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Gutted cats, now low high end.

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Old 10-19-06, 11:41 PM
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Gutted cats, now low high end.

I gutted my cats (sloppy welding it back on, and many leaks, due to running out of gas)and it seems to go through my first gear faster, but above 65-70 it is very slow. It used to pull pretty well all of the way to 90 or so. Would the exhaust leaks cause this? Also, not that I'm dying to have it or anything, but.... I heard it would shoot flames, and i hardly have any popping. I'm thinking its probably lean, or it could be leaky cat or clogged muffler, but I definately need a second opinion.
BTW i have a 91' na auto.
Any help is appreciated.
Ryan
Old 10-20-06, 12:11 AM
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well if it ran fine before and now it doesnt with the gutted cats.... i would get the welds right then then see how it runs or y not take the cats off and use a few feet of 2" straight pipe?
Old 10-20-06, 02:16 AM
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sounds like the 5th and 6th port isn't oppening.
Old 10-20-06, 10:26 AM
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^^ that is your problem your 5th and 6th ports open from the back pressure of your exhaust.... search for the 5th and 6th port they make a kit that opens them when need and doesnt rely on the back exhaust pressure
Old 10-20-06, 10:43 AM
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you can also hook them up to run off just the air pump
Old 10-20-06, 11:13 AM
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At one point I had the aux ports wired closed, and the exhaust line that supplies the ports with pressure I had capped (I was in the middle of testing something). The cap developed a crack, and from time to time it would vent. So what I had was a pencil-sized exhaust leak that would turn on and off at random, and my aux ports were wired closed.

The interesting thing is, when the exhaust leak would cut in, not only would the engine sound like a tractor as expected, but I would lose a good deal of power. So, fix the exhaust leaks, and you'll probably kill two birds with one stone (aux ports opening and fixing the issue I'm talking about).
Old 10-20-06, 11:15 AM
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Originally Posted by rx7 FC TII
^^ that is your problem your 5th and 6th ports open from the back pressure of your exhaust.... search for the 5th and 6th port they make a kit that opens them when need and doesnt rely on the back exhaust pressure
To rx7 FC TII: Don't answer if you don't know. Wrong information by unknowledgeble over-confident members is a real problem.


To Bob: You have an S5. Your 5/6 port does not open by exhaust backpressure. It opens by way of the ACV. It is more complicated and more sophisticated than the S4 system, but it is totaly unrelated to your exhaust system. I doubt that the issue you are dealing with involves your 5/6 port, unless you have changed something else, knocked something loose etc.

FSM and the Haynes manual have pretty good trouble shooting proceedure that you can use to determine 5/6 port operation if you want to check this out.

Search is a better friend than the misinformation given to you on this thread.

good luck
Old 10-20-06, 11:35 AM
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Good catch about the S5, I missed that myself. Still, I have experience with power loss due to exhaust leaks (per my post above), so do fix those.
Old 10-20-06, 01:03 PM
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Holy misinformation...

On the S5, the aux ports are opened by the AIR PUMP. Note that this DOES NOT mean the ACV. There is a port solenoid on the rack that opens them up by allowing pressurized air to the actuators...This is all in the FSM...
Old 10-20-06, 01:06 PM
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damnit arron, i was enjoying watching people "explain" the n/a aux port system. why ruin our fun? lol
Old 10-20-06, 01:49 PM
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In Jack's defense, he probably meant air pump anyway. Good catch Aaron, I missed that one as well! Guess I need more sleep - or coffee. Coffee sounds good.
Old 10-20-06, 02:01 PM
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Originally Posted by Aaron Cake
Holy misinformation...

On the S5, the aux ports are opened by the AIR PUMP. Note that this DOES NOT mean the ACV. There is a port solenoid on the rack that opens them up by allowing pressurized air to the actuators...This is all in the FSM...
Thanks for the correction, Aaron: I yield to one of the Masters of the Forum.

I made the mistake of answering very hastily and focused on the misinformation, then spread some of my own.

My humble apologies all around.

BTW, I do know the ACV function from the the vdi solenoid, the port solenoid functions etc.

I even know my ACV from a hole in the ground, but it doesn't seem like it today.

I think I will take a drive.
Old 10-20-06, 02:47 PM
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still running stock mufflers? and btw the flames (for me atleast) only occur between 3k shifts and high rev decelleration
Old 10-20-06, 04:16 PM
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wow.....i guess i was fed miss info also then...i guess thats why i dont own an n/a also...
Old 10-20-06, 04:52 PM
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less backpressure = less torque and that is something you really dont want to lose with an auto transmission.
Old 10-20-06, 05:47 PM
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lol thats y i didnt say anything about back presure bcs its a s5 on the other hand.... i know that leaks in try duels and in headers can act like a cam with uneven lobes and will cause a engine a lil rough
Old 10-20-06, 09:55 PM
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yeah the fifth and sixth ports are opening fine, i really only notice how slow the upper rpms are at high speed, i'll try seeing if sealing those exhaust leaks will do the trick.
Old 10-23-06, 02:57 AM
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hows it running with the leaks fixed?
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