Boost too low

[blu_s2]

Finally got all my intake plumbing 100% - no leaks - or at least I thought so. Tested with bungs and compressor and found a leak on the i/c outlet.

However, under driving I can only get ~1.1 bar boost max (third gen' ABY Homefry so expecting 1.4 bar).

It 'feels' as though the boost is actually being limited to this value, not leaking as such. Car pulls great up to this value and then just sits there (does not leak away until 4,800rpm+).

When I did have leaks I could get 1.3-1.4+ bar but boost would fall away quickly - this feels very different in driving now.

Any thoughts as I'm starting to lose patience but suspect the '5cyl specialists' would struggle to track it down so nervous about large bills from the qst's of this world.

Thanks in advance.

FWIW - bypass valve, wgfv, throttle pot, air temp sensor, water temp sensors, oil temp sensor and plugs all nearly new. Fuel filter replaced. All small bore hosing is silicone, + samco kit. MAF and contacts cleaned. WG diaphragm tested ok.

[s2avant]

Not much help, but I have a similar situation with my ABY avant. I can't get more than 18 psi. As with yours mine doesn't feel like a leak and the boost stays solid as it should. No early tail off as you would find with a leak.

As per your list all items are new except throttle pot. All the hoses have been changed to silicone.

Ben

[porkkis]

One thought. We consentrate too much on the electrics on these cars. What about the turbo itself? Could it be on its way out? Blocked and dirty IC from inside? Air filter? Broken catalyst blocking the exhaust? Sticky WG piston? I can guess more if these are not enough

[karlblues2]

Sticky WG piston? I can guess more if these are not enough

How do you check for sticky wastegate piston? That is something that I haven't checked on mine and it too dtruggles to make more than 14psi on a good day. The only thing I have changed is the I/M to an RS2 item from Martyn at VAGPARTS. Could this extra volume in the I/M affect the boost at all? What is the sensor that plugs into the top of the I/M?
Cheers
Karl

[Greg_S]

the volume is the same for ABY and RS2 its only if you had a 3b will the volume be any different. as for checking wastegate if you take the top off of it you can check the diaphargm and see its condition and move the valve by hand to see.

Greg

[newsh]

WGFV or wiring to it?

[porkkis]

Faulty WGFV wiring should appear as a fault code. Sticky valve not, but I understood that it has been changed. Or what ever FWIW means...?

And sorry to confirm that to you Karl. The IM you replaced is the same as now but just without the fancy porsche writing..

[blu_s2]

Or what ever FWIW means...?

"For What Its Worth"

and yes WGFV is nearly new and diaphragm has no leaks

and no fault codes are registered

[Doug_RS2]

there are a lot more places you can have leaks - like the throttle body housing to inlet manifold, injector seats, IM temp sensor, ISV.

I think you need to cover the engine in a soap that will bubble when the leak appears.

[jameswkr]

Hi Jim,
Looks like all you have left are:- a) Altitude sensor, b) knock sensors, c ) ambient temp variation (its cooler - so less boost ) d) Dodgy petrol, e) intake temp sensor. Was your first homefry not an original - no change to 3rd generation ? What about damage to your exhaust from the bash ? James.

[blu_s2]

Hi Jim,
Looks like all you have left are:- a) Altitude sensor, b) knock sensors, c ) ambient temp variation (its cooler - so less boost ) d) Dodgy petrol, e) intake temp sensor. Was your first homefry not an original - no change to 3rd generation ? What about damage to your exhaust from the bash ? James.

Temp and altitude sensor is also new (I forgot that from the list). I haven't done the knock sensors although they are on my 'refresh list' as well. I think the lower boost is more than would be expected for temp/barometric changes (usually only +/-0.3bar).

I'd really like to know if I am getting any knocking - does anyone know how I can tell? Certainly I cannot hear pinking but is there a better test out there?

I have had all 3 generations of homefry in mine at some point.

I only ever use Optimax.

I have checked manifold/downpipe and exhaust and cannot find a leak but I might get it checked 'professionally'.

Cheers