3" cut-out w/ stock exhaust vs. full 3" exhaust

[alika86]

So I'm thinking about doing something with my exhaust. I'm debating between a 3" cutout and a full 3"exhaust. I got quoted $550 for a full 3" exhaust from a local exhaust shop.

As an alternative, I was thinking of buying a bolt- on 3" test pipe to replace the cat and welding in a 3" electronic exhaust cutout.

That way I can just bolt on and bolt off if necessary. The flow should be pretty good with the cut-out right?

The stock system is 2.25" so mounting the 3" cutout where the cat is should give me about the same flow as a full 3"?

The cutout setup would cost me about $300 compared to the $550 for the full 3". If they flow about the same, I'd rather get the cheaper setup.

What you guys think?

 

[JayRolla]

It should work out pretty well. My buddy is running a gt37r on his SRT-4 and he has a 3" cutout on his stock exhaust at the bottom of the downpipe. Only problem is when shifting he shoots fire out the cutout and the whole underside of the car is burnt. All the heatshield material around the fuel lines are gone and so is some other material for sound dampening. I would not do it just because of that issue.

 

[alika86]

thanks for the quick response!

Wow that sucks that all that stuff gets burnt.. in that case, you think some DEI heat sheild tape should help? I'd probably just put it in the areas under the car that would most likely be burnt.

 

[93_tsi_fwd]

Since your all stock you wont be shooting flames out of there. I have a 3'' cut out and my car has some bolt ons and it doesnt throw flames. $500 for a full 3'' exhaust!!! my god, why not get ebay full 3'' system instead.

 

[alika86]

well that's good news that i won't be shooting flames! yeah all stock for now

as for the ebay exhaust, I live in Hawaii, so shipping to here is an arm, a leg, maybe a kidney or lung ...I did find some cheap stuff on ebay, but shipping made it all cost about $500 anyway.

oh yeah... are you running that cutout with the stock exhaust or did you put on an aftermarket downpipe?

 

[93_tsi_fwd]

Im running it with the stock pipings welded the cut out right before the cat, I still have the cat on my car and a 3'' muffler at the end.

 

[alika86]

cool... that's pretty much what i wanted to do except replace the cat.. did you notice a big difference in power? similar to a 3" exhaust or more? btw thanks for answering my questions I'm leaning towards the cutout now.

 

[93_tsi_fwd]

yes i did feel a difference in power. its like when the vtec on a honda is always open.

 

[silverbullett]

I've been thinking of using one of QTP's cut-out's and adding a resonator to my exhaust. I just can't stand all the drone.

QTP - QTEC Electric Cutout

Here's the one I'm thinking of buying.

 

[alika86]

yes i did feel a difference in power. its like when the vtec on a honda is always open.

wow...that's something to look forward to!

 

[alika86]

I've been thinking of using one of QTP's cut-out's and adding a resonator to my exhaust. I just can't stand all the drone.

QTP - QTEC Electric Cutout

Here's the one I'm thinking of buying.

Yah i know what you mean. I had a full 3" exhaust on my old 1g talon and sometimes i wished i could've turned that drone down a bit...but just a bit

I was also thinking about getting the QTP cutout.

I like that electronic controller too so i dont have to guess what position the butterfly's at.

I also like that you can put presets in to fully open or closed or somewhere in between.

I was thinking of getting this also: Welcome to DMH Performance!

It says that you can open the butterfly at the flick of a switch... so I'm assuming there's somekind of preset system, which would be awesome because its only $200, whereas the QTP valve+ controller is about $300

 

[ed_GST]

E-cut outs are worth every penny
when close nice quiet driving NO cops
and if you put it in the downpipe u can leave the rest of the exhaust stock
u can pass emissions test and save the trees
also gives faster spool of the turbo and a nice turbine whine noise

im planning to install one on my car
used to have e-cutout on my DAEWOO (2.2L, EVO VIII 16G etc..) i loved it

 

[alika86]

awesome man.. wow, a daewoo?.... sorry man i just keep thinking about Bobby Lee's character "TANK" on MadTV...if you've seen it you know why I'm laughing... but damn you must've dropped a couple jaws with that daewoo huh? sounds like a good sleeper

Yah i like that you can decide when you want the noise and power. Good for sleepers. I enjoy that surprise factor with my o2 dump. I can cruise if i want, or open it up and scare the crap out of people when the wastegate opens..

Cheap and effective power.. sounds better and better to me!

YouTube - MADtv - Tank at a Playboy Party (Bobby Lee)

 

[silverbullett]

Thanks for the link bro. Nice find!

 

[ed_GST]

awesome man.. wow, a daewoo?.... sorry man i just keep thinking about Bobby Lee's character "TANK" on MadTV...if you've seen it you know why I'm laughing... but damn you must've dropped a couple jaws with that daewoo huh? sounds like a good sleeper

it was a sleeper
that vid made me laugh


this is the brand that i had http://www.badlanzhpe.com/

very good one

 

[Novice]

That looks pretty sweet. I'm wondering though if you still lose some power by the exhaust that does run through the stock part still. Because it's still open and you're just counting on most of it to go out of the cut out?

I guess it would be hard to tell unless you had Dynos of a full 3' exhaust vs a cut-out.

 

[alika86]

no problem on the link! Bobby Lee's classic.. ..

So I've ordered the QTP 3" cut-out and the digital controller. I basically went with the qtp because it had the controller with the presets. I like that kind of convenience.

I figure I'm already spending the money, I might as well get something really nice and convenient for a couple extra bucks. Still cheaper than a full 3"

The badlanz one looked pretty good, though. But the controller didnt have presets.. that was pretty much the deciding factor.

I've had a full 3" before on my old tsi awd, so as soon as I get this installed I'll post up my experience with the cut-out.

As for the flow... I would think that the flow would still be pretty good. Hotter exhaust gases nearer to the turbo are less dense and flow easier through the stock 2 1/4" piping.

However, as the gases move down the piping, they cool and become more dense, making flow more difficult through the stock piping.

That's where the cut-out comes in to help all that exhaust flow right out! Hopefully it all works out that way!

 

[Black_Bullet]

Yah i know what you mean. I had a full 3" exhaust on my old 1g talon and sometimes i wished i could've turned that drone down a bit...but just a bit

I was also thinking about getting the QTP cutout.

I like that electronic controller too so i dont have to guess what position the butterfly's at.

I also like that you can put presets in to fully open or closed or somewhere in between.

I was thinking of getting this also: Welcome to DMH Performance!

It says that you can open the butterfly at the flick of a switch... so I'm assuming there's somekind of preset system, which would be awesome because its only $200, whereas the QTP valve+ controller is about $300

I have the DMH Performance cut out its a bit cheaper.
I upgraded my stock piping to 2.5 for a little bit more flow, but left the stock muffler.
When the cutout is closed the car is stock quiet ( except for all the turbo, blow off noise.)

Now, you definitly will want to upgrade your downpipe to mandrel bent 3in.
I have the Megan btw. Just because the cutout gives you open dp performance, doesnt mean that stock Dp wont be a restriciton. The inlet itself is horrible, and despite flow being quicker when its hotter at the dp, your size of your DP plays the largest role in spooling characteristics and overall air flow potiential. Upgrade that DP and put the 3in cutout on it after wards.

When the cutout is open the car is pretty mean sounding, it has a musclar growl, and is much deeper than DSM's with reg. 3in catbacks. It is pretty loud, but since you can control how opened it is, you can tune the sound you want while driving. On the highway it isnt so bad, but driving in traffic in the city you'd likely not want you cutout opened to much.

To be honest, gas milage is so much better with it opened that I dont even bother closing it 60% of the time and this is my DD. Ive driven by many cops with it open and they didnt bother me. And it has saved me a few incidents with speeding were I closed the cutout as I seen some cops and they didnt mess with me. Leaving the stock muffler in back helps alot. I dont know how strict your state is about emissions ( no testing here ) but it is very illegal if you caught with a cutout on your car, so you might want to keep that in mind.
Keep your stock DP and switch it out for emissions and take off the 3IN DP w/ the cutout.

The controller that you get with the QTP is worth it though,
not knowing what position the plate is at can be a problem, because Ive noticed that when its not dead center ( 100% opened ) there is a slight lose of power, especially since I am running the stock muffler in the back for stealthness...

You may want to keep the cutout mounted behind the doors/windows to keep exhaust fumes from entering cabin. I had a problem with that for awhile.

As far as the flames under the car, yes its true, I have a lot more power than you do, but I noticed on cold nights with timing low and a rich tune my car would have a flame thrower under it....
Playing around with my friends Sti on the highway ( wont mention speed ) but as I was passing him
he later informed me that I was spewing under the car.
It will also spit fire if i use my NLTS and bounce off the rev limiter too long.
Under my car is a tad bit melted but more so covered in soot than anything. Im not worried about it.

Hope I covered everything, I will try to get you some pics or videos up later today or tommorow of how/ where my cutout is setup on my car.

Good purchase.

 

[alika86]

Thanks so much for the info Black Bullet! It's all very helpful

As for the downpipe...I've read on here that bottle-necking can hurt performance when the cut-out is closed. Wouldn't it increase backpressure to have a large pipe going into a small pipe instead of the other way around?

I've never done this kind of mod before so I'm just wondering how a large downpipe paired to a stock exhaust would flow. This is what you're running right? Do you notice a difference when the cut-out is closed or is it just like stock?

This was the whole reason I wanted to put the cut-out in a test pipe instead of a larger downpipe, but if there are no negative side-effects of putting a larger downpipe with a stock exhaust, I'd much rather do that.

I didn't buy the test pipe yet so I think I'll just get a megan downpipe instead.

It's REALLY great news to hear that gas mileage is BETTER with the cut-out. Gas here is about $4.55 for 92 octane premium...SUCKS. I already get relatively good mileage (20-22 MPG) seeing that I drive in about an hour of crawling traffic every day, so it's great that this mod will save me money in the long run, too.

That whole fire under the car thing still sucks though because I'm aiming to get to about 350-400awhp eventually and that would probably result in some flames. I'm gonna see if someone can weld me a slash cut piece of pipe on the top of the valve to redirect that exhaust to the ground. You think that would help?

Oh yeah... we don't have any emissions testing here and the rules about catalytic converters aren't very strict either. It's illegal to replace a working cat, but nobody actually checks if your cat is working or not anyway. So big plus for me

Yah those pics/ vids would be great man! thanks!

 

[fatherbubble]

RRE has a great setup there Downpipe an the Apexi N-1 85mm exaust all bolt up fits perfectly.

 

[alika86]

cool man thanks I'll take a look at those

btw.. anybody buy ebay downpipes? how's the fitment with those. I'm just trying to find a happy medium between price and quality.

 

[vanilla gorilla]

Regarding the flame throwing issue:
I'm running all custom open exhaust, no cat, no muffler on my srt4 and it shoot flames and black smoke. Thats why I have the exhaust routed out the side of the car, under the sideskirt, in front of the tire. This way it doesnt melt crap.
On my eclipse all I have is an Apex'i N1 downpipe for exhaust. No cat, no muffler again and its dumping under the car about mid ways the door. For this setup I made a stainless flange that bolts to the back of the Apex'i pipe, and I welded about a 60 degree turndown pipe onto the new flange. Slick setup, it directs the exhaust down, and I can unbolt it if I ever decide to add the rest off the N1 exhaust.

I like your idea of using an electric cutout. If I was doing it, the pipe that opens up when you open the cutout....I would have it directed out the side, then have the normal exhaust directed out the back as usual.

Good luck.

 

[alika86]

I was thinking of just welding a slash cut pipe on top of the cut-out to direct the gases down. That side exit sounds like a good idea though, so I don't melt stuff.

Still looking for a downpipe...Apex'i sounds good

 

[Black_Bullet]

Thanks so much for the info Black Bullet! It's all very helpful

As for the downpipe...I've read on here that bottle-necking can hurt performance when the cut-out is closed. Wouldn't it increase backpressure to have a large pipe going into a small pipe instead of the other way around?

I've never done this kind of mod before so I'm just wondering how a large downpipe paired to a stock exhaust would flow. This is what you're running right? Do you notice a difference when the cut-out is closed or is it just like stock?

This was the whole reason I wanted to put the cut-out in a test pipe instead of a larger downpipe, but if there are no negative side-effects of putting a larger downpipe with a stock exhaust, I'd much rather do that.

I didn't buy the test pipe yet so I think I'll just get a megan downpipe instead.

It's REALLY great news to hear that gas mileage is BETTER with the cut-out. Gas here is about $4.55 for 92 octane premium...SUCKS. I already get relatively good mileage (20-22 MPG) seeing that I drive in about an hour of crawling traffic every day, so it's great that this mod will save me money in the long run, too.

That whole fire under the car thing still sucks though because I'm aiming to get to about 350-400awhp eventually and that would probably result in some flames. I'm gonna see if someone can weld me a slash cut piece of pipe on the top of the valve to redirect that exhaust to the ground. You think that would help?

Oh yeah... we don't have any emissions testing here and the rules about catalytic converters aren't very strict either. It's illegal to replace a working cat, but nobody actually checks if your cat is working or not anyway. So big plus for me

Yah those pics/ vids would be great man! thanks!

Ok, to address a few of your questions.

When the cutout is closed performance will suffer a tad but may not be enough for you to care. The turbulence of the Y pipe of the cutout most likely, the 3in DP into stock exhaust doesnt hurt anything with flow. I dont run the stock piping anymore, I want to free up a little back pressure and I upgrade the stock piping to 2.5 going into stock muffler.
The car was a lot smoother after I did that at all times. Hell if you could get a 3in pipe going straight back into stock muffler that would be even better.

Whenever my cutout is closed I barely exceed 3500rpms, when its closed I am normally just cruising, my whole tune changes when it closes and I dont want to tune for the cutout not being open, if im going to do a pull I want to go fast obviously, so it makes no sense to be hammering the car with it closed...

Maybe 7 or 8 months ago i dynoed my car for the first time and I dynoed with the cutout closed and open both at 20psi falling to 17 with a 10.8 afr and 17 degs peak timing and a minor boost leak abd completely stock motor, the car laid down 225awhp and 271 ft lbs of torque with my cutout closed... So dont get me wrong there still is some power that can be made on stock muffler, but then with the cutout open the car did 271 awhp w/ 304 peak ft/lbs of torque... Thats a large increase in power right there. I have a video of that dyno by the way, ill look for it.
Right now I am def over 300awhp as since that dyno, I have added 272cams,AWD Laser 900rpm idle, BC272s - Video
fp race manifold, gm maft setup w/ CAI, another 3more psi, another 2-3 degs of timing, and a tad bit leaner afr... Car sounds/ pulls nice.
24psi by 3300-3400 rpms...

As far as fire under car again, just make a custom heat shield for it if you really concerned. I honestly dont care on mines, that cutouts been on the car for 2 yrs with no ill effects... Also how much power you produce has nothing to do with the flames.
I found colder air, long carried out highway pulls, bouncing off revlimiter, rich tune w/ low timing, that is what produces the flames... Otherwise you wont see any.
My new tune right now doesnt spit flames at all unless I do my NLTS; and its not really that bad.

Something else to add, my cutout went bad on me about 3 months ago and I had to replace it... I only had to do was order a new motor though from DMH for 40bucks, the old one had burnt out over the course of like 3 yrs of use ( it was on my friends car first.)
You just have to be mindful of not holding button to long when opening and closing it, but wit hthe one your getting you shouldnt have that issue.

Im working on videos.

 

[1gDSM4g63]

Looking are your profile of your car being completely stock, I really don't think you'll have to work about flame shooting out of the cut-out.