Before I forget, if you have the PRE-CATS installed on your truck the gain
from JBA shorty headers are only 9HP. If you don't have the Pre-CATS, then
the long type headers are up to 21HP gain. These were the figures given to
me from JBA engineers while they prototype the headers units.
--------------------------------------
Steven St.Laurent
C4i System Engineer
C4i Engineering Branch, PSD, MCTSSA
MARCORSYSCOM, U.S. Marine Corps
Office (760) 725-2506 (DSN Prefix: 365)
"Never be content with somebody else definition
of you. Instead, define yourself by your own beliefs,
your own truths, your own understanding of who
you are. Never be content until you are happy with
the unique person GOD has created you to be."
-----Original Message-----
From: crm [mailto:tb.crm@verizon.net]
Sent: Wednesday, May 29, 2002 11:52 AM
To: dakota-truck@dakota-truck.net
Subject: Re: DML: Exhaust bottleneck?
excellent info Jay! i think after reading this and talking to a buddy up
here at work i'll wait till i can get the 3" cat-back. i figure that the
larger pipe might not do as much good now but down the road (after a couple
more mods) it will definitely be called for. no sense putting something in
that i'll have to replace a couple months later...
now i just need to decide on the muffler...the quote from the muffler shop
was for a $135 magnaflow, i guess i could knock $50 (or more?) off that
price if i took one in there myself.
thanks again guys!!
-adam
----- Original Message -----
From: "Woodruff, Jason P" <jason.p.woodruff@boeing.com>
To: "DML (E-mail)" <dakota-truck@dakota-truck.net>
Sent: Wednesday, May 29, 2002 12:18 PM
Subject: Re: DML: Exhaust bottleneck?
>
> Main exhaust bottleneck? In my opinion the whole thing.
>
> First I made a po'boy air intake Z tube, I felt a little more HP, probably
> mostly do o the colder air. Next I replaced the cat back exhaust system
to
> a single 3" and found that to increase throttle response AND torque
> substantially. Then I replaced the intake and Throttle Body with a real Z
> tube and F&B TB. Throttle response went way up, HP went up on anything
> above 2K RPM, but low (really low) end torque diminished a bit. I
wouldn't
> recommend that last one if your looking to tow a lot. I have a set of JBA
> headers in my bed room that I'm not sure if I'll ever get to put on, but I
> suspect they'll have the same effect as the TB change.
>
> I think there's 3 cats on 4.7Ls (except 2000 non-cali daks). one on the
end
> of each header then one further downstream after they've merged.
>
> Jay W
> 505/287 Dakota
>
> >Date: Wed, 29 May 2002 10:02:01 -0500
> >From: "crm" <tb.crm@verizon.net>
> >Subject: DML: Exhaust bottleneck?
> >
> >Hello all,
> >
> >Can someone pinpoint the main exhaust bottleneck for a 2001 Dak QC with a
> >4.7? After doing a lot of reading (here and elsewhere), I seem to be
> running
> >into 2 or 3 differing points. One the one hand, many seem to suggest a
new
> >muffler will really free up the exhaust. One the other, I have heard that
a
> >new muffler wont do much because the main bottleneck is at the cat. And
> then
> >on the 3rd "hand", I have read that if you dont replace the stock 2.5"
> pipes
> >with a 3" catback, neither hi-flow muffler nor hi-flow cat will help. And
I
> >guess to round it all out (4th hand), I've heard that the 3" pipes will
rob
> >you of low end torque, which is what you need for towing and the like
> >correct?
> >
> >If it makes a difference, I dont use the truck for towing. Mainly for
> >driving to work and around town and the occassional day trip. No racing,
> >other than the normal youthful exuberance on the freeway or at the light.
> >Basically, I am not looking to build a mean street rod or anything, just
a
> >truck that can sh*t and git if I tell it to.
> >
> >I dont want to spend money for the same thing 2 times, so I want to make
> >sure I do it right the first time. I just ordered a Z-tube last night and
> if
> >I can figure out what's best I hope to get some exhaust work done this
> >weekend. I'd like to use stock pipe if possible and avoid getting a whole
> >new catback system until later on.
> >
> >Also, is it correct that the 4.7 Dak's have 2 cats? Like a pre-cat and
then
> >a main cat?
> >
> >Thanks in advance!!
> >
> >- -adam
> >
>
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