Americans way behind you guys in diesel technology, were just plain behind you period. I'll have to check Aussie sites to get tomorrow's news

[MY45]

there you go....i was wrong

[Mr X]

Thanks for the replies...Been away from work for a few days.

I've just been driving up the highway all weekend & up big hills full-throttle in 4th it's just hitting 700 C.

The placement of the sender was on the advice of my regular 4WD workshop & the diesel shop that custom fitted the I/C. The I/C was as much for reliability as the power/torque (not that I'd give that up - beautiful to drive now!) & I was given the impression that it was tuned a tad conservatively.

I rang up before the weekend & was told 750 C was pretty safe....

I'm wondering what the temps would be like for the guys running a lot higher boost (& turning up the fuel, I assume).....

X.

[MarkR]

Are you running a top mount or front mount I/C?

[Mr X]

Front.

[eliteforce32]

X..... can i just ask as i have a top mounted I/C does ur cooling for the radiator heat up more? sorry to hijack but just interested.....and how did u mount it ? cheers elite

[dumbdunce]

I rang up before the weekend & was told 750 C was pretty safe....

I'm wondering what the temps would be like for the guys running a lot higher boost (& turning up the fuel, I assume).....

X.

750C pre turbo is pretty safe but don't let it go much higher, with the 2L-T there is a real risk (and I mean REAL, it happens all the time) of cracking and dropping a precombustion chamber cup into the cylinder, and this obviously makes a real mess of your engine in a very short time.

if you're in the mood for experimenting it would be good for you to stick a couple of cheap thermocouples in your inlet airstream pre and post intercooler, and another in the ambient inlet airsteream (in the air filter) to get an indication of the effectiveness of your intercooler and the efficiency of your turbo. if you are still running the CT20 factory turbo and it has not been high flowed, running an intercooled 11psi from it is well outside its optimum efficiency and your engine is working a fair bit harder than it needs to to make the power, especially in terms of oil and water temperatures generated in the turbo. almost ANY turbo is better than the stocker - a garrett off a smallish Nissan in the 1.8 to 2.5 litre range will work better across the rev and boost range and should only set you back a few hundred at a wreckers.

other dangers when running a 2L-T hard (extra boost) include failed big end bearings (use a premium, high calcium jap spec 15W40 oil, do not be tempted to thicker), and high revving has been known to snap the ends off the valves, dropping the valve into the cylinder. The head will crack, it's just a matter of time until the cracks propagate into the water jacket. it's not a matter of IF, but when. by all means run it hard (I sure did with mine) but don't expect it to be a bulletproof engine.

cheers

Brian

[Mr X]

Hey Dumbdunce,
Thanks for the info...... but now my brain hurts!!!!! Could you pls explain what high-flowing is & how other turbos are more efficient. Are you talking about turbine size? Where does the CT20 fit in the scheme of Garrets, DTS etc....

When I was having the engine rebuilt last year I asked about different turbos & was told " why get a different one, 7 PSI is 7PSI, 9PSI is 9PSI etc regardless of the turbo" (obviously coming in at different revs depending on size. Also, what do you consider high boost for the 2LT?

....Kinda wishing we had this discussion BEFORE I pulled out the Visa.....
Much appreciated.

Elite,
It was a full custom job. Nothing had to be moved, just the I/C size & mounts had to be customised. I haven't noticed any cooling differences yet on the highway or crawling along. The test will be in sand --> low speed / high load....

X.

[dumbdunce]

Hey Dumbdunce,
Thanks for the info...... but now my brain hurts!!!!! Could you pls explain what high-flowing is & how other turbos are more efficient. Are you talking about turbine size? Where does the CT20 fit in the scheme of Garrets, DTS etc....

the CT20 is a toyota turbo. it is (obviously) mass produced and not particularly high quality. It is slightly undersized for the 2L-T (deliberately) to provide quick spool up and reasonable boost at lower RPM. it is hard to place any turbo in a lineup with others as the numbers that describe a turbo are actually quite complex. as well as the general spec, like CT20, CT26 etc, there are the A/R ratios of both compressor and turbine, and the efficiency maps of each. There are also different kinds of spindles and bearings, which all add up to litereally thousands of different turbo combinations.

When I was having the engine rebuilt last year I asked about different turbos & was told " why get a different one, 7 PSI is 7PSI, 9PSI is 9PSI etc regardless of the turbo" (obviously coming in at different revs depending on size. Also, what do you consider high boost for the 2LT?

that is rubbish and shows a complete lack of understanding of turbo technology. the sizing and design of the turbo has an impact on the critical bit of information that is usually glossed over in turbo discussion. EFFICIENCY. 7psi at 75% compressor efficiency is a LOT more useable boost than 7psi at 45% efficiency. The efficiency of the compressor is the ratio of (energy imparted to the inlet charge as a pressure increase) : (all energy imparted to the inlet charge), and most of the other energy imparted to the inlet charge is HEAT. as you increase boost with a stocker turbo, you gradually push the compressor (and usually to a lesser degree the turbine) beyond its efficient operating range, so that, for example as you increase boost 20% (7psi to 8.4psi), you need 30% more power to the compressor - the extra 10% goes to heating the inlet charge, and the extra 30% makes the turbine work that much harder (ignoring for a moment the issue of turbine efficiency). that's not so bad. if you want another 20% boost increase (to 10psi), your compressor is getting well beyong its peak efficiency and you might need another 40% turbine shaft power to get that extra bit of boost. around 11psi is the limit for the stock CT20 turbo on a 2L-T and at that boost, at 2800rpm, from memory mine was running under 50% efficiency (ie HALF of the turbine power was just heating the inlet charge). With a better turbo you can get the same boost for far less load on the turbine and far less heating of the inlet charge - that means two things:

less turbine load = less exhaust backpressure = more crankshaft power.

lower inlet charge temperature = more mass air flow for a given boost pressure = more power.

there are also side benefits like lower combustion temps (and therefore EGT's), less load on the cooling system, less stress on the oil and engine internals etc. All these things are within very safe ranges with the engine in stock trim but as you wind up the boost, even with an intercooler, it all goes out of "safe" ranges fairly quickly.

with a thermocouple before and after the turbo, with some not too difficult matchs, you can calculate the compressor efficiency for different RPM/load scenarios. the only one that counts is peak boost at full load really. you only need cheap multimeter type thermocouples. you can do the same thing on the exhaust side but you need two expensive EGT thermocouples and ideally a pressure gauge on the high pressure side, it's not quite as critical as the inlet side.

internally stock, with intercooling and high-flowed (compressor housing machine to accept a slightly larger compressor wheel) turbo or decent aftermarket turbo, a 2L-T will tolerate around 12psi boost, maybe a little more if you carefully watch the EGTs.

hope this helps. There is a lot of good info on turbocharging and how to do it right on the www. have a search and a read.

cheers

Brian