Gtr Half Boost

[dilmah]

Hi all,

Hoping someone can help. I bought a 33 GTR a few weeks ago and it's been great, but I occasionally have this "issue" where the car doesn't seem to pull as hard when on boost.

It's hard to reproduce on demand, but sometimes I have my foot to the floor, but the boost gauge only ready about 4, whereas normally it reads 7.

I can usually fix it by letting go of the accelerator, letting the boost drop below 0psi, and then accelerate hard again and it'll go all the way up to 7psi.

It happens in every gear (usually first or second, as by then I'm already doing over 100, so no need to go any faster).

Stock, except for the following performance mods:

• HKS Priest 3" cat back exhaust
  
• K&N high flow air filter
  
• New turbos (around 4000-5000km old according to the previous owner)
  

I think it may also have an after market blow off valve, as it is pretty loud and has the slightest bit of a flutter to it.

I just had it serviced by RE customs, and they just changed the oils and filter, apparently nothing else needed to be done.

Any ideas what I need to check to get this fixed?

[infamous_t]

Can't help with your problem, but are you reading of the stock triple cluster in the center?

Pressure measurement isn't in psi, it is bar pressure (7 is actually 0.7 bar, or approx 10psi)

[R31Nismoid]

I wouldn't trust the stocker gauges for boost.

They are often all over the place

[dilmah]

aah, ok, so it's read in bar, that's fine, and yes it's the stock pod gauges (torque, oil temp, boost)

but still it definitely feels slow, regardless of what the gauge says.

It's just weird. Sometimes you launch off in first and it goes rather slow, then you shift into second and it pulls harder than it did in first.

It also has nothing to do with how many revs I'm running at the time, it's a constant boost all the way from about 3500 all the way up to 7500 (i don't normally redline it), about a quarter of the time it only boosts up to 0.5 bar, the rest of the time it boosts at the normal 0.7 bar

[rb180]

Can't help with your problem, but are you reading of the stock triple cluster in the center?

Pressure measurement isn't in psi, it is bar pressure (7 is actually 0.7 bar, or approx 10psi)

the 7 measurement on the stock gauge is more like 14-15 psi

Its not in bar pressure. Its actually mmHg which is millimeters of mercury

[tacker]

Do you have atmo BOV? as it might be getting stuck open. Just a thought

[wrxhoon]

the 7 measurement on the stock gauge is more like 14-15 psi

Its not in bar pressure. Its actually mmHg which is millimeters of mercury

This is correct , you will find it may even go higher that 7 but the stock gauge runs out at this point, you may find that someone has removed the restrictor . When your boost only goes to the half mark or just above its because the your ecu turns the boost solinoid off and you have just actuator boost then .

I think you will find the problem is your stock ecu cuts boost to protect your engine because it detects either knock or injectors go to max when boosting. As soon as you turn the engine off it resets itself then boosts to the end again

[dilmah]

Hmm, that doesn't sound very good at all.

Yes, it probably does go past 7, but like you said I've got no idea how far because the gauge doesn't go that far.

The werid thing is that I don't have to turn the engine off and back on for it to start working at full boost again, all I have to do it jump off the loud pedal, wait for boost to drop below zero and then jump back on and it's okay again and I get the kick in the pants I'm after.

So could it be something simpler than this? I sure hope so.

What's the best way to diagnose what the actual problem is?

* Wire up another boost gauge and see what's happening?

* Find a stock GTR bov and put that back in?

* Put the boost restrictor back if it has been removed? (how to tell if it has been removed?)

* get a knock sensor/readout

* upgrade injectors? (shouldn't be necessary as it's pretty much stock car right?)

I'm not very mechanically minded, but willing to learn.

Thanks for all your help so far.

[TTT]

I would..

* get stock gtr bovs back on (there are 2)

* buy an accurate boost gauge (not made by speco or autogage)

* buy an Electronic Boost Controller (some even have a digital boost gauge on them) which you can adjust your boost from stock to what ever you choose.

that should set you back

$150 - stock bovs

$150 - boost gauge

$300 - EBC

-$200 - Sell the current bov

you are out of pocket $400 and you know it's working right.

[dilmah]

Thanks!

I'll start looking into this & see how I go.

I saw a thread about a boost controller for $22 from jaycar or something... I didn't read into it, but I'm guessing that won't do the job here?

[wrxhoon]

Hmm, that doesn't sound very good at all.

Yes, it probably does go past 7, but like you said I've got no idea how far because the gauge doesn't go that far.

The werid thing is that I don't have to turn the engine off and back on for it to start working at full boost again, all I have to do it jump off the loud pedal, wait for boost to drop below zero and then jump back on and it's okay again and I get the kick in the pants I'm after.

So could it be something simpler than this? I sure hope so.

What's the best way to diagnose what the actual problem is?

* Wire up another boost gauge and see what's happening?

* Find a stock GTR bov and put that back in?

* Put the boost restrictor back if it has been removed? (how to tell if it has been removed?)

* get a knock sensor/readout

* upgrade injectors? (shouldn't be necessary as it's pretty much stock car right?)

I'm not very mechanically minded, but willing to learn.

Thanks for all your help so far.

Sometimes they will reset as soon as you back off but usualy you have to turn the ignition off ( from my experiance).

A proper bosst gauge will tell you exacly how much boost you have ( you don't have to wire it up , get a mechanical gauge , they are more accurate too).

Replace your aftermarket BOV with a pair of stockers , are you sure you have aftermarket ? where is it ? If its not inside the drivers side guard you probable don't have the pipe there either.

If you want to run stock boost ( about 11-12 psi) you have to put the restrictor back in , it should be inside one of the hoses to your stock boost solinoid, the one with the 2 yellow lines on it.

If you run stockish boost you are correct you don't need bigger injectors but don't forget you maybe running a lot more than stock and or more ignition timming ( this may cause knock)

Knock or leaning out up high could bust a ringland .... Running high boost on stock turbos could be terminal to your turbos, if a turbo exhaust wheel lets go could spell the end or your engine !!

The above is not meant to scare the crap out of you , just a warning of what could happen, if I was you i would back off until I sort it all out .

[TTT]

You've got 2 boost controllers mixed up there..

the $22 dollar one is now $35 these days.

it is a manual bleed valve

it is made by "turbo Tech"

it will do the job.. but I don't know..

I see it more of a gtst mod.. not a GTR mod..

you have a fancy bit of gear there.. might as well buy something more advance for it.

The Jay Car boost controller is an electronic boost controller.

it is a "DIY" kit that you have to solder together yourself.

it is also a little tricky to tune as it does not bleed of boost, it uses injector duty cycle to work out how much boost to run etc..

it's a little confusing to me.

I have one at home already build but haven't put it on for that reason.

these kits are about $80 from jaycar.

to "tune" it, you will also need the Hand controller (which is another $70)

[infamous_t]

the 7 measurement on the stock gauge is more like 14-15 psi

Its not in bar pressure. Its actually mmHg which is millimeters of mercury

Learn something new everyday, lol.

Now i know...

700 torr(mmHg) or 7 x100 torr(mmHg) = 0.933 bar = 13.5psi

[ashneel]

will come around this weekend and pull my boost gauge out and hook it up to yours and see what the read out is ok dilli boy

[bubba]

Do GTR's have R&R? maybe the "new" turbos aren't standard and you're hitting R&R all the time due to increased flow..

[dilmah]

sweet!! See ya on the weekend ash.

According to the previous owner, the turbos were replaced because the old ones were leaking a little bit of oil so he got them replaced with new stock items. I haven't actually checked them, but he was a pretty genuine guy, and everything else he told me has been true so far, so i have no reason to doubt him.

Also, I'm not 100% sure that they're aftermarket bovs yet, only because i haven't been able to get a look at them, but I'll get in there and have a look this weekend. They may just be dirty or the valve/spring thing inside may be weak.

I sure hope thats all it is.

[mojave15]

Had the same problem on my 32 GTR which seems to have turned out to be the boost solonoid. Swapped that out and she's been boosting 14psi ever since.

Might be worth a try.

[dilmah]

That's good news

I'll let you know how it all goes.

[TrentGTR]

I have the same problem in my R33 GTR!!!!

Except, it happens after a while.

Example:

Ill leave my house at 6pm, drive hard for bout 2 hours, then it feels like one of the turbos is just goin bed!

It totally cuts the boost in half! And i haveto leave the car off for like 20 mins to get it bak up, even then it wont last very long itll cut bak down! ARGHHHH!!!

Boost solanoid sounds like a good tric.

[dilmah]

does anyone know if the boost solenoid in the gtr is the same as the one in a gtst?

How much should i roughly be paying for a stock one from a wreckers, etc.?

i didn't get enough time to check it out last weekend, so the plan is to get into it this weekend:

hook up another boost gauge,

check/replace boost solenoid (with another standard one)

check/replace bovs (with stock ones)

we'll see how that goes first