Headers and Restrictor

[TarekGTR]

A few questions....

-Is the design of the headers influenced by the restrictor?

-Is it better to buy an already fabricated header exhaust or design your own?

-Is there a program that can do flow analysis of headers that you've designed?

[TarekGTR]

A few questions....

-Is the design of the headers influenced by the restrictor?

-Is it better to buy an already fabricated header exhaust or design your own?

-Is there a program that can do flow analysis of headers that you've designed?

[Sam Zimmerman]

The design of our headers is based on the design of the intake, which is based on the gear ratios of the vehicle, which is based on the design of the tracks we run on and the skill level of our drivers.

First look at the courses and your potential drivers. If we had professional drivers I would try to create a torque curve with one huge peak that was just wide enough for the driver to "ride the peak" as they travel up and down through the gears. The lower the skill level of the drivers, the wider the torque peak needs to be so they won't have to shift as much. There are other factors here, but let's leave it at that for now. Once this is established I design the intake based on this information. The exhaust headers are last for me because they are the simplest to design. If they are designed to resonate with the intake, you will get the highest torque peaks and lowest valleys. If you design them to resonate slightly off the intake you will get a wider torque peak with a lower max value and less severe valleys. Of course, the better everything flows (i.e. no sharp curves and the like) the happier you will be.

So in short, your headers are influenced by the restrictor because the intake is influenced by the restrictor. If you buy "already fabricated" headers you then have to design a car around your headers rather than designing headers around your car. There are tons or cfd programs that will be accurate only if the headers you design are the same as the headers you fabricate (not an easy task.)

[Tal199]

Optimum Power have an FSAE package for their Virtual Engines software. This is a 1-D simulation package which is simple to use and runs a simulation in about 10 minutes.

We've used it for a few years now and get good correlation between simulation results and test data. This is a big help for manifold design and there has been plenty of papers published on the underlying theory and applications too.

Their website (http://www.optimum-power.com) gives some more info.

Tal

[MarkG]

Tal,

I'm currently designing our intke system and am trying to source simulation software. I've looked at Optimum Power's website and the software looks allright. What's involved with this FSAE package you're talking about? Did they give you a discount on the software? If they did what was the cost?

Cheers Mark.

[BeaverGuy]

Optimum Power provides the software to FSAE teams at a cost of $100 US per year. This includs a fairly good tutorial that is written for FSAE and base models of an F4 and a single cylinder engine. There is more information on their webpage. If you have good input data you will get a very good idea of what you should get out.

Even though we are using a ZX6R and don't have specific data for certain inputs, like the combustion dynamics, the software is incredibly accurate.

The software was designed by Gordon P. Blair who is the author of Design and Simulation of 2 Stroke Engines and also a book of similar name for 4 stroke engines. In addition to various papers on the subject.

[Tal199]

I should also add that the tech support at Optimum Power is very good since a lot of the guys working there had a hand in developing the software with Gordon Blair.

Tal