LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

I need Back Pressure..

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Old May 13, 2006 | 11:15 AM
  #1  
93 Trans Am's Avatar
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I need Back Pressure..

..or should i say port velocity? anyways.. i guess some guy stole my muffler the night before last for some reason.. i like woke up in the morning to go to school and notices my car was loud as hell and i was like WTF.. so i look under my car and wondered if my welds broke from when i gutted my cat and those were fine.. so i look in the bck and blam no muffler.. it seems like something really weird to steal but i guess they did it.. so yea now my car is sucking wind in the torque department.. last night i could barely hang with a stock Eclipse GTS.. this shames me.. i was wondering if there would be any sort of quick fix to regain some of that back pressure/port velocity
Old May 13, 2006 | 11:53 AM
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Re: I need Back Pressure..

If you have problems hanging wiht a stock GTS, they go way beyond your lack of a muffler. You dont "need backpressure." If anything, your car has gained power by losing the muffler.
Old May 13, 2006 | 11:59 AM
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Re: I need Back Pressure..

Without the muffler, you are in a similar regard, just running an exhaust cutout. I can assure you that for those of us that are running cutouts, we are not losing power in most cases, but actually gaining a little. As mentioned above, if you lost to a supposedly stock GST, that on paper you should be able to beat, then maybe you should look into other things on your car. Also, can you be certain he was stock? It is pretty easy to turn up the boost on those things and you would never now. Just a few thoughts.
Old May 13, 2006 | 12:00 PM
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93 Trans Am's Avatar
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Re: I need Back Pressure..

Originally Posted by Steve0
If you have problems hanging wiht a stock GTS, they go way beyond your lack of a muffler. You dont "need backpressure." If anything, your car has gained power by losing the muffler.
hmm maybe that sneaky bastard isnt so close to stock then
Old May 13, 2006 | 12:09 PM
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Re: I need Back Pressure..

Originally Posted by 2000GTP
Without the muffler, you are in a similar regard, just running an exhaust cutout. I can assure you that for those of us that are running cutouts, we are not losing power in most cases, but actually gaining a little. As mentioned above, if you lost to a supposedly stock GST, that on paper you should be able to beat, then maybe you should look into other things on your car. Also, can you be certain he was stock? It is pretty easy to turn up the boost on those things and you would never now. Just a few thoughts.
well actually i reaally did win the race but not by much.. we were rollign about 30 and he took off early.. and i mistakingly shifted into 3rd instead of 2nd.. then i dropped it to 2nd and starting slowly reeling him in til i beat him by half a car.. but i still think i should have got him by more than that.. im sure hes not running boost.. i know he has a CAI and exhaust.. maybe he has a few more bolt ons that helped him out

EDIT: i forgot to mention that he also has a few stickers and underglow lights.. so i guess i pretty much jsut answered my question considering these last 2 mods

Last edited by 93 Trans Am; May 13, 2006 at 12:19 PM.
Old May 13, 2006 | 01:39 PM
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Re: I need Back Pressure..

You didn't lose any power. The tuned length of your exhaust changed and the powerband shifted upwards.

Your ride is fine, I promise. The only thing backpressure is used for in LT1 fbodys is EGR valve function, and it's only an issue in OBD2 cars, which yours is not.

And if you think that was bad, wait till you get LTs and true duals. The tuned length of that exhaust is going to be nill and it'll feel like a dog at 2000 RPM. Funny thing is though, even if it feels like a dog, mash on the gas and I guarantee you'll light them up from a roll
Old May 13, 2006 | 01:43 PM
  #7  
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From: Bahrain
Re: I need Back Pressure..

That use to happen alot back when I lived in Corpus Christi. They would still our HKS exaust or greedy setups. I hate thieves. Sure it didnt fall of?
Old May 13, 2006 | 01:46 PM
  #8  
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Re: I need Back Pressure..

how come you didn't weld it together?
Old May 14, 2006 | 11:23 AM
  #9  
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Re: I need Back Pressure..

Removing the muffler, mounted 8-feet away from the engine has no effect on the system. Lack of backpressure helps, it doesn't hurt, and the muffler is so far from the engine it has nothing to do with "tuning" and "power band".
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