[Shotimes] true dual exhaust

[Leigh Smith]

Usually when cars lose power from a better exhaust, it's because the better
flow causes them to go lean. A significant amount of richening may be
required to get the power back. Go tune your low-end fuel curve and you
should at least get the low-end power back.

Actually increasing the mid-range power is a whole 'nother kettle of fish.
The main issue that crops up is scavenging from tuning the exhaust pulses.
I'd bet good money the Yamaha was pretty carefully tuned at the factory,
regarding the cam profiles and exhaust reversion. Increasing it will be
tough. There is just no way a 3.0 L would get any more power strictly from
flow capacity at mid-range, it has to come from the exhaust tuning. It is
always possible to increase the power at mid & high rpm with increased
exhaust scavenging, but it is going to be way more difficult than just
putting on better pipes. Adjusting the fuel curve alone may not increase it,
you may have to go to tuned headers, or custom cam timing, or both. Ted did.
IIRC Ted's car had a lot of modifications like tuned headers, dual exhaust,
custom fuel curves and adjustable cam sprockets. I'm sure it was well
"optimized".

Race cars have juggled header length, tubing diameter, collector size &
diameter, cam lobe timing and fuel curves for years. They can be stronger
than stock, but bolting a race car open exhaust on a car with a stock
carburator has always made it go slower. The fuel delivery has to match the
exhaust.

Lee


----- Original Message ----- 
From: <cmichaelo@optonline.net>
To: "Rick Glass" <rick@pitroadproducts.com>
Cc: <shotimes@autox.team.net>
Sent: Saturday, November 27, 2004 9:05 AM
Subject: Re: [Shotimes] true dual exhaust


> Time for the bombshell question now:
>
> How could TedB get a 35HP gain from his dual exhaust?
>
> I can understand 10HP from the high-flow Y-pipe, and maybe another 5HP
from [obviating] the somewhat restrictive 2 1/4" stock pipe.
>
> But where did the rest come from?
>
> According to his dyno measurements he also noticed a very significant gain
in the mid-range RPM.
>
> And also very interestingly, he also reported that a true dual cat-back
system from a company (Racing Technologies or something...no longer in
existince though) yielded a 25HP gain measured on several SHO cars.
>
>
> Michael
> 94MTX,green,BOS+,Koni/Intrax,Baer,Corbeau
> SHO items for sale: http://hometown.aol.com/cmichaelo/for_sale.html
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