Boost (yet again)

[Heat Seeking Missile]

I've just (temporarily) plumbed ny nice new VDO boost gauge and taken the car out to make sure that everything is sound and there are no leaks. Its displaying 1bar of boost at full throttle, is this about right? I read somewhere that full boost should be 1.2bar but I cant remember if that is the overboost facility or not.

Thanks in advance,

Mark

[S-Express]

Hi Mark, can't believe you haven't homefried yet - that gives you 1.4 bar

[Heat Seeking Missile]

Trust me, its next on the agenda, now I've fixed the Vectra, once I've replaced the head gasket on the Rover and welded a patch on the floor of the Transit and.......

If its still leaking somewhere though, a homefry is kinda pointless at the min. Cant be a huge leak for only 0.2bar to be lost can it? I'm pretty sure my boost gauge addition hasn't made a leak.

Mark

[S-Express]

Sell the rover and the vectra - then optimise the S2 - simple really :mischeif:

[Heat Seeking Missile]

Nah, I refuse to give my mum the satisfaction of me EMPTYING the drive rather than filling it

So, anyone got any ideas where I might be losing this 0.2bar? Doesn't seem to be a huge problem but I'd rather get it sorted before I start getting even more power hungry.

Mark

[S-Express]

suggest you fit a set of silicone hoses anyway as the extra boost is going to kill old standard hoses (killed mine) - then, if you're lucky - you may have your boost back.
Check the hose going into the throttle body anyway - seems pretty common to get a split in, round the back where you can't see it, you'll have to take it off really....
You putting decent fuel in it?

[Heat Seeking Missile]

Ah yes. I remember you saying about popping hoses. They may be leaking a small amount and accumulating in a loss of 0.2bar?

I'll have a look at the throttle body hose tomorrow. I put Optimax in it every time I fill up.

Mark

[Heat Seeking Missile]

Just taken a look at the rubber hose that connects the long metal intercooler pipe to the throttle body and it looks to be a little cracked and beginning to perish. Is this one included in the Samco hose kit? If not can I get an OE replacement one for Euro Car Parts or something?

Mark

[Rusty]

Peak boost should be 1 bar on a standard ABY on overboost, 0.8bar on normal dropping to about 0.6 at the red line. Do a WOT run in 3rd from 1500rpm to the rev limiter and watch the boost gauge...

If you have a leak then the boost gauge usually fluctuates a bit, it should be steady as a rock!

[Heat Seeking Missile]

Peak boost should be 1 bar on a standard ABY on overboost, 0.8bar on normal dropping to about 0.6 at the red line. Do a WOT run in 3rd from 1500rpm to the rev limiter and watch the boost gauge...

If you have a leak then the boost gauge usually fluctuates a bit, it should be steady as a rock!

Oh, that sounds about right then, for some reason I thought overboost was 1.2bar and should run normally at 1bar. I was a bit worried in case I'd damaged the gauge or had another vacuum leak. Its standard bar a panel filter and exhaust but that wont have any effect on it I dont think.

Thats cheered me up I think I should still replace the hose to the TB though, it really doesn't look too clever.

Mark

[HPmuirt]

Peak boost should be 1 bar on a standard ABY on overboost, 0.8bar on normal dropping to about 0.6 at the red line. Do a WOT run in 3rd from 1500rpm to the rev limiter and watch the boost gauge...

Couple of points...

Firstly, a stock ABY runs 1bar full boost (dropping to 0.8) and 1.15bar in 'overboost' which is probably why you were expecting 1.2bar.

Secondly, do a WOT test in 4th or above as according to Audi, overboost is only available in 4th, 5th and 6th gear. The best way is to do a run from low rpm in a high gear, as Officer Casey suggested, but in order to get full boost, let alone overboost, you need to stamp on the throttle, rather than easing it down.

I find that running up hill in 5th with the brakes gently applied creates perfect overboost conditions.

Cheers n

Si

[AndyP]

Putting the brakes on to get overboost, great idea

[HPmuirt]

Putting the brakes on to get overboost, great idea

Sounds odd, but it works for me

Cheers n

Si

[Rusty]

Cheers Si, good effort on the brakes, heel'n'toe or left-foot? :mischeif:

Don't forget that the where you attach the boost gauge can make a difference as there is a pressure drop along the manifold and some boost gauges aren't that well calibrated, mine's out a bit! IMO it's more just to check that oyu have solid boost than get an exact figure...

[Heat Seeking Missile]

Thanks for all the replies everyone. Everything appears to be in full working order. Nice!

Mark