Pressure vs. Flow - Let's do this!!!!
02-09-2010, 07:19 PM
#126
how about something simple like low power .
Say your boost is 10psi at 7500rpm and your power is only 250whp . Do you really think that is normal and can be explained through turbo sizing ?
Hell no !!!!! Give me a freakin break .
So you look as mass flow and see it's say 270g/s . Seems about right for 250whp . But why is boost so high and power /MAF so low ?
I don't know about you but I can think of some very good explanations for this -none of which involve the turbo size .....
Say your boost is 10psi at 7500rpm and your power is only 250whp . Do you really think that is normal and can be explained through turbo sizing ?
Hell no !!!!! Give me a freakin break .
So you look as mass flow and see it's say 270g/s . Seems about right for 250whp . But why is boost so high and power /MAF so low ?
I don't know about you but I can think of some very good explanations for this -none of which involve the turbo size .....
How about you just look at flow in the first place and skip why the boost is so low?
Here's a data point:
When AccessPORT customers send me their datalogs, I don't get to see boost.
At all.
The AP doesn't log it.
I have to tune entirely with flow.
Yet, somehow, not only can I do this effectively, but I can tell exactly how much boost they are running, what their boost response "curve" looks like and whether they are "pedaling it" or if there is some other problem in their setup.
Boost is completely useless and can be totally ignored.
02-09-2010, 08:18 PM
#128
Actually, I think the answer to that is "yes".
That is to say, I haven't ever walked away from a problem or failure without either fixing it or determining the issue. (There are, of course, circumstances where the issue causing the failure cannot or will not be addressed by the owner due to difficulty or expense.)
To some degree, this is a downfall of mine, because it leads me to over-extending myself significantly.
That is to say, I haven't ever walked away from a problem or failure without either fixing it or determining the issue. (There are, of course, circumstances where the issue causing the failure cannot or will not be addressed by the owner due to difficulty or expense.)
To some degree, this is a downfall of mine, because it leads me to over-extending myself significantly.
02-09-2010, 08:27 PM
#129
Administrator
i started to go back into the old posts and dig up useful quotes like
and
and
much easier for me (and you guys) than if i typed the stuff out myself.
anyway point is i was going to do more of this but then i realized it's dinner time so i'll end here by saying-
go read the axial flow thread and hymee's Measured Mass Air Flow & Efficiency and a few other threads from 2004 and you'll hopefully find all the useful truthful, educational nuggets that will set you on the correct path. flow is king
I took a more mathematical approach when it came to making power. Read my first post in this thread:
https://www.rx8club.com/showthread.p...=ideal+gas+law
Did you mean by more fuel, more fuel consumption? A/F ratios are critical to optimum performance, especially in forced induction applications. More pressure can lead to more power, but it depends on the method. For example, an equation for power, which I will call W[dot] follows the equation
W[dot]=m[dot]*[(Integrand)pdV]
I wish I had mathtype
.
m[dot] is the mass flow rate
[(Integrand)pdV] is the integral from the initial specific volume to the final specific volume, multiplied by some specified pressure p.
For those who haven't had any experience with calculus, the formula for W[dot] goes to
W[dot]=m[dot]p(v[2]-v[1])
v[1] is the initial specific volume
v[2] is the final specific volume, which are both measured in ft^3/lbm or in SI units, m^3/kg
Note: Mass air flow rates are usually in lbf/min, or in kg/s. It is okay to mix units, as long as you convert between English and SI.
Yes, increasing the pressure will increase the power. Unfortunately, the internal strength is weakened, since the mass flow rate is both pressure and temperature dependent. This will explain a lower modulus in the material.
With ideal intercoolers, the temperature drops, but the pressure is to remain constant. Cooler operating temperatures will lead to more power. Why? Going back to the Ideal Gas Law for the mass balance,
m[dot]=p(AV)/{R[G]T}
you can observe that lowering the temperature will lead to a higher mass flow rate, thus increasing W[dot].
https://www.rx8club.com/showthread.p...=ideal+gas+law
Did you mean by more fuel, more fuel consumption? A/F ratios are critical to optimum performance, especially in forced induction applications. More pressure can lead to more power, but it depends on the method. For example, an equation for power, which I will call W[dot] follows the equation
W[dot]=m[dot]*[(Integrand)pdV]
I wish I had mathtype
.m[dot] is the mass flow rate
[(Integrand)pdV] is the integral from the initial specific volume to the final specific volume, multiplied by some specified pressure p.
For those who haven't had any experience with calculus, the formula for W[dot] goes to
W[dot]=m[dot]p(v[2]-v[1])
v[1] is the initial specific volume
v[2] is the final specific volume, which are both measured in ft^3/lbm or in SI units, m^3/kg
Note: Mass air flow rates are usually in lbf/min, or in kg/s. It is okay to mix units, as long as you convert between English and SI.
Yes, increasing the pressure will increase the power. Unfortunately, the internal strength is weakened, since the mass flow rate is both pressure and temperature dependent. This will explain a lower modulus in the material.
With ideal intercoolers, the temperature drops, but the pressure is to remain constant. Cooler operating temperatures will lead to more power. Why? Going back to the Ideal Gas Law for the mass balance,
m[dot]=p(AV)/{R[G]T}
you can observe that lowering the temperature will lead to a higher mass flow rate, thus increasing W[dot].
and
Yea for Hymee. I hate the term "volumetric efficency". I don't even know what it is.
Do you remember when your professor took a big pyrex bell and hooked a pump through a manometer? You know a u shaped tube with a given amount of mercury in it? When he pumped the air out the pressure would go down. And the opposite.
Did the volume change under the bell???
Of course not, it can't. The bell is the same size so the volume is the same. Now is there more orr less air in there?? yes there is, but this is mass.
So no matter how well or poorly your engine pumps air it alwways pumps the same volume.
Therefore, in order to fuel the engine properly the ECM must know the mass. If that were not the case this would be a lot easier.
I havn't read this whole tread and I;m going to do so right now. I just wanted to put that in since it is one of my pet peeves.
RAP
Do you remember when your professor took a big pyrex bell and hooked a pump through a manometer? You know a u shaped tube with a given amount of mercury in it? When he pumped the air out the pressure would go down. And the opposite.
Did the volume change under the bell???
Of course not, it can't. The bell is the same size so the volume is the same. Now is there more orr less air in there?? yes there is, but this is mass.
So no matter how well or poorly your engine pumps air it alwways pumps the same volume.
Therefore, in order to fuel the engine properly the ECM must know the mass. If that were not the case this would be a lot easier.
I havn't read this whole tread and I;m going to do so right now. I just wanted to put that in since it is one of my pet peeves.
RAP
anyway point is i was going to do more of this but then i realized it's dinner time so i'll end here by saying-
go read the axial flow thread and hymee's Measured Mass Air Flow & Efficiency and a few other threads from 2004 and you'll hopefully find all the useful truthful, educational nuggets that will set you on the correct path. flow is king
02-09-2010, 08:40 PM
#130
Well that's great then.
It behooves me to think that you (and others) totally dissmiss all the points I've raised here - but I guess I always knew I had my back against the wall on this one.
And if you ever do find a dyno that shows numbers way out of proportion to what I suggested they should be (on a renesis with no other issues) do me a favour and post it here .
It behooves me to think that you (and others) totally dissmiss all the points I've raised here - but I guess I always knew I had my back against the wall on this one.
And if you ever do find a dyno that shows numbers way out of proportion to what I suggested they should be (on a renesis with no other issues) do me a favour and post it here .
02-09-2010, 09:12 PM
#131
i do have to admit i have seen pretty accurate hp calculation charts depending on boost level.
how it is all done is beyond me.
here is one site--it speaks about superchargers in particular but boost is boost.
http://www.superchargersonline.com/hp_calculator.asp
it is a rough estimate but it is pretty close.
OD
how it is all done is beyond me.
here is one site--it speaks about superchargers in particular but boost is boost.
http://www.superchargersonline.com/hp_calculator.asp
it is a rough estimate but it is pretty close.
OD
02-09-2010, 11:19 PM
#132
Those calculators just take an existing number and apply a fudge-factored multiplier.
If car "X" makes 200 WHP at atmo, it will make 85% - 95% of the delta P from atmo.
200 HP NA @ 7 PSI of boost = 300 HP (give or take 15 HP).
Anyone with experience can usually guess within a dozen or so HP what the result is gonna be when adding FI to an existing setup.
Its pretty crude.
But try to tune with that information and see what happens.
If car "X" makes 200 WHP at atmo, it will make 85% - 95% of the delta P from atmo.
200 HP NA @ 7 PSI of boost = 300 HP (give or take 15 HP).
Anyone with experience can usually guess within a dozen or so HP what the result is gonna be when adding FI to an existing setup.
Its pretty crude.
But try to tune with that information and see what happens.
02-10-2010, 01:02 AM
#133
Oh, by the way:
https://www.rx8club.com/series-i-tech-garage-22/rotary-math-106294/
I already went through all this math for you over three years ago.
https://www.rx8club.com/series-i-tech-garage-22/rotary-math-106294/
I already went through all this math for you over three years ago.
02-10-2010, 08:49 AM
#134
thanks for posting that link to the earier post concerning the rotary's air flow analysis etc.
I can totally understand that tuning cant be done per boost only. I also admit I havent done much if any real tuning on the modern efi/ecm engine. Give me a carb/recip engine and I am at home.
I can totally understand that tuning cant be done per boost only. I also admit I havent done much if any real tuning on the modern efi/ecm engine. Give me a carb/recip engine and I am at home.
02-10-2010, 09:45 AM
#136
how about something simple like low power .
Say your boost is 10psi at 7500rpm and your power is only 250whp . Do you really think that is normal and can be explained through turbo sizing ?
Hell no !!!!! Give me a freakin break .
http://www.turbobygarrett.com/turbob..._756068__1.htm
It would be normal for some compressors.
BTW my argument on here has never been that boost > flow as a tool . Just that Boost is a valuable tool and you should not ignore it .
Say your boost is 10psi at 7500rpm and your power is only 250whp . Do you really think that is normal and can be explained through turbo sizing ?
Hell no !!!!! Give me a freakin break .
http://www.turbobygarrett.com/turbob..._756068__1.htm
It would be normal for some compressors.
BTW my argument on here has never been that boost > flow as a tool . Just that Boost is a valuable tool and you should not ignore it .
02-10-2010, 01:39 PM
#137
/\ Kane - it is extremely unlikely that that turbo would reach 10psi boost in a renesis at 7500 rpm - physically impossible . Hell - the Greddy can't even do it .
My comments were directed at turbos that we currently use that are at least close to being sized right for the Renesis .
BTW has everyone forgotten how tuning was done (and still is by many ) up until very recently - it's called MAP tuning . How do they do it ? I mean - According to MM boost is absolutely useless information . They must just wave a majic wand or something ......
My comments were directed at turbos that we currently use that are at least close to being sized right for the Renesis .
BTW has everyone forgotten how tuning was done (and still is by many ) up until very recently - it's called MAP tuning . How do they do it ? I mean - According to MM boost is absolutely useless information . They must just wave a majic wand or something ......
Last edited by Brettus; 02-10-2010 at 01:59 PM.
02-10-2010, 02:03 PM
#138
MAF vs MAP Tuning
There are two basic types of EMS’ out there today (excluding the ones that tune by Volumetric Efficiency). There are those that use a Mass Airflow Sensor (MAF) and others that use a Manifold Absolute Pressure Sensor (MAP). Some cars, like an RX8+e-Manage use both a MAF with a piggyback EMS that uses MAP. There are different tuning set-ups depending on what type of EMS the vehicle has.
MAF = example - Cobb AP (in some cases); Maps are often in Load and RPM. This type of EMS measures the mass of air entering the motor by using a heated sensor which reads the amount of airflow being drawn into the motor and converts this reading into a voltage usually in the scale of Volts, or in some cars Hertz. This is called a MAF sensor. This means your vehicle is going to be tuned in Load % or Calculated Load%. The scales on MAF vehicles use some derivative of Load as there is no pressure sensor.
MAF Sensor EMS’ calculate the Load on the motor by taking the RPM and the Mass of Air into the motor to determine the Load %. It does this by determining the total volume of air the motor could breathe at the specified RPM (Engine Displacement * RPM) and dividing that by the Mass of Air the motor is actually breathing. A 3.0 Liter Engine at 2000 RPM is capable of breathing 6000 Liters of Air a minute; but the MAF only measures 3000 Liters of Air, is said to be at 50% load. Tuning a boosted motor with a MAF based tunable EMS, the Load scale is going to exceed 1.00 or exceed 100% (see Power Adders for Dummies Post for more on Load and VE%).
MAP = example - Apexi PFC; Pressure Based Tuning
This type of EMS uses the Pressure of the Intake Manifold combined with the Air Temperature to estimate the Mass of Air into the motor. This is currently the most common type of Tunable EMS. Typically, the Base Map is set up just by Pressure and RPM. There is a separate map for temperature changes as a modifier to the base fuel map. Baseline will be giving you the information to plug into the base map. The scale of a MAP based EMS may also be in Load.
The type of EMS in the vehicle needs to be known in order to set up the Manifold Scale correctly. It will either be in Load (KPa, or Percent), Pressure (PSI) or Voltage (V). Some MAP sensors will convert the reading into a Voltage similar to some MAF sensors, this occurs with some versions of HP Tuners.
Ultimately, these different EMS’ do the same thing; figure the Partial Pressure of Oxygen in the motor to calculate the amount of fuel to inject. While the set-up will be different, the tuning process is the same.
There are two basic types of EMS’ out there today (excluding the ones that tune by Volumetric Efficiency). There are those that use a Mass Airflow Sensor (MAF) and others that use a Manifold Absolute Pressure Sensor (MAP). Some cars, like an RX8+e-Manage use both a MAF with a piggyback EMS that uses MAP. There are different tuning set-ups depending on what type of EMS the vehicle has.
MAF = example - Cobb AP (in some cases); Maps are often in Load and RPM. This type of EMS measures the mass of air entering the motor by using a heated sensor which reads the amount of airflow being drawn into the motor and converts this reading into a voltage usually in the scale of Volts, or in some cars Hertz. This is called a MAF sensor. This means your vehicle is going to be tuned in Load % or Calculated Load%. The scales on MAF vehicles use some derivative of Load as there is no pressure sensor.
MAF Sensor EMS’ calculate the Load on the motor by taking the RPM and the Mass of Air into the motor to determine the Load %. It does this by determining the total volume of air the motor could breathe at the specified RPM (Engine Displacement * RPM) and dividing that by the Mass of Air the motor is actually breathing. A 3.0 Liter Engine at 2000 RPM is capable of breathing 6000 Liters of Air a minute; but the MAF only measures 3000 Liters of Air, is said to be at 50% load. Tuning a boosted motor with a MAF based tunable EMS, the Load scale is going to exceed 1.00 or exceed 100% (see Power Adders for Dummies Post for more on Load and VE%).
MAP = example - Apexi PFC; Pressure Based Tuning
This type of EMS uses the Pressure of the Intake Manifold combined with the Air Temperature to estimate the Mass of Air into the motor. This is currently the most common type of Tunable EMS. Typically, the Base Map is set up just by Pressure and RPM. There is a separate map for temperature changes as a modifier to the base fuel map. Baseline will be giving you the information to plug into the base map. The scale of a MAP based EMS may also be in Load.
The type of EMS in the vehicle needs to be known in order to set up the Manifold Scale correctly. It will either be in Load (KPa, or Percent), Pressure (PSI) or Voltage (V). Some MAP sensors will convert the reading into a Voltage similar to some MAF sensors, this occurs with some versions of HP Tuners.
Ultimately, these different EMS’ do the same thing; figure the Partial Pressure of Oxygen in the motor to calculate the amount of fuel to inject. While the set-up will be different, the tuning process is the same.
Let's say that a 350ci V motor with a single turbo at 10psi, would it flow the same as parallel twins at 10psi? Would they make the same power as a roots SC at 10 PSI? *The answer must be in the form of a question*
02-10-2010, 02:07 PM
#139
We compute the flow by correlating the MAP to temperature.
It's still flow tuning, just really crude by comparison.
You can't just tune with MAP. Even if you are assuming the IAT values and the motor Ve values, you are still doing flow.
Alpha-N is even, technically, flow tuning. You are just assuming nearly everything.
It obviously can be done, but you have to know in advance exactly what the IAT and Ve values are gonna be.
Ugh.
02-10-2010, 02:37 PM
#144
just quoting myself here because you all missed my point .
It was just a attempted humourous dig at MM's assertion that boost is totally useless .
I don't see anybody saying lets just measure temperature change and tune with that and not include boost cuz it's "totally useless" .
It was just a attempted humourous dig at MM's assertion that boost is totally useless .
I don't see anybody saying lets just measure temperature change and tune with that and not include boost cuz it's "totally useless" .
Last edited by Brettus; 02-10-2010 at 02:47 PM.
02-10-2010, 03:37 PM
#145
I don't see the big confusion here. Even in map tuning boost is useless unless coupled with the many other thing to calculate the FLOW. And even then it's pretty much just a number it doesn't really equate to anything.
10 psi of boost on one turbo is totally different than the flow of another turbo pushing 10 psi cause the mass flow/density is different. flow>boost.
I think I'm getting the jist, please if I'm wrong correct me. I'm really trying to grab a hold of this.
10 psi of boost on one turbo is totally different than the flow of another turbo pushing 10 psi cause the mass flow/density is different. flow>boost.
I think I'm getting the jist, please if I'm wrong correct me. I'm really trying to grab a hold of this.
02-10-2010, 03:44 PM
#146
just quoting myself here because you all missed my point .
It was just a attempted humourous dig at MM's assertion that boost is totally useless .
I don't see anybody saying lets just measure temperature change and tune with that and not include boost cuz it's "totally useless" .
It was just a attempted humourous dig at MM's assertion that boost is totally useless .
I don't see anybody saying lets just measure temperature change and tune with that and not include boost cuz it's "totally useless" .
But you could with Flow... that's the point.
I can say I am going to tune with FLOW and that is it...and it will work out just fine.
I think we have run our course - and Jeff is starting to resemble this guy...
