Boost Spike Question regarding aftermarket downpipes

[uwantsumbeef]

Hi all, im looking at buying this for my 2003 SG5 Forester http://www.trademe.co.nz/Trade-Me-Motors/Car-parts-accessories/Subaru/Other/auction-346693173.htm

A friend of mine told me to be cautious of boost spiking as earlier model evos and subarus were prone to it with aftermarket downpipes.

anyone every had any problems along these lines?

thanks

[kamineko]

yep, early v2 sti with a td05 can spike and boostcut pretty badly with a large downpipe/exhaust. i think the smaller turbos should be ok, and the newer models have a higher boostcut threshold. giving it the berries on a cold night a v3 might hit limpmode but they don`'t seem to cut as badly a the v1/v2

i have no firsthand experience with the newer models though

[Guest S T E Y E]

best way to get the full out of your 3 inch downpipe to not boost spike / hit the cut (my old v2 use to cut like a beast) is to either a. port the internal wastegate OR run an external wastegate...on my old v2 i switched to an external and all was fine

[Guest]

external wastegates are good for holding boost unlike internals lol

[Koom]

Internals do a pretty decent job but you may need an aftermarket controller and/or port the wastegate hole as mentioned. They only start to spike with a bigger downpipe as the factory controller isn't configured to that setup. It's the electrickery that's half the problem, not just the fact that its still using the internal.

[Guest S T E Y E]

yea as for internals go tho the best way to have it is with a EBC and ported as far as u can take it.....

[QIK_KAS]

the internal wg is fine. you just require a well set up EBC.

-whopps, kamineko

[Guest S T E Y E]

yea but if u run a ebc and boost is still not good enough... you port the wastegate...

is all im saying

[Guest]

haha if your going to all that trouble you may aswell geta externL and plum it back

[Guest S T E Y E]

plumb it back?? why??? ohh yes to be legal haha

[Guest]

haha yeh bro iwas just sayin it for all the legills on here ;)

[Koom]

 S T E Y E said:

yea but if u run a ebc and boost is still not good enough... you port the wastegate...

is all im saying

Why? So you can run 22psi on a vf23?

[Guest S T E Y E]

lol

its the theory yes?? i havent come across this situation on a suby (cos i dont run a internal)

my RB30 originally had a internal...and on just 1 bar with a turbonetics t70 hybrid the internal was all over the show...ported the fuck out of it...was better but not great...got an external and it was mint!! got a re tune and alot more power

[Koom]

Yeah but a Turbonetics T70 is a much different beast to the factory turbos that most people with Subaru's seem to run. And the factory Subaru turbo's don't work well above 20psi (usually peak around 17-18psi from what I've seen) which the internal controls pretty well in most cases. External's are great when you go to a bigger turbo and want to push some big numbers but in general (and I'm talking about the ~200kw crowd here) an external is either a) overkill or b) just for noisy wank factor.

[Guest S T E Y E]

 Koom said:

Yeah but a Turbonetics T70 is a much different beast to the factory turbos that most people with Subaru's seem to run. And the factory Subaru turbo's don't work well above 20psi (usually peak around 17-18psi from what I've seen) which the internal controls pretty well in most cases. External's are great when you go to a bigger turbo and want to push some big numbers but in general (and I'm talking about the ~200kw crowd here) an external is either a) overkill or b) just for noisy wank factor.

LOL...

all though it is proven a open to atmosphere wastegate is better performance than a plumbed in wastegate..less back pressure for wastegate gases to exit and less turbulence in exhaust

[subieboy]

 Koom said:

Yeah but a Turbonetics T70 is a much different beast to the factory turbos that most people with Subaru's seem to run. And the factory Subaru turbo's don't work well above 20psi (usually peak around 17-18psi from what I've seen) which the internal controls pretty well in most cases. External's are great when you go to a bigger turbo and want to push some big numbers but in general (and I'm talking about the ~200kw crowd here) an external is either a) overkill or b) just for noisy wank factor.

Agreed

Unless you are 200KW@wheels or more its of no use other than wank factor (or on a factory standard car)

[kamineko]

 S T E Y E']

[quote name='Koom said:

Yeah but a Turbonetics T70 is a much different beast to the factory turbos that most people with Subaru's seem to run. And the factory Subaru turbo's don't work well above 20psi (usually peak around 17-18psi from what I've seen) which the internal controls pretty well in most cases. External's are great when you go to a bigger turbo and want to push some big numbers but in general (and I'm talking about the ~200kw crowd here) b]an external is either a) overkill or b) just for noisy wank factor[/b].

LOL...

all though it is proven a open to atmosphere wastegate is better performance than a plumbed in wastegate..less back pressure for wastegate gases to exit and less turbulence in exhaust

sure, but thats akin to saying there are performance gains in removing your exhaust altogether. its not really a fair comparison is it

[Pappu1]

yo bro it wont spike dont have to change anything else like wastegates and the likes..

initially it will have a spike or 2 but settle to a pound or so within factory boost and give u no trouble but just a whole better turbi rush

the new gen ecu can conteol boost a fair bit better then the older ones so in summary - get the pipe and dont wirry abt the spike etc as the ecu will sort the biist very nicely

PS done that a few times in few new gen turbos and they were all very good

[uwantsumbeef]

 pappu said:

yo bro it wont spike dont have to change anything else like wastegates and the likes..

initially it will have a spike or 2 but settle to a pound or so within factory boost and give u no trouble but just a whole better turbi rush

the new gen ecu can conteol boost a fair bit better then the older ones so in summary - get the pipe and dont wirry abt the spike etc as the ecu will sort the biist very nicely

PS done that a few times in few new gen turbos and they were all very good

cheers bro, thanks for an answer. iv got my ecu-remapped with ecu-tek and will look at getting it redone once i get a few more mods.

problem with this forum, people get off topic pretty fast and in the end generally know one really knows

[Guest]

I was speaking to Steve Murch a while back and he does not recomend you port the wastegate of a vf turbo.

When you start to push these turbos backpressure forces the wastegate open and you can't hold boost. Porting the wastegate just makes it worse.

[Guest]

i tried installing a boost tap in my car today,i still run the factory internal gate. the tap was crap and wasnt ever accurte.1st gear 14psi 2nd almost 20 3rd gear mean spiking to 20psi and dropping back.also felt like it was slow bringing on boost.i wana invest in a good ebc that is the same psi every gear

[Guest S T E Y E]

yeap cheap taps are.......cheap

[Pappu1]

It's a pot lick with cheap taps I have seen some control boost well and others very badly. Guess that's the most consistent factor of cheap taps thy they are unreliable on what sorta performance they will give. O has anyone here used a gfb atomic tap. There website talks sooooo highly of them bu I don't know anyone who has used it for real

[Guest]

 pappu said:

It's a pot lick with cheap taps I have seen some control boost well and others very badly. Guess that's the most consistent factor of cheap taps thy they are unreliable on what sorta performance they will give. O has anyone here used a gfb atomic tap. There website talks sooooo highly of them bu I don't know anyone who has used it for real

yeh this tap i got free prty much .was shit az thoe.cheap is what yu get lol.yeh i had a read up about the atomic taps,bring boost on early(quicker spool) and hold boost for longer,seems like a good tap.iv known a few people running these(not on a Subaru) and they aparntly do all the shit they say they shuld do on the website lol

[WRXER]

Get a decent EBC, problem solved. Unsure why recommend an external for these kind of setups when not needed as Koom said, plus you don't need to worry about replacing up-pipes/welding/legality issues etc etc so IMO less hassle. Also I discount the oppinion it leaves options open later on, 99% of people I hear that from will never go down the large turbo route once costs are added up and if you do it an extra few hundred bucks shouldn't be a major to get it done.

I solved the boost problem on my previous v2 with a boost tap when I changed my downpipe to a 2.5". Fixed the boost spike issue however like mentioned before not very accurate, once setup though they do the trick though and I wasn't ever running high boost (was happy on 12psi and allowed to an extra psi of creep so boost spike/boostcut was never an issue).