Non-restricted exhaust

[So Cal Mark]

I really like the Hushpower H2 muffs. If you go to the Hushpower website you can listen to the exhaust note on several different cars so that you can approximate what yours will sound like

[grrrdot]

I'll just chime in for the environment and mention that honeycomb catalytic converters have a negligible impact on performance and reduce pollution that cause smog, acid rain all kinds of other stuff.
Unless you have an older bed type converter or your cat is broken/melted focusing on the exhaust manifold, muffler and/or pipe diameter will get you more power gains.

-G

P.S. Plenty of info out there on this stuff..
These guys have a bunch of videos where they test different things like headers vs manifolds, dented headers etc. This one they show how HP changes with exhaust diameter: https://www.youtube.com/watch?v=_PVXvHkr-Vs

[So Cal Mark]

our dyno testing using our header and complete exhaust system show no difference with or without catalyst. We use compact, high flow honeycomb catalysts. In fact, our X1/9 testing showed 1hp more at peak with the cat compared to the non-cat system.
The two big differences are cost of course, and heat from the catalyst

[brackie1]

I hate beating a dead horse but don't want to make costly mistakes. I am looking at the hushpower hp-2 as mark suggested. There seems to be two kinds an 18" I guess replaces the muffler, and one they call a shortie and seems to be a resonator. So the question is, in order to boast performance would you replace current resonator with the shortie or replace the current muffler with the hp-2 muffler?

[brackie1]

Mark
so as you recommended I ordered a Hushpower HP-2 muffler. The question now becomes how to hang it. First of all, the smallest inlet size is 2"id which is what I ordered. Since it is 2" id that would mean it is probably 2 1/8" od, but my current exhaust is 1 3/8" od. What do you uses as a connector piece? secondly, since there is no flanges on the sides of the HP-2 how do you mount it? I am thinking of a wrap around hanger of some sort. Any suggestions would be great.

[So Cal Mark]

if you intend to use the Hushpower with a stock exhaust you'll need to make a connector that is expanded to fit the muff. We usually weld tabs on the side and use the stock hangers

[aevansgatech]

free-flow exhausts are important for power increases, I can't imagine why in your opinion they aren't worthwhile? Exhaust systems with back pressure cause reversion to enter the cylinder during overlap, sapping hp.
Would you care to offer some proof to back up your opinion?

My point was just that it depends on the individual owner's goals for the car. Based on the rest of the thread it's clearly a worthwhile mod for him, but I wouldn't take an all original car and modify the exhaust just for the mild performance upgrade. To each their own!

[carl]

You do realize the stock spider exhausts for a spider is a free flow exhaust in that the muffler and resonator are straight through with no baffles. I think the issue is whether the pipe and muffler core diameters are big enough. I have to say, I am fabulously happy with the two sport exhausts I got from Auto Ricambi. They are made just like the stock system (apparently they are the European spider exhausts). Bolt right on with no hassle and have a 2" diameter core. No silly polished stainless steel or 8" diameter tail pipe and after more than 30 years of playing with spiders I'm done with Ansa mufflers which are too small in core size, weigh a ton and always break where the pipe goes into the muffler. Both systems are on spiders with carbed 2 liter motors using an early 4-2-1 manifold and 1800 stock down pipe.