Basic questions about boosting NA engines.
Basic questions about boosting NA engines.
1. In a boosted NA gasser timing is set as close to 0 as possible, or there abouts. My understanding of diesels is that you want advance - in fact, factory boosted engines run a lot of advance. Please explain why diesels are not set closer to 0.
2. If you add boost then you have to add fuel. Of course the governor will add fuel within limits in response to more airflow. Correct?
3. What's the best way to monitor air fuel ratio as you add boost? I can see that trial and error could work: Twist the fuel screw, black smoke, add boost smoke disappears, run it, check egts and so on. What about an O2 monitor and a five wire or lambda O2 sensor? Pretty simple to add down stream and get it right. Anyone done this?
I'm open for training and correction.
DieselSchlepper
01-30-2011, 02:46 PM #1My boosted studies were mainly in gas. Now that I found out diesel is far better I'm wondering about a thing or two - gaps in my thinking.
1. In a boosted NA gasser timing is set as close to 0 as possible, or there abouts. My understanding of diesels is that you want advance - in fact, factory boosted engines run a lot of advance. Please explain why diesels are not set closer to 0.
2. If you add boost then you have to add fuel. Of course the governor will add fuel within limits in response to more airflow. Correct?
3. What's the best way to monitor air fuel ratio as you add boost? I can see that trial and error could work: Twist the fuel screw, black smoke, add boost smoke disappears, run it, check egts and so on. What about an O2 monitor and a five wire or lambda O2 sensor? Pretty simple to add down stream and get it right. Anyone done this?
I'm open for training and correction.
Fuel will not be automatically added- you will have to adjust the injector pump for more. There is no airflow metering on a diesel injector pump.
Without an ALDA (boost aneroid) to limit boost before the turbo spools up, you *will* get black smoke from the N/A injector pump as the turbo spools, unless you limit it by giving less throttle.
The reason timing is set low on a gas engine under boost is to avoid knocking, which cannot happen on a diesel because there's no fuel to ignite until after it's injected. A turbo diesel generally runs roughly the same advance as a non-turbo diesel.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
Just adjust the injector pump for as much fuel as possible without excess black smoke- or adjust it for as much fuel as possible period, and turn the boost up until the smoke goes away at full throttle. Air fuel ratio is not critical on a diesel and you don't need to monitor it with an O2 sensor or anything.
Fuel will not be automatically added- you will have to adjust the injector pump for more. There is no airflow metering on a diesel injector pump.
Without an ALDA (boost aneroid) to limit boost before the turbo spools up, you *will* get black smoke from the N/A injector pump as the turbo spools, unless you limit it by giving less throttle.
The reason timing is set low on a gas engine under boost is to avoid knocking, which cannot happen on a diesel because there's no fuel to ignite until after it's injected. A turbo diesel generally runs roughly the same advance as a non-turbo diesel.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
(01-30-2011, 02:46 PM)DieselSchlepper Please explain why diesels are not set closer to 0.Two reasons.
1- diesel burns slow compared to g@soline.
2- the prechamber design adds significant delay to the flame front reaching the piston crown.
Quote:Of course the governor will add fuel within limits in response to more airflow.No. More air will add 0hp unless you adjust the governor to match.
Mechanical injection pumps don't care one bit about airflow, all they know is throttle position, RPM and boost pressure. Increasing manifold pressure above stock specs will not increase fuel flow beyond the stock governor settings.
Quote:3. What's the best way to monitor air fuel ratio as you add boost?Your rear-view mirror. Diesels run very lean 99.9% of the time. Its only at low boost and maximum throttle that the air-fuel ratio matters, and that is very easy to determine simply by visible smoke out the exhaust. The less smoke the better, though a slight haze at WOT is best for power.
Quote:What about an O2 monitor and a five wire or lambda O2 sensor?Complete waste of money.
ForcedInduction
01-30-2011, 11:06 PM
#4
(01-30-2011, 02:46 PM)DieselSchlepper Please explain why diesels are not set closer to 0.Two reasons.
1- diesel burns slow compared to g@soline.
2- the prechamber design adds significant delay to the flame front reaching the piston crown.
Quote:Of course the governor will add fuel within limits in response to more airflow.No. More air will add 0hp unless you adjust the governor to match.
Mechanical injection pumps don't care one bit about airflow, all they know is throttle position, RPM and boost pressure. Increasing manifold pressure above stock specs will not increase fuel flow beyond the stock governor settings.
Quote:3. What's the best way to monitor air fuel ratio as you add boost?Your rear-view mirror. Diesels run very lean 99.9% of the time. Its only at low boost and maximum throttle that the air-fuel ratio matters, and that is very easy to determine simply by visible smoke out the exhaust. The less smoke the better, though a slight haze at WOT is best for power.
Quote:What about an O2 monitor and a five wire or lambda O2 sensor?Complete waste of money.
That is incorrect and you know it, increased air density will obviously improve performance even before the addition of more fuel (not to say more fuel is not a good idea). Just like increasing compression ratio, increasing manifold pressure has the same effect on cylinder pressure and gives you greater efficiency from the same amount of fuel. Stop being arguementative just to be arguementative. As a side note i agree with everything else that was said.
"No. More air will add 0hp unless you adjust the governor to match"
That is incorrect and you know it, increased air density will obviously improve performance even before the addition of more fuel (not to say more fuel is not a good idea). Just like increasing compression ratio, increasing manifold pressure has the same effect on cylinder pressure and gives you greater efficiency from the same amount of fuel. Stop being arguementative just to be arguementative. As a side note i agree with everything else that was said.
I fail to see how pumping more air, with the same amount of fully combusted fuel, will gain anything.
Correct me if I'm wrong, but that's how I see it.
1990 Power Ram 50 V6 SOHC 24V 6g72
I can be wrong, don't take everything I say as verbatim, please fact-check first.
My posts are my personal opinions and thoughts, unless otherwise noted.
Er, when you have an air density of X in a diesel, that's already running lean as can be, using all the air it needs, and you increase the air density to X+1, you don't get anything but more air being pumped through.
I fail to see how pumping more air, with the same amount of fully combusted fuel, will gain anything.
Correct me if I'm wrong, but that's how I see it.
1990 Power Ram 50 V6 SOHC 24V 6g72
I can be wrong, don't take everything I say as verbatim, please fact-check first.
My posts are my personal opinions and thoughts, unless otherwise noted.
(01-30-2011, 11:32 PM)josha37 That is incorrect and you know itThat is false information.
Quote:increased air density will obviously improve performance even before the addition of more fuelIncorrect. Boost without added fuel will decrease performance through added compression loss to blowby (less rebound), exponentially higher exhaust pressure and compressor pumping losses (heat).
Quote:Just like increasing compression ratio, increasing manifold pressure has the same effect on cylinder pressure and gives you greater efficiency from the same amount of fuel.That is false information.
Increasing the compression ratio increases the expansion ratio which means more combustion energy is utilized.
Quote: Stop being arguementative just to be arguementative.First, at least try to spell "argumentative" correctly. Second, try to understand what you're talking about. Basic physics and thermodynamics isn't a difficult field.
(01-30-2011, 11:42 PM)300D50 Correct me if I'm wrongYou're not.
ForcedInduction
01-30-2011, 11:44 PM
#7
(01-30-2011, 11:32 PM)josha37 That is incorrect and you know itThat is false information.
Quote:increased air density will obviously improve performance even before the addition of more fuelIncorrect. Boost without added fuel will decrease performance through added compression loss to blowby (less rebound), exponentially higher exhaust pressure and compressor pumping losses (heat).
Quote:Just like increasing compression ratio, increasing manifold pressure has the same effect on cylinder pressure and gives you greater efficiency from the same amount of fuel.That is false information.
Increasing the compression ratio increases the expansion ratio which means more combustion energy is utilized.
Quote: Stop being arguementative just to be arguementative.First, at least try to spell "argumentative" correctly. Second, try to understand what you're talking about. Basic physics and thermodynamics isn't a difficult field.
(01-30-2011, 11:42 PM)300D50 Correct me if I'm wrongYou're not.
I've actually tested this at the drag strip- my 190D ran a noticeably slower time when I raised the boost by 5psi without adjusting the injector pump.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
I'm with forced on this one- if you're already lean enough that you're not smoking, adding additional boost will slightly decrease horsepower rather than increase it.
I've actually tested this at the drag strip- my 190D ran a noticeably slower time when I raised the boost by 5psi without adjusting the injector pump.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
The same effect can be had by increasing the density of the air you are compressing.
"Incorrect. Boost will decrease performance through added compression loss to blowby (less rebound), exponentially higher exhaust pressure and compressor pumping losses (heat)."
If you are losing performance to blow-by you have bigger problems, back-pressure is only negative if nothing good is coming from it, diesel's thrive on heat and without adding tons of extra fuel we are not talking about manifold pressures high enough to have much of any effect of intake air temps.
Just like engines making less power at mountain peak altitudes than sea level, artifically altering manifold pressure will have similar effects on the way the engine behaves.
casio i agree with what you are saying but if you backed your pressure off to zero and ran then bumped it up to 5 and ran again your car would be faster... When i initially installed the turbo on my 240d i made no changes to fueling and noted a rather significant increase in performance not only with top end power but steady interstate cruising as well.
"Increasing compression increases the expansion ratio which means more combustion energy is utilized."
The same effect can be had by increasing the density of the air you are compressing.
"Incorrect. Boost will decrease performance through added compression loss to blowby (less rebound), exponentially higher exhaust pressure and compressor pumping losses (heat)."
If you are losing performance to blow-by you have bigger problems, back-pressure is only negative if nothing good is coming from it, diesel's thrive on heat and without adding tons of extra fuel we are not talking about manifold pressures high enough to have much of any effect of intake air temps.
Just like engines making less power at mountain peak altitudes than sea level, artifically altering manifold pressure will have similar effects on the way the engine behaves.
casio i agree with what you are saying but if you backed your pressure off to zero and ran then bumped it up to 5 and ran again your car would be faster... When i initially installed the turbo on my 240d i made no changes to fueling and noted a rather significant increase in performance not only with top end power but steady interstate cruising as well.
(01-31-2011, 12:00 AM)josha37 "Increasing compression increases the expansion ratio which means more combustion energy is utilized."
The same effect can be had by increasing the density of the air you are compressing.
You have many variables at play at once here- the extra power it takes (extra exhaust back-pressure) to make higher boost more than compensates for any efficiency increase from the higher density air at lean fuel mixtures.
(01-31-2011, 12:00 AM)josha37 Just like engines making less power at mountain peak altitudes than sea level, artifically altering manifold pressure will have similar effects on the way the engine behaves.
No, engines make less air at altitude because they are tuned to be able to provide sufficient fuel at sea level, and either lean out via altitude compensation, or waste fuel as smoke at high altitude. If your injector pump lacked altitude compensation, and were tuned to not smoke at high altitude, you would experience no horsepower increase going to low altitude.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
(01-31-2011, 12:00 AM)josha37 "Increasing compression increases the expansion ratio which means more combustion energy is utilized."
The same effect can be had by increasing the density of the air you are compressing.
You have many variables at play at once here- the extra power it takes (extra exhaust back-pressure) to make higher boost more than compensates for any efficiency increase from the higher density air at lean fuel mixtures.
(01-31-2011, 12:00 AM)josha37 Just like engines making less power at mountain peak altitudes than sea level, artifically altering manifold pressure will have similar effects on the way the engine behaves.
No, engines make less air at altitude because they are tuned to be able to provide sufficient fuel at sea level, and either lean out via altitude compensation, or waste fuel as smoke at high altitude. If your injector pump lacked altitude compensation, and were tuned to not smoke at high altitude, you would experience no horsepower increase going to low altitude.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
The ADA on a NA pump takes care of that, and on a turbo car the altitude change is all but moot except at idle with no boost, and even then the ALDA will compensate for it.
1990 Power Ram 50 V6 SOHC 24V 6g72
I can be wrong, don't take everything I say as verbatim, please fact-check first.
My posts are my personal opinions and thoughts, unless otherwise noted.
The high altitude vs low altitude has to do with the engine running too lean at high altitude due to the lower air density not supporting full combustion of the injected fuel quantity.
The ADA on a NA pump takes care of that, and on a turbo car the altitude change is all but moot except at idle with no boost, and even then the ALDA will compensate for it.
1990 Power Ram 50 V6 SOHC 24V 6g72
I can be wrong, don't take everything I say as verbatim, please fact-check first.
My posts are my personal opinions and thoughts, unless otherwise noted.
(01-31-2011, 12:00 AM)josha37 When i initially installed the turbo on my 240d i made no changes to fueling and noted a rather significant increase in performance not only with top end power but steady interstate cruising as well.
Probably because your engine was already getting more fuel than it could burn. N/A diesels generally are tuned much richer, and produce a lot more smoke at full throttle than turbo diesels to squeeze every last bit of power from them.
You wouldn't have noticed any power increase adding the turbo *if* your engine had already been tuned for zero smoke at full throttle without the turbo.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
(01-31-2011, 12:00 AM)josha37 When i initially installed the turbo on my 240d i made no changes to fueling and noted a rather significant increase in performance not only with top end power but steady interstate cruising as well.
Probably because your engine was already getting more fuel than it could burn. N/A diesels generally are tuned much richer, and produce a lot more smoke at full throttle than turbo diesels to squeeze every last bit of power from them.
You wouldn't have noticed any power increase adding the turbo *if* your engine had already been tuned for zero smoke at full throttle without the turbo.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
(01-31-2011, 12:00 AM)josha37 The same effect can be had by increasing the density of the air you are compressing.Only when increasing the density doesn't consume power to do. The turbo does, significantly.
Quote:If you are losing performance to blow-by you have bigger problemsFYI; ALL engines have blowby.
Quote:back-pressure is only negative if nothing good is coming from itFor which boost is one of them.
Quote:diesel's thrive on heatThat is false information. Heat is only need for initial ignition, anything further is wasted energy.
Quote:and without adding tons of extra fuel we are not talking about manifold pressures high enough to have much of any effect of intake air temps.Incorrect. Even a bone-stock non-turbo engine can make upwards of 13psi, my 300D was able to do exactly that when the non-turbo M-pump was installed. What limits boost on a wastegated turbo is the wastegate, not fuel.
Quote:Just like engines making less power at mountain peak altitudes than sea levelIncorrect. They make less power because there is less air available and the turbo must pump to a higher pressure ratio to achieve the same airflow.
Quote:casio i agree with what you are saying but if you backed your pressure off to zero and ran then bumped it up to 5 and ran again your car would be faster.That is not even remotely close to what he said.
Quote:When i initially installed the turbo on my 240d i made no changes to fueling and noted a rather significant increase in performance not only with top end power but steady interstate cruising as well.That is more likely to the change in noise. Thats what makes people perceive an increase in performance with a "cold air intake".
ForcedInduction
01-31-2011, 12:12 AM
#13
(01-31-2011, 12:00 AM)josha37 The same effect can be had by increasing the density of the air you are compressing.Only when increasing the density doesn't consume power to do. The turbo does, significantly.
Quote:If you are losing performance to blow-by you have bigger problemsFYI; ALL engines have blowby.
Quote:back-pressure is only negative if nothing good is coming from itFor which boost is one of them.
Quote:diesel's thrive on heatThat is false information. Heat is only need for initial ignition, anything further is wasted energy.
Quote:and without adding tons of extra fuel we are not talking about manifold pressures high enough to have much of any effect of intake air temps.Incorrect. Even a bone-stock non-turbo engine can make upwards of 13psi, my 300D was able to do exactly that when the non-turbo M-pump was installed. What limits boost on a wastegated turbo is the wastegate, not fuel.
Quote:Just like engines making less power at mountain peak altitudes than sea levelIncorrect. They make less power because there is less air available and the turbo must pump to a higher pressure ratio to achieve the same airflow.
Quote:casio i agree with what you are saying but if you backed your pressure off to zero and ran then bumped it up to 5 and ran again your car would be faster.That is not even remotely close to what he said.
Quote:When i initially installed the turbo on my 240d i made no changes to fueling and noted a rather significant increase in performance not only with top end power but steady interstate cruising as well.That is more likely to the change in noise. Thats what makes people perceive an increase in performance with a "cold air intake".
"That is more likely to the change in noise. Thats what makes people perceive an increase in performance with a "cold air intake". "
Yea a top speed of 75 ish to being able to push it past that with little effort, yea must have been noise
"Probably because your engine was already getting more fuel than it could burn. N/A diesels generally are tuned much richer, and produce a lot more smoke at full throttle than turbo diesels to squeeze every last bit of power from them."
It did not smoke even a little pre- turbo, the smoke all started after pump modification began. I have always suspected that it was under fueling initially simply because it was hardly capable of maintaning interstate speeds on flat ground. But i never verified that.
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I have a mountain 2 hours from here and i live well about 5 feet off sea level. Your trying to tell me that if i took a na engine ran it here then went up there that i would experience no loss of performance if my fueling rate was not changed? That is clearly incorrect for i have been up there several times with my carb powered truck and there is a very clear change in performance from here to there and it is VERY negative at those altititudes. Same thing with my cav and blazer both fuel injected(auto correction through o2 sensors) and huge losses of performance with altitiude change can be noted. Air density is increadibly important to power output no mater how you look at it.
"That is more likely to the change in noise. Thats what makes people perceive an increase in performance with a "cold air intake". "
Yea a top speed of 75 ish to being able to push it past that with little effort, yea must have been noise
"Probably because your engine was already getting more fuel than it could burn. N/A diesels generally are tuned much richer, and produce a lot more smoke at full throttle than turbo diesels to squeeze every last bit of power from them."
It did not smoke even a little pre- turbo, the smoke all started after pump modification began. I have always suspected that it was under fueling initially simply because it was hardly capable of maintaning interstate speeds on flat ground. But i never verified that.
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(01-31-2011, 12:12 AM)ForcedInduction That is more likely to the change in noise. Thats what makes people perceive an increase in performance with a "cold air intake".
I've yet to seen an N/A MB diesel that wasn't tuned to produce considerable smoke at full throttle. I'm sure adding a turbo without adjusting anything would convert this wasted fuel to power.
(01-31-2011, 12:15 AM)josha37 I have a mountain 2 hours from here and i live well about 5 feet off sea level. Your trying to tell me that if i took a na engine ran it here then went up there that i would experience no loss of performance if my fueling rate was not changed?
No, you didn't understand what I said. If you took an NA diesel (not gasoline) without altitude compensation to high altitude, and proceeded to lean out the injector pump until it produced no smoke, you would then have an engine that makes roughly the same power at both high and low altitude. Normally a diesel without altitude compensation is tuned properly for sea level, and simply produces more smoke (and less power) at higher altitudes.
This absolutely does not apply to gasoline engines, which need to maintain a correct A/F ratio, and can't simply experience a reduction in power by running overly lean.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
(01-31-2011, 12:12 AM)ForcedInduction That is more likely to the change in noise. Thats what makes people perceive an increase in performance with a "cold air intake".
I've yet to seen an N/A MB diesel that wasn't tuned to produce considerable smoke at full throttle. I'm sure adding a turbo without adjusting anything would convert this wasted fuel to power.
(01-31-2011, 12:15 AM)josha37 I have a mountain 2 hours from here and i live well about 5 feet off sea level. Your trying to tell me that if i took a na engine ran it here then went up there that i would experience no loss of performance if my fueling rate was not changed?
No, you didn't understand what I said. If you took an NA diesel (not gasoline) without altitude compensation to high altitude, and proceeded to lean out the injector pump until it produced no smoke, you would then have an engine that makes roughly the same power at both high and low altitude. Normally a diesel without altitude compensation is tuned properly for sea level, and simply produces more smoke (and less power) at higher altitudes.
This absolutely does not apply to gasoline engines, which need to maintain a correct A/F ratio, and can't simply experience a reduction in power by running overly lean.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
(01-31-2011, 12:21 AM)josha37 but that is not to say that there is not the possiability of efficiency improvement.
There is a thermodynamic efficiency improvement from the higher cylinder pressure and temperature- but it's minimal and more then compensated for by the extra power required to drive the turbocharger to produce more boost.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
(01-31-2011, 12:21 AM)josha37 but that is not to say that there is not the possiability of efficiency improvement.
There is a thermodynamic efficiency improvement from the higher cylinder pressure and temperature- but it's minimal and more then compensated for by the extra power required to drive the turbocharger to produce more boost.
-Tyler
1984 Volvo 760GLE Turbo Diesel D24T/M46
1986 Isuzu Trooper Turbo Diesel
No mercedes (for now)
"Incorrect. Even a bone-stock non-turbo engine can make upwards of 13psi, my 300D was able to do exactly that when the non-turbo M-pump was installed. What limits boost on a wastegated turbo is the wastegate, not fuel."
Who said anything about wastegated turbos?
And once you have boost.. you can add fuel and this entire arguement is moot.
"Incorrect. Even a bone-stock non-turbo engine can make upwards of 13psi, my 300D was able to do exactly that when the non-turbo M-pump was installed. What limits boost on a wastegated turbo is the wastegate, not fuel."
Who said anything about wastegated turbos?
(01-31-2011, 12:25 AM)josha37 And once you have boost.. you can add fuel and this entire argument is moot.So the entire point of our argumentative posts is.......
Quote:Who said anything about wastegated turbos?Everyone that isn't living in the 1950's.
ForcedInduction
01-31-2011, 01:15 AM
#19
(01-31-2011, 12:25 AM)josha37 And once you have boost.. you can add fuel and this entire argument is moot.So the entire point of our argumentative posts is.......
Quote:Who said anything about wastegated turbos?Everyone that isn't living in the 1950's.
DieselSchlepper
01-31-2011, 08:37 PM #20Thanks for that spirited debate. I got a lot out of that. Really appreciate it
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