Downpipe / Exhaust question

[JAVO]

Do you think you answered your own question?
There is not, nor will there be a replacement "1st cat"/"downpipe" replacement.

There are high-flow cats out there but they are "main cats" and are not going to be fitted to a turbo exhaust housing.

The "pre-cat"/"1st cat" is the single biggest restriction to the turbo on the exhaust side.
If you removed only the cat at the turbo you'd still get a good boost out of it and see less lag.

That being said, no one half-asses this one, you either replace it with a straight(down) pipe or you leave the stock one so nobody is going to make a high-flow replacement, there's simply not enough demand to make it cost effective.

As far as answering my own question, I don't know. I'm looking for help, and knowledge. Not attitude.
I want the power gains but this is a daily driver and one I want to keep for a long time. I'm far too OCD to drive around with lights lit up on the dash (as someone mentioned it being a possibility) and when I have to renew my emissions I'm not terribly interested in it failing.
These have to be issues that others have faced. Does a custom flash wipe out / disable trouble codes triggered by not having the pre-cat? Is there an option to relocate the O2 sensor from the precat to just forward of the primary cat?

Lights on or failing emissions would be half assing it. This isn't NASCAR or Fast and Furious. I'm looking for little gains while maintaining and error free computer. It may not be possible. I'm not educated enough about the Sonic to know.

 

[laborsmith]

I have written this before but I think it bears repeating. The least expensive upgrade to improve 1.4t performance is to use premium fuel. To get the best advantage of a tune you will need to use premium fuel. Pete Basica got 124 then 125 HP to the wheel with no other mods than Grand Sport painted stripes and Pedders coilovers. OEM using regular fuel is widely reported to be 116 HP.

A freer flowing cat back exhaust will add HP, whether using regular or premium grade fuel and will not need a tune to get the best results.

I am not certain what gains a downpipe on its own would add and suspect on its own would be a lot of work for minimal gain.

Any other upgrades to improve performance will require a tune and one can get a significant performance upgrade just using a tune with no other mods.

Laborsmith

 

[sx sonic]

@ laborsmith I cannot see how it would provide minimal gains. And install time is under an hour with basic tools and a jack (requires O2 sensor socket, wrench may work if low miles). It is the most restrictive part of the exhaust followed by the 2nd cat. That's in terms of the core material and also I.D. of the piping. Removing smaller bottlenecks is not as effecient or effective as removing the largest one.. the ecm will likely tune itself back to stock output like it would with all mods but you will still have quicker spool times, mine does and I'm still stock tuned.

Trifecta can tune the ecm to ignore the service engine light (aka CEL or SES). I'm at over 200mi with the downpipe and still no light so it is possible it won't come on.. the ecm shoulda thrown a code immediately as its recording unchanged emmsions or at a minimum after 2 complete drive cycles which I've more than done.

What I meant to say about the warranty is that the downpupe should not cause any problems that will require repairs if properly installed (there's always the .1% chance). But the dealership will likely raise issues with you about warranty coverage. Depends on the problem and largely the dealer. Some won't give you any troubles about it unless it was a likely cause (I.e. CEL or turbo failure). Some dealerships will give you a hard time doing any warranty work with it installed even if its not related like a radio or abs problem. (I ran into this problem last week with just my ultragauge and cat back on). The only way to avoid that and that goes with almost any aftermarket mod is to remove it before taking it into service... put the stock one back on before you go in and you don't have anything to worry about..

I'm not trying to sway you in any directions and you have to way out what you want and what hassles your comfortable dealing with but there's my expierence and knowledge

-tyler

 

[Larry]

It's illegal to modify factory emissions systems that are still functioning properly. If you have a problem with one of your emissions systems you are allowed to replace it with a non-OEM product as long as it is compliant with your state laws.

 

[sx sonic]

Good point Larry. Some how I forgot about that one :O.
The only exception is if its intended for off highway use

-tyler

 

[JAVO]

It's illegal to modify factory emissions systems that are still functioning properly. If you have a problem with one of your emissions systems you are allowed to replace it with a non-OEM product as long as it is compliant with your state laws.

hahaha. Are you a lawyer?

 

[Eric Smit]

hahaha. Are you a lawyer?

He's an officer of the law.


-Eric Smit

 

[Opticon]

Restrictive exhausts are against my religion. I have to remove power-robbing emissions equipment to achieve nirvana.

 

[laborsmith]

@ laborsmith I cannot see how it would provide minimal gains.

-tyler

I believe putting in a downpipe but keeping the rest of the exhaust will not have a great effect on performance. I could be wrong. Replacing the whole system from the manifold to the tip with a freer flowing system should result in higher performance gains than just a cat-back.

Laborsmith

 

[JimmyBuckets]

Vermont Tuning 1.4T Turbo Upgrade - Flows 22lb/min Vs 18lb/min with Stock Turbo

Besides the turbo upgrade part there are some important bits about the stock vs upgraded exhaust.

 

[laborsmith]

Good find, Jimmy. Wonder where he got the 210 limit for the clutch. I think the 237 for the tranny is a typo as 236 is the official GM number for all iterations of the 6 speed manual tranny used in the Sonic.

As I have posted in other threads, Brian has a very good reputation. The biggest difference between Vermont Tuning and Trifecta Performance is the former does mods and tuning and the latter tunes to accommodate mods developed by others.

Laborsmith

 

[JimmyBuckets]

I'm not sure where he gets all is info, but Brian is very open about what and how is does things...which I like very much. There is GM site that has all the trans and engine info for US and Europe...I think you are right about the 236 limit.

 

[sx sonic]

i just dont see the cat back being that restrictive, compared to the 1st and 2nd cat.. just in terms of the smallest O.D. pipe size the 2nd cat is the most restrictive followed by the 1st cat/downpipe, coupled with the core of the catylytic converter and the fact that the DP has the shrapest bends, it would seem that putting only a cat back exhaust on would do nothing but add sound (which is satisfying).

the way im looking at it is like an assembly line, lots of parts coming in. the guy taking parts in is competent (turbo/header). the next guys slow and loses parts (downpipe). the forklift operator is workman like and a decent speed (flex pipe). the 1st machinist messes up half the parts and has to rework em (2nd cat). the heat treat guy is always running his production #s (resonator) and the recieving guy usually naps an hour a day but otherwise works ok (muffler). now your the manager which Guy would you replace first??? if you replace your heat treat guy he's still gonna get the parts slowly and messed up. if you replace the 2nd guy in the line thats slow and messing up then everyone else will get more parts!

thats just the logic i'm looking at it and i like analogy's lol I do agree a full exhaust would be required to take full effect of any mods, however it would seem replacing the most restrictive components first would yield the most results as any component after it would not be as detrimental to the overall scheme of things.

it is possible i could be wrong, i am by no means an expert in this, just a young punk who does alot of research, tinkering, and trial and error.
and i hope you do not take this as me calling you out or anything of that nature, you've attributed alot of great things to this site and informed me of many things, i just dont fully agree with you on this one

-Tyler

 

[JimmyBuckets]

Or maybe business is so slow that they are all standing around doing nothing (exhaust being plenty large to flow properly)

 

[laborsmith]

i just dont see the cat back being that restrictive, compared to the 1st and 2nd cat.. just in terms of the smallest O.D. pipe size the 2nd cat is the most restrictive followed by the 1st cat/downpipe, coupled with the core of the catylytic converter and the fact that the DP has the shrapest bends, it would seem that putting only a cat back exhaust on would do nothing but add sound (which is satisfying).

I have dynoed it. The DDMW 2.25 cat back added about 25 WHP.

There are a bunch of dyno charts posted in the DDMWorks section which is in the Venders Section. The thread has "dyno charts" in the title.

Laborsmith

 

[sx sonic]

as i said i could be wrong. i would not expect a cat back exhaust to yield that much hp in gains, that is surprising to say the least.

Jimmy buckets you made me lol alil bit haha

-tyler

 

[laborsmith]

Me too. And this was not a one time occurrence. Two separate days over a month apart, but the oem exhaust is 1.825 for the most part so the improvement is understandable. Also, I believe the exhaust is 2.25 from the manifold thru the cats before going to 1.825. I am busy tomorrow so I won't be able to check until tomorrow evening or Thursday.

Laborsmith

Why so restrictive? Fuel economy. You give up 1 or 2 mpgs by going to a bigger exhaust.

 

[rdss]

Yeah, the pipe necks down right off of the second cat before the flange for the cat back.

Stock pipe vs 2.5" pipe.

 

[sx sonic]

purdy pipe haha. cool pic RDSS. is that the SLP 2.5 exhaust you put on your car? (i believe that was the name of it)

-tyler

 

[sx sonic]

nvm just saw it on you build thread