i understand that an headers are made up of primary and seconday pipes, and the whole idea is to scavage exhaust gases.. Theres a heap of programs out there that you can drop in engine sizes and you can get ur desired exhaust to suit your donk. i heard that you can measure up your own exhaust by bolting up pipes, draw a line along the exhaust in texta, run the engine, and where the line disappears is where the primary length for you engine, then doing the same with the secondaries and you have your perfect exhaust. Is this theory reputable?
The IDEAL lengths for V6 headers are so long they would be impractical in any road car props to greenfoam for the pic.
their not that long, was expecting heaps longer, they look round 3-4feet long. what would be the sweet spot on the formula motors? 7000rpm?
You try and fit them in your car, I'm sure you will change your mind about that. There is a lot of science involved, sometimes it's best to look at what's on offer from the bigger manufacturers, they spend a lot of time and money on R&D. If you were planning on making your own, don't settle on your first version. Make a few sets and changes on each to get comparitive data.
i know theres a ****load involved, i've been doin a bit of research and theres a heap of calculations and whatnot.. i've currently got HM headers installed with catback i just thought that its interesting and relativaly easy to experiment with pipe lengths and i guess diameter would play a big part in testing also. if i had the time i would trial this with a heap of different lengths and diameters also. The thing i like about this method, you wouldnt have to trial much because the lines burnt off at the sweet spot for your engine, thus giving u an exact length. its kinda backyard/bush mechanics style, anyone heard of this method of exhaust trial?
I got taken aside one time at the drags by a old time drag racer with a fast small block chev and he told me about the burnable paint theory. He said you paint the collector with paint that burns go for a hoonand where the paint burnt off is where you cut the pipe. I think it was only for collectors not primary pipe length. Most people use a program called pipe-max it's no very expensive maybe 40usd? but it will give you very acurate calculations on header length. You will be able to fit 3x 1.5 inch primaries as far back as you want on a V6 (4 gets difficult) but 3 is OK. From what I can remember 43 inches is about perfect for a street driven V6 and you would want perhaps a 10 inch collector on the back of those straight into the cats. The big companies don't do correct length headers for Commodores, except maybe the smaller geniune go fast companys like difilipo. Everyone else is just doing the best they can and doing a bit of a compramise to get good clearence
Here's a sample of pipe-max output from a roughed out Ecotec V6, great for getting your intake runners and exhaust calculated --- Single Primary Pipe Specs --- for 231.360 CID from 3000 to 5500 RPM Diameter= 1.385 to 1.510 Length= 35.2 to 38.0 inches long --- 2-Step Primary Pipe Specs --- 1st Dia. inches= 1.385 Length= 17.6 to 19.0 2nd Dia. inches= 1.510 Length= 17.6 to 19.0 --- 3-Step Primary Pipe Specs --- 1st Dia. inches= 1.385 Length= 11.7 to 12.7 2nd Dia. inches= 1.510 Length= 11.7 to 12.7 3rd Dia. inches= 1.635 Length= 11.7 to 12.7 --- Header Collector Specs (Conventional Straight Tube) --- Diameter= 2.750 Tuned Lengths= 21.6 best and 10.8 or 43.3 --- Header Collector Specs (Megaphone or Diffuser Cone Shape) --- Diameter= 2.250 taper to 2.750 Megaphone/Diffuser Length= 21.6 inches H-Pipe= 21.6 X-Pipe= 86.6 distance behind end of Primary Tube ends -- Total Exhaust System Tuned Lengths (Primary ends to TailPipe end) -- Best HP/TQ Tuned Collector Lengths= 21.6 , 43.3 , 86.6 , 173.1 inches long Worst HP/TQ Loss Collector Lengths= 32.5 , 64.9 , 129.9 , 259.7 inches long Note=> measured from where the Primary Pipes end inside the Collector to the point the tailpipe exits into the atmosphere. Note-> all Pipe Diameters are OD and based-off .0625 inch Pipe thickness ---- Primary Pipe's Harmonics ---- 1st Harmonic = 153.6 inches long ... typically never used 2nd Harmonic = 58.5 inches long ... longest recommended 3rd Harmonic = 35.2 inches long ... highly recommended , best Torque Curve 4th Harmonic = 24.7 inches long ... shortest recommended 5th Harmonic = 18.7 inches long ... typically never used 6th Harmonic = 14.8 inches long ... typically never used 7th Harmonic = 12.1 inches long ... typically never used 8th Harmonic = 10.1 inches long ... typically never used ---- Collector's Harmonics (includes Intermediate, Muffler , TailPipe) ---- 1st Harmonic = 173.1 inches long ... longest with Mufflers and TailPipes 2nd Harmonic = 86.6 inches long ... longest recommended with Mufflers 3rd Harmonic = 43.3 inches long ... more bottom-end Torque 4th Harmonic = 21.6 inches long ... highly recommended , best Torque Curve 5th Harmonic = 10.8 inches long ... reduced Torque , more top-end HP sometimes 6th Harmonic = 5.4 inches long ... reduced Torque , not recommended -------------------------------------------------------------------------------------------------------------- 231.360 Cubic Inches @ 5000 RPM with 92.0 % Volumetric Efficiency PerCent Required Intake Flow between 125.8 CFM and 132.0 CFM at 28 Inches Required Exhaust Flow between 98.0 CFM and 106.2 CFM at 28 Inches 600 RPM/Sec Dyno Test Lowest Low Average Best Peak HorsePower 172.8 180.0 183.5 187.1 Peak Torque Lbs-Ft 201.3 209.6 213.7 217.8 HorsePower per CID 0.747 0.778 0.793 0.809 Torque per Cubic Inch 0.870 0.906 0.924 0.942 BMEP in psi 131.2 136.6 139.3 142.0 Carb CFM at 1.5 in Hg. 308 343 360 377 Target EGT= 1449 degrees F at end of 4 second 600 RPM/Sec Dyno accel. test Octane (R+M)/2 Method = 89.6 to 92.7 Octane required range Air Standard Efficiency = 59.73663 % for 9.400:1 Compression Ratio Peak HorsePower calculated from Cylinder Head Flow CFM only 600 RPM/Sec Dyno Test Lowest Average Best Potential Head Flow Peak HP = 158.2 199.9 241.5 ----- Engine Design Specifications ----- ( English Units ) ( per each Valve Sq.Inch area ) Engine Size CID = 231.360 Intake Valve Net Area = 2.474 CID per Cylinder = 38.560 Intake Valve Dia. Area = 2.545 Rod/Stroke Ratio = 1.753 Intake Valve Stem Area = 0.071 Bore/Stroke Ratio = 1.118 Exhaust Valve Net Area = 1.744 Int Valve/Bore Ratio = 0.474 Exhaust Valve Dia. Area = 1.815 Exh Valve/Bore Ratio = 0.400 Exhaust Valve Stem Area = 0.071 Exh/Int Valve Ratio = 0.844 Exh/Int Valve Area Ratio = 0.713 Intake Valve L/D Ratio= .244 Exhaust Valve L/D Ratio= .289 CFM/Sq.Inch = 49.4 to 51.9 CFM/Sq.Inch =54.0 to 58.5 Curtain Area -to- Valve Area Convergence Intake Valve Lift inch= .450 Curtain Area -to- Valve Area Convergence Exhaust Valve Lift inch= .380 Intake Valve Margin CC's Exhaust Valve Margin CC's 1.00 CC = 0.0240 1.00 CC = 0.0336 0.50 CC = 0.0120 0.50 CC = 0.0168 0.25 CC = 0.0060 0.25 CC = 0.0084 0.10 CC = 0.0024 0.10 CC = 0.0034 ------- Piston Motion Data ------- Average Piston Speed (FPM)= 2833.33 in Feet Per Minute Maximum Piston Speed (FPM)= 4629.05 occurs at 75.156 Degrees ATDC Piston Depth at 75.156 degree ATDC= 1.4955 inches Cylinder Volume= 277.9 CC Maximum TDC Rod Tension GForce= 1551.45 G's Maximum BDC Rod Compression GForce= 862.82 G's ------- Current Camshaft Specs @ .050 ------- IntOpen= -10.00 IntClose= 34.00 ExhOpen= 34.00 ExhClose= -10.00 Intake Duration @ .050 = 204.00 Exhaust Duration @ .050 = 204.00 Intake CenterLine = 112.00 Exhaust CenterLine = 112.00 Compression Duration= 146.00 Power Duration = 146.00 OverLap Duration = -20.00 Lobe Center Angle (LCA)= 112.00 Camshaft installed Straight Up = 0.00 degrees -Recommended Camshaft Valve Lift- Minimum Normal Maximum Intake = 0.429 0.462 0.508 Exhaust = 0.386 0.416 0.458 Max-effort Intake Lift = 0.533 Max-effort Exhaust Lift = 0.480 Minimum Intake Valve Lift to prevent Choke = .462 Lift @ 5000 RPM Minimum Exhaust Valve Lift to prevent Choke = .416 Lift @ 5000 RPM - Induction System Tuned Lengths - ( Cylinder Head Port + Manifold Runner ) 1st Harmonic= 35.213 (usually this Length is never used) 2nd Harmonic= 19.985 (some Sprint Engines and Factory OEM's w/Injectors) 3rd Harmonic= 13.953 (ProStock or Comp SheetMetal Intake) 4th Harmonic= 10.982 (Single-plane Intakes , less Torque) 5th Harmonic= 8.910 (Torque is reduced, even though Tuned Length) 6th Harmonic= 7.496 (Torque is reduced, even though Tuned Length) 7th Harmonic= 6.470 (Torque is greatly reduced, even though Tuned Length) 8th Harmonic= 5.690 (Torque is greatly reduced, even though Tuned Length) Note> 2nd and 3rd Harmonics typically create the most Peak Torque 4th Harmonic is used to package Induction System underneath Hood Plenum Runner Minimum Recommended Entry Area = 1.342 to 1.510 Sq.Inch Plenum Runner Average Recommended Entry Area = 1.543 Sq.Inch Plenum Runner Maximum Recommended Entry Area = 1.576 to 1.865 Sq.Inch Minimum Plenum Volume CC = 442.3 [typically for Single-Plane Intakes] Minimum Plenum Volume CID= 27.0 [typically for Single-Plane Intakes] Maximum Plenum Volume CC = 3791.3 [typically for Tunnel Ram Intakes] Maximum Plenum Volume CID= 231.4 [typically for Tunnel Ram Intakes] ------- Operating RPM Ranges of various Components ------- Camshaft Intake Lobe RPM = 4202 Exhaust Lobe RPM = 3910 Camshaft's Intake and Exhaust Lobes operating RPM range = 2129 to 4129 Note=> Lobe RPMs are only BallPark estimations Minimum Intake Valve Lift to prevent Choke = .462 Lift @ 5000 RPM Minimum Exhaust Valve Lift to prevent Choke = .416 Lift @ 5000 RPM Current (Intake Valve Curtain Area -VS- Time) Choke RPM = 4760 RPM Current (Exhaust Valve Curtain Area -VS- Time) Choke RPM = 5285 RPM Intake Valve Area + Curtain Area operating RPM Range = 3448 to 5448 RPM Intake Valve Diameter RPM Range = 2760 to 4760 Intake Flow CFM @28in RPM Range = 2769 to 4769 ___________________________________________________________________________ Best estimate RPM operating range from all Components = 2771 to 4771 Note=>The BEST Engine Combo will have all Component's RPM Ranges coinciding ___________________________________________________________________________ --- Cross-Sectional Areas at various Intake Port Velocities (@ 28 in.) --- 121 FPS at Intake Valve Curtain Area= 2.488 sq.in. at .440 Lift 119 FPS at Intake Valve OD Area and at Convergence Lift = .450 146 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 2.061 sq.in. at 5000 RPM 350 FPS Velocity CSA= 0.862 sq.in. at 5000 RPM Port Sonic-Choke with HP Loss 330 FPS Velocity CSA= 0.915 sq.in. at 5000 RPM Port Sonic-Choke with HP Loss 311 FPS Velocity CSA= 0.971 sq.in. at 5000 RPM Smallest Useable Port CSA 300 FPS Velocity CSA= 1.006 sq.in. at 5000 RPM Recommended Smallest Port CSA 285 FPS Velocity CSA= 1.059 sq.in. at 5000 RPM Recommended Smallest Port CSA 260 FPS Velocity CSA= 1.161 sq.in. at 5000 RPM Recommended Port CSA 250 FPS Velocity CSA= 1.208 sq.in. at 5000 RPM Recommended Port CSA 240 FPS Velocity CSA= 1.258 sq.in. at 5000 RPM Largest Intake Port Entry CSA 220 FPS Velocity CSA= 1.372 sq.in. at 5000 RPM Largest Intake Port Entry CSA 210 FPS Velocity CSA= 1.438 sq.in. at 5000 RPM Torque Loss + Reversion 200 FPS Velocity CSA= 1.510 sq.in. at 5000 RPM Torque Loss + Reversion --- Cross-Sectional Areas at various Exhaust Port Velocities (@ 28 in.) --- 117 FPS at Exhaust Valve Curtain Area= 2.101 sq.in. at .440 Lift 135 FPS at Exhaust Valve OD Area and at Convergence Lift = .380 167 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 1.470 sq.in. at 5000 RPM 435 FPS Velocity CSA= 0.563 sq.in. at 5000 RPM Sonic Choke at Throat Area 350 FPS Velocity CSA= 0.700 sq.in. at 5000 RPM Port Sonic-Choke with HP Loss 330 FPS Velocity CSA= 0.743 sq.in. at 5000 RPM Port Sonic-Choke with HP Loss 311 FPS Velocity CSA= 0.788 sq.in. at 5000 RPM Smallest Useable Port CSA 300 FPS Velocity CSA= 0.817 sq.in. at 5000 RPM Recommended Smallest Port CSA 285 FPS Velocity CSA= 0.860 sq.in. at 5000 RPM Recommended Smallest Port CSA 250 FPS Velocity CSA= 0.980 sq.in. at 5000 RPM Recommended Port CSA 240 FPS Velocity CSA= 1.021 sq.in. at 5000 RPM Recommended Port CSA 225 FPS Velocity CSA= 1.089 sq.in. at 5000 RPM Largest Exhaust Port Exit CSA 210 FPS Velocity CSA= 1.167 sq.in. at 5000 RPM Largest Exhaust Port Exit CSA 190 FPS Velocity CSA= 1.290 sq.in. at 5000 RPM Torque Loss + Reversion 180 FPS Velocity CSA= 1.361 sq.in. at 5000 RPM Torque Loss + Reversion ---- Some Useful Formulas are: ---- Average_CSA = Port_Volume_CC / (Port_CenterLine_Length * 16.387) Port_Volume_CC = Average_CSA * Port_CenterLine_Length * 16.387 Port_CenterLine_Length = Port_Volume_CC / ( Average_CSA *16.387 ) FPS = ( Flow_CFM * 2.4 ) / Average_CSA Flow_CFM = Average_CSA * FPS * .4166667 Average_CSA = ( Flow_CFM * 2.4) / FPS Valve Intake Exhaust Curtain Area 300 FPS Velocity Minimum Head Lift Choke Choke Square Inches Cross-Sect Area Flow @ 28 In inches RPM RPM Intake Exhaust Intake Exhaust Int Exh .050 541 601 0.283 0.239 0.109 0.088 13.6 11.0 .075 811 901 0.424 0.358 0.163 0.133 20.4 16.6 .100 1082 1201 0.565 0.478 0.218 0.177 27.2 22.1 .125 1352 1502 0.707 0.597 0.272 0.221 34.0 27.6 .150 1623 1802 0.848 0.716 0.327 0.265 40.8 33.1 .175 1893 2102 0.990 0.836 0.381 0.309 47.6 38.7 .200 2164 2402 1.131 0.955 0.435 0.353 54.4 44.2 .225 2434 2703 1.272 1.074 0.490 0.398 61.2 49.7 .250 2704 3003 1.414 1.194 0.544 0.442 68.0 55.2 .275 2975 3303 1.555 1.313 0.599 0.486 74.8 60.7 .300 3245 3604 1.696 1.433 0.653 0.530 81.7 66.3 .325 3516 3904 1.838 1.552 0.708 0.574 88.5 71.8 .350 3786 4204 1.979 1.671 0.762 0.619 95.3 77.3 .375 4057 4505 2.121 1.791 0.817 0.663 102.1 82.8 .400 4327 4805 2.262 1.910 0.871 0.707 108.9 88.4 Valve Intake Exhaust Curtain Area 300 FPS Velocity Minimum Head Lift Choke Choke Square Inches Cross-Sect Area Flow @ 28 In inches RPM RPM Intake Exhaust Intake Exhaust Int Exh .425 4598 5105 2.403 2.029 0.925 0.751 115.7 93.9 .450 4868 5406 2.545 2.149 0.980 0.795 122.5 99.4 .475 5138 5706 2.686 2.268 1.034 0.839 129.3 104.9 .500 5409 6006 2.827 2.388 1.089 0.884 136.1 110.5 .525 5679 6307 2.969 2.507 1.143 0.928 142.9 116.0 .550 5950 6607 3.110 2.626 1.198 0.972 149.7 121.5 .575 6220 6907 3.252 2.746 1.252 1.016 156.5 127.0 .600 6491 7207 3.393 2.865 1.306 1.060 163.3 132.5 .625 6761 7508 3.534 2.985 1.361 1.105 170.1 138.1
43 inchs is about right.about the paint on the pipes in the old days when fitting a crossover pipe between left and right bank on twin systems you used to put white crayon along the lengths of pipe after the headers and where it burnt first was where the balance pipe was welded in for a nicely tuned exhaust
thanks Foams, damn it spits out a heap of info. i guess if you wanted to tune it perfectly all the info would be awesome. i'll sift thru it over the weekend. delcowizzid: its good hearing more stories of this style of tuning. for getting the balance pipes, where did the measurement start from, after the headers?
I've also heard that the best way to 'balance' a twin exhaust is to not truly 'merge' the pipes into one and back out, but a hole about 1/2" between the two and welded together. I personally have not done any testing with this but I imagine it would be different for every single car.
