Exhaust: Do we really need back pressure?

[Cory_Langford at bcit.ca (Cory Langford)]

Thanks,

This is the kind of information that is really helpful.

I was debating on if I should keep the 2.5 inch that I currently have in
the car (it has a really prepped G60 in it right now), or pull out that
exhaust and put in a full super sprint that I have sitting in the garage.
I think the super sprint is just over 1.5 pipe.  It has the super sprint
resonator and muffler and header with the unit (all nicely welded together
still. So I may just cut off the muffler and see what level the sound is
at. If it is over the dB range, I can slide the muffler back on.

I was planning on wrapping the header, but never thought about wrapping the
entire system.

Would it be beneficial to wrap the entire system to the muffler, or is that
a little over kill?

It is for the 1.7l NA engine, and if I reach 100 hp with what I am allowed
in the class I will be absolutely ecstatic :)

Cory


"brad boston" <boston813roc@gmail.com> wrote on 15/02/2007 05:42:28 PM:

> I agree, the back pressure from a straight though muffler is
> minimal.  I was still at work at that point and in no frame of mind
> to be quantitative, only qualitative :)  If I remember correctly
> this is for your '87 1.7 8v race car? if thats correct you may want
> to go with something a bit smaller than 2.5 inches.  With something
> under 2L making ~100 hp you should be looking in the 1.75 inch range
> if you want to run it all the way to the back of the car.  This will
> keep the gases hot (wrapping the pipe also helps) and will keep the
> flow as constant as possible.  Without getting into tuning the
> length of the pipe (Math) and diameter (More Math). i would say that
> anything between 1.5 and 2 inches is fine and you will see more
> gains from tuning the header.
>
> Brad