My rant on my new exhaust
#21
05-23-2011, 02:41 AM
This thread's all over the place...
To the OP:
"Performance exhaust" isn't simply hacking the OE piping and slapping a fart pipe on it. Manufacturers of quality exhaust systems do R&D in efforts to get the best sound, overall broadest ranger of power and torque, and quality construction that will last.
Your method of hacking, splicing, rehacking, and resplicing sounds like a pain in the ass. If you'd just leave the engineering to the professionals and just cough up the money for a purpose-built exhaust for your Fit then you could probably have a nice sounding exhaust that won't compromise low end, midrange, or top end power/torque.
To the OP:
"Performance exhaust" isn't simply hacking the OE piping and slapping a fart pipe on it. Manufacturers of quality exhaust systems do R&D in efforts to get the best sound, overall broadest ranger of power and torque, and quality construction that will last.
Your method of hacking, splicing, rehacking, and resplicing sounds like a pain in the ass. If you'd just leave the engineering to the professionals and just cough up the money for a purpose-built exhaust for your Fit then you could probably have a nice sounding exhaust that won't compromise low end, midrange, or top end power/torque.
#23
05-23-2011, 06:45 AM
If you have a free flowing exhaust that is straight through in design you are going to have a terrible droning sound in 5th between 60n and 80 MPH... A'pexi makes a cable actuated exhaust control valve that can be tweaked a little from the drivers seat to bring the sound more tolerable. In the city it can be completely closed and as quiet as stock when you need to be a bit stealthy...
#24
05-23-2011, 08:10 AM
Texas that was the first thing I looked for was an exhaust valve of some sort and all I could find was a dump valve. I may have to search a little more and get one.
As for the comment of "silly people" and I'm assuming this is in reference to me. I had a good american made straight through muffler welded on and a straight pipe welded in place of my res. and that makes me so called "silly" My exhaust performance wise and sound wise is as good as any $500 dollar unit...wish I had all stainless pipes, but I only have $175 into it.
as for mufflers with 3" or 4" openings...that's the tip size not the size pipe ran. anyone that would put larger than 2" pipe with a wide open on a fit would lose all low end torque and have hellish drone. A 427 big block only needs around 2" pipes.
As for the comment of "silly people" and I'm assuming this is in reference to me. I had a good american made straight through muffler welded on and a straight pipe welded in place of my res. and that makes me so called "silly" My exhaust performance wise and sound wise is as good as any $500 dollar unit...wish I had all stainless pipes, but I only have $175 into it.
as for mufflers with 3" or 4" openings...that's the tip size not the size pipe ran. anyone that would put larger than 2" pipe with a wide open on a fit would lose all low end torque and have hellish drone. A 427 big block only needs around 2" pipes.
#25
05-23-2011, 08:34 AM
The A'Pexi exhaust control valve is available on ebay. I have Header , resonated down pipe into 2 1/2" B pipe all Megan, into 3" the valve that is sandwiched between 2 flanges into a 3" inside diameter Vibrant resonator into an Aero Turbine 4" inside diameter muffler with 4" outlet..The B pipe had about a 1/4" plate on the end with about a 1 1/2" hole in it that I cut off... There was a loss of low end torque right of the line unless I revved it up a bit and lit up the front tires.. The valve gives me more torque for stop and go driving in traffic at very low RPM but it still does well even when it is wide open thanks to 10PSI boost by way of KWSC high boost kit, 93 octane fuel and liberal doses of octane booster. .
#26
05-23-2011, 09:02 AM
Thats awesome. I would like to boost mine, but until then I just wanted to be able to hear my muffler without spending an arm or a leg or an arm and a leg.
I bet your fit is fast as sh$t...any videos of it?
when I make my last payment the real fun will begin until then I have to work with a naturally aspirated engine.
So when you want low end torque you shut your valve to get some more low end? I think you are helping to prove my case.
I bet your fit is fast as sh$t...any videos of it?
when I make my last payment the real fun will begin until then I have to work with a naturally aspirated engine.
So when you want low end torque you shut your valve to get some more low end? I think you are helping to prove my case.
#27
05-23-2011, 09:13 AM
Texas I wanted to let you know I did the 93 octane switch from 87 and I think it was a good move. I can just tell the difference in the driving experience...not sure how to explain it...smoother maybe. Have yet to run the mpg, when I had the wide open without the reduction my mpg went way down and when adding my silencer it went back up...so now I'm settled in and can get some real results.
#28
05-23-2011, 10:20 AM
Join Date: Sep 2010
Location: Chicago, Illinois
Posts: 4,424
Where did you pull that figure out of? 
One 427 BBC is not the same as all other 427s. What Cam/Head/Intake are they using? Is it boosted?Even were they comparable in setup, the next question is what will they be used for?
A 427 that redlines at 5k rpm and a 427 that winds out to 7k are going to have entirely different needs.
One 427 BBC is not the same as all other 427s. What Cam/Head/Intake are they using? Is it boosted?Even were they comparable in setup, the next question is what will they be used for?
A 427 that redlines at 5k rpm and a 427 that winds out to 7k are going to have entirely different needs.
Last edited by DiamondStarMonsters; 05-23-2011 at 10:33 AM.
#29
05-23-2011, 10:31 AM
a boosted engine is another monster alltogether. I am reffering to naturally aspirated engines. Hot rodders have figured all this out fifty odd years ago and its what you want out of your engine...do you want low end, high end or a comprimise in the middle. These old timers will know off the top of their heads what size pipes to use for what size engine to get your power where you want it. Boosted I don't know anything about but I hope when it comes time that people will share there wisdom with me so I can avoid pitfalls.
#30
05-23-2011, 10:38 AM
Join Date: Sep 2010
Location: Chicago, Illinois
Posts: 4,424
That's kind of a non answer... Here is the very simple math involved with figuring out flow requirements:
So I havent posted anything useful in here for a while it feels like, so here is a bit of DIY flow optimisation I performed the last few weeks.
After feeling like there was more to be eeked out of my intake system I went through and did a rough approximation of my pressure drop across the core, the swing in temp from the exducer on the compressor wheel to the throttle body as well as flow velocity and found some interesting numbers.
I lose about 4psi across the intercooler at 38psi, so fortunately that still keeps me withing the efficiency island I want as well as the compressor speed lines left on the map. My turbo is built to support pressure ratios as high as 55psi, so 38 + 4 only puts me at 42psi, or a PR of ~3.0.
So now that I have determined that the charge cooler is up to the task it is time to work my way through the rest of the intake, so lets start at the cone filter..
Let me preface this by saying in revisiting the rough calculations I did the first time, I am shocked I was able to move as much air as I do, and that this next round of surgery on the Laser should yield some big gains in flow. I want to push this turbo to its choke flow!
So originally I only intended on being able to do 40lbs/min on pump gas because it is a relatively small turbo, only 59mm at the inlet.
All my calculations were only intending to see 400whp worth of air on pump gas, while I knew that when I turned up the wick I would be using a different fuel and the smaller intake system would yield greater flow velocity which means more torque.
And that all turned out to be true, but I didnt think I would be pushing 60lbs/min in an internally wastegated .55A/R turbine housing on a 74mm exhaust wheel..so I in tuning purely for torque, I lost out on top end VE.
This is why I got the bigger core and changed my IC piping and air filter.
So starting with the air filter on the pre-turbo intake pipe.. for 400whp I established I will need about 40lbs/min according to my engines brake specific fuel consumption.
40lbs/min at 0.076lbs/ft3 makes for 525cfm. Ideally you want about 120-140ft/min charge face velocity entering the intake system to reduce restriction as much as possible.
So 525cfm divided by 130ft/min gives us an area of 4ft2.
4ft2 times 144in2/1ft2 gives us 580in2 minimum filter surface area required to meet this goal.
Now how the f*ck do I figure out the SA of a cone filter? Well not so bad really..
After feeling like there was more to be eeked out of my intake system I went through and did a rough approximation of my pressure drop across the core, the swing in temp from the exducer on the compressor wheel to the throttle body as well as flow velocity and found some interesting numbers.
I lose about 4psi across the intercooler at 38psi, so fortunately that still keeps me withing the efficiency island I want as well as the compressor speed lines left on the map. My turbo is built to support pressure ratios as high as 55psi, so 38 + 4 only puts me at 42psi, or a PR of ~3.0.
So now that I have determined that the charge cooler is up to the task it is time to work my way through the rest of the intake, so lets start at the cone filter..
Let me preface this by saying in revisiting the rough calculations I did the first time, I am shocked I was able to move as much air as I do, and that this next round of surgery on the Laser should yield some big gains in flow. I want to push this turbo to its choke flow!
So originally I only intended on being able to do 40lbs/min on pump gas because it is a relatively small turbo, only 59mm at the inlet.
All my calculations were only intending to see 400whp worth of air on pump gas, while I knew that when I turned up the wick I would be using a different fuel and the smaller intake system would yield greater flow velocity which means more torque.
And that all turned out to be true, but I didnt think I would be pushing 60lbs/min in an internally wastegated .55A/R turbine housing on a 74mm exhaust wheel..so I in tuning purely for torque, I lost out on top end VE.
This is why I got the bigger core and changed my IC piping and air filter.
So starting with the air filter on the pre-turbo intake pipe.. for 400whp I established I will need about 40lbs/min according to my engines brake specific fuel consumption.
40lbs/min at 0.076lbs/ft3 makes for 525cfm. Ideally you want about 120-140ft/min charge face velocity entering the intake system to reduce restriction as much as possible.
So 525cfm divided by 130ft/min gives us an area of 4ft2.
4ft2 times 144in2/1ft2 gives us 580in2 minimum filter surface area required to meet this goal.
Now how the f*ck do I figure out the SA of a cone filter? Well not so bad really..
So now the we know the required SA for the filter it is time to find a filter that fits the bill.
Just so happens that there is a popular and affordable 9"L 4"-5"W cone filter from K&N with a 4" mouth. So does it have the SA to flow at the rate we need to make 400whp efficiently?
We need to know:
Pleat height
Pleat depth
# of pleats
So the one I have is 9" pleat height, with .55" pleat depth and about 60 pleats.
SA (in2) = Height times Depth times # of pleats times 2 [for each side of the (pleat)]
SA = 9 x .55 x 60 x 2
SA = ~590in2
590in2 > 580in2 so it'll work but just barely. That is with a 9" x 5" filter with a 4" outlet! And it is just enough for only 400whp!
Just so happens that there is a popular and affordable 9"L 4"-5"W cone filter from K&N with a 4" mouth. So does it have the SA to flow at the rate we need to make 400whp efficiently?
We need to know:
Pleat height
Pleat depth
# of pleats
So the one I have is 9" pleat height, with .55" pleat depth and about 60 pleats.
SA (in2) = Height times Depth times # of pleats times 2 [for each side of the (pleat)]
SA = 9 x .55 x 60 x 2
SA = ~590in2
590in2 > 580in2 so it'll work but just barely. That is with a 9" x 5" filter with a 4" outlet! And it is just enough for only 400whp!
Now the next part is how big should my pre-turbo intake pipe be? Well thats easy.. as big or bigger than the compressor inlet. In my case that is 4", and 4" the pipe shall be.
That was easy enough, so how big do the post compressor charge pipes have to be? Well again I am just using the 400whp (525cfm) figure for this demonstration... so lets take a look.
Post turbo you want to keep flow face velocity within a certain sweet spot. That is about 200-300ft/min.
So what I chose was 2.75", which has a cross section of 0.04ft2, so 525cfm will have a face velocity of about 215ft/sec, which is acceptable.
Velocity = Volumetric Flow Rate / Pipe cross section
Velocity = 525cfm / 0.04ft2
Velocity = ~215ft/sec
Because I know it will be on the big size for 400whp, but it also needs to be able to handle my high boost tune which is moving 600whp worth of air, or about 790cfm.. and even then 790cfm / 0.041ft2 gives me a face velocity of ~325ft/sec, which again still works with the 200-300ft/sec sweet spot.
Now to make things more confusing I am also accounting for changes in temperature and pressure across the system all the way to the cylinder head.
Something peculiar happens right at the throttle body elbow that helped me keep my decision to go with 2.75" charge pipes.. my water/meth kit cools the charge so effectively it becomes denser as it enters the manifold and the "tight" piping keeps flow velocity up as it enters the manifold and runners while it is simulataneously shrinking in volume and consequently flow velocity.
To yet further complicate things my thought process also had to account for how all of this would affect the vaporization and required activation energy on my 4 different fuel constituents.
I expect the charge air to remain relatively warm since it leaves the turbo at around 260F and after the IC and piping it then enters the heat soaked manifold and cylinder head where it starts to heat up again,
This heat helps the alcohol atomize and absorb heat, yet leave enough energy in to allow the toluene and gasoline to light off with relative ease.
Because the combination of the alcohol, water, toluene and premium gas resists knock so well, I can leave the charge temps relatively warm.
So then I can be aggressive in my spark timing and fuel scheme. The cooled but still warm charge allows the fuel to spray fine and even, but the residual heat means even a weak spark can burn the whole mixture and rapidly.
.
.
Now here is the part that was kind of shocking.. for 600whp (790cfm) you want an exhaust that flows ~1300cfm to keep any significant restriction at bay. This calls for a minimum of 4" exhaust from the engine all the way to the tail pipe
Velocity = Volume Flow Rate / Pipe Cross section
Velocity = 1300cfm / 0.087ft2
Velocity = ~250ft/sec
So if you are only looking to make 250whp, you should be looking at a 3" minimum exhaust pipe from the engine back.
That was easy enough, so how big do the post compressor charge pipes have to be? Well again I am just using the 400whp (525cfm) figure for this demonstration... so lets take a look.
Post turbo you want to keep flow face velocity within a certain sweet spot. That is about 200-300ft/min.
So what I chose was 2.75", which has a cross section of 0.04ft2, so 525cfm will have a face velocity of about 215ft/sec, which is acceptable.
Velocity = Volumetric Flow Rate / Pipe cross section
Velocity = 525cfm / 0.04ft2
Velocity = ~215ft/sec
Because I know it will be on the big size for 400whp, but it also needs to be able to handle my high boost tune which is moving 600whp worth of air, or about 790cfm.. and even then 790cfm / 0.041ft2 gives me a face velocity of ~325ft/sec, which again still works with the 200-300ft/sec sweet spot.
Now to make things more confusing I am also accounting for changes in temperature and pressure across the system all the way to the cylinder head.
Something peculiar happens right at the throttle body elbow that helped me keep my decision to go with 2.75" charge pipes.. my water/meth kit cools the charge so effectively it becomes denser as it enters the manifold and the "tight" piping keeps flow velocity up as it enters the manifold and runners while it is simulataneously shrinking in volume and consequently flow velocity.
To yet further complicate things my thought process also had to account for how all of this would affect the vaporization and required activation energy on my 4 different fuel constituents.
I expect the charge air to remain relatively warm since it leaves the turbo at around 260F and after the IC and piping it then enters the heat soaked manifold and cylinder head where it starts to heat up again,
This heat helps the alcohol atomize and absorb heat, yet leave enough energy in to allow the toluene and gasoline to light off with relative ease.
Because the combination of the alcohol, water, toluene and premium gas resists knock so well, I can leave the charge temps relatively warm.
So then I can be aggressive in my spark timing and fuel scheme. The cooled but still warm charge allows the fuel to spray fine and even, but the residual heat means even a weak spark can burn the whole mixture and rapidly.
.
.
Now here is the part that was kind of shocking.. for 600whp (790cfm) you want an exhaust that flows ~1300cfm to keep any significant restriction at bay. This calls for a minimum of 4" exhaust from the engine all the way to the tail pipe
Velocity = Volume Flow Rate / Pipe Cross section
Velocity = 1300cfm / 0.087ft2
Velocity = ~250ft/sec
So if you are only looking to make 250whp, you should be looking at a 3" minimum exhaust pipe from the engine back.
Last edited by DiamondStarMonsters; 05-23-2011 at 10:42 AM.
#31
05-23-2011, 10:40 AM
Join Date: Sep 2010
Location: Chicago, Illinois
Posts: 4,424
Note, all that applies to any engine and not just a boosted one. To move 250whp worth of air you WILL need a 3" pipe.
Considering you can crank a conservative 600-700whp out of a modern 427, the minimum you would want is two 3" pipes. Most of the torque is made in the primaries off the head..
Considering you can crank a conservative 600-700whp out of a modern 427, the minimum you would want is two 3" pipes. Most of the torque is made in the primaries off the head..
Last edited by DiamondStarMonsters; 05-23-2011 at 10:44 AM.
#32
05-23-2011, 10:41 AM
Unless one purposely buys a quieter exhaust, it is most likely to drone with an aftermarket exhasut anyway. The stock MUFFLER muffles the sound, remember? Even when I had my Thermal R&D Cat Back Exhaust on my 89 prelude, it droned and that was a milder exhasut note.
Also, for an N/A engine, isn't better to keep the stock piping alone and get a higher flowing muffler? You get the low end torque from the smaller piping but the high-end gain from the unrestricted muffler. Otherwise, too open of piping on an N/A would result in too much loss of torque and we know the Fit doesn't make much torque, lol.
Also, for an N/A engine, isn't better to keep the stock piping alone and get a higher flowing muffler? You get the low end torque from the smaller piping but the high-end gain from the unrestricted muffler. Otherwise, too open of piping on an N/A would result in too much loss of torque and we know the Fit doesn't make much torque, lol.
Last edited by Fitguy07; 05-23-2011 at 10:44 AM.
#35
05-23-2011, 10:52 AM
note I said a 427 only needs around 2" pipes not that it couldn't run bigger pipes as an example to people that run naturally aspirated fits with 3" pipes and they lose all the low end torque that the fits barley have to begin with.
#37
05-23-2011, 10:58 AM
What's the stock piping size on our fits anyway? 1.75 inches?
#38
05-23-2011, 11:07 AM
its closest to 1 3/4".
you have to cut the res. out too and then your left with drone.
you could add a drone pipe but then your still left with no low end.
I'm speaking of naturally aspirated fits
you have to cut the res. out too and then your left with drone.
you could add a drone pipe but then your still left with no low end.
I'm speaking of naturally aspirated fits
#39
05-23-2011, 11:08 AM
Join Date: Sep 2010
Location: Chicago, Illinois
Posts: 4,424
How right you are.
