exhaust facts and figures
omega0684 - 4/3/10 at 09:50 PM
evening all,
with my new engine on its way i am looking into a performance exhaust system to optimise the power output. the std exhaust i have at the moment will
be too restrictive and i wont be able to get the most out of my new investment?
the westy owners forum have a group buy on the go at the moment for a Simpson Exhaust package but a complete 4-2-1 package which includes a custom
fitment to your car, headers,collectors, lambda and silencer is well over a grand!
where can i find the information needed for the production of these systems, eg waht length the primaries have to be etc?
All the best
Alex
twybrow - 4/3/10 at 09:57 PM
READ THE BOOK I LENT YOU A YEAR AGO!!! 
omega0684 - 4/3/10 at 09:59 PM
quote:
Originally posted by twybrow
READ THE BOOK I LENT YOU A YEAR AGO!!!
but thats not specific to the pinto!
Steve Hignett - 4/3/10 at 10:17 PM
There are lots of things to read about exhaust performance online...
procomp - 5/3/10 at 12:00 AM
Hi
Ah Now there is one and only one way to get the right system for your setup.
first you have a load of primary pipes made. along with differing length secondaries. You then go and play on a dyno until you achieve the best
results and then have fabricated what made best results. That is how it would be done if your using a high lift profile cam. As there are so many
considerations to be taken into account Not just whether a 4-1 or a 4-2-1 is best.
However if using a std or road spec profile you best bet is to just go for a system that has the right Dia pipes and follows conventional lengths for
a 4 pot. There will be very little pulse tuning to be had so theres not an awful lot to play with. The difference between a 4-2-1 and 4-1 will be
marginal also. Maybe even as little as 3 Hp.
The one thing to get right though is the collectors. A very high percentage of so called performance exhausts are using collectors which are
restricitng performance considerably. Follow the conventional route with the length and desighn for collectors and do not touch anything with these
chap nasty short stubby collectors that most are using.
Cheers Matt
twybrow - 5/3/10 at 10:19 AM
quote:
Originally posted by omega0684
quote:
Originally posted by twybrow
READ THE BOOK I LENT YOU A YEAR AGO!!!
but thats not specific to the pinto!
Since when were there special rules for the Pinto? The book gives fundamental principles on engine tuning and performance. If you want a specific book
on Pintos, then I beleive there is one out there
(here you go), but I can't see why you would... Read the section on exhausts in the book, and then come back and ask the same
question!
What Matt says is bang on, but hopefully some homework can alleviate the need to try loads of combinations in the pursuit of that last HP.
mangogrooveworkshop - 5/3/10 at 12:22 PM
MikeRJ - 5/3/10 at 01:29 PM
quote:
Originally posted by procomp
The one thing to get right though is the collectors. A very high percentage of so called performance exhausts are using collectors which are
restricitng performance considerably. Follow the conventional route with the length and desighn for collectors and do not touch anything with these
chap nasty short stubby collectors that most are using.
I have a book at home "4 Stroke Performance Tuning" by "A. Graham Bell" that states the classic collector design (i.e. effectively
a cone and a plate with holes in for the primaries) is the best design for performance. Since the purpose of the collector is to reflect pulses back
to the port, a larger change in section will give stronger return pulses so this makes sense.
However, merge collectors that give a much more gradual change in section seem to be favoured these days, and I've not read anything that says
why they are better (in other than looks).
Just found an earlier book by Mr Bell here that shows the
same thing on page 116
twybrow - 5/3/10 at 09:27 PM
That is the book I lent to Alex!
Pete Jordan - 6/3/10 at 02:38 PM
Or you could use this online calculator
LINKY
Or buy this calculator for$45
PIPEMAX
Pete