In keeping with this "exhausting" issue of VW Trends magazine, we decided to take some of the more commonly available exhaust systems and put them to the test. We wanted to see how much they actually help the VW aircooled engine breathe better, thereby increasing horsepower and torque. We made a call to The Real Source, in Effingham, Ill., ordered the most commonly available aftermarket exhausts and ran them on Geoff Hart's Stuska engine dyno in Fountain Valley, Calif. The "mule motor" that we used was a brand new, bone-stock, Mexican-built, 1600cc, dual-port engine from Btlmex, in Nogales, Ariz.
The first thing we did, to establish a baseline, was to fire up the engine and run it in. Right away, we realized that the factory doesn't set the valves on brand new engines; they leave the valves un-adjusted so that during storage there won't be any pressure on the valve springs. After a quick cool down, adjustment and break-in of the engine, we are ready to see what, if any, gains could be made by the simple addition of an aftermarket exhaust.
So we took the bone-stock engine, popped it on the dyno and fired it up.
The stock 1600s come equipped with a Bocar 34 PICT-3 carb, with a 117 main jet and a 90 air. We took the new engine to 5000rpm, a level we still felt somewhat safe with. As you will see, the exhausts were very close in horsepower and torque readings. From here, you will have to check the price and availability of these exhausts, and decide which one fits your needs. To see audio clips of these dyno tests, click on the links below the images. You'll need to have Quicktime, Win Amp or another MP3 player.
Stock 1600cc Exhaust
rpm lbs. hp torque
2500 16.8 42 88.23
3000 16.2 48.6 85.08
3500 15.2 53.2 79.83
4000 14.2 56.8 67.22
4500 12.8 57.6 67.22
5000 10.2 51 53.57
Not too bad for a fresh engine, huh? Next, we installed a Euro sport single tip exhaust and tried it again. This exhaust is designed to run the tips out the stock location in a Sedan rear apron.
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Tri-Mil Eurosport Single-Tip
rpm lbs. hp torque
2500 17.2 43 90.33
3000 16.6 48.9 87.18
3500 15.6 54.6 81.93
4000 15 60 78.78
4500 13.6 61.2 71.42
5000 11.2 56 58.82
We got between four and five horsepower from 4000rpm to our redline of 5000. A quick plug check showed that with the free-flowing exhaust the engine was running lean. The 117 main jet was changed to a 125.
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Tri-Mil Eurosport single-Tip (re-Jet)
rpm lbs. hp torque
2500 17.2 43 90.33
3000 16.8 50.4 88.23
3500 16.4 57.4 86.13
4000 15.2 60.8 79.83
4500 13.8 62.1 72.47
5000 11.8 59 61.97
A simple three-dollar jet change netted us a solid three extra ponies at 5000rpm. Another plug check told us the engine was happier with the fatter main jet. With the rest of the free-flowing exhausts yet to come, we left it right where it was.
Now, we took off the Euro Sport Single Tip, and installed an S&S header with a single quiet-pack muffler. This exhaust was one of the best-fitting.
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S&S Header/Single Quiet Pack
rpm lbs. hp torque
2500 18 45 94.54
3000 16.9 50.70 88.76
3500 16.4 57.40 86.13
4000 15.6 62.40 81.93
4500 14.2 63.90 74.58
5000 12 60 63.02
Seems like the engine responded well to the S&S system. It was probably a better match, however slight, in back pressure for the stock intake and carb system. The S&S edged out the Tri-Mil by 1hp and about 1 lb-ft of torque at 5000rpm.
Then we simply unbolted the single muffler, and using Performance Technology's "Burnproof" collector gasket, installed the S&S dual muffler onto the header, since the single and dual header are identical.
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S&S Header/Dual Quiet-Pack
rpm lbs. hp torque
2500 17.6 44 92.44
3000 16.8 50.40 88.23
3500 16.6 58.10 87.18
4000 15.8 63.20 73.53
4500 14 63 73.53
5000 12 60 63.02
The engine seemed to like the back pressure of the single quiet pack better. We lost a tiny bit of horsepower at 4000 and 4500rpm, but with a gain of a little over 1/2 hp at 3500rpm.
We installed the BUGPACK header system with a single quiet pack muffler. This system fit with ease as well.
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Bugpack Header/Single Quiet-Pack
rpm lbs. hp torque
2500 17.8 44.50 93.49
3000 17 51 89.28
3500 16.6 58.10 87.18
4000 15.6 62.40 81.93
4500 13.7 61.65 71.95
5000 11.6 58 60.92
It kept up with the S&S unit only seeing a noticeable drop at 5000rpm.
Now we exchanged the BUGPACK single muffler for a dual muffler setup, also by BUGPACK. Since the headers are identical, we added three bolts and a new collector gasket and we were ready to torture this 1600cc some more.
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Bugpack Header/Dual Quiet-pack
rpm lbs. hp torque
2500 17.2 43 90.33
3000 17 51 89.28
3500 16.6 58.10 87.18
4000 15.8 63.20 82.98
4500 14.4 64.80 75.63
5000 12.2 61 64.01
We lost a bit on the lower end, but gained three ponies at 5000rpm. This exhaust, with the dual mufflers, was the highest horsepower at 5000rpm of all the exhausts tested.
Using the same BUGPACK header, we bolted on a hideaway muffler.
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Bugpack Header/Hide-away
rpm lbs. hp torque
2500 17.6 44 92.44
3000 17.2 51.60 90.33
3500 16.8 58.80 88.23
4000 15.8 63.20 82.98
4500 14.2 63.90 74.58
5000 11.6 58 60.92
This one beat the BUGPACK single muffler across the board, with identical horsepower readings at 5000rpm. It even came close to the BUGPACK dual muffler exhaust.
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13/8, 11/2, 15/8, 13/4 and 2: diameter measurements (in inches) of exhaust pipe. The bigger the diameter, the less back pressure, and the better flow the exhaust will have.
Back Pressure: The resistance of the exhaust, for exiting spent gases from the combustion chamber, necessary for proper scavenging of combustion chamber.
EGR (Exhaust Gas Recirculation) Valve: Starting in 1972, Volkswagen added these valves to lower the cylinder temperature and smog emissions. The system takes exhaust gasses, seperates and filters them into inert gasses and introduces them into the combustion chambers through the intake manifold. These gasses take up about 10 percent of the space in the cylinders, but do not explode and are then exited through the exhuast valves.
Center-tip exhaust: Used on 1938 KDF-Wagens, exhaust exited at the center of the rear apron.
Collector: The part of an exhaust where all four tubes come into one.
Dual Quiet Pack: Aftermarket header with two mufflers.
DynoMax: Brand name of high performance muffler.
Flange: Where the exhaust bolts onto the cylinder head, also modification to heater boxes to avoid leaks from stock-style heater box/exhaust coupling, also, where muffler/stinger bolts onto collector.
Four-tip: Type of exhaust that has four exit tips from the muffler body.
Fresh Air: Used on all engines starting from the later 40 horsepower engine; ducts on both sides of fan shroud, and tubes going to heater boxes.
Header: Aftermarket exhaust, usually incorporating an American car style muffler.
Heat Riser: Small tube on stock exhaust & intake manifold that circulates exhaust to intake manifold to prevent icing on single-carburetor applications.
Heater Box: Shroud encasing cylinder number one and number three exhaust tube so that the engine cooling fan can blow hot air into passenger compartment.
HPC: Brand name of aluminized high-temp coating for exhaust systems.
Jet-Hot: Brand name of aluminized high-temp exhaust coating.
Late Single-Tip Exhaust: Used on fuel injected Beetles from chassis number 115000001, 1352000001 and 1552000001 (1975).
Magnaflow: Brand name of high-performance muffler.
Merged: Exhaust that doesn't have any provisions for heater boxes; used mainly in racing applications.
Pea Shooter: The stock, dual tip exhaust that came on all Beetles from 1956 to 1974.
POR-20: Inexpensive high-temp exhaust coating.
Single Quiet Pack: Header exhaust with one muffler.
Single Tip: Early Sedan exhaust with only one exhaust outlet, used on mid-1955 & earlier cars.
Stale Air: no heater outlets on fan shroud; used on all 25, 36, and early 40 horsepower engines.
Stinger: Megaphone shaped tube on the end of exhaust system, for decreased back pressure. (note: Unless baffled, they are illegal to use on the street).
Tri-Mil: Type of exhaust, normally used on Baja Bugs and Buggies
Tuck Away: Header with muffler(s) inside rear fenders.
VHT: Type of high temp spray paint.
Troubleshooting Exhausts
Exhaust Leaks:
These are often confused with other problems. A sound caused by the exhaust system will continue even when the car is idling, although it gets louder when you accelerate. A sound that occurs only when the car is moving is more likely to be caused by some other mechanical problem. If the exhaust system is tight, blocking the tailpipes should stop the engine. Momentarily apply pressure to the tailpipes using wet rags or your shoe. If there are leaks, you'll hear a puffing sound coming from the leak.
Exhaust systems can leak from anywhere, but the usual spots are the flanges at the cylinders, muffler and tailpipe extensions.
Strange Sounds
If you hear a whistle as the engine is accelerated, it is caused by loose or cheap replacement tailpipes, headers or exhaust systems.
A steady, pulsing roar means a hole in a pipe or exhaust system component. If it is a hissing or puffing noise, it could be caused by a crack in the exhaust manifold or a leaking gasket.
A chugging or choking sound can be caused by a blockage in the exhaust system, such as a bent pipe. Rattling noises can be caused by a misaligned exhaust system that is touching something under the car, or by a loose baffle in the muffler or resonator.
A loud metallic vibration usually indicates something is touching the exhaust pipe or a clamp or hanger is loose. A more muffled metallic vibration--especially one that changes in pitch with different engine speeds--is more likely to be a broken baffle in the muffler.
Smoke Signals
Blue smoke from a tailpipe indicates that engine oil is being burned, and that unburned hydrocarbons (HC) are being released into the air.
Black smoke indicates that the air/fuel mixture is too rich to burn completely.
White smoke is steam, and is normally visible on a cold day. However, it can also indicate an internal engine oil leak, especially if accompanied by a pungent odor.--Ryan Lee Price