25 *wheel* HP gain from the Miles mod! (dyno sheets included)
10-05-2007, 05:53 PM
#61
Dave, we know it's purpose exactly ...
<center><img src="http://www.teraspeed.com/RS4/rs4%20torque%20curve.jpg"></center><p>"To ensure a sufficient supply of air to the engine at high RPM ..."
Therefore, if it does not open, there is not a sufficient supply of air.
I think we may just have a simple misunderstanding here. When the flap opens, it is unmistakable. You hear it and feel it. There is a punch above 4500 rpm that is unmistakable. This is born out by the factory HP/Torque curve. A little after 4000 rpm, the intake manifold ram flap switches over to the short geometry, and begins the torque boost process. Thereafter, around 5000 rpm the intake "power flap" opens and completes the boost, which peaks at 5500 rpm.
When this happens, there is a mean intake growl, and there is enough of a torque boost that you feel it. And, just like the factory was able to measure it, it is capable of being measured on a chassis dyno. The interesting feature in the dyno plot, when the flap opens, is that the torque from about 4500 rpm to about 6000 rpm is higher than the torque in the 2500 to 4000 rpm range.
When the flap does not open, you don't feel the kick, you don't here the intake growl, and in my case, the dyno showed that torque between 4500 and 6000 rpm was lower than the torque in the 2500 to 4000 rpm range.
There are quite a few dyno plots I've seen where you can see that the manifold runner flap switches over (and if it did not, you would get an ECU fault code), but there is no boost. There are a few dyno plots I've seen where the boost is evident and significant.
In my case, the top end loss in power is correlated to the flap not opening. IMO, I believe that is the root cause of low HP measurements on RS4s that have been placed on the dyno in the US and Europe. However, I cannot say that for certain, since I have no personal knowledge of those cars. It is, however, the best hypothesis that I can come up with, and it is one that is easily tested.
The test is simple. Come up with a way to open the flap, dyno the car, or do a WOT run and log MAF. Then close the flap and do the same. If the flap makes a difference you will see an increase in torque, horsepower and mass air flow when the flap is open. I hypothesize that the difference is about 6%. We can also monitor the intake air temperature to see if any airflow increase is offset by increased temperature.
I've planned to do all of these, but I just have not had the time.
Therefore, if it does not open, there is not a sufficient supply of air.
I think we may just have a simple misunderstanding here. When the flap opens, it is unmistakable. You hear it and feel it. There is a punch above 4500 rpm that is unmistakable. This is born out by the factory HP/Torque curve. A little after 4000 rpm, the intake manifold ram flap switches over to the short geometry, and begins the torque boost process. Thereafter, around 5000 rpm the intake "power flap" opens and completes the boost, which peaks at 5500 rpm.
When this happens, there is a mean intake growl, and there is enough of a torque boost that you feel it. And, just like the factory was able to measure it, it is capable of being measured on a chassis dyno. The interesting feature in the dyno plot, when the flap opens, is that the torque from about 4500 rpm to about 6000 rpm is higher than the torque in the 2500 to 4000 rpm range.
When the flap does not open, you don't feel the kick, you don't here the intake growl, and in my case, the dyno showed that torque between 4500 and 6000 rpm was lower than the torque in the 2500 to 4000 rpm range.
There are quite a few dyno plots I've seen where you can see that the manifold runner flap switches over (and if it did not, you would get an ECU fault code), but there is no boost. There are a few dyno plots I've seen where the boost is evident and significant.
In my case, the top end loss in power is correlated to the flap not opening. IMO, I believe that is the root cause of low HP measurements on RS4s that have been placed on the dyno in the US and Europe. However, I cannot say that for certain, since I have no personal knowledge of those cars. It is, however, the best hypothesis that I can come up with, and it is one that is easily tested.
The test is simple. Come up with a way to open the flap, dyno the car, or do a WOT run and log MAF. Then close the flap and do the same. If the flap makes a difference you will see an increase in torque, horsepower and mass air flow when the flap is open. I hypothesize that the difference is about 6%. We can also monitor the intake air temperature to see if any airflow increase is offset by increased temperature.
I've planned to do all of these, but I just have not had the time.
10-05-2007, 06:03 PM
#62
But there's no indication that this flap is there for that purpose
Are you sure you're not talking about the secondary air injection pump, that moves air from the intake over to the exhaust to light up the cats on cold start? It's purpose is to reduce emissions.
Any air that passes through the MAF sensor is necessarily metered and will be used by the ECU to control mixture. It is, however, possible to restrict the intake causing air starvation and turbulent flow at the MAF, which can cause the engine to go rich.
Any air that passes through the MAF sensor is necessarily metered and will be used by the ECU to control mixture. It is, however, possible to restrict the intake causing air starvation and turbulent flow at the MAF, which can cause the engine to go rich.
10-05-2007, 06:06 PM
#63
If you're driving at 120 mph
Noise is not a problem
Airflow through the secondary radiator is a problem.
It makes sense to open the flap to maximize cooling.
It also makes sense that there is enough positive pressure developed at high speed that there will be an additional flow boost. (I did see this in comparing 3rd gear and 4th gear WOT vag runs, when I logged the mass air flow.)
Airflow through the secondary radiator is a problem.
It makes sense to open the flap to maximize cooling.
It also makes sense that there is enough positive pressure developed at high speed that there will be an additional flow boost. (I did see this in comparing 3rd gear and 4th gear WOT vag runs, when I logged the mass air flow.)
10-05-2007, 06:13 PM
#64
Looking at the plots
If you look at the way MAF jumps around on the Hyperflow intake, I'd say that they've induced additional turbulence in the flow around the MAF sensor.
Is the volume of the filter chamber smaller in the Hyperflow than it is with the stock airbox?
Is the volume of the filter chamber smaller in the Hyperflow than it is with the stock airbox?
10-05-2007, 06:28 PM
#65
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i'm not saying it is, that was just an example...
to explain the relationship between airflow and fuel. look Scott, the air isn't metered, it's there, based on the design. the fuel is what's metered. basic Bosch Motronic.
that's why restricted airflow due to clogged filter will hurt performance and MPG, but not casue the engine to act up, except in extreme cases. the fuel delivery system compensates for less air flow, in those circumstances, by adjusting amount of fuel in the mix, via the injectors.
as for the the secondary air injection, some do introduce fresh air into the exhaust manifold ahead of the cat, to reduce emissions. but others, and sometimes a combination, introduce more air into intake for a leaner mixture. the cold idle speed is increased to accommodate it.
the breakthroughs that they are accomplishing with PZEV is in the more complete burning of fuel when engine cold. introduction of air increases the intake temp and aids in fuel atomization...which aids in the complete burning process...which helps lower emissions.
that's why restricted airflow due to clogged filter will hurt performance and MPG, but not casue the engine to act up, except in extreme cases. the fuel delivery system compensates for less air flow, in those circumstances, by adjusting amount of fuel in the mix, via the injectors.
as for the the secondary air injection, some do introduce fresh air into the exhaust manifold ahead of the cat, to reduce emissions. but others, and sometimes a combination, introduce more air into intake for a leaner mixture. the cold idle speed is increased to accommodate it.
the breakthroughs that they are accomplishing with PZEV is in the more complete burning of fuel when engine cold. introduction of air increases the intake temp and aids in fuel atomization...which aids in the complete burning process...which helps lower emissions.
10-05-2007, 06:38 PM
#66
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i think so...
talking about the same thing, airflow for power.
where you lose me is in conclusions drawn on the exact power loss, and what exactly is causing it. i think you're probably right, but looking at other RS4's tested in the press or with independant dynos, you seem to assume that the flap is working as it should on those RS4's just based on the numbers. whereas it doesn't work on people's RS4's here, based on a weak discussion of the matter. know what i mean?
anybody can pull their flap out for whatever perceived gain(power, sound, airflow), and that's fine. but there's no proof yet that it will solve any power issues, based on a lot of incomplete info and understanding of the damn thing.
my concern would be if by removing it, it's doing any other imperceptible damage. such as: running too lean, running too hot, affecting fuel injectors/deposits, influencing the ECU to make corrections that may not be desireable, etc.
where you lose me is in conclusions drawn on the exact power loss, and what exactly is causing it. i think you're probably right, but looking at other RS4's tested in the press or with independant dynos, you seem to assume that the flap is working as it should on those RS4's just based on the numbers. whereas it doesn't work on people's RS4's here, based on a weak discussion of the matter. know what i mean?
anybody can pull their flap out for whatever perceived gain(power, sound, airflow), and that's fine. but there's no proof yet that it will solve any power issues, based on a lot of incomplete info and understanding of the damn thing.
my concern would be if by removing it, it's doing any other imperceptible damage. such as: running too lean, running too hot, affecting fuel injectors/deposits, influencing the ECU to make corrections that may not be desireable, etc.
10-05-2007, 06:43 PM
#67
No...larger, but you can expect that fluctuation any time you take those datapoints...
if you looked at the range in values for OEM versus hyperflow they are not statistically significantly different.
10-05-2007, 06:45 PM
#68
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that's a good couple of points...
the noise and the airflow(cooling of intake temps).
i was thinking more of a top end speed tie-in to this flap. getting extra airflow for extra power...for RS4 max speed(150+ mph). it could be there just to kick it over the top...at top end. IMO.
i was thinking more of a top end speed tie-in to this flap. getting extra airflow for extra power...for RS4 max speed(150+ mph). it could be there just to kick it over the top...at top end. IMO.
10-06-2007, 03:57 AM
#69
Re: i think so...
No, actually I've seen some dynos in the press that exhibit the same issue with lack of torque boost at 5500 rpm.
As for running lean, the engine will correct. Bosch ME 9.1 will compensate for increased airflow in one engine revolution for mixtures that do not meet it's target at the wideband O2 sensors. There is realtime adjustment of the mixture in this engine, always.
As for running hot, that is a possibility that remains to be determine, and why I want to test it systematically.
As for running lean, the engine will correct. Bosch ME 9.1 will compensate for increased airflow in one engine revolution for mixtures that do not meet it's target at the wideband O2 sensors. There is realtime adjustment of the mixture in this engine, always.
As for running hot, that is a possibility that remains to be determine, and why I want to test it systematically.