I just recently replaced my speedo cable and while i was down there i wanted to see how loud rotary exhaust really was. I took off the 2nd precat and took it around the block a couple times and boy was it loud. Anyways i wanted to show my friend so i put it back in without the 2 gaskets and it kinda seemed like i had more top end power. and before i changed the speedo cable i in 5th gear @ 3000 i would be at almost exactly 80mph. but now its like 84-86mph. is this somethin caused by the cable or the leaks?? o ya i have all stock exhaust on an 86na.

 

I'll try to answer that.

Eliminating the "pre cat" with a downpipe will help in overall HP and engine longevity. Once that precat gets clogged you'll notice you engine seems to struggle around 5500-8000 rpms.

You stepping up to a performance "main cat" and catback will also help. The 15-20hp claims are usually on the money if you buy the nicer "matched" full exhaust upgrade like the N1 or HKS.

 

Speed is DIRECTLY related to running gear and rpm.
The only way to change an indicated speed at a given rpm is to change the final drive ratio. This is done through trannmission ratios, rear end ratios and tire diameter.

In other words the change in MPH is due to the cable adjustement. Although removing the pre cat and bassically runnng straight 'headers/mainfold' would give an increase in power, but not an increase in mph at a given rpm and gear.

 

ok i was just wanderin which one did it, i put the precat back in jsut without the gasket because il hopefully be gettin a system soon. the cable im usin now came out of an 88na and i have an 86na.....arent those the same.