ST185 (swapped st205) How much boost it takes?

lordvampire

New member
HI,

I swapped engine my st185 to ST205JDM. I am running currently 0,6-0,7BAR. I runs ok. I was planning to install WB lambda gauge to see, how much I can turn boost. BUT, soon comes track day, and I could need all the safe power I can get. I have light modds in engine, metal head casket, new belts and rollers etc.. Timing is in its place. Its working ok right now.

Question: How much boost I can add, before st185 fuel pump is maxed out? Can I go with 1bar?


I know its little bit stupid, not go bythebook, but I have not got the time right now.
I will install the wideband kit to next year. :) I really need top be out there right now.

BR, Andres
 

CMS-GT4

Active member
Should be fine. I never ran a 185 pump in my 205 swap myself. I doubt you would be making over 300hp at those settings.
 

lordvampire

New member
Ok, ok, thanks. I take it easy, and try to be rational. Its Time Attack event so I can cool it meanwhile. Thanks for replay´s.
 

quieter

Member
i pushed my 3rd gen st205 swap at 17.6 psi never hit fuel cut and i never fuel starved with my stock st185 fuel pump
 

aus jd 2703

New member
first off depends if its a gen 3 motor and ecu or gen 3 motor with gen 2 ecu, if its the later gen 2 ecu sucks and I would go over 15psi.

as for all gen 3 gear, I ran 17.8 so right on boost cut for 2-3 years and have noticed slight detonight to #3 plug and a 7psi drop in the cylinder so if I was you 16psi and you safe.
also I run 98 octane in Australia, I believe that's ron and you guys talk mon so I think its your 92 or similar.
 

quieter

Member
yeah 93 AKI is similar to 98RON. in Canada we got 87,89,91 and only 94 at Petro-Canada. its just dumb to put a 2nd gen ECU on a 3rd gen, not the same base maps, injectors are different and MAF vs MAP and plenty other particularities
 

lordvampire

New member
Yes of course, I have matching St205JDM ECU also. Did it with ST185 wiring. We have 98 octane in EU also. Never run lower (95) octane. Ok... I do 15-16BAR then.
 

lordvampire

New member
With wideband air/fuel gauge should see this allthe same. ? or fuel pressure too is needed monitor on its own? So is it possible that Air/fuel is ok, but fuel pressure is not? I know there is third piston melting common. I guess programmable ECU would help. But am I not running 400-500hp. (Eventually I need it :D ) but right now... only little power needed... It has too long gears, that eat power, so everything helps... In short time I do most essential... I make car light as possible, tires, Ferodo pads, axles is over looked, motul 20v60 already in, only question is how much boost.

I know its not right, I was not planning to do any races this year. But, thats life... now I need all the available safe power I can get... 0,9-1bar(13-14,5PSI) some laps. and hope it lasts. Next year I will be prepared and do things by the book.
 

Pipedreams

New member
The wideband won´t tell the hole story. Sure it will lean out a bit but you get poor fuel atomization with too low pressure which will lead to detonation even if the mixture is ok.
 

lordvampire

New member
Ok, I keep in mind. I heard that fuel pump its not the weakest link. Wiring to the pump should be looked over, that if give pump proper wire and via relay operate it it should work better... dodnt know, havent tested, but I guess its not equal to walbro anyway.
 

Pipedreams

New member
Yes, proper wiring makes a big difference. But on a st185 I used to have it wasn't enough to keep up with the demand of a ct20.
 

Pipedreams

New member
I can't remember, it's ~7years ago :) But I don't think I turned the boost until I had a new pump so it was less than 1bar but the pressure dropped at least 0,5bar in high revs so it was barely enough for 0,5bar of boost.
 

lordvampire

New member
I didnt know its so bad! I quess I turn the boost little down and order new fuel pump. : ) I want to keep the engine to wintertime also : )
 
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