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The Datsun 1200 used a 1-1/2 inch exhaust system. The cast iron exhaust manifold has a flat two-bolt flange. A donut-type asbestos seal was used to connects to the exhaust pipe, which extended past the rear axle. Finally a very, very quiet muffler with a short tail pipe was suspended by two rubber rings.
Contents |
Overview
muffler with integrated pipe
Bottom (old) is the factory piece
A12GX Engine (twin carb) models used a quieter exhaust with a small resonator as well the regular muffler:
Notice the GX also used a cast header with dual outlets.
Sizing for Performance
A large diameter exhaust pipe is needed for maximum high-rpm horsepower. However, a small diameter pipe is needed for low-rpm horsepower. So you can see that a properly sized pipe -- not too big or too small -- is advantageous.
Single Exhaust
- Stock 62 horsepower A10: 35mm (~1-3/8")
- Stock 68/69 horsepower A12: 1-1/2" (38mm)
- modded A-series engine: 1-3/4"
- Max fuel econdomy: 1.5"
- 100 hp engine: 1.75"
- 125 hp engine: 2"
- 200 hp engine: 2-1/4"
- 250 hp engine: 2-1/2"
- 325 hp engine: 3"
Of course you can vary this. For example:
- The larger the engine relative to your car, you can get away with a larger pipe. Although the larger pipe cuts down on low-rpm horsepower you have a big engine so it's not so bad. This increases high-rpm (peak) horsepower
- For better street driveability, go a size smaller
- For drag racing where it is flat-out full throttle, a larger size may work fine
2.5 inch works too, but results in less HP than 1.75 inch pipe
Options
- Muffler system with resonator
- Chrome tailpipe extension (bell-shaped)
-
Coupe vs. Sedan
coupe muffler
- The bends are slightly different.
- The hanger near the end of the tailpipe (in the photo: where the price tag is) is a different place for sedan vs coupe
Part Numbers
Muffler measurements from my car (original muffler?):
- 11-5/8" Shell length
- 8-1/4" Shell oval width
- 3-3/4" Shell oval height
- 1.5" front inlet, centered
- 1.5" rear outlet, on far left of oval
A muffler about 2" longer may fit.
Nissan JDM Catalog
- 20010-H1000 TUBE ASS'Y-exhaust, front - ALL (exc. GX, Automatic)
-
- 20010-H1020 TUBE ASS'Y-exhaust, front - Automatic
- 20010-H2301 TUBE ASS'Y-exhaust, front - GX 4-speed
- 20010-H3400 TUBE ASS'Y-exhaust, front - GXA (GX Automatic)
- 20010-H7200 TUBE ASS'Y-exhaust, front - GX-5
- 20603-H2300 GASKET-exhaust tube - GX and GX-5
- 20602-27700 NUT-fixing, tube end (2) - ALL (except GX, GX-5)
- 20602-27700 NUT-fixing, tube end - GX-5
- 08915-13810 WASTHER-spring lock (3) - GX-5
- 20635-18000 STOPPER-muffler bound - ALL
- 20100-H1000 MUFFLER ASS'Y-with rear tube - Sedan
- 20100-H1400 MUFFLER ASS'Y-with rear tube - Van
- 20100-H2500 MUFFLER ASS'Y-with rear tube - Coupe
- 20630-18000 RING-rubber, muffler clamp (2)
- 20620-H1000 CLIP-tube, exhaust
- 06915-43810 WASHER-plain (2)
- 08915-13810 WASHER-lock
- 08110-85510 or 08110-86010 BOLT
- 08911-10810 NUT
- 20640-18000 STRAP-exhaust hanger
- 20641-18000 WASHER-plain (2)
- 08911-10810 NUT (2)
- 08915-13810 WASHER-lock (2)
- 08110-82210 BOLT (2)
- 20321-H2500 FINISHER-exhaust - GL, GX
- 20720-N2225 SEALER KIT-exhaust tube joint - ALL
USA Catalog
- 20010-H3100 ASSY-TUBE EXHAUST FRONT Sedan Manual Trans (formerly 20010-H1000) $34.92
- 20100-H7001 ASSY-MUFFLER WITH REAR TUBE Sedan Manual Trans (formerly 20100-H1000) $84.72 NLA (but is in 2007 catalog)
- 20321-H2000 FINISHER-EXHAUST (chrome extension) NLA
- 20321-H2500 FINISHER-EXHAUST (chrome extension) $18.36 NLA (but is in 2007 catalog)
Muffler
The muffler should flow at least 2.2 cfm per flywheel HP. For a 69 hp A12, that is 152 cfm
Aftermarket 1.5
- Dynomax 17700 ("Thrush turbo"),similar shape to stock. Oval 3.25 in. x 7.75 in. Case Length: 11 in. Overall length: 16 in. Width: 7.750 in. Thickness: 3.25 in.
1-1/2 pipe clamps:
- Merit M112 or U112
- Napa BK 7335325
Rubber Donut Hangers
- Merit 8166 ???
Aftermarket GX (is it the same as the S110 gasket?)
- Gasket: Merit 8696
- Pipe: (1981 Nissan 720), Merit 48316
Exhaust Tip - 1-1/2" diameter
- Merit 9821
Aftermarket 1.75
- Walker Super Turbo WLK-17771
- Dynomax 17771, 160 cfm
- WALKER Pro-Fit Muffler, 1.75" offset/center, #17881
- Magnaflow 11123 with offset. Might be too long, it is 14" body, but it is Stainless Steel, best buy
- Borla XR-1: BOR-40483 Stainless Steel, 1.75 in, 2.25 out
Search for these using http://google.com or http://www.napaonline.com
System
David Vizard says exhaust pipe diameter makes a significant difference.
In practice though it is better, especially for a street-driven machine, to have pipes a little too small rather than a little too big. If the pipes are too large a fair chunk of torque can be lost without actually gaining much in the way of top-end power.
More interesting is about the tuned-header and collector lengths:
on a well-tuned race engine ... the exhaust system draws on the intake port as much as 500 percent harder than the piston going down the bore...the exhaust is the principal means of induction, not the piston moving down the bore.
Vizard recommends a sized extractor and a resonator box placed at the correct length. Then after the resonator it doesn't matter how long the exhaust pipe is or what muffler type is used (open chamber or glass pack). Without a resonator the type of muffler makes a huge difference on horsepower.
- For racing, don't worry about equal length extractors, it's a waste of time.
- For a downdraft induction system, don't mess with the length of the extractor primaries
- The collector length is where you should concentrate your efforts
- At the end of the collector length fit a large expansion chamber (pressure wave termination box)
- The chamber should be 8 to 15 times the volume of one cylinder (larger is better). For an A12 this works out to about 3 liters.
Collector Length:
Pick an appropriate length from the collector. This makes a huge difference on high overlap camshafts and not just a "dyno difference". There is no "correct length" for all A12 engines. It depends on how you build the engine. What cam do you have? Where do you want the max HP to occur? Via the length you can shift the power band somewhat.
Having a proper length (long) collector can provide a lot more HP while in the power band. Up to 22% more. So it's definitely worth doing.
Discussion by jmac: Extractor selection