john banks

Looking for consistent boost in all gear with the EBC I have been watching my (admittedly cheap) boost gauge which I know underreads by 1 PSI. However, in future I am not sure I'll bother hugely.

On occasions it can show anywhere from 15.5 to 17 PSI when the MAP sensor is giving out a steady 18 PSI signal, and the performance feels equal each time. The EBC gives a characteristic LED flashing pattern which I programmed in when it is at boost target and it normally holds this from 2300 to 5000 RPM. Oddly it has little correlation with the boost gauge! I would have thought at least the boost gauge would have a consistent error, unless the MAP sensor is in error, which I very much doubt. Also had similar effect with the Dawes, but I thought that was just the Dawes.

Also the gauge can be too slow to see a fuel cut as it cannot keep up with the rate of spool up.

Thought this might help those who are struggling to explain odd boost behaviour/unpredicatable fuel cuts.

Chris.Palmer

Have you tried the slow boost guage mod -

http://www.scoobymods.com/forums/sho...c&threadid=210

this may help.

Regards,

Chris

[Edited by Chris.Palmer - 3/27/2002 2:42:02 PM]

john banks

Are they putting narrow gauge tubing from the source to the gauge?

mutant_matt

Chris, why does that fix it then?

John, perhaps you need s better faster reacting gauge like a Defi perhaps as mine is easily as fast acting as the Autometer in the vid clip!!! (and I know someone who's selling his )

Matt

john banks

Probably don't need it now I have the EBC? Anyway, I prefer spending money on making it faster not seeing how fast it is

[Edited by john banks - 3/27/2002 3:11:53 PM]

mutant_matt

Cosie Convert

Yea but only if it's less than 10 pounds

Moles Dad

I did think about "Scotts and spending money" but I thought I'd leave it as I'm of Scottish origin too!

Cheers, MD.

john banks

I'm as English as they come.

mutant_matt

So why that dodgy kilt in your wedding photos?

Matt

john banks

Had to pretend to get a Scottish lass.

AndrewC

John,

Are you sure the MAP sensor reading is accurate, any noise on the ground or ARef lines on the AVR will cause the ADC to underread, effectively bringing your achieved boost down, if your EBC is achieving really good spool up and holding steady boost the car might feel really quick although you are actually holding less boost?

I am not saying this is what is happening, but, I had problems causing an underread by the ADC of about 1.0 psi, all this is conjecture of course because none of us have had our MAP sensors checked on a calibrated rig!

Andrew...
Andrew...

James_PowerMad

My Sampled MAP signal, and a dodgy cheapo Halfrauds boost gauge match up pretty damn well, apart from a slight offset due to variation in atmospheric pressure (remember that the MAP sensor measures absolute pressure, not relative like some or ??all?? mechanical boost gauges).

john banks

Short of putting an oscilloscope on (which I don't have access to) I can only guess from other information.

I am using a power supply on the development board which is designed to take AC or DC supplies and has pretty comprehensive filtering with some nice big capacitors and a voltage regulator. Running this off a DC supply leads to very stable values through the ADC. The ADC reference is connected to this 5 V supply.

The MAP sensor is powered from the ECU 5 V supply.

It also correlates well with MAP reading on a DVM which holds pretty steady at target boost - ie changing by at most by one terminal digit, but often not at all. When target boost is reached the needle is steady, it is just that it is not in the same place every time.

So I suspect crap gauge syndrome? Does this seem reasonable based on the above? I don't see what else I could do to clean it up. I can tell I think that it is not wandering on boost from what I can measure.