Boost Maxes Out At 9psi

[diamondjo]

So I installed a Turbosmart Boost Tee today along with a boost gauge and according to the gauge I always max out around 9psi and this is the weird part: even with the stock solenoid. The Tee (according to the gauge) makes absolutely no difference - even wound out all the way! Something is very wrong wrong here.

I always ran 12psi on my previous Skyline with a Turbotech controller and really didn't have any problems getting to this pressure.

The only real difference between the old and new cars is that my current one is more heavily modified that my old one (3" turbo back, hiflo cat, fmic, pod, bov versus just the pod on my old one).

Does the fact that the engine breathes easier somehow mean I can't make as much boost? Or perhaps there's something wrong with my gauge. The gauge is responsive and smooth, but I'm not sure I trust it.

Anyone have any ideas?

[diamondjo]

I guess my biggest concern is, I have absolutely no idea what pressure I'm actually running.

[diamondjo]

Sleep on it, they say, and the answer will come. Now I'm not a mechanic, this only comes from thinking about the physics of the problem - please someone who knows what they're talking about put me right if this isn't the case. Now I know this is modding 101, but please bear with me because this is my first foray into proper mods.

The FMIC and all that extra piping has (for argument's sake only) doubled the volume that needs to be filled with air before the intake plenum. This means that it takes twice as much air to reach the same pressure as it once did and the turbo has to work twice as hard to get there. There's probably nothing wrong with my gauge, tee or anything else, I'm simply getting to the limit of what my little snail can puff.

Is this the case? And if so, if it was considered "safe" to run my virtually stock skyline at 12psi, I'm assuming I've got to wind this figure down somewhat for the modded one?

[Pal]

cooler piping and FMIC will not make much difference to your boost, and if it does it will increase . take the bleed valve out and plumb straight from the intake pipe to the actuator, should be under 9psi with that. that will test your gauges to see if they are ok. make sure you are winding the screw the right direction, i think it has to be wound in to increase boost

[bubba]

You are using an aftermarket boost gauge yes?

[diamondjo]

You are using an aftermarket boost gauge yes?

Yeah an aftermarket gauge. Can't remember the brand name but it's from Supercheap. Can't afford an electronic controller yet - having just bought the new car and getting some mods so I needed a gauge (any gauge) quick smart. I wouldn't have expected the gauge to be more than a fraction of a PSI out regardless of the cost - but I'm really wondering whether or not to trust it. As I mentioned though, the readings are smooth and consistent - it's not like it wiggles up to the line or anything.

It's hooked into the pressure line to the stock gauge via a T-Piece.

To be honest, the car "feels" faster when I unwind the tap - but you know how reliable feelings are when measuring power increase

What bothers me is that even with the tap FULLY unwound, it makes no difference to pressure. Tonight I'll try winding it all the way in to see if the readings come out lower - as they should.

[diamondjo]

cooler piping and FMIC will not make much difference to your boost, and if it does it will increase . take the bleed valve out and plumb straight from the intake pipe to the actuator, should be under 9psi with that. that will test your gauges to see if they are ok. make sure you are winding the screw the right direction, i think it has to be wound in to increase boost

I'm pretty sure I followed everything correctly, with the arrow pointing towards the turbo-housing (and hence the wastegate actuator) and I was turning the tap in the direction of "Boost+". I can't help but think I've done something wrong though as (apart from the very occasional hunting at idle) everything else about the engine in terms of smoothness and response seem fine.

Edit: I think the idle problem is the AFM. It only happens when cold and only very occassionally. A light tap of the throttle always sorts it out.

Edited April 21, 2010 by diamondjo

[diamondjo]

Okay, this is weird... tightening the controller right up has no effect either! Tomorrow I will try reversing it in case I have it backwards, but I'm almost certain I don't! Also, checking under the bonnet, things look a bit different to my last skyline. For one thing, I can actually see the waste gate actuator and it almost looks as if the hose from the solonoid comes from a T-piece on the main line goes somewhere else entirely. It was getting dark when I did this, so I couldn't see exactly what was going on, but I'll draw a diagram:

It was also hard to see exactly where everything went because of the rubber conduit. I'll take some actual pics tomorrow and try to find out where everything goes.

[HoWiE_Au]

Hi there mate yeah mine was maxing out at 9 too awhile ago it didnt matter how i installed it , Then i had it trying to boost to infinity or untill the turbo shit itself. Remove it and ground out the the boost solenoid wire im on about 10psi or so now and my stock turbo is happy ( lol for awhile anyway ) give it a crack you can only stuff it .

[RBceffy25]

Ok mate read the following carefully and study it.

As far as I understand one line/hose must go from actuator to tee and the other line/hose from either compressor housing of turbo or turbo outlet pipe (the pipe that goes between the turbo and intercooler). As far as I remember (and I have installed about 4 different makes and brands of boost controllers) it must be before it goes through the intercooler as a minor pressure drop will occur through the intercooler giving inaccurate boost and false readings.

Also you I think you have leave the factory boost solenoid connected or your ecu/AFM wont like it which could be why it wont allow you to make more boost due to the AFM not seeing correct boost levels in correspondence to what the ecu thinks it should be seeing from the standard boost solenoid. I know it sound like a contradiction but trust me it actually makes sense because when you install an aftermarket boost controller it runs independently without being directly linked to the ecu, AFM etc.... leave it plugged in to the loom but cap off the ports.

By the way save your money and get an electronic boost gauge with its own solenoid etc as I have also used various cheap mechanical boost gauges and they are too inaccurate for a conclusive boost reading. I even went through 2 identical 'Speco'(supercheap) gauges on my own car and both read differently running on an identical engine/car setup (I assume this is what you are using).

By the way your idle issue is your IAC valve. Here is the link you want http://www.skylinesaustralia.com/forums/Di...0&start=160. It’s easy as and it works.

While you’re at it though I recommend you also remove you AFM and pod and clean your pod and get a can of CRC MAF/AFM cleaner. It also works nicely.

I hope all this helps you in some way.

[RBceffy25]

This link shows just as i have explained.

www.turbosmartonline.com/index.php?id=108

[HoWiE_Au]

Nice write up ceffy, Do you know much about stalling after the Bov kicks in?, It feels like it gulps in a shitload of air and it doesnt like it.

[RBceffy25]

This link shows just as i have explained.

www.turbosmartonline.com/index.php?id=108

My bad.

This is the one you want:

http://docs.google.com/viewer?a=v&q=ca...R5AvGD9-hF29boA

[RBceffy25]

Nice write up ceffy, Do you know much about stalling after the Bov kicks in?, It feels like it gulps in a shitload of air and it doesnt like it.

Thanks mate, much appreciated.

Ok firstly, I assume what your saying is that when you make boost or start making boost and then back off the throttle (which initiates the BOV because the boost needs somewhere to go when the butterfly in the throttle body slams shut) your engine is stalling. Is this correct? (i'll explain more on this later)

Also please explain what you mean by "It feels like it gulps in a shitload of air and it doesn’t like it"

Next question.

What type of BOV are you using? Is it the standard unmodified plumb-back unit or have you swapped it for an aftermarket item?

And if its aftermarket, is it venting to atmosphere or still plumb-back?

Depending on your answer, it may have something to do with what i started to explain in the brackets in the first paragraph.