twin scroll exhaust

[lunchie]

Hey guys I am trying to learn a bit more about the car I intend to buy soon (and the parts I will fit to it :P). (Probably )

If we assume I am looking at a v8-10 jdm sti then I have a few questions about the exhaust.

http://www.fortyone.co.nz/parts/view/19058.html

This link shows a tomei replacement downpipe for a jdm twinscroll sti.

In the picture it looks like it has two "plug in points" for O2 sensors, one right at the top where the turbo bolts on and one just before the end.

My questions are these

1st. Do the twin scroll sti's have two O2 senors?

2nd Do they only have one cat converter as pictured in the tomei photo or is there another one later in the system.

3rd. if there are two O2 senors then does the position of the O2 "plug points" on the tomei down pipe match up with the factory positions for an sti so the O2 sensor would still plug in as factory?

4th. Would the end of this piece (the tomei one) be where you bolt an aftermarket cat back exhaust to or is there another section of exhaust needed first?

5th. what do you guys think of the overall design of the tomei piece?

TY for any input

[Guest]

for starters i wouldnt be looking at a aftermarket pipe to find out what the factory one has. the aftermarket scales 3" down pipe i had only had one at the rear. you can always extend wires if you need to. from the look of that down pipe and the end on it i would say it bolts straight up to factory mid section. tomei seems to be a good name and widely used in america from what ive seen.

may help http://www.iwsti.com/forums/gd-exhaust/153473-help-identifying-exhaust-6.html

[lunchie]

still, anyone that can answer these 5 q's would be great

[Miller]

Hey

I have a Version 9 Sti. So here goes my attempt to answer your q's..

1 - Yes, mine has 2 o2 sensors. One right behind the turbo, and one at the other end like pictured.

2 - No the factory down pipe has 1 cat, and another small muffler (I think) in it.. Definatly 2 mufflers in it though, but one 1 is a cat i believe.

3 - Yes, looks to be in the exact right place

4 - Yep, if you get an exhaust for the right model, it should bolt straight up to the downpipe.

5 - Only thing i can see wrong with it straight away, is that it steps down to the factory size exhaust at the end, so if you get an aftermarket 3" exhaust, it will have to step down to factory size as well to bolt up.. But you could chop the flange off, and get a new 3" one welded on, bit of work, but not to hard to do.

Cheers

[lunchie]

 Miller said:

Hey

I have a Version 9 Sti. So here goes my attempt to answer your q's..

1 - Yes, mine has 2 o2 sensors. One right behind the turbo, and one at the other end like pictured.

2 - No the factory down pipe has 1 cat, and another small muffler (I think) in it.. Definatly 2 mufflers in it though, but one 1 is a cat i believe.

3 - Yes, looks to be in the exact right place

4 - Yep, if you get an exhaust for the right model, it should bolt straight up to the downpipe.

5 - Only thing i can see wrong with it straight away, is that it steps down to the factory size exhaust at the end, so if you get an aftermarket 3" exhaust, it will have to step down to factory size as well to bolt up.. But you could chop the flange off, and get a new 3" one welded on, bit of work, but not to hard to do.

Cheers

are you sure the step down would matter? I mean as long as the flange at the end of the pipe is big enough to support a 3inch pipe would it really matter? The 3 inch pipe would just go over the top of the small bit sticking out?

[Stoffa]

yes the step down will make a difference, why not just save $8-900 and buy a mild steel rage one? if you want a 3 inch buy a full 3 inch, you dont need to buy one with a cat, it hurts performance.

[Guest]

doesnt any car after 1996 legally require a cat? anyone confirm? i dont run one and never have but i dont use warrant inspectors who do balls out checks...

[lunchie]

 Stoffa said:

yes the step down will make a difference, why not just save $8-900 and buy a mild steel rage one? if you want a 3 inch buy a full 3 inch, you dont need to buy one with a cat, it hurts performance.

have to have a cat for it to be legal.

[Stoffa]

I dont have a cat in my version 5 and I passed a cert and many wof's without one

[johnny5]

not in NZ maybe Oz but not here I don't run one at all

[Guest]

i dont think wof inspectors are too picky but its still illegal afaik. ive never had an issue either

[Kiwi_Fozze]

Cats are not yet a wof (or legal) requirement in nz iirc.... Unless you have a warning on your dash. If you have a warning light, beat be getting it fixed.

[lunchie]

ah indeed, you are right I was reading the LTSA site but it was regarding cars that had an engine swap.

So yeah atm I dont think cats are a legal requirement.

[lunchie]

Ok guys I have one more question.

Are there ANY differences between the rods/pistons in the V7-11 2ltr sti's

Was reading on a Aussie forum that the V7 had the best rods/pistons?

Basically just wondering which version would be best for max hp on stock block?

[ADIKT]

 lunchie said:

Ok guys I have one more question.

Are there ANY differences between the rods/pistons in the V7-11 2ltr sti's

Was reading on a Aussie forum that the V7 had the best rods/pistons?

Basically just wondering which version would be best for max hp on stock block?

How much HP do you plan on making?

[lunchie]

Well this may sound stupid but when I was 19 I got to take a 2007 RS4 out for a drive. The combination of power and handling redefined the way I thought about how a car should and could drive. Since then I have always wanted and tried to find a way to recreate that sensation but with a car thats within my means.

The RS4 makes 320hp atw in factory guise.

That is how much power I want atw from my STI.

it works out to 240kw atw.

Do-able?

[funkytown]

just a quick note on the delivery of that power. While what you're saying makes lots of sense bear in mind a couple of things. Btw im not dissing what you want to do - i get it and the way you're approaching it is reasonably well thought out.

just FWIW:

RS4 is a v8 - it makes power and torque very differently to a 2.0T 4 banger.

the RS4 i'd pick weighs bucket loads more than an STI and will change how it handles, accelerate and stops etc.

Anyone you know with a 230-250kw subbie you could get in for a ride coz that will tell you with more certainty what you really want.?

In terms of doable, a factory v8-10 is capable of 230-240atw in factory form, its right on the limits of the injectors, rods and turbo but should just get there. for reliability id be hunting out a set of forged rods and pistons at some point.

also an as aside, i have access to a couple of 300kw cars, across a GD and GC chassis, its really interesting how the weight and motor difference makes 300kw feel very different.

[lunchie]

 funkytown said:

just a quick note on the delivery of that power. While what you're saying makes lots of sense bear in mind a couple of things. Btw im not dissing what you want to do - i get it and the way you're approaching it is reasonably well thought out.

just FWIW:

RS4 is a v8 - it makes power and torque very differently to a 2.0T 4 banger.

the RS4 i'd pick weighs bucket loads more than an STI and will change how it handles, accelerate and stops etc.

Anyone you know with a 230-250kw subbie you could get in for a ride coz that will tell you with more certainty what you really want.?

Yeah I totally understand that, the RS4 weighs 1620 KG. And I know what you mean about the differences between the two in terms of power delivery.

In terms of cars I have driven? I have spent a good few hours flogging a stock v9 sti, and have spent a bit of time in h8evo's wrx when it was making around 300kw atw.

Also my flatmate owns a v6 RA.

I know the sti wont make power down low or sound or feel just the same as that rs4 but I remember the way the car accelerated, that is what I want.

The factory handling of the STI is I believe more than a match for the rs4, its just the power that I need to match.

[funkytown]

 funkytown said:

In terms of doable, a factory v8-10 is capable of 230-240atw in factory form, its right on the limits of the injectors, rods and turbo but should just get there. for reliability id be hunting out a set of forged rods and pistons at some point.

also an as aside, i have access to a couple of 300kw cars, across a GD and GC chassis, its really interesting how the weight and motor difference makes 300kw feel very different.

[lunchie]

 funkytown']

[quote name='funkytown said:

In terms of doable, a factory v8-10 is capable of 230-240atw in factory form, its right on the limits of the injectors, rods and turbo but should just get there. for reliability id be hunting out a set of forged rods and pistons at some point.

also an as aside, i have access to a couple of 300kw cars, across a GD and GC chassis, its really interesting how the weight and motor difference makes 300kw feel very different.

/quote]

have you seen this?

http://rusubaru.com/goquality-specs/

[lunchie]

Spoke with STM today, they have installed a bolt on HKS turbo on v8 sti and tuned to 270kw atw with totally stock internals. They recken that is about the limits of the factory block tho.

[Guest]

 Stoffa said:

I dont have a cat in my version 5 and I passed a cert and many wof's without one

+1 no cat in my rs either. full 3 inch with one resonator.

also do consider the flow effects of a 3" and make sure thats what you are after. i used to have a 3" downpipe to a 2.5" mid section to the end and my boost came on around 2K ish RPM and full boost till 6.5K ish and then it would die out but since fitting my 3" i start boosting around 2.5 - 3K and got boost till pretty much redline. so if you are after quick spool and acceleration, a 3" to 2.5" imo is pretty mint. but if you do a lot of highway driving you will prefer the full 3" also depends if you like drag racing or circuit and ultimately wat sort of rev range you drive around in.

cheers muhammad

[Guest]

dont the V8 etc all the same shortblock as the V7? just different heads? not too sure just thinking out loud here

[pl0x]

 VADZTER said:

dont the V8 etc all the same shortblock as the V7? just different heads? not too sure just thinking out loud here

no

[Guest]

 pl0x']

[quote name='VADZTER said:

dont the V8 etc all the same shortblock as the V7? just different heads? not too sure just thinking out loud here

/quote]

no

oh yes now that i think about it LOL V8 got twin scroll larger sump aye and internals any better than V7?