Are exhaust cutouts worth it on a turbo car?
07-12-2008, 06:33 PM
#23
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We recently had a 02 z06 with a HP turbo kit getting a SD tune and more boost for race gas.
He had installed the electric cutouts and wanted a re-tune for them as well.
The car had the stock TI mufflers so as you can imagine 750+ hp on that is a bit of a restriction.
With boost set to around 15-16psi, it picked up 75rwhp with the cutouts open, and the boost hit light a freight train when it came on, not to mention it spooled a few hundred rpms faster.
Note of caution, it will change your AFR so beware.
He had installed the electric cutouts and wanted a re-tune for them as well.
The car had the stock TI mufflers so as you can imagine 750+ hp on that is a bit of a restriction.
With boost set to around 15-16psi, it picked up 75rwhp with the cutouts open, and the boost hit light a freight train when it came on, not to mention it spooled a few hundred rpms faster.
Note of caution, it will change your AFR so beware.
07-12-2008, 06:49 PM
#24
07-12-2008, 06:52 PM
#25
You've always seemed like a pretty knowledgeable guy on this forum but I have a hard time believing a cut-out produced an extra 10psi. I've had cut outs on several set-ups of mine and a couple of my boosted friends have too and I have never seen anything REMOTELY close to a 10psi swing. You had to of had another issue.
07-12-2008, 07:21 PM
#26
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hey this is a very good thread for a new to fi guy like myself. I'm swinging toward the sts kit because it should be a cheaper install and less stress on the motor than a front mount. I love the sound of cut-outs, but is it sensible or possible to put them on a sts kit?
07-12-2008, 07:27 PM
#28
BTW, with the Magnaflow, it doesn't gain any boost when I remove it totally.
It all just depends on the muffler.
Mike
07-12-2008, 08:25 PM
#30
I was running a 3.5" Mufflex system with a 3.5" Aerochamber muffler. My low-boost setting of 11 psi became 17 psi with the cutout open. My high boost setting of 18 psi became 25++ psi with the cutout open. When I removed the Aerochamber (to be replaced by a 3.5" Magnaflow), I noticed that the inlet end-wall of the muffler had actually bulged out from heat and pressure.
BTW, with the Magnaflow, it doesn't gain any boost when I remove it totally.
It all just depends on the muffler.
Mike
BTW, with the Magnaflow, it doesn't gain any boost when I remove it totally.
It all just depends on the muffler.
Mike
07-12-2008, 10:16 PM
#31
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thanks for all the info guys. like i said i have a 3" corsa exhaust so i'm sure i will see an increase of power. i'm only running 7psi on a stock bottom end with heads and cam 587rwhp 522 rwtq on a mustang dyno hoping to see over 600 with them open.
07-12-2008, 11:51 PM
#32
i just went backed and check my log from the day I did the back to back cutout closed and open runs at the track, and picked up a 1/2 second. I ran about 170 kPa with the cutup plugged and about 177kPa with it open. Thats about 1 Psi. The exhaust setup was 3" down pipe off the the turbo to under the truck (no kitty), then strait as a string back about 8 feet back to the Warlock muffler and then it goes strait though the muffler and out the back of the cut out built into the muffler. There is no louvers or baffling though that part of the muffler.
I now have a same 3" down pipe to under the truck and then into 4" duramax exhaust with a 30" long strait though muffler. Sounds good and very low restriction.
I now have a same 3" down pipe to under the truck and then into 4" duramax exhaust with a 30" long strait though muffler. Sounds good and very low restriction.
07-13-2008, 04:20 AM
#33
I like them because I actually run a stock muffler 
to keep it very quiet when I want to have a conversation in the car or keep it stock sounding for the non-suspecting people... and cops 
. Second, they really let you hear the turbo's spool, loud but lots of fun. Third, you know you have zero restriction. $400 but worth every penny IMHO.
to keep it very quiet when I want to have a conversation in the car or keep it stock sounding for the non-suspecting people... and cops . Second, they really let you hear the turbo's spool, loud but lots of fun. Third, you know you have zero restriction. $400 but worth every penny IMHO. Last edited by SStolen; 07-13-2008 at 01:49 PM.
07-13-2008, 11:07 AM
#34
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I have had a QTP and DMH and now have STREET PRO. The qtp rattled when closed and broke after I sold it . The dmh worked good but rattled when closed. The street pro is very pricey but doesn't rattle when closed and has been working perfectly. I am very happy with it and likely buy another one for my 96z28.
DMH and QTP might have redesigned their products I had them quite a few years back. DMH offered to fix mine but sold it rather than going thru hassle of shipping it back, a bit of pain since I am up in Canada.
Cutout is high on my list of favorite mod.You can have your car nice and quiet when they are closed,open them up a little bit or a lot and get the sound where you like it. I like to put the fear of god into hondas sometimes at the lights.Its great fun!
For some reason in a few of my NA tests the car seems slower with the cutout not sure why. It should really help though on a turbo car epecially one like mine that has 3 inch single exhaust. For now going to be running single cutout only in intermediate pipe.
DMH and QTP might have redesigned their products I had them quite a few years back. DMH offered to fix mine but sold it rather than going thru hassle of shipping it back, a bit of pain since I am up in Canada.
Cutout is high on my list of favorite mod.You can have your car nice and quiet when they are closed,open them up a little bit or a lot and get the sound where you like it. I like to put the fear of god into hondas sometimes at the lights.Its great fun!
For some reason in a few of my NA tests the car seems slower with the cutout not sure why. It should really help though on a turbo car epecially one like mine that has 3 inch single exhaust. For now going to be running single cutout only in intermediate pipe.
check them out guys here's the link
http://www.streetpro.us/index.html
05-19-2009, 12:05 AM
#35
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ummm.... buh? ok... im very confused for a multitude of reasons, one of which is this, now when you guys are running turbos with cut outs are you running the turbo in the engine compartment or lower down off the exhaust system? and if your running it off the exhaust system is your turbo located before the cut off or after the cut off? i had this crazy idea the other night wondering if you could run cut offs on dual exhaust and have a turbo coming off each cut off? i mean i dont know why it wouldnt work but i dont know that it would? that being said i am INCREDABLY undereducated on turbos and how they work. but if you could do this it would almost create a tubo car at the push of a button. a feature some might not find appealing, but if it could be done successfully i think it would be especially nice around the police
05-19-2009, 05:14 AM
#37
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I read that a guy's LS2 made 512 rwhp with a off the shelf cat-back system with no cats. After that he threw Random cats and cutouts up stream of the cats and made 478 rwhp with the cutouts closed. He opened them up and the car made 510 rwhp.
The turbulence created by the cutout itself cost him a lot of power and I noticed the same on my old car. I had dual cutouts right after the long tubes and with the cutouts open it made some nice power, not so much with them closed. After awhile I got tired of the cutouts and went with a true dual setup and I couldn't tell difference in power between open cutouts and the true duals.
Food for thought.
The turbulence created by the cutout itself cost him a lot of power and I noticed the same on my old car. I had dual cutouts right after the long tubes and with the cutouts open it made some nice power, not so much with them closed. After awhile I got tired of the cutouts and went with a true dual setup and I couldn't tell difference in power between open cutouts and the true duals.
Food for thought.
05-19-2009, 05:57 AM
#38
Why not just refrain from hitting the gas around the police? The gas pedal IS a boost controller!
05-20-2009, 01:03 AM
#40
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while i realize your pedal is a boost controller, i also think it would be really nice to have a sleeper, thats what i want anyways, id like moderate easy to have fun while staying out of to much trouble power for everyday commuting, but at the push of a button have the ability to bark a tire on the interstate and shoot off, and i know this sounds like nos, but id like a turbo kit that i could do that with... cuz i want nos too, haha but i also wonder if you could put cutoffs on a normally turboed car and tune the car for max boost with the cutoffs open, and then leave them closed most of the time, all the while running maybe 3lbs of boost, maybe a little hp gain? and then when sombody pulled up to you trying to start crap on the interstate, throw open the cutoffs and take off like a bat out of hell? or would all that increased pressure so quickly cause you to blow your engine?