lost 8 hp with cutout
03-20-2005, 09:29 PM
#1
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lost 8 hp with cutout i dynoed with and without a cutout, i made 291 with and 299 without the cutout. wondering why that would be. also wondering would the cap affect my fuel/air ration?
03-20-2005, 10:21 PM
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Maybe you lost to much backpressure. Its not unheard of for cutouts to have a negative effect, mine however worked to the number of 1/10th off my 1/4 mile time.
03-20-2005, 10:25 PM
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Not sure, but I believe that it does affect the air/fuel ratio a little when it's uncapped. I gained 10 rwhp with the cutout uncapped over it capped up running through an old aluminized Magnaflow muffler that I used to have.
03-20-2005, 11:43 PM
#5
Originally Posted by violator3434
i have my cutout right after my passenger cat, on the right side of the car. would that be a problem? think it would help if i moved it to the i-pipe?
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03-21-2005, 06:25 PM
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Originally Posted by CRL 01 SS
Not sure, but I believe that it does affect the air/fuel ratio a little when it's uncapped. I gained 10 rwhp with the cutout uncapped over it capped up running through an old aluminized Magnaflow muffler that I used to have.
how would it affect a/f?
its exhaust...
03-21-2005, 07:28 PM
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thats wierd... there has to be something else going on... for the most part exhaust systems are restrictive.. a cutout... releases all that trapped air and increases flow yielding to a higher output of gases...
what are the rest of your mods???
was the car dynoed open vs. closed on the same day? has your car even been tuned?
i personally gain about 18-20RWHP with my cutout open..
what are the rest of your mods???
was the car dynoed open vs. closed on the same day? has your car even been tuned?
i personally gain about 18-20RWHP with my cutout open..
03-21-2005, 08:38 PM
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Originally Posted by SiL3NtXWS6
Free flowing exhaust makes your car run leaner, computer compensates with too much fuel
oh right. stupid technology. lol
03-21-2005, 09:23 PM
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Originally Posted by Durien
thats wierd... there has to be something else going on... for the most part exhaust systems are restrictive.. a cutout... releases all that trapped air and increases flow yielding to a higher output of gases...
what are the rest of your mods???
was the car dynoed open vs. closed on the same day? has your car even been tuned?
i personally gain about 18-20RWHP with my cutout open..
what are the rest of your mods???
was the car dynoed open vs. closed on the same day? has your car even been tuned?
i personally gain about 18-20RWHP with my cutout open..
i went to the muffler shop today, and had him move the cutout to my i-pipe there was a spot that looked like it was perfect for it. its alot quieter now and makes a ugly noise when i take off from idle. also he replaced my driver side pipe that was all flatten with a bigger round pipe. he said it should help the it flow more.
hope this will help my power out now, its hard to tell what im making just driving it.
03-22-2005, 12:07 PM
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Originally Posted by mike c.
dude,you put the cutout on only one side of your exhaust? 
mine is at the end of my y- pipe. i gained 9hp and 8tq when opened. the new set up should help you.
mine is at the end of my y- pipe. i gained 9hp and 8tq when opened. the new set up should help you.noticed any change in e.t. with or without cut out.
I consider it an exhaust sound mod.
03-22-2005, 12:31 PM
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when i put my dual cutouts in it seemed like everyday it ran a little stronger for about a week. then it still ran a little rich, but not enough for me to spend the money for a tune........i'll pry get it tuned this spring.....with the pcm, i don't think you'll get the full performance effect if you just uncap it at the dyno(without tuning) or the track, the pcm takes a while to adjust to it.....that's what i've gathered from talking to a few people and my personal experience, i don't have any technical info to back my opinion up.....
03-22-2005, 03:16 PM
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If you drive around with the cutout open, the PCM will set LTFTs to compensate and you're likely to run the same or worse than before.
If you are running on the rich side corked up, and then only uncork when you are making a pass, then you'll definately gain significant power.
To avoid bad reversion at the lower RPMs you mount the cutout as far away from the engine as possible.
To the original poster, why in the world are you running CATs in the first place?
If you are running on the rich side corked up, and then only uncork when you are making a pass, then you'll definately gain significant power.
To avoid bad reversion at the lower RPMs you mount the cutout as far away from the engine as possible.
To the original poster, why in the world are you running CATs in the first place?
03-22-2005, 03:59 PM
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i just read what i posted and i didn't write it very cleary.....everyday for a week after i went to the headers and open dual cutouts it kept running stronger, never did it stop running good(other than a little rich). what i meant was that it seemed to take that long for the pcm to get used to all the extra air flow. i'm actually afraid that if i get a tune with the cutouts opened that it will effect the tune if i then close them for a while....maybe that shows my ignorance right there....
i think the first poster had cats because he was in california
i think the first poster had cats because he was in california
03-23-2005, 09:15 AM
#19
I gained ET & MPH testing mine on back to back runs at the track.
BTW, back pressure is NOT good. Any time you get rid of back pressure you'll get a performance increase so long as the tuning takes the change into account.
A single cut-out on the I-pipe almost always works to increase performance on our cars. To loose power is very unusual, even when the tune is unchanged.
BTW, back pressure is NOT good. Any time you get rid of back pressure you'll get a performance increase so long as the tuning takes the change into account.
A single cut-out on the I-pipe almost always works to increase performance on our cars. To loose power is very unusual, even when the tune is unchanged.
03-23-2005, 10:28 AM
#20
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Originally Posted by Ragtop 99
I gained ET & MPH testing mine on back to back runs at the track.
BTW, back pressure is NOT good. Any time you get rid of back pressure you'll get a performance increase so long as the tuning takes the change into account.
A single cut-out on the I-pipe almost always works to increase performance on our cars. To loose power is very unusual, even when the tune is unchanged.
BTW, back pressure is NOT good. Any time you get rid of back pressure you'll get a performance increase so long as the tuning takes the change into account.
A single cut-out on the I-pipe almost always works to increase performance on our cars. To loose power is very unusual, even when the tune is unchanged.
Yeah, if anything, a cutout will give you a higher peak tq (yet higher in the rev range), therefore one feels like there's a loss of tq down low, but in fact, the car is making more peak tq overall up high (where it needs it for track times).