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I've done a search, but couldn't find what I'm looking for. My question is, will running through the muffler without the cutout open at full boost be hard on the valvesprings? Motor makes 810/875rw.

NemeSS

iTrader: (127)

More info on the build.
seems like stout numbers thru a single 3" exhaust.

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True, I could have been more detailed. Car is a 00 ss, 370ci ls2, ls6 heads/intake, 96# injectors, 3 inch dp, 3 inch out the back into a MagnaFlow with dual 3 inch out. Tu1 cam, power peaks at 6300....I never shift above that. 6 speed car btw. Yea, the car runs hard....really pleased with it. It's an e85 car as well, that contributes to some of the saltiness.

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Cutout was open when those numbers were made.

alocker

iTrader: (10)

On my 6.0 with a 4" downpipe reduced into a 3" into a 2.5" dual makes a pretty big difference. I gain almost 4 PSI going from closed to open 4" dump. Consider one of those boost activated cutouts for the best of both worlds.

69-chvl

iTrader: (11)

Gaining 4psi could equal apprx 100hp in some cases - that is huge. Maybe that's why I believe I'm missing some mph

stoverz28

iTrader: (8)

My car makes 9lbs through the 3" exhaust and 15 cutout open, 4" dp.

OP, why would having the cutout closed be harder on the valve springs? They shouldn't care at all how well the exhaust is flowing.

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In my mind it seems that the additional backpressure would possibly make life a little more difficult for valvesprings. I'm new to the turbo game, so there's quite a bit that I don't know about them.

coltboostin

You are right to a point.

Are you measuring back-pressure? Did you at least do a back to back dyno to see what the difference in power was?

willizm

iTrader: (10)

I ran a pt7675 with 3" downpipe to cutout and then through the magnaflow exhaust. Whenever I'm at the track or getting on it, I always open up the cutout. Else if I'm driving around I keep it closed. It would most likely create a restriction.

If your turbo is an on3 or tc76 it probably has a 68mm turbine wheel which would probably pose a bigger restriction than the catback would, however the best catback is no catback for a turbo car so there is always something to gain dumping the exhaust

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The car was dynoed prior to me owning it, only runs made were with cutout open. And to be frank, I don't know how I would go about checking backpressure. Will you tell me would be the best way to go about it?

alocker

iTrader: (10)

At your power level a 3" catback is going to be a restriction. It's not just the diameter but the length and bends also cause a restriction. I assume you have decent valve springs with the aftermarket cam so don't worry about those.

If you just want the car to be quiet, cap it up and drive. It will just spool slower and not have as much peak boost.

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Thanks for the feedback, yea..I've noticed that it isn't as crisp with the spool up. And yes, it does have patriot dual springs. Sometimes I like to make a quick blast...but don't really feel like hearing the cutout open. And in terms of performance, it being closed doesn't really seem to slow it down much. Kinda like stealth mode sometimes.

1bdbrd

iTrader: (12)

There's also the boost reference cutout option. Set it to open up after a certain boost level and then set your boost controller below that for the days you don't want it to be louder.

Game ova

I hear ya, I also run a precision...7678 I believe .96ar. True, no catback is best. I was just wondering if playing with cutout closed would weaken the springs or cause valve float being that exhaust would be kinda backed up. And we probably have the same muffler as I run magnaflow as well.

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Those boost reference cutouts are definitely nice pieces, but MAN those things are pricey!! As most other things related to our hobby I guess.

alocker

iTrader: (10)

Denmah uses this one and it seems to work nicely.

http://loudvalves.com/

I splurged on the Sound Performance unit and I can vouch for the quality. It's a really nice piece with oring seals. If you cannot affort it, try the loudvalve. A boost cutout is really the way to go on a turbo car. As if a turbo car isnt enough to scare the doodoo out a new passenger, having the cutout open unexpectedly under their feet makes it that much better.

3 window

iTrader: (1)

I'm planning 4" exhaust up over the axle and out the back with a straight through muffler. You think it'd still be worth putting a 3" cutout on it up front. Loud valves doesn't offer a 4".

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How much are you making?

3 window

iTrader: (1)

Not sure to be exact. SBE 5.3, 243 heads untouched, 218 cam, truck intake, s475/83 t4, 20 psi max.