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UKPonchoMan
24-12-2011, 01:11 PM
Well, I finally got around to fitting my boost gauge, but the readings its giving are incorrect, which leads me to suspect I've done something wrong...

With the ignition on, the gauge reads zero:-

http://www.usaf-sig.org/Miscellaneous/Legnum_Boost_Gauge/Legnum_Boost_Gauge_001.JPG

With the engine on, at idle the gauge is reading -19PSI!

http://www.usaf-sig.org/Miscellaneous/Legnum_Boost_Gauge/Legnum_Boost_Gauge_002.JPG

Attached are a couple of pics of the install:-

http://www.usaf-sig.org/Miscellaneous/Legnum_Boost_Gauge/Legnum_Boost_Gauge_003.JPG
http://www.usaf-sig.org/Miscellaneous/Legnum_Boost_Gauge/Legnum_Boost_Gauge_004.JPG

The only thing I didn't do when installing was to fit the air filter between the boost gauge sender and the T-piece.

Doers anyone have any ideas what's going on here?

Thanks again guys!!

Chris

elnevio
24-12-2011, 01:17 PM
That is normal behaviour, as the boost gauge also measures the vacuum. The reading at idle is also about spot on too. Zero on the gauge is the same is the outside pressure, so is the expected reading when the engine is off.

Whilst driving, any positive reading is the extra boost pressure being generated by the turbos.

You will also note that if you use engine braking, you can get the negative reading almost all the way to -30 inHg! (it reads the negative in inHg and the positive in PSI)

UKPonchoMan
24-12-2011, 01:26 PM
Oh.... In my (potentially simplistic) mind I was expecting zero boost at idle, going to +12psi or so.

This makes things doubly weird then as it normally goes up to about -5psi under hard acceleration but I've seen it spike close to +5psi

elnevio
24-12-2011, 01:39 PM
The best time to measure it (on a clear straight bit of road) is in 3rd gear, about 3000 rpm, and plant it. After a second, I would expect a steady reading of about 9/10 PSI which then starts to tail off as the red line approaches.

UKPonchoMan
24-12-2011, 01:45 PM
Thanks Nev - you've given me a good excuse to go out and find out!!

Would that mean that the ACTUAL boost is +9/10 psi then?

elnevio
24-12-2011, 01:50 PM
Yes, that's the actual additional pressure above normal air pressure. This is the 'boost'.

If you take normal air pressure to be about 15 PSI, then the actual pressure that the intake system is seeing would then be about 24/25 PSI.

UKPonchoMan
25-12-2011, 01:13 PM
Well, I "had" to go out yesterday and for some reason it turned into a slighly longer trip than planned :)

Following your suggestion, I saw 8/9psi under hard acceleration in 3rd from about 3000rpm - this is about spot on for a stock VR4 I think? Methinks it's time for my Greddy EBC :)

elnevio
25-12-2011, 04:17 PM
Sounds entirely reasonable to me! /yes

UKPonchoMan
25-12-2011, 08:52 PM
Absolutely... :) Sure 12psi will feel a little more "lively" :)

aboo
25-12-2011, 09:13 PM
Why stop at 12? Crank it up to 14;)

Nutter_John
25-12-2011, 09:22 PM
Why stop at 14? Crank it up to 17 ;) :D

UKPonchoMan
26-12-2011, 01:03 PM
From what I've read, anything over 12 is risking the turbo exploding - given that this is my daily driver and needed for work, it's probably not a risk I should be taking... No...I'd need to replace the turbos before considering something like that ;)

psbarham
26-12-2011, 03:09 PM
Why stop at 14? Crank it up to 17 ;) :D

I agree, Mine now runs 1.2 bar which livens things up considerably, although the poor sod in the vantage v8 i royally pissed all over the other day wouldn't agree /lol

sabreuk
26-12-2011, 05:17 PM
Im struggling to get anything around 1bar or over without hitting fuel cut :( resulting in me taking the manual boost controller off and running standard boost again. But then I was using an eblag el cheapo nasty Mbc

UKPonchoMan
27-12-2011, 03:24 PM
I've got a Greddy Profec B-Spec II to go in so will hopefully be OK!!

Nick Mann
27-12-2011, 05:16 PM
Upping boost shortens the life of your turbos, that is certain. But I wouldn't suggest you need to fit new tubs before you crank the boost up. Just keep an eye on the amount of smoke coming out of the exhaust on over run and when you notice it, get new tubs! Your current tubs might last 5 miles on standard boost or 50,000 miles on raised boost, so why not see how they cope before shelling out on new/refurbed ones? Turbos usually fail by allowing oil past the bearing, which is seen by blue smoke coming out of the exhaust when your boost gauge shows high vacuum. It doesn't immediately make the car undriveable, so waiting a few days for the tubs to be changed doesn't leave you stranded.

aboo
27-12-2011, 08:35 PM
Im struggling to get anything around 1bar or over without hitting fuel cut :( resulting in me taking the manual boost controller off and running standard boost again. But then I was using an eblag el cheapo nasty MbcYou'll need a reflashed ECU or piggy back to raise the fuel cut to get over 1 bar/yes