Type 4 Exhausts
This page was last updated Monday, April 13, 2009
Intro | Exhaust Ports | Articles
Selecting an exhaust system for any car is a critical decision. The exhaust system does more than provide a way out for the spent fuel/air mixture and to muffle the sound of the combustion. Properly designed systems will also "scavenge" the exhaust gases from the combustion chamber and exhaust port. If a system is too restrictive, it will increase the temperatures of the cylinder and be difficult to drive. If your system is too open, there will be dead spot in the lower engine speeds where there isn't enough vacuum to pull out the fumes.
There are many properties that go into a properly designed system. Tube style headers should have equal length tubes, and be free flowing, without kinks or obstructions. It's been found that most Type 4s, from stock to about 2500cc like 1⅝" tubing for headers, and 1¾" for larger engines and engines that will live at high rpms, like 8,000rpm and above. A well tuned header and quiet pack muffler will give you better gas mileage, smooth drivability, and cooler engine temps from the increased efficiency. Check out the Custom Made section of this article for more details of a properly designed header.
The stock exhaust systems are fine for a stock car, but if you looking for a little bit more power or have really modified your VW, then start looking for a header for your car. Most headers are a "4 into 1" system. That means that the four exhausts meet at a single point into a larger pipe. This junction is called the collector. This type of exhaust is commonly seen on the Type 4 engines and the earlier (1.7/1.8) Bus engines.
The other type of header is a "2-2-1" header. This is where the two exhaust ports on each head have their own collector and later on these two pipes merge into another collector and to the muffler. This header is usually seen in the later model Busses, as the stock system does the initial 2-2 collection. Tangerine Racing's SuperHeader is also an 2-2-1 system.
During these articles I will refer to a couple of terms that I need to define here. "Off road" exhausts are designed for vehicles with little or no bodywork behind the engine and for maximum ground clearance. Examples of offroad vehicles include Baja Bugs, fiberglass dune buggies, and sand rails. "Street" exhausts are designed for stock bodied vehicles, like a Bus, Bug, 411/412, etc. Theses exhausts are designed to fit into the stock body with little or no alterations.
The Type 4 cylinder head used two different types of exhaust ports over the years. The early "oval port" was used in all models through 1978. This includes every 914, 912E and 411/412. The 1972-1978 Transporter used the oval port, but in 1979 it received what is called the square port. The heads with the square ports are also referred to as Vanagon heads, as all of the aircooled Vanagons utilized this port.
In the past almost all of the exhaust systems manufactured for the Type 4 conversion were only for use with the oval port. That all is changing though. Manufacturers are now offering adapters or stub tubes for their systems that allow you to install the system on either an oval port or square port engine. When you are shopping for an exhaust system, make sure you know which you have. These ports can be viewed on the Cylinder Head Tour page on this web site.
Due to the size of this article, I've decided to break it into logical blocks. This helps you find the information easier and makes download times reasonable for those on dial-up.
Here is the breakdown of articles:
- Pancake cooling
- This article covers all of the stock VWs that came with the Type 4 engine, namely the 411/412 cars and the Transporter. This article also includes Type 3s, as they also utilize the pancake cooling system when converted. Offroad systems with the stock cooling are also covered.
- Upright cooling
- This is for all of you Bug, Karmann Ghia, and any other car that can use a 1600cc Type 1. This article covers the options for a stock body car and for the offroad crowd.
- Porsche 912 / 912E / 914
- For those Porsche owners, I've got you covered. If your Porsche came Type 4 powered from the factory (914 or 912E), or if your Porsche didn't (like the early 912), there is something available for you. This article also covers the 356 and 550 replica cars.
- Custom exhausts
- Don't see anything that you can use, or have something special in mind? Well, this article is for you. I cover some of the basic points and where to get more information on building your own, or going someplace to have a custom system built for your latest project.
Thanks go to Rolf Christensen, Ron "Plastermaster" Roberts, Ephraim "Ephry73" Castillo, Rich Craig, Tom "Tom Notch" Hansen, and Jake Raby for all of their help in gathering the information and supplying photos. Thanks guys!!
