Cut out comparision
07-25-2012, 12:30 PM
#1
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Cut out comparision OK, lets try posting here. and i will try to summarize the point
So Im thinknig 3 inch cutouts dupped after the headers before running my 2.5 inch true duals and crush bent overaxel set up.
Mr Luos made a great point by saying he didnt care what power he made with the cutouts capped because at the strip he would run them open
so i believe he made a great point because the cut outs will eliminate back pressure causing more hi end power at the strip and with them closed i will gain back pressure and low end power (that will suffer a bit from the crush bent overaxel piping
however, some are saying i will ultimately loose power thruought the curve because of the cut outs being open....
right now im bolt on but this will someday soon be a 500-600wrhp FI car...
thoughts? dyno comparisions? track time comparisions? anything>?
So Im thinknig 3 inch cutouts dupped after the headers before running my 2.5 inch true duals and crush bent overaxel set up.
Mr Luos made a great point by saying he didnt care what power he made with the cutouts capped because at the strip he would run them open
so i believe he made a great point because the cut outs will eliminate back pressure causing more hi end power at the strip and with them closed i will gain back pressure and low end power (that will suffer a bit from the crush bent overaxel piping
however, some are saying i will ultimately loose power thruought the curve because of the cut outs being open....
right now im bolt on but this will someday soon be a 500-600wrhp FI car...
thoughts? dyno comparisions? track time comparisions? anything>?
07-25-2012, 03:24 PM
#4
My best mph at our local 1/8th mile was 92.4 before the cutout, through the stock catback with a dynomax muffler. 94.2 mph after the cutout with it open. I have LPP 1 3/4" headers and the cutout is located where the stock catback would have met the header y pipe neckdown.
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07-25-2012, 05:57 PM
#8
I really wish I had gotten a graph. We did the back to back runs open and closed just to prove to a friend that the cutouts were worth alot more than just noise. Me and my tuner knew it would make a pretty big difference because when he tuned the car with them closed, opening them changed the A/F ratio almost a whole point leaner.
07-25-2012, 09:26 PM
#10
IMO, they are worthless, if you have a good flowing cat back.
I had a 412ci LS2, it made 519rwhp in 2005 with open Kooks 1 7/8" headers. We put the Magnaflo cat back on with the kooks 3" into 4" Y pipe and it made 512rwhp. Then put dual 3" QTPs and dual Randomtech metallic cats. Put it back on the dyno with the cutouts closed and it made 478rwhp. Open the cutouts behind the cats and it made 511rwhp.
So it still made 511rwhp through the cats for a loss of only 8 hp.
You can only have your tune correct in either open or closed, your pick. I prefer full hp when ever you want it.
BTW, had 5 cutouts fail in one season, 2 different brands. Driving home 40 miles with one failed open. That has to be bad for the motor.
I had a 412ci LS2, it made 519rwhp in 2005 with open Kooks 1 7/8" headers. We put the Magnaflo cat back on with the kooks 3" into 4" Y pipe and it made 512rwhp. Then put dual 3" QTPs and dual Randomtech metallic cats. Put it back on the dyno with the cutouts closed and it made 478rwhp. Open the cutouts behind the cats and it made 511rwhp.
So it still made 511rwhp through the cats for a loss of only 8 hp.
You can only have your tune correct in either open or closed, your pick. I prefer full hp when ever you want it.
BTW, had 5 cutouts fail in one season, 2 different brands. Driving home 40 miles with one failed open. That has to be bad for the motor.
07-26-2012, 07:04 AM
#13
IMO, they are worthless, if you have a good flowing cat back.
I had a 412ci LS2, it made 519rwhp in 2005 with open Kooks 1 7/8" headers. We put the Magnaflo cat back on with the kooks 3" into 4" Y pipe and it made 512rwhp. Then put dual 3" QTPs and dual Randomtech metallic cats. Put it back on the dyno with the cutouts closed and it made 478rwhp. Open the cutouts behind the cats and it made 511rwhp.
So it still made 511rwhp through the cats for a loss of only 8 hp.
You can only have your tune correct in either open or closed, your pick. I prefer full hp when ever you want it.
BTW, had 5 cutouts fail in one season, 2 different brands. Driving home 40 miles with one failed open. That has to be bad for the motor.
I had a 412ci LS2, it made 519rwhp in 2005 with open Kooks 1 7/8" headers. We put the Magnaflo cat back on with the kooks 3" into 4" Y pipe and it made 512rwhp. Then put dual 3" QTPs and dual Randomtech metallic cats. Put it back on the dyno with the cutouts closed and it made 478rwhp. Open the cutouts behind the cats and it made 511rwhp.
So it still made 511rwhp through the cats for a loss of only 8 hp.
You can only have your tune correct in either open or closed, your pick. I prefer full hp when ever you want it.
BTW, had 5 cutouts fail in one season, 2 different brands. Driving home 40 miles with one failed open. That has to be bad for the motor.
07-26-2012, 11:44 AM
#19
You seem to know what you want. I am just trying to tell you the pitfalls, I have tried a lot of them. 1 HC motor, 3 strokers motors and all the stuff that bolts on to them. I like well thought out engineered solutions over hack jobs. I had cutouts too, and tried to do it right, I just realized what a hazard and waste they were. Everyone talked about how great they were, they were not that great.
