No Cat & no mufflers!

[nelson84]

I have decided to go with no cat and no mufflers on my 85 vette. My 84 has a random cat and muffler eliminators. I took the mufflers off my 85 with no cat and it sounds the same. The random cat doesn't muffle any sound. I will be putting on muffler eliminators, for sound and I am also on a budget($190).

Anybody have thoughts on this? Or has anybody have this setup? What would be louder regular muffler eliminators or the ones with the indents in the pipe, baffled I think they call it.

 

[tcxd40]

Engines are designed to operate with some back pressure. By eliminating all restrictions your low RPM performance may suffer.
tcxd40

 

[nelson84]

What about race cars they don't have anything, no cats and no mufflers? Would they be faster with them installed?

 

[Edmond]

What about race cars they don't have anything, no cats and no mufflers? Would they be faster with them installed?

Can't answer that question but race cars aren't designed to be driven every day in our every day conditions. Plus, race car engines aren't expected to have long lives.

Heidi commented on an engine having no back pressure from her experience a few years ago. Hopefully, she'll chime in with her experience.

 

[G Winter]

Upper RPM range should be better but like tcxd said , the lower RPM could suffer power loss. A trade off where you want your power.

Glenn

 

[tcxd40]

I don't remmeber all of the engineering.
However from personal experience. I Modified my 454 with new intake, fuel injection camshaft and a free flowing exhaust, too free flowing. After the adddtion of the headers and exhaust pipes. I had no low end performance. The factory set up was 2 1/4 inch pipes. I installed 3 inch pipes from the headers to the mufflers. The vehicle fell flat until the RPMs rose to about 3800 RPM. I later found out the there is a required amount of back pressure needed at low RPM. Once I re-piped the exhaust to 2 1/4 it as like a new car.
tcxd40

 

[nelson84]

On a TPI engine it is already designed for low to mid range power with the long runners so I think with less backpressure, it would help in the higher RPM's and still retain the low end power.

 

[Toms007]

On a TPI engine it is already designed for low to mid range power with the long runners so I think with less back pressure, it would help in the higher RPM's and still retain the low end power.

Your reasoning sounds good, but, I don't believe it's actually works that way. I saw, somewhere (I can't remember where), where someone did just what you are talking about and they actually saw a low end performance drop (IIRC they had dyno sheets). I would do a bit more research before doing this.

 

[MR NICE]

It will sound like a old junk truck,IMO

 

[TedC]

Look at exhaust back pressure as just another component you can tune. L98s were designed to produce a strong torque curve between 2200 and 4200 RPM. I would suggest that some back pressure is required to maximize torque in the lower RPM ranges. When you reduce exhaust back pressure you shift the torque curve to higher RPMs. There is room to improve the exhaust on a stock L98, especially those that use mass air (MAF) technology (1985-89) without ECM changes. Just understand the impact of torque curve changes on your overall performance. I've tried all kinds of mufflers on my stock 1988 (auto, 2.59, air foil, open air cleaner lid), and found straight pipes and muffler eliminators actually hurt launch and 1/8 mile performance. I actually lost the 1st to 2nd tire chirp at WOT which came back after installing mufflers with 4 open ports.

 

[mendesb]

Bigger throttle body is needed

Your reasoning sounds good, but, I don't believe it's actually works that way. I saw, somewhere (I can't remember where), where someone did just what you are talking about and they actually saw a low end performance drop (IIRC they had dyno sheets). I would do a bit more research before doing this.

My mechanic told me you need to increase the air flow from the filter and install a bigger throtle body. I just took out my big cat and I am running straight pipes. It sounds good and I haven't noticed any power shortage. Of course I need a clutch and trany so it's hard to tell