TAT MAN

First time I had the Z28 on the road since I put the true duals on.
before,,, my best time was 12.82 sec in the quarter mile.
Time was done with my Vector FX 1 , yeah, yeah,... I know they ain't all that accurate, but there isn't any time tracks around so its the best I can go by.
Anyway's I got 12.48 this time, at 112. mph. the tires were spinning the first 50 feet,

I be happy.

12.48 1/4 @ 112.7 mph
8.10 1/8 mile @ 89.8 mph
0 - 60 mph 4.1 sec.
60 foot 1.98 sec's

00ls1

congrats dude... .4 is alot of time to pick up from exhaust

TAT MAN

Yup but I'll be alot happier when I get to a track for real time.

Greed4Speed

What other variables were different? Is this compared to a stock exhaust?

Trap speed would be a better comparison.

mrr23

pretty good. here's mine when i went from stock exhaust vs open cutout vs bassani tru-duals.

distance ---stock ----- cutout --- Bassani
60ft ------ 1.987 ------- 2.074 ----- 1.969
1/8 ------- 7.902 ------- 7.912 ----- 7.739
mph ------ 93.20 ------- 93.97 ----- 98.60
1/4 ------ 12.102 ------ 12.080 ---- 11.814
mph ----- 117.12 ------ 118.06 ---- 121.35

bombd84

^ that mph difference is crazy.

Bayer-Z28

Funny, that a slightly different exhaust set up could make that big a difference...

mrr23

the biggest difference is that instead of squeezing all eight cylinders into one pipe, you only have four cylinders per pipe. a dual 2.5" system flows about the same as one 3.5" pipe. also, the bigger the pipe, the slower the velocity at lower rpms. think like the water hose trick. you turn it on full blast. the water comes out in a huge volume. now pinch the hose some. in order to get the same volume of water out, the water has to speed up. the water shoots further and comes out faster.

Bayer-Z28

Would that mufflex 4" sys be a waste of money? Ground clearance? Not enough back pressure? seems kind of big...

Meccadeth

Does the loss of backpressure cause you to lose any gas milage?

mrr23

loose the backpressure mentality. that's a 50s term. it's called velocity and in the olden days they thought it was a 'needed resistance'. think of this. you have a flow supply of 1 gallon per minute at a speed of 10 mph. now a pipe that's 1" in diameter only flows 1/2 gallon per minute. now increase the size to 4" in diameter. it can handle the gallon of water. but, because it's so big, the flow slows to a crawl. now if you were to increase the volume for the larger pipe, then the velocity would increase. again, the old bigger isn't better scenario.

Greed4Speed

And it takes more pressure (aka back pressure or force, which would have to be supplied by the engine working harder to force the exhaust out) to make the exhaust come out at the higher velocity and go further. The key is to find the correct diameter that allows good velocity w/minimal back pressure.

I have the 4" mufflex. Clearance tight but fine. I'll see how it is after I install my springs though. It is overkill for most including mine, but I couldn't pass up the deal. They do make a 3.5" system though.

I still want to see the duals compared to a good catback w/Y instead of duals vs a completely stock exhaust. I'm not saying the duals aren't going to make more power, I just want to know. If I hadn't found the deal on the mufflex that I did, I'd have duals out the back. May yet if I don't go with an STS type set up. I'm dreaming now.

mrr23

the faster the exiting exhaust pulse travels, the more vacuum is created behind it. this is called scavenging effect. with this vacuum behind it, this will 'pull' the next cylinders exhaust pulse out of the chamber. it's about speed of the pulses.

mrr23

when i get the wife's 99 formula dynoed again, you'll see a 3" borla vs the bassani dual. i have the bassani on both cars. the wife's car also has bassani optimum length headers with catted y-pipe. so, you'll have it one day.

mrr23

back pressure is a build up due to the fact the exhaust cannot meet the demands of the engine's output. here, the dictionary definition for you. http://dictionary.reference.com/sear...ack%20pressure
you do not want the motor exerting itself trying to push the exhaust out. that soaks up energy (or torque for engines).

your statement though is correct The key is to find the correct diameter that allows good velocity w/minimal back pressure