Defi gauge inaccurate
 

Hey ppl, just had my car retuned and the tuner said it is set to 1.3bar although my defi bf boost gauge is showing 1.5bar. The original tune (by a different workshop) was set to 1.2bar and this is what the boost gauge showed.

I'm trying not to doubt the tuner but I thought these expensive gauges where meant to be highly accurate. Anyone else's read off? Scared it might be actually 1.5bar which isn't safe so I'm told

using the Perth-WRX mobile app

Do you know anyone else with a gauge to test it? Did you do the re-calibration yet?

buy a $15 obd bluetooth scanner and get the app for your phone (torque if you have an android)
monitor the boost as per the ecu

Where did you buy your Defi from?
Which vacuum line is it connected to?

[QUOTE=dnbosiris;823174]buy a $15 obd bluetooth scanner and get the app for your phone (torque if you have an android)
monitor the boost as per the ecu[/QUOTE]

Wont work for this application. Stock MAP sensor is only good to about 18pound. (Least thats where it maxes out on my forester.) Even if actual pressure is higher than that, it will still only show that.

Really? Oh maybe I need to upgrade mine ... Although I have a sti Mani and sensors might read more

using the Perth-WRX mobile app

Who did initial tune?
Who did this recent tune?
What car?

[QUOTE=Jacob92;823187]Really? Oh maybe I need to upgrade mine ... Although I have a sti Mani and sensors might read more

using the Perth-WRX mobile app[/QUOTE]

Look at my track vids. Boost hits a wall at 18psi. But in reality its up to about 22psi. Thats recorded from the ECUs MAP sensor via Tactrix Openport 2.

[QUOTE=Jacob92;823187]Really? Oh maybe I need to upgrade mine ... Although I have a sti Mani and sensors might read more

using the Perth-WRX mobile app[/QUOTE]

Pretty sure you can buy 3bar MAP sensors (2 bar above atmospheric, and 1 bar below). Just need the pressure to voltage rescaled in the tune. But its not really worth it unless your going for speed density etc.

[QUOTE=Bram;823183]Wont work for this application. Stock MAP sensor is only good to about 18pound. (Least thats where it maxes out on my forester.) Even if actual pressure is higher than that, it will still only show that.[/QUOTE]

what car?
the reading my MY02 sti tops out at 22.3psi according to torque app (android)... this is on stock intake, turbo, ecu etc

[QUOTE=dnbosiris;823194]what car?
the reading my MY02 sti tops out at 22.3psi according to torque app (android)... this is on stock intake, turbo, ecu etc[/QUOTE]

Interesting. Im only going off my car, which is a MY05 Forester XT. It maxes out, according to the data logs, at around 18psi.

[QUOTE=Bram;823196]Interesting. Im only going off my car, which is a MY05 Forester XT. It maxes out, according to the data logs, at around 18psi.[/QUOTE]

Bram - It's probably your stock boost solenoid that can't read any higher... replace with grimmspeed 3port and the likes...should have been one of the initial mods on the car along with a tune/fuel pump.

[QUOTE=RJ999;823202]Bram - It's probably your stock boost solenoid that can't read any higher... replace with grimmspeed 3port and the likes...should have been one of the initial mods on the car along with a tune/fuel pump.[/QUOTE]

Done that about 4 years ago.

Car is tuned to run 22-23 psi. And its been doing that for a while now.

The ECU doesnt really need to see higher MAP. The cars are MAF based. y
You only realy want it for finer closed loop boost control, or a speed density hack.

The OEM Subaru MAP sensor is good for 2-3bar depending on model/year. By the way who tuned your car?

Well. Maybe the MAP sensor may be able to handle higher. But the ECU will only see up to 18psi on mine. When i plug the readers/loggers in to the OBD port, it never shows more than around 18psi.

Also. A 2bar MAP sensor can only actualy see 1bar of positive pressure. Remember, atmospheric pressure is already at 1bar. ECUs talk in absolute. We commonly talk relative. When we say 1 bar of boost, we are tecnically saying 2 bar absolute. (Give or take for minor variations in atmospheric pressure)

ASG / Sean tuned the engine.

Anyways. This is getting well away from the OPs original problem.

[QUOTE=RJ999;823202]Bram - It's probably your stock boost solenoid that can't read any higher... replace with grimmspeed 3port and the likes...should have been one of the initial mods on the car along with a tune/fuel pump.[/QUOTE]

Boost solenoids don't read anything they are a solenoid, not a pressure sensor.

They're simply an electro magnet, a return spring & a steel rod with a rubber valve seat on one end:

[IMG]http://blog.perrinperformance.com/wp-content/uploads/2013/10/tech_boostcontrol_boostsolenoidatrestsmall.jpg[/IMG]

Subaru factory MAP sensors have varied a lot over the years.

The reason you want one that reads above the boost you currently run is for safety. The factory ecu is blind to boost it cannot see - be it a deliberate boost increase or a system failure.

[QUOTE=Rossco;823208]Boost solenoids don't read anything they are a solenoid, not a pressure sensor.

They're simply an electro magnet, a return spring & a steel rod with a rubber valve seat on one end:

[IMG]http://blog.perrinperformance.com/wp-content/uploads/2013/10/tech_boostcontrol_boostsolenoidatrestsmall.jpg[/IMG]

Subaru factory MAP sensors have varied a lot over the years.

The reason you want one that reads above the boost you currently run is for safety. The factory ecu is blind to boost it cannot see - be it a deliberate boost increase or a system failure.[/QUOTE]

So what does the ecu do with boost levels when they go above levels it can see?

Usually it will either throw the check engine light on & cut the fuel (boost cut) or go into limp mode on the later cars & run waste gate pressure (5-7psi).

With some open source tunes (Rom's) there's code that disables the factory over boost safety features - not great for reliability in the long run. Most tuners cap the upper boost limit well below the MAP sensor's limit or they change to a GM 3bar sensor.

Sean told me the same thing about my defi boost gauge. Mine reads 1.5 but car is tuned to 1.4bar which is shown on my dyno graph. If you doubt him they can supply a dyno plot showing manifold pressure.

I have been meaning to try different size t-pieces etc to see if its a line restriction issue but havn't got around to it yet.

Now, Im going to struggle to remember if it was here, or wrx.com.au or Rexnet (RIP), but someone had 2 gauges installed [U]side by side[/U] [B]on the same car[/B] - a DEFI and a cheap shit SAAS, and took pictures to compare the differences.

You'll never guess which one was more accurate - the cheap shit SAAS. The DEFI was consistently out.

The genome defis are gonna be like 10+ years old now. No surprises there.

Sorry to go off topic in the topic :D

[QUOTE=nick73;823167]Do you know anyone else with a gauge to test it? Did you do the re-calibration yet?[/QUOTE]

Did the recal, but it was more the finding the zero point which it does.

The car is a 2006 wrx.

Orginal tune (TBE exhaust, TMIC and CAI) @ Evo-R. Tuned at 1.2bar. Defi gauge read 1.2bar

Recent tune (VF48 turbo, fuel pump, Headers and Ecutek tune) @ Race Torque. Tuned at 1.3bar (not shown on dyno graph but verbally told), Defi gauge reads 1.5bar.

Gauge is a Defi Advance BF w/control unit 2

I have read some people having inaccurate readings. If thats the case then the pricetag is digusting. I want to believe the tuner but feel like asking for a readout showing the boost figures as the gauge was accurate initially. But feel like that might be rude in not trusting. just really don't want the car to be running that high

1.5 bar is not that high for your setup man, it's likely only there for a second then tapers down. I doubt race torque would leave you with an unsafe tune.

It does hit 1.5bar and then slowly drop back to 1.3. I was under the impression that over 1.3bar for a wrx without forgies is dangerous ground

using the Perth-WRX mobile app

Those levels of boost alone arnt going to bring down an engine. As long as the afr, timing etc are set safe by the tuner, then 21psi of boost is ok. Though I don't know much about the internals of a ej255.Someone correct me if I'm wrong.

Just ask Lane for a full dyno plot, he should have given you one to begin with.

You're worrying over nothing. It's because ambient temps are colder and thus a colder more denser charge = slightly more boost. It will be within the parameters of the tune.

An additional 0.2 bar is not going to wreck your engine. Your air flow meter will see to that, as will the map sensor too. I'm sure if it was an issue you'd be hitting boost cut long before there's any danger of damaging the engine.

Even new Defis are known to over read too. So just enjoy the small amount of extra power you have until it starts warming up again.

[QUOTE=Nikt3ndo;823302]Sorry to go off topic in the topic :D



Did the recal, but it was more the finding the zero point which it does.

The car is a 2006 wrx.

Orginal tune (TBE exhaust, TMIC and CAI) @ Evo-R. Tuned at 1.2bar. Defi gauge read 1.2bar

Recent tune (VF48 turbo, fuel pump, Headers and Ecutek tune) @ Race Torque. Tuned at 1.3bar (not shown on dyno graph but verbally told), Defi gauge reads 1.5bar.

Gauge is a Defi Advance BF w/control unit 2

I have read some people having inaccurate readings. If thats the case then the pricetag is digusting. I want to believe the tuner but feel like asking for a readout showing the boost figures as the gauge was accurate initially. But feel like that might be rude in not trusting. just really don't want the car to be running that high[/QUOTE]

I guess you didnt read my post further up. Ring up ASG and ask for a dyno plot with boost and AFR's on top of the standard power and torque plot. Its not rude, you paid for the tune so you are entitled to ask for the manifold pressure readings to make sure they are what you asked for.

Simon: ej255 and ej257 have identical internals, only difference between the 2 are the compression ratios of the pistons

Nick, here is my last tune with Lane. You can see the overshoot at the start of peak boost, it's pretty normal mate nothing to be concerned about.

Just ask Lane for the full dyno sheet, he wont be offended.

[url]http://www.perth-wrx.com/vb/819617-post133.html[/url]

[QUOTE=RJ999;823205]The OEM Subaru MAP sensor is good for 2-3bar depending on model/year. By the way who tuned your car?[/QUOTE]

Going off topic here again. (sorry) But, Just a follow up with my 18odd PSI limit on the forester XT. Here is a screen shot of a data log showing the boost capped at 18.4275 PSI. The log was recorded via a Tactrix. But you get the same results when using a ODB2 reader etc. The boost does physically exceed that. Sits somewhere around 22psi (1.5bar). Yet my ECU only ever reads that when queried via the OBD2 port. Perhaps the ECU/sensor can see more, but is not able to show more when queried via the diagnostic port?

When originally tuned, I did have to go back for more revisions to get boost control fully dialed in. Im guessing that if my set boost exceeds the limit of what the ECU can see, then the boost control tables must be all kinda set up as an 'open loop' controlling. Not as a closed loop?

My boost, when set at 'wastegate actuator pressure' is at about 18-19psi, due to the heavy duty actuator on the turbo. I have a 3 port on there to just get a bit more out of it.

[IMG]https://lh6.googleusercontent.com/-wa5-c-lCEXY/VWkEdsmB-MI/AAAAAAAABQA/jOP_04q0ph4/w685-h803-no/pwrx%2Bboost%2Blimit.bmp[/IMG]