BOV and exhaust system question.

[Guest]

Hi there!

noob here...

Sorry if this is a re-post! been trying to use the "search" can't find it.

i have a 00' turbo forester... planning to put a bov and custom exhaust system.

now, i googled, and found out that a stock Subaru engine hates aftermarket blow off valves, no matter what sort of brand it is. is this true?

therefore, people in states etc, uses or focusing on CAI. (which apparently, from them: you can hear the ppkssshh sound) also just found out about INTAKE SILENCER DELETE MOD....

have you guys done any of this?

also, for exhaust system, will taking off the catalytic or stock reso to pipe it will perform the subaru rumble?

[Timmah]

I think you'll find a few of us here have aftermarket BOV's on our cars. It's not bad for them the only problem with having one the vents out (making that noise) is that it can sometimes make the car run a bit rich when changing gears.

I'll let someone else answer you exhaust question, but on my car, I still have the stock system with cat converters, just a STI model muffler which gives it a nice rumble

[pl0x]

I got a gfb hybrid,

drove round with standard, then put the gfb in and used it in 50/50 for ages then changed to full vent and didn't notice a difference

[nickch]

 pl0x said:

I got a gfb hybrid,

drove round with standard, then put the gfb in and used it in 50/50 for ages then changed to full vent and didn't notice a difference

have the same BOV..

was running 50/50.. it still went rich between gear changes..

have screwed the bung in the make it fully recirculated, it still runs a bit (less but still) rich between gear changes...

and with the silencer delete, I get a quick and discreet hiss with a bit of a high pitched whistle..

the 'woosh' is louder with the stock BOV + silencer delete..

[Guest S T E Y E]

i dont get trouble from running a atmospheric vent on my hks ssqv... only thing to watch for is if u set the bov adjustment too loose itl hang open and stall when u come to a stop....say at the lights...

the theory is dat a atmo venting bov will run rich wen its blow off valving because the afm is registering all the air going in and adjusting air fuel ratio to suit and wen u let it out to the atmosphere the afm has registered that air so the engine wont see the air so it will run rich...

if that makes any sense to u???

a pod filter will make the plumback bov louder as u will hear it more

but seriously its allright to run a atmo bov as long as u set it up right

as for exhaust if u want suby rumble then change downpipe to a catless one and if u want it nice and deep put resonators in instead of mufflers it all comes down to what u want from ur car really

i run a 3 inch downpipe to a straight through 3 inch exhaust with only a rear muffler (resonator) and the suby rumble is pure mint

[nickch]

==edit==

grah.. i just re-read this post.. don't mind me.. i think i need more sleep.. ><

[Guest]

so, got myself a 3"inlet xforce cannon, and a resonator with 3" both ends...

im planning to replace my catalytic with reso, is it a good idea? also, will Vtnz, pass it? as im thinking of going vtnz for my next wof....

thanks!

[Pappu1]

should pass as long as its not too noisy.. thats what seems to be the norm.. altho if u get an anal inspector then sometimes they dont like the noise and put it as too exxesive

[nickch]

 pappu said:

should pass as long as its not too noisy.. thats what seems to be the norm.. altho if u get an anal inspector then sometimes they dont like the noise and put it as too exxesive

;D

[Guest S T E Y E]

well the rules are 94db at 4000 rpm yea?

my 3 inch would defonatly FAIL that soo bad...

silencers your best freind....

but i find with my noisy ass exhaust the silencer wont cut it so wat ya do is ram heapsa steelo wools up the exhaust then put the silencer in...

quiter than standard

pass the wof and pull it out yeaya

[LAtitudeNZ]

AFAIK the dB limit is 90.

Would love to be proven wrong and it be 94dB, as this would then make my car legal.

[Ninja8)]

+1 to 90DB.

[Guest]

http://www.nzta.govt.nz/consultation/vehicle-equipment-noise-amendment/draft-vehicle-equipment-noise-amendment.html

this was the 2009 draft, cant find anything newer on the law. but i think the bottom table is what you want

this was due for release in may 2009, not sure if it happend though

-smurff

[Guest S T E Y E]

hmm i do remember something in the rule book about 90db AND 94db was something to do with which year of first register in nz im pretty sure can someone confirm?

[Guest S T E Y E]

yea thats out of date as wen Db testing first started it was 96db...then 95db...then 94db

gosh can they make their mind up

silencer for the wof = WIN haha

[sultan]

there's no need for a 3inch all the way. i had a full 3 inch with two resos and a big bore, it was noisy as hell. i now run a 3inch down pipe to standard 2.5" mid section to standard 2.5" rear section with a smaller straight through muffler. sounds fantastic and isn't noisy. not restrictive at all either.

[Guest S T E Y E]

a 3 inch with no resonators will allways offer better performance / turbo spool than a 2.5 inch with resonators and mufflers etc...

less back pressure the faster the turbo will spool

(in theory anyway)

but before thinking performance its about what the owner wants it to sound like / loudness

and i would never trade my straight 3 inch for anything else haha love the deep pure mint sound

[pl0x]

 S T E Y E said:

a 3 inch with no resonators will allways offer better performance / turbo spool than a 2.5 inch with resonators and mufflers etc...

less back pressure the faster the turbo will spool

(in theory anyway)

but before thinking performance its about what the owner wants it to sound like / loudness

and i would never trade my straight 3 inch for anything else haha love the deep pure mint sound

wrong

[Guest S T E Y E]

care to explain then?

[Guest S T E Y E]

heres a little thing to put into the mix

heres the link

http://www.tercelreference.com/tercel_info/turbo_exhaust_theory/turbo_exhaust_theory.html

and heres some quotes

This thread was brought to my attention by a friend of mine in hopes of shedding some light on the issue of exhaust size selection for turbocharged vehicles. Most of the facts have been covered already. FWIW I'm an turbocharger development engineer for Garrett Engine Boosting Systems.

For turbo cars, you throw all that out the window. You want the exhaust velocity to be high upstream of the turbine (i.e. in the header). You'll notice that primaries of turbo headers are smaller diameter than those of an n/a car of two-thirds the horsepower. The idea is to get the exhaust velocity up quickly, to get the turbo spooling as early as possible. Here, getting the boost up early is a much more effective way to torque than playing with tuned primary lengths and scavenging. The scavenging effects are small compared to what you'd get if you just got boost sooner instead. You have a turbo; you want boost. Just don't go so small on the header's primary diameter that you choke off the high end.

Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure.

Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve engine VE throughout the rev range.

[Guest S T E Y E]

now going by my small statement off less backpressure is better this garret man seems to back me up 100%

[Guest]

Back to back tests have shown going to 2.5" back end do not restrict power in some cases.

In some engines the 2.5" increases torque and power lower in the power band.

It obviously depends on your power levels tho. I suspect for most people 2.5 will be fine and a better all round car to 220kw.

An interesting example - about 15psi

[zarnah]

hmmmm, well I do remember having a looksie under a wrc car once , think it was a focus, and was shocked at the tiny pinner exhaust it had was maybe 2 inch definately not 2 1/2 anyhow, and those things spool like fuck!

[Guest S T E Y E]

haha wrc cars and all other rally cars are all restricted to a 2 inch exhaust as far as i know... a mate has a group N and has turbo inlet restrictor and restricted exhaust size...

plus as for the spool... WRC cars run LINK ecus with antilag lol

[Guest S T E Y E]

as for the 2.5 inch to 3 inch...also depends on turbo ur using??

but defonatly less back pressure = better...that right up from mr garret man is really good stuff