Standard boost gauge. Needle doesn't hit max marker.

[Scorpius911]

Hi guys,

Been lurking around here for a while but finally decided to throw something on the table.

I have a rev 2 Tubby that I've owned for a few months. The car was pretty standard when I bought it, was well looked after and not had any real issues. The car seems to have good power and drives fine.

Theres one thing I'm not sure about though. The needle on my boost gauge has never gone all the way to the top. At max, it always sits about 2 notches from the top. The gauge is standard, but I remember reading somewhere that Blitz dump valves can make the cars underboost. Not sure if this is true?

The only non-standard parts it has is this Blitz dump valve and a loud sports exhaust (not sure what type).

Where is the needle meant to sit on standard gauges? Anyone else have this problem?


*Reposted as I originally posted on the wrong board (Mk3 board)*

[Phill P]

Standard boost gauge is rubbish,get an aftermarket one.

Mine showed full boost but actually was only doing .5 bar,not .7

Paul

[Mike]

As above really /\ /\ /\ You can't really rely on the standard guage for accurate readings however assuming that it does work properly, on full boost in 3rd, 4th and 5th the needle should reach the top marker on the guage which is 10psi on the Rev2. Boost is limited in 1st and 2nd as far as I remember so I'd assume you'd get a slightly lower reading in those gears.
It could be your BOV, does it vent to atmosphere? If so I strongly recommend replacing it with a standard recirculating BOV, not saying that will sort out your possible boosting issue but the car will run better and will also become more economical to boot.

[jake]

I've got a rev 2 tubby too and it came with a manual boost controller which was set too high so it would fuel cut regularly.

After removing it (i.e. all back to stock) the gauge would only get about 3/4 of the way up, I've since fitted an electronic boost controller and discovered that the standard boost pressure is only around 0.45 bar, well short of the 0.7 it should be.

I've checked all the pipework for leaks so my only conclusion is I've got a weak wastegate actuator, which sounds like it could be your issue too. With the electronic boost controller everything is very stable, which supports my theory.

Again, as others have said, the only way to know what you've got is a good gauge. But, you can fit a footpump with an airbed adapter to the pipe between the turbo and actuator (it's awkward to get to and very short so you'll have fun!) and slowly pump it looking for the pressure at which it vents - not amazingly accurate but gives an indication.

Jake

[afennell]

Standard gauges can be a little unreliable, your best best would be to install a after market gauge for an exact reading. I think on my rev1 the boost gauge did not go all the way to the top and she was boosting fine.

I have heard that a bov venting to the atmosphere on a rev 1 – 2 can cause fuelling problem due to the are flow meter getting upset. Cant see it causing under boosting.

Also worth checking all hoses are nice and tight, from the turbo to the intercooler and to the throttle body, check for any splits in the rubber.

Also try re-setting the ecu. Chances are if the car feels fine it probably is.

[Timsmr2]

As others have said its best to get a good boost gauge setup to see what actually happening. If you dont want an aftermarket boost gauge installed perminantly then a friendly garage will probably have one that they can temporary plumb in to check the boost or you can borrow one of someone.

If the car is under boosting likely causes are:

1) The actuator has gone soft (happens with age) - can be fixed either by replacing the actuator or installing a boost controller (Manual boost controllers can be had for under £20)

2) A push type BOV is opening under the pressure (can normally be adjusted but pull types are better by design)

3) A boost leak (check all hoses and clips for damage and that they are secured properly.

[Cliff]

Which ECU Code does it throw up?

I'm no expert, but it might help diagnose the fault.