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factory boost on jap spec R

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200WEI

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hi every 1 :) this might be a bit old news for you guys but yeh i aint jus very sure bout this whole stock boost on s15. i know aus spec 200sx s15 all run 0.5bar, but i heard jap spec turbo s15 run 0.9bar, hence that they are more powerful. n i jus recently bought a jdm s15 n it runs 0.5bar and its stock so plz help me here thanx!!!
 

Yakozan

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I think stock boost is somewhere around .7 bar. If your JDM S15 only boost .5 bar you probobly got a boost leak somewhere. The most likely source of leak is the hose teed off the top recirc valve hose to the stock boost gauge unit located on the drivers side strut tower. remove that hose and check if it's broken. can be pretty hard to see sometimes, but if you completely remove it and look at it you should be able to tell if it has split or not at the ends.

Very common problem on the JDM S15s. very easy and cheap to repair though.
 
S

Scotty

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Factory boost on my spec r is 0.5 peaking to 0.6

check your boost control solenoid/the restrictors in the lines, if you have removed a wrong restrictor it will drop boost instead of increase it.
 
2

200WEI

Guest
I think stock boost is somewhere around .7 bar. If your JDM S15 only boost .5 bar you probobly got a boost leak somewhere. The most likely source of leak is the hose teed off the top recirc valve hose to the stock boost gauge unit located on the drivers side strut tower. remove that hose and check if it's broken. can be pretty hard to see sometimes, but if you completely remove it and look at it you should be able to tell if it has split or not at the ends.

Very common problem on the JDM S15s. very easy and cheap to repair though.

thx for the suggestion. ill have a look at it. but thing thing is ive seen afew other jdm s15 with 0.5 bar stock boost + mine runs right at 0.5 constantly so i thought it might of been dropped down for compliance or something?
 
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200WEI

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Factory boost on my spec r is 0.5 peaking to 0.6

check your boost control solenoid/the restrictors in the lines, if you have removed a wrong restrictor it will drop boost instead of increase it.
thx for the reply, and wheres the restrictor located??
 
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I thought standard boost was 0.5 bar in first and second then 0.7 bar in the rest of the gears?

I'm pretty sure thats correct but i'm sure somone will confirm...
 
S

Scotty

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Look on your boost lines you will see all the black hosing And the solenoid, remove the resrictors in the solenoid line. Beware you will be boosting 0.8 bar peaking to 1 bar. If you have no restrictors then get an hks adjst actuator !
 
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200WEI

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Look on your boost lines you will see all the black hosing And the solenoid, remove the resrictors in the solenoid line. Beware you will be boosting 0.8 bar peaking to 1 bar. If you have no restrictors then get an hks adjst actuator !

ar thx man ill have a look, tho im still unsure bout where the boost line is so if u can explain it to me a bit mroe in detail dat would be very nice thx man :)
 
J

jonny b

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i had this problem about 2 weeks ago and,like yakozan said,the problem is generally your boost line going to your gauge,check the boost line running from beside the drivers coilover yo the front of the engine bay and youll prob find its split or leaking at the the t-piece..
 
S

Scotty

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Check the gauge, i'm going to check mine too, but the boost line, on a factory setup, is on the right hand side of the engine, (looking at the bay) and is on the cold side of the i/c piping, little nipple going from the piping to the turbo, and splitting for the solenoid.
 

DeanS15

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as standard my car only boosted to 0.5 or 0.6 bar, only when i fitted a turbo back exhaust and filter did the boost jump up to 0.9 bar. is it possible the jap spec one you went in had a decat exhaust and filter?
 
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200WEI

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as standard my car only boosted to 0.5 or 0.6 bar, only when i fitted a turbo back exhaust and filter did the boost jump up to 0.9 bar. is it possible the jap spec one you went in had a decat exhaust and filter?
yeh mine runs right at 0.5bar constantly, so i DONT think it is a prob and i asked my other 2 m8s who also own jap spec, theirs also ran 0.5bar when stock. mine had apexi cat back exhuast n the rest of the car is dead stock.
 

DeanS15

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i also replaced all the boost hoses before they could split, so may well of removed the said restrictor, but id say as long as its not showing less than .5bar stock then its aok.....
 

DeanS15

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huge reduction in back pressure against the turbo - on na you need backpressure for it to work well and for a bit more torque, on turbo the less restrictive the exhaust gas flow is the better. the standard exhaust and its downpipe, especially the turbo elbow are very restrictive. in fact the stock elbow seems designed in such a way to interrupt the gas flow as it exits the turbo as one side juts out into the exhaust gas path.

this isnt the most technical of answers and im sure someone can tell you the effect this all has on the wastegate to allow more boost to be produced naturally.:)
 
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200WEI

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thx for all the replies guy! byw i jus installed genuine apexi intake kit n somehow it managed to push the boost upto 0.7 from factory 0.5. so now im asking you guy is it normal or has it happened to any of ur cars when u jus installed a pod filter on stock s15?
 
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200WEI

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yeh i know, 1 of my other s15 m8 had turbo back n his ran 16psi. but i so unexpected my boost to go up jus with pod filter tho
 

DeanS15

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you have removed a restriction, thats probably why. if you keep modding without some form of boost control it will probably continue to rise
 
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200WEI

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yeh i got greddy profec B boost controller at home in box lol jus bought it yesterday with the intake. i will install the boost controller this week then set the boost at 12psi
 
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