HKS talks about intakes for the RX-8
07-23-2007, 07:47 PM
#1
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HKS talks about intakes for the RX-8
I think it is time to talk modification again. I think I will go ananlytical from now on. Bring this forum back to life. This post has been hiding in other forum and my blog for a while.
This is the first of my translated Japanese magazine articles. More to come I promise. This is taken from the still current RX-7 magazine (May 2007)
“RX-8 air intake is a difficult subject and it is very sensitive to change. One must choose carefully,” said the intake designer at HKS.
Normally an open type intake works well for every car, since the best suction rate you can get is from this type of design. Totally open type in an Mazda RX-8, however, has an opposite effect.
If you want to increase the engine performance, the volume of air intake has to be increased. However, one must ensures cold air being taken in. Since high temperature air arising from an RX-8 has an increase total volume than colder air. Hence, a lower density of air particles, resulting from less air being taken in the end. The ECU also very sensitive to intake heat, and it may be the reason for reduction in engine power.
“On the other hand, if the box is totally sealed, the amount of air is certainly less than open type, hence performance of the intake will not be fully used. Therefore, the amount of open air expose to the intake, and the shape of the box, and where it opens are important.”
“We have produced the best intake whereby the intake amount and the air temp is balanced.”
Therefore, HKS opted for a suction intake has a shape not totally open or totally closed.
This is their analyses using different set ups.
Discussion
In my opinion, it is a very confusing article since the parameters on the graft are confusing.
The first graph indicates the temperature of the intake over engine revolution. It is very confusing since it is a difficult concept of the fact that the intake temp will reduce in hard revving. Does it mean more continuous air being sucked in and the actual temperate reading is being record by the sensor?
The dyno graph on the right shows marginal benefits. The max power difference at the top of the rev range is a mere 1-2kW. I hope they have factored in variations of power between runs on the same set up. This marginal result may not be argumentative enough.
To confuse me even more, the middle graph indicates a big variation between intake resistant versus the intake flow. The actual amount of flow in respect of the engine revolution/speed was not shown. I wonder how much of this graph translate to actual benefit of amount of air being taken in across the rev range.
The actual resistance benefit of the HKS filter element itself can be shown by comparing the result from both closed type boxes (the black graph and the blue graph). According to this, there is approximately 20-30% increase (~0.21 m3/sec to ~0.27 m3/sec at 4kPa of suction resistance). So I interpret that in the same type of box you use (close type), you will have increase of flow by 20-30% when you change to the HKS filter type alone. That is not great amount considering just changing the filter itself from MazdaSpeed, Pipercross (RMagic) and ITC will get at least 10-15% of improvement in filtration effort.
Conclusion
HKS has its point of balancing the amount of air and its temperature of an intake. I reckon there may be a better way then just merely opens the box and get more air flow, knowing they have done some sacrifice by getting small amount of bonnet air.
I think some sort of ram air via the bonnet may be a good solution, although it will not be rain proof.
This is the first of my translated Japanese magazine articles. More to come I promise. This is taken from the still current RX-7 magazine (May 2007)
“RX-8 air intake is a difficult subject and it is very sensitive to change. One must choose carefully,” said the intake designer at HKS.
Normally an open type intake works well for every car, since the best suction rate you can get is from this type of design. Totally open type in an Mazda RX-8, however, has an opposite effect.
If you want to increase the engine performance, the volume of air intake has to be increased. However, one must ensures cold air being taken in. Since high temperature air arising from an RX-8 has an increase total volume than colder air. Hence, a lower density of air particles, resulting from less air being taken in the end. The ECU also very sensitive to intake heat, and it may be the reason for reduction in engine power.
“On the other hand, if the box is totally sealed, the amount of air is certainly less than open type, hence performance of the intake will not be fully used. Therefore, the amount of open air expose to the intake, and the shape of the box, and where it opens are important.”
“We have produced the best intake whereby the intake amount and the air temp is balanced.”
Therefore, HKS opted for a suction intake has a shape not totally open or totally closed.
This is their analyses using different set ups.
Discussion
In my opinion, it is a very confusing article since the parameters on the graft are confusing.
The first graph indicates the temperature of the intake over engine revolution. It is very confusing since it is a difficult concept of the fact that the intake temp will reduce in hard revving. Does it mean more continuous air being sucked in and the actual temperate reading is being record by the sensor?
The dyno graph on the right shows marginal benefits. The max power difference at the top of the rev range is a mere 1-2kW. I hope they have factored in variations of power between runs on the same set up. This marginal result may not be argumentative enough.
To confuse me even more, the middle graph indicates a big variation between intake resistant versus the intake flow. The actual amount of flow in respect of the engine revolution/speed was not shown. I wonder how much of this graph translate to actual benefit of amount of air being taken in across the rev range.
The actual resistance benefit of the HKS filter element itself can be shown by comparing the result from both closed type boxes (the black graph and the blue graph). According to this, there is approximately 20-30% increase (~0.21 m3/sec to ~0.27 m3/sec at 4kPa of suction resistance). So I interpret that in the same type of box you use (close type), you will have increase of flow by 20-30% when you change to the HKS filter type alone. That is not great amount considering just changing the filter itself from MazdaSpeed, Pipercross (RMagic) and ITC will get at least 10-15% of improvement in filtration effort.
Conclusion
HKS has its point of balancing the amount of air and its temperature of an intake. I reckon there may be a better way then just merely opens the box and get more air flow, knowing they have done some sacrifice by getting small amount of bonnet air.
I think some sort of ram air via the bonnet may be a good solution, although it will not be rain proof.
07-24-2007, 03:13 AM
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Firstly...............
Thank you very much for going to the effort of translating that article. I know it can be quite difficult to get the grammar & meaning correct.
This is actually quite interesting & also explains why some guys using open pod filters are getting a power loss. Look at the 13`C difference at 8500rpm between the open & closed boxes.
The reason for the reduction in intake temps on the two closed boxes is simple. As the rpms rise, the intake is taking less & less warmed / cloaked air from around the frontal area as the scoop is at the front sealed from the engine bay. More outside air is drawn into the scoop as the revs climb, less chance of that air contacting vehicle parts & warming up.
The reason for the increase in temps from the open boxes is due to the intakes drawing from engine bay air as the demand for additional air flow increases. They rise with RPM because the engine stresses more as RPM rises, generates more heat from everything attached to it & is effectively a radiating element for the passing air to rush across & warm from on its way to the pod filter
Like water & electrical current. Air travels the path of least resistance from a high pressure (outside) to a low pressure (intake) zone. So the intake "will" take from the engine bay as thats the most direct route for the air to be sourced from.
Intake air resistance is more tricky (assumming I am reading this right) The stock box shows around 5KPA of flow/vacum? at just 0.22m cubed of air flow. However, the open box will flow 0.35m cubed for the same pressure meaning its flowing around 60% more air for the same pressure. Means you can get more air into the given area (air box) before it maxes out.
Very interesting read.
Thanks again.
REgards
Thank you very much for going to the effort of translating that article. I know it can be quite difficult to get the grammar & meaning correct.
This is actually quite interesting & also explains why some guys using open pod filters are getting a power loss. Look at the 13`C difference at 8500rpm between the open & closed boxes.
The reason for the reduction in intake temps on the two closed boxes is simple. As the rpms rise, the intake is taking less & less warmed / cloaked air from around the frontal area as the scoop is at the front sealed from the engine bay. More outside air is drawn into the scoop as the revs climb, less chance of that air contacting vehicle parts & warming up.
The reason for the increase in temps from the open boxes is due to the intakes drawing from engine bay air as the demand for additional air flow increases. They rise with RPM because the engine stresses more as RPM rises, generates more heat from everything attached to it & is effectively a radiating element for the passing air to rush across & warm from on its way to the pod filter
Like water & electrical current. Air travels the path of least resistance from a high pressure (outside) to a low pressure (intake) zone. So the intake "will" take from the engine bay as thats the most direct route for the air to be sourced from.
Intake air resistance is more tricky (assumming I am reading this right) The stock box shows around 5KPA of flow/vacum? at just 0.22m cubed of air flow. However, the open box will flow 0.35m cubed for the same pressure meaning its flowing around 60% more air for the same pressure. Means you can get more air into the given area (air box) before it maxes out.
Very interesting read.
Thanks again.
REgards
07-24-2007, 03:20 AM
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Ditto.
You hear a lot of people trashing aftermarket intakes for the car but very few who provide a detailed explanation why they do not necessarily work.
You hear a lot of people trashing aftermarket intakes for the car but very few who provide a detailed explanation why they do not necessarily work.
07-24-2007, 03:24 AM
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On a related note.
Mazda Australia guru, Mr Daniel Deckers learnt in the early 90's about this very issue with the FD RX-7 when they went racing at Bathurst etc.
Racing regs required the stockintake to be used. The series-6 (92-95) version had a single scoop providing air to both intake box & intercooler. Under racing conditions, the demand for air from the rotary engine was so high that the team found reverse air flow was occurring on the intercooler.
Meaning the intake was sucking heated air from the engine bay & the intercooler was having that same air running through it.
The results where pretty obvious. Intercooler failed to cool intake charge. Heated air resulted in power drop. Car would be good for only 2-3 laps before the Porsches started to catch up.
Result = RX-7 SP
Seperate the intake & intercooler scoops. Larger intakes & intercooler. Intake temps now remained steady, intercooler received continuous cool air. Power stayed reliable.
Mazda Australia guru, Mr Daniel Deckers learnt in the early 90's about this very issue with the FD RX-7 when they went racing at Bathurst etc.
Racing regs required the stockintake to be used. The series-6 (92-95) version had a single scoop providing air to both intake box & intercooler. Under racing conditions, the demand for air from the rotary engine was so high that the team found reverse air flow was occurring on the intercooler.
Meaning the intake was sucking heated air from the engine bay & the intercooler was having that same air running through it.
The results where pretty obvious. Intercooler failed to cool intake charge. Heated air resulted in power drop. Car would be good for only 2-3 laps before the Porsches started to catch up.
Result = RX-7 SP
Seperate the intake & intercooler scoops. Larger intakes & intercooler. Intake temps now remained steady, intercooler received continuous cool air. Power stayed reliable.
07-24-2007, 04:46 AM
#5
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Yes it is very clear and documented here now that sucking heated air will reduced power.
I would like to draw people attention to the difference between a sealed box and the half open box that HKS has.
1. The power difference is minimal.
2. The half open has a 4-5 degree C higher temp than closed ones.
3. The closed box has about 20% less volume of air intake at the same intake pressure.
That is why at the end I question what an intake tube will do. Like Revi intake or RE Amemiya intake, something that is very big. Some kind of modification to allow direct open air to the intake is the most ideal. Currently, the intake outlet after the VFAD is very small. That is why the close type has less benefit.
You will be surprised how much interesting stuff there are in the Japanese mag.
I would like to draw people attention to the difference between a sealed box and the half open box that HKS has.
1. The power difference is minimal.
2. The half open has a 4-5 degree C higher temp than closed ones.
3. The closed box has about 20% less volume of air intake at the same intake pressure.
That is why at the end I question what an intake tube will do. Like Revi intake or RE Amemiya intake, something that is very big. Some kind of modification to allow direct open air to the intake is the most ideal. Currently, the intake outlet after the VFAD is very small. That is why the close type has less benefit.
You will be surprised how much interesting stuff there are in the Japanese mag.
07-24-2007, 07:17 AM
#6
I would like to draw people attention to the difference between a sealed box and the half open box that HKS has.
1. The power difference is minimal.
2. The half open has a 4-5 degree C higher temp than closed ones.
3. The closed box has about 20% less volume of air intake at the same intake pressure.
1. The power difference is minimal.
2. The half open has a 4-5 degree C higher temp than closed ones.
3. The closed box has about 20% less volume of air intake at the same intake pressure.
Really good article to post. Wish it was not in a regional forum though, since it's something all of us should be looking at.
What this graph shows is what we should all expect by now - the closed intake that Mazda developed is pretty damn good, and difficult to improve on.
It also shows all the lousy open intakes (The K&N's, the GReddy turbo and Pettit supercharger) are not ideal.
07-24-2007, 07:37 AM
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Found a decent cold air scoop for the RX-8 designed to fit the OEM air box.
Purchase & postage to Oz around $250
Gets more cold air into the closed box
REgards
Purchase & postage to Oz around $250
Gets more cold air into the closed box
REgards
07-24-2007, 04:19 PM
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DMHR
My home made cold air ram duct / scoop made out of airconditioning 4" aluminium duct works great and fits myaftermarket racing beat air box
drawing cold air from the outside .protected by the hymee grill from debris .
Ben
My home made cold air ram duct / scoop made out of airconditioning 4" aluminium duct works great and fits myaftermarket racing beat air box
drawing cold air from the outside .protected by the hymee grill from debris .Ben
Last edited by erx8s; 07-24-2007 at 04:27 PM.
07-24-2007, 05:18 PM
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DMRH,
I use that.
https://www.rx8club.com/showthread.p...ighlight=odula
I posted the same in the modification section.
I use that.
https://www.rx8club.com/showthread.p...ighlight=odula
Originally Posted by mysql101
Really good article to post. Wish it was not in a regional forum though, since it's something all of us should be looking at.
07-25-2007, 08:50 AM
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DMRH,
I use that.
https://www.rx8club.com/showthread.p...ighlight=odula
I posted the same in the modification section.
I use that.
https://www.rx8club.com/showthread.p...ighlight=odula
I posted the same in the modification section.
Seems I am quite behind the times here.
REgards
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