Catted and Divorced Downpipe Options for an '04 WRX (EJ205)

[LaszloT]

Is it necessary to optimize the dowinpipe (DP) if I'm planning on running COBB AP off the shelf maps? If so, I like the Q300 exhaust and the engineering in both of these downpipes:

Invidia Catted Divorced Downpipe - 2002-2007 Subaru WRX



Invidia 02-07 WRX/STI Q300 STAINLESS STEEL ROLLED TIP CAT-BACK

[JoeT]

If you add anything to the car, like that downpipe, or intake, you're beyond the realm of "off the shelf" maps. You'll need to invest in a tune that's specific to your mods.

[LaszloT]

Thanks JoeT, I appreciate it.

I like the independence and flexibility of using the COBB OTS maps to start. So does this mean that I have to source a tubo-back exhaust that is designed to work with the Stage 2 OTS maps instead?

[JoeT]

Thanks JoeT, I appreciate it.

I like the independence and flexibility of using the COBB OTS maps to start. So does this mean that I have to source a tubo-back exhaust that is designed to work with the Stage 2 OTS maps instead?

YUP.. They have a list on their site on what you can use with their maps. But it's always a good idea to get tuned specifically to your mods. No 2 cars are exactly the same.

[STeveD]

If you're buying downpipes or catbacks piece-meal, there tend to be more fitment issues, and they also tend to taper down to a stock diameter flange since they're designed to work with the other half of the exhaust being stock. If you are going to order these, make sure they're 3" straight through and don't taper at the flanges if you want to maximize power. Mind you, the Cat will do more to restrict flow than the 2.5" taper, but you did talk about "optimizing". Even some TBE kits taper down at the flanges. Ask about this and shop wisely!

Really for your power goals, a taper isn't going to be a big problem. But goals tend to creep over time.

[LaszloT]

Ok I'll get the exhaust pieces as a set and I'll confirm that the one I pick is compatible with their OTS maps. I suspect this Invidia item is, but will check.

[BryceD]

AFAIK all Invidia WRX / STi exhausts are 3" flat flanges, no OEM donuts.

[LaszloT]

Thanks BryceD.

Stage 2 power, here I come.

[JoeT]

Spun bearings here we come... LOL Welcome to the obsession.

[LaszloT]

Ye of no faith, JoeT. I have the secret weapon - Rotella T 15W-40

[dubya_rx]

Not T6?

[JoeT]

Heed these words, I know for a fact you have not modded your oil pan. With great power comes greater expenses.. That comment has nothing to do with the quality of oil, and the barrel in comes in.

Turn 3 at Mosport is waiting for you.

[LaszloT]

JoeT you are scaring me.
I thought Stage 2 was modest power. And yes, stock oiling system.

I got it today and might get it installed Friday, if all goes well. An Invidia Q300 and a catted/divorced downpipe. See updated images above.

Yippee!

[JoeT]

Laszlo, when we first discussed your goals, you indicated you wanted stock "ish" hp, that's why we recommended the route you're taking. Your goals have changed, modest power out of a 2L engine that's open deck, and barrels that walk during high boost and high rpm's, couple that with no oiling mods = tick tick tick... Just letting you know what you're in for, and not to be surprised when it does occur.

Turn 3 taken at greater than 5500 rpm can empty your oil pan in less than 8 seconds flat, most of that getting ingested through the intake through the PCV recirc. Next time you take off your intercooler, look at the nice oily film in there then ask yourself where did it come from. Then note, that the oil film in there was from street driving, now imagine the amount of oil that will go through there when on the race track. A side effect of oil being ingested is the "0" AKI index that it contains. Doesn't matter what gas you use, if there's motor oil in that mix, you can expect your bearings to get hammered like crazy through knock.

Remember, the farther from stock you go, the more care and feeding your engine will need, and the more careful you'll need to be.

[LaszloT]

I'm listening, JoeT.

What do you suggest with Stage 2 power then - is it oiling mods? I have a spare oil pan that came with the spare shortblock that we could have the toilet seat mod fitted to it and then switched with the one in the car.

That sounds like a task for when the EJ205 is rebuilt though.

Keep it under 5500 rpm in Mosport MIR turn 3..?

[BryceD]

Sticky tires and GP track absolutely need a oil pan baffle at minimum.

[LaszloT]

Bryce,
Was I taking a risk running my stock '09 STi on the big track at Mosport then, or has it better oil management features in the pan than my '04 WRX?

[JoeT]

Bryce,
Was I taking a risk running my stock '09 STi on the big track at Mosport then, or has it better oil management features in the pan than my '04 WRX?

Yes you were. The STI has better baffles in the oil tank than the WRX, back in your year. The WRX has a single baffle the STI had 3 layers in 2 directions, back then. But if you threw V710's or R6's on your car and drove it at Mosport, yes, it would have eventually grenaded. The other operative word you used was "Stock". The farther from STOCK you go, the greater the risk of failure.

[LaszloT]

Interesting.
JoeT, have you a sketch of the oil pan toilet seat mod you mentioned, and is that enough for my '04 WRX with Stage 2 power and street tires?

[Cavemanrjc]

Well, its 715am and I'm headed to the shop to install all these shiny parts.

Thank you all for the input on the tune.

See, its not just me saying it. But as there is a second block being prepared what's the worst that can happen? ;-) have a good day all, ill post picks later.