My boost is playing up and just wanted to see if anything sounds strange.

 

my boost read -9 or is it -90 when engine off. it idles at -60 or -600. full boost is 0.5 bar but drops to 0.4 bar after a while. is this a boost leak or saftey/detting

marcus most cars go off the scale in standard form

on standard boost gauge

have you fitted the new one yet

get all the boost pipes changed

get in touch with smithy £20 for all the little pipe you will need

 

steve

i was getting the figures off my blitz one i fitted

Anybody with ideas on my boost readings?

anybody..

marcus most cars go off the scale in standard form

on standard boost gauge

steve

 

Hmm... (sorry to butt in with my own question!) so if I'm only getting a reported 5-6 mmHg on my Jap spec gauge at full throttle, does that mean I've got a problem too?!

 

Mark

Guys,

 

I'm no expert ;) , but when the engine is off (but ignition on) you should see 0 boost (midway on the standard gauge). If ignition is off the gauge goes all the way to the left.

 

For the other descriptions substitute my positions with real numbers :confused: !!!!

 

When idling I think it should be around the first small mark (going from left). When slowing on engine braking it should almost be at the large mark on the left (full vacuum).

 

On steady acceleration (no boost) it should go between about 1/4 and midway (from the left). At steady speed mine (at least) reads anywhere on the first left hand quarter of the stock gauge (depending on load).

 

On boost (full acceleration) it should go almost all the way to the rightv - penultimate mark (std car!) In safety mode I think it only goes about 1/2 way into right hand section of gauge.

 

Like I say, substitute number based on your gauge and needle position (J-spec, euro,etc.) I know a lot of people say the standard gauge is pants, but I've never had any problems with mine :nelson: (aside from someone plumbing it in wrong!) and I think it does exactly what its supposed to!

 

MarkW - 500-600mmHg is about 10-11.5 psig - I think this is standard boost :p

Ah good! That sounds about right then. Cheers Stuart :)

AFAIK the pressure guage works on a spring mechanism, which is attached to a rod which runs back and forth over a small wheel that moves the needle. When pressure is applied in the back of the clock in either way it will press it in or pull the rod (tensioned by the spring) moving the small wheel and thus in turn winding the needle on the gauge round (i dont know the technical name for it perhaps some one can fill me in ;)). The guage should read 0 normaly as this is how the tension is set from factory and the springs/mechanism normal resting place, when there is a negative pressure the vacum is sucked through the hose connecting to the guage hence putting negative pressure on the mechanism (by sucking) moving the rod back and the needle moves down, when aproaching positive boost the negative pressure lessens and once you go above 0 then the positive pressure will force its way through the vacum tube to the mechanism on the guage thus pushing it in and making it rise.

 

So you should be showing 0 when not running, and under 0 (will flux a bit) on tick over if the gauge works diff to above. Then you should see negative until the boost presure rises(you will hear and feel it as you know) then your guage should work into positive.

p.s having said that the boost guage I ripped apart was well over 10yrs old and so they could have changed the mechanism by now ;) lol

p.s having said that the boost guage I ripped apart was well over 10yrs old and so they could have changed the mechanism by now ;) lol

I think they have ;) - the sender is located on the driver's inner wing, near the bulkhead. This sends an signal to the electric gauge on the dash - hence it goes off to the left when off (rather than stay centered).

My standard guage reads 0 but my blitz reads a minus reading so i guess my blitz guage is a duff un.

If you blitz guage reads minus on tickover then that is correct. Mine reads around -20 on tickover and obviously when you start to put your foot down the boost pressure will rise into the positive.

 

Unless of course I am being a complete twat and have got it wrong .... I don't think I have though.

my blitz is reading a minus with engine switched off ill see if i can take some pics when i get home.

Blitz is reading minus when the engine is off? I bet the vac pickup is connected to the fuel pressure regulator :rolleyes: BIG no no!!!! :nono:

ill post some pics when i get home.

pics

Take a look at Andy's advice mate ... he knows his stuff ...

When engine off, if you disconnect the hose and let it hang free, does your gauge still read at this value? Looks like its plumbed in somewhere that should be OK, so may be a duff gauge (or needs recalibrating).

 

Cheers.

Yeah that guage is out. At least its plumbed in to the right place tho. The problem with using the pressure regulator line is that it is connected to a vacuum reservoir so doesn't always reflet the true pressure in the manifold itself...