How to make a '74 1.8L sound less like a VW bug, Would this necessitate a muffler change? Muffler modification? Exhaust tip? Options

[mjsdt914]

Looking to improve the sound of my '74 1.8L ... make is less like a VW Bug ((

[Jake Raby]

Lots of other factors create the character of the engine note the T4 has other than the exhaust. Usually the intake note of my engines is louder in the car than the exhaust, and the components and clearances I use change the mechanical notes as well.

Usually what makes a T4 sound more like a VW than a Porsche is the valve train clatter, which can be altered with components and clearances.

So what "VW noise" are you trying to cancel out?

If I have learned anything about T4 engines over the last 28 years it has been the correlation between exhaust sound and performance do not go hand in hand. If the exhaust is developed for sound, it'll usually suck for performance and engine tune ability. The latter is the most important, as rich running is directly indicative of poor exhaust design. When testing exhaust systems I can tell within one dyno pull if they are worthy a damn or not, and that is all based on the shape and specifics of the air fuel ratio curve. If an engine wants more fuel to reach 13:1 AFR I know that exhaust is a good design, if it wants less fuel then I know the exhaust sucks.

I see engines that act lean in the way they behave, but indicate overly rich fuel mixtures. These are the worst exhaust designs of all. I see this primarily when people (including me 20+ years ago) attempt to try a 4-2 exhaust design with these engines. This does not work, no matter how the cylinders are paired. It sounds like a sick Harley, runs rich, and can't be tuned- period.

To me you either choose sound or performance/ efficiency/ tuning. The guys that choose the former never really realize what they leave on the table for performance and tuning. They do wonder why the engine has higher than optimum CHT and OT (oil temperatures) and why the engine averages 10 MPG all the time. They wonder why the oil turns black from soot in a couple hundred miles, and they wonder why they have issues with blow- by compression. They wonder why their air filters (dual carbs especially) are soaked in unburned fuel spray from stand- off.

They never correlate exhaust with any of this. I know that ALL of this is impacted by exhaust design in relation to the T4. Having designed many systems for my 996/997/Cayman engines over time I'll say that these engines do not follow suite and they have completely different rules when it comes to design. Just like my 4.1L 993 based engine loves a pair of 3-1 pairings with a nice detailed collector makes it completely different than that of the M96/M97/9A1 engine that has proven to hate this.

Admittedly, most of my direct experience is not with engines that retain stock heater boxes since these generally don't perform well enough for even my least performing engines. Due to this the systems that utilize basic/ stockfish mufflers aren't my forte. Today I start with 180HP at minimum from what I build and the design changes I have made to the engine internals in regard to camshafts and cylinder heads with my generation 7 engines no longer really like the 4-2-1 design like they used to in the earlier days. Today a short primary 4-1 usually makes the flattest torque curve and best peak power at the same time, if the collector design is correct. I started changing things around back in 2010 when I developed my "Evil Twist" T4 conversion exhaust used mostly in 356s/ 912s then VW conversion applications.

Mufflers do make a difference, since sound wave control is a definite factor with everything related to exhaust. What really woke me up was buying a much bigger flow bench (Superflow 1020) that can really show the differences in flow characteristics between mufflers. What I learned quickly on this bench was sound and volume don't go hand in hand when it comes to muffler design, and "back pressure" is often misunderstood as a factor that doesn't even exist.

These things said, any engine 2270cc or larger has every factor heavily impacted by exhaust design. If you get the exhaust wrong, you botch the entire engine combination.

I think that it is ok to create an engine that sounds like nothing else. People spend all their time trying to make the car sound like something it isn't, when they should be embracing the uniqueness. If you identify the unique sound and behaviors as "flaws" it means you are decreasing the individuality of the 914.

That's just my perspective, and most won't agree with it.

[Van B]

I see this primarily when people (including me 20+ years ago) attempt to try a 4-2 exhaust design with these engines. This does not work, no matter how the cylinders are paired. It sounds like a sick Harley, runs rich, and can't be tuned- period.

You broke my heart with this observation Jake lol...