Any harm running without exhaust?

zbph10 · 10-05-2008, 09:46 AM

I have a cat bypass pipe coming and took the cat off the car this morning. Is there any harm starting the car with out an exhaust system (right out of the turbo) just to hear what it sounds like?

Don't want to drive it around but I thought it would be cool to hear it.

Thanks
Brian

Geronimo '74 · 10-05-2008, 09:56 AM

It's gonna be loud, I can tell you that.
With a normaly aspirated car, there's no problem.
With a turbo, I don't know, but others will surely do.

David · David's Garage

It would still have an exhaust so there shouldn't be a concern of burning a valve. Turbos don't like back pressure and this would be the ultimate in low back pressure so it shouldn't harm the turbo. Just keep your hands and body work clear of the turbo exhaust. I wouldn't rev it very much and like you mentioned, don't drive it.

spuggy · 10-05-2008, 11:59 AM

Some people say that a turbo works well as a muffler. I think they've never heard a free-flowing exhaust on a 930, which is "20 car alarms per floor as you idle through the parking lot" loud. Insanely glorious in a tunnel on boost, very wearing and anti-social the rest of the time. Makes Harley's sound quiet.

Without the tailpipe, it'll be louder still than an open exhaust. It won't be much different in volume to a Zork - which is just an short pipe to direct hot gas safely away from bodywork and wiring etc.

So +1 on not driving it like that.

Formerly Steve Wilkinson · 10-05-2008, 01:09 PM

They used to say that running an engine with stub exhausts could lead to valve warpage when you shut down and the cold air went up the short pipe without getting heated any. We used to quick pop tennis balls into our racecar exhausts immedaitely upon shutdown for that reason, but I suspect it was an old wive's tale. Didn't seem to bother Spitfires and Mustangs.

Quicksilver · 10-05-2008, 03:50 PM

If you run your exhaust ports open with nothing at all past the heads, after a good length of time it will start to mess up the valves. I can't imagine someone who has enough hearing protection to stand it for the length of time it would take to make a difference.

Running the exhaust out through the turbo isn't an issue. You just need to worry about what the exhaust (blowtorch) is blowing on and also about neighbors throwing rocks at you as you rattle their windows loose.