For more details check out the video below! Kyle Forster is a qualified Aerodynamicist, race car engineer, and the man behind JKF Aero , a firm that offers a variety of aerodynamic consultancy services for racing purposes. If you have any questions for Kyle or have any suggestions for future videos, drop them in the comments below!
Please enlighten me on the argument of back pressure vs scavenging. The way I am thinking is that you should make the least back pressure and then tune for scavenging pulses. But the common community idea is that it's one or the other. Is there any way to find this out using math or any other method rather than placing your faith in what random people on forums claim? For example, on my GT86, I have the stock exhaust manifold, with the stock primary catalytic converter. Then I have a 3 inch mid-pipe and axle back stock exhaust diameter is 2.
Any input you can provide would be much appreciated. The author seems to be an expert in this field. Why would you suppose he reads forums and writes articles based on random people opinions? I never said that he was on the forums. Tim Rodie. Viraaj Neel Bhatnagar. Topher Crowder. Mark Holgate.
Rachael Hogg. Robert Percy. Engineering brought to you by By. Kyle Forster posted in Mike's Mechanics. Play video. Join In Want to add something? Comments 5 Popular Latest. Dillon Sisk. BrokenRex Member. You must log in or register to reply here. Similar threads. Replies 3 Views Oct 30, civicious. What do we have here? Replies 5 Views Jul 17, phunky. Replies 0 Views 1K. Nov 23, Periculum. How Honda Alternators work. Replies 1 Views 6K.
Jul 15, Dual Honda announces new engine tech. Replies 10 Views Dec 6, awptickes. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register. By continuing to use this site, you are consenting to our use of cookies. Assuming that both the engine and the exhaust system are standard, fully functional and in good condition, the slug of exhaust gas from a cylinder enters the exhaust system in a slightly pressurised condition, and at a speed that is high enough to create a low-pressure area behind it as it races through the system.
Although the tail end of the slug of exhaust gas does decay somewhat as it travels down the exhaust system, it generally does not decay enough to raise the pressure behind it to the point where the slug of exhaust gas that follows would slam into it.
However, how well or otherwise this works depends on-. This relationship is a critically important aspect of any exhaust system design, regardless of the application, since it must represent a perfect balance between the flow capacity of the system and the velocity of the exhaust gas, both of which must in turn, be balanced against the volume of exhaust gas the engine produces. In the days before emissions regulations, none of these factors was particularly important; neither in isolation, nor in combination, but this is no longer the case.
Let us look at the basic requirements a modern exhaust system must satisfy, starting with-. Note that this aspect of an exhaust system is more closely related to the diameter of the exhaust tubing than it is to the length of the system, or the number or restrictions built into the exhaust system. In order for the whole exhaust system to function as an effective scavenging mechanism, the exhaust gas must travel through the system at the highest possible velocity.
For instance, if you have two identical engines running at the same speed, and both exhaust systems are also identical save for their diameters, say 50mm vs. Put simply, this scenario represents a classic case of excessive exhaust backpressure, but instead of improving engine performance, engine performance suffers severely because the exhaust system now chokes the engine to death because it cannot evacuate the exhaust stream fast enough, which begs this question-.
Well, yes, and no. It all depends on the application and its intended use. The point is that since standard engines produce both their peak power and most optimal fuel efficiency between clearly defined points in their operating ranges, their exhaust systems are designed to operate at maximum efficiency precisely at these points in the power band. Of course, this is not to say that a standard exhaust system does not perform well at points below, between, and above these points in the power band.
However, it must be understood that at points below, between, and above maximum power and optimal fuel efficiency, the operation of the exhaust system represents several compromises between effective exhaust gas extraction, fuel efficiency, power delivery, effective exhaust gas pressure, and noise suppression. Any modification of, or alteration to an engine that effects either the volume or velocity of exhaust gas that engine produces has the potential to create excessive exhaust gas pressures that in turn, have the potential to cause severe power losses and other symptoms unless the exhaust system is tuned and matched to the engine.
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