cutouts. worth it?
Originally Posted by Colonel
"first pull was with all closed
2nd pull was with just the back one open
3rd pull was with all 3 open."
I hope you take this in the helpful manner in which it's intended but here's a suggestion so that you get a more accurate understanding of what really happened.
1. Get the engine and drivetrain (drivetrain takes longer) up to normal driving temperature. This means driving it for a good half hour I would think.
2. Dyno 4 pulls with the single cuttout open. Take the highest reading.
3. Allow the engine to cool back to the starting temp of the first pull.
4. Dyno 4 pulls with all three cuttouts open. Take the highest reading.
Be sure to use a diagnostic scanner to monitor timing advance and O2 readings. Better yet, use a wideband. Keep the fuel/air mixture between 13:1 and 13.3:1.
I think you'll see that there is little to no difference in power between 1 and 3 cuttouts UNLESS you have a restriction between the 2 cuttouts and the single, such as a restrictive sized I-pipe.
2nd pull was with just the back one open
3rd pull was with all 3 open."
I hope you take this in the helpful manner in which it's intended but here's a suggestion so that you get a more accurate understanding of what really happened.
1. Get the engine and drivetrain (drivetrain takes longer) up to normal driving temperature. This means driving it for a good half hour I would think.
2. Dyno 4 pulls with the single cuttout open. Take the highest reading.
3. Allow the engine to cool back to the starting temp of the first pull.
4. Dyno 4 pulls with all three cuttouts open. Take the highest reading.
Be sure to use a diagnostic scanner to monitor timing advance and O2 readings. Better yet, use a wideband. Keep the fuel/air mixture between 13:1 and 13.3:1.
I think you'll see that there is little to no difference in power between 1 and 3 cuttouts UNLESS you have a restriction between the 2 cuttouts and the single, such as a restrictive sized I-pipe.
i have a custom y-pipe made with no cats and with a cutout on each side of the y-pipe and then the cutout on the i-pipe and stock muffler. ive always gained about 15 rwhp with just the cutout on the i-pipe and this is my first dyno since having the 2 on the y-pipe. my a/f ratio was around 12.5 on all pulls. the car was fully warmed up. i always make sure espcially with the white one because of the cam and heads it has and the electric water pump.
thanks for the input
It is worth it, cheap hp mod! I didn't dyno with it capped, but I'd say probably 10 rwhp on a stock car. I made 302 rw w/ a lid & cut out on a '98 Z A4. Car definately has more top end pull with it uncapped.
Originally Posted by pdd
i decided not to get them. emissions seems like a problem up here in mass
Dope
TECH Enthusiast
Joined: Jan 2002
Posts: 531
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From: Helendale, Ca (SilverLakes)
I only picked up a tenth (.10) and half a mph at the track over the stock exhaust. Don't even use it anymore. Don't know what the dyno#'s were.
Last edited by highgear; Jan 22, 2004 at 03:44 PM. Reason: spelling
