Lets talk about exhaust cutouts
02-26-2009, 02:49 PM
#1
Lets talk about exhaust cutouts
On my journey to create the most sleeper FI Z out there, I have started to look into electric cut outs. I pretty much got the idea from reading SPG thread in the FI section about their new boost controlled valve.
Actually I have never heard or seen a Z with cutouts before because it is never talked about on here. I want to know what you all think about it?
In a FI car does it affect the tune widely when it is closed/open? Currently I have the stock exhaust system so that is restricting the flow tremondously. I was thinking about having both downpipes flow into an X pipe, I would cut the X pipe in half and have them weld in the cutout and then keep it true dual to the back of the car.
But then more questions arise when this is installed. Should I go with 3" DP's and then after the cutout bring it down to 2.5" pipe? What I am mainly concerned about is the tune. How does this effect the tune? I am going to be running a Haltech. How should the car get tuned, with the valve open or closed, I'm assuming open.
Mabe I should just scrap the idea, idk but I would like everyones opinion on it.
Actually I have never heard or seen a Z with cutouts before because it is never talked about on here. I want to know what you all think about it?
In a FI car does it affect the tune widely when it is closed/open? Currently I have the stock exhaust system so that is restricting the flow tremondously. I was thinking about having both downpipes flow into an X pipe, I would cut the X pipe in half and have them weld in the cutout and then keep it true dual to the back of the car.
But then more questions arise when this is installed. Should I go with 3" DP's and then after the cutout bring it down to 2.5" pipe? What I am mainly concerned about is the tune. How does this effect the tune? I am going to be running a Haltech. How should the car get tuned, with the valve open or closed, I'm assuming open.
Mabe I should just scrap the idea, idk but I would like everyones opinion on it.
02-26-2009, 03:02 PM
#2
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Its just one more thing to go wrong. I have thought about this too. If I were to do it, I would have the switch to open the valve activated by having two points touch when the throttle plate opens fully (full throttle). I know that some nitrous switches are like this but why not just do open dumps?
02-26-2009, 03:35 PM
#3
Open Dumps and exhaust cutouts are two separate things. I could agree with you that its just more things that can go wrong, if you have ever seen a electric valve open they take a couple of seconds to go from fully closed to fully closed so I dont think that a switch at full throttle will react fast enough.
02-26-2009, 04:00 PM
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So are you wanting to just have a switch so you can have it off or on and just switch your map according to it? Not sure if you have a utec but I know you have to make the map selections with the engine idling (My bad, just saw you have a Haltec, not sure how those work with map selections). With you being turbocharged I know you would make more power / boost so a tune should be done for both settings. I guess open dumps would commit you to having a loud *** car every time you boost. Oh an no I didn't know they opened that slow. I was wanting to do an electric valve to open my bypass valve to the atmosphere or route it back into the intake. Sometimes its annoying to hear that constant whistle while driving down the highway with a supercharger. I know the concept would work and should work for you too.
Last edited by 350Z400rwhp; 02-26-2009 at 04:15 PM.
03-03-2009, 05:46 AM
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I'm considering this myself. I'm getting ready to build the motor in my car and add a few more goodies and have been looking into QTP electronic cutouts. Thinking about dual 3" right after the test pipes. In for more info on the tune!!!
03-03-2009, 06:41 AM
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I have experience with electric cut outs, we run one on my dads 10 second maxima.
The tune does change when its open, the AFR gets quite a bit leaner when the cutout opens so you will want to log and adjust for it. It's not much but if you are running on the line with nitrous its enough to possibly cause a hiccup. I would log your car then open it and log again. If you are running in the 12.5 : 1 at WOT area then I would expect to see .3-.5 difference during a WOT run with the cutout open.
The cheaper cutouts tend to leak and eventually break and stop working. We ran with one about $175 bux and it lasted about 6 months before it was toast. We're looking at a new brand new, some of the better ones are $400+ and have guarantees against leaking and longevity.
A buddy of mine with a 550whp Talon ran a 3.5" cutout inline inside his 3" exhaust system. (so it was like a throttle body in your intake). He drilled holes in the plate of the cutout so when it was closed the car was really quiet and ran like it was stock. He could still make 15psi of boost and the car was fast enough. He set the cutout on a switch and also made it open at WOT. When the plate opened it was straight through and the car would make full hp. The reason he did a 3.5" cutout in a 3" exhaust was to make up for the plate being inline inside the exhaust system even when open it would be a bit of restriction so he went slightly larger to make up for it. It worked really well and kept his car really quiet, and really loud when he wanted without having the cutout vent outside. It was really just a measure to keep his car quiet with a straight through 3" exhaust more than anything, but a good idea non-the-less.
Running it at the Y pipe would be the easiest as you would only need one. I would tune open loop with it open and close loop with it closed as that will be how you will drive most commonly. I would also put the cutout on a WOT switch so it opens automatically at WOT. You don't go WOT unless you wan to make noise, and part throttle boost (80% throttle) is plenty of acceleration in most scenarios (like getting on the highway) so you can have power and keep it quiet. Then go WOT and it will be noisy which at WOT isn't really a concern. You could also tune it close and opened and put both maps on a switch (can you do that with haltech like AEM and UTEC?) and put the cutout on the same switch so your map and cutout work together.
You will see a huge increase in spool time, boost level and power and tune with the valve open vs. closed so you need to prepare for that.
The tune does change when its open, the AFR gets quite a bit leaner when the cutout opens so you will want to log and adjust for it. It's not much but if you are running on the line with nitrous its enough to possibly cause a hiccup. I would log your car then open it and log again. If you are running in the 12.5 : 1 at WOT area then I would expect to see .3-.5 difference during a WOT run with the cutout open.
The cheaper cutouts tend to leak and eventually break and stop working. We ran with one about $175 bux and it lasted about 6 months before it was toast. We're looking at a new brand new, some of the better ones are $400+ and have guarantees against leaking and longevity.
A buddy of mine with a 550whp Talon ran a 3.5" cutout inline inside his 3" exhaust system. (so it was like a throttle body in your intake). He drilled holes in the plate of the cutout so when it was closed the car was really quiet and ran like it was stock. He could still make 15psi of boost and the car was fast enough. He set the cutout on a switch and also made it open at WOT. When the plate opened it was straight through and the car would make full hp. The reason he did a 3.5" cutout in a 3" exhaust was to make up for the plate being inline inside the exhaust system even when open it would be a bit of restriction so he went slightly larger to make up for it. It worked really well and kept his car really quiet, and really loud when he wanted without having the cutout vent outside. It was really just a measure to keep his car quiet with a straight through 3" exhaust more than anything, but a good idea non-the-less.
Running it at the Y pipe would be the easiest as you would only need one. I would tune open loop with it open and close loop with it closed as that will be how you will drive most commonly. I would also put the cutout on a WOT switch so it opens automatically at WOT. You don't go WOT unless you wan to make noise, and part throttle boost (80% throttle) is plenty of acceleration in most scenarios (like getting on the highway) so you can have power and keep it quiet. Then go WOT and it will be noisy which at WOT isn't really a concern. You could also tune it close and opened and put both maps on a switch (can you do that with haltech like AEM and UTEC?) and put the cutout on the same switch so your map and cutout work together.
You will see a huge increase in spool time, boost level and power and tune with the valve open vs. closed so you need to prepare for that.
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03-21-2009, 07:47 AM
#10
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SP boost activated cutouts....can also be controlled by a hobbs switch for NA guys.
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