Open Downpipe

[SpoolinTalon2]

Hey I have a couple questions about running open downpipe.
-What are the benefits and drawbacks of it?
-If you run open downpipe, will your o2 sensors be reading check engine?

thanks guys.

 

[pnishr]

benefit: AWESOME sound. (LOUD)
Good power. (WAY less backpressure)
Scare your neighbors
Cons: LOUD
Illegal (emissions)
Scare your neighbors
Hot exhaust gases coming out under your body.

I don't recommend doing this for a daily driver. But at the track, go for it.

Yes, your ECU will (should) throw a code for your rear 02. I have an Apex'I N1 with the very last piece off right now (while I work on the car) So, no muffler, just resonators and a 3". It sounds like a friggin v8... beautiful.

 

[SpoolinTalon2]

Alright. Thanks.

 

[nightspeed87]

i was considering doin this but im scared its going to be too loud and get me a ticket. Maybe ill just take it off and see how it sounds and if its too loud throw it back on. Does your turbo spool faster with open downpipe?

 

[pnishr]

Yes, it seems that mine does. anything that will open up the exhaust should.
Also, another con: you'll probably get serious boost creep with that much backpressure removed. I creep up to about 20.6psi- on a T25 (no knocking though, so I'm not worried yet) but it will kill that turbo quick, and you won't be making any more power even if you're not knocking.

Edit: I went temporarily retarded, and misnamed SPIKE with CREEP. yes, creep will not happen. I SPIKE to 20+ psi, not creep. Sorry about that. And thanks to No Skillz for typing the reality.

 

[SpoolinTalon2]

Hmmm. Is there any way of avoiding that backpressure? Ya I did open downpipe on my friend's ride and it sounds sick as hell. Some more questions:
-Will a wideband work fine with open downpipe?
-So open downpipe will make your check engine light come up but will it kill your o2 sensors?

Thanks

 

[pnishr]

No, the lack of backpressure is WHY you would take off the exhaust. It allows exhaust gas to escape more quickly= more flow= more HP.

I run my WB 02 in place of the front stock one, so yes you can use WB. but if you were planning on using it as a secondary, removing that rear piece of exhaust will remove the bung you were going to put it into.

As far as hurting the sensors, no. you'll need to either remove or tie up somehow (so it doesn't drag) your rear 02. you may not throw a code, but you probably will. The sensors are not harmed.

 

[Byrd]

I ran open for a while. You will sound like a hoss truck around 2K-3K rpms but smooths out when your coasting. The people behind you will smell the lovely aroma of gas . When yI was not boosting i was hella slow from lack of backpressure, but during boost it was dirty.

 

[nightspeed87]

I ran open for a while. You will sound like a hoss truck around 2K-3K rpms but smooths out when your coasting. The people behind you will smell the lovely aroma of gas . When yI was not boosting i was hella slow from lack of backpressure, but during boost it was dirty.

in your own experience how loud was it though'?
Some people say its crazy loud to were cops will be after you.
Was this the case for you.
And I have a 14b havent upgraded my turbo yet,
so how could I contain that boost creep were basically it wouldnt happen.
Will a mbc be able to control boost creep or boost spike from open dp.

 

[No_Skillz]

You will not creep with a stock turbo or a properly ported larger turbo. MBC will not control creep... you can avoid spike by connecting it correctly (via j-pipe instead of bov tee).

Byrd - please read some of the threads about backpressure. Your assumption about backpressure helping low end power is a common misconception.

 

[Byrd]

in your own experience how loud was it though'?
Some people say its crazy loud to were cops will be after you.
Was this the case for you.
And I have a 14b havent upgraded my turbo yet,
so how could I contain that boost creep were basically it wouldnt happen.
Will a mbc be able to control boost creep or boost spike from open dp.

This is gonna sound a little out of place on this forum. But i used to have a cougar and i had a 2.5" inch all the way through with gutted cats and it, to this day, is louder then just a open dp.

The sound from an eclipse is alot like a truck though, not raspy but it's got that raw sound (best word i could think of atm). I'm using a megan racing DP btw. Cops will be after you at low speeds but on the highway your ok. My buddies '06 sti with 3" back is louder at cruising.

High rpm pulls it sounds straight mean! if i could keep the full spool high-rpm sound i would but the low rpm is very annoying and not worth it.

No_boost - I said i was slow from lack of backpressure, there's a point where lack of backpressure can hurt - you might have read me wrong or i'm just a complete idiot and my butt dyno is broken.

 

[krazy4]

do it
ohhh... also dump the wastegate and scare the hell out of everyone

 

[nightspeed87]

yea i like that rapsy sound turbo dsms make though when you do that.
Makes ppl not knowing think you have a bigger engine than you have so
when you beat them there baffled because their v6, or v8 just got spanked by a 4.

 

[SpoolinTalon2]

So it sounds like running open downpipe will give you quicker spool but kill your turbo faster? Is there any way of avoiding your turbo to die at a quicker rate? Thanks.

 

[nightspeed87]

how do you combat boost creep more like is what you mean?
Any answers?>

 

[Byrd]

Yea, open DP in general won't kill your turbo. But boost creep that you'd get from open DO i'd assume would kill more then just your turbo.

But Boost creep would not happen every time, every car, on all DP's - just to clarify

 

[Wicked96GS-T]

If you want to run an open downpipe, but don't want cops chasing you, look into an electric exhaust cutout. Open it for power and sound, and close it for stealth and legality around police.

 

[SpoolinTalon2]

My friend and me are running open downpipe on his car right now (t-28 with stock downpipe). do you guys reccomend he just slap on a 3" turbo back with no cat or its ok to run open dp with that turbo and dp? Thanks.

 

[No_Skillz]

My friend and me are running open downpipe on his car right now (t-28 with stock downpipe). do you guys reccomend he just slap on a 3" turbo back with no cat or its ok to run open dp with that turbo and dp? Thanks.

I suggest making the car emmissions legal. DP and 3" cat is a good choice. I don't want my grandkids sucking in noxious fumes when they are born.

Like I posted earlier... you won't boost creep with a stock turbo or a larger turbo with proper porting. For more info about creep, do a search.

 

[SpoolinTalon2]

Is his turbo being killed faster with his downpipe open right now? (t-28 turbo with stock downpipe) Thanks.

 

[No_Skillz]

If you are maintaining good boost levels and there are no tuning, smoking, knocking, or bogging problems, no. A turbo is potentially more vulnerable to damage from the intake side of the engine from boost leaks. Do a test.

 

[StimpsTSI]

I just wanted to say that my brother used to own an sr20det swapped nissan 240sx, and he was running open downpipe for about a month. It sounded good as hell, just like a dsm open downpipe, but he was pulled over and forced to buy an exhaust. He was lucky that he knew the cop. When he had it running open dp it boosted much faster, and he used to get looks from people like he had 2 heads, but his t-25 spiked to about 20 psi all the time.

 

[olmytsi]

I have run open 02 housing and never got a rear 02 sensor check engine light but evry car is different. I never got one when i got rid of my cat either and i know the sensor works because i bought it new last year.

 

[zilo900]

I have my n1 downpipe disconnected right now. Im putting it back tomorrow, for same reasons as above. It is ungodly loud below about 3k rpm, it makes the car have crappy low end, but awesome top end. The boost doesnt hit full until about 3800 and i have an evo3 16g, and then the whole thing about being worried about cops and the damage all that exhaust gas is doing directly under the car. And people can argue all they want about the effects of doing it but ill be posting my times in the 1/4 with and without the catback attached in my thread in the tuning section tomorrow.

 

[olmytsi]

Yeah you loose some low end.