Quote:
Originally Posted by garickman
I am trying to educate myself on vehicle exhaust systems, mainly in the header department. I have searched the internet and various threads but have not found all the answers I am looking for. Most threads are specific to one question and I have several questions. I was thinking a lot of people have some of the same questions I do so I thought I could start a discussion which might address multiple concerns.
How important is the primary tube size?
Very, it will affect torque and horsepower
How do you determine the primary tube size?
I saw a top NHRA engine builder use a flowjet to determine flow at every amount of valve lift, and enter the data into a engineering dynamics software suite and compare it to 3d CAD flow simulation he had modeled with a digital plotter and a lot of time. The average guy can determine the approximate size from the overall characteristics of the engine
How important is it that primary tubes are all the exact same length?
Despite popular belief (and according to GM) not at all
Are stainless steel headers really that much better than mild steel?
No
If stainless steel headers really are better, would ceramic coated mild steel headers be just as good?
Yes
Can you ceramic coat stainless steel headers?
Yes
How come it seems some headers use gaskets and some don't?
They should all use gaskets
Is it a good idea to safety wire header bolts?
That is an application specific question, sometimes yes sometimes no
Do headers effect you torque as well as your horsepower?
How important is the size and length of the merge collectors?
It is the second most important part of the exhaust system
Should the o2 sensors be located in merge collectors?
LONG story short it depends on the exact engine and O2 sensor type, there is a LOT of research on this subject.
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One of the most important things, and why OEM performance car exhausts seem odd sometimes, is the overall system length. As an example the NASCAR Cup cars can find a great deal of horsepower by changing the overall exhaust system length. The flow "pulses" for lack of a better descriptor and you want to tune that flow, in the high end of racing anyways.