What modifications do in terms of tuning... Part 1: Intake Manifold
Thread Starter
Evolved Member
Joined: Oct 2002
Posts: 2,788
Likes: 1
I run Autronic SM4 which has no knock control. For everyday driving I do have a Knockblock from Link but I can't say I've been too happy with it. I have it setup so if the Knockblock reaches a certain voltage alarm LEDS will go off on my AIM dash. But I have it turned off right now.
CR,
A change in the intake side will NOT decrease back pressure. One of the reasons for this is because there is NO SUCH thing as back pressure. Its called capacity. In order for an engine to process more air it will have to allow for a better pressure differential across all cylinders on the intake and the exhaust system as a whole.
A change in the intake side will NOT decrease back pressure. One of the reasons for this is because there is NO SUCH thing as back pressure. Its called capacity. In order for an engine to process more air it will have to allow for a better pressure differential across all cylinders on the intake and the exhaust system as a whole.
Okay I'm in 
2 things that I can see as maybe a flaw apart from where I see you are taking the discussion.
One being that, if you have a "better" manifold, one would tend to see the initial torque being shifted later in the rpm band, not earlier. I think we have seen this in DB's manifold tests. Every one was compared to stock and every aftermarket manifold lost initial hp and tq.
...but lets say hypothetically, one could achieve what you are asking for. Your map is still skewed because all the cells the were at peak tq and hp have now been shifted negatively(on the x axis, to the left) of your map. So, technically you need to recalibrate to a new map and take into conisderation your changes.
My take on your theory is this. As long as you can achieve cooler temps, through efficiency or cooler fuel or whatever you'll make better hp and therefor more tq. In your "better" manifold it would be efficiency that got you the torque increase, along with the extra air. The additional air would also help to absorb some of the heat, which helps make more torque.
Someone smack me if I'm talking out my butt.
Random thought occurs here: Anyone, use anything to cool their fuel?
2 things that I can see as maybe a flaw apart from where I see you are taking the discussion.
One being that, if you have a "better" manifold, one would tend to see the initial torque being shifted later in the rpm band, not earlier. I think we have seen this in DB's manifold tests. Every one was compared to stock and every aftermarket manifold lost initial hp and tq.
...but lets say hypothetically, one could achieve what you are asking for. Your map is still skewed because all the cells the were at peak tq and hp have now been shifted negatively(on the x axis, to the left) of your map. So, technically you need to recalibrate to a new map and take into conisderation your changes.
My take on your theory is this. As long as you can achieve cooler temps, through efficiency or cooler fuel or whatever you'll make better hp and therefor more tq. In your "better" manifold it would be efficiency that got you the torque increase, along with the extra air. The additional air would also help to absorb some of the heat, which helps make more torque.
Someone smack me if I'm talking out my butt.
Random thought occurs here: Anyone, use anything to cool their fuel?
On some units you will notice a decrease in low end torque numerically because you have effectively changed the dynamic combustion process. Much like adding cams you change the dynamic compression slightly. The "turbo" in most cases will show you an increase in boost threshold.
"Cooler" fuel does not mean better power in every case. A stable temperature that allows the promotion of vaporization is what will yield constant powerful results. That along with proper flame front travel and propagation. What you should ask yourself is what does that after market runner do to velocity versus flow in the rpm band you plan on running. Also how well does the fuel atomize in different situations based on temperature and velocity.
Before you think about power/pressure from the ignition, think about what is happening in the cylinder. You have a certain amount of air and fuel which provide a certain amount of stored energy. The better intake manifold provides more stored energy than the original manifold. In this situation, regardless of your ignition timing you have more stored energy available. Because of this, if you keep your ignition timing the same your peak cylinder pressure will be slightly higher. If you retard the ignition timing slightly, you can keep the peak cylinder pressure the same while making more power due to more energy provided by the original charge. Hopefully I didn't get too wordy and confusing in the way I typed this.
-Paul
-Paul
Its not necessarily the "fuel". Its the pockets of air and fuel in the chamber that will ignite prematurely. Think of them as pockets or areas of air and fuel with a void between the next plot of A/F. Pockets with the right amount of droplets attaching themselves to the oxygen molecule will burn completely thru when conditions are optimal.
Thread Starter
Evolved Member
Joined: Oct 2002
Posts: 2,788
Likes: 1
CR,
A change in the intake side will NOT decrease back pressure. One of the reasons for this is because there is NO SUCH thing as back pressure. Its called capacity. In order for an engine to process more air it will have to allow for a better pressure differential across all cylinders on the intake and the exhaust system as a whole.
A change in the intake side will NOT decrease back pressure. One of the reasons for this is because there is NO SUCH thing as back pressure. Its called capacity. In order for an engine to process more air it will have to allow for a better pressure differential across all cylinders on the intake and the exhaust system as a whole.
"Now if the intake manifold had somehow relieved back pressure, or cooled the intake charge, I might say, well hey it may have actually helped fight det because of those attributes. But the intake manifold does neither, but I know it does other things but don't understand them well."
DTM I'd love to hear your take on what the intake manifold does exactly. From my understanding the only thing I can think of is better velocity, more flow, more turbulence for better air/fuel atomization.
Thread Starter
Evolved Member
Joined: Oct 2002
Posts: 2,788
Likes: 1
Its not necessarily the "fuel". Its the pockets of air and fuel in the chamber that will ignite prematurely. Think of them as pockets or areas of air and fuel with a void between the next plot of A/F. Pockets with the right amount of droplets attaching themselves to the oxygen molecule will burn completely thru when conditions are optimal.
I.m not sure I follow this well. The intake manifold has stored energy? Maybe the capacity for more airflow. BUT the airmass has to be able to bond to the fuel molecules presented in the port and combustion chamber. The more they are broken down and attach the more energy potential you have.
Its not necessarily the "fuel". Its the pockets of air and fuel in the chamber that will ignite prematurely. Think of them as pockets or areas of air and fuel with a void between the next plot of A/F. Pockets with the right amount of droplets attaching themselves to the oxygen molecule will burn completely thru when conditions are optimal.
As I said in my previous post, I don't see this being as much a function of intake manifold design as it is a function of head and piston design. Getting the proper "swirl" during the compression stroke will do more to help mix the air and fuel than an intake manifold. These items will remain constant when changing an intake manifold and will have little effect on the gains provided by the manifold.
CR,
A change in the intake side will NOT decrease back pressure. One of the reasons for this is because there is NO SUCH thing as back pressure. Its called capacity. In order for an engine to process more air it will have to allow for a better pressure differential across all cylinders on the intake and the exhaust system as a whole.
A change in the intake side will NOT decrease back pressure. One of the reasons for this is because there is NO SUCH thing as back pressure. Its called capacity. In order for an engine to process more air it will have to allow for a better pressure differential across all cylinders on the intake and the exhaust system as a whole.
Call it what you want, but there is pressure between the turbine wheel and the exhaust valves. I call that back pressure, maybe you call it something different. If you have more back pressure you will have more combustion products remaining in the cylinder when the exhaust valves close. This will limit the amount fresh air and fuel you can pull into the cylinder on the subsequent intake stroke.
On some units you will notice a decrease in low end torque numerically because you have effectively changed the dynamic combustion process. Much like adding cams you change the dynamic compression slightly. The "turbo" in most cases will show you an increase in boost threshold...
"Cooler" fuel does not mean better power in every case. A stable temperature that allows the promotion of vaporization is what will yield constant powerful results. That along with proper flame front travel and propagation. What you should ask yourself is what does that after market runner do to velocity versus flow in the rpm band you plan on running. Also how well does the fuel atomize in different situations based on temperature and velocity.
Evolved Member
Joined: Jan 2008
Posts: 874
Likes: 0
From: Australia
I run Autronic SM4 which has no knock control. For everyday driving I do have a Knockblock from Link but I can't say I've been too happy with it. I have it setup so if the Knockblock reaches a certain voltage alarm LEDS will go off on my AIM dash. But I have it turned off right now.
Peak cyl pressure is always the same angle no matter what load, rpm, afr, etc, only changes in the combustion chamber will change that. But if you change the burn rate (boost, dynamic compression, swirl, valve timing, charge volume, knock, etc) or fuel type the amount of spark timing needed to get PPP will also change.
crcain look into this for knockdevices. Better then the knocklink.
http://www.phormula.co.uk/KnockDetection-KS-3.aspx
http://www.phormula.co.uk/KnockDetection-KS-3.aspx
