6 port HP!
02-20-07, 10:24 AM
#51
Originally Posted by rotarygod
Back pressure NEVER makes torque. Back pressure is ALWAYS the enemy! Period. The thing that many people fail to think about is flow and velocity. Yes you want flow. In a perfect world you want a pipe that flows a proprtionate amount of air to the engines needs. At lower rpms the engine flows less air. Velocity in the exhaust stream is important in making power as inertia will help pull more gasses along the pipe between power pulses. If you make the pipe too large you decrease this effect and hurt power. More or bigger is not always better. This includes with porting. Too many people go too large and this is especially true on exhaust ports.
Why then does a smaller pipe make more low end power than a larger one? It's not backpressure. It's flow! A pipe of any given size can only flow so much air with so much restriction. When testing this on a flowbench we need to determine a base pressure. It's worthless to state any flow level in cfm without also having a reference pressure. Let's say pipe A flows 300 cfm and pipe B flows 200 cfm. From looking at it we'd come to the logical conclusion that pipe A flows more. Are we sure? Were they tested at the same reference pressure? What if pipe A was tested at a reference pressure of 28" H2O and pipe B were tested at a reference pressure of 14" H2O? If we tested them both at 28" H2O, pipe B would actually flow closer to 400 cfm (maybe not exactly but you get the idea). How would you know?
I needed to tell you that so my example would be a little bit clearer when it comes to flow. Keep in mind that I'm making all of these numbers up but do assume that they are all at the same reference pressure.
Let's say a 2" pipe flows 100 cfm, a 2.5" pipe flows 200 cfm, and a 3" pipe flows 300 cfm. More is better right? Is it? Is the 3" pipe really a restriction? What if the engine at 8000 rpm's only flows 200 cfm? Was the 3" pipe really better? Both it and the 2.5" pipe could flow the required amount of air but the 2.5" pipe would have higher velocity inside and would make more average power. Yes going larger kills low end power. What about going smaller? Let's say we change our pipe down to a 2" pipe. We can already tell that top end power is going to suffer. This is because we have too much backpressure. Remember that backpressure is always a bad thing. Let's say our engine flows 100 cfm at 5000 rpm. We can see that our pipe would be sized to flow the perfect velocity at this rpm. This means that average airflow through the pipe is also faster on average below this point than in a larger pipe. More velocity is more power. Velocity is what makes power. Once our pipe becomes a restriction (wahtever that rpm may be), the effort required to squeeze and speed up the air going through the pipe is greater than the gain from having higher velocity and power starts falling. This car would have more power to about 5000 rpm than the car with the larger pipe but it wouldn't have the top end power. Yes it has a smaller pipe and yes that pipe is adding backpressure. But it only does it above 5000 rpm yet low end was increased. This is because it wasn't the backpressure at all that was making better low end power. It was velocity!
Remember I made these numbers up but the example is sound. There is more to exhaust tuning than this of course but I was merely tryling to dispell the whole backpressure and low end torque misconception.
Keep true duals OFF of bridge or peripheral port motors if you want to get max power out of them. Yes you'll make power on them with true duals. Just not nearly as much as a proper collected system can.
Why then does a smaller pipe make more low end power than a larger one? It's not backpressure. It's flow! A pipe of any given size can only flow so much air with so much restriction. When testing this on a flowbench we need to determine a base pressure. It's worthless to state any flow level in cfm without also having a reference pressure. Let's say pipe A flows 300 cfm and pipe B flows 200 cfm. From looking at it we'd come to the logical conclusion that pipe A flows more. Are we sure? Were they tested at the same reference pressure? What if pipe A was tested at a reference pressure of 28" H2O and pipe B were tested at a reference pressure of 14" H2O? If we tested them both at 28" H2O, pipe B would actually flow closer to 400 cfm (maybe not exactly but you get the idea). How would you know?
I needed to tell you that so my example would be a little bit clearer when it comes to flow. Keep in mind that I'm making all of these numbers up but do assume that they are all at the same reference pressure.
Let's say a 2" pipe flows 100 cfm, a 2.5" pipe flows 200 cfm, and a 3" pipe flows 300 cfm. More is better right? Is it? Is the 3" pipe really a restriction? What if the engine at 8000 rpm's only flows 200 cfm? Was the 3" pipe really better? Both it and the 2.5" pipe could flow the required amount of air but the 2.5" pipe would have higher velocity inside and would make more average power. Yes going larger kills low end power. What about going smaller? Let's say we change our pipe down to a 2" pipe. We can already tell that top end power is going to suffer. This is because we have too much backpressure. Remember that backpressure is always a bad thing. Let's say our engine flows 100 cfm at 5000 rpm. We can see that our pipe would be sized to flow the perfect velocity at this rpm. This means that average airflow through the pipe is also faster on average below this point than in a larger pipe. More velocity is more power. Velocity is what makes power. Once our pipe becomes a restriction (wahtever that rpm may be), the effort required to squeeze and speed up the air going through the pipe is greater than the gain from having higher velocity and power starts falling. This car would have more power to about 5000 rpm than the car with the larger pipe but it wouldn't have the top end power. Yes it has a smaller pipe and yes that pipe is adding backpressure. But it only does it above 5000 rpm yet low end was increased. This is because it wasn't the backpressure at all that was making better low end power. It was velocity!
Remember I made these numbers up but the example is sound. There is more to exhaust tuning than this of course but I was merely tryling to dispell the whole backpressure and low end torque misconception.
Keep true duals OFF of bridge or peripheral port motors if you want to get max power out of them. Yes you'll make power on them with true duals. Just not nearly as much as a proper collected system can.
02-20-07, 10:27 AM
#52
Originally Posted by Karack
ahh ****.... here we go with the scientific reasonoing.
#1 little secret i will tell you is scientific reasearch is not always as on the dot as most of us would like to think. my most recent delve into this subject was on a truck with lugnuts that were LH threaded on one side and RH threaded on the other side, i'm sure someone had scientific reasoning to back that one up as well. smaller pipe does increase velocity but also does create a small amount of backpressure.
most guys straight out of college with too much time on their hands always tend to think they are right and will never admit to being wrong. personally i don't care either way.
and no i couldn't stand to read the whole thread or replies.
#1 little secret i will tell you is scientific reasearch is not always as on the dot as most of us would like to think. my most recent delve into this subject was on a truck with lugnuts that were LH threaded on one side and RH threaded on the other side, i'm sure someone had scientific reasoning to back that one up as well. smaller pipe does increase velocity but also does create a small amount of backpressure.
most guys straight out of college with too much time on their hands always tend to think they are right and will never admit to being wrong. personally i don't care either way.
and no i couldn't stand to read the whole thread or replies.
02-20-07, 11:07 AM
#53
Originally Posted by philiptompkins
I can't say who's correct here BUT I can tell you that Rotary God is not just out of college and has been at this a loooong time.
02-20-07, 02:25 PM
#54
Passing life by
Still doesn’t hold a candle to the scientific theory that physics do not LIE and the bottom line truth is BP does not make power in any way what so ever nor is BP good for an engine! Whoever puts BP in there question should just be ignored from there on out plain and simple.
Exhaust can not add power ever, exhaust can only free up power the motor has already made.
And allot of older European cars used reverse threaded lug nuts.
Exhaust can not add power ever, exhaust can only free up power the motor has already made.
And allot of older European cars used reverse threaded lug nuts.
02-20-07, 02:54 PM
#55
Originally Posted by Karack
ahh ****.... here we go with the scientific reasonoing.
#1 little secret i will tell you is scientific reasearch is not always as on the dot as most of us would like to think. my most recent delve into this subject was on a truck with lugnuts that were LH threaded on one side and RH threaded on the other side, i'm sure someone had scientific reasoning to back that one up as well. smaller pipe does increase velocity but also does create a small amount of backpressure.
most guys straight out of college with too much time on their hands always tend to think they are right and will never admit to being wrong. personally i don't care either way.
and no i couldn't stand to read the whole thread or replies.
#1 little secret i will tell you is scientific reasearch is not always as on the dot as most of us would like to think. my most recent delve into this subject was on a truck with lugnuts that were LH threaded on one side and RH threaded on the other side, i'm sure someone had scientific reasoning to back that one up as well. smaller pipe does increase velocity but also does create a small amount of backpressure.
most guys straight out of college with too much time on their hands always tend to think they are right and will never admit to being wrong. personally i don't care either way.
and no i couldn't stand to read the whole thread or replies.
I have seen people do things the same way for years and it becomes habit for them and that's the only thing they know. Then of course they preach their ways to others who assume they must be correct due to years of experience. What if that person never actually did it properly in the first place? What if they continued doing it this way and teaching it to others? Does that suddenly make it correct? The point is that just building engines and bolting things on them doesn't mean a whole lot in the long run. Trial and error, testing, and actually learning why things work the way they do leads to results and sometimes those results are completely surprising. Why? Because what people logically think "should" happen vs what actually "does" happen, is not always in agreement. The funny thing is that EVERY result can be explained scientifically. Go complain about it but science is based on physics and so is the way everything works in your engine. If your explanation differs from the science aspect of it, you used the wrong scientific reasoning! You can't get a math problem right if you used the wrong formula.
Go back and study exhaust theory some more. Then you'll understand backpressure vs velocity a little better and how you can actually have less than ambient pressure in the exhaust.
Thankfully I haven't been wrong twice yet! 
02-20-07, 03:43 PM
#59
Originally Posted by Sideways7
Actually, 6 ports will produce better power than 4 ports when NA.
As for power, you can get 160-165 to the wheels with a good street port. Put on a fuel controller and get it tuned and you are looking at 10-15 more than that. With a full standalone and a good tune you are looking at 180-190 to the wheels, and you can theoretically get even more than that with a really good port job and some luck.
All of this is assuming a fresh rebuild, straight-through exhaust, a cone filter with CAI, and s5 intake.
As for power, you can get 160-165 to the wheels with a good street port. Put on a fuel controller and get it tuned and you are looking at 10-15 more than that. With a full standalone and a good tune you are looking at 180-190 to the wheels, and you can theoretically get even more than that with a really good port job and some luck.
All of this is assuming a fresh rebuild, straight-through exhaust, a cone filter with CAI, and s5 intake.
I've seen a dyno of an S5 with a custom intake manifold, ecu, rb exhaust and 4 x 550 injectors. Made 190 - 195 whp NA, but tuner (Kahren) said it was running out of fuel so it couldn't go any higher. In the dyno graph, power was still climbing at 8000, so the intake manifold wasn't sized right either. Still, impressive power.
02-20-07, 06:23 PM
#60
Passing life by
That doesn’t matter either because TQ doesn’t matter didaly unless you’re trying to pull a tanker truck up a hill. In a sports car we are trying to race around from point A to point B as fast as we possibly can. For this TQ don’t matter at all. We are interested in the HP curve and peak.
02-20-07, 07:15 PM
#61
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Originally Posted by Aaron Cake
Beat me too it. 
If you are going to do a bridgeport NA, do it right and do a full bridge or half bridge.
If the car is turbocharged, then the aux bridge will make a huge difference as far as spool goes but you might as well just continue the bridge down and make a proper half bridge...A bridge is a bridge is a bridge as far as characteristics go...
If you are going to do a bridgeport NA, do it right and do a full bridge or half bridge.
If the car is turbocharged, then the aux bridge will make a huge difference as far as spool goes but you might as well just continue the bridge down and make a proper half bridge...A bridge is a bridge is a bridge as far as characteristics go...
But what about if the operation of the auxiliary ports was to be kept intact while bridge porting the aux ports? Is the aux-bridge still such a bad idea? You can retain the driveability and fuel consumption of a relatively mild port rotary under low RPM/low engine loading, but take advantage of the higher flowing bridge port under high engine load once the aux ports open up.
02-20-07, 10:30 PM
#62
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The argument is that the intake pressure waves of the aux ports and secondary ports will **** with eachother wince they share a common runner. basically no one has proven that an Aux port bridge, with functioning sleeves or not, provides more power than a good streetport. I have an aux bridge with functioning sleeves. Once I get my exhaust sorted out Im going to dyno it and post the results.
Right now it feels like the stock exhaust manifold is suffocating the engine. After about 7000 rpms the engine falls on its face. Im not sure if its the exhaust or a fueling issue, but since Im going to be setting up my exhaust either way Ill find out when I dyno the car. In either case there is a lot to be made up with a custom intake manifold and standalone. Im sure that an intake that creates an individual runner for each aux port would make a big difference in how the engine responded.
BC
Right now it feels like the stock exhaust manifold is suffocating the engine. After about 7000 rpms the engine falls on its face. Im not sure if its the exhaust or a fueling issue, but since Im going to be setting up my exhaust either way Ill find out when I dyno the car. In either case there is a lot to be made up with a custom intake manifold and standalone. Im sure that an intake that creates an individual runner for each aux port would make a big difference in how the engine responded.
BC
02-20-07, 10:43 PM
#63
If you have a bridgeport and a stock exhaust manifold it will definitely affect power. You really NEED to get a good header (collected not true dual) type of system on there for max benefit. Start with the exhaust and then work on the fuel later if you find you are running out.
The stock ecu doesn't use the stock injectors to their fullest potential. Of course we already knew that. Once the secondary injectors come online, the primaries fall down to 40% duty cycle and never go above it again. This means that when you max out your injectors with the stock ecu, you are really only maxing out the secondaries. The primaries have much to go. A standalone will take care of this issue but you can program it to do the same thing. Get a standalone before you worry about the fuel system. Even with stock injectors you've got enough for an n/a.
There is a reason why they did this and why I am also doing nearly the same thing with speedmonkey's megasquirt. Atomization. You really want the fuel injectors to be farther away as rpms rise. It gives more time for fuel to atomize but you need the added air velocity from higher rpms to take advantage of it. The stock ecu does this to a point. After the secondaries kick in, it adds more fuel as rpm's rise but it favors the secondaries rather than splitting the duty up equally for atomization reasons. On speedmonkey's car, ultimately after we get it tuned it, the primaries will shut off completely after a certain load and/or rpm is hit. Of course we need to size the secondaries accordingly but the reasons behind it are the same. I spoke to David Haskell of Speedsource Racing about this technique at Sevenstock last year and this is actually exactly how they do it on their race engines and for the same reasons.
The stock ecu doesn't use the stock injectors to their fullest potential. Of course we already knew that. Once the secondary injectors come online, the primaries fall down to 40% duty cycle and never go above it again. This means that when you max out your injectors with the stock ecu, you are really only maxing out the secondaries. The primaries have much to go. A standalone will take care of this issue but you can program it to do the same thing. Get a standalone before you worry about the fuel system. Even with stock injectors you've got enough for an n/a.
There is a reason why they did this and why I am also doing nearly the same thing with speedmonkey's megasquirt. Atomization. You really want the fuel injectors to be farther away as rpms rise. It gives more time for fuel to atomize but you need the added air velocity from higher rpms to take advantage of it. The stock ecu does this to a point. After the secondaries kick in, it adds more fuel as rpm's rise but it favors the secondaries rather than splitting the duty up equally for atomization reasons. On speedmonkey's car, ultimately after we get it tuned it, the primaries will shut off completely after a certain load and/or rpm is hit. Of course we need to size the secondaries accordingly but the reasons behind it are the same. I spoke to David Haskell of Speedsource Racing about this technique at Sevenstock last year and this is actually exactly how they do it on their race engines and for the same reasons.
02-20-07, 10:59 PM
#64
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So what are you guys thinking abotu running for secondaries? 800 or 1000cc injectors???
Im going down the path that you described exactly btw. I have read a lot of your opinions on the aux bridge setup, and bridge ports in general, and am following that path. I have a collected header and presilencer sitting in my trunk now that is going to be installed hopefully this saturday. Im probably going to run it as a single out the passenger side, and somewhere down the line run a boost referenced cutoutjust before the differential running off the airpump flow to the VDI. VDI opens, so does the cutout. (thats like a final step in my plans though.) Right now Im just waiting on Zeal to get their MS PnP together, or for RTEK to get their S5 na setup going, whomever gets their out first.
BC
Im going down the path that you described exactly btw. I have read a lot of your opinions on the aux bridge setup, and bridge ports in general, and am following that path. I have a collected header and presilencer sitting in my trunk now that is going to be installed hopefully this saturday. Im probably going to run it as a single out the passenger side, and somewhere down the line run a boost referenced cutoutjust before the differential running off the airpump flow to the VDI. VDI opens, so does the cutout. (thats like a final step in my plans though.) Right now Im just waiting on Zeal to get their MS PnP together, or for RTEK to get their S5 na setup going, whomever gets their out first.
BC
02-20-07, 11:23 PM
#65
Passing life by
Originally Posted by anewconvert
So what are you guys thinking abotu running for secondaries? 800 or 1000cc injectors???
Im going down the path that you described exactly btw. I have read a lot of your opinions on the aux bridge setup, and bridge ports in general, and am following that path. I have a collected header and presilencer sitting in my trunk now that is going to be installed hopefully this saturday. Im probably going to run it as a single out the passenger side, and somewhere down the line run a boost referenced cutoutjust before the differential running off the airpump flow to the VDI. VDI opens, so does the cutout. (thats like a final step in my plans though.) Right now Im just waiting on Zeal to get their MS PnP together, or for RTEK to get their S5 na setup going, whomever gets their out first.
BC
Im going down the path that you described exactly btw. I have read a lot of your opinions on the aux bridge setup, and bridge ports in general, and am following that path. I have a collected header and presilencer sitting in my trunk now that is going to be installed hopefully this saturday. Im probably going to run it as a single out the passenger side, and somewhere down the line run a boost referenced cutoutjust before the differential running off the airpump flow to the VDI. VDI opens, so does the cutout. (thats like a final step in my plans though.) Right now Im just waiting on Zeal to get their MS PnP together, or for RTEK to get their S5 na setup going, whomever gets their out first.
BC
http://www.clubfc3s.com/forums/index.php?showtopic=583
02-21-07, 12:00 AM
#67
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Originally Posted by iceblue
not a registered user. Since I just registered they wont let me look at the link until I have been approved by an admin.
grrrr
BC
02-21-07, 12:20 AM
#68
Why is this still going on? You can do a search on the side debate topics. They've been discussed before.
Basically:
Basically:
- See my post on page 2 for everything needed for streetable power.
- A bridge port will allow even more power up top. It'll be streetable down below but low end power won't be much better than a stock port. Mpg and emissions will tank royally. A peripheral port works even better, though with a higher cost and the same problems.
- You can increase your redline by having your rotors balanced. However, you'll need to get your engine ported to get any decent power at the higher rpms. After a street port, that may be the way to go for (relatively) reliable power beyond what I mentioned. Though it seems most people gamble with aggressive tuning instead (SAFC 2 or a standalone ECU).
- I hear 13B N/A's top out at an unreliable 300HP (wHP?). I imagine that would be peripheral ported, high redline and tuned to unsafe settings.
- Everything I mentioned I picked up from these forums. I know nothin' first hand. You can do a search to answer all your questions.
02-21-07, 12:25 AM
#69
Originally Posted by anewconvert
So what are you guys thinking abotu running for secondaries? 800 or 1000cc injectors???
Im going down the path that you described exactly btw. I have read a lot of your opinions on the aux bridge setup, and bridge ports in general, and am following that path. I have a collected header and presilencer sitting in my trunk now that is going to be installed hopefully this saturday. Im probably going to run it as a single out the passenger side, and somewhere down the line run a boost referenced cutoutjust before the differential running off the airpump flow to the VDI. VDI opens, so does the cutout. (thats like a final step in my plans though.) Right now Im just waiting on Zeal to get their MS PnP together, or for RTEK to get their S5 na setup going, whomever gets their out first.
BC
Im going down the path that you described exactly btw. I have read a lot of your opinions on the aux bridge setup, and bridge ports in general, and am following that path. I have a collected header and presilencer sitting in my trunk now that is going to be installed hopefully this saturday. Im probably going to run it as a single out the passenger side, and somewhere down the line run a boost referenced cutoutjust before the differential running off the airpump flow to the VDI. VDI opens, so does the cutout. (thats like a final step in my plans though.) Right now Im just waiting on Zeal to get their MS PnP together, or for RTEK to get their S5 na setup going, whomever gets their out first.
BC
Don't think I'm a bridgeport hater. I'm not. I just don't like them on the street. There are too many sacrifices necessary to get their true potential out of them.
For right now we are using 550 primaries and 720 secondaries. I want to get it running nicely first and to do that it's staying simple with a more conventional approach. This way if it takes longer to get the other way dialed in, all I have to do is switch maps and injectors. Removing the manifold isn't even a 5 minute job on his car now. It's simple.
I am using the dual table maps. One fuel map is for the primary injectors only. I have a second independent map that is only for the secondaries. This way I can bring them online at a higher rpm and load level. This also gives me the ability to dial in more map points through the rpm range than the standard mapping would allow. I can fine tune off boost and crusie with the primaries due to more map points within those areas and at the same time get the same benefit under boost with the secondaries. Since ultimately all of his fuel under boost will taper off to just 2 fuel injectors after some point, I need to compensate for this with added injector on the order of double what he'd normally use. I have a pair of 1600's sitting around that I may try as I'm not using them anyways. I'd really rather have 4 smaller injectors instead of 2 large ones as I would prefer to have fuel flowing down all the runners as opposed to half of them. I'll worry about that when I get there. Ultimately welding on 2 additional injector bungs to the primaries up high next to the secondaries and then running 4-550's or 720's would be the best option.
02-21-07, 12:37 AM
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Originally Posted by iceblue
That doesn’t matter either because TQ doesn’t matter didaly unless you’re trying to pull a tanker truck up a hill. In a sports car we are trying to race around from point A to point B as fast as we possibly can. For this TQ don’t matter at all. We are interested in the HP curve and peak.
02-21-07, 12:47 AM
#73
Originally Posted by zoomman
this is probably the worst statement of all time. first of all if you dont have enough torque to spin you wheels, then all the hp in the world wont save you. you'd just be sittn there at the line while some *shudders* honda beats you off the line. im not saying hp curves arnt important but hp and torque go together like peas and carrots. you cant have one without the other and expect anything good. and i know u said in daily usage...but if u think about it, if you had more torque from your car, you wouldnt have to mash the gas down so much to get up to speed, and then you would just save gas. which is why the v8 swap guys can get like 28 mpg out of thier rides.
02-21-07, 12:50 AM
#74
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Originally Posted by rotarygod
Yep. It's got it. No one really takes advantage of it though.
remind me to hunt you down relentlessly when I need to find someone who can explain intakes to me
that being said the GF may overwhelm me eventually and force me to upgrade to an 8 before I get too far along on the 7. For some reason she likes AC during the summer in NC... who knows.
BC
02-21-07, 01:29 AM
#75
As far as I know I was the first person to run an RX-8 on a Megasquirt! Actually it was fuel only but it wasn't hard to do. Ignition would have been easy to do if the code had been written for the RX-8 trigger wheel. I hear it'll be available soon though.