993 Faq Frequently Asked Questions about the Porsche 1994-1997 993

01/31/2005

Muffler bypass pipes

Filed under: Exhaust — Jeff 993TT @ 4:38 am

Muffler bypasses pipes bypass the muffler all together. They replace the almost 2 feet of tubing and sound deadening material in the muffler.

For turbo cars, the difference is quite dramatic. In addition they save about 20 lbs off the back end of the car. Throttle response and power are noticable increased.

However, the increased noise may not be for everybody. In the Fabspeed muffler bypass pipes I used for my turbo, there was slight responance from 2800-3000 rpm.

For normally apirated cars, I imaging that difference would be less dramatic, although you would get the same amount of exhaust noise as a turbo.

12/20/2002

Smoking exhaust on startup ( NA cars )

Filed under: Engine,Exhaust — Jeff 993TT @ 11:17 am

A small puff of smoke on startup is not any cause for alarm. If it does not go away after 5 seconds, then you will have to seek the advice of your mechanic.

There are many different reasons for this:

a) Boxer engine design – Allows oil to pool in the cylinders after running, probably due the expansion/contraction of the cylinder walls, allowing a small amount of oil to seep through. This has not been verified.

b) Overfilling the oil. Check the owners manual for the proper procedure for checking a dry sump oil system.

How do electronic boost controllers work?

Filed under: Exhaust,Turbo — Jeff 993TT @ 9:54 am

A wastegate is a valve that regulates the boost in our cars. It does this by opening at a preset setting and allows exhaust gas to bypass the turbo out to the atmosphere (either through a muffler or directly out.). This keeps the turbo from spinning faster, therefore keeping the boost at the preset setting.

Speaking strictly of external wastegates, most, maybe all, wastegates, electronically controlled or manually controlled have a mechanical spring in them. When you install a 1bar boost spring in the wastegate, the turbo will not produce anything more than 1 bar of boost. Since it is a mechanical device, as the pressure on the spring increases, it begins to open the wastegate, so by about .5bar, the wastegate is starting to open even though it has not yet reached full 1 bar boost. This causes some degree of inefficency as the boost does not build as fast as it could by keeping the wastegate closed until 1bar. Additionally, a manual wastegate, although set with a 1 bar boost spring, may tend to fall off in the upper gears and may only allow .8 or .9bar.

An electronically controlled wastegate, uses engine vaccuum/boost pressure to assist the spring tension and keep the wastegate closed until its preset setting. Take the above example of 1bar. An electronic controller can usually handle about 150% of the spring rate, so if you install a .7bar boost spring, the controller can be set to control from .7bar up to about 1.05bar of boost. Once the electronic controller senses 1bar, it will release the spring and the wastegate will open and it will regulate it exactly at 1bar assuming it was programmed properly. You can also usually change the setting on the fly. If for instance, you wanted less boost while driving in the rain, you could set it to .7bar with the touch of a button.

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12/15/2002

Oval Exhaust tips

Filed under: Exhaust — admin @ 6:14 pm

The factory oval exhaust tips came in 2 offsets.

The NA cars and the Turbo used the same offset and have these part numbers:
993.111.981.01 L
993.111.982.01 R

The C4s/C2s used another offset and have these part numbers:
993.111.981.02 L
993.111.982.02 R

The can be bought here: Carnewal – Oval Exhaust Tips

If the exhaust tips do not line up, there is only angle adjustment allowed with the flange clamp. It is possible to adjust the amount the tip protrudes by shifting the muffler, but there is not very much room for movement. The muffler clip only provides several mm of movement.

By adjusting the rotation of the tips you can make it “look” like they are the same. Meaning you can only make it look better but it probably won’t be perfect.

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Cat bypass pipes

Filed under: Exhaust,Turbo — Jeff 993TT @ 6:08 pm

Catalytic converts convert the incomplete burning of gasoline products into more environmentally friendly products.

But as with any filter, it will reduce air flow, which reduces power. Environmentally ethics aside, I will share my experiences with them.

For a NA car, the effects will be much less notacable than a turbo. That is because on a turbo car, the most exhaust gasses which are expelled means more forced air into the engine.

Popular manufactures are Cargraphics and FVD. Cost is about $2500 for a turbo car.

What are RSR mufflers?

Filed under: Exhaust — Jeff 993TT @ 4:40 pm

RSR mufflers are made by another Porsche enthusiest and is very popular for the increased throatyness of the sound. There are versions for both normally aspirated and turbo cars.

More information can be found here: RSR Muffler for 993

Here is a short except from the web page above:

Enough talk about the RSR name, I really came out with the RSR Muffler to satisfy my own needs. After months of searching for a perfect exhaust for my car (a 1996 993), and trying out several different solutions I came to the conclusion that in order for me to have what I wanted I needed to build one for myself. What I was looking for in a 993 exhaust in particular was the extra 911 muscular growl that was missing since the introduction of the 993, as you may or may not know Porsche tried really hard to lower the noise level of their cars with the introduction of the 993 model in order to meet strict European “drive by” standards. Although this is perfect for most Yuppies, but for an old fashion 911 enthusiast like me this is a nightmare. But in the same time I didn’t want to deal with too much resonance and didn’t want my car to sound like a modified “Rice Burner” (Japanese cars with big exhaust tips). I wanted a sophisticated mechanical sound and a muscular sounding idle…….

RSR Muffler for 993

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