EJ20tt custom turbo-back exhaust

[_rsk_]

Heya guys. I am running standard exhaust atm with a axle back 4" muffler (not cannon style).

If I was to make a custom exhaust with flanges - 2.5" from primary with divorced wastegate, "plumbed back" and 3" from secondary turbo merged to a Y pipe, and then 2.5" to the back with a cannon style muffler.

How would this run compared to my standard exhaust? Would boost come on earlier or anything?

Cheers.

[Guest]

It would work awesome. The response would be so much better, probably clear up alot of VOD as well due to allowing the secondary to spool quicker.

Im planning the same but i want a 3inch system. I am only running a Fujitsubo diff back at the moment and when i had it installed, it made the world of difference to the second turbo. I know its only a diff back, but i was really surprised at the top end gain. I previously had an Sti Genome muffler on.

[BLSTIC]

I see no reason to go 3" for the secondary turbo then back to 2.5" as soon as you join the 2.5" primary pipe. Remember the twin turbo system doesn't switch the turbo's (ie the primary never stops, the secondary just cuts in), so if you think about it that way, the primary and secondary dump pipes only have to flow 150kw maximum each (The chances of you going any further than 300kw while still keeping some variant of the twin turbo system is so close to zero)

I was thinking 2.5" from both turbo's to the collector, then 3" from the collector back.

[Carbon]

With 3" youd risk overspool. Theres no reason not to stick with 2.5" for a twin turbo (remembering singles run 3") and then run 2.5 or 3 from the y join

[BLSTIC]

what's this overspool thing you mention? Do you mean spiking or the boost level staying too high all the time?

Both are easily fixed with well placed bypasses (with restrictions) on the boost control plumbing. It would be a little complicated with a twin-turbo system, but more than likely still do-able.

Best off asking someone with experience doing what you plan to do, and see if they actually had problems and what they did to fix them. I haven't done much with the twin turbo's, just theorised about how to fix the valley of death (not actually done it...).

[Guest]

 BLSTIC said:

what's this overspool thing you mention? Do you mean spiking or the boost level staying too high all the time?

Both are easily fixed with well placed bypasses (with restrictions) on the boost control plumbing. It would be a little complicated with a twin-turbo system, but more than likely still do-able.

Best off asking someone with experience doing what you plan to do, and see if they actually had problems and what they did to fix them. I haven't done much with the twin turbo's, just theorised about how to fix the valley of death (not actually done it...).

Over boosting through spikes.

[ReubenH]

Yeah, i have always heard that come up. Everyone's paranoid about blowing turbo's on the twin apparently, but i think BLSTIC is right. External wastegate and a proper TT boost controller and you'd be sweet.

Is there any way to improve the secondary's exhaust valve too? I mean, every time i look at one, all i can think about is how much of a restriction it looks like. Anyone tried improving on that?

[BLSTIC]

well you can have them ported, but there is ony so far you can take it.

If you could find a large external wastegate with an external (like internal wastegates have) actuator you could use that with the original exhaust control valve. If a normal external gate actuator functions the same you can use it, but I doubt it.

[_rsk_]

If I was to vent internal wastegate, would I get the external wastegate sound? ;D ;D

[ReubenH]

 _rsk_ said:

If I was to vent internal wastegate, would I get the external wastegate sound? ;D ;D

The real question is though, why on EARTH would you want to do that!? (thinking more on the difficulty of mod vs benefit of reward here + it being illegal)

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