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post #1 of (permalink) Old 04-10-2001, 10:40 PM
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New exhaust system affect engine?

I am probably going to get a Magnaflow muffler with one pipe in and 2 out soon(It sounds a lot like a V-8). I plan on getting a 2" or 2.5" pipe, and my questin is: will this modification affect the performance of the vehicle at all? I have heard that the computer has to "re-learn" after the new exhaust system and it might take awhile to do so. How common is this problem? I am just being cautious. Thanks for the help.

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post #2 of (permalink) Old 04-13-2001, 07:17 PM
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Re: New exhaust system affect engine?

What year model and engine size do you have? I have a 97 Blazer with the 4.3L vortec. I had a Flowmaster muffler installed with 2.5" out and I'm still having problems with it. My mileage and performance have both dropped. However, a friend of mine owns a 1990 Jimmy with a 4.3L and installed a Flowmaster and saw an increase in both mileage and performance. Results may very, and in my situation, the computer and/or sensors just don't seem to be making the adjustment to the new muffler. Let me know what you decide or if you have any questions.


post #3 of (permalink) Old 04-15-2001, 05:46 PM
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Re: New exhaust system affect engine?

you may have a problem with the o2 sensor, this may cause the check engine light to come on, and when this happens it causes the mixture to richen and wreck your fuel mileage, if the light dont come on, you are fine. you should see improvement in power and mileage. If it does come on there is not enough restriction. You can cause these computer controlled engines to breathe too well. Good Luck

My truck is not rusty, that's caked on mud. Jason
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post #4 of (permalink) Old 04-15-2001, 07:09 PM
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Re: New exhaust system affect engine?

I have a 70 series Flowmaster, 2.5" in and 2.5" out. My truck runs better and gets better mileage. While I had the old muffler off I decided to run it like that to see what would happen. It still wasnt all that loud but the engine would not idle down properly and going down hill it would fly [img]/wwwthreads_images/icons/laugh.gif[/img]. They need a certain amount of backpressure to run properly. The trick is to get rid of as much you can without getting rid of too much. Good luck.

post #5 of (permalink) Old 04-16-2001, 09:33 AM
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Re: New exhaust system affect engine?

I have a 1997 4.3L Vortec engine. Thanks for the advice guys, I generally have bad luck with vehicles but still think that it is worth it for me to get a new exhaust system. I really want improved mileage and horsepower (I already have a K&N). I have a local shop that could figure the engine light out if I had trouble I think. I am looking at the 40 series Flowmaster now too, but it will be mid summer before I get the system. I wonder if I got 2" pipes as opposed to 2.5" if it would eliminate some possible problems for me. Any input would be helpful. Thanks guys.

post #6 of (permalink) Old 04-16-2001, 02:41 PM
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Re: New exhaust system affect engine?

For One thing Guys Bigger Is Not Always Better On a 4.3 With Singles Exhuast Yes you can run 2.5" pipes but For Bacpressure reasons alot of After market Exhaust sys are made to Flow Alot better the n Stock So Staying with 2" pipes will Keep the backpressure at a point the computer will like and Plus with the after market exhaust your engine will thank you by running longer
As far as the Computer is concerned try This Disconnect the battery For bout ten minut's this will make shure the Computer memory is Clear then hook battery back up start truck up and Drive normally the computer will then Reset itself to the way the engine is running at the time unless there is a major problem one of the sensors is picking up
Hope this helps guys


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