Intake manifold theory
08-31-11, 10:51 AM
#1
Full Member
Thread Starter
Join Date: Jan 2008
Location: idaho
Posts: 232
Likes: 0
Received 0 Likes
on
0 Posts
Intake manifold theory
i'm curious if i used the wrong intake mani? i adapted a REW intake with a 1.25" spacer to my 6-port block. right now i seem to run out of breath around 7k-7.5k. this manifold is over 20" in runner length. i believe about 6" longer than a S4 N/A intake. plus the 1.25" adaptor plate.
My thoery was the longer runners would help torque? and now i don't think that was helping me as the torque side of this N/A motor is non-existent. the power-band does not come on till 5k. and ends shortly after.
block is a S4 6pi, halfbridged secondaries, stock pri, stock aux, stock exhaust.
afr's between 12.5-13.5, leading timing up to 26btdc. RB header.
thoeries?
My thoery was the longer runners would help torque? and now i don't think that was helping me as the torque side of this N/A motor is non-existent. the power-band does not come on till 5k. and ends shortly after.
block is a S4 6pi, halfbridged secondaries, stock pri, stock aux, stock exhaust.
afr's between 12.5-13.5, leading timing up to 26btdc. RB header.
thoeries?
08-31-11, 11:16 AM
#2
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,770
Received 2,562 Likes
on
1,822 Posts
mazda did a test of intake length vs power to get the stock S5's lengths.
however i think if you're too far out of the optimum range you just loose everywhere
however i think if you're too far out of the optimum range you just loose everywhere
08-31-11, 12:53 PM
#3
Old [Sch|F]ool
None of the turbo intake manifolds flow worth a damn. The pinch to clear the turbo kills them. The FD manifold looks extremely bad, I'm surprised people can make any power at all with that turd.
On my T2 keg, I picked up a whole lot of powerband down low and up top by adapting a S4 N/A intake manifold. With the T2 intake the engine would run out of breath around 8000. With the N/A manifold (lots of JB Weld to port match it), it would pull beyond the point where I had the guts to rev it (about 9500). This on a large street port/half bridge engine.
My experience with half-bridging a 6-port is that they just suck. The end ports close way too late for the engine to make any useful torque below 5000rpm no matter what you do.
On my T2 keg, I picked up a whole lot of powerband down low and up top by adapting a S4 N/A intake manifold. With the T2 intake the engine would run out of breath around 8000. With the N/A manifold (lots of JB Weld to port match it), it would pull beyond the point where I had the guts to rev it (about 9500). This on a large street port/half bridge engine.
My experience with half-bridging a 6-port is that they just suck. The end ports close way too late for the engine to make any useful torque below 5000rpm no matter what you do.
09-01-11, 07:44 AM
#4
Rotary Freak
I just would like to understand this because my experience on the race track showed me that the 88 S4 intake setup was noticeably quicker than the S5 setup on the same S5 motor. It pulled harder and was more flexible. Granted this was using a stock S4 ecu in both cases.
Just trying to learn something from the Mazda charts.
Eric
09-01-11, 12:35 PM
#5
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,770
Received 2,562 Likes
on
1,822 Posts
Maybe I am being stupid, but I have seen the above chart and other similar ones and I just don't understand where the starting point is. So does the chart refer to the use of a base S4 intake setup as the starting reference point and where does the 200 mm shorter or 400 mm longer come from? Is the measurement point from motor face to butterfly or is it from motor face to intake/throttlebody interface?
I just would like to understand this because my experience on the race track showed me that the 88 S4 intake setup was noticeably quicker than the S5 setup on the same S5 motor. It pulled harder and was more flexible. Granted this was using a stock S4 ecu in both cases.
Just trying to learn something from the Mazda charts.
Eric
I just would like to understand this because my experience on the race track showed me that the 88 S4 intake setup was noticeably quicker than the S5 setup on the same S5 motor. It pulled harder and was more flexible. Granted this was using a stock S4 ecu in both cases.
Just trying to learn something from the Mazda charts.
Eric
09-01-11, 02:28 PM
#7
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,770
Received 2,562 Likes
on
1,822 Posts
of course it didn't work, that would be too easy... try this
Trending Topics
09-01-11, 03:06 PM
#9
and where does the 200 mm shorter or 400 mm longer come from? Is the measurement point from motor face to butterfly or is it from motor face to intake/throttlebody interface?
The s4 has a fixed runner length, fixed intake pipe length, and only auxiliary ports really change with rpm. The secondary ports are staged mechanically based on the throttle linkage. S5 is similar except it has VDI, but is still not as efficient as the Renesis.
The turbo intake manifolds are designed for a turbo (duh). They're not optimized for an n/a application, just like the n/a manifold are not optimized for a turbo application. If Mazda could have used the same manifolds for both they would have saved a bunch of money, but they didn't do so for a reason.
I just would like to understand this because my experience on the race track showed me that the 88 S4 intake setup was noticeably quicker than the S5 setup on the same S5 motor. It pulled harder and was more flexible. Granted this was using a stock S4 ecu in both cases.
Just trying to learn something from the Mazda charts.
09-02-11, 07:49 AM
#12
Maybe I am being stupid, but I have seen the above chart and other similar ones and I just don't understand where the starting point is. So does the chart refer to the use of a base S4 intake setup as the starting reference point and where does the 200 mm shorter or 400 mm longer come from? Is the measurement point from motor face to butterfly or is it from motor face to intake/throttlebody interface?
I just would like to understand this because my experience on the race track showed me that the 88 S4 intake setup was noticeably quicker than the S5 setup on the same S5 motor. It pulled harder and was more flexible. Granted this was using a stock S4 ecu in both cases.
Just trying to learn something from the Mazda charts.
Eric
I just would like to understand this because my experience on the race track showed me that the 88 S4 intake setup was noticeably quicker than the S5 setup on the same S5 motor. It pulled harder and was more flexible. Granted this was using a stock S4 ecu in both cases.
Just trying to learn something from the Mazda charts.
Eric
increase runner length = shift your torque peak to a lower rpm
decrease runner length = shift your torque peak to a higher rpm
It doesn't say, and the s3/s4 intake manifold design is significantly different from the s5 and Renesis design. The early ones had a bigger plenum. The s5 and Renesis have very little (zero?) plenum and focus more on the runner length to affect it. The Renesis intake system is FAR superior to any Rx-7 intake. This is because it opens in 5 different stages based mostly on rpm: primary ports, then secondary ports, then auxiliary, then the intake pipe changes, then VDI opens up. The Renesis also has huge intake ports compared to the old 6 port engines.
send me a PM and I can get you the whole thing
and pm sent
09-02-11, 08:40 AM
#13
Full Member
Thread Starter
Join Date: Jan 2008
Location: idaho
Posts: 232
Likes: 0
Received 0 Likes
on
0 Posts
09-02-11, 10:00 AM
#14
Rotary Freak
[QUOTE=fidelity101;10771198]Okay here is an easy explanation:
increase runner length = shift your torque peak to a lower rpm
decrease runner length = shift your torque peak to a higher rpm
No kidding......... What I am trying to do is understand and establish what Mazda used in their development. A ton of intake manifold development has taken place over the years and when you review base concepts and SAE papers they always have the measurement criteria established. I have seen valve based engine intake development that measures from the front face of the valve all the way out to the mouth of the ITB bell. For rotaries, I have seen measurements from the mouth of the port as it opens into the chamber, back to the butterfly. I have also seen from the keg mounting face to the opening of the bell. The make bells in different lengths to change the torque curve profile.
There are soooo many variables when it comes to intake development, that I am always cautious just talking about adding 200 mm to an intake length will move my torque and horsepower curves X amount. I have always tried to understand the effects of runner diameter, runner length, mutual plenum volume and the effects of the length and volume of the intake chamber up stream of the throttle body. All of these have a strong effect on the power curve of a motor and its responsiveness to throttle inputs.
The papers sent to me by ARGHX has given me some clues as to how Mazda did their work. FYI they measured runner length from mounting face on the keg to mounting face between throttle body and intake. In my case, because I am running an individual runner 4 throat system, runner length goes from mounting face to openning of the bell as there is no mutual plenum to diffuse or reinforce intake charge effects.
When I developed my intake, I was targeting a max pulse charge point at 8,000 rpm and low and behold I am just short of that as the engine pulls hard to well over 9,000. What I surprised by is the amount of bottom end the engine still has. I am just trying to understand why. I am certain that having a 1/2 bridge is really effecting this as well.
Sorry for the long explanation, but anybody running a periport is basically running a 2 runner version of what I am running.
Eric
increase runner length = shift your torque peak to a lower rpm
decrease runner length = shift your torque peak to a higher rpm
No kidding......... What I am trying to do is understand and establish what Mazda used in their development. A ton of intake manifold development has taken place over the years and when you review base concepts and SAE papers they always have the measurement criteria established. I have seen valve based engine intake development that measures from the front face of the valve all the way out to the mouth of the ITB bell. For rotaries, I have seen measurements from the mouth of the port as it opens into the chamber, back to the butterfly. I have also seen from the keg mounting face to the opening of the bell. The make bells in different lengths to change the torque curve profile.
There are soooo many variables when it comes to intake development, that I am always cautious just talking about adding 200 mm to an intake length will move my torque and horsepower curves X amount. I have always tried to understand the effects of runner diameter, runner length, mutual plenum volume and the effects of the length and volume of the intake chamber up stream of the throttle body. All of these have a strong effect on the power curve of a motor and its responsiveness to throttle inputs.
The papers sent to me by ARGHX has given me some clues as to how Mazda did their work. FYI they measured runner length from mounting face on the keg to mounting face between throttle body and intake. In my case, because I am running an individual runner 4 throat system, runner length goes from mounting face to openning of the bell as there is no mutual plenum to diffuse or reinforce intake charge effects.
When I developed my intake, I was targeting a max pulse charge point at 8,000 rpm and low and behold I am just short of that as the engine pulls hard to well over 9,000. What I surprised by is the amount of bottom end the engine still has. I am just trying to understand why. I am certain that having a 1/2 bridge is really effecting this as well.
Sorry for the long explanation, but anybody running a periport is basically running a 2 runner version of what I am running.
Eric
09-02-11, 03:16 PM
#15
What I surprised by is the amount of bottom end the engine still has. I am just trying to understand why. I am certain that having a 1/2 bridge is really effecting this as well.
What makes all this tough is that none of us have access to the proprietary models and expensive software used by the OEM engineers. They can do all sorts of simulations to figure this stuff out. All we have all rules of thumb, basic calculations, and chassis dynos.
09-02-11, 06:02 PM
#16
Rotary Freak
For now just the *** dyno and on track performance compared to the previous setup. Where as before with the same motor and a 4 barrel holley and Racing Beat intake, the car would barely pull hard enough to load the back tires coming out of certain corners, now it will actually spin the back tires hard enough that I am counter steering a ton, like a freakin' V8 coming out of a second gear corner at 3,500 rpm. I can also leave 10 yard strips of black rubber when I choose coming out of corners again in second.
As well, I can stay with a lighter Peri port RX7 (makes high 280's to low 290's) all the way through second and only loose out when I have to shift first as I don't want to grenade the motor. I think once I complete the shift I pull just as hard in 3rd. The car is going on a chassis dyno after the next race and I will see what it is making and then have emperical data to compare to when the car was on the Holley and compared to the the previous motor which was the S5 reman using the S4 intake and ecu. Same exhaust on all 3 setups.
Eric
As well, I can stay with a lighter Peri port RX7 (makes high 280's to low 290's) all the way through second and only loose out when I have to shift first as I don't want to grenade the motor. I think once I complete the shift I pull just as hard in 3rd. The car is going on a chassis dyno after the next race and I will see what it is making and then have emperical data to compare to when the car was on the Holley and compared to the the previous motor which was the S5 reman using the S4 intake and ecu. Same exhaust on all 3 setups.
Eric
09-14-11, 04:40 PM
#17
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,770
Received 2,562 Likes
on
1,822 Posts
i just drove a stock S5 back to back with a stock S4
the S5 feels good, really flat powerband, its really strong between 3500-7000.
the S4 seems like the power curve is more curved, it starts coming on earlier, and falls off quicker, maybe 2500-5500? the S5 is a vert, so the 120lbs less weight S4 feels faster
the S5 feels good, really flat powerband, its really strong between 3500-7000.
the S4 seems like the power curve is more curved, it starts coming on earlier, and falls off quicker, maybe 2500-5500? the S5 is a vert, so the 120lbs less weight S4 feels faster
Thread
Thread Starter
Forum
Replies
Last Post
rgordon1979
3rd Generation Specific (1993-2002)
40
03-15-22 12:04 PM
