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downpipe and boost SPIKE

7K views 29 replies 16 participants last post by  xreidpolarx 
#1 ·
Just put on a dp and when i am wot going into 5th the boost spike dam near 18 psi makes the fuel cut go on Whats next boost control. or save for utec
 
#12 ·
wow....

common knowledge ftl. sorry but theres about 2189426398476 posts about EM and boost spike.

yes the spike is extremely dangerous. without tuning you can be running 12.0+ afrs in full boost. thats bad.
 
#14 ·
Boost spikes yeah they might be bad, but they really shouded me some good power when it spiked to 15to about 15.5. Well an 05 sti was starting to pull ahead of me when my car boot spike AND I WAS ROLLING, bye bye sti pull at least 1.5 cars ahead of him with my big as smile lol.
 
#23 ·
at what psi does the ecu cut fuel? with after market EM will you car still cut fuel?
ie. if im hitting 10psi stock and maybe the car peaks at 11/11.5 and then i get EM and a custom tune for 17psi will it still cut my fuel at like 18psi? boost usually stays in one general area but every now and then it will jump + or - like 2psi. that would suck if you tune was so close to the stock cut off that every time you hit WOT your car cut off on you
 
#25 ·
Good Posting Dum Dum And Kjot21. Exhaust No Em Is Not Efficient, But Can Be Run, Not Recomended Though. And All These People Have Been Talkin About 18 Psi On Their Stock Wrx Turbo How Why What!!!!!!! Thats Not Right Even If You Are "tuned" Thats Out Of Its Efficiency Range.
 
#30 ·
I've heard of this happening a lot with the EJ25 and although a reflash or stand-alone is the best way to go, there is a poor man's fix...allegedly. Bore out your wastegate passage. I don't know anyone who's tried it, but jscspeed.com says it works:

"04-06 STi OWNERS READ: On the 04-06 STi there are boost spike or creep issues in all cases with the use of an aftermarket downpipe or turboback that uses a bellmouth or external dump tube design. This is because the 2.5L engine pushes so much air. Even with the internal wastegate fully open not enough air can exit to stop spinning the turbo, the result is boost creep or boost spike. You can fix the problem by porting the stock turbo's wastegate passage (any exhaust shop should be able to do this or it can be done at home) or you can get an engine management system to fix the issue, like a UTEC or AccessPORT."

Hope this helps.
 
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