Turbo Diesel's unaffected by altitude (proof provided)

[Stewart]

You're absolutely right Green1. I regularly take my van up mountains and I also notice a bit longer turbo lag with resulting smoke ie runs rich. Cold start behavior is also different but of course that's before the turbo starts to create boost ie also rich. Normal driving with the turbo spooled up is fine but I had the Deli tune at CVI and make it a habit to ease into the throttle more on starts to let the turbo catch up.

Stewart

[FalcoColumbarius]

Okay, this thread has reached a new level. Although it is posted in "L400 Technical" we seem to be including experiences of L300 pilots, which leads me to the next question:

What difference does the Intercooler make with elevation? The L300 typically has no intercooler, where the L400 typically does.

Falco.

[Manitoba deli]

The altitude at which a turbo can no longer compensate for the lower air pressure is not printed in the text book, because for land and sea applications,(for which the book was written) it is not relevant, you cannot reach this elevation on wheels. As for the "magicalness" of a turbo compesating for lower air pressure, it becomes clear when you fully understand how a turbo with a wastegate functions. It is not magic, just simple physics. To argue with a text book seems pointless to me. Is anyone else having trouble understanding the text book explanation, or is it just one individual?

Jason

[Green1]

The altitude at which a turbo can no longer compensate for the lower air pressure is not printed in the text book, because for land and sea applications,(for which the book was written) it is not relevant, you cannot reach this elevation on wheels.

If it was irrelevant why'd the textbook bother to mention it? In fact the book DOES say what the altitude is, it says it varies based on the engine and the turbo, in our case, the turbo is not nearly big enough to do any significant elevation.
As for "airplane" level vs "car" level, keep in mind that the small planes flying around near the coast aren't flying much higher than I am driving near my house. (and turbo diesel engines don't exist on jetliners!)

As for the "magicalness" of a turbo compesating for lower air pressure, it becomes clear when you fully understand how a turbo with a wastegate functions. It is not magic, just simple physics. To argue with a text book seems pointless to me.

So at altitude does the turbo physically grow in size? does your exhaust suddenly push harder? where does it get this "extra" boost? you imply that at sea level it generates far more than it needs and dumps the excess, and then at altitude you use that excess... this is not the case, it uses ALL of it at sea level, meaning at altitude there is less to go around.
The Turbo has no way of generating more boost at higher altitudes than it does at lower altitudes, the effect tapers off, starting right at sea level, the higher you go, the less boost available.

The book agrees that the turbo GREATLY helps vs a non-turbo engine, but does nothing to prove that it can magically continue to provide infinite boost no matter how high you go.

Is anyone else having trouble understanding the text book explanation, or is it just one individual?

nope, so far just you.

[Manitoba deli]

The first step is to admit there is a wastegate. The second step is to learn how it works.

Jason

[Green1]

The first step is to admit there is a wastegate. The second step is to learn how it works.

So the wastegate magically generates more boost from less air? you want to explain exactly where that comes from?

If the wastegate was dumping extra boost at sea level, it could close to provide more at altitude, but since we DON'T dump all our boost at sea level (we actually USE it) it can't MAKE more, it's just a valve.
What you are describing is how aircraft turbo diesels work, not automotive ones.

[Manitoba deli]

I will try to explain a wastegate. It is controled by boost pressue. when the desired boost pressure is reached, the wastegate dumps excess exhaust (which is used to generate boost). If more boost is required, the wastegate sends more exhaust through the turbo. If you were to unhook the wastegate, and plug the pressure relief, the turbo will generate enough boost to seriously damage your engine.

Jason

[Green1]

I will try to explain a wastegate. It is controled by boost pressue. when the desired boost pressure is reached, the wastegate dumps excess exhaust (which is used to generate boost). If more boost is required, the wastegate sends more exhaust through the turbo. If you were to unhook the wastegate, and plug the pressure relief, the turbo will generate enough boost to seriously damage your engine.

Where can I buy one of these "infinite boost" turbos you keep talking about?

The turbo is powered by exhaust gas, it can't spin any faster than the exhaust gas moves, which means it can't spin the fan on the intake side any faster either. we don't have tons and tons of "spare" boost sitting there for the taking, it just doesn't exist. in addition, the higher you go in altitude, the less air you have on the intake side, AND the less exhaust you have on the output side, you also have less pressure pushing on your valves to keep them shut.
All of this means that the higher you go, the LESS boost available (less created, and more dumped)

Mitsubishi didn't design the vehicles with a turbo big enough to output several times the boost needed, they made it with one capable of generating the amount they though you would need, it doesn't generate all this magical extra boost you claim it does just so that it can vent it to the atmosphere.

[psilosin]

Where can I buy one of these "infinite boost" turbos you keep talking about?

Any turbo can pretty much wind itself up to the point of destroying itself and/or the engine. Hence the MFking wastegate... Only an idiot thinks in black and white like you. Your turbo can generate a lot of boost well beyond safe operating conditions. Only an idiot like you would take that to the extreme to mean infinite.

Mitsubishi didn't design the vehicles with a turbo big enough to output several times the boost needed, they made it with one capable of generating the amount they though you would need, it doesn't generate all this magical extra boost you claim it does just so that it can vent it to the atmosphere.

Whats with the several times BS Mr. MyTurboHasNoWastegate? It was already shown mathmatically that the difference in absolute pressure your mechanicals operating at the same relative pressure would experience in Calgary on a vehicle tuned at seal level would be less than 3psi. Thats hardly a bump and would be EASILY handled by your turbo if you chose to do so. Thats like a 25% or less increase in output...not 200-300%.

I think that maybe the reason your Delica can magically run at equal power to one at sea level by ONLY REDUCING fuel is because Mardy added a custom high altitude compensator to your engine that scavanges and burns all the methane that accompanies the manure you ceaselessly spews from your mouth.

[mararmeisto]

At the rate this thread is progressing, altitude-compensated-infinite-boost-waste-gating turbo or otherwise, I'm going to run out of popcorn before the weekend.

[Mr. Flibble]

At the rate this thread is progressing, altitude-compensated-infinite-boost-waste-gating turbo or otherwise, I'm going to run out of popcorn before the weekend.

The trick I found is you don't pop it yourself, you just scatter the kernels over this thread and the heat pops them for you!

*EDIT*

I just have to add XKCD to my post:

[Green1]

Your turbo can generate a lot of boost well beyond safe operating conditions.

So again you think that mitsubishi designed the vehicle to generate way more boost than it would ever need, just so that it can vent all the extra to the outside world... so if that is the case, why do people keep talking about adding bigger turbos? obviously the one they already have can generate WAY more boost than anyone could ever use (and according to you it doesn't even need modifying to do it! all people have to do is "CHOSE" extra boost and it happens!)

It was already shown mathmatically that the difference in absolute pressure your mechanicals operating at the same relative pressure would experience in Calgary on a vehicle tuned at seal level would be less than 3psi. Thats hardly a bump and would be EASILY handled by your turbo if you chose to do so. Thats like a 25% or less increase in output...not 200-300%.

And what difference does the percent make? it doesn't matter if it's 1000% or 0.1%, the difference is what effect it has on combustion, diesel engines need a specific air-fuel mix, changing it away from optimum (either high or low) will reduce your power and generate smoke. that's what we're talking about here, reduced power and extra smoke.
And how do you "choose" to add boost? the turbo has no way of knowing what altitude it is operating at, it has no way of knowing it needs to provide more boost, and it has less and less ability to do it due to less air coming in and less exhaust going out. add to that the fact that the very tool you think would help the situation would actually make things WORSE by opening even more easilly at altitude and venting even MORE of the boost you think will help.

Without some piece of the engine knowing the pressure that it is operating at, it will never be able to compensate for it, and the turbo simply doesn't know what pressure it is at.

[psilosin]

So again you think that mitsubishi designed the vehicle to generate way more boost than it would ever need, just so that it can vent all the extra to the outside world... so if that is the case, why do people keep talking about adding bigger turbos? obviously the one they already have can generate WAY more boost than anyone could ever use

Most people buying Bigger turbos are boosting well beyond factory levels on modified motors...they are not just doing little baby 3-5psi bump ups. 'Modding' your turbo to run at 10psi instead of 8psi for example (which is in the realm of what we are talkin about) is a non-issue. Your turbo at its factory boost setting is operating nowhere near its upper limit. No your turbo will not provide 30psi all day (but neither would your engine survive that) but if the wastegate and relief valve both failed it could most likely wind itself up to that and beyond before grenading.

(and according to you it doesn't even need modifying to do it! all people have to do is "CHOSE" extra boost and it happens!)

yes all you have to do is choose to add more boost...then make it happen...like I said already by either shimming the wastegate or using a bleed valve. As for tuning...look at boost gauge...want more? more shim, too much? less shim...done. Even you could do it.

diesel engines need a specific air-fuel mix

No they don't, gasoline engine do. Diesel engines do not operate on a specific schochiometric ratio like a gasoline engine.

changing it away from optimum (either high or low) will reduce your power and generate smoke

No, only too much fuel will cause smoking. Many people run additional boost without adjusting the compensator to continue adding more fuel as a way to attempt to lower EGTs while retaining the same power they had at a lower boost level.

And how do you "choose" to add boost?

You hold your chin between your thumb and index finger and go "hmmmm i want more boost!!"...and then make the adjustment. This is an actual adjustment Green1, that someone tuning an engine for high altitude might do...as opposed to JUST TURNING DOWN THE FUEL, which will only reduce smoking (again primarily only during off boost)...at the expense of power.

You also fail to acknowledge that the original posters symptoms developed over time which continues to beg the question...maybe the massive black smoke and loss of power are NOT just elevation related....just bringing that up again to remind you.

There are two distinct conversations going on here. 1) is about the original posters symptoms and possible solutions and 2) your (mis)understanding of turbos and diesels. Not every comment being made in regard to functioning of turbos etc even applies to the OP's issue so don't confuse that, they are just in response to your false statements about how things work.

If you could get past your hubris you could actually contribute to a useful discussion on what kinds of adjustments you CAN make to a turbo diesel operating at high altitudes to decrease smoke AND maintain or even increase power over stock power. Your pigheaded continued belief in 1) that less fuel is the only adjustment that may be made and how that magically increases power and 2) defending that position with untrue information about how turbos work serves no purpose other than comic relief.

If you have an EGT and a Boost gauge installed, you should leave the computer alone, go outside, and actually start messing around with some of your engines turbo and IP components and get some hands on knowledge. Start with a lttle shimming of the wastegate and notice the increased boost available during accelerating. Then mess around carefully with the IP fuel delivery and and see how they interact both on and off boost. Then if you are lucky enough to have a mechanical boost compensator on the L400, which someone said it does, you can start to have a lot of fun messing with the delivery ramp. Once you get a handle on all that you can REALLY tune your engine however you want it.

[deLOOKA]

At the rate this thread is progressing, altitude-compensated-infinite-boost-waste-gating turbo or otherwise, I'm going to run out of popcorn before the weekend.

The trick I found is you don't pop it yourself, you just scatter the kernels over this thread and the heat pops them for you!

*EDIT*

I just have to add XKCD to my post:

I'm still laughing while typing this down. Where do you find these images?


As much as parts of these postings are confusing for me, I have to say that i'm quite impressed with both parties.

-Delooka

[Green1]

diesel engines need a specific air-fuel mix

No they don't, gasoline engine do. Diesel engines do not operate on a specific schochiometric ratio like a gasoline engine.

If that doesn't underline your complete lack of understanding of the internal combustion process... Fuel doesn't burn without oxygen... it never has, and never will, doesn't matter if you're talking diesel, gas, wood, paper, magnesium, or ANY other combustible material, the air and fuel always have to mix in an appropriate ratio for complete combustion to occur. if you don't get enough air, the fuel will not burn completely and you'll get smoke, you'll also loose power as you choke out any complete combustion that could have happened.

changing it away from optimum (either high or low) will reduce your power and generate smoke

No, only too much fuel will cause smoking.

Too much fuel will cause black smoke, too little fuel will cause white smoke, either way, in this particular case we're talking about too much fuel, so that means black smoke.

And how do you "choose" to add boost?

This is an actual adjustment Green1, that someone tuning an engine for high altitude might do...

Finally!!!!!! you finally get that an adjustment needs to be made, before this post you have always insisted that the vehicle magically does it all itself... but you finally admit I was right all along and something needs to be adjusted!

Unfortunately you picked the wrong thing.... and here's the reason, increasing the boost only helps when you are already maxing out the boost, as you don't always run at full boost, it means that your solution doesn't always work. (Now if you find a way to increase the amount of boost provided over the enitre range, starting right at idle, then you'd have a point, but all your proposed solution does it increase the top end, not raise the whole range)
turning down the fuel though will work, regardless of boost level, now if you turn down the fuel, you will get rid of your smoke at all boost levels, at the expense of a small amount of power (when compared to operating at sea level with full boost) however you will INCREASE your power as compared to a vehicle that has not been adjusted and is dumping too much fuel in for the amount of air it is receiving.

You also fail to acknowledge that the original posters symptoms developed over time which continues to beg the question...maybe the massive black smoke and loss of power are NOT just elevation related....just bringing that up again to remind you.

You fail to offer any other explanation (except that he should blank his EGR, which he had already done), as for "over time" the longer you run with too rich a mixture, the worse the problems get as that black smoke you see is also covering everything inside the engine with soot and gumming up the works.
The good news is that after fixing the problem by decreasing the fuel level, a few good highway trips will clean out the carbon build up and have 'er good as new.