Is there any HP gain with just a 4" exhaust and K&N drop in minus the collar?

 

i doubt it

 

In one of the diesel mags they did the test with a series of intakes and exhaust, all there data showed that there are no power gains. It just allows room to grow in the future

 

Don't headers increase HP on gassers?

 

Yes, because they reduce the back pressure.

There is no real back pressure with diesels because they don't create vacuum.

 

My exhaust and k&n made 400+ horses!!!




lol

 

Really? No back pressure? So the power output would be the same between a truck with a 4" exhaust and a 1" exhaust, just the EGTs would be WAY high on the 1"?

 

If you are horribly overfuled air (from intake/exhaust) can add power, mostly because it can let you stay on it longer/harder.

But EGT issues (like would be caused by 1" exhaust) would reduce power, because you would not be able to inject enough fuel to produce boost, and burn lots of fuel without having top back out due to EGTs.

 

A k&n drop in with the boot removed and my 4" exhaust seemed to work great for the dyno pull in my sig. So these mods may not make power by themselves, they will support up to 500 hp

 

Be careful here what you are trying to point out. There is back pressure on turbo charged diesels. With a really good turbo or maybe twins, that back pressure would be about the same as boost pressure or even a little lower. On a stock turbo, it could be almost as much as double the boost pressure.

It is the pressure reduction downstream of the turbo (turbine) that a 4 inch exhaust tries to remedy. Keep in mind that the stock 3 inch exhaust works fine until the engine Hp goes over a certain point. At that piont the exhaust pipe can't flow all the exhaust gas efficiently so pressure builds up.

FWIW many gas turbines operate using differential pressure. The turbine on turbo chargers is one of them. To raise the shaft Hp output the differential pressure needs to be raised. The differential pressure is the inlet pressure minus the exhaust pressure. Raising differential pressure can be done by raising the inlet pressure or by lowering the exhaust pressure. The larger exhaust pipe functions to lower the exhaust pressure of the turbine. That makes the turbine more efficient. The result of higher turbo efficientcy is higher engine efficientcy.

Jim

 

That's what I was thinking. I didn't see how it was physically possible to not have back pressure whatsoever.

 

Basically, horsepower increases in a diesel engine come from adding fuel. The intake and exhaust just provide some additional air to burn that added fuel, but do very little by themselves until fueling mods are made.

The bombing cycle generally runs - add more fuel, then figure out how to add more mass airflow (oxygen) via turbo(s), intakes, exhausts, nitrous, etc. to burn it efficiently. One can always add more fuel to the engine - getting the additional oxygen to burn it is the challenge.

Rusty

 

A free flowing exhaust and kn type filter will often not result in a net higher peak horsepower BUT...it will allow your engine to achieve its max power quicker with faster turbo spool. So basically you will feel your max hp quicker and also have some added torque in the lower rpms.

Another thing that combo will do is lower exhaust gas temps.

 

Nice, now I'm getting some good input, thanks guys!

 

This site always has good input.
I love it.