Fitted a boost sensor/guage and getting much lower boost then expected :(

[Anees]

Hi guys,

 

Recently I have started the process of getting myself to the holy grail that is BPU. I bought a HKS Boost sensor and connected it into the vacuum pipe on that goes into the Toyota Turbo pressure sensor.

 

I cut the vacuum pipe, put in a T and ran some 3mm rubber vacuum hosing to my sensor.

 

Trouble is the MAX boost I hit was a measily 4.2psi! I thought something can not be right, so I thought the hose might be kinked or leaky (it was quite tight), so I replaced the old hose with a new hose and used longer hoses so everything wasn't so tight. Went for a blast and came back having hit 4.3psi!

 

My car is stock yet apart from a 1st decat but I should be hitting much more then that.

 

The car actually drives well and pulls smoothly and strongly so I am at a loss as to why I can only peak at 4.3psi.

 

This pic hopefully explains better:

 

http://www.ranatech.co.uk/aristo/boostsensorinstall.jpg

 

I know the location I have tapped into is the best one to use since it goes into the same pipe the Toyota Boost sensor uses. My car was up at Charlesworth Motors a few weeks back (work on alot of Toyota/Lexus cars especially Aristos) and when they drove it they said it drove well considering the stock level of tune. Surely if I was really hitting 4.3psi the car would hardly move, but if I am to believe the HKS electronic boost sensor I must be? LOL

 

When I first start the car the guage is in the minus (around -11psi). Is this normal (never had a boost guage before!)?

 

What can I try? Could I have a leak?

 

Any help appreciated.

 

Thanks,

Anees

[merckx]

What pressure does the gauge show when you have the ignition on before you start it up?

 

4.2 psi is low, 0.3 bar. You should be getting almost 0.8 bar max if the Aristo is the same as the

Supra.

 

 

It is normal to have a negative pressure or partial vaccuum when you start the car up as the engine is sucking air in from the intake manifold, I'm not sure what the the average pressure should be . When the turbo's are forcing air into the intake manifold you'll have a positive pressure.

Edited November 16, 2008 by merckx (see edit history)

[Anees]

You are correct, should be 0.7bar on first turbo and 0.8bar when the second turbo kicks in.

Engine stuff is exactly the same between the two cars (except I have VVTi like on some of the later Supras)

 

When I start the car it is at around -11 psi. Would you agree I have taped into the best location? I mean if its a good enough location for Toyota it should be good enough for me.

[merckx]

When I start the car it is at around -11 psi.

What pressure do you get when the ignition is on but the engine isn't running?

 

 

Would you agree I have taped into the best location?

I tapped into the turbo pressure sensor tubing on mine, it's difficult to tell from the picture, as long as you've fitted the T piece in the hose that goes to the turbo pressure sensor then it should be okay.

 

It's obviously important that the new hoses won't come loose at any stage in the future and give the turbo pressure sensor incorrect readings , did you get a nice tight fit with the hoses?

Edited November 17, 2008 by merckx (see edit history)

[Anees]

I tapped into the turbo pressure sensor tubing on mine, it's difficult to tell from the picture, as long as you've fitted the T piece in the hose that goes to the turbo pressure sensor then it should be okay. Did you get a nice tight fit with the hoses?

 

 

I used a 3mm hose with a 3mm T peice, tight push on connectors and then cable tied - seemed tight to me

 

I have definetly fitted the T into the hose that goes to the turbo pressure sensor - the hose loops from the turbo sensor into the T, the other end of the T connects to the plastic bit with the round cap on (you can really see in the picture unfortunetly)

 

What pressure do you get when the ignition is on but the engine isn't running?

 

Sorry missunderstood the question. Will check when I get home. What should it be?

[Tricky-Ricky]

Could be a simple problem with your sequential system, i think there is a guide in the FAQ section, that tells you how to check.

[Anees]

What pressure do you get when the ignition is on but the engine isn't running?

 

Just popped home during my lunch hour.

 

With the engine off I get -4.7ish PSI

With the engine started I get -9.5ish PSI

 

Is their any significance to this?

[JustGav]

Just popped home during my lunch hour.

 

With the engine off I get -4.7ish PSI

With the engine started I get -9.5ish PSI

 

Is their any significance to this?

 

Yup, the boost gauge should read 0 at non-ignition in my mind, since it is at standard atmospheric. Sounds very much like the gauge isn't right...

 

You would get a vacuum reading on idle.

[Anees]

Yup, the boost gauge should read 0 at non-ignition in my mind, since it is at standard atmospheric. Sounds very much like the gauge isn't right...

 

You would get a vacuum reading on idle.

 

:blink:

 

I am actually using the HKS Camp 2, but the electronic boost sensor is exactly the same as the one used on their guages, except that I get to see the boost on the stock screen in the centre console rather then a seperate gauge.

 

I think I have a mechanical guage somewhere that I bought before deciding to do the HKS Camp somewhere, suppose I could put that in, and see if I get 0 psi when the ignition is turned on??

[merckx]

With the engine off I get -4.7ish PSI

Is their any significance to this?

Just like JustGav has said,it looks like the gauge/sensor are to blame.

[Anees]

Long short but I don't suppose anyone know if the sensor has some kind of calibration that needs doing? My instructions are in Japanese but I can't really pick anything up to suggest I need to calibrate.

[JustGav]

Trouble is the MAX boost I hit was a measily 4.2psi!

 

You are correct, should be 0.7bar on first turbo and 0.8bar

 

J

With the engine off I get -4.7ish PSI

 

4.2 + 4.7 = 8.9 which sounds about right (little low since 0.8 bar is about 11.6PSI (I think, I don't do imperial) Faulty gauge

[Anees]

Its working now

 

Been out for a blast and hit 14.1psi (I don't have a BCC installed yet so I don't know if thats max boost, or if the ECU is cutting boost)

 

The mods I have are front decat and a cat back exhaust - I was going to detail and explain all mods in another thread. The second cat is still in.

 

Next step is to install the Greddy BCC I have and see what I hit then. Hopefully if it stays around the same level then I can just add my boost controller to increase boost and I am at 1.2bar (obviously will do supporting mods too)

 

I don't really want to say why the guage wasn't working - I feel such a pratt so feel free to laugh at me.

 

 

On the HKS Camp, you can choose which sensors to display on the screen. I was basically looking at the wrong sensor.......... Oops!

 

I saw the IN_MAN gauge on screen and saw it reading in PSI and thought that was the correct gauge to be looking at. On most cars the IN_MAN is intake manifold pressure and it relates to boost pressure, but I hadn't realised that my seperate boost sensor was actually called IF_BOOST. As soon as I selected that I saw the correct guage!

 

I feel a numpty, but just glad it was something simple and hope I have given you a laugh (at my expense! )

/vbb/images/smilies/bbcode_oops.gif

 

The Journey to BPU continues...............

[Anees]

Never had a boost gauge before- I hadn't realised they were this much fun! LOL

[Guest Carsten]

I have a question about:

 

You are correct, should be 0.7bar on first turbo and 0.8bar when the second turbo kicks in.

 

I installed a Boost Gauge few days ago. When the first turbo kicks in ive got about 0.5 bar. On second turbo: 0.7 bar.

 

Is that normal?

[SteveC]

I get about 0.5-0.6 bar on the 1st turbo, and around 0.8 bar when the 2nd one kicks in... I very much doubt many of these gauges are perfectly accurate though.