fabricating a decent exhaust



fabricating a decent exhaust

Postby grumpyvette » October 8th, 2008, 8:47 am

face it, many, maybe, most muffler shops want you in and out of thier bays as fast as possiable and want to use the least expensive components they can find , and want to take the least effort and time they can, yet derive the most proffit, from the work. you can totally avoid that by either buying top quality components and paying big bucks, or...if your budgets like mine....
if something BREAKS , well,thats a P.I.T.A., and probably a badly designed or improperly installed component, but thats what WELDERS are designed for.....learn to weld and things like that are at most a minor repair that will usually take well under 30 minutes and its almost certain that you can put some thought into the repair and make it darn near "bullet proof"
and very unlikely to re-occure
no part is immune from a bad installation.
in fact! once you learn to weld and you can weld up a totally custom exhaust that will exactly match your design and application goals for far less than you can buy one for, in cheap aluminized steel or the far better stainless steel
put some thought into the system design, having the correct diam exhaust pipes and an (X) pipe connecting the two sides as close to the engines as space under the car allows helps performance,having the muffler as far rear as possible has both performance and sound benefits. Exhaust gasses will naturally slow down cool and expand and the individual exhaust pulse strength dissipates, the further it travels through a pipe, also the extra length will help dissipate sound waves , and smooth the flow making the muffler theoretically less intrusive to exhaust flow and quieter. minimizing back pressure past the header collectors and (X) pipe should be a major factor in your exhaust system design calculations as that will tend to increase exhaust scavenging efficiency if the headers are correctly designed.
FAILURE TO READ THE LINKS AND SUB LINKS SIGNIFICANTLY REDUCES THE USEFUL INFO YOU HAVE ACCESS TOO!
http://store.summitracing.com/egnsearch.asp?Ntk=KeywordSearch&DDS=1&Ntt=exhaust+kit&searchinresults=false&N=700+115&y=6&x=32

http://www.jegs.com/webapp/wcs/stores/servlet/category_10001_10002_11525_-1_10245

http://www.magnaflow.com/02product/universalsatinxl.asp

http://www.flowmastermufflers.com/mufflers.html

viewtopic.php?f=32&t=1174&p=2404#p2404

http://www.superchevy.com/technical/eng ... index.html

http://www.borla.com/products/universal.aspx

http://home.flash.net/~ivc1/cobra/xpipes.html

you can build your own stainless steel exhaust system and personally install it and its very unlikely to cost nearly what youll pay a muffler shop, BUT USE A MINIMUM 16GA 18 GA is too THIN, FOR STAINLESS HEADERS OR EXHAUST PIPE, AND DON,T FORGET TO PURGE THE BACK GAS WHEN WELDING ,and if you shop for components carefully youll find that a stainless exhaust will cost only slightly more than the muffler shop charges for inferior aluminized steel
if your going thru the work do it correctly, buy and install decent components so your not back doing it again in a year or so!

careful measurement and planing, and component sellection, will help a great deal in keeping costs low!

BUT THEN I ONLY BUY AND INSTALL STAINLESS COMPONENTS IF GIVEN AN OPTION, INSTALL THEM MYSELF, AND CAN,T REMEMBER HAVING PROBLEMS INSTALLING OR HAVING A COMPONENT FAIL IF ITS PROPERLY INSTALLED...QUALITY EXHAUST HANGERS DON,T GENERALLY FAIL AND QUALITY WELDS DON,T GENERALLY BREAK, AND IF YOU INSTALL IN CORRECTLY YOURSELF AND CAN WELD YOULL SAVE MONEY AND HAVE THE EQUIPMENT AND SKILL TO FIX IT IN THE UNLIKELY EVENT IT DID BREAK:thumbsup:

JUST ONE MORE REASON TO LEARN TO WELD AND HAVE ACCESS TO A GOOD MIG,TIG, OR OXY-ACETOLENE TORCH:D :thumbsup:

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theres plenty of fluid dynamics math and research out there to show that the distances the exhaust travels between exhaust pulses and the diam. and length are easily calculated, and past that length the second previous pulse has little effect compared to the current and previous pulse energy and reflective wave
and lets not forget the cam timing displacement and intake port all effect the cylinder scavaging the headers can effectively provide also

http://www.engr.colostate.edu/~allan/fluids/page7/PipeLength/pipe.html

http://www.rbracing-rsr.com/runnertorquecalc.html

http://victorylibrary.com/mopar/header-tech-c.htm

http://www.headerdesign.com/

http://www.pontiacracing.net/js_header_length1.htm

http://www.slowgt.com/Calc2.htm#Header

example , my 383 vette has a cam with exhaust cam timing that opens at 83degs bbdc, thats 97 degs atdc, http://www.cranecams.com/?show=browseParts&action=partSpec&partNumber=119661&lvl=2&prt=5
Bore: (Inches) 4.03"<BR>Exhaust Valve Opening Point: (Degrees ATDC) 97 degs
Peak Power RPM: 5500rpm Calculated information appears below
Header Pipe Diameter: (Inches) 1.84"<
Header Pipe Length: (Inches) 37.65
Collector Diameter: (Inches) 3.5
Collector Length: (Inches) 18.82


so ideally the (X) is placed at that point to maximize scavaging but thats not always possiable due to clearance, and if you choose to place an (H) just before the mufflers its mostly to reduce resonance or noise not increase scavaging but it tends to reduce the restriction to flow
most guys I talk and deal with,seem to think that slapping a set of headers on thier car is all thats required to boost performance....ANY HEADERS! ...and they fail to realize that both the header design and the exhaust system behind them require a good deal of thought if you want the maximum benefits, and that simply hooking a restrictive exhaust system to the collectors on the best headers will negate most of thier potential benefits.
most commercial headers are designed mostly for ease of manufacturing and ease of installation,little thought goes into maximizing the cylinder scavaging which is thier main function.
your fooling yourself if you think headers will provide a big boost in hp/tq without the low restriction exhaust behind them,and in most cases that requires a larger dia. exhaust system and adding an (X) to the system and extending the header collectors at thier full dia. up till at least the exit of the (X) so the twin exhaust pipes cross sectional area can provide that reduced restriction to flow, rather than the reducers many guys install to the collector exits to adapt them to the stock exhaust system

example of a well laid out exhaust (MELROSE)
Image

but even that system could be hurt if you slap restrictive mufflers on it
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: fabricating a decent exhaust

Postby grumpyvette » October 26th, 2008, 2:17 pm

http://www.sandersonheaders.com/index.p ... h=21_23_35

http://www.holley.com/index.asp?division=Hooker

http://www.hedman.com/

http://www.melroseheaders.com/

http://store.racing-solutions.org/

http://www.mez.co.uk/mezporting/exhaust_length.html

viewtopic.php?f=56&t=2106&p=5659#p5659

the ideal exhaust on any corvette or muscle car, will have less than 1 psi of back pressure at peak power rpms and headers designed to match the engines power curve.
In most cases commercial headers are designed to be easy to manufacture, cheap to produce and simple to install with very little thought wasted on maximizing power or designing a header that maximizes the engine torque in its usually power band.
keep in mind the OEM engineers are more concerned with low noise levels and maximizing power in the idle to 3500 rpm band where most cars operate 90% of the time.
upgrading to a dual 3" exhaust with an (X) pipe and low restriction mufflers matched to headers calculated to match your intended power band could easily boost net power 30 plus hp
Here are some numbers assuming exhaust behaves as an ideal gas and the pressure inside an exhaust system is 1 atmosphere due to it having an open end.


degrees F-------gas volume (1 mol)
100F-------------25.51L
300F-------------34.63L
600F-------------48.32L

Exhaust gasses at 600F are almost double the volume as they cool and reach the tailpipe. If exhaust efficiency is to keep velocity constant, wouldn't it not make sense to keep the relative diameter of the pipe consistent with temperature of the exhaust in the system?
Why aren't racing exhausts pipes tapered to maintain this difference in volume?
WELL ONE REASON is that on a race engine the whole exhaust length is not used or needed to maximize low rpm torque, and at higher rpms a tuned header collector more closely matches the intended power curve, thus as long as the exhaust is LESS restrictive past the header collector its not hurting the power curve, so its maintained at the collector exit diameter , or routed to a (X) pipe to further reduce the restriction, remember the exhaust is in pulsed spaced 90 degrees apart not a solid consistent flow.


READ THIS THREAD AND SUB LINKS

viewtopic.php?f=56&t=1503

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TAKE the effort to calculate what the correct type/size headers will be

http://www.wallaceracing.com/header_length.php

http://www.pontiacracing.net/js_header_length1.htm

http://www.bgsoflex.com/cgi-bin/progaut ... 3&rpm=6300.

http://www.mk5cortinaestate.co.uk/calculator5.php



threads and sub links you should read thru
viewtopic.php?f=56&t=495

viewtopic.php?f=56&t=1166

viewtopic.php?f=56&t=961

viewtopic.php?f=56&t=185

viewtopic.php?f=56&t=2916
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: fabricating a decent exhaust

Postby grumpyvette » February 1st, 2009, 1:43 pm

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: fabricating a decent exhaust

Postby grumpyvette » February 1st, 2009, 1:50 pm

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: fabricating a decent exhaust

Postby grumpyvette » August 17th, 2009, 8:42 am

viewtopic.php?f=79&t=497

viewtopic.php?f=56&t=495

viewtopic.php?f=56&t=1730

read thru ALL the sub linked info in this thread, and ITS SUB LINKED THREADS
its not at all rare for a swap from 2.5"-to-3" exhaust on a sbc or mild bbc or from 3"-to-3.5" on a radical big block to add 5-15hp, depending on the restriction that was removed behind the collectors or exhaust manifolds, back pressure reduces the effectiveness of the exhaust cylinder scavenging, and once you tune the engine to take full advantage of that reduced restriction and better cylinder scavenging factor you get the full benefits that the reduced back pressure tends to provide.
keep in mind the lower rpm TORQUE LOSS thats occasionally reported is FREQUENTLY a tuning issue as the more effective scavenging tends to lean out the effective fuel/air ratio
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: fabricating a decent exhaust

Postby grumpyvette » October 29th, 2011, 1:51 pm

I had a recent discussion over the phone with one of the guys on the site that has a 460 ford installed in a COBRA kit car with a ford 4 speed manual transmission and he was telling me the car runs great up to about 4000rpm then it just noses over on power , he was using factory exhaust manifolds not headers and I know hes running a decent cam and intake, so I had him check the ignition timing, advance curve, fuel pressure, look at the spark plug condition and check the compression, vacuum readings plug wire resistance and a dozen other factors exhaust. the result was that the exhaust he had installed was very restrictive because like most of us he was on a tight budget, and the correct side pipe exhaust was going to cost something like $2K so he temporarily installed a fabricated exhaust, using two 2.5" tail pipes in a true dual exhaust, under the car with two rather restrictive mufflers that when he tested showed he had 7-8 psi of back pressure at 5000rpm.
needless to say here hes researching options for headers and side exhaust.
the point here is that even a really nice potentially powerful engine that should easily exceed 400 plus hp can be down significantly in power if the exhaust restricts flow, and cylinder fill efficiency.
this is a reasonably common problem, guys install killer cams, big heads, good intakes etc. and forget that everything that goes in needs to exit AFTER its heated and expands a great deal, yet they still seem to think that the marginal stock or similar size fabricated exhaust will handle a 25%-50%-or even 100% increase in potential power that the other parts potentially allow??

http://www.hotrod.com/howto/hdrp_0511_f ... ewall.html

http://www.cobracountry.com/home2.html

http://www.hoverd.org/Tim/links_frames.html

http://www.erareplicas.com/427/427sc.htm


http://jwane.net/Driving%20A%20Cobra/Dr ... plica.html

Image
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: fabricating a decent exhaust

Postby Indycars » October 29th, 2011, 2:24 pm


Why not simplify the exhaust system by going to ONE larger pipe after the crossover point. Fabrication would be simpler working with only one pipe. You would only have to purchase one muffler, but are there larger sizes available ???

ExhaustPipeSizeEquivalent.jpg

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Re: fabricating a decent exhaust

Postby grumpyvette » October 29th, 2011, 3:34 pm

Ii,m sure he will read this, thread and consider that option but I,m also sure he would rather NOT be identified and thats his choice of course
but from what he previously said Id be surprised if he went with anything other than a true side exhaust and full length header combo, installed on that cobra kit car
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: fabricating a decent exhaust

Postby grumpyvette » February 21st, 2013, 1:44 pm

IF you shop carefully youll find you have dozens of options for a STAINLESS 3" exhaust for your muscle car, don,t just jump on the first exhaust you find, actually compare what you get and cost and try to look over instructions and pictures
remember stainless costs more up front but easily last 3-4 times as long.
and your never going to get a true high performance car to perform to its full potential with out a decent exhaust
If your swapping to a larger 3" exhaust with an (X) pipe, it has or will more than likely reduced your engines exhaust restriction this tends to lean out the fuel/air ratio, which can reduce torque ESPECIALLY if you still have shorty stock exhaust manifolds that don,t always scavenge the cylinders correctly at all rpm levels, you can generally get back the torque and add upper and mid rpm power with correctly designed long tube headers, but most engines with factory injectors and tuning run rather lean for passing emission testing. and most original cams are more concerned with mileage and drive-ability than torque and peak power.
every change you make effects the way the car runs, if you reduce the exhaust restriction it potentially allows the car to make noticeably more hp, but REQUIRES there engines are re-tuned to match the new conditions and having a longer duration cam and larger injectors , or increased carburetor jet sizes and long tube headers certainly helps take advantage of the lower exhaust flow restriction.


http://www.highperformancepontiac.com/f ... ntiac_gto/

http://www.magnaflow.com/07techtips/pdfs/15898.pdf
http://static.summitracing.com/global/i ... 15898_.pdf
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http://www.summitracing.com/parts/pye-s ... /model/gto
Image
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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: fabricating a decent exhaust

Postby bytor » February 21st, 2013, 2:29 pm

I went the Pype's route with my setup and was very pleased with the quality and fit.
http://www.pysales.com/iw_products.m4p.pvx?;item?ItemCode=SCC12R?company=ppe

Here's a few pics.
IMG_0745.JPG

IMG_0746.JPG

IMG_0747.JPG

IMG_0748.JPG

IMG_0764.JPG


The only work I had the exhaust shop do for me is weld up up 'S' pipes with the flex joints and reducers.
IMG_0763.JPG
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My 383 build photos
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Re: fabricating a decent exhaust

Postby Michaeljohn » March 29th, 2013, 6:07 am

was very pleased with the quality and fit.



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Re: fabricating a decent exhaust

Postby grumpyvette » December 22nd, 2013, 9:41 pm

I'm always rather amazed at the total reluctance of many guys to do anything too the car they own ,that didn,t come in a pre-cut kit ,labeled indicating it a direct fit and interchangeable with stock components, thats been listed for and specifically designed specifically for ,their particular car, and shown that way in some catalog.!
I had one guy recently who found that a particular brand of muffler no longer carried the particular part number that was listed as fitting his car, the idea of measuring carefully and selecting a generic or even the exact same brand of muffler and custom fitting it where the older muffler was, just never entered his mind, it was as if , the mere idea that the particular muffler part number, in a catalog didn,t show it was listed too fit his particular car meant that there was no possibility of it ever being fitted or functioning, on his car, and that simply having that particular part number listed was all that was required to make it fit!
one other absurd idea is that you can,t modify a cross member for the required clearance.
I had to have a good long discussion with one guy before the idea that a muffler from the exact same company with very similar measurements to the muffler that was discontinued could be used, there was plenty of room, it was simply that the owner felt the fact that the part was not listed as fitting his car made it a physical impossibility to fit the component

viewtopic.php?f=56&t=3155&p=37050&hilit=corvette+exhaust#p37050

viewtopic.php?f=56&t=1166
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: fabricating a decent exhaust

Postby Indycars » December 22nd, 2013, 10:20 pm


Thanks Grumpy for always questioning the normal for most people. It's made
me question exactly what I'm capable of doing!!!



Rick
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- Check Out My Dart SHP Engine Project: viewtopic.php?f=69&t=3814
- Need a Dynamic Compression Ratio Calculator: viewtopic.php?f=99&t=4458
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Re: fabricating a decent exhaust

Postby grumpyvette » May 30th, 2014, 4:54 pm

heres the results of a well done custom fabricated 3.5" exhaust,I found posted, with an (X) pipe in a c3 corvette,built from mandrel bent and carefully fitted pipe and components easily sourced from several sources, then fitted cut and welded.
a low restriction exhaust allows the engine to breath, and its mandatory your install an efficient low restriction exhaust behind the header collectors on any performance car, be it under the car with an (X) pipe or separate tuned side exhaust, if your trying to squeeze the max potential from an engine, obviously ground clearance must be checked and tucking the exhaust up near the cars frame and suspension where its not subjected too damage from every raised manhole cover edge or speed bump you might pass over is mandatory, so you can,t just throw it together, it needs to be well planed out and fabricated correctly


Image
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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: fabricating a decent exhaust

Postby philly » May 30th, 2014, 9:00 pm

gorgeous... very well done
-phil

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