porting Q's
07-31-14, 05:26 PM
#1
Junior Member
Thread Starter
porting Q's
just a few questions about it
im just wondering why does a PP move the power band further up the rev range is it due to the size of the port or the position or is it a combination of both?
also just out of interest not sure if its possible but could you keep the same power band say as street port with a PP?
Thanks
im just wondering why does a PP move the power band further up the rev range is it due to the size of the port or the position or is it a combination of both?
also just out of interest not sure if its possible but could you keep the same power band say as street port with a PP?
Thanks
07-31-14, 05:53 PM
#2
the simple answer is overlap. the size that full peripherals have to be in order to make good power introduces much more overlap than stock or stock-ish ports.
if you check the New Member Tech section there is a sticky thread on porting that may shed better light on the subject.
if you check the New Member Tech section there is a sticky thread on porting that may shed better light on the subject.
07-31-14, 06:10 PM
#3
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the P ports are generally done to have maximum power, which means highest RPM possible. the intakes and exhausts are usually tuned to work best at high rpm too.
the part that nobody mentions though is that the P port, even tuned in high power trim makes more power at low rpm than a street port, it then goes on to make another 50+ hp higher up.
i have a 12A P port, its nothing fancy, hug ports, 48 IDA weber, locked timing, and it makes more power under 4000rpm than a stock port 12A with bolt ons does @7000.
with mine i am using the stock 12A air cleaner to keep it quiet, and this is limiting me to about ~170rwhp at about 5500rpm. there is another 50 in it with a better air cleaner, and more rpm
so its a yes, but you leave a lot on the table
the part that nobody mentions though is that the P port, even tuned in high power trim makes more power at low rpm than a street port, it then goes on to make another 50+ hp higher up.
i have a 12A P port, its nothing fancy, hug ports, 48 IDA weber, locked timing, and it makes more power under 4000rpm than a stock port 12A with bolt ons does @7000.
with mine i am using the stock 12A air cleaner to keep it quiet, and this is limiting me to about ~170rwhp at about 5500rpm. there is another 50 in it with a better air cleaner, and more rpm
so its a yes, but you leave a lot on the table
08-01-14, 03:05 PM
#4
Junior Member
Thread Starter
the simple answer is overlap. the size that full peripherals have to be in order to make good power introduces much more overlap than stock or stock-ish ports.
if you check the New Member Tech section there is a sticky thread on porting that may shed better light on the subject.
if you check the New Member Tech section there is a sticky thread on porting that may shed better light on the subject.
only other question i have is what about some sort of rectangular intake port keeping it as high as you can and only bringing it down close to the exhaust port to get the desired size so it gives a big of opening as possible without creating a huge overlap
would that keep the power band wider?
08-01-14, 04:43 PM
#5
cheers i just read your write up its very helpful,
only other question i have is what about some sort of rectangular intake port keeping it as high as you can and only bringing it down close to the exhaust port to get the desired size so it gives a big of opening as possible without creating a huge overlap
would that keep the power band wider?
Nope, you have it backwards. Overlap increases the engines Volumetric Efficiency at all RPM ranges and that is why Peripheral Port motors make more low end power (and top end power) than street port motors.
If you want to somehow limit the high rpm power of a peripheral port motor so it has the same power band as a street port you could, but I don't know why you would want to.
Mazda used rectangular peripheral ports for qualifying because they have more volume per port timing than the round ones so they make more peak power, but the rectangular ports have a more peaky power band because at lower rpms the port velocity/inertia is lower.
im just wondering why does a PP move the power band further up the rev range is it due to the size of the port or the position or is it a combination of both?
Again, P-port provides a wider powerband than sideport. They have the ability for more top end power due to less intake restriciton (straight shot into engine) and more favorable timing available (more intake biased overlap).
Yes, the volume of a port (side or peripheral) will affect the power curve as the larger volume will have less low rpm velocity/inertia to overcome compression stroke reversion (and so less low end power). Larger volume port will also have less restriction to flow at high rpm (so more high end power). Larger volume = less low end, more top end.
Yes, moving the port closing line (not opening line, ie overlap) further into the compression stroke will also lower low rpm power where the compression stroke will revert out the intake and increase top end power when the intake velocity/inertia overcomes the compression reversion.
As stated all this is skewed because most p-port motors are developed for racing (emphasis on top end power) and so will have late port closing. The higher you rev and engine while still maintaining torque the more horsepower (work) you make- so they concentrate on top end power. ie Natually Aspirated tuning theory.
only other question i have is what about some sort of rectangular intake port keeping it as high as you can and only bringing it down close to the exhaust port to get the desired size so it gives a big of opening as possible without creating a huge overlap
would that keep the power band wider?
Nope, you have it backwards. Overlap increases the engines Volumetric Efficiency at all RPM ranges and that is why Peripheral Port motors make more low end power (and top end power) than street port motors.
If you want to somehow limit the high rpm power of a peripheral port motor so it has the same power band as a street port you could, but I don't know why you would want to.
Mazda used rectangular peripheral ports for qualifying because they have more volume per port timing than the round ones so they make more peak power, but the rectangular ports have a more peaky power band because at lower rpms the port velocity/inertia is lower.
im just wondering why does a PP move the power band further up the rev range is it due to the size of the port or the position or is it a combination of both?
Again, P-port provides a wider powerband than sideport. They have the ability for more top end power due to less intake restriciton (straight shot into engine) and more favorable timing available (more intake biased overlap).
Yes, the volume of a port (side or peripheral) will affect the power curve as the larger volume will have less low rpm velocity/inertia to overcome compression stroke reversion (and so less low end power). Larger volume port will also have less restriction to flow at high rpm (so more high end power). Larger volume = less low end, more top end.
Yes, moving the port closing line (not opening line, ie overlap) further into the compression stroke will also lower low rpm power where the compression stroke will revert out the intake and increase top end power when the intake velocity/inertia overcomes the compression reversion.
As stated all this is skewed because most p-port motors are developed for racing (emphasis on top end power) and so will have late port closing. The higher you rev and engine while still maintaining torque the more horsepower (work) you make- so they concentrate on top end power. ie Natually Aspirated tuning theory.
08-01-14, 07:08 PM
#6
Junior Member
Thread Starter
cheers i just read your write up its very helpful,
only other question i have is what about some sort of rectangular intake port keeping it as high as you can and only bringing it down close to the exhaust port to get the desired size so it gives a big of opening as possible without creating a huge overlap
would that keep the power band wider?
Nope, you have it backwards. Overlap increases the engines Volumetric Efficiency at all RPM ranges and that is why Peripheral Port motors make more low end power (and top end power) than street port motors.
If you want to somehow limit the high rpm power of a peripheral port motor so it has the same power band as a street port you could, but I don't know why you would want to.
Mazda used rectangular peripheral ports for qualifying because they have more volume per port timing than the round ones so they make more peak power, but the rectangular ports have a more peaky power band because at lower rpms the port velocity/inertia is lower.
im just wondering why does a PP move the power band further up the rev range is it due to the size of the port or the position or is it a combination of both?
Again, P-port provides a wider powerband than sideport. They have the ability for more top end power due to less intake restriciton (straight shot into engine) and more favorable timing available (more intake biased overlap).
Yes, the volume of a port (side or peripheral) will affect the power curve as the larger volume will have less low rpm velocity/inertia to overcome compression stroke reversion (and so less low end power). Larger volume port will also have less restriction to flow at high rpm (so more high end power). Larger volume = less low end, more top end.
Yes, moving the port closing line (not opening line, ie overlap) further into the compression stroke will also lower low rpm power where the compression stroke will revert out the intake and increase top end power when the intake velocity/inertia overcomes the compression reversion.
As stated all this is skewed because most p-port motors are developed for racing (emphasis on top end power) and so will have late port closing. The higher you rev and engine while still maintaining torque the more horsepower (work) you make- so they concentrate on top end power. ie Natually Aspirated tuning theory.
only other question i have is what about some sort of rectangular intake port keeping it as high as you can and only bringing it down close to the exhaust port to get the desired size so it gives a big of opening as possible without creating a huge overlap
would that keep the power band wider?
Nope, you have it backwards. Overlap increases the engines Volumetric Efficiency at all RPM ranges and that is why Peripheral Port motors make more low end power (and top end power) than street port motors.
If you want to somehow limit the high rpm power of a peripheral port motor so it has the same power band as a street port you could, but I don't know why you would want to.
Mazda used rectangular peripheral ports for qualifying because they have more volume per port timing than the round ones so they make more peak power, but the rectangular ports have a more peaky power band because at lower rpms the port velocity/inertia is lower.
im just wondering why does a PP move the power band further up the rev range is it due to the size of the port or the position or is it a combination of both?
Again, P-port provides a wider powerband than sideport. They have the ability for more top end power due to less intake restriciton (straight shot into engine) and more favorable timing available (more intake biased overlap).
Yes, the volume of a port (side or peripheral) will affect the power curve as the larger volume will have less low rpm velocity/inertia to overcome compression stroke reversion (and so less low end power). Larger volume port will also have less restriction to flow at high rpm (so more high end power). Larger volume = less low end, more top end.
Yes, moving the port closing line (not opening line, ie overlap) further into the compression stroke will also lower low rpm power where the compression stroke will revert out the intake and increase top end power when the intake velocity/inertia overcomes the compression reversion.
As stated all this is skewed because most p-port motors are developed for racing (emphasis on top end power) and so will have late port closing. The higher you rev and engine while still maintaining torque the more horsepower (work) you make- so they concentrate on top end power. ie Natually Aspirated tuning theory.
cheers that has really cleared up alot for me guess ill do the round p ports based on the thread i seen on this forum on how to do them
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