Rb26 - Noob Question Regarding Boost

[UNR33L]

Hi guys,

Just a quick question I'm sure:

Basically I've owned my R33 GTR for about 2 months now, I put some apexi pods filters on it and just has a cat back exhaust at the moment otherwise completely stock.

Now my boost gauge use to say -11 ish on idle and boost up to abou 10 PSI, (on both my mechanical boost gauge and stock gauge), and now after a oil change (duno if it could be related at all) sits at about -2 ish on the gauges and only found that its boosting up to about 6-7 PSI? and car just seems a little slower in general..

Now I'm no engine guru but my first thought was maybe there is a leak somewhere in my FMIC piping? but figure I'd just ask here to see if this has happened to anyone else.. sorry if its been answered before but couldn't find anything.

Thanks in advanced,

Leigh

[Beer Baron]

yep, most likely a pipe blown off, or vacuum hose off. best bit if you are not sure what to look for is take it to a mechanic and get them to find the missing/split/blown pipe. easy fix.

[UNR33L]

Ah ok no worries, it must be only small / hard to find if its still getting some boost I guess? I was going to get some parts and a tune by Status so I assume Trent should be able to find it if I cant haha

edit: is there any common places to look?

[StealthX]

Ah ok no worries, it must be only small / hard to find if its still getting some boost I guess? I was going to get some parts and a tune by Status so I assume Trent should be able to find it if I cant haha

edit: is there any common places to look?

Does your car have a front mount?

If so, the turbo > first hot pipe, is a common one on aftermarket kits. So is throttle body and first of the cold pipes.

Are you blowing any black smoke and is it idling rough?

[UNR33L]

Its just got the stock front mount

I will check pipes when I have a chance

It doesn't seem like its blowing to much black smoke if any, the rear of my car gets a little black but seems fairly normal black-ness to be honest.

It seems to idle a little rough sometimes but not at all times, and also seems after I turn the car off for say 5 minutes (get petrol or what ever) get back in and drive off it has trouble when it hits boost seems to missfire a bit? or at least seems like that and also will idle rough at this stage as well.

[DVS JEZ]

check out all the little black rubber hoses near the oil filter, get a good light down there and you might find a hose off, did you use a ratchet or oil filter removal tool?

[UNR33L]

Used a oil filter removal chain, and then replaced filter with a socket type filter 'Drift' brand.

The only thing I saw near the filter was something going to the front diff? a wire or something from memory

[DVS JEZ]

under the inlet manifold there is a vineyard of black vacuum hoses. have a really good look, even use a mirror, its to coincidental that you changed the oil then this happened,

the reason i asked it you used a tool is this would make more sense if you pulled a hose off

[UNR33L]

ah ok so check under the intake / throttle body? yeh sounds like that could be it as I did just change the oil, will update once I have a look at everything.

[Beer Baron]

yeah trent will be able to find it no problem in 10 mins or so. he would have fixed literally hundreds of skylines with the exact problem you describe.

[lachlanw]

lol @"does your car have a frontmount"

nah i took it off coz i didnt wanna be a boy racer

[UNR33L]

Yeah i'll try and have a look when i can.. if not fixed I'm sure Trent will have no problems he would be 100x better with this sort of thing then myself I'm more of a I.T guru rather then engine troubleshooting..

And yes! GTR has FMIC!

Happy that its nothing serious

[GTRNUR]

The map sensor for your gauge is located on the drivers side of the engine bay near your brake booster. There is a hose that goes from that to the back of the plenum near the firewall. The rubber tends to go hard, split/crack or just break off the brass pipe fitting that is on the back of the plenum.

You can easily reach it to check the hose. Give the hose a wiggle and squeese where it attached to the plenum. If its hard and cracked it will probably break off completely. Replacing the hose and doing a complete pressure test to identify other failing hoses is your best bet.

[UNR33L]

Well I feel like a idiot for not seeing this while changing the oil but here was the problem (simple boost gauge T-Piece rubber tube has busted):

Thanks for the help and advice people gauge went from -2 ish to -20, and boosted 10psi plus now instead of dropping at like 6-7 psi and just not running well in general.

[DVS JEZ]

good to hear its fixed,

[UNR33L]

haha thanks figured i'd post a photo up purely incase someone else comes across the same thing

now to move on to finding some new turbos!

[ZILLR]

really nice GTR, seen it around a while back