• Welcome to the Contour Enthusiasts Group, the best resource for the Ford Contour and Mercury Mystique.

    You can register to join the community.

Best exhaust setup for drag racing.

95_Mystique

Hard-core CEG'er
Joined
Jul 19, 2007
Messages
3,970
Location
Middletown, Pa
I have a spare SVT exhaust sitting in my basement that i'm planning on cutting up to make a drag racing exhaust for the car. My question is, is it best to go with straight pipes, or should i have some backpressure?

Engine/trans info: 3L Hybrid, SVT cams, optimized Y pipe, AEM intake, MSDS headers and Y pipe, UDPs, Torsen.

I was thinking of using a glasspack inplace of the resonator, and straight pipes the rest of the way. Should i run a chambered muffler instead?
 
open headers (or maybe open y-pipe with a turn down). back pressure=bad. another option would be to take the stock exhaust and weld in an electric cutout where the CAT would be (or before). then you close the cutout for daily driving, and open it at the track.
 
I'm no expert, but I'd always heard that some (albeit minimal) backpressure was beneficial on naturally aspirated cars. I never researched it much because most of my cars have been turbocharged.
 
I'm no expert, but I'd always heard that some (albeit minimal) backpressure was beneficial on naturally aspirated cars. I never researched it much because most of my cars have been turbocharged.

Simply having an exhaust manifold creates more "backpressure" than you'll ever need.
 
no exhaust

This. You need about 12" of pipe from the exhaust port to keep oxygen from backfeeding into your exhaust valves, which would be what catalyzes the heat and burns up the valves. Like Andy said, just the stock gutted manifolds would be way more back pressure than you need. Look at all the race cars and drag cars....12" of pipe and no exhaust.
 
well i do have headers, so i guess i'll be doing straight pipes then. I do want to keep an exhaust on the car so i can drive it to the drag strip and not get high on fumes.
 
Anything that causes back pressure is bad. That means something would be restricting air flow equaling less horsepower. This myth of needing some "back pressure" is incorrect. What it's supposed to mean is you gain horsepower from scavenging which is a process that helps pull the exhaust out of the cylinder, and if done correctly based on header length and diameter can net some pretty impressive gains. But thats exactly opposite of back pressure its actually creating a low pressure area to pull the next exhaust pulse out. Running no exhaust will not effect your valves at all but will kill your performance, even stock manifolds will benefit more than nothing at all.
 
Exactly. The length of the headers and tubing size plays a role in this too. My Mustang 357CI windsor....has Hooker 1 7/8" primary tube long tube headers...and they needed 3" OD extension pipes of 12" in length bolted to the collector to get the lowend torque back and get the car to 60ft good (1.50's). So you will need to add some straight pipe to the manifolds....use some gloss black paint first....to see where the exhaust burns the paint to...and thats where you cut the extensions at to gain that lowend back. I am sure the effects would be the same on a CSVT with just headers....they will for sure need some tubing added to get the car to pull out of the hole like it should. And these extensions are for scavenging which was mentioned above...Rad Merc would be correct. Its basically just tuning the header length to get lowend power back.
 
Back
Top