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Stock Car Running 1 Bar Boost?

hop1308

By hop1308,
in Engines & Forced Induction

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hop1308 Collaborator

hop1308

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Hey guys, I've got a R34 GT-T 98. and i bought it recently. me not knowing much about turbos yet, i bought it trusting the guy and he said the car is completely stock apart from the exhaust which is a 3 inch turbo back.

Yet when i flat foot the pedal at about 5-6 rpm the stock boost gauge shows it reaching almost the top end of it, which is the +1. From what i can see, nothing else is changed it even had the stock airbox which i changed to a pod.

Could someone give me an explanation on what's going on here? I don't see any sort of boost controller or bleed valve either.

Thanks.

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Moodles2 Grand Master

Moodles2

Posted
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I don't know if i've converted it right, but +1 on the stock boost gauge is alittle under 2psi. The line to the factory map sensor (black box on the firewall on the drivers side) has probably cracked and is bleeding air which could explain the low reading.

hop1308 Collaborator

hop1308

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well google says

1 bar = 14.5037738 pounds per square inch

which is really getting me worried because i dont want to be running 14.5psi. im wondering if the guy might have changed the acutator or somethin like that?

RBEE Apprentice

RBEE

Posted
Posted

Years ago when I first got my R33 ser II GTS25T, I picked up a Turbosmart Tee for it, however, one thing that people have to watch is the hose barbs / nipples on the Tee is slightly smaller in diameter so the factory vac line would pop off if not clamped down properly....Long story short, I was on the freeway that night and all of a sudden I was maxing out my boost gauge at 20+ psi and sideways on the freeway in 5th ! The hose from the Tee to the actuator popped off and the wastegate wasn't opening to regulate boost. The motor would've went 'pop' if I had kept at it but I'd learnt two things that night.... One is to use the correct size vac lines, two is what these motors are capable of with a little extra boost - I wasn't too familiar with these car at the time but that incident accidently showed me the hidden power potential in these RB donks.

GTSBoy Grand Master

GTSBoy

Posted
Posted

I don't know if i've converted it right, but +1 on the stock boost gauge is alittle under 2psi. The line to the factory map sensor (black box on the firewall on the drivers side) has probably cracked and is bleeding air which could explain the low reading.

well google says

1 bar = 14.5037738 pounds per square inch

which is really getting me worried because i dont want to be running 14.5psi. im wondering if the guy might have changed the acutator or somethin like that?

The +1 on the stock gauge is in units of kg/cm2. A shitty metric equivalent of psi (not equivalent numerically, just in units of mass per area instead of force per area).

1kg weight at 1 gravity of acceleration is equivalent to 9.807 Newtons of force. 1cm2 is 0.0001m2, so the top marking on that gauge is 98070 N/m2, also known as 98070 Pascals, or 98.07 kPa. That's 14.2 psi.

hop1308 Collaborator

hop1308

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yeah, so its reading about 14.2 psi then from the stock boost gauge. im looking to get an after market one but until then i still wonder whats going on.

what exactly should i be looking for under the hood in regards to controlling boost pressure, and where is the acutator located?

I've still got the dual boost soleniod there with the wires still attached to it, but there are two nossles at the top of the solenoid that look like they should have pipes attached but they dont? or is it supposed to be like that?

GTSBoy Grand Master

GTSBoy

Posted
Posted

The wastegate actuator is a can that is attached to the turbo. Look next to the compressor housing. There is a boost line fitting with hose on the can. That should be connected to a boost line fitting on the compressor outlet (or on the turbo outlet pipe)......but in the case of a stock R34 that hose will go via a solenoid. If it has been fiddled with (other boost controller installed) it is anyone's guess what the plumbing will look like.

hop1308 Collaborator

hop1308

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well my boost gauge reads +1 Bar and i cant see a boost controller or anything like that in my car. The solenoid is still there but has no pipes attached to it.. wonder whats going on :s

anyone have any ideas?

NISMOGTT Collaborator

NISMOGTT

Posted
Posted

it sounds like my car was when i got it from Japan years ago.

the boost control solinoid was not connected and i found that i actually had an Impul ECU which supported the higher boost level.

check where the vacume hose from the waste gate goes, if not to a solinoid then it will be straight to engine like mine was, if this is the case then check the ECU also as if it is a stock ECU you could end up doing damage...

GTSBoy Grand Master

GTSBoy

Posted
Posted

With no boost control solenoid connected, no ECU can control the boost. The boost can only do one of two things. Those are 1) run at wastegate pressure if the hose is connected direct to the actuator, or 2) run totally uncontrolled if the hose is somehow disconnected. The Impul ECU had nothing to do with it.

GTSBoy Grand Master

GTSBoy

Posted
Posted

Look at the first image in your post. Straight down from the boost control solenoid and slightly closer to the motor is the compressor housing, and attached to that is the wastegate actuator. The actuator is the cad plated (gold coloured) can. Look on the photo posted by 34GTT above. Red circled region. That's the turbo. The can is clearly visible and you can see the little connection where the boost hose needs to be connected. You need to see that on your car there is a hose on there and that it is connected meaningfully to something else. The bare minimum should be for it to run to another connection either on the compressor outlet (about 3 inches away, max) or somewhere on the compressor outlet pipe (the ~2" one off the turbo housing that then runs to the front of the car and down to the intercooler). If the hose runs somewhere else, you need to find out where, what and why. If there is no hose at all, that will explain why your boost is too high, although it doesn't explain why it is not 20+ psi, because no boost control at all should give you enough boost to blow the thing to smithereens.

hop1308 Collaborator

hop1308

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do i need to disassemble to see this or will it be visable from the engine how it is, these jap engines are so big and crammed into such little space lol.

thanks heaps for the help though guys, especially gtsboy, i dont wanna lose anymore sleep wondering whats going on :P

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