back pressure??? - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars
Ford Forum Ford Forum

» Auto Insurance
» Featured Product
ยป Wheel & Tire Center

Go Back   Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars > Ford Cars and PAG Vehicles > Ford Probe Forum | Mazda MX6 Forum
Register Home Forum Active Topics Photo Gallery Auto Loans Garage Mark Forums Read Auto Escrow

Ford Probe Forum | Mazda MX6 Forum Forum for discussion of the Ford Probe and Mazda MX6.

FordForums.com is the premier Ford Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools Display Modes
Old 12-23-2001, 14:18   #1 (permalink)
GTR ProBe PlaYa/Mod
 
Luckys94-GTR's Avatar
 
Join Date: Apr 2001
Location: miami , Florida
Age: 33
Posts: 29
back pressure???

Im currently running pace setter headers with catco high flow catalytic and a greddy stlye muffler. i was wondering what would be more beneficial 3inch cat back madrel bent or 2 1/2. Also considering doing side exhaust like rx7s and eclipses.
__________________
Nos kit(dryset up with purge kit 70 shot)-Ground controls-Ractive intake-Ngk/Moroso wires-Jacobs ignition kit(with custom cap and C4 coil)-Walbro fuel pump-Pacesetter headers-B&M fuel psi regulator-ACT Stage 2 Clutch kit-Catco catalytic-Adjustable carbon fiber wing-6 Stage indiglo's and lots more!!!. Soon to come 18'svolk racing Custom interior.
Luckys94-GTR is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 12-23-2001, 17:08   #2 (permalink)
Registered User
 
Join Date: Dec 2001
Posts: 18
Your engine isn't big enough to need a 3 inch, 2 1/2 will do just fine. And it's not about the backpressure, it's about the flow. If the gases are moving as fast at the end of the exaust as they are when they come out of the engine, this is the ideal combination. If you have big piping the gases will just expand and start to slow down and this goes all the way to the engine making it loose power. Sorta like a traffic jam, except it's the opposite in term of size.
Fantomas is offline   Reply With Quote
Old 12-29-2001, 00:12   #3 (permalink)
Grand Muckety Muck
 
Trey's Avatar
 
Join Date: Mar 2001
Location: SpoCompton
Age: 34
Posts: 710
That is the *perfect* defintion of how the exhaust works, and what happens when people put too large pipe on their cars.

The faster the exhaust flows out the rear the better because as it's flowing out of the car, it creates a vaccuum behind it that sucks more exhaust out of the combustion chambers, making a mroe effective and efficent air pump...errr...motor.
__________________
I have a full tank of Unleaded...
1994 PGT
5 liters and 12 cylinders of fury....
Trey is offline   Reply With Quote
Old 12-29-2001, 22:27   #4 (permalink)
mwild8
Guest
 
Posts: n/a
indeed that is why you have that H connection on your exhaust.
when certain valves are closed the exhaust gasses are just sitting there.. but when the two pipes are connected there is always a vacuume going.... the exhaust sucks itself out, its not pushed.


edit> the 2.5 naturally aspirated engines shouldnt go any more that 2.5inch pipe
turbo, no more than 3inch

if you do the exhaust will lose its flow and wander around in there.. and mess the flow yo!
  Reply With Quote
Old 01-15-2002, 20:50   #5 (permalink)
turbo PGLer
 
Join Date: Dec 2001
Location: Utah
Age: 32
Posts: 46
Finally!! people that understand exhaust. You guys need to go into 1gen forums, esp. on PT to explain this, they don't get it there...
Also another trick, from what I understand, you want the exhaust to go out the side of the car, or just angled in the back?
Angling in the back is an other trick to improve flow. When they come out straight, the turbulent area behind the car slows the whole thing down, too. Angling it allows the exhaust to I guess go "between" the turbulence. Instead of hitting it dead on. And out the sides of the car would be pretty cool too, I mean in looks. Side exits are always good in performance anyways
gxt89 is offline   Reply With Quote
Old 12-03-2002, 09:00   #6 (permalink)
Registered User
 
Join Date: Dec 2002
Posts: 9
The 70 shot of nitrous you are using would benefit from a 3 inch exhaust. However if you did this, any time you weren't spraying you would have a decrease in power, especially in the low end.
__________________
1993 Ford Probe, nowhere near street legal.

I'm "Duddy" on Probetalk.
Armon is offline   Reply With Quote
Old 02-11-2003, 22:17   #7 (permalink)
Just some guy...
 
Gil Starr's Avatar
 
Join Date: Jun 2001
Location: Hollywood, CA
Posts: 553
I'd like to clarify this a bit. Backpressure is needed. I found that in a modded PGT with a 2.5 catback, headers and highflow, I lost lowend but gained massive amounts of high end especcially with N20. Since then I have changed back to the stock 2.25 catback and have seen better launch time and a better lowend. Of course when reaching that transition to mid/highend, without N20, I've noticed the dreaded stock bog return.

You need to know what you want from your car before you start modifying it.

Does this make sense?? I'm buzzed.
__________________
I'm almost done with my website
Gil Starr is offline   Reply With Quote
Old 02-22-2003, 02:47   #8 (permalink)
Old Skool Member
 
Vulcan Power's Avatar
 
Join Date: Feb 2001
Location: Anchorage, Alaska USA
Age: 37
Posts: 1,031
Yeah man it makes sense...

Another thing to mention that alot of people forget. If you have your stock exhaust manifold(s), and a large exhaust the stock exhaust manifolds will provide enough backpressure for a good low end, and the cat-back will provide a decent upper end boost. I have a 2.5" mandrel bent which is probably equal to a 3" regular bent exhaust, but it's a cat-back w/stock headers, etc and the low end response is still very good..
__________________
1990 Ford Probe LX 3.0L V6 :s6:
SEE IT HERE:

1989 Mazda RX-7 Turbo II 13B-T "FC3S"
Turbo RWD Rotary Powa!
Vulcan Power is offline   Reply With Quote
Old 06-05-2003, 08:04   #9 (permalink)
SpeedProbe
Guest
 
Posts: n/a
I have a 3" exhaust on my probe GT.

I ran a 14.4@98mph all motor with I/H/E ze Intake manifold and modified y-pipe
  Reply With Quote
Sponsored Links
Advertisement
 
Reply

  Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars > Ford Cars and PAG Vehicles > Ford Probe Forum | Mazda MX6 Forum



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Auto to manual conversion guide mongrelEB Trans | Driveline 79 12-18-2011 14:27
Oil pressure sender units uteman General Tech 9 05-07-2005 03:21
Manual conversion for 5ltr EB blueoval Trans | Driveline 13 06-03-2003 21:02
302 Oil Pressure Problem Fritz The Cat Cleveland Tech 15 05-15-2003 04:38
TALK FROM THE TOP: Ford Motor CEO cuts costs, not product Stacy94PGT Ford Worldwide News 0 11-18-2002 08:35

Powered by vBadvanced CMPS v3.2.2

All times are GMT -7. The time now is 06:02.



Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO 3.6.0
Garage Plus vBulletin Plugins by Drive Thru Online, Inc.