open downpipe

[nyk4life]

hey i have a 99 gs-t, i just made my down pipe open but i dont really hear the whistlin of the turbo? its a stock turbo and stock dowpipe.

99 gs-t
injen intake, greddy exhaust,highflowcat,hks ssq bov,msd wires,grounding kit.

 

[fourreGsixty3]

Having an open DP probably drowns out the turbo spooling. Also fix your punctuation. It goes a long way on here to spell correctly, and have proper punctuation.

Dustin

 

[JayRolla]

Do you have a boost guage, if not the open downpipe may cause the turbo to creep.

 

[nyk4life]

i dont have a boost gauge and ive been reading about"boost creep" so i am going to bolt it back up tomorow mornin.

 

[funkbuster]

I was running my 93 talon with an open downpipe for a few weeks. My turbo sounded like a dump truck, mine is bone stock. I put it back together due to some major boost creep. I was maxing my stock guage out.

 

[JayRolla]

Im not sure, I know the 14b on the 1g will creep but not sure about the t25. But ive heard all mitsu turbos can creep.

 

[DSM602]

if your not boosting up more than stock, then you wont have to worry about boost creep right? correct me if im wrong. my 97 gst (t25) is all stock besides intake with open downpipe, and my boost max's out where it did with the downpipe on. i dont feel, hear, or see anything abnormal.

 

[kmoore]

if your not boosting up more than stock, then you wont have to worry about boost creep right? correct me if im wrong. my 97 gst (t25) is all stock besides intake with open downpipe, and my boost max's out where it did with the downpipe on. i dont feel, hear, or see anything abnormal.

Yeah... that's incorrect. You can creep at any psi (stock or above stock) if you have something that is creating your turbo to creep (open downpipe, etc.)

 

[7"exhaust_tip]

im running open downpipe until wed when i can reinstall my cat back. and i can say....sheez the turbo de spooling is loud as anything.

also it boost creeps to like 19psi on the t25. yikes!

 

[Joshuaevansmith]

Has anyone ran a 3" DP and welded a magnaflow or other high flow muffler to it with a turn down? I'm considering this set up and leaving my stock muffler n place for aesthetics. Should be a significant power gain and I'm hoping the nose won't be awful with the muffler.

 

[2gmitsueclipse]

Do you have a boost guage, if not the open downpipe may cause the turbo to creep.

A boost gauge has no bearing on whether or not you will experience boost creep. It can happen with, or without a boost gauge.

 

[Joshuaevansmith]

A boost gauge has no bearing on whether or not you will experience boost creep. It can happen with, or without a boost gauge.

2gmitsueclipse, Do you have any opinion on the muffler after downpipe I referred to? I was surprised I did not find mention of several folks doing this upon searching. I see people doing open downpipe, but I would think the muffler would be a simple install using the cat hangers and would help solve the noise and boost creep issues I see everyone talking about. Would love to hear your thoughts.

 

[2gmitsueclipse]

2gmitsueclipse, Do you have any opinion on the muffler after down pipe I referred to? I was surprised I did not find mention of several folks doing this upon searching. I see people doing open down pipe, but I would think the muffler would be a simple install using the cat hangers and would help solve the noise and boost creep issues I see everyone talking about. Would love to hear your thoughts.

You are likely not going to find much information about this because many do not route the exhaust this way. Unless this car is specifically for drag racing, then I would not run the exhaust out the underneath the car as a permanent solution. Otherwise, you are going to get headaches from listening the car, and attract unwanted attention. This is on top of being emissions compliant and the health issues with exhaust exiting underneath the car (sitting in traffic). There really aren't enough gains performance wise to delete most of the exhaust unless you are looking to extract every ounce from a setup.

Off the soapbox...

Obviously, one of the best ways to regulate boost creep would be to go to an external wastegate. Other options include:

• Porting the wastegate flapper hole.
• Slight grinding the turbine housing to allow more movement of the flapper arm.
• Increase the flapper size to 34mm.
• upgrading/modifying/shimming the wastegate gate actuator.
• Porting o2 housing.

To address your exhaust:

• You could use an electric cut-out so that you can have the exhaust route under the car when you want to.
• Just stick to a 3in exhaust from the o2 housing back. It is up to you on resonators, catalytic converter, and mufflers.
• Use a flange or coupler to join the muffler under the car, so you can swap it out for a pipe that connects to the rest of your exhaust when you tire of the exhaust noise.

If you insist on keeping the downpipe/muffler combo, I would look into a bullet style muffler as they have a small frame (space) and very nonrestrictive. Granted, most people use these in cases where they MUST have a muffler for competition, or need to slightly lower the decibel level for a track (road course, dirt track). They look something like this:

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[Smilinjay]

Im surprised you cant hear any spool noise. Mine sounded like a semi with open down pipe. If you plan to stay open dp for a long time, I would keep a few things in mind (obnoxious noise aside). Like others said, you will get crazy boost creep. On an externally gated 20g I was creeping from 14 psi all the way to 23. Also, unless you get some sort of turn down the bottom of your car will get completely covered in carbon. Ill tell you from personal experience it gets pretty old after about 500 miles.

 

[Joshuaevansmith]

You are likely not going to find much information about this because many do not route the exhaust this way. Unless this car is specifically for drag racing, then I would not run the exhaust out the underneath the car as a permanent solution. Otherwise, you are going to get headaches from listening the car, and attract unwanted attention. This is on top of being emissions compliant and the health issues with exhaust exiting underneath the car (sitting in traffic). There really aren't enough gains performance wise to delete most of the exhaust unless you are looking to extract every ounce from a setup.

Off the soapbox...

Obviously, one of the best ways to regulate boost creep would be to go to an external wastegate. Other options include:

• Porting the wastegate flapper hole.
• Slight grinding the turbine housing to allow more movement of the flapper arm.
• Increase the flapper size to 34mm.
• upgrading/modifying/shimming the wastegate gate actuator.
• Porting o2 housing.

To address your exhaust:

• You could use an electric cut-out so that you can have the exhaust route under the car when you want to.
• Just stick to a 3in exhaust from the o2 housing back. It is up to you on resonators, catalytic converter, and mufflers.
• Use a flange or coupler to join the muffler under the car, so you can swap it out for a pipe that connects to the rest of your exhaust when you tire of the exhaust noise.

If you insist on keeping the downpipe/muffler combo, I would look into a bullet style muffler as they have a small frame (space) and very nonrestrictive. Granted, most people use these in cases where they MUST have a muffler for competition, or need to slightly lower the decibel level for a track (road course, dirt track). They look something like this:

You must be logged in to view this image or video.

Appreciate the thorough response. It's a weekend driver so I don't want obnoxious exhaust. I just figured as long as there was a muffler, it would be manageable.

 

[buhay6]

I wouldn't run open down pipe again! I found out I was hitting 20 psi by 2800 rpm on my ported 14b and was un-able to control my boost period! But unlike you all I heard when ever I hit the throttle was turbo spool. Only way I could control my boost again to an extent was to reinstall my factory down pipe.
Like Nate said for the hassel is causes your better off keeping the down pipe in place and and external WG is the best way to control boost.

 

[Lowestform]

On the first 3g colt that I swapped a 4g63t into I ran a large blue bottle glass pack style muffler with a turndown on it. The muffler was maybe 18" long, and welded directly to the downpipe to catcon flange. It worked well. Wasn't TOO loud. This was 15 years ago and I'm old now. I wouldn't do it now.

I didn't have any boost control issues either with a ported 14b/1g ported o2 housing. I do really the smell in traffic would get to me though.

 

[Joshuaevansmith]

On the first 3g colt that I swapped a 4g63t into I ran a large blue bottle glass pack style muffler with a turndown on it. The muffler was maybe 18" long, and welded directly to the downpipe to catcon flange. It worked well. Wasn't TOO loud. This was 15 years ago and I'm old now. I wouldn't do it now.

I didn't have any boost control issues either with a ported 14b/1g ported o2 housing. I do really the smell in traffic would get to me though.

Thanks, very helpful information. Boost control was my main concern. Luckily, I'm in central Illinois and we don't have traffic here, so that shouldn't be a problem.