1989 Grand Marquis

[DuceAnAHalf]

I've gained horsepower. From my perspective, backpressure is one of the topics often talked about, but seldom understood. Here's a link:
http://www.veryuseful.com/mustang/te...Scavenging.pdf

Read the article. I know that there is a LOT out there about backpressure, so I'm not trying to start a war on this topic. My experience is that I lost nothing and gained some. I would also expect the same response if I gutted my cats, or installed an H-pipe. This article made sense to me. Open headers, you loose torque. Add a length of pipe, you get it back. Backpressure is bad. It seems that just a length of pipe is what helps, not the backpressrue.

If you read the entire article, you will note that in some, very limited applications, backpressure can help the torque/HP at a narrow range of RPM, but will hurt at the higher RPMs.

It is also noteworthy to mention that pretty much all muffler makers design their products to dampen noise with as little backpressure as they can (within the design limits of dampening noise). I've never seen a muffler maker make the claim that "we've kept the minimum backpressure high for your engine".

Johnny (Blaze86Vic) has electric cutouts on his car. he did two 1/4 mile passes, one with full exhaust one with open exhaust. i cant remember the numbers but there was a noticible time difference in both 60' (slower with open) and overall time (faster with open).

[89GrandMarquis]

Johnny (Blaze86Vic) has electric cutouts on his car. he did two 1/4 mile passes, one with full exhaust one with open exhaust. i cant remember the numbers but there was a noticible time difference in both 60' (slower with open) and overall time (faster with open).

I still stand by my original comments.

First, when the cutouts are open, the overall exhaust length has changed, which is one of the technical points made in the article. Longer is better, regardless if a muffler is in the system or not.

Furthermore, with the cutouts, his computer "has learned" what his car needs during normal driving. I realize that in WOT, the computer is no longer in closed loop, but it still uses what has been stored in the tables during closed loop operation. I'm not suprised that the car reacts differently when the exhaust changes, as in when the cutouts are open. It should, since the exhuast system has changed, but the computer has not had the chance to "re-learn". If Blaze86Vic drove around all day, in all conditions with the cutouts open, then made a run with the cutouts closed, he may see a reduction at the dragstrip that is opposite of his current experience.

Anyway, and again, there is a LOT of information out there - the pros and cons of no mufflers.

We can both quote alot of sources to make our case. But for me, until I make further exhaust changes (to install high flow cats), the "no-muffler" approach stays.