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Old 11-22-2009, 04:50 PM
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Gains/Losses w/SRT exhaust on WK 3.7?

I've had the SRT exhaust set-up on my 3.7 Laredo for a few weeks now and for some reason to me it seems to "lag" from stopped to giving it gas, like it hesitates. I deleted the muffler and added a Y pipe going back to the srt dual pipes over the axle to the two srt resinators out the rear. It does seem quicker on the highway when passing though compaired to my previous Magnaflow cat back exhaust. I've been searching online and have heard now that i have no muffler and two larger pipes there is now less backpressure and that "might" be bad for the exhaust valves and my performance might be down now. I did come across this post on a BMW site that kinda made sence.

Myth.

Modern BMWs don't have to worry about the effects of reduced backpressure, because the DME (car's computer) that controls the engine will detect that the engine is burning leaner than before, and will adjust fuel injection to compensate. So, in effect, reducing backpressure really does two good things: The engine can use work otherwise spent pushing exhaust [COLOR=blue !important][COLOR=blue !important]gas[/COLOR][/COLOR] out the tailpipe to propel the [COLOR=blue !important][COLOR=blue !important]car[/COLOR][/COLOR] forward, and the engine breathes better. Of course, the DME's ability to adjust fuel injection is limited by the physical parameters of the injection system (such as injector maximum [COLOR=blue !important][COLOR=blue !important]flow [COLOR=blue !important]rate[/COLOR][/COLOR][/COLOR] and fuel system pressure), but with exhaust backpressure reduction, these limits won't be reached.

Older [COLOR=blue !important][COLOR=blue !important]cars[/COLOR][/COLOR] with carburators, could run lean due to reduced backpressure, and without adjustment, could lead to bruned valves in some cases, but outside of that, the slightly reduced backpressure of removing resonators or mufflers from an otherwise full length exhaust does NOT reduce torque, even a little bit. IN fact, it can often INCREASE power and torque, due to less restriction and better exhaust flow. If reducing backpressure reduced torque, then no reputable engine [COLOR=blue !important][COLOR=blue !important]builder[/COLOR][/COLOR]

would build or install free flowing cat-back exhaust systems or higher flow exhuast headers.


One thing I havent done is dissconnect my battery, thinking that might make the cars computer reconfigure itself for the new exhaust. Im lazy and dont want to reset all my stereo settings, but would it be a good idea to dissconnect the battery or would my cars computer already have reconfigured itself by now with the new exhaust?
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Old 11-22-2009, 04:54 PM
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Re: Gains/Losses w/SRT exhaust on WK 3.7?

Also, would making a true dual exhaust, meaning after the headers and cats weld on pipes that go back to an X pipe to the srt dual exhaust, deleting the single pipe I have in there after the cats have a better effect?
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Old 11-22-2009, 05:32 PM
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Re: Gains/Losses w/SRT exhaust on WK 3.7?

great find and it all makes sense
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Old 11-22-2009, 05:45 PM
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Re: Gains/Losses w/SRT exhaust on WK 3.7?

hmm,
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Old 11-22-2009, 05:51 PM
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Re: Gains/Losses w/SRT exhaust on WK 3.7?

ok ur second post didn't make sense ... but resetting ur jeep ... I heard from a mechanic that after 40 resets of ur vehicle meaning turning it on and off ur car will automatically adjust and reset to itself to any new thing added ...
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Old 11-22-2009, 06:02 PM
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Re: Gains/Losses w/SRT exhaust on WK 3.7?

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Originally Posted by boniomario View Post
ok ur second post didn't make sense ... but resetting ur jeep ... I heard from a mechanic that after 40 resets of ur vehicle meaning turning it on and off ur car will automatically adjust and reset to itself to any new thing added ...

My second post where I wrote about making it a true dual exhaust? If so, I meant instead of how the headers on each side of the motor go to one pipe I cut that off and have a single pipe coming off each header, just like the SRT exhaust. It shouldnt be that expensive to have done im thinking, and if it would free up more exhaust flow it might be worth looking into.
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Old 11-22-2009, 06:07 PM
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Re: Gains/Losses w/SRT exhaust on WK 3.7?

sounds like a really good idea, and of course would free it up and make it better for the engine to breathe.

If you can do it on your own I would say that's the way to go.

I was thinking about doing the same thing to once I bolt on a turbo to my 3.7 setup.

My mechanic friend did a job like that once where he split the header exit pipes to make it into dual exhaust, it took him half a day to it with the right parts.

fyi a lot of people might say it's not worth it but I am firm believer in doing what you think is right for your car
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Old 11-22-2009, 06:19 PM
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Re: Gains/Losses w/SRT exhaust on WK 3.7?

I would want the pipes welded on after the headers so its not something i can do myself. I'd get all stainless steel, so I never have to worry about going under there changing out rusted pipes ever. I was just under there yestarday and think there is enough room to install the two pipes, as its done the same way on an SRT basically.
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Old 11-22-2009, 06:22 PM
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Re: Gains/Losses w/SRT exhaust on WK 3.7?

I told you about the true duals, you did not listen...

the burnt valves is BS, that comes from a lean AFR....
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Old 11-22-2009, 07:28 PM
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Re: Gains/Losses w/SRT exhaust on WK 3.7?

Quote:
Originally Posted by Sleepy4.7 View Post
I told you about the true duals, you did not listen...

the burnt valves is BS, that comes from a lean AFR....

You told me?? Lol. Whats an AFR? And I was really not worried about the burnt valves myth with my WK because of the computer being able to reset itself. Just wanted extra extra advice on it thats all. You know how the net is, some people say this some people say that, was just trying to get the real deal info so i could fully understand it and why.

Sleepy4.7 I have read many of your posts on other threads and seems you def have alot of great info and have picked up a few things from you. thanks.
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Old 11-22-2009, 07:49 PM
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Re: Gains/Losses w/SRT exhaust on WK 3.7?

Quote:
Originally Posted by TimmyB View Post
You told me?? Lol. Whats an AFR? And I was really not worried about the burnt valves myth with my WK because of the computer being able to reset itself. Just wanted extra extra advice on it thats all. You know how the net is, some people say this some people say that, was just trying to get the real deal info so i could fully understand it and why.

Sleepy4.7 I have read many of your posts on other threads and seems you def have alot of great info and have picked up a few things from you. thanks.
The computer has a very limited ability to reset/adjust it's parameters. It's for this reason that people need aftermarket fuel/spark controllers aka "tunes" to modify those parameters to achieve peak performance, especially when they add modified heads, aggressive cam profiles, etc.

The "real deal" is that you should have utilized a dual exhaust into the SRT catback, rather than throwing in multiple Y's , etc. There should also be a crossover pipe, such as an H or X pipe. Which you want to use is based on preference.

Backpressure is a myth. A motor needs as little backpressure as possible for peak performance, all the while maintaining air velocity.

AFR= air to fuel ratio.
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Old 11-22-2009, 08:15 PM
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Re: Gains/Losses w/SRT exhaust on WK 3.7?

Ryan very impressive ... I am amazed on how much you know ...

Great to have you on here
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