Na->Turbo - Page 2 - PeachParts Mercedes-Benz Forum

leathermang · #16 09-01-2015, 11:43 AM

Quote:

Originally Posted by Diesel911

......I am guessing it aids in buring Fuel that might not get completaly burned under acceleration and since it would raise the comression ratio some it could help low compression issues after the Turbo stats to boost which would allow the Fuel to burn more completely.
Of course aaltitued performance should be better.

How would it aid in burning Fuel ?

Since our engines do NOT have an accelerator pump... which gas engines do...and do waste some gas in support of increased power... why do you think a turbo itself would help that 'complete burning'... as compared to a more accurate setting of the curve built into the cam on the IP or better tuning of the injectors ?

It would NOT raise the compression RATIO..

that is strictly a function of the stroke and the relative area above the piston at the top of the stroke compared to the volume of the cylinder with the piston at the bottom of its stroke.

That ratio is SET by the engine design... not affected by more or less air pressure. To get more power an appropriate amount of fuel with regard to that extra air must be provided.

Tmadia · #17 09-01-2015, 01:40 PM

Quote:

Originally Posted by leathermang

How would it aid in burning Fuel ?

Since our engines do NOT have an accelerator pump... which gas engines do...and do waste some gas in support of increased power... why do you think a turbo itself would help that 'complete burning'... as compared to a more accurate setting of the curve built into the cam on the IP or better tuning of the injectors ?

It would NOT raise the compression RATIO..

that is strictly a function of the stroke and the relative area above the piston at the top of the stroke compared to the volume of the cylinder with the piston at the bottom of its stroke.

That ratio is SET by the engine design... not affected by more or less air pressure. To get more power an appropriate amount of fuel with regard to that extra air must be provided.

It would indeed raise compression. You are talking about static compression ratio, which is the mechanical definition, but there is also dynamic compression, which takes cam timing and forced induction into account.

Wallace Racing: Dynamic Compression Ratio Calculator

The increased heat of compression may help burn more completely, but I wouldn't bet on it. Like everyone is saying, without more fuel there won't be noticeable gains.

vstech · #18 09-01-2015, 02:27 PM

Quote:

Originally Posted by soates4

I know what you all are going to say. i know that its a terrible idea. i know the stock 240d internals cant handle it, i know i dont have oil squirters. Don't care. wanting to set up a junkyard turbo build run very little turbo and max boost out below 7 psi to safetly continue to daily drive the slowest car on the east coast. lol. ive seen it done and looks to be the easiest car ever to turbo. turbo, lines, manifold, exhaust. done. thats the beauty of a all mechanical ran car i guess. any one have any turbo suggestions. or tips? also looking for a manifold if you know one. its a 1974 w115 om616 engine

ok soates4...

unless you live in high altitude, or you make modifications to the injection pump, or replace it altogether for a fuel supplemented pump... or you plumb in Propane or similar fuel additives...

a turbo will simply do nothing for the motor but make noise.

interzonearts · #19 09-01-2015, 04:49 PM

Quote:

Originally Posted by Diesel911

Well there is a small suprize. The Oil that drains from the Turbo drains mostly by gravity. The Turbo Drain has to be above the level of the Oil in the Oil pan or the Oil inside of the Turbo builds up and your Turbo Seals leak.
How do I know that? I worked in a Fuel Injection Shop that also rebuilt Turbos. We also did some work on the Big Rig Diesels and removing and insalling Turbos was one of them.
In short I have seen Truckers overfill their Engine with Oil to a level that blocks off the Oil Drain and their Turbos leaked Oil because the Oil would not drain out.

Also note that on Engines like My 300D the Turbo inlet Oil line has a 2mm restriction in it.

Good point, it can be done though.

Diesel911 · #20 09-01-2015, 09:05 PM

Quote:

Originally Posted by leathermang

How would it aid in burning Fuel ?

Since our engines do NOT have an accelerator pump... which gas engines do...and do waste some gas in support of increased power... why do you think a turbo itself would help that 'complete burning'... as compared to a more accurate setting of the curve built into the cam on the IP or better tuning of the injectors ?

It would NOT raise the compression RATIO..

that is strictly a function of the stroke and the relative area above the piston at the top of the stroke compared to the volume of the cylinder with the piston at the bottom of its stroke.

That ratio is SET by the engine design... not affected by more or less air pressure. To get more power an appropriate amount of fuel with regard to that extra air must be provided.

Maybe Compression Ratio was a bad choice Because it deals with fixed volumes.

What the Turbo does is effectively increases the Engine Displacement which increses the measured Compression because a larger density of Air is in the Cylinder.

Most of Air is Nitrogen. When the Air is compressed in a Cylinder and the Fuel burns some of the Fuel does not get burned because it is only exoposed to Nitrogen. Higher Compression helps the Fuel burn more completely because the Oxygen Molecules are closer together and have a better chance to be exposed to the Fuel.

When the Turbo charger is boosting it does indeed raise the Compression Ratio in the Cylinder (because the boost pressurized Air is packing in more air volume into the cylinder before the Piston is coming up on the compression stroke) and that does what I indicated in the above Paragraph. Higher Compression Ratio in the Cylinder also means the Air is also hotter which also aids in combustion.

Perhaps one of our Members who has and likes to use Math skills can figure out how much more Air goes into the Cylinder on one intake Stroke when the Boost Pressure is 5 psi above Atmospheric Pressure and get back to us.
And, use that to calculate the difference in Compression.
　
Xcceleration

Also the Guy that added the STT Turbo Kit to the formally NA 300D gave his results and followed up the results in a later Post. He claimed an improvement in power.

However, it is also important that he used a kit that was designed for the purpose. That means that a Turbo was picked that would operate with some efficiency for the application.

Mxfrank · #21 09-01-2015, 09:59 PM

Quote:

Originally Posted by Diesel911

Maybe Compression Ratio was a bad choice Because it deals with fixed volumes.

What the Turbo does is effectively increases the Engine Displacement which increses the measured Compression because a larger density of Air is in the Cylinder.

Most of Air is Nitrogen. When the Air is compressed in a Cylinder and the Fuel burns some of the Fuel does not get burned because it is only exoposed to Nitrogen. Higher Compression helps the Fuel burn more completely because the Oxygen Molecules are closer together and have a better chance to be exposed to the Fuel.

When the Turbo charger is boosting it does indeed raise the Compression Ratio in the Cylinder (because the boost pressurized Air is packing in more air volume into the cylinder before the Piston is coming up on the compression stroke) and that does what I indicated in the above Paragraph. Higher Compression Ratio in the Cylinder also means the Air is also hotter which also aids in combustion.

Perhaps one of our Members who has and likes to use Math skills can figure out how much more Air goes into the Cylinder on one intake Stroke when the Boost Pressure is 5 psi above Atmospheric Pressure and get back to us.
And, use that to calculate the difference in Compression.
　
Xcceleration

Also the Guy that added the STT Turbo Kit to the formally NA 300D gave his results and followed up the results in a later Post. He claimed an improvement in power.

However, it is also important that he used a kit that was designed for the purpose. That means that a Turbo was picked that would operate with some efficiency for the application.

It's hard to read posts like that, so much confusion and misinformation in such a small space. The stochiometric ratio for diesel is almost the same as gasoline....14.5:1 air to fuel. Since Diesels are controlled by fueling the actual air/fuel ratio is varied by the accelerator pedal, but is ALWAYS over stochiometric. Anywhere from 1000:1 to 20:1 depending on speed and load. If you get below 20:1, you get smoke, and that's the only time more air helps. But if your car smokes, it probably has weak compression, bad timing, or a bad injector, which means the engine is too worn for upgrades. There is always sufficient air.

Static compression ratio is determined by the bore and stroke, nothing else. Dynamic compression ratio is determined by bore, stroke, and cam, before you consider the turbo...the equations in your article are just wrong. The reason for this is that your intuitive notion of how an engine works probably isn't correct: the cam doesn't snap the valve shut at BDC, but rather has a ramp... on a 60x, for example, the intake valve doesn't close fully until 17 degrees after BDC.

If you want the truth about how it feels to add a turbo to an NA car, there's no need to play with words or numbers. Get someone with a turbo to loan you their car, and disconnect the Alda line. That will prevent fuel enrichment, and you will see how well it's really going to work.

I know there are people on the net who claim all kinds of things from turbos, cold air intakes, pod air filters, etc. Let me tell you how to interpret this information: nobody does a stupid, expensive upgrade without boasting about it or evaporating into the ether...admitting the mistake in a public forum will never happen. Do you expect them to say, I just spent two large on a turbo upgrade, and the car is still a slug? No, they lie, or maybe just disappear after a lot of noise.

leathermang · #22 09-01-2015, 10:41 PM

Diesel911,
I think you have made several assumptions about combustion for which there is no evidence to support them.... I am going to try to keep this really short and address the largest one... Which is described in this course work from Washington.edu...

Your assumption about increasing the heat from the already high 21.5 ( approx depending on engine ) meaning more complete burning of the fuel does not apply to our diesels.... as they already intentionally burn lean on fuel ... meaning there is plenty of oxygen at sufficient heat to support their combustion.

https://en.wikipedia.org/wiki/Internal_combustion_engine
""""Most steel engines have a thermodynamic limit of 37 %. Even when aided with turbochargers and stock efficiency aids, most engines retain an average efficiency of about 18 %-20 %""""

Improving IC Engine Efficiency

"""However, the diesel engine is not subject to this limitation. It runs at high compression ratio. In part, this explains its high efficiency. It also runs lean, and its pumping work is low, further increasing its efficiency over the gasoline engine. Humankind needs quiet, smoke-free, odor-free diesels!"""

https://en.wikipedia.org/wiki/Combustion
'''Solid and heavy liquid fuels also undergo a great number of pyrolysis reactions that give more easily oxidized, gaseous fuels. These reactions are endothermic and require constant energy input from the ongoing combustion reactions. A lack of oxygen or other poorly designed conditions result in these noxious and carcinogenic pyrolysis products being emitted as thick, black smoke.''''

Edit.. Thank You MXFrank... well said.

interzonearts · #23 09-01-2015, 10:51 PM

Adding the turbo would not increase the max power output without increasing fuel delivery. Actually it may cause problems at high rpms (and that where the rated power comes to life) if it's not chosen right.

However it would increase top torque and if it's a small turbo that spools quickly it'd lower the peak torque rpms, The higher the rpms the harder the engine needs to work just to turn itself over so if it's able to do more work at lower rpm it'll become more efficient. And also if it pulls stronger at lower rpms the car will accelerate quicker and that seems to be what OP wants.

As the saying goes power sells cars but torque wins races, Horsepower determines the top speed but lbs/ft determine how fast you get there.

I don't know if i'd put a turbo on this particular engine but i can relate to feeling uncomfortable driving a sluggish car in modern traffic especially where i live. A lot of people drive like morons here and chase each other from one red light to another. It'd would not concern me that much but i feel bullied by cars behind me a lot of times if i drive in what i would consider a sensible way.

Anyways, i'm buying a slow moving vehicle sign for the back of my truck and see if that makes a difference

leathermang · #24 09-01-2015, 11:03 PM

Quote:

Originally Posted by interzonearts

Adding the turbo would not increase the max power output without increasing fuel delivery.......

That is the defining TRUE statement of your post.
All the rest of the statements are totally dependent on that true statement..

Diesel911 · #25 09-01-2015, 11:57 PM

Interesting stuff from Chilton's Guide to Diesel Cars and Trucks by James Joseph
Page #64

"A turbocharger ups diesel volumetric efficiency in several ways. First, no matter how efficient a diesel, on the downward air-intake stroke its pistons cannot take in the full air capacity of their cylinders. On an engine with 300-cubic inch displacement its pistons pull into the combustion chambers only about 85 percent. Turbocharging not only makes up this 15 percent volumetric deficit, but often increases volumetric efficiency far beyond the 100 percent level--to as much as 1.6 (160%) of capacity, nearly doubling volumetric efficiency. On the 300SD, the turbocharger increases the horse power from 77 to 120 and boosted the maximum torque from 115 to 168 ft/lbs, while adding only 33 pounds to the engine's dry weight.

The greater its air supply the greater a diesel's efficiency. One outward sign of a Turbodiesel's increased efficiency is turbocharging's virtual elimination of exhaust smoke, the telltale of unburnt, wasted fuel. As little as 1 percent unburnt fuel can cause objectionable exhaust smoke. In doing away with most smoking turbocharging overcomes one of diesel paradox: the fact that a diesel, even with only 85 percent volumetric efficiency, almost always has an over supply of air, although not necessarily a great enough oversupply to permit every fuel molecule to find sufficient air for combustion."

I did not know the part highlighted in blue quoted from the Book.

Also a NA Engine is pulling in only 85% of the Air into the Cylinder that means it is not reaching the theoritical compression ratio or in fact compression.

If that is true then supplying the cylinder with 100% of the Air would bring it up to the theoritical Compression Ratio and raise the compression and if you supply more then 100% of the Air due to to the boost pressure the compression will go higher.

Higher compression burns the Fuel more efficiently.

The part in highlighted in read supports the idea that adding a turbo but not increasing the amount of Fuel during boost could yield more power due to the burning of Fuel normally would not be burned if the Engine was still NA.

The Author of the Article in the Book did not say at what rpm the only 85% of the Air makes it into the Cylinder on NA Engines. I am speculating that at idle speed is when you get the most Air in because that allows the most time for the Air to get in.

As was partly related in another post as the Engine rpms increase on a NA Engine there is less time Air at Atmospheric Pressure to get into the Cylinder. Less time to get in means less Air gets into the Engine. That means there is another reason performance is going to fall off.

Having a Turbocharger even if you do not increase the Fuel can erase that poorer Air intake at higher rpms.

leathermang · #26 09-02-2015, 12:16 AM

Diesel911,
You are forgetting about the fact that the diesel is already running lean on fuel... so increasing the temperature by turbo addition does nothing WITHOUT ADDING an appropriate amount of fuel.

And I am not sure you can support the idea that on a high compression engine like ours... that even the fact that adding more air does increase the final compression temperature some.... that once past the needed temperature to ignite the fuel...which was already extant..... does anything to increase power.... nothing supports that notion.

interzonearts · #27 09-02-2015, 01:16 AM

Quote:

Originally Posted by Diesel911

The part in highlighted in read supports the idea that adding a turbo but not increasing the amount of Fuel during boost could yield more power due to the burning of Fuel normally would not be burned if the Engine was still NA.

True, but getting more air in will require more work to compress it so at least some of the energy recovered by more efficient burning would be used to produce it. I'm guessing but the net gain if any would be marginal.

Even if one is an optimist and assumes 1% increase in efficiency that'd give the engine 65.65 instead of 65 hp. I don't imagine anyone would notice a difference.

One will notice the difference in torque in lower rpms but i said it already..

Diesel911 · #28 09-02-2015, 01:36 AM

Quote:

Originally Posted by leathermang

Diesel911,
You are forgetting about the fact that the diesel is already running lean on fuel... so increasing the temperature by turbo addition does nothing WITHOUT ADDING an appropriate amount of fuel.

And I am not sure you can support the idea that on a high compression engine like ours... that even the fact that adding more air does increase the final compression temperature some.... that once past the needed temperature to ignite the fuel...which was already extant..... does anything to increase power.... nothing supports that notion.

I am not forgetting about that but I am also not forgetting that all of the Fuel does not burn and if you can get that fuel to burn your performance will incease.

I guess you don't believe that when the Guy installed the Turbo Kit on his formally NA 300D that he got better peformance as he said he did?

Diesel911 · #29 09-02-2015, 01:56 AM

Quote:

Originally Posted by interzonearts

True, but getting more air in will require more work to compress it so at least some of the energy recovered by more efficient burning would be used to produce it. I'm guessing but the net gain if any would be marginal.

Even if one is an optimist and assumes 1% increase in efficiency that'd give the engine 65.65 instead of 65 hp. I don't imagine anyone would notice a difference.

One will notice the difference in torque in lower rpms but i said it already..

I guess you don't believe that when the Guy installed the Turbo Kit on his formally NA 300D that he got better peformance as he said he did?

I have tried to back my opinion with some facts. But, today the learning curve is too steep and it is hard to find specifics on Diesels.

There was at least 2 threads on gasoline engines where they said raising the compression in the Cylinder increased gas expansion during combustion reguarless of the extra Fuel or if there is a turbocharger.

So perhaps that increased gas expansion compensates for that extra work compressing the Extra Air supplied by the Turbo.

Also energy is used up creating the low pressure in the cylinder as the Piston is going down due to the fact the Intake port with Intake Valve is a restriction.
When the Turbo is boosting the energy that is needed to create the low pressure in the cylinder is not needed. So there is an energy savings there.

The Turbo itself is not a parisite on the Engine after it starts boosting.

So when Turbo is boosting compression goes up causing increased exhaust gas expansion pushing down on the Pistons and the Engine does not have to work at creating a low pressure to intake Air.
Apparently that is enough to give the engine some extra power it did not have before the Turbo was added.

Also if you are on level ground the Turbo is not going to start Boosting right off and you won't get that extra low end torque you speak of.

However, when the Car starts going up the a Hill that changes because the pressure in the cylinders goes up wich increase the velocity of the Exhaust Gasses which turns the Turbo faster and sooner. So I could see the low rpm torque in that situation.

Diesel911 · #30 09-02-2015, 02:01 AM

Quote:

Originally Posted by Mxfrank

It's hard to read posts like that, so much confusion and misinformation in such a small space. The stochiometric ratio for diesel is almost the same as gasoline....14.5:1 air to fuel. Since Diesels are controlled by fueling the actual air/fuel ratio is varied by the accelerator pedal, but is ALWAYS over stochiometric. Anywhere from 1000:1 to 20:1 depending on speed and load. If you get below 20:1, you get smoke, and that's the only time more air helps. But if your car smokes, it probably has weak compression, bad timing, or a bad injector, which means the engine is too worn for upgrades. There is always sufficient air.

Static compression ratio is determined by the bore and stroke, nothing else. Dynamic compression ratio is determined by bore, stroke, and cam, before you consider the turbo...the equations in your article are just wrong. The reason for this is that your intuitive notion of how an engine works probably isn't correct: the cam doesn't snap the valve shut at BDC, but rather has a ramp... on a 60x, for example, the intake valve doesn't close fully until 17 degrees after BDC.

If you want the truth about how it feels to add a turbo to an NA car, there's no need to play with words or numbers. Get someone with a turbo to loan you their car, and disconnect the Alda line. That will prevent fuel enrichment, and you will see how well it's really going to work.

I know there are people on the net who claim all kinds of things from turbos, cold air intakes, pod air filters, etc. Let me tell you how to interpret this information: nobody does a stupid, expensive upgrade without boasting about it or evaporating into the ether...admitting the mistake in a public forum will never happen. Do you expect them to say, I just spent two large on a turbo upgrade, and the car is still a slug? No, they lie, or maybe just disappear after a lot of noise.

In other posts I am at least trying to take it beyond opinion by posting other sources. We will see how it pans out.

I guess you also don't believe what the guy that installed the turbo kit on his formally NA Engine and got better performance.