Are Straight Pipes Bad?

[joeydeherrera54]

Originally Posted by junior3382

here is a bit of info for you. Yes, the cats and mufflers are there for noise reduction and for emmisions, but there is a balance too. Your motor needs a certain amount of back pressure. The cats and mufflers provide this. With out them, yes it will be loud, and in some cases abnoxious...lol, but you lose the resistance. Now most guys will say ... "COOL"... but here is the draw back. The motor is tuned from each end. With out the standard back pressure, you will eventually burn out your exhaust valves in the heads and will need to rebuild the top end of your motor. Yes, the sound is cool, the temperary gain in power is fun too, but in then end, the matinence will kill you. Not to mention most states and areas are federally regulated for emissions anyways, and it will not pass with straight pipes.

i may be wrong but i dont argree with this i have ran straight pipes on my trucks every since i have owned then and never had a problem with the top end and for the back pressure you can also ajust by how big you pipe is

[junior3382]

Now in all fairness I was talking about actual straight pipes, 3inch open with no muffler no cats no sensors and such, on the business end of a 5.7l V8. The motor needs the balance, and opening up the exhaust is not always healthy. It can .... over time .... destroy the exhaust valves on the motor. Does not mean it will. There is always an exception to the rule. But I would be willing to bet if you take two exact motors, one with true straights and the other with OEM and ran them side my side for 25,000 miles, and then looked at the valves, there woould be an huge difference. These are not like the motors back in the 60's where they were so simple it was sick, with the ECU's and sensors all over the place..... everything is over "tuned" and therefore needs the balance. Besides his truck has a cat back system anyways, and was concerned it would hurt it, whereas it shouldn't. Everyone has different experiences, that is just mine.

[joeydeherrera54]

Originally Posted by junior3382

Now in all fairness I was talking about actual straight pipes, 3inch open with no muffler no cats no sensors and such, on the business end of a 5.7l V8. The motor needs the balance, and opening up the exhaust is not always healthy. It can .... over time .... destroy the exhaust valves on the motor. Does not mean it will. There is always an exception to the rule. But I would be willing to bet if you take two exact motors, one with true straights and the other with OEM and ran them side my side for 25,000 miles, and then looked at the valves, there woould be an huge difference. These are not like the motors back in the 60's where they were so simple it was sick, with the ECU's and sensors all over the place..... everything is over "tuned" and therefore needs the balance. Besides his truck has a cat back system anyways, and was concerned it would hurt it, whereas it shouldn't. Everyone has different experiences, that is just mine.

yea i argree with you if you go with a 3 inch pipe it wont have enough back pressure i thought we were talking about just stock size just with out any thing else i run 2.5 inch on my truck but i wouldnt go any bigger

[junior3382]

Even 2.5 would be rough if we are talking true straights..... maybe a 4 inch collector, into a 2.5 inch coupler...... maybe..... I would still be careful. To get the sound and hp increase nowadays, a cat back flowmaster system is more then enough. So really true straights, unless for a high performance off-road or track motor, are kinda unnescesary.

[436'd skylark]

I have to chime in here..

first, I don't think there was ever a webster's meaning behind straight pipes. its just some slang somebody started. cats, mufflers, no bends in the piping, this isn't set in stone folks. I always thought it meant no mufflers, just pipe. but that changes with everyone ya talk to.

second, the valve thing. Its been said that with open headers, or zoomies that the exhaust valves are more susceptable to bending since they can cool too quickly. if the valve is open, and a cold gust of wind blows in the port, supposedly the valve can warp. I think its hog wash. I've been around hundreds of drag and street cars that run open headers and nobody has a problem. and those are abused and put away wet too. much more extreme than a daily driver.

third, there is very little power to be had by straight pipes, or cat backs. noise isn't power. period. 10-15 horse, woo hoo. is that worth the 300-400 bucks in exhaust work just to hear your truck growl? gimmie a break.

[junior3382]

Like I was saying before though, on a motor tuned for the open pipes, it is fine, but for today's motors, open flow just cannot be good. I may not know everything here, but it just seems like what I have read and opinions I have gotten long before this post seem to make sense. but by the same theory, you should be able to take the entire intake off, and run with just the port in the side of the manifold, and gain HP and sound, but is that good for the motor?

[jdfenske]

i run stock cats that flow into an X pipe, straight pipe to the bumper, topped off with tips with them little round holes/baffles

meets emissions, keeps the computer happy, as mine has 4 Oxy sensors, high flow, very cheap, no fiber glass to blow out, and gives a good thump, not a ear popping crack, and sounds like a V8, not a pair of 4bangers fighting each other.

and above that, high flow exhausts are alright, people say it's bad, like burning a valve or cold air rushing in and causing warping. i think they make little balls or something fancy to drop in to prevent that? , but i did burn a couple exhaust valves when running 5 grand for a few minutes and nothing bolted to the heads. yes, it was wild.

more air out, means more air in, which means more fuel can be burned cleanly, which means more go go

[Mikeee P]

Originally Posted by junior3382

here is a bit of info for you. Yes, the cats and mufflers are there for noise reduction and for emmisions, but there is a balance too. Your motor needs a certain amount of back pressure. The cats and mufflers provide this. With out them, yes it will be loud, and in some cases abnoxious...lol, but you lose the resistance. Now most guys will say ... "COOL"... but here is the draw back. The motor is tuned from each end. With out the standard back pressure, you will eventually burn out your exhaust valves in the heads and will need to rebuild the top end of your motor. Yes, the sound is cool, the temperary gain in power is fun too, but in then end, the matinence will kill you. Not to mention most states and areas are federally regulated for emissions anyways, and it will not pass with straight pipes.

Just stealing your post because it poses a comment you hear all the time -

Here is a legit question for everyone - how is it that airboat guys here in Florida run 8 straight, short little pipes for exhausts, or just open headers on a 350 V8 and it never harms their engines - they run them wide open all the time for hours and run them for years and years with no problem(s).

I've always heard it was bad for the valves - and used to hear that about motorcycles too - but bikes have Stelite coated valves now which are extremely tough... aren't auto manufactures doing this too (using stronger valves than back in 1960)...

Mechanics tell you all the time that you can burn your valves up with low back pressure - why? A cold charge is coming in every time and blowing the burnt gasses out... so what is supposedly burning the exhaust valves? I even had a mechanic tell me once it was cold air that did it - I explained it was completely impossible for cold air to be sucked back up a 15' long exhaust pipe to get to the exhaust port...

Clue me in, on what you guys think regarding burnt valves - I'm asking because I have a post right now and I'm not sure if I have burnt valves, or if I have a ring problem...

Mike

[junior3382]

If you take a 2008 GMC sierra and simply drop all the emmisions and exhuast components and run an open flow exhaust, it is not healthy. I still hold to this. But I never said their are not motors out there then cannot do it. Those motors on motorcycles, or motors on air boats are built different. They are not built for emmisions like some of today's vehicles are.

Not all burnt valves are due to a cold air infusion. When I posted this originally I was talking about a balance. The technology in todays motors is so different from it used to be. It is not just exhuast mods that can affect the overall performace. Everything has a reaction.

I have not read your other post yet, I will shortly, but I wanted to post this quick. Even NASCAR motors, and drag cars run short straight pipes, but those engines are built for it.

If you think about it rationally, if it was healthy to simply cut it all off, why would there be several converters, and a half of a dozen O2 sensors? And if the motor will never be affected by simply running with out them, why does an O2 failure cause the motor to run like ****? There are more sensors and more electronics on the engines nowadays then ever before, does it really seem like you can just remove them with out any negative results?

I am not saying I am 100% right here. Everyone has an opinion. I simply think about causes and reactions. Reality is, we are not talking about a 1955 Camaro here with only eight plug wires and a battery cable. Things are not a simple as they used to be. And that was my whole opinion.

The OP here may or may not have been talking about a truley open system, all I was saying is that for sound and HP purposes, why not avoid it and run a system designed for the truck? Get the sound and get the performance, and keep the technology the way it was. Thats all.

[Chevy_Finatic79]

Not to be a know it all but the first year Camaro came out was 67. but I agree all the sensors have to run in harmony with each other if not the ECM sees this difference and compesates for it and not always the way we plan. Backfires, sputters,loss of mileage/performance

on the flipside I've heard the a GM motor can tolerate "not saying it's good for it with no cats just that it can run that way" running with no cats. while a ford motor will not operate anywhere close to good without the backpressure created by the cats. I'm talking TBI/EFI only
has anyone else heard that or was someone just blowin smoke my way?

I curently have some 85' stock pipes true duals that came with factory "shorty type" manifolds/headers and 2 straight pipes that went to these huge mufflers that I changed to thrush glasspacks, they are soon to be flowmasters tho I want a deeper rumble and a little more back pressure. Gotta luv the no emmisions inspections in Nebraska