Hot Rod Forum banner
Status
Not open for further replies.

small exhaust diameter up front and big out back??

75K views 76 replies 25 participants last post by  rifraf 
#1 ·
i was just thinking about something and let me know if im right or wrong. the general consencus seems to be that smaller exhaust pipe diameter gives better low end torque and big pipes give better high end and revving capability due to the increased flow. now why not build an exhaust system that has both? it seems that smaller tubes closer towards the motor such as the headers and first bit of pipe coming off of them is the most crutial to low end torque (smaller tube headers=more torque, etc.) i mean look at high performance motorcycles and such. they usually have a very skinny header pipe which tapers out into a large diameter muffler. so would it make sense to build an exhaust system that starts out out with say 2" or 2 1/4" piping from the headers to the mufflers then uses 2 1/2" or 3" piping for the tailpipes?? wouldnt this give you the benefit of having smaller pipes close to the motor for low end and torque and then have the bigger pipes towards the back for less high-end restriction, plus the added bonus of having a deeper sound due to the bigger tailpipes?? or am i just talking out my a** and what you would actually have is a system with flow characteristics somewhere inbetween the two??
 
#2 ·
You are confused. Smaller pipes are generally used on engines that need less air flow and are generally lower end type engines. Engines that make power consume more air and need the larger exhaust tubes. Air flow is related to engine capacity and output more than power band. You are not going to kill low end torque with larger than needed pipes, but you will kill high end power by putting a section of small pipe. The pipe will only flow as much as the smallest section.

Chris
 
#3 ·
TurboS10 said:
You are confused. Smaller pipes are generally used on engines that need less air flow and are generally lower end type engines. Engines that make power consume more air and need the larger exhaust tubes. Air flow is related to engine capacity and output more than power band. You are not going to kill low end torque with larger than needed pipes, but you will kill high end power by putting a section of small pipe. The pipe will only flow as much as the smallest section.

Chris
stepped headers work in this way to boost low end power and still maintain midrange and upper. Backpressure is important for torque production TurboS10, very important. By going with bigger tube headers and big exhaust you can loose alot of getup and go from a small motor, so saying that you are not going to kill low end torque is a lie. It may be more evident if you use smaller than needed pipes that restrict flow and kill top end, but finding the balance is the key.
 
#4 ·
ok i see what your saying, but im pretty sure im correct in saying that if you just throw some dual 3" pipes on a small block like my 283 for example that your going to kill all your low end and it will be bad for overall performance. so what if you want the better performance of the smaller pipes but the big, deep sound of large diameter pipes. would there be anything wrong with using smaller pipes up front and large tailpies after the mufflers so you get the sound of big pipes without the performance loss that would occur with slapping them on a smaller engine???
 
#5 ·
Really Dubz.....got any dyno sheets on that? From everything I have seen, the step headers have been proven to be pretty much worthless. I have also never seen any information that supports the fact that large pipes will "kill" power. I have seen dyno sheets that do prove that a small amount of backpressure will produce favorable mid range torque advantages. When I say small, we are talking less than 5 percent. Of course mufflers on 3 inch pipes will usually provide a small amount of backpressure just because of the slowed flow.

So, I would like some supporting data(read dyno sheets) that large pipes will "KILL" low end torque. I did not say it would not be effected. Hot Rod magazine did a series of small block dyno pulls to test open, straight, H pipe, and cross over a little while back. They used 3 inch pipe on a fairly mild build, with good results. This or another also tested the step headers with no advantage over a header of the same size as the smallest tube. The theory is that the step size increases scavenging ability of the headers if I remember correctly. This would supposedly help in the top end of the power range, but the dyno did not support this.

I guess we should define "kill" here, huh.....


Chris
 
#7 ·
TurboS10 said:
Really Dubz.....got any dyno sheets on that? From everything I have seen, the step headers have been proven to be pretty much worthless. I have also never seen any information that supports the fact that large pipes will "kill" power. I have seen dyno sheets that do prove that a small amount of backpressure will produce favorable mid range torque advantages. When I say small, we are talking less than 5 percent. Of course mufflers on 3 inch pipes will usually provide a small amount of backpressure just because of the slowed flow.

So, I would like some supporting data(read dyno sheets) that large pipes will "KILL" low end torque. I did not say it would not be effected. Hot Rod magazine did a series of small block dyno pulls to test open, straight, H pipe, and cross over a little while back. They used 3 inch pipe on a fairly mild build, with good results. This or another also tested the step headers with no advantage over a header of the same size as the smallest tube. The theory is that the step size increases scavenging ability of the headers if I remember correctly. This would supposedly help in the top end of the power range, but the dyno did not support this.

I guess we should define "kill" here, huh.....
Chris
Must have hit a sore spot, you got pretty defensive....however if you ask just about any rodder they will tell you that big pipes on a small stock engine will KILL power down low.

do you have any dyno sheets to support your side of the argument??

And you said "small amount of backpressure will produce favorable mid range torque advantages", but we were talking about low end, not midrange.

Also you mentioned that the sb responded well to 3" on a farily mild build. What were the results?? more peak hp? (expected) or more low end torque? (or do you know)

The race boys have been running tuned step headers, and the idea behind them is proven. Off the shelf stepped headers may not boost anything however (such as Hedmans tork-step) because thier not TUNED to the exact engine and rpm range, althouh since you mention hotrod look in March 2002 in the 500lb-ft article. "....we tried a swap to regular 1 5/8" headers and ended up gaining a few horsepower while losing a few ft-lb of torque" which if you think about a graph of torque and hp, meens that if you gain torque and lose hp it must make the torque down low.

Dyno proven by a NHRA/IHRA/SRA member and licensed Superstock driver "We did some header testing over the weekend on the dyno. I'll get into specifics later.....1 3/4 lost 15 ft lbs of torque and 10 HP over 1 5/8 and that's on a 9000 RPM engine! A good step header will always out perform any single diameter tube header on a race engine. (not top fuel or big blown stuff you smart a$$es lol)"

Exhast backpressure changes the torque curve, lots of backpressure gives lots of low end torque, and no backpressure (open pipes) give great mid range and high range power (moves the torque band higher in rpms).

from another thread on another forum "A 306 with stock heads, street gears, in a heavy car with a 4 spd will lose some valuable lowend torque with mandrel 2 1/2 pipes, but if you have future head and stroker plans for the motor, go ahead and do it so you won't have to pay again later. Otherwise, a standard 2 1/4" job will be a big improvement. I'm still running 2 1/4" on my little 331 and it's nice and torquey!"

That is with a difference between a cross section of 4.9 sq inches and 4.0 sq inches, if you were to put a set of 3" pipes (7.07 sq inches) you would loose alot of the down low torque and on a small motor that isn't good.

It all depends on the application, sure if you have a BBC such as a 502 you can stand to loose 20-30 ft lbs by using an exhaust that gives you more peak hp, but if you are running something much smaller, say a 289 that kind of loss would change alot.
 
#8 ·
Most oem stuff comes with smaller tailpipe than the header pipe.

I have always used the same size all the way , with good result.

Dubz, telling a member on this board that his opinion is a lie is a little strong. I think that would make a sore spot for me.

Troy

__________________
69 ss rs full custom camaro 98 ISCA grandchampion
69 ss rs bb camaro wifes driver
66 Elcamino 350/all dz parts,ac,windows,loaded,my driver
69 ss chevelle bb conv.fresh frame off
26 T sedan street rod
 
#9 ·
troy-curt said:
Most oem stuff comes with smaller tailpipe than the header pipe.

I have always used the same size all the way , with good result.

Dubz, telling a member on this board that his opinion is a lie is a little strong. I think that would make a sore spot for me.

Troy
I re-read that and it does sound a little strong, but to me it wasn't an opinion type question, it was a fact based question (where there is a right and a wrong)

Sorry Turbo :(
 
#10 ·
Being a king of low budget-- low buck, I have had numerous cars that prove this backpressure issue in real world situations with seat of the pants information. ( I don't have any Dyno proof and probably will never be able to "dyno" anything!) But, I did have a 455" buick electra that the exhaust got torn off of (gravel road racin') With only two feet of lead pipe on the car, it was no longer the tire shredding monster it was with full exhaust and actually labored to pull away from a dead stop--- replaced the exhaust--TaDah!--back came the lowend torque! Another time, I put a very mild 305" in a 65 chevy pickup but I ran out of money so I welded the 305's leadpipe to the 6cyl. exhaust (1-3/4, 2"?). WOW! gobs of lowend power! A month or so later, when I had the money, I had a complete dual exhaust put on the truck (2-1/4") Guess what? lowend torque was nowhere near what it had been with the single system! I have used 2-1/2" ( 18"long ) collectors at the dragstrip on a small block car and picked up a tenth over open headers! Anyway, my answer to the question would be, on your 283, I would run a 2-1/4" dual exhaust through the mufflers and then step up on the tailpipes if you want the big sound and look!
 
#11 · (Edited)
DoubleVision said:
I remember years ago on a subject like this, it was said that exhaust gasses cool the further back they travel in the pipe, so the tail pipe section or sections after the muffler could be slightly smaller in diameter.
Very true, but you still have to be carful IMHO. Really depends on how far back you want to downsize.

Dubz said:
Must have hit a sore spot, you got pretty defensive....however if you ask just about any rodder they will tell you that big pipes on a small stock engine will KILL power down low.
It was not a sore spot, I just dont like being called a liar. Most dont......appology accepted. I Like I said, I guess you have to define kill. Is it 5% or 25%?

I dont doubt that alot of rodders agree, but many hotorodders also think the chevy 302 was the hottest engine ever built. Exhaust upgrades are also almost always the first and most benifitial upgrades(more later) My experience has been the same. Typically .1-.3 tenths better open than when I ran 2.5 inch exhaust and super turbo mufflers on my 57. Have not run the same setup since I installed 3 inch flowmasters and H pipe. I will add that you can not just uncork the headers and not retune the engine. Typically fatten it a bit on the primaries.

Dubz said:
do you have any dyno sheets to support your side of the argument??
Only the HRM article that dispelled the header theory. I have a hard time believing they would run 3 inch pipes if there was no advantage. Most of the time those guys do their homework.

We actually upgraded from 2.25 inch duals and turbo mufflers to 3 inch and dynomax race mufflers with H pipe on my brothers 383 powered Nova. It is kindof hard to tell how much it gained since it did and still does roast the tires in anything other than high gear over 50 mph....at the burp of the throttle. What it did help alot was top end. It is pushing 450-500 ponie range and was seeing serious restriction. He is running 1.75 primary headers BTW.

Dubz said:
And you said "small amount of backpressure will produce favorable mid range torque advantages", but we were talking about low end, not midrange.
Okay, exactly how low? I guess I have never delt with a bone stock engine other than my daily driver 2000 Chevy. I upgraded to 3 inch single over 2.5 and changed to dynomax race muffler and it picked up considerably through the whole range by the seat-of-the-pants-ometer. I always run at least a little stall in a hotrod and really dont need anything less than 2000 RPM so I have no experience there. The area under the curve at that point is so little it really does not matter IMO. What really counts is how much total work you are getting under the curve. Most of this is mid to top end which benifit from large diameters.


Dubz said:
Also you mentioned that the sb responded well to 3" on a farily mild build. What were the results?? more peak hp? (expected) or more low end torque? (or do you know)
Will have to try to look it up......have the last twleve or so years of HRM.

Dubz said:
The race boys have been running tuned step headers, and the idea behind them is proven. Off the shelf stepped headers may not boost anything however (such as Hedmans tork-step) because thier not TUNED to the exact engine and rpm range, althouh since you mention hotrod look in March 2002 in the 500lb-ft article. "....we tried a swap to regular 1 5/8" headers and ended up gaining a few horsepower while losing a few ft-lb of torque" which if you think about a graph of torque and hp, meens that if you gain torque and lose hp it must make the torque down low.
Well all the "race boys" I know and run around with run regular 1.75 to 2.25 inch header tubes. The 1.75 for NA SB and larger for real nasty SB and BB. The idea is that hot expanding gases will always move to an area of lower temp and pressure. The step provides a lower pressure area in the larger tube. The idea is that is sucks the gas out of the chamber inproving scavenging. This is a good theory, but what hurts it is the pumping losses if the small tube section becomes a restriction. I dont doubt that when tuned on a race engine there are benifits, but they aint runnin' 1.5 inch primaries unless it is a small cid. As for the curve, all it means is it made more torque somewhere below 5252 RPM where the curves always cross and are equal. They are usually talking peak torque which is somewhere in the last 1/2 of the curve before the curves cross. This is midrange to me.


Dubz said:
Dyno proven by a NHRA/IHRA/SRA member and licensed Superstock driver "We did some header testing over the weekend on the dyno. I'll get into specifics later.....1 3/4 lost 15 ft lbs of torque and 10 HP over 1 5/8 and that's on a 9000 RPM engine! A good step header will always out perform any single diameter tube header on a race engine. (not top fuel or big blown stuff you smart a$$es lol)".
If that is truely a 9000 RPM engine, it aint no big block and it is probably an itty bitty smallblock or an import. If we are talking import, we are talking turbocharged. At this point we can throw this conversation out the window because it all changes.


Dubz said:
from another thread on another forum "A 306 with stock heads, street gears, in a heavy car with a 4 spd will lose some valuable lowend torque with mandrel 2 1/2 pipes, but if you have future head and stroker plans for the motor, go ahead and do it so you won't have to pay again later. Otherwise, a standard 2 1/4" job will be a big improvement. I'm still running 2 1/4" on my little 331 and it's nice and torquey!"
Opinion......



Dubz said:
It all depends on the application, sure if you have a BBC such as a 502 you can stand to loose 20-30 ft lbs by using an exhaust that gives you more peak hp, but if you are running something much smaller, say a 289 that kind of loss would change alot.
Obviously engine size has alot to do with this. You would never run smaller than 1.75 on a BB I would hope, and usually it is larger. 1.5 is plenty good on a 289 unless it is a real screamer.

Point my original post was that his idea would just not work. He may as well run small the whole way. One thing that I have heard but not seen proven is that if the pipe is severly oversized for the application, you to not get a laminar(believe that is the right word), but rather a sort of tumble effect. Smaller pipes keep velocity high enough to keep this from happening. Point is that small and large are all relaitive to displacent, rpm range and VE which all effect flow characteristics.

I guess, it is also relative to what low end is for an engine. For a race engine, below 5K is usually not important and this leads to the gargantuous headers. For a rock crawler, where you need 500-1500 to be optimized the little pipes have a place. For the average 2000-6000 RPM street bruiser, I like big pipe and header tubes without going overboard. I believe you get the most usuable power through the range. I will point out again, a simple swap without retuning is not a good indicator.

Chris
 
#12 ·
Before I put the new exhaust system on my 85' blazer with a 355 dynomax 1 5/8 headers, 268XE comp, I ran open headers for a day just to see what it would be like. It was loud but the low end was absolutely horrible, and the top end also seemed to lack. I dont know if running open headers is even near the same as running too large diameter of pipe, but I thought I would mention it anyway. The 2.25 inch dual with H-pipe really brought up the power by alot.
 
#13 ·
I just read a book that outlined the advantages of stepped headers, or even stepped exhaust systems. They gave percentages for length that each step should be of your total header length should be. Lengthening certain steps affects different RPM ranges, enabling tuning. I wish I remembered more, but the book was just loaned to me for a while. If I get it, I'll try to retain a bit more of that. My bad:rolleyes:
 
#14 ·
TurboS10 said:
If that is truely a 9000 RPM engine, it aint no big block and it is probably an itty bitty smallblock or an import. If we are talking import, we are talking turbocharged. At this point we can throw this conversation out the window because it all changes.
a 289 or 302 sbf
 
#15 ·
so if its true that hot expanding exhaust gasses will always go to the place of lower temperature and pressure, wouldnt using small pipes from the header-mufflers and big tailpipes "suck" the exhaust away from the motor better than one smaller size all the way through?? the bigger tailpies are areas of lower pressure and temperature are so wouldnt the exhaust gasses rush to this area more??
 
#16 ·
TurboS10 said:
For the average 2000-6000 RPM street bruiser, I like big pipe and header tubes without going overboard. I believe you get the most usuable power through the range. I will point out again, a simple swap without retuning is not a good indicator.
Chris
But as you are saying there is an overboard where you will gain no more power, and may lose low end (on a street bruiser 1000-3000) which with street gearing will make the car a dog on the low end. Right?
 
#17 ·
I don't know too much about exhaust.
But I did know when I had an exhaust problem.
I put on a new intake and my truck started overheating at high rpm's.
After a few checks I determined that my factory exhaust manifolds were the problem.
I put on a set of hooker comp. headers... long tube style... I can't remember what that tube diameter size was... but the collecter was 2 1/2 inches...
I couldn't afford a total exaust (pipes, mufflers, hangers, etc.) on it as I had spent most of my money on the intake and carb. So I just got 2 1/4 reducers for it and welded my old glasspacks (18 inches long, 2 1/4 inch internal diameter) right to the reducer. My exhaust is basically nothing but headers with glasspacks hanging off of the ends. no pipes. at all.
This is on a 350 in a 72 chevy truck.
not only does this setup sound great... I have actually popped my tire burning out with this setup and have noticed GAINS in torque all the way from stopsign to redline.
I don't know how or why it works... I just know that it does and since it does I've left it alone for over a year now.
 
#18 ·
Basicly from what I've read and seen you need to match your exast size and length to the motor out put for best results.
You need to have a suficient scavenge speed coming out of each header pipe into the colector in order for each cylinder to help suck the exhast out of the next one. To big of any pipe and you have no speed. To small and the exhast is restricted.
4 banger racing bikes use this perfectly. Thats why racing bikes only have one muffler/baffle and not 4. Or even 4 open headers.
Thats also why 2 stroke engines respond so well to a simple exhast change. They tune the size and shape of the expantion chamber.
There are other ways(atmospheric reverberation) and reasons to tune an exhast and intake to your motor but its late and takes too long to explain right now.
But wasn't there a factory musle car that used this perfectly to acheive 115% of the incoming air/fuel mix in each cylinder instead of the normal some what less than 100%. Though it only happened at a single small RPM range.
In the 50's Mercedes Benz even worked out a way for your gas peddle to change the exhast leagth to match the RPM. Thearby trying to make the best power band over the longest range. It worked but the exhast leaked or got stuck.
 
#19 ·
Dubz, there is always an overboard, or at least a point of diminshing returns. Since I have not seen any dyno test, I will just say that my opinion is that there will be some losses in the low end if pipe size in increased, but I do not believe it will be significant enough to justify a high restriction exhaust. While larger tubing may hurt 3000 and below, it will help on top. Really depends on the combo. IMO, top end is more usable since you are not having to fight tire spin. Roasting the tires does not make a car fast, ya know.

Smlblks10, from what I have read the scavenging is most benifitial in the header tubes and right after. It seems it is more benifitial when the EG is very hot and at high velocity, but this is just what I have gathered from reading so dont hold me to it. I really dont think there would be any performance gained from running a larger pipe from the muffler back. When the exhaust gas slows in the muffler it is going to loose some heat and really should need less volume in the pipe since it will be at a lower volume.

Another point dealing with tuning and backpressure. When running open headers, an extension tube should be used to extend the header collector. You can use paint to check the point where the EG gets cool enough to stop burning the paint. At this point, you can chop the pipe off. This is suppose to be the ulitmate tune on open exhaust. I would venture a guess that this is due to the added back pressure with the added pipe length. Same paint trick can be used to find the best crossover pipe location on duals.
 
#20 ·
This has been covered in great detail on this board. I did a quick search and came up with the following links. In summary, there is no 'best' header/exhaust system for every application. Engine design is a compromise - a header that works best in normal driving would be a bad choice for a high RPM racing engine. Peak torque is highly dependent on header length. The longer the primary header pipe, the lower the peak torque RPM. Detroit's compromise is to use a header log that has no primary pipes so doesn't have as high a torque as it could have but also doesn't 'peakie' torque characteristics.

http://hotrodders.com/showthread.php?s=&threadid=5427&highlight=exhaust

http://hotrodders.com/showthread.php?s=&threadid=4781&highlight=header

http://hotrodders.com/showthread.php?s=&threadid=4523&highlight=header
 
#21 ·
Some interesting info Willys. Basically, looks like backpressure is bad all around.....hmmmm sounds familiar. What the question comes down to is do you want to optimize headers and exhaust for lower or higher end velocity. Low end velocity can be achieved with the smaller tubes. High end they become restrictive and cause backpressure problems.

I have to disagree a little to some of the other threads. There are alot of aftermarket headers that achieve very close to equal tube length. The afterburner headers actually attempt to also add a longer tube for what they explain to be an uneven pulse since each bank does fire at an even interval. Take 18436572, the most widley memorized order on the planet;). If you look, you can see how equal length would not give an equal scavenging pulse for all cylinders since 84 fire together, then one cylinder later 6, and two cylinders later 2. Properly designed uneven length could help achieve pulses that correspond to the uneven firing order.

Just some food for thought. Shoot it full of holes guys:boxing:

Chris
 
#22 ·
we should know better by now than to talk in terms of absolutes when it comes to motors.

Bigger carb is not always better.

Bigger cam is not always better

Bigger valves and runners are not always better...

and bigger exhaust is not always better either.

IMO the more you build a motor up, the more exact you have to be about your parts due to cam overlap. My professor explained it this way in my auto-restoration class:

Bigger cams move columns of air and fuel through your engine (a reason you should always match your intake to your cam...), a bigger cam moves a bigger column, thats why it moves the RPM range of the motor up, because the air has to be moving that much faster to get that full column into the motor. A well designed exhaust system (which on flat crankshafts can be tuned ex. Italian sports cars use this method) works with the cam using a scavenging effect. The gas expansion from one header tube creates a pulling or low pressure area on the next opening valve and actually sucks the exhaust out of the port and because of the overlap (both intake and exhaust valves open at once) that much intake air is sucked into the chamber as well. What a great system eh?

Furthermore, on these "tuned" flat crank engines, a perfect muffler (exactly 20x the size of the combustion chamber) is used and creates a sound pulse that travels up the exhaust, back to the header and helps create a low pressure area that pulls the gasses out of the chamber. The "tuning" involves positioning all parts of the exhaust perfectly so that the sound pulse hits the port at the desired instant. That must be why these Italian cars cost so much! LOL

K
 
#23 ·
weight matters, so does driving in traffic

Vehicle weight plays a big part also. Optimum performance for pipe size varies with weight of the vehicle, as it does with torque converters.

The idea is to expel as must of the gas as possible while still retaining back pressure for low end torque and the scavenging effect of from valve timing overlap. Hence, cam spec come into play when choosing the best pipe size.

The hotter the gasses, the faster they go: its physics.

So if you have coated headers, the gasses stay hotter. If you wrap them => even hotter.

Small primaries stepped out to *slightly* larger pipes create a "restirctor plate" type effect that keeps the gasses from going back up the tube, as *easily*.

Ridiculously HUGE pipes that cool off easily, keep a low pressure environment that acts like a solid wall to push through. The gasses are NOT HOT ENOUGH TO GET OUT OF THE PIPES.

Race cars are different. They spend most of there lives above 5000 rpm.

The same goes for Fart boxes on Turbo, they only have power in the high range, but they will NEVER need dual 3" exhaust on a <2 liter engine.
 
#24 ·
Yes, I have heard all of the stories on how back-pressure is desirable in certain situations but none make sense to my pea-brain. Also, the organ pipe theory used in header primary-pipe design ignores effects pipe interference. Assuming the collector size is reasonably larger than the primary tubes, each tube acts independently from its neighbors. The main advantage gained in equal length, independent primary header tubes is from the strong negative pressure pulse that is reflected from the tube end when the strong positive pressure pulse form the exhaust valve reaches the collector. Other pulses from other header tubes are of much smaller magnitude in the tube of interest and can be ignored. Thus tuning length is very easy to determine once you have an estimate of the speed of sound in the hot gasses. A useful equation is

L = 120V/rpm

For
L = pipe length, less port length in head, in inches

and

V = velocity of sound in hot gasses. Values of 1300ft/sec to 1700 ft/sec are common.

Using V = 1700ft/sec the equations simplifies to

L = 204,000/rpm.

There have been various permutations on this basic design like tri-Y headers, stepped tubing size, etc. Each takes advantage of modifying the pressure pulse arrival time at the instant the exhaust valve closes to achieve a scavenging/ higher volumetric efficiency/ more torque result. The good is that you can achieve a very significant torque increase at the design rpm. The bad is that you likely will also achieve less torque at other RPMs.

There are other design theories like the Helmholtz resonator which are useful in designing systems with more than one degree of freedom than a single pipe/cylinder, i.e., Tri-Y.

Test show that smaller tube diameter has no effect on tuning speed but the smaller the tube, the stronger the signal. Conversely, the smaller the tube the more bad pressure loss there is. Tubing bends, within reason, have no effect on header performance.
 
#25 ·
Re: weight matters, so does driving in traffic

2DoorCaprice said:

The same goes for Fart boxes on Turbo, they only have power in the high range, but they will NEVER need dual 3" exhaust on a <2 liter engine.
I am curious of the fart boxes you speak of. New term to me;) Are you talking intake here? Or, large pipe after the turbo to take the "twist" out so the flow can become linear? If the later, this is a very viable setup. General rule of thumb is put as large a downpipe as will fit on a turbo. Should also be as open as possible. I have read on a turbo engine you can loose 10-20 percent by using a chambered muffler(flowmaster) over straight(dynomax) through. Same for turbo mufflers.

Chris
 
#26 ·
so if there is no performance gain by using bigger tailpipes than exhaust pipes (headers-mufflers), is there any performance LOSS? i mean pretty much everybody can agree that bigger diameter pipes make your motor sound better and lots of people prefer the look of big pipes coming out the back (me included) so is there any reason why it is NOT a good idea to use, say, 2 1/4" pipes all the way back to the mufflers and then use maybe 2 1/2" pipes for the tailpipes for the look and sound?? it should just flow very similar to a system thats 2 1/4" all the way through since that is the smallest pipe being used, correct??
 
Status
Not open for further replies.
You have insufficient privileges to reply here.
Top