dual exhaust

dual exhaust

Postby a2l1 [OP] » March 21st 2011, 5:51am

In an earlier post I expressed my concerns about a smaller tailpipe and was told they had to be backpressure to keep the low level torque at the motor for lower rpm. So the question is pure duals. If the system was pure true duals with a crossover pipe and the cat actually got misplaced during the assembly so there would be 3 inch pipe front to back with a crossover pipe between the two actually the questions are
1, would a system like this requirer a smaller pipe somewhere to create backpressure even with a crossover pipe?

2,Without the cats how would you compensate for the computer? I am sure there would be errors. Could one simply plug into a sensor and tape it up out of the way?.

3 With a big straight thru system wouldnt the exhaust flow faster and easier allowing for more fuel input and therefore a boost in horsepower/performance

If I said hell with it and went to 3 inch duals without cats how does the old 95 run? Is the gas mileage better? Does the motor work less? With the big pipes getting the exhaust out does the engine actually run cooler? What do I do about the computer?

This is the sort of thing I occupy my time with while I am waiting for the meds to kick in so I can sleep. Nite all


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Re: dual exhaust

Postby Phantom » March 21st 2011, 12:20pm

I don't have the time right now to give all the details , but if you went to true duals you should go with
2.25 inch or no more than 2.5 in pipe , the 3 in pipe is larger because it carries both banks of cylinders exhaust ,2.25 in duals will carry more exhaust than the 3in single .
3in pipe in duals you will lose torque , you would need a stoutly built motor to handle 3 in duals , 2.25 is likely to be optimum for a bone stock 4.3 running duals , 2.5 would be the limit. if you search for 'remove cat' or variations you will get a lot of info , there are a few ways that people has configured their van , sometimes it is just setting the ECM.
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Re: dual exhaust

Postby chevymaher » March 21st 2011, 12:20pm

a2l1 wrote:In an earlier post I expressed my concerns about a smaller tailpipe and was told they had to be backpressure to keep the low level torque at the motor for lower rpm. So the question is pure duals. If the system was pure true duals with a crossover pipe and the cat actually got misplaced during the assembly so there would be 3 inch pipe front to back with a crossover pipe between the two actually the questions are
1, would a system like this requirer a smaller pipe somewhere to create backpressure even with a crossover pipe?

2,Without the cats how would you compensate for the computer? I am sure there would be errors. Could one simply plug into a sensor and tape it up out of the way?.

3 With a big straight thru system wouldnt the exhaust flow faster and easier allowing for more fuel input and therefore a boost in horsepower/performance

If I said hell with it and went to 3 inch duals without cats how does the old 95 run? Is the gas mileage better? Does the motor work less? With the big pipes getting the exhaust out does the engine actually run cooler? What do I do about the computer?

This is the sort of thing I occupy my time with while I am waiting for the meds to kick in so I can sleep. Nite all


A J

I am the resident idiot as far as hot rodding and dogging the 4.3.and My opinion(which are like a holes)3 inch way to big for duals.2.25 if you can find it or 2.5 max.2.5 inch a good med performance dual system on a small block which translates into actually being a hair to big for the average 4.3.But it would be fine.As for the O2 sensors put them back in stock locations if you dont have emissions testing you set with no cats.It would throw codes and run great.Mine is par for the course.Everything non-essential disconnected (I should get a reading and post the codes it tossing around)but it runs like a raped ape.I sent you that video of my speedo thats stock whatever it came with engine.It does run a hair better with the single 3 inch into thrush muffler 2.5 inch exhaust.but nothing to write home about.
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Re: dual exhaust

Postby scott936 » March 21st 2011, 2:03pm

chevymaher wrote:
a2l1 wrote:In an earlier post I expressed my concerns about a smaller tailpipe and was told they had to be backpressure to keep the low level torque at the motor for lower rpm. So the question is pure duals. If the system was pure true duals with a crossover pipe and the cat actually got misplaced during the assembly so there would be 3 inch pipe front to back with a crossover pipe between the two actually the questions are
1, would a system like this requirer a smaller pipe somewhere to create backpressure even with a crossover pipe?

2,Without the cats how would you compensate for the computer? I am sure there would be errors. Could one simply plug into a sensor and tape it up out of the way?.

3 With a big straight thru system wouldnt the exhaust flow faster and easier allowing for more fuel input and therefore a boost in horsepower/performance

If I said hell with it and went to 3 inch duals without cats how does the old 95 run? Is the gas mileage better? Does the motor work less? With the big pipes getting the exhaust out does the engine actually run cooler? What do I do about the computer?

This is the sort of thing I occupy my time with while I am waiting for the meds to kick in so I can sleep. Nite all


A J

I am the resident idiot as far as hot rodding and dogging the 4.3.and My opinion(which are like a holes)3 inch way to big for duals.2.25 if you can find it or 2.5 max.2.5 inch a good med performance dual system on a small block which translates into actually being a hair to big for the average 4.3.But it would be fine.As for the O2 sensors put them back in stock locations if you dont have emissions testing you set with no cats.It would throw codes and run great.Mine is par for the course.Everything non-essential disconnected (I should get a reading and post the codes it tossing around)but it runs like a raped ape.I sent you that video of my speedo thats stock whatever it came with engine.It does run a hair better with the single 3 inch into thrush muffler 2.5 inch exhaust.but nothing to write home about.


Lets be clear here, are you running long tube headers, shorty headers or OEM exhaust manfolds and then going to 2.25"
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Re: dual exhaust

Postby chevymaher » March 21st 2011, 2:10pm

No I still got stock exhaust manifolds W style 3 inch exhaust then reducer then 2.5 inch cherry bomb style thrush muffler with 2.5 inch tail pipe.Basically I was just fixin the rotted tail pipe to muffler connection.I wish there were long tube headers for these things but in a pinch shorty would work then into 2.25 duals that would be my choice.When going for it.
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Re: dual exhaust

Postby a2l1 [OP] » March 21st 2011, 3:46pm

Well Im a guy with a bunch of time and very little money so in actuality the duals will probably never happen. I was considering dumping the cat though, something I could do here in the drive and pop in a section of pipe. That wouldnt cost me but a couple of pennies, may even get some money selling the cat at the recycle(junk) yard. If I dont want the codes flashing at me constantly I would have to put back the sensor,correct? Would the lack of a cat actually alter the computer and how it signals the rest of the system?
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Re: dual exhaust

Postby Gary » March 22nd 2011, 12:24am

Any time you don't see me post to a thread that deals with performance,that's NOT a good sign.Might want to do a search on this forum what we covered before. :doh: :banghead:
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Re: dual exhaust

Postby Woodweasel » March 22nd 2011, 12:46am

:angry-soapbox:
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Re: dual exhaust

Postby Gary » March 22nd 2011, 2:49am

Woodweasel wrote::angry-soapbox:


I demand a do over!!!!!. :hand: :nono: :lol: :lol:
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Re: dual exhaust

Postby a2l1 [OP] » March 23rd 2011, 6:12am

Well a do-over is out. I have decided to just stay with the stock setup. It seems to work well enough and I have no need for additional power for the cheater slicks on the back :shhh:

No cheaters just wanted to get a rise out of ya. Take care and thanks,

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Re: dual exhaust

Postby Garpathen » June 28th 2011, 3:31am

ive got an 89 safari, just put a new 4.3 l in it i should have gone smbl v8 anyway i want dual exhaust and i want it yesterday i want it to sound good mean any ideas r welcome!!!
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Re: dual exhaust

Postby redfury » June 28th 2011, 5:46am

Garpathen wrote:ive got an 89 safari, just put a new 4.3 l in it i should have gone smbl v8 anyway i want dual exhaust and i want it yesterday i want it to sound good mean any ideas r welcome!!!


Well, I've got a V8 and a true dual exhaust and honestly, I hate it. It's too noisy and sounds like any other redneck truck out there with a loud exhaust. I should measure the pipes, but they are certainly not small..probably 3".

Removing the cat ( a functioning one ) will do little to improve performance. I had done it on my Dakota with the same muffler I have on my van and a split dual exhaust. I replaced it with a stock exhaust from the Y pipe back and loved it after dealing with the noisy exhaust for 2 years.
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Re: dual exhaust

Postby Phantom » June 28th 2011, 5:12pm

Large capacity High flow mufflers in dual exhaust can be quite , just a higher cost for the high capacity mufflers .

For the 4.3 in an astro if you want duals you will need to find a private muffler shop that will custom bend the pipes for you as there is really no pre-bent offerings from any retail outlet , the only ones i have seen were far too costly , a good exhaust tech can bend them easy , thing is that most shops these days only replace what was offered as oem euip as far as pipes are concerned .

In a astro with 4.3 there is not a whole lot of power to be gained compared to a quality built and setup single exhaust that have pipes contoured to give a moderate increase in power/torque . If you want real duals try to find a small muffler shop far away from any large population where they are not concerned with being audited for what they do to exhaust systems. When I lived n Arlington,TX. and need to get vehicle inspected I drove about and hour one way to some tiny town that put the inspection sticker on my car and only walked around it to check lighting , horn brakes and if the car was quiet , I did not even get out of drivers seat , all done in about 10 minutes , then drove back home :)
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Re: dual exhaust

Postby luckybodog » August 6th 2011, 6:43pm

Hi Everyone
Does the dual exhaust help Horse power,Gas mileage,and over all performance? Removing the cat will that help as well? It sounds good . I don't mean a loud exhaust,I got past that from driving to tech school in my 71 goat had a head ache for two years. Comments? Oh yea how do use those smile things? luckybodog
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Re: dual exhaust

Postby jcmastro » August 8th 2011, 2:51am

Here is a good read that explains exhaust well. For our little 200hp, 2in would likely be overkill. My G8 came rated at 361hp with 2.25 dual exhaust.

http://www.superchevy.com/technical/eng ... index.html
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Re: dual exhaust

Postby cowboydan » August 17th 2011, 5:16am

i'm a firm believer of preformance with emissions. cutting out the cat only handicaps the computer. there are cleaner ways to get preformance. thanks for your words phantom. i couldn't have said it better.
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