Whats the diff horsepower wise between 2 cats and no cats on x-pipes?

lafear01 said:

LOL. i'm sorry, but i'm not a 'neck' talker (or whatever the hell your talking about). Now... as for my post, i believe my post was actually quite intelligent. Your ability to quote a 'source' does not make your post intelligent OR creditable for that matter. Sometimes the simple and most direct answers are the best.

I guess if you dont get it, you can try to wow the rest of us here with a nice quote full of BS. lmao.
IMHO, your one of the "grain of salt" posters. As i'm sure anything that you'll be posting in the future will have to be taken with a ............

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You say you had something intelligent to say in your post. When the information I was providing describes how a more free flowing exhaust produces better performance. With that in mind, your saying that 1/2" pipes which will restrict the flow and putting pizza cutters on the back. I'm sorry, but that's sorta lame. I was merely trying to show that this was dicsussed as well as an explanation given that shows how exhaust gases flow. It goes into detail and is more a science than anything. I wasn't trying to blow sunshine up anyone's a$$, I was giving information from someone who knows what they are talking about. So you can discredit me all you want, quite honestly I could care less.

LordJish said:

So after all this yammering, I take it the O/R pipe is still a good thing then?

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As long as you don't have to worry about emissions, Yes it is!!

Blev said:

Do you guys have the exact same mods across the board, with the exception of the exhaust of course.

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Yup the only mods we have on those graphs were just exhaust mentioned above.

Like I said, his car dynoed stock 5 more horses and 10 more torques than my stock dyno. This might be because his car is more broken into (10k+ miles) vs. my fresh 700 miles.

All and all if you don't worry about emission, go with o/r pipes. They both make considerably the same gains.. nothing to worry about much I don't think.

There seems to be a lot of confusion in this thread. Bottom line is that an O/R pipe will yield MORE peak power than a catted pipe. Plain and simple. As stated in a previous thread, backpressure is BAD!! Backpressure does not help produce power. Many people have the term "backpressure" confused with the term "deltapressure". I'll explain:

Some say that "an engine needs backpressure to work correctly." Is this true? No. It would be more correct to say, "a perfectly stock engine that cannot adjust its fuel delivery needs backpressure to work correctly." This idea is a myth. As with all myths, however, there is a hint of fact with this one. Particularly, some people equate backpressure with torque, and others fear that too little backpressure will lead to valve burning.

The first reason why people say "backpressure is good" is because they believe that increased backpressure by itself will increase torque, particularly with a stock exhaust manifold. Granted, some stock manifolds act somewhat like performance headers at low RPM, but these manifolds will exhibit poor performance at higher RPM. This, however does not automatically lead to the conclusion that backpressure produces more torque. The increase in torque is not due to backpressure, but to the effects of changes in fuel/air mixture, which will be described in more detail below.

The other reason why people say "backpressure is good" is because they hear that cars (or motorcycles) that have had performance exhaust work done to them would then go on to burn exhaust valves. Now, it is true that such valve burning has occurred as a result of the exhaust mods, but it isn't due merely to a lack of backpressure.

The internal combustion engine is a complex, dynamic collection of different systems working together to convert the stored power in gasoline into mechanical energy to push a car down the road. Anytime one of these systems are modified, that mod will also indirectly affect the other systems, as well.

Now, valve burning occurs as a result of a very lean-burning engine. In order to achieve a theoretical optimal combustion, an engine needs 14.7 parts of oxygen by mass to 1 part of gasoline (again, by mass). This is referred to as a stochiometric (chemically correct) mixture, and is commonly referred to as a 14.7:1 mix. If an engine burns with less oxygen present (13:1, 12:1, etc...), it is said to run rich. Conversely, if the engine runs with more oxygen present (16:1, 17:1, etc...), it is said to run lean. Today's engines are designed to run at 14.7:1 for normally cruising, with rich mixtures on acceleration or warm-up, and lean mixtures while decelerating.

Getting back to the discussion, the reason that exhaust valves burn is because the engine is burning lean. Normal engines will tolerate lean burning for a little bit, but not for sustained periods of time. The reason why the engine is burning lean to begin with is that the reduction in backpressure is causing more air to be drawn into the combustion chamber than before. Earlier cars (and motorcycles) with carburetion often could not adjust because of the way that backpressure caused air to flow backwards through the carburetor after the air already got loaded down with fuel, and caused the air to receive a second load of fuel. While a bad design, it was nonetheless used in a lot of vehicles. Once these vehicles received performance mods that reduced backpressure, they no longer had that double-loading effect, and then tended to burn valves because of the resulting over-lean condition. This, incidentally, also provides a basis for the "torque increase" seen if backpressure is maintained. As the fuel/air mixture becomes leaner, the resultant combustion will produce progressively less and less of the force needed to produce torque.

I hope this helps to clear up some confusion

THANK YOU SO MUCH SOLID SNAKE

Yes, thank you. I tried to explain it but couldn't so I gave a link to a post were Voldamont discusses this. Now others can simply read your reply. Again, thanks for the explanation.