straight pipes wreck your engine?

[9jetta6]

so i brought the turtle to the shop to get some of the maintence done, 100k stuff i guess. when i pulled in, the guy said in a concerned mad voice how long have you been driving it like this? i said what do you mean, the exhaust he said, oh just a week pretty much havent been really driving much either, oh that recks your engine you know that right? i said oh no i didnt, its going to get fixed in a couple weeks or next week. he said something with the pressure valves or some sort of valves. is this true? i mean he is a mechanic, but can straight pipes acutally ruin your car? because i hope it sure hasnt done anything to my car...

[reverend]

there needs to be a certain amount of back-pressure for the engine to operate properly.

[Die Frau]

LOL... You ain't wrecking shit.

Perhaps you might be a little down on power if the back pressure isn't right... but it isn't like you are running stacks out your hood or open headers.

[Digital K]

yeah its fine.

[Die Frau]

Sounds like a mechanic that was looking for a longer appointment...

[Dwalmop]

so i brought the turtle to the shop to get some of the maintence done, 100k stuff i guess. when i pulled in, the guy said in a concerned mad voice how long have you been driving it like this? i said what do you mean, the exhaust he said, oh just a week pretty much havent been really driving much either, oh that recks your engine you know that right? i said oh no i didnt, its going to get fixed in a couple weeks or next week. he said something with the pressure valves or some sort of valves. is this true? i mean he is a mechanic, but can straight pipes acutally ruin your car? because i hope it sure hasnt done anything to my car...

Like the others said, you're fine. It's a good laugh though.

there needs to be a certain amount of back-pressure for the engine to operate properly.

How so?

[Sven7]

I've heard no back pressure can burn your valves or something. It's hard to get a straight answer. Is it different on CIS vs. other FI vs. carbs?

[VAGatHeart]

Check yourself before you wreck yourself.

[JK9K]

The valves will burn of the motor is running lean...I doubt simply running straight exhaust is going to cause that to happen.

[the_bomber]

rule of thumb for race pipes for people I know is that you take a crayon, and run it along your hot exhaust with it running, where it stops melting is where you are safe to cut it off without burning valves..

[veedubmechanic]

Sounds like a mechanic that was looking for a longer appointment...

yup


He probably said something like :
"back in the day we used to straight pipe our chevelle's and race on 42, then my buddy blew his motor. It was those straight pipes that caused the valves to burn out"

[Audiphile]

there needs to be a certain amount of back-pressure for the engine to operate properly.

This is true for 2 stroke engines, but not for 4 strokes. 9jetta6, your "mechanic" doesnt know whats he is on about. Regardless, you shouldnt have your car straight piped, because its loud and obnoxious to everyone else on the road.

[16vguy]

Well, it is true, to an extent.

An open exhaust will cause more flow, even more so on an open one off the header, as it scavenges with the cool outside air. More flow, on an exhaust valve, will heat it up- sometimes , if its an extreme, can burn a valve. The only way a exhaust valve cools, is by seat contact. On a stock car, with a stock exh manifold, i dont think it would be possible.

However, when that does happen, it is typically in carburated race engines, that is tuned to perfect stochiometric WITH a certain exhaust, and also have very small valve/seat contact (ie radius, or multiple angle seats.), and are switched to a very short (typically side) exhaust, or teh exhaust breaks off during a race, without any other tuning, and are also running at high rpm. Also, ignition timing can affect exh temps drastically, however, doesnt apply here.

The crayon trick is for a crossover pipe on V motors, or for a collector on long tubes. Although, i suppose it would also work for safe length, but I have never heard that.

If you are running straight off the manifold, I would say there is a possibility for damage. But more than likely, not. There is probably enough unburned fuel, and oil coming out of that thing to cool it plenty.

Its kind of a urban myth. Valve materials have come a long way in 50 years, and very, very, very seldom to you see a burned valve. And, also, just because some unknown "mechanic" told you something, you shouldnt always do it. I would say for every good mechanic, there are 40 ass clowns. Get a second opinion- which i suppose you are doing here.

But, regardless, save the money for the 100k. Change the oil, and buy a damn exhaust. Even if quiet, who cares. A 2 liter wont gain much from an exhaust anyway, especially not a open one.

[oneunder]

^ That guy.

Listen to him.

[KOOTER]

Go find a different mechanic.