fs vs. f2
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the F2 has 1 3/4" primaries which retains low-end torque but hurts high-end power, more suited to the D20
the FS/OBX/Cossie has 1 7/8" primaries and a different routing which sacrifices the low end but gives a much more linear power curve with lots of high-end NA power
the FS/OBX/Cossie has 1 7/8" primaries and a different routing which sacrifices the low end but gives a much more linear power curve with lots of high-end NA power
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Look at it this way. If you aren't racing it you will want the low end power. The HP benefits you will see by making the motor breath exceedingly well with the OBX/Focussport will only be seen in the very high RPM range. Like 5500-7000.
See the thing is that when the motor breathes well it basically never peaks in HP during the entire RPM range. For the sake of argument lets say your peak HP is 150. If the motor breathes very well then you will probably not see that until redline. The motor wants to keep generating HP but is limited by the rev limit on your car at that point.
Now when you restrict airflow (basically if you use the F2 over the OBX) then your car will peak more in the middle of the RPM range. So you will have that 150hp at a much more useable range than if you had to climb all the way up the power band to obtain it. So around the town get up and go will be more pronounced than if you had the motor breath very well.
Look at it this way. The car needs some backpressure to retain its low end power. Here is a little analogy. You have a large diameter straw and a small diameter straw. You blow into both. You will be able to produce a much faster airflow through the smaller straw because there is resistance there. The bigger straw your air is quickly depleted and the airflow is very slow. Therefore you must breathe again, sooner to keep any airflow up. The same principle applies to a motor. If you go with a smaller exhaust system yes there will be more pressure there but the motor will get more "useable" work down low because it will be able to keep air coming in and out of the motor quick enough at low RPM whereas with the bigger exhaust system you just aren't inducing enough air fast enough to keep the flow out of the motor up.
Big exhaust is good for full race applications where all the motor sees is high rpm and the motor has the capability to take in enough air to blow through at a good speed. I hope all this makes sense. Feel free to PM me if you need clarification. lol.
It also depends on the motor though. The 2.0 just doesn't have the flow capabilities on the intake side as the 2.3 has. The 2.3 has a dual stage intake manifold just like the SVT which switches to short runners at high RPM to keep breathing at an optimum. The head on the 2.3 also has higher flow characteristics through it than the 2.0 so in all honesty the 2.3 would have a much easier time using the OBX or Focussport sized header than the 2.0. I should say it would make a better powerband than the 2.0.
It all depends on what you want outta the car though. Honestly I don't race around much. I did some datalogging and had member Illinipo read it for me to determine a possible problem and the first thing he said was boy you are an easy driver aren't you. lol. Its just who I am. So I rarely see those high rpm. If I were to build an all out racecar I would definately go with the OBX or Focussport system with some high lift/duration cams and the Cossie IM but for now the F2 suffices. I also have the 2.3 as well so its an entirely different beast as far as this goes.
Take a look at the dyno sheets. Mine is up there as well as some other peoples. Learn to read the torque and HP lines and make your decision from that. The sheets can tell you more than I ever could.
Anyway... Enough babbling... Hope this all made sense.
See the thing is that when the motor breathes well it basically never peaks in HP during the entire RPM range. For the sake of argument lets say your peak HP is 150. If the motor breathes very well then you will probably not see that until redline. The motor wants to keep generating HP but is limited by the rev limit on your car at that point.
Now when you restrict airflow (basically if you use the F2 over the OBX) then your car will peak more in the middle of the RPM range. So you will have that 150hp at a much more useable range than if you had to climb all the way up the power band to obtain it. So around the town get up and go will be more pronounced than if you had the motor breath very well.
Look at it this way. The car needs some backpressure to retain its low end power. Here is a little analogy. You have a large diameter straw and a small diameter straw. You blow into both. You will be able to produce a much faster airflow through the smaller straw because there is resistance there. The bigger straw your air is quickly depleted and the airflow is very slow. Therefore you must breathe again, sooner to keep any airflow up. The same principle applies to a motor. If you go with a smaller exhaust system yes there will be more pressure there but the motor will get more "useable" work down low because it will be able to keep air coming in and out of the motor quick enough at low RPM whereas with the bigger exhaust system you just aren't inducing enough air fast enough to keep the flow out of the motor up.
Big exhaust is good for full race applications where all the motor sees is high rpm and the motor has the capability to take in enough air to blow through at a good speed. I hope all this makes sense. Feel free to PM me if you need clarification. lol.
It also depends on the motor though. The 2.0 just doesn't have the flow capabilities on the intake side as the 2.3 has. The 2.3 has a dual stage intake manifold just like the SVT which switches to short runners at high RPM to keep breathing at an optimum. The head on the 2.3 also has higher flow characteristics through it than the 2.0 so in all honesty the 2.3 would have a much easier time using the OBX or Focussport sized header than the 2.0. I should say it would make a better powerband than the 2.0.
It all depends on what you want outta the car though. Honestly I don't race around much. I did some datalogging and had member Illinipo read it for me to determine a possible problem and the first thing he said was boy you are an easy driver aren't you. lol. Its just who I am. So I rarely see those high rpm. If I were to build an all out racecar I would definately go with the OBX or Focussport system with some high lift/duration cams and the Cossie IM but for now the F2 suffices. I also have the 2.3 as well so its an entirely different beast as far as this goes.
Take a look at the dyno sheets. Mine is up there as well as some other peoples. Learn to read the torque and HP lines and make your decision from that. The sheets can tell you more than I ever could.
Anyway... Enough babbling... Hope this all made sense.
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since i wanted the IM anyways, I wanna get the f2 and the cosworth so then i have the best of both worlds [
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I would have to disagree w/ you on this Justin, if you look at are dyno's you can see that we both reach peak HP at about the same RPM 5.8. both of or peaks go form about 5.8 and carry over till about 6.3-6.5 pretty close if you ask my. And correct my if I'm wrong (which you prolly will b/c I'm prolly wrong) but I though that our engine is just a big air pump, so to try to blow in a smaller straw would not be an accurate analogy. I think if you took two straws one bigger than the other like you said and put them in a cup of water and drink....what cup do you think would empty first...this is a picture of you gas tank....lol..but to be serious here, it looks like to me that we are pretty much the same w/ the exception that you have a 2.3 w/ an F2 and I have a 2.0 w/ an OBX..now here is your turn to correct me...lol... Mr. Auto Mechanic
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I think what I meant to mean with that straw analogy is that with the bigger straw you must stop and take another breath faster to keep the air moving through at a constant speed than with a smaller straw. The same is with our motors. If the exhaust is too big then it simply cannot suck in enough air at the lower RPM that is necessary for getting the most outta the exhaust. This is also why FI cars need bigger exhausts. Simply because instead of sucking air in they are more or less blowing it through the car at a much faster rate than NA could ever do.
I should have clarified some things though. (this was at like 10 at night so i was tired... lol) You will see definate gains with both headers on both motors for sure. The difference in size really is negatable until you get into high HP builds and such. So take what I said above with a grain of salt with our cars. It really was more of a discussion on big exhaust principles in general.
I should have clarified some things though. (this was at like 10 at night so i was tired... lol) You will see definate gains with both headers on both motors for sure. The difference in size really is negatable until you get into high HP builds and such. So take what I said above with a grain of salt with our cars. It really was more of a discussion on big exhaust principles in general.
i think i'll be going with the f2 as well. as a general rule i like to consider my redline as being 5500. i've always said, if i can't beat them without going over 5500, i don't need to beat them. so a lower powerband will be just right. but i also have the 2.3, so maybe i won't even have to worry about it. :]
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I think for the 2.3 you would want the OBX...IMO. Just b/c you already have a sweet IM and the primaries on the OBXs' are bigger than the f2 JMO though, I would assume your going to get a tune down the road too and your car would theoreticly breath better w/ lets say a 2.5" exhaust and a 4-1 (1 7/8) header.
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the header does? hummmm.....FS header/ FS CAI/ FS exhaust...FTW!!!!!
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wow n2o...didnt know that...so yeah, that would make up the diff in price right there. ceramic heat coating is good stuff. then again, you could always wrap the f2. it has a coating to protect from moisture, so it shouldnt crack. as justin said, id go with the f2 in general, just cuz i would never expect to be hitting over 5500! whats the point of hitting all ur power so high, with less tq? thats what makes the focus good....its tq, when compared to so many other cars.
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I love to race my little focus against all the haters out there!!( leagally of course)
what would be the best header for someone like me?
dont wanna steal the thread, which one is for raceing which is for driving?
what would be the best header for someone like me?
dont wanna steal the thread, which one is for raceing which is for driving?
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6,877 Posts
id say its a tossup...the lower-end tq will pull you off the line faster, so you will have a better launch. as you get to the higher end, you may lose a bit of distance, as your HP drops off. maybe. but would you be shifting higher than 5500?
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