Okay, first of all backpressure in a properly designed primary exhaust
system is BAD. Primary exhaust system is basically the headers and maybe
first 12-18" past collectors.
Now there are a couple of reasons why the reduction in backpressure might
have hurt you
1) A/F ratio - if you are getting more exhaust out and the computer is not
compensating properly then you may end up hurting yourself.
2) Spark timing - if you get more exhaust out you actually typically need
less timing - since backpressure acts like an internal EGR and reduces A/F
charge quality
3) Improper Cam timing / primary exhaust system (stock cam and manifolds).
if you have a crappy setup (like from the factory) then you can loose hp
below your torque peak, though ONLY below the torque peak. This
could be remidied by a better set of headers, which would pick up power
across the board.
Chris Bennight
----- Original Message -----
From: "Mark Kuzia" <flyboy01@mediaone.net>
To: <dakota-truck@buffnet.net>
Sent: Wednesday, July 11, 2001 11:31 PM
Subject: DML: Re: Re: Installed true duals, lost horsepower????
| I'm pushing about 360 hp and 400+ ftlb of torque (300hp & 335tq @ rear
| wheels) with a 360 that revs to 6000+ rpm, I talked to flowmaster and they
| recommended 2 1/2. I really don't think it is too big, I suspect it may be
| the O2 sensor.
|
| Mark Kuzia
| flyboy01@mediaone.net
| http://people.mw.mediaone.net/flyboy01/home.html
| 1995 Dakota 13.79 @ 102.45 mph
| ~360ci, 5-spd, 4.11 LS (8 3/4 [3.90 SG] coming soon)
| 1994 Dakota 15.36 @ 91.56 mph
| ~318ci, 5-spd, 3.90 LS (bone stock, no mods)
|
|
| ----- Original Message -----
| From: "George T. Geissinger" <ustow@ptd.net>
| To: <dakota-truck@buffnet.net>
| Sent: Wednesday, July 11, 2001 10:36 PM
| Subject: DML: Re: Installed true duals, lost horsepower????
|
|
| > I always try to tell my customers that too big is no good. Sorta like
| water
| > running down a pipe too big and the exhaust just sorts "rattles around" on
| > its way out, no scaving effect. too small adds back pressure. I do dules
| on
| > V-6 and 318 in 2 or 2 1/4 if it is HOT.
| > GEORGE!!
| > ----- Original Message -----
| > From: "Mark Kuzia" <flyboy01@mediaone.net>
| > To: <dakota-truck@buffnet.net>
| > Sent: Wednesday, July 11, 2001 10:06 PM
| > Subject: DML: Installed true duals, lost horsepower????
| >
| >
| > > I need some help from those of you who have installed true duals in your
| > > Dakota. I had a set installed today and lost horsepower? I was down 2-3
| > > tenths and about 2 mph in the 1/4 from last week.
| > >
| > > Its a 2 1/2" system, with dual Flowmaster 40 series Deltaflow with an
| > H-pipe
| > > and it dumps out in front of the right rear tire like the Lightnings do.
| > The
| > > bends are not true mandrel bends, but they are smooth.
| > >
| > > I am wondering about the O2 sensor, It is installed in the right pipe,
| > > before the H-pipe. Does this affect how it reads? Please let me know
| what
| > > you did if you have a set on you Dak.
| > >
| > > Thanks,
| > > Mark Kuzia
| > > flyboy01@mediaone.net
| > > http://people.mw.mediaone.net/flyboy01/home.html
| > > 1995 Dakota 13.79 @ 102.45 mph
| > > ~360ci, 5-spd, 4.11 LS (8 3/4 [3.90 SG] coming soon)
| > > 1994 Dakota 15.36 @ 91.56 mph
| > > ~318ci, 5-spd, 3.90 LS (bone stock, no mods)
| > >
| > >
| > >
| > >
| >
|
|
|
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