Exaust decision insanity....
03-24-2005, 11:51 AM
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Car: 1992 Camaro RS
Engine: 305 TBI
Transmission: TH700R4
Exaust decision insanity....
Ok.. moving this topic here from the General exaust thread, including replies.
The topic got a little too big for that thread, so I'm starting a seperate one.
Origional question:
Figured I'd pose this question, I have a choice to make and I'm not sure what to do.
I've got a 92 RS 305 TBI (L03) and I'm converting it to TPI this summer. But.. before that I need to replace the exaust, as it is currently falling off :/
Currently the car has the single CAT setup on it. I'm wondering, is it worth it to convert to the dual cat setup? And if not I'm having troubles finding a single performance CAT that has 3" inlet / outlet, does such a thing exist?
Thanks for the help.
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The topic got a little too big for that thread, so I'm starting a seperate one.
Origional question:
Figured I'd pose this question, I have a choice to make and I'm not sure what to do.
I've got a 92 RS 305 TBI (L03) and I'm converting it to TPI this summer. But.. before that I need to replace the exaust, as it is currently falling off :/
Currently the car has the single CAT setup on it. I'm wondering, is it worth it to convert to the dual cat setup? And if not I'm having troubles finding a single performance CAT that has 3" inlet / outlet, does such a thing exist?
Thanks for the help.
Replies
Originally posted by Avenger007
Catco and carsound both make 3" in/out catalysts for pretty cheap. There are a few others out there too like dynomax i think and slp has some. Check out summit.
Catco and carsound both make 3" in/out catalysts for pretty cheap. There are a few others out there too like dynomax i think and slp has some. Check out summit.
Originally posted by T.D.K
Ya I just found a bunch on Summit that are 3"
Still wondering about switching from single to dual CAT
Ya I just found a bunch on Summit that are 3"
Still wondering about switching from single to dual CAT
Originally posted by Kevin91Z
GM rated the setup at ten more horsepower. Plus, 4 cylinders flowing thru 1 cat is better than 8 cylinders, right? Just make sure your exhaust guy uses mandrel bent pipe, and uses a true y-design to join them after the cats, and not a t-design like factory.
GM rated the setup at ten more horsepower. Plus, 4 cylinders flowing thru 1 cat is better than 8 cylinders, right? Just make sure your exhaust guy uses mandrel bent pipe, and uses a true y-design to join them after the cats, and not a t-design like factory.
Originally posted by T.D.K
Good point. I have another concern though. With the 305 will I loose any off the line power due to lack of back preasure with a 3" exaust?
I'm goint to eventually put a supercharger on it after the TPI conversion but it may be a while because of the $$$ issue.
So in the mean time will a big exaust like this have any adverse effect on my day to day street driving?
Good point. I have another concern though. With the 305 will I loose any off the line power due to lack of back preasure with a 3" exaust?
I'm goint to eventually put a supercharger on it after the TPI conversion but it may be a while because of the $$$ issue.
So in the mean time will a big exaust like this have any adverse effect on my day to day street driving?
Originally posted by fst2qtrmile
when i did my exhaust, i bolted up hedman headers w/ a 3" collector. Then brought the rest to my buddy. He welded in an )2 provision for my o2 sensor and then reduced the 3" collector to 2.5". Then he built me the Y-Pipe. All manderal bent stainless steel piping. The way he did it, it flows so smooth out of he engine. The Y-pipe runs 2.5" off the headers, then collects into a 3" collector - no cat. Then runs 3" to the flowmaster system. The TPI setups create torque at low rpms and when u run 3" all the way back or even true dual, you will actually loose that torque. Thats why he ran 2.5" then collected into 3". Also, he didnt want to do 3" because of ground clearance. I will get a pic up soon - this Y-pipe is nice. Well just thought i would add my 2 cents.
when i did my exhaust, i bolted up hedman headers w/ a 3" collector. Then brought the rest to my buddy. He welded in an )2 provision for my o2 sensor and then reduced the 3" collector to 2.5". Then he built me the Y-Pipe. All manderal bent stainless steel piping. The way he did it, it flows so smooth out of he engine. The Y-pipe runs 2.5" off the headers, then collects into a 3" collector - no cat. Then runs 3" to the flowmaster system. The TPI setups create torque at low rpms and when u run 3" all the way back or even true dual, you will actually loose that torque. Thats why he ran 2.5" then collected into 3". Also, he didnt want to do 3" because of ground clearance. I will get a pic up soon - this Y-pipe is nice. Well just thought i would add my 2 cents.
Originally posted by T.D.K
Thanks for the good info.
Ok taking into account all that I'm learning here.
How does using Edelbrock headers into CatCo dual cat setup (2.5" inlet/outlet) and 3" the rest of the way back into a flowmaster.
I figure that sounds like it would get the job done. Yes/No?
Thanks for the good info.
Ok taking into account all that I'm learning here.
How does using Edelbrock headers into CatCo dual cat setup (2.5" inlet/outlet) and 3" the rest of the way back into a flowmaster.
I figure that sounds like it would get the job done. Yes/No?
Originally posted by fst2qtrmile
if i were you, i would use your piping from header to cat as 2.5 for clearnce cababilties. I wouldnt even use cats, but if you must, go with 3" because cats will creat enough back pressure as it is - so go with 3" cats. I would run 2.5 headers to cat, then run 3" from cat - making the cats 3"
if i were you, i would use your piping from header to cat as 2.5 for clearnce cababilties. I wouldnt even use cats, but if you must, go with 3" because cats will creat enough back pressure as it is - so go with 3" cats. I would run 2.5 headers to cat, then run 3" from cat - making the cats 3"
Originally posted by Kevin91Z
Dont worry about backpressure, as he said having the cat on there will take care of that.
Edelbrock headers are the worst in my opinion.
Lastly, your questions belong in their own topic, not in the FAQ topic. If you have any more questions, please start a new thread.
Dont worry about backpressure, as he said having the cat on there will take care of that.
Edelbrock headers are the worst in my opinion.
Lastly, your questions belong in their own topic, not in the FAQ topic. If you have any more questions, please start a new thread.
Originally posted by vortec77
Why do you think edelbrocks are so bad?
Why do you think edelbrocks are so bad?
03-24-2005, 12:00 PM
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Car: 1992 Camaro RS
Engine: 305 TBI
Transmission: TH700R4
If the Edelbrocks stink then what would you recommend using.
I wanted to drive out to Summit this weekend and pickup the parts I need so I can start working on this. The decision on what setup to use has become harder instead of easier
There's the dual cat option, but should i go with 3" CAT's and all 3" tubing both before and after the cats or use 2.5" cats and 3" tubing the rest of the way back.
Or there's the single CAT option using all 3" headers back including 3" cat.
Basically, with the 305 TBI I'm looking to get better performance out of the car without loosing any low end power (i.e. back preasure issue). I've heard the argument go both ways, not to worry about backpreasure, or that I do. So I'm confused/lost on the issue.
I will be converting to TPI later this year so I need to keep that in mind, if that makes any differance at all in exaust configuration choices.
I really appreciate the help, I'm still learning all this stuff, and sometimes feel a bit like a moron.
I wanted to drive out to Summit this weekend and pickup the parts I need so I can start working on this. The decision on what setup to use has become harder instead of easier
There's the dual cat option, but should i go with 3" CAT's and all 3" tubing both before and after the cats or use 2.5" cats and 3" tubing the rest of the way back.
Or there's the single CAT option using all 3" headers back including 3" cat.
Basically, with the 305 TBI I'm looking to get better performance out of the car without loosing any low end power (i.e. back preasure issue). I've heard the argument go both ways, not to worry about backpreasure, or that I do. So I'm confused/lost on the issue.
I will be converting to TPI later this year so I need to keep that in mind, if that makes any differance at all in exaust configuration choices.
I really appreciate the help, I'm still learning all this stuff, and sometimes feel a bit like a moron.
Last edited by T.D.K; 03-24-2005 at 12:05 PM.
03-24-2005, 12:19 PM
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Car: '92 RS, '84 Z28
Engine: 383, L69
Transmission: T56, 700R4
Axle/Gears: 3.42, 3.42
Alot of people will suggest Hooker 2055's. There prob the best header. The header primarys are 1 5/8ths on the 2055's, as opposed to a few are 1 3/4. that would prob make a differnce in your low end torque more than pipe size after the collector.
Kevin
Kevin
03-24-2005, 01:40 PM
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Car: '90 RS
Engine: 377 LSX
Transmission: Magnum T56
Gte an entire exhaust sytem for TPI applications. It will work on your 305 and you won't lose any of this mystery "low end" power. You want a full 3" without anything smaller anywhere in your system. People often say that they lose low end power but they are wrong. They are feeling one of two things.
1. Their power band has shifted enough to where their butt dynos have not been recalibrated to the new feel of the car. Track times would would most likely shock them. This same theory applies to people who say LS1's have no low end. They are just impressed with the top end that masks the low end.
2. Full exhausts on 305 TBI's increase the volumetric efficiency by up to 10%. That is huge and enough to make the tune slightly off. Even though it is off you will still see power gains at every point in the curve. We always recomend chip work as soon as you decide to put your fisrt mod onto any TBI set-up. The power of these cars lies in the chip. After headers and afull exhaust the chip should really be tweaked. The parameters are set for an engine that is choked and makes 170hp stock. You are adding a solid 20+hp that is being fed with poor spark and fuel tables. Changing those will make your little car scoot. There are guys with a full exhaust that run mid to low 15's and then there are guys who have nothing more than a cat-back and chip work running 14.5's.
Ok. Look at the Mac's, SLP's or Hooker 2055's. All three have 3" y-pipes with performance characteristics desinged into them. You can then buy a 3" cat of your choice (or get the TPI direct fit cat) and then mate it to a TPI cat-back of your choice. The TPi stuff is no different than the TBI exhausts except that they don't come with any reducer to mate to the 305's wimpy exhaust pipe size.
1. Their power band has shifted enough to where their butt dynos have not been recalibrated to the new feel of the car. Track times would would most likely shock them. This same theory applies to people who say LS1's have no low end. They are just impressed with the top end that masks the low end.
2. Full exhausts on 305 TBI's increase the volumetric efficiency by up to 10%. That is huge and enough to make the tune slightly off. Even though it is off you will still see power gains at every point in the curve. We always recomend chip work as soon as you decide to put your fisrt mod onto any TBI set-up. The power of these cars lies in the chip. After headers and afull exhaust the chip should really be tweaked. The parameters are set for an engine that is choked and makes 170hp stock. You are adding a solid 20+hp that is being fed with poor spark and fuel tables. Changing those will make your little car scoot. There are guys with a full exhaust that run mid to low 15's and then there are guys who have nothing more than a cat-back and chip work running 14.5's.
Ok. Look at the Mac's, SLP's or Hooker 2055's. All three have 3" y-pipes with performance characteristics desinged into them. You can then buy a 3" cat of your choice (or get the TPI direct fit cat) and then mate it to a TPI cat-back of your choice. The TPi stuff is no different than the TBI exhausts except that they don't come with any reducer to mate to the 305's wimpy exhaust pipe size.
03-26-2005, 01:46 PM
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Car: 1987 GTA/1998 Explorer
Engine: 355, trick flow heads, zz409 cam, 3
Transmission: 700r4, shift kit, valve body
Axle/Gears: precision 3.73's, auburn diff
Alot of people will suggest Hooker 2055's. There prob the best header. The header primarys are 1 5/8ths on the 2055's, as opposed to a few are 1 3/4. that would prob make a differnce in your low end torque more than pipe size after the collector.
Kevin
i dont understand, wouldnt 1 3/4 inch primaries flow better, producing better low-mid range torque?
Kevin
i dont understand, wouldnt 1 3/4 inch primaries flow better, producing better low-mid range torque?
03-26-2005, 01:48 PM
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Car: 1984 Z28 Hardtop
Engine: 383 Carb
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The benefit of headers comes from scavenging. Smaller headers scavenge more at low speeds. I agree with ShiftyCapone though, it's not something most people will notice for what it is.
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03-26-2005, 02:09 PM
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Car: 1987 GTA/1998 Explorer
Engine: 355, trick flow heads, zz409 cam, 3
Transmission: 700r4, shift kit, valve body
Axle/Gears: precision 3.73's, auburn diff
so for low-mid torque, 1 5/8th lt's would be best, and high rpm hp say slp 1 3/4 shorties would be best?
03-26-2005, 11:11 PM
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Car: 1987 GTA/1998 Explorer
Engine: 355, trick flow heads, zz409 cam, 3
Transmission: 700r4, shift kit, valve body
Axle/Gears: precision 3.73's, auburn diff
not saying i would need it on a motor like mine, i was just thinking it would give my car a deeper, meaner tone. also, i'm worried about clearance issues with lt's. are there any lts that tuck up under the car? whats the best shorty header for making earth moving torque?
03-27-2005, 02:09 AM
#11
What gives exhaust that aggressive sound is velocity. Headers help achieve that somewhat (and in the process make more power), but most cars actually just sound smoother and slightly quieter with most header designs.
If you want a low tone you need to learn something about acoustic, helmoltz tuning. In a nutshell, a larger tube will decrease high pitched “wind” noise (whistling), but assuming that the tube length stays the same it will raise the tuned frequency of the tube, increasing the frequency of the exhaust note. The 2 ways to lower the frequency is to make the tube longer or smaller in diameter.
If you want a low tone you need to learn something about acoustic, helmoltz tuning. In a nutshell, a larger tube will decrease high pitched “wind” noise (whistling), but assuming that the tube length stays the same it will raise the tuned frequency of the tube, increasing the frequency of the exhaust note. The 2 ways to lower the frequency is to make the tube longer or smaller in diameter.
03-27-2005, 01:06 PM
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Car: 1987 GTA/1998 Explorer
Engine: 355, trick flow heads, zz409 cam, 3
Transmission: 700r4, shift kit, valve body
Axle/Gears: precision 3.73's, auburn diff
alright, i hear a lot of good things about these 2055's on 3rd gens, how is the clearance? right now my car is at stock height, but sitting on 17x9's so actually a bit higher than stock, but i plan on putting eibach springs on to drop it 1.5 or 2 inches. dont like the whole lowrider look, just want a tad lower than stock. think i'd be alright running lt's?
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