Exhaust Cut-out [Merged 8-9] cut out bypass

[Cs4g63]

By the way if your a sleeper this will be a great thing to do...

This would be the best reason to go with the cutout. Definately a great way to fool some jacka$$ that wants to race.

 

[TSG59_Steve]

Especially if you have cams

 

[nightspeed87]

This would be the best reason to go with the cutout. Definately a great way to fool some jacka$$ that wants to race.

Especially with my stock muffler hanging back there just chillen .
I leave people confused because they hear this car screaming by on the high way and
then by the time they catch up to me on the exit back onto the street its a quiet car.

Especially if you have cams

Yea and oh do I want a pair of fp2s so bad right now as I have almost maxed out my e316g pump gas set up.

Whenever I get picks of the car and everything Ill post and show you what my electric cutout looks like...

 

[architechnik]

Can you make an electronic bypass?
You could route it back through the muffler, bypassing the cat, just to make it still sound more like a street-legal and removing at least some of the backpressure. It's not quite stripworthy, but you could still pass emissions with a flip of a switch and not attract too much bluelight interest.

I would always be worried about those exhaust gasses, having not been broken down in the cat, igniting under the car... can you put the cutout far enough forward to route the outlet pipe just behind the front tire?

 

[Mr Peepers]

a little restriction? um, no, not at all. Backpressure is the enemy, no matter what the case. Naturally aspirated engines have an exhaust system that compromises between a good scavenge and backpressure. In a turbo car, scavenge is not as important and we want the turbine to operate as efficiently as possible, so the less backpressure, the better, hence 3" systems being popular, and even 4" possible.

Just wanted to elaborate, VERY good info by the way. There is still a compromise in the size of exhaust tubing, even with a turbo negating a lot of the scavenging in the first place. The size of the pipe also affects speed of the exhaust flow and the surface area obviously, meaning the exhaust will cool down much more as it travels the system. Cool air is dense air as we all know but that also means it doesn't flow as well more backpressure. Backpressure equates to a smaller pressure differential surrounding the turbine, decreasing its overall output.

A good article on the subject along with much more exhaust system info: http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

And another excellent article on backpressure why it was seen as necessary(based on n/a engines): http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm

 

[tkelly27]

I really love my 3" cat and muffler, but I can feel a definite quicker spool up and more power when I open up the cut out.

I'm 22 and I love noisy ass clunkers. More sophisticated people might want to keep a 3" down pipe and cut out, and have a 2.25-2.5" exhaust system out the back to keep it from driving them crazy. Electric would also be the way to go. If you're too poor for that, you can get them from Summit racing for $30 some odd.

The little stuby segment of open pipe will always outflow anything that goes back to the rear of the car (maybe not a 4" pipe...), muffler or not.

 

[HIGHPSI4]

I run a 3" turbo back straight pipe. I have been in several situations such as seat belt checks, license checks, passing by Troppers that have just pulled someone, etc. where a quite exhaust is a good thing just to keep the heat off of you. In town the cops are just looking for a modification change to pull you over and go over the car. So I am leaning to a cut-out for these times.

 

[tkelly27]

An easy to remove flange somewhere on your down pipe is a good idea, but it's not electric, and where do you plan on putting your exhaust system while you race? In your car? That's not a weight savings

Personally I'll be doing that, but that's just because I'd like to have the convenience of a flanged fitting.

 

[nightspeed87]

Just wanted to elaborate, VERY good info by the way. There is still a compromise in the size of exhaust tubing, even with a turbo negating a lot of the scavenging in the first place. The size of the pipe also affects speed of the exhaust flow and the surface area obviously, meaning the exhaust will cool down much more as it travels the system. Cool air is dense air as we all know but that also means it doesn't flow as well more backpressure. Backpressure equates to a smaller pressure differential surrounding the turbine, decreasing its overall output.

A good article on the subject along with much more exhaust system info: http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

And another excellent article on backpressure why it was seen as necessary(based on n/a engines): http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm

The thing is, my cut out dumps right after the end of the 3inch mandrel dp
so how cold could the exhaust possibly get its not like its traveling that far I dont think
that applies to my situation if thats what it was aimed at. Besides people who put really large exhaust like 4in and what not, dont care so much about exhaust flow speed because these are usually people who are also pumping 500-600 hp's through it therefore the pressure thru the pipe from the amount of exhaust moving thru will keep it moving plenty fast. Your theory would make more sense if its someone with say 200hp and a 4in exhaust, in my opinion at least. And running large or open exhaust, I dont look at it is losing power down low, id rather look at it like, shifting your power band like with almost any high flow modifications will do to your car...

 

[TSG59_Steve]

This is what first got me thinking about it:

http://boneheadperformance.com/exhaust/electriccoutouts.htm

I'm gonna get some BC 272's, mmmmm.... cams

 

[nightspeed87]

An easy to remove flange somewhere on your down pipe is a good idea, but it's not electric, and where do you plan on putting your exhaust system while you race? In your car? That's not a weight savings

Personally I'll be doing that, but that's just because I'd like to have the convenience of a flanged fitting.

Maybe if I can get some pics and a video up i will be able to pursway you guys into getting an electric version instead of manual flanged type cutouts. This car has had an electric cutout for like 3 years with no problems.

Here is a cutout on a suburu STi in which looks very similar and functions identically with mines except mines isnt as far down the exhaust system and mines dumps right after the driver tire...

http://www.youtube.com/watch?v=1uKmhx5INSU&mode=related&search=
http://www.youtube.com/watch?v=6O9uXh17Fhk&mode=related&search=
http://www.youtube.com/watch?v=yX3DAxpVd4k&mode=related&search=
http://www.youtube.com/watch?v=bsgOVy1_8R0&mode=related&search=

Cut out on a subie....

Couldnt really find any on a dsm.

 

[Mr Peepers]

The thing is, my cut out dumps right after the end of the 3inch mandrel dp
so how cold could the exhaust possibly get its not like its traveling that far I dont think
that applies to my situation if thats what it was aimed at. Besides people who put really large exhaust like 4in and what not, dont care so much about exhaust flow speed because these are usually people who are also pumping 500-600 hp's through it therefore the pressure thru the pipe from the amount of exhaust moving thru will keep it moving plenty fast. Your theory would make more sense if its someone with say 200hp and a 4in exhaust, in my opinion at least. And running large or open exhaust, I dont look at it is losing power down low, id rather look at it like, shifting your power band like with almost any high flow modifications will do to your car...

I was just trying to hit on "bigger is always better" for turbo exhaust and all the misinformation on backpressure. I wasn't talking about cutouts, I got off on a tangent Like I said, there is a compromise, just like there is a point where 3" full exhaust will be overall more efficient than 2.5", after a certain power level 4" will be more efficient overall than 3"

 

[nightspeed87]

I was just trying to hit on "bigger is always better" for turbo exhaust and all the misinformation on backpressure. I wasn't talking about cutouts, I got off on a tangent Like I said, there is a compromise, just like there is a point where 3" full exhaust will be overall more efficient than 2.5", after a certain power level 4" will be more efficient overall than 3"

Tru that.
I personally like room to grow and only have to do stuff once, and if I could have hell id even put a 3.5inch dp with a 3.5 cutout instead of the 3inch cutout I have... Do i need that... No, does it matter... No.
Will it ensure I never loose a single hp due to pumping loses when I start going into the high hp figures... Probably... Idk thats how I look at stuff...

 

[Mr Peepers]

With a DP and cutout, I doubt you'll notice ANY drawbacks no matter how big you go, but I'm sure if you went too small you'd definitely know it. There is so little piping for the exhaust to travel when the cutout is open. We were talking apples and oranges before

 

[kspharris]

Has anyone ever dynoed them yet? I searched all the cutout threads and found nothing. I would guess that one would get a little more power than doing a full 3". What I have done is went from stock exhaust to a 3" downpipe with a 3" cutout in it. It is all connected to my stock cat and stock cat back. I might get it dynoed if nobody knows the answer to my question. Does anyone know of a cheap place to dyno here in TN or close? Thanks and let me know, Keith.

 

[99gst_racer]

Has anyone ever dynoed them yet? I searched all the cutout threads and found nothing. I would guess that one would get a little more power than doing a full 3". What I have done is went from stock exhaust to a 3" downpipe with a 3" cutout in it. It is all connected to my stock cat and stock cat back. I might get it dynoed if nobody knows the answer to my question. Does anyone know of a cheap place to dyno here in TN or close? Thanks and let me know, Keith.

I've never known anyone to dyno the difference between an open cut-out and a closed cut-out. But I have had some track experience with them.

A friend of mine runs here 2G at the local drag strip. She has a 2.25" turbo-back, and a cutout in the downpipe. She gains almost 4 mph by opening it.

I've seen another guy at the same drag strip make back-to-back passes with and without his turbo-back exhaust. He gained a couple mph and a couple tenths.

So, freeing up exhaust flow definitely helps. Be sure to report back with dyno numbers if you do have it done.

 

[spawn87]

hey i wana put an electric exhaust cut-out on my 99 gst its running stock exhaust and will probably put a header later on what size cutout should i put on it ?

 

[matthewdesigns]

If you have a stock DP, then I'd go with a 2.5" or 3", depending on where you get it. I got my 3" from BadlanzHPE and it's a full 3", including the valve (the valve is actually closer to 3.5"). Just make sure that you don't neck down any farther than your dp size, or you kinda defeat the purpose.

And I was going to have mine put in just ahead of the stock cat location, but it wouldn't fit. So it was installed right at the start of the curve of the dp, about a foot below the turbo. The outlet faces down towards the passenger side. Love it!

 

[2GAWD4U2NV]

Something that is not bigger than the diameter of the pipe and would match up properly would be best. I have a 2" electric cut-out that im trying to sell. It works on factory,3.5",+. Basically whatever will fit under the car . If you are interested, let me know. I really need to get it sold because my T-25 is going out! I'll include the wiring, ( you'll have to make your own switch and run it the way you want!), the actual cut out with everything you need, and an easy 3 bolt flange adapter so you can take it off and put it on in a matter of seconds instead of getting the actual motor welded to the downpipe.

 

[spawn87]

how much are u thinking of asking for the cut out...and if its a 2inch wouldnt i need at least a 2.5 inch?

 

[2GAWD4U2NV]

I believe $110 shipped would cover it. I pulled it off of a GST part out project and it was on the factory downpipe. Factory DP's are what, 2" 1/4 or 2"? The bigger the exhaust piping, the easier it is to make it up to. Here is how it works: you have your DP. You find where you want to attach the electronic cut out. You get the right size diameter piping that fits your flange for the cut out. I'd go to an exhaust shop to get them to weld the little piece of piping onto your DP for you. Much easier and is only like $5-10. Get your flange put on the end of the piping. (Mines 3 bolt.) Then line your holes up and drop some bolts through. Tighten up, and you are good to go on that end. The next part, you have to snag a little bit of wire so you can run the switch wherever you want it. Not hard at all.

BTW- I can take a pic of an example if you really need me to. Just ask!

 

[spawn87]

my friend gave me one he had from his srt-4 so i wont need urs any more sry. but thanx for the offerer

 

[DSMunknown]

If anyone is looking to do something like post #8, look here. BTW, sorry for bringing back an old thread, but I just found this browsing the web. Sure, you could "do it yourself", but for those of you who "ain't got no skills", then this may be for y'all.

 

[420a-t]

Has anyone ever tried to have an electric 2.5" or 3" cutout on the downpipe, so the cutout goes through the driver's side of the bumper and the rest is stock-routed? All I've seen is the o2 dump's go through there or just the exhaust, not like a cutout, but the exhaust. I want to try this but does anyone see any fitment/heating issues? Let me know what you guys think. Thanks

 

[turboglenn]

We run them on my friends 55 chevy wagon with 572 rat motor in it. Never tried it on a 4cyl turbo but i've wanted to if they weren't damn near 300 bucks each.

I too would like to hear if they are worth it on our cars.