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Engine Specific Info and Questions => IDI Engine => Topic started by: 8v-of-fury on March 02, 2012, 10:36:19 pm
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it goes now pretty good, after ~17psi I don't feel much change in power. i notice that the EGT drops when the boost hits which is nice.
thats because your turbo is pushing more air than needed.. if you have marginal fueling, and lots of boost, it will make less power that way, rather than having decent fueling, and marginal fueling..
if you havent cranked up your fuel screw, then i would back the boost down to about 12-13 psi.. there is absolutely no reason to run that much boost to an engine with stock fueling..
Is boost not directly affected by how much fuel you are giving? Stock fueling is only good for x amount of boost. Why limit it? If stock fueling wants to make 15psi whats wrong with that?
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it goes now pretty good, after ~17psi I don't feel much change in power. i notice that the EGT drops when the boost hits which is nice.
thats because your turbo is pushing more air than needed.. if you have marginal fueling, and lots of boost, it will make less power that way, rather than having decent fueling, and marginal fueling..
if you havent cranked up your fuel screw, then i would back the boost down to about 12-13 psi.. there is absolutely no reason to run that much boost to an engine with stock fueling..
Is boost not directly affected by how much fuel you are giving? Stock fueling is only good for x amount of boost. Why limit it? If stock fueling wants to make 15psi whats wrong with that?
stock fueling will let the turbo explode with boost.. like literally grenade..
there is no reason to be running more boost than you have fuel for.. you are actually going backwards if you have 10psi worth of fuel to burn, and you are burning it with 20psi.. the piston has to fight the boost before TDC.. so you are actually LOSING power by running MORE boost than it takes to make the car run efficiently..
TOO MUCH BOOST for a given amount of fuel is bad..
do you think you would get more power from a small fuel charge and 10psi, or a small fuel charge, and 20psi?
well, of course with marginal fueling, you want marginal boost..
you WILL make less power with TOO MUCH boost..
this topic has been gone over many times before..
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stock fueling will let the turbo explode with boost.. like literally grenade..
Stock fuel levels can produce enough boost to grenade a turbo.. Ok, but at what RPM? Gotta be something above what our diesels spin. I have driven a bone stock TD (with stock fueling) and the waste gate does not bleed boost off. So this tells me stock fueling cannot even produce the 12-13psi needed to open the stock waste gate.
there is no reason to be running more boost than you have fuel for.. you are actually going backwards if you have 10psi worth of fuel to burn, and you are burning it with 20psi.. the piston has to fight the boost before TDC.. so you are actually LOSING power by running MORE boost than it takes to make the car run efficiently..
If you have enough fuel to produce 10 psi of boost (because the boost in said engines is directly related to fuel injected, ie. energy to spin the turbine) how are you making 20psi of boost? You have got some things jumbled up with how you are understanding this. Yes too much boost is bad, but not while your still in the efficiency range of the turbo. If you have the fuel set so you can produce 25-27psi out of a T3 and you make X amount of power, you can make X amount of power with less fuel and have boost somewhere in the turbos efficiency range. But this only applies when you have exceeded the turbos range of efficiency.
TOO MUCH BOOST for a given amount of fuel is bad..
Well no not really, because you cant have boost without fuel. So therefore, really.. Too much fuel for a given amount of air is bad.. That is why the OP said from 18 psi up to 22psi he did not feel anymore power. Too much fuel, not enough air.
do you think you would get more power from a small fuel charge and 10psi, or a small fuel charge, and 20psi?
If the fueling remained exactly the same? and did not change one bit? You would have WAY more power with X amount of fuel and 20psi then you would have with X amount of fuel and 10psi. Because if you had enough fuel to support 20psi.. then you have too much fuel for 10psi.
well, of course with marginal fueling, you want marginal boost..
What is marginal? For power you want as much boost and fueling as your entire setup can handle. Efficiently. If your turbo can efficiently produce 18psi, and you can provide enough fuel to do so without raising EGT's too much then you have found your systems maximum power for smallest amount of fuel given. Add an inter cooler, drop the EGT's, cool the charge air. You can now effectively run MORE fuel while maintaining the same boost level, Within the turbo's efficiency range.
you WILL make less power with TOO MUCH boost..
Too much only meaning outside of the turbo's efficiency. What happens when you have a big turbo that can support big boost? is it gonna make less power too?
Yes it has been gone over before, yet you still don't quite grasp how it works.. Interesting.
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my VNT would make 30+ psi on stock fueling from a n/a pump.. it was SLOW!
i made WAY more power with lots of fuel and 15psi than i did with no fuel and 30 psi..
grasp it or not, it actually works that way..
think of boost as variable compression.. if you have TOO MUCH compression for a given application, it will HINDER performance..
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I don't know if we can quantify the data obtained from your VNT setup. It is known fact you never had the vanes hooked up or working properly. SO yeah vanes closed, i feel a small VNT, with its vanes closed, could reach those boost pressures with very little fueling. If it were properly working? I doubt it.
think of boost as variable compression.. if you have TOO MUCH compression for a given application, it will HINDER performance..
They are in direct relation though man. Now that you have a waste-gated turbo go turn your fuel way down and get back to us. I want you to see if you can still hit the same boost numbers.. but here lies the challenge, with the same amount of power as well.
I'm not hating on you man, I do this to everyone spouting incorrect information. Interwebz or real life.
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I don't know if we can quantify the data obtained from your VNT setup. It is known fact you never had the vanes hooked up or working properly. SO yeah vanes closed, i feel a small VNT, with its vanes closed, could reach those boost pressures with very little fueling. If it were properly working? I doubt it.
think of boost as variable compression.. if you have TOO MUCH compression for a given application, it will HINDER performance..
They are in direct relation though man. Now that you have a waste-gated turbo go turn your fuel way down and get back to us. I want you to see if you can still hit the same boost numbers.. but here lies the challenge, with the same amount of power as well.
I'm not hating on you man, I do this to everyone spouting incorrect information. Interwebz or real life.
one thing tho man, i never changed my vane position ever, as long as i had my VNT..
retarded timing and marginal fuel would make LOADS of boost..
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its not a secret.. too much boost for a given fuel quantity is a bad thing..
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one thing tho man, i never changed my vane position ever, as long as i had my VNT..
retarded timing and marginal fuel would make ASS LOADS of boost..
Then they must have been closed. I have read on here that people with open vanes not being able to build any boost at all.
its not a secret.. too much boost for a given fuel quantity is a bad thing..
No it is not a secret, but you are using this information in the wrong context. Fuel and boost being relative to one another, you can only have as much boost as you have relative fuel. Meaning so long as you are in the turbo's efficiency range there is no too much boost for a given fuel. If you only have enough fuel for 10 psi, you only have enough fuel for 10psi. You cant magically make the turbo produce 10 extra psi of boost with no additional fueling. Now if you have the fueling turned up so you can hit 20psi, and you turn the waste gate down to open at 10psi you do not have too much fuel for a given boost pressure because the waste gate bleeds off and the injection pump stops fueling for boost.
Please, prove everything I have said wrong. Go outside, turn your fuel down, and try and hit the same power and boost numbers. It is all I ask, and if you are right, it is a very simple simple way to shut me up ;).
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i made WAY more power with lots of fuel and 15psi than i did with no fuel and 30 psi..
I cannot fathom how this works. More fuel less boost, less fuel more boost.
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and i cant drive my car, so you are going to just have to figure it out..
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and i cant drive my car, so you are going to just have to figure it out..
I have it figured out lol. I have given you nothing but proof and logic to determine what happens with boost relative to fuel.
Until you can get your car operational, I cannot physically show you what I am talking about. I just ask for some qualitative answers to prove what you say is all eh?
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Excessive boost reduces engine efficiency by causing excessive back pressure on the exhaust side and will hurt power. The compression of the added air is not the issue. Compression of air is an effective spring and the energy of compression is recovered when the piston goes back down on the power stroke. 15psi with appropriate fueling will result in more power than 20 psi with the same fuel.
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Most of the time, more boost at the same fueling is due to too much heat. I understand what you are saying, Jeremy. Most of the time you want to maximize boost but once you are outside of the turbo's efficiency, you are just making hot air. For the vnt-15, it's efficiency drops drastically over 18 psi.
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Excessive boost reduces engine efficiency by causing excessive back pressure on the exhaust side and will hurt power. The compression of the added air is not the issue. Compression of air is an effective spring and the energy of compression is recovered when the piston goes back down on the power stroke. 15psi with appropriate fueling will result in more power than 20 psi with the same fuel.
What about if you are using a turbo that can support 20+ efficiently?
Most of the time, more boost at the same fueling is due to too much heat. I understand what you are saying, Jeremy. Most of the time you want to maximize boost but once you are outside of the turbo's efficiency, you are just making hot air. For the vnt-15, it's efficiency drops drastically over 18 psi.
Right, as long as you are in the turbo's efficiency, maximum fuel is what brings maximum power.
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What about the ECO engine? My regular TD has the aneroid enrichment but the ECO doesn't. In theory, the ECO has an excess of fuel and the turbo matches it creating a neutral fuel/ air mix. I don't know what the ECO's boost limit is. My blow off ran at 12 psi until I blocked it off and the waste gate cracks @ 15. If mine is set properly then the ECO should have a lot less boost or there is indeed an excess of air. I can't imagine that there's a lot of valve overlap but the fact that EGT's go down when you hit the boost indicates that air is getting by the exh valve and diluting the exh gasses. The spring argument makes sense. I found a chart somewhere and our 23:1 engines @10 psi = 38:1 effective compression. It takes a lot of energy to do that and I can see a drop in power possible without the additional fuel to go bang. I've heard of some Cummings running 70-90 lbs boost with compound turbos but they must have fire hoses for fuel lines.
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The only point I was trying to get across was that boost is directly relative to fuel burnt. You cannot have high boost without additional fueling. It does not work that way. Unless there is more energy going out the tail-pipe to spin the turbo up then there is no extra boost.
70-90psi!? HOLY COW.
I have never really fully grasped the people going to 22+ psi when it is completely counter-intuitive. You are wasting power to compress the air.. it is pointless. When I get the inter cooler setup on the M-TDI it is going to run a cool 15-18psi.
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This is very true, with my compound setup It pulls hard until about 15 psi and about 2200-2500 rpm, soon after I begin to run out of fuel.
With both wastegates operating at thier lowest boost setting it will still make 22-24psi, but there is clearly no need for that extra 5-10psi.
On the other hand that extra boost does still help keep the EGT's down at higher rpm's..but really serves no other purpose untill it is fed with more fuel..... hopefully soon to come.
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The eTDIs with wastegated turbos had the wastegate controlled by computer. They limited the boost under all conditions in order to accurately match fuel to air to maximize efficiency. Additional boost for any given fueling always reduces efficiency even if you are within the turbos efficiency range (they are never 100% efficient). The mechanically controlled engines come close to that with the aneroid functioning properly, but still fall short.
The ECOdiesel engines were produced to reduce emissions and all the ways they are different from the "true" TD engines hurts engine efficiency.
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8v
Heat spools a turbo, not nessesarily fuel. If you retard the timing and DO NOT change fuel it will reach higher boost, because the later injected fuel isn't burnt completely in the combustion area. It is still burning good in the exhaust port and then spinning the turbo eventhough no more fuel is being injected. So with the timing unchanged if you add more fuel you can add more boost. BUT it is load dependant as well. If you have no load it is harder to make boost. Ex: rev car in nuetral, then rev car in 1st gear, then in 4th gear, the more load the more "potential" for boost.
I had 20+ psi with my k24 because it needed to be cooled. I had less when it wasn't intercooled. For me it was a bunch of trial and error...or mostly error and error and maybe get lucky. I played with that engine constantly to get better results. Right around 22psi intercooled was the best for my EGT situation. More than that it didn't change, less it got worse.
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(http://www.a2resource.com/brochures/1991/vwenvironment/todaytomorrow/source/1.jpg)
(http://www.a2resource.com/brochures/1991/vwenvironment/todaytomorrow/source/2.jpg)
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and i cant drive my car, so you are going to just have to figure it out..
I have it figured out lol. I have given you nothing but proof and logic to determine what happens with boost relative to fuel.
Until you can get your car operational, I cannot physically show you what I am talking about. I just ask for some qualitative answers to prove what you say is all eh?
ok, there.. some answers that werent from me.. sorry dude, but i knew what i was talking about, just needed a couple others to confirm it.. andrew knew exactly what i was talking about, because i believe he was the first one to ever bring it to my attention..
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Sorry. My points were referring to a properly running car. Retarded timing is not optimal, and was never intended.
Andrew, How do the mechanical engines with the LDA manage to do better than the electronically controlled TDI's?
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They don't do better. As I said, "they fall short". They come close because with increases of boost the fuel is increased as well, provided the aneroid is tuned properly, but partial load situations still result in less than optimal fuel to air.
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Additional boost for any given fueling always reduces efficiency even if you are within the turbos efficiency range (they are never 100% efficient). The mechanically controlled engines come close to that with the aneroid functioning properly, but still fall short.
Oh sorry, I read this wrong. It sounds as though you said the mechanical engines come close to 100%, my bad.
So say you have a manual boost controller in place to make sure your waste gate wont pop open until say 20psi. If you adjust the fuel so that 12-15psi WOT with load is all that is obtained. Then you up the fuel so that now you can produce 18-20psi with WOT on load.
Which situation would you have more power at?
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That would depend upon the turbocharger's flow characteristics as compared to the engine's flow characteristics.
And doing what you wrote in your last post is the part of the process of "tuning" your diesel automobile. That in a sense is matching the fueling to the airflow of the engine. <--is what it's all about, and doing it from 500-5500rpm
With any given setup there will be a "magic" boost number that will make the best power, any more or less boost than that number will result in a decrease in power.
Anyways, did you get the TDI working and driving in your car yet? Did you build your own M-TDI pump and how did it turn out?
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Additional boost for any given fueling always reduces efficiency even if you are within the turbos efficiency range (they are never 100% efficient). The mechanically controlled engines come close to that with the aneroid functioning properly, but still fall short.
Oh sorry, I read this wrong. It sounds as though you said the mechanical engines come close to 100%, my bad.
So say you have a manual boost controller in place to make sure your waste gate wont pop open until say 20psi. If you adjust the fuel so that 12-15psi WOT with load is all that is obtained. Then you up the fuel so that now you can produce 18-20psi with WOT on load.
Which situation would you have more power at?
I have played with this and I understand what you're getting at.
Boiled down to the simplest level, you can't have too much mass of air for a given mass of fuel because there wouldn't be enough exhaust gases to spin the compressor to get that mass of air in. If you had a turbo setup that could make high boost with little fuel, it would be inefficient when more fuel is available (except for variable vane turbines, which are designed to function in both situations).
Because of the nature of a diesel engine, fuel doesn't have to be mixed with air in a stoichiometric mixture to get a complete burn of fuel. You can't go rich on the mixture without making smoke, but you can go very lean and still have an efficient engine.
Yes it takes energy to compress a volume of air to a higher ratio, but that energy doesn't just disappear. That larger compressed volume of air is fighting the piston right to top dead centre, then afterwards rebounds like a spring. Whether or not there's fuel injected, that additional volume of air is acting upon the piston during the power stroke.
If "too much" boost for a given volume of fuel is inefficient, why did Volkswagen design an engine to do precisely that, and then throw an "Eco" prefix on it? I think some former gassers need to learn to give up their precious 14.7:1.
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James, as I mentioned previously, the ECO diesel was produced solely to reduce emissions and at significant cost to both performance and efficiency. Additional boost always costs additional back pressure on the exhaust side. If you are over-fueled, then, depending on the size of the turbine, additional boost will give additional power. If appropriately fueled, then increasing boost without increasing fuel at the same time will hurt performance. That effect has nothing to do with gasoline engines.
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Jer, its a matter of flow not pressure. Pressure isn't a good thing.
If you flow more oxygen at 1psi than you do at 100psi you will have a better combustion of the fuel.
talking psi all the time is like talking mileage in "tanks of gas"
who cares how much psi there is. If it's not getting into the cylinders with the appropriate amount of fuel you're either fighting the restriction of the turbo + all the turbulance you're going to be creating in the cylinders or you're flooding it with masses of unburnt fuel.
This dude at a DSM shop where i grew up had a talon and a ... rotary supra...
The supra flowed the fuel & air in and the exhaust out better than the talon did but the talon ran over double the "psi" of the supra.
Needless to say, the supra produced over twice the HP as the talon.
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Ok, but how are you magically increasing boost? I turned down my fuel, and as a result I can't produce as much boost. Sure I could make more power for a given mass of air by increasing the fueling, but it doesn't feel like the added boost affects power either way (waste-gate connected or not) for a given volume of fuel. For the test, my setup is an AAZ with a K14 turbo, stock boost pin, stock everything, with a minor adjustment of fueling, and pump timed to .90mm. With the waste-gate connected, it will generate 9psi boost consistently (enough to put the boost pin on the step). Without, it tops out at about 19psi with my current fueling. I'm only using the butt dyno, but it doesn't feel any different, except it's quieter with the waste-gate disconnected. To quell this argument, we need someone to run a few dyno pulls with consistent fueling and variable manifold pressure.
And Eddy, we're only talking in psi because engines are positive displacement pumps. My engine will flow 1.9L of air for every two revolutions at whatever pressure is in the manifold. Volume is constant at a given speed for any manifold pressure. What we should be talking about is mass. m=pV/RT. Volume is a constant, R is a constant, and temperature falls into a fairly consistent range for our purposes (although it would be more consistent if I had an intercooler), so the only real variable is pressure, which is what we're discussing.
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And Eddy, we're only talking in psi because engines are positive displacement pumps. My engine will flow 1.9L of air for every two revolutions at whatever pressure is in the manifold. Volume is constant at a given speed for any manifold pressure. What we should be talking about is mass. m=pV/RT. Volume is a constant, R is a constant, and temperature falls into a fairly consistent range for our purposes (although it would be more consistent if I had an intercooler), so the only real variable is pressure, which is what we're discussing.
Couldn't agree more. Thanks for that.
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I thought this was common sense.... my bad.
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Ok, but how are you magically increasing boost? I turned down my fuel, and as a result I can't produce as much boost. Sure I could make more power for a given mass of air by increasing the fueling, but it doesn't feel like the added boost affects power either way (waste-gate connected or not) for a given volume of fuel. For the test, my setup is an AAZ with a K14 turbo, stock boost pin, stock everything, with a minor adjustment of fueling, and pump timed to .90mm. With the waste-gate connected, it will generate 9psi boost consistently (enough to put the boost pin on the step). Without, it tops out at about 19psi with my current fueling. I'm only using the butt dyno, but it doesn't feel any different, except it's quieter with the waste-gate disconnected. To quell this argument, we need someone to run a few dyno pulls with consistent fueling and variable manifold pressure.
You can 'magically increase boost' by adjusting the wastegate opening pressure or vane angle of a VNT.
Are you intercooled?
There are dyno apps for smart phones. You could do the testing yourself in a more conclusive manner than the butt dyno. Please report back your findings. If for the same fueling there is no difference in power between 9 psi and 19 psi, then the most appropriate fuel to air is somewhere between the two.
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Anyways, 8v-of-fury, does your M-TDI do the daily drive yet and run as intended or are we keyboard cruising still?
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If the wastegate on my turbo opened (or maybe i just need to adjust the controller RadoTD(Matt) made me) I would run 16-20psi.
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I thought this was common sense.... my bad.
How to only reply when you have something helpful to post, that is common sense. ;)
Sorry for utilizing the forum for what it is there for. :D
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ok.. final nail in coffin..
my turbo makes 25 psi with the LDA hooked up, or un hooked, but it makes WAY more power with the LDA hooked up, at the same 25psi boost..
plain and simple, if you have too much boost for a given fuel, it reduces power and efficiency..
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ok.. final nail in coffin..
my turbo makes 25 psi with the LDA hooked up, or un hooked, but it makes WAY more power with the LDA hooked up, at the same 25psi boost..
plain and simple, if you have too much boost for a given fuel, it reduces power and efficiency..
That's not a nail in the coffin, despite bringing this back from the dead. The LDA regulates fuel, not airflow. What you're saying is that with more fuel for a given boost, you make more power. That's already a given here. What you need to do is disable the LDA and see if there's any significant change in power by adjusting manifold pressure.
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ok.. final nail in coffin..
my turbo makes 25 psi with the LDA hooked up, or un hooked, but it makes WAY more power with the LDA hooked up, at the same 25psi boost..
plain and simple, if you have too much boost for a given fuel, it reduces power and efficiency..
That's not a nail in the coffin, despite bringing this back from the dead. The LDA regulates fuel, not airflow. What you're saying is that with more fuel for a given boost, you make more power. That's already a given here. What you need to do is disable the LDA and see if there's any significant change in power by adjusting manifold pressure.
if the LDA is un-hooked, how is it NOT disabled? im completely aware of the functions of the LDA.. it regulates fuel. the wastegate regulates air, and if neither are hooked up, i can still make 25 psi boost..
were talking about keeping the same quantity of boost, and changing fueling..
im saying that it IS possible to make HIGH boost numbers, and still have marginal fueling..
god, im almost sorry i started this thread..
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So if you can make 25psi with everything unhooked?
How do you manage this?
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So if you can make 25psi with everything unhooked?
How do you manage this?
how the hell should i know? my boost gauge doesnt lie tho.. pressure reading taken DIRECTLY from the turbo outlet..
the exhaust coming out of the engine is still hot, and it takes heat and pressure to spool a turbo, not fuel..
heat and pressure are present in ANY exhaust stream.. my TD pump is cranked up enough that even with the LDA un hooked, it still smokes..
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heat and pressure are present in ANY exhaust stream.. my TD pump is cranked up enough that even with the LDA un hooked, it still smokes..
Sounds like your car needs some better tuning? How do you have so much exhaust pressure and heat with WAY less on-boost fueling?
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heat and pressure are present in ANY exhaust stream.. my TD pump is cranked up enough that even with the LDA un hooked, it still smokes..
Sounds like your car needs some better tuning? How do you have so much exhaust pressure and heat with WAY less on-boost fueling?
i have a CRANKED UP PUMP.. it pours coals with or without the LDA hooked up.
the collar on the fuel screw, its gone, and the fuel screw is threaded in like 3 full turns past the collar..
and like libby mentioned.. the MAGIC way to increase boost without fueling, is to adjust the wastegate.. durr..
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I unno man.
Why are you running that much fuel? To smoke that bad on boost aswell ? why?
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...the exhaust coming out of the engine is still hot, and it takes heat and pressure to spool a turbo, not fuel..
With out fuel, you wouldn't have heat or pressure. Heat is not needed to spin a turbo, it does help though.
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Ok, so I was playing again today. I disconnected my LDA, and set my fuel screw so it could smoke off boost, but not on. Kept my waste-gate disabled, and did a 60-90km/h pull in 4th gear up a bit of a hill. Set the wastegate to open at the stock 9psi, then did another 60-90 pull up the same stretch of road.
No LDA, no wastegate 5.9 seconds maxed out around 24 psi boost (hard to tell exactly because I was paying more attention to the speedometer and the road).
No LDA, waste-gated 6.0 seconds maxed out at 9 psi.
With LDA, no waste gate, I backed off the throttle when the needle headed towards 30psi.
That doesn't actually mean that 24psi is good for that fueling, just that the most efficient would be closer to 24 than 9. I would conclude that I have a well matched turbo for my setup, and have a hard time attaining too much boost for a given fuel, but if I could reach too much boost for this fueling, it would be a bad thing. If I turn the fuel down, 24psi would be too much, but I likely wouldn't be able to make that much with my setup.
Oh, and you shouldn't take the boost pressure from the turbo outlet, only the wastegate control. The pressure you should measure is the plenum pressure. Temperature drop from the intercooler and restrictions in intake stream will affect your readings otherwise.
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Oh, and you shouldn't take the boost pressure from the turbo outlet, only the wastegate control. The pressure you should measure is the plenum pressure. Temperature drop from the intercooler and restrictions in intake stream will affect your readings otherwise.
Nice test. So you found that with fueling unchanged you had more power at a higher boost level. However if the turbo is stock on the AAZ, 23psi is way too much for it :O. I think the gt15 is really only good to 18 max tops. If you were to set the waste gate to 18psi, you would probably see even better performance at this fueling than at 23+.
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Ok, so I was playing again today. I disconnected my LDA, and set my fuel screw so it could smoke off boost, but not on. Kept my waste-gate disabled, and did a 60-90km/h pull in 4th gear up a bit of a hill. Set the wastegate to open at the stock 9psi, then did another 60-90 pull up the same stretch of road.
No LDA, no wastegate 5.9 seconds maxed out around 24 psi boost (hard to tell exactly because I was paying more attention to the speedometer and the road).
No LDA, waste-gated 6.0 seconds maxed out at 9 psi.
With LDA, no waste gate, I backed off the throttle when the needle headed towards 30psi.
That doesn't actually mean that 24psi is good for that fueling, just that the most efficient would be closer to 24 than 9. I would conclude that I have a well matched turbo for my setup, and have a hard time attaining too much boost for a given fuel, but if I could reach too much boost for this fueling, it would be a bad thing. If I turn the fuel down, 24psi would be too much, but I likely wouldn't be able to make that much with my setup.
Oh, and you shouldn't take the boost pressure from the turbo outlet, only the wastegate control. The pressure you should measure is the plenum pressure. Temperature drop from the intercooler and restrictions in intake stream will affect your readings otherwise.
when the intake plenum, and turbo inlet are 6" apart, i dont see it being a BIG issue..
im running sans intercooler right now..
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I read most of what was going on in this thread but not everything in detail.
One thing to consider is the fact that the turbo on a 4bt does not have a wastegate or vanes (at least on the rotary pump engines), the engineers at Cummins did this on purpose. They sized the turbo to the engine. This allows the the boost levels to be driven by engine RPM and fueling. This also allows for optimal AFRs whenever possible (although, being mechanically driven there are times at intermediate load levels the AFRs are not so optimal). So in this case if we look at boost relative to fueling, one can say that boost is at least partially driven by fueling levels (you also must account for a properly sized turbo).
Also, belchfire, mentioned Cummins running 70-90 psi. That is not the upper limit on boost levels, competition tractor pullers using the International DT466 or the alike are ranging anywhere from 100 to 300 psi. (quoting this from this article: http://www.enginebuildermag.com/Article/2192/tractor_pulling_its_not_your_granddads_john_deere_anymore.aspx (http://www.enginebuildermag.com/Article/2192/tractor_pulling_its_not_your_granddads_john_deere_anymore.aspx))
And you may say that those are excessive and they could make more power with lower numbers. But one thing you have to take into consideration is that fact that these engines are tuned extensively. When the average build cost for these engines are $50,000, there is no guessing on stuff like boost levels and fueling.
So in the case above high levels of boost and fueling can make high power numbers.
Also there is one thing to consider about fueling and that is the concept of over fueling. Over fueling to a point where the amount of excess fuel being injected into the a cylinder, cools the combustion process can be useful. Excessive over fueling can lower the temperature of the cycle because the unburnt fuel is able to carry heat out of the cylinder much faster than air alone. This allows for increased boost levels and increased power values from a given engine.
I'm not trying to make a point here, I am merely adding information to the thread.
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if too much fuel gives high egt how can we over fuel to cool it down?
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if too much fuel gives high egt how can we over fuel to cool it down?
I am no expert on this but I would assume a set of extrudehoned injectors would be in order; also, the addition of a a "P-Pump" or larger head on a rotary pump would be needed.
You have to understand that the concept of excessive over fueling should only be used in "race" applications. By no means would a vehicle with the amount of fueling needed to accomplish this concept be streetable.
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dh13's reference artical sheds some interesting light on what is possible. Looks like water injection is probably the best way to drop EGT's but not all that practiable for street use. I've run vehicles on the street with all but full race engines in them and it's no fun in stop & go traffic. While there's no such thing as too much power, driveability has to be considered. Always good to keep in mind the intended purpose of your machine so that driving pleasure doesn't turn into a chore.
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dh13's reference artical sheds some interesting light on what is possible. Looks like water injection is probably the best way to drop EGT's but not all that practiable for street use. I've run vehicles on the street with all but full race engines in them and it's no fun in stop & go traffic. While there's no such thing as too much power, driveability has to be considered. Always good to keep in mind the intended purpose of your machine so that driving pleasure doesn't turn into a chore.
I guess the water/meth injection slipped my mind. Mainly because it has been cover so much and has been around for a long time. It was used during WWII in air crafts.
I like your thoughts on driveability and purpose. I feel sometimes people do not understand these concepts.
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When I was a kid every day was race day. A few years and a lot of tickets later I learned that it was every other day.
The water/ meth injection was on gas engines to control detonation. I'm pretty sure that for diesels it's about EGT reduction and charge densification. I would imagine that it's done after the turbo as before would erode the impeller something fierce.
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When I was a kid every day was race day. A few years and a lot of tickets later I learned that it was every other day.
The water/ meth injection was on gas engines to control detonation. I'm pretty sure that for diesels it's about EGT reduction and charge densification. I would imagine that it's done after the turbo as before would erode the impeller something fierce.
nope.. they shoot it pre-turbo on the tractor pullers to keep the compressor from melting.. believe it or not, it DOES NOT cause any erosion of the compressor wheel.. idk about long term wear tho.. after 200k miles of water injection, it could cause a LITTLE bit of wear on the compressor..
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When I was a kid every day was race day. A few years and a lot of tickets later I learned that it was every other day.
The water/ meth injection was on gas engines to control detonation. I'm pretty sure that for diesels it's about EGT reduction and charge densification. I would imagine that it's done after the turbo as before would erode the impeller something fierce.
nope.. they shoot it pre-turbine on the tractor pullers to keep the compressor from melting.. believe it or not, it DOES NOT cause any erosion of the compressor wheel.. idk about long term wear tho.. after 200k miles of water injection, it could cause a LITTLE bit of wear on the compressor..
According to SAAB, this is not the case. Even particles of water as small at 10 micron will erode the compressor wheel. Of all the water/meth systems that I have seen, never have I seen it injected before the compressor wheel on road applications.
You are correct in the fact that tractor pullers do it. Although, for two different reasons. The first is to cool the air going into the turbo. Second, to actually increase the efficiency of the turbo. It acts as a seal between the compressor wheel and the housing, increasing the amount of air the turbo can actually pull.
Also injecting water/meth before the compressor will do little to nothing to keep the "turbine" from melting. The compressor is the cold side of the turbo, the turbine is the hot side of the turbo. I would think that lowering EGTs would be the only way to keep the turbine from melting. I am not sure there would be much heat transfer from the turbine to the compressor or vise a versa. I am talking the wheels themselves. I know heat transfers quite a bit from the turbine housing to the compressor housing and what not.
Just some food for thought. Adding to this already overly complex thread. Sorry I had to with it being finals week and all...
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What a dummy. Of course the exhaust is on the other side of the compressor. What was I thinking? OK how about this. The water cools the combustion as it's being converted to steam. The old latent heat of vaporization thing. That would surely drop EGT's. Inlet injection probably does do some erosion but then we get into race v/s driver application. I've seen a lot of ill advised ideas done for racing but the only thing is winning and it doesn't matter if the engine is a smoldering pile of metal at the end.