[Ccmano]

:excited: Earlier this year I was contemplating getting rid of my Power Effects system for something with less annoying resonance. It wasn't so much the loundness of the system but resonance that occured in the 1800 and 3200 RPM ranges. I literally had to adjust my driving style to minimize it. After driving the car again more frequently this spring I decided I liked the tone of the system and would just put up with the resonance, usually just driving with the windows open, that seemed to make it at least bearable.

About a week ago, while the wife was out of town, I had a chance to do a few things on the car. One was to clean up the exhaust system and just generally under the rear of the car after I had gotten caught in the rain last year. While it's not a show car, I like things clean. In getting under the back of the car I needed to remove the spare tire carrier and tire to get at everything for the cleaning. What a mess when I pulled it down! There was even an old mouse nest inside the spare.:WTF I decided to just leave it out to save some weight and even removed the brackets that hold the carrier.

I cleaned up under there and now at least it looks presentable when you look under the back of the car. The following day I was meeting up with some fellow ZR1ers about an hours drive from where I now live here in the burbs of Chicago. To my great surprise when I drove the car the 1800 rpm resonance was almost completely gone and the 3200 rpm resonance was much improved! All the way there and back I played with different RPM's (including an encounter with a couple of custom Harleys, boy were they surprised ) I even closed the windows, turned on the A/C and turned on the radio. It was very pleasant. I haven't experianced that since I removed the stock system.

Now I'm not saying the resonance is completely gone, but subjectively, I would say it's 50-75% better.

So here's the question... is this just me? Is it a fluke? Have any of you also noticed this? Does this explain why some people are driven crazy by the resonance on their cars and others with the same car and system don't have a problem?

I'd be interested in some observations from the rest of you. Give it a try and let us know what you think. Am I nuts :crazy: or are we on to something?

Hans
:cheers:

 

[Panther0876]

I had the same problem with my set of flowmasters. I have given up on making it go away. Then I installed my new sterio system and used a little of the Squirt in insulation down where the jack use to be. (Its a speaker box now) The next day.... almost gone. I am thinking that any change you make to the lower area of the car is going to help. Maybe with out the spare in the way the noise gets blown out the back? :huh:

 

[86korvette]

I think it would be improved with the spare tire removed because when you think about it even though the exaust is prety well sealed, the pipes still make movment and vibration. So if the tire/carrier was removed there was less mass to vibrate and it just smoothed out as the car was propelled forward. I never thought of that. Im going to try that soon. It only bothers me because first, if I had a flat I couldnt change it but if I honestly did get a flat, I am NOT getting out to change it. I have AAA. They can bring me a tire and stick it on there I guess. Saftey though. I heard that in a rearend crash the carrier/tire helps cushion a rearend crash and PROTECT the gas tank**KABOOM?** I also know they make a tire deletion kit which cleans it up but still reinforces it to give it more streighth should a backend crash occur. Anyone have any ideas on that or info? It would look alot nicer though. I think RaidMagic did this and painted everything back there.

 

[-=Jeff=-]

Yeah Hans, your nuts..:rolling: j/k

I did not notice a difference when I removed my spare and brackets. Maybe it is a combination of exhaust type, motor and other things.

with mine, the resonance is not too bad unless the A/C is on then it is worse, but with A/C the car is running richer as well. I still need to try my other pair of mufflers

 

[muddpile]

My 84 resonates pretty bad with the stock exhaust, cat cut out and replaced with X-pipe and a pair of Targa mufflers on it. I've often thought about the melrose system with some actual oval mufflers but don't want to drop that much coin if it doesn't help my problem.

 

[crazy4c409]

had the same problem went to home depot spent 18 bucks on some insulation material and layered the back hatch and used some aero turbine resonators car is pretty quiet now, very bearable I love being able to have conversations in my car with the windows up now!