I know my exaust but I am not very familiar w/ back pressure, so if all of you exaust guru's can shed some light on this dilema of mine that would be great.

My exaust consist of:


Edelbrock TES 1 5/8th's headers with a 3" collector, the Y-pipe is 3" from the header collector, then turns into a 2 1/2 inch pipe until it connects to the Y-section of the pipe, from there it's 3", the Y-pipe connects to my stock gutted cat & exaust wich is 2 3/8th's. by the muffler I have a cut out to bypass my muffler for an open exaust setup.


My girlfriends dad was telling me that with the exaust setup I have and the fact I have an open exaust cut out that I have lost all of my back pressure and my car just ended up getting slower because these engine need some back pressure to function at peak performance, i know a little back pressure is always good, but then again I do not have 1 3/4th headers and a full 3" exaust... I personally think he's full of it.


I'd like to know if My exaust setup is to free flowing and if I shouldn't run the car @ the track with my cut out sealed up.


any info is appreciated.

 

And if you guys are interested in my intake mods, I have a gutted dual snorkel setup, gutted maf, fully ported & siamesed plenum, and slp Siamesed runners.

 

first of all you cut is the wrong place. basically, cutouts need to go as close to the engine as they can. in your case, right where the y-pipe comes together, before the cat. you have almost defeated the purpose of a cutout, well not quite, but you arent gaining the full benefit of the cutout.

anyway, you dont want any back pressure...what you dont want to lose is the exhaust velocity and scavenging.....hopefully some one more scientific which explaint the science to you.

also, that i-pipe is not helping the situation both when the cutout is capped and when it is open. what kind of muffler do you have? cause a stock muffler and stock i-pipe are still a bottleneck.

 

There was a long debate over this earlier.

Basically, you want an exhaust that is matched to what you want your engine to do.

If you want an exhaust that will work efficiently from 5000-6500 rpm, you are going to sacrifice exhaust velocity down low (large tube headers, dual 3" or bigger).

At the same time, if you want an exhaust that works efficiently in the 2000-4000 rpm range (like a tpi car), then you are going to want to keep that low end exhaust velocity (medium to small tube headers, not too crazy on the exhaust tubing size).

Back pressure will come into play when your exhaust is no longer efficient, so if you want your exhaust system efficient down low, back pressure is going to come into play in the upper rpms when your exhaust system is no longer efficient.

 

I gained 21rwhp and 8rwtq on the dyno in 2nd gear, just by opening my cutout (before cat). I am running Edelbrock TES 1 5/8 headers, Edelbrock TES 3" y pipe with 3" cutout welded before cat, Catco high flow cat, and stock catback with Flowmaster Force2 muffler.

Although some cars might not benefit as much as I did, I do beleive different engines need different exhaust setups, depending on heads/cam/and intake selection.

 

Backpressure is NEVER good.... ever... period.

 

No, but if you are shooting for low end torque then you will encounter back pressure top end.

 

when I bought the vehicle the previouse owner welded the custom cut out in himself right before the muffler. When I get a real cat back exaust setup, I'm going to install a cut out where the y-pipe meets the cat like you all recommend.

thanks for the info guys.


And I'm not sure off hand what exaust muffler it is, if i'm not mistaken it's an SLP muffler.