But the very next sentance says... "Just the opposite is true."


It's complicated stuff, I think I'll pay someone to think for me when it comes time to install an exaust on any of my projecs.

 

He also says that the Tornado Fuel Saver "really works", and with a straight face no less.

So much for television heros.

 

Faster and PONY,

Granted the first sentence of the second paragraph may be confusing to the uninitiated but let me clear it up. The Misconception is about the back pressure being needed for optimum performance. Not about headers relieving back pressure. We all know that headers relieve back pressure and the good ones actually create a vacuum in the system. What most people don't know because of the lack of knowledge, or the misconception, is that a little bit of back pressure is good. Plain and simple it is not.

 

yeh theres a reason there show doesnt come on anymore... we have had people come into work saying two guys garage said this tuner for the turbo diesels wont void their factory warranty and is a great safe way to boost power out of our turbo diesels and we just say... well they didnt make the vehicle ford did and read their warranty policy... the product you installed into this vehicle has caused the problems of head gasket to be blown. so no more warranty for you

 

that was my point all along

 

Faster,

You are like a haemorrhoid.

JMC

 

got any cream for me

 

I am by no means an expert, and can only go by what I've been taught, and by several years of experience both in racing and in operating my own automotive repair business.

Some backpressure is a good thing, and I'll tell you why. First off, I need to clarify a few things. Items like mufflers, cats, bends in the pipes, etc. create a "bad backpressure". They are more of an obstruction, than anything else, and removing them will always maintain or increase output power. But things like pipe diameter also create backpressure, but in a good way. A properly tuned exhaust system will create a high velocity in the pipes, which actually helps pull the exhaust out more efficiently at lower rpms. This is why it is assumed that backpressure is necessary for low end torque. If you put 5" pipes, rather than 2.5" pipes, from your collectors all the way back, you would have less power at low speeds because the exhaust velocity would be lower. As rpms rise, the velocity in the pipes becomes less important because the engine gets to a point where it is pumping out more efficiently than it can take in.

Making reference to a top fuel dragster, and it's short pipes, as being the most efficient exhaust is not accurate. Sure, if all you ever do is drive at WOT, that's one thing, but for a daily driver that spends an enormous amount of time at low rpms, a better tuned exhaust will help increase power.

In other words, it is important to properly size your exhaust pipes for better low rpm performance. In the sense that a smaller diameter pipe will create more backpressure than a larger one, backpressure is necessary. Bear in mind, though, items that create backpressure by being an obstruction will not improve power output.

 

I wastrying to diplomatically point out that he was incorrect and cherry picked that sentance.

 

That is the misconception. The correctly sized smaller diameter pipe is not creating back pressure it is creating more velocity in the movement of the exhaust gasses which helps create a vacuum in the primaries which helps scavenge the cylinders.
Just the fact that the velocity increases is an indication that there is no back pressure. What actually happens when you install to large of a diameter pipe is that you reduce the exhaust gas velocity. This reduces the vacuum in the system and that is what reduces the torque. That is why people think that a little back pressure is good. Reducing the pipe diameter is what increases the velocity and hence the vacuum in the system. The correct diameter pipe will optimize the vacuum in the system

JMC

 

Pony,

Understood.

JMC

 

That's pretty much exactly what I said, except that I refer to the smaller diameter pipe as creating a form of backpressure. I should have referred to it as a restriction, which would have been more appropriate.

 

I would question the source. Who wrote it? It is a roadrunner personal site. Is it yours Faster150? Not a performance engineer or exhaust manufacturer.

 

The camera showed the gauge clearly, no camera tricks. The show was not a commercial to sell a product. They were actually explaining exhaust problems and were using a F-150 as an example. They were not selling cat backs or fancy exhausts. They were just explaining function and faults.
Use your brains and think for yourselves.

The tornado has actually been proven to work on some vehicles with Dyno tests. I do not think it will work on our trucks however but that is off the topic now isn't it.

 

This is getting close but still not all of what is happening in a 'tuned' system,
Do a search of all the times people just changed the muffler and felt a loss of torque.
This is NOT due to loss of back pressure.
The queation is, why would one put a muffler on that improves hi rpm power for a towing application?
The factory has designed a stock system for the average 'truck use' of the truck so as to preserve and enhance the torque of the small displacement engine that is already down on torque, for use in these heavey trucks.
Granted, a different muffler and system can improve the mid and high end but that is not what we are talking about in refering to low end power. This is changing the ' acustic' tuning of the system that is the key element.
None of this involves back pressure except to the point of keepng it as low as possible.
No-one has addressed acustic tuning, gas speed, gas temperature, pipe sizes and pipe length (tract length) as a complete design function in these systems.
System tunning is only effective over somewhat a short rpm range when compairing one design to another for torque output. This means you have to pick the system that meets your needs. You either want mid and hi improvement and accept the loss of low or stay with the stock system or a proven system like the Magnaflow that has been tested to at least keep the stock level of torque throughout the rpm range.
But if all that can be thought about is making more noise than improving performance then just put on anything that make the right noise and forget what it does to the engine torque.