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How is it possible to gain power by removing the stock resonator on an otherwise stock exhaust?
Yes, the resonator probably DOES restrict exhaust flow and increase backpressure as opposed to a straight pipe or a freer flowing resonator but who cares! I would be willing to bet big bucks that the cats create far more backpressure.
When trying to free up power by reworking the exhaust system one should remove the â??bottleneckâ? to gas flow first. As the resonator is likely not the bottleneck to gas flow why would removing it decrease backpressure?
This sounds like the same BS that exhaust companies like to spew. They often claim that a cat-back exhaust system will give palpable power increases on an otherwise stock car. That is simply not the case unless a particular car has one really, really restrictive exhaust. Most of the time power increases come from exhaust systems only if the cats are replaced or headers are used.
Replacing the stock resonator on an otherwise stock setup is, in all probability, a waste of money and a recipe for a really gay, boy-racer sounding car.
Iâ??d be interested to see dyno results or at least ETs/trap speeds with JUST the resonator as a variableâ?¦. Anyone?
1999 CSVT #545
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Originally posted by CalgarySVT:
How is it possible to gain power by removing the stock resonator on an otherwise stock exhaust?
Yes, the resonator probably DOES restrict exhaust flow and increase backpressure as opposed to a straight pipe or a freer flowing resonator but who cares! I would be willing to bet big bucks that the cats create far more backpressure.
When trying to free up power by reworking the exhaust system one should remove the â??bottleneckâ? to gas flow first. As the resonator is likely not the bottleneck to gas flow why would removing it decrease backpressure?
This sounds like the same BS that exhaust companies like to spew. They often claim that a cat-back exhaust system will give palpable power increases on an otherwise stock car. That is simply not the case unless a particular car has one really, really restrictive exhaust. Most of the time power increases come from exhaust systems only if the cats are replaced or headers are used.
Replacing the stock resonator on an otherwise stock setup is, in all probability, a waste of money and a recipe for a really gay, boy-racer sounding car.
Iâ??d be interested to see dyno results or at least ETs/trap speeds with JUST the resonator as a variableâ?¦. Anyone?
some of this is true...although it has been proven on this site that with the replacement of the y-pipe alone will net you about 5-7(?) horsies at the wheels
"Youth ages, immaturity is outgrown, ignorance can be educated, and drunkenness sobered, but STUPID lasts forever."-Aristophanes.
--93 pgt,headers,intake,borla=14.9 1/4mile
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if you were to replace the stock resonator and mufflers with less restictive units like magnaflow then there would be a small, possibly very small gain as our resonators are pretty restrictive. bigger gains can be had elsewhere though.
00 black/tan svt, #2052 of 2150, born 2/1/00
formerly known as my csvt
"Nothing in the world is more dangerous than a sincere ignorance and conscientious stupidity." -Martin Luther King, Jr.
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The resonator has a 1.875" baffled core and it's on 2.25" pipe.
You could say it's quite a flow restriction!
It is the second most restrictive piece of the exhaust after the POS crush flange in the Y-pipe.
Resonator replacement (straight through NON-louvered or split core) is worth 2-3 FWHP/TQ throughout the power band.
Optimized Y-pipe is worth 5-8 FWHP/TQ throughout the power band. (gains with a chip {i.e. timing!} have seen double digit TQ)
The cat is actually 2.5" in/out (on 2.25" pipe) with a very decent frontal area on the honeycomb. It's not much of a flow restriction.
High flow cat might be worth 1 maybe 2 FWHP in the upper rpm range. Provided of course you have an optimized Y-pipe.
Your thinking about "needing" back pressure is incorrect.
An ideal exhaust would have minimal to no back pressure and the highest exhaust velocity while sustaining enough volume to achieve maximum power.
You DO NOT want back pressure.
It's part of the trade off to achieve velocity (piping size) and volume control (mufflers)
2000 SVT #674
13.47 @ 102 - All Motor!
It was not broke; Yet I fixed it anyway.
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Originally posted by DemonSVT:
It is the second most restrictive piece of the exhaust after the POS crush flange in the Y-pipe.
The cat is actually 2.5" in/out (on 2.25" pipe) with a very decent frontal area on the honeycomb. It's not much of a flow restriction.
I have seen flow bench tests of cats before and placing honeycomb in front of gas flow is a very large restriction. So much so that is should easily rival a resonator no matter how restrictive it may be.
Originally posted by DemonSVT:
Your thinking about "needing" back pressure is incorrect.
An ideal exhaust would have minimal to no back pressure and the highest exhaust velocity while sustaining enough volume to achieve maximum power.
You DO NOT want back pressure.
It's part of the trade off to achieve velocity (piping size) and volume control (mufflers)
I did NOT say back pressure was needed. You must have misunderstood.
1999 CSVT #545
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There are at least 10 dynos showing catbacks on stock SVTs gaining 5-10 (average 7) FWHP. The resonator with its narrow down to under 2" is likely the biggest single bottleneck of the stock SVT catback so Demon's 3FWHP estimate is pretty much what you can expect replacing the resonator with straight through part. Not much but then again its only about $80 and sounds better.
I've seen a number of dynos on a number of cars..they rarely show more than 2-5 HP with main cat removal.
1999 Amazon Green SVT Contour (#554/2760)
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Originally posted by Dan Nixon:
The resonator with its narrow down to under 2" is likely the biggest single bottleneck of the stock SVT catback..
No doubt... but that is not my point. My point is simply this: If I were to re-work a stock SVT exhaust I would do the following in order:
1.) Y pipe, no pre-cats
2.) High flow main cat or gut or replace with test pipe
3.) New cat back or remove resonator
I still find it difficult to understand how the removal of the stock resonator, on a otherwise unmodified exhaust can increase horespower. Unless the stock resonator is the single most restrictive part of the entire SVT exhaust system, i.e. MORE restrictive than the pre-cats, the y pipe intersection, the main cats and the mufflers.....
Are we in agreement then that the resonator is the single most restrictive thing on the entire exhaust system?
1999 CSVT #545
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No, your so called "point" what that replacing it with a high flow resonator was a waste of time (i.e. the name of this thread that YOU created). The fact is, it ISN"T a waste of times as gains, both through hp and sound, are there.
Sure the stock precats and y-pipe are not to be ignored, but you're pint was to say you shouldn't even both with the stock resonaotr, which frankly, is ignorant.
2000 SVT Turbo 295hp/269ftlb@12psi
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Knuckles rebuilt w/new bearings $55
AUSSIE ENDLINKS $70
Gutted pre-cats $80/set
A lack of planning on your part does not constitute an emergency on mine!
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Originally posted by Stazi:
No, your so called "point" what that replacing it with a high flow resonator was a waste of time
No my point is that replacing the stock resonator on AN OTHERWISE STOCK EXHAUST is a waste of time... do you understand the difference?
Originally posted by Stazi:
Sure the stock precats and y-pipe are not to be ignored, but you're pint was to say you shouldn't even both with the stock resonaotr, which frankly, is ignorant.
No, that is not my point, and suggesting so is, frankly, ignorant. (Please refrain from insulting me, and moreover, from putting words in my mouth.)
I am saying that you should do the y-pipe an cats first, do you understand the difference?
So again, is it agreed that the stock resonator is the single most restrictive part of the entire exhaust system?
1999 CSVT #545
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Quote:
Yes, the resonator probably DOES restrict exhaust flow and increase backpressure as opposed to a straight pipe or a freer flowing resonator but who cares! I would be willing to bet big bucks that the cats create far more backpressure.
I understood your point...
But I think in the case of the Contour, you are probably incorrect. I have not seen any pre-post dynos with resonator removal alone so I did the next best analysis..catback change where LOTS of data show a gain. It is pretty universally accepted that resonator is worst part of catback so I think the 3 HP estimate is pretty accurate (may actually be 2-5FWHP I would say).
Similarly, I have not seen the main cat removal ALONE dynoed pre-post in Contour but other cars it is rarely more than the 2-5 HP gain that I estaimat for the resonator. Further, I have seen data with SHO SHOP Y pipe, which includes a straight pipe in place of main cat..gain was 8 HP, and I suspect the Y pipe alone counts for about half of that (MSDS Y with stock cat showed +6HP..though Y is different style and not directly comparable).
So my point was that I think the 2 mods are likely pretty even in power gains (+/- 1-2HP) and I myself would NOT bet big bucks on the cat removal being better. Doing both would be best but more noise. The resonator change has the advantage of being emmisions legal.
1999 Amazon Green SVT Contour (#554/2760)
"People demand freedom of speech as a compensation for the freedom of thought which they seldom use."
-Soren Kierkegaard (as posted by Jato)
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