Can someomne with a boost gauge tell me what it should read at idle.

I'm hunting a boost leak and wondering if its a vacaum leak somewhere

-16 In HG

I thought as much, I spend all day looking at it, but don't pay that much attetion to what it does on idle lol

Mines sat around - 28, so does this mean a vac leak ??

I got no codes, but over 5k it's crapping out the boost so I think something is leaking

Pass i dont know, i dont even know if -16 is right lol

I guess I should wait for a few more replies before I take the hammer to the engine bay lol

Well i got mine mapped and scanned 4 weeks ago and no faults, but i suppose you have no fault codes either

Looking at mine now its warmed up its hitting -18

-0.6bar ~ -0.8bar, it depens if the AC is turned on...

If the boost is OK till 5000rpm and then starts to fluctuate you don`t have a boost leak, more likely a problem with fuel system. Boost peaks around 3000-3500rpm,if there was a leak you will noticed it first here.

There may be a slight flutter through the revs, where it drops but its tiny if at all.

But I see what you're saying, that kind of puzzled me as you say its high up max pressure was reached a while back lol

So fuel you say, any suspects I should be looking.

Dare I say it .. fuel filter lol

Yeah, change the fuel filter, but be careful with those clips!!!!

Mione reads about -18 inHg on idle too. It was around -12 but I had a split breather pipe and EML light.

Fuel filter is really cheap so change it but before you start throwing some serious cash first check&double check for any possible leaks and your fuel trims. Second thing what i would do is to check fuel pressure with fuel pressure gauge at idle and from 2000~7000rpm (3rd or 4rd gear). Fuel pressure at idle should be iirc around 2.5-2.8bar, and when you boot it 3bar(3bar FPR) base pressure + your current boost, any thing below that and you should install a new fuel pump. Me and 2 friends had problems with stock fuel pump,allegedly there were problems with early models according to authorized škoda mechanic.

Edited 26 May, 201214 yr by Gonzaga

Damn it mines 10.7 split breather hose then?

Sent from my GT-I9100. Not a Crapple!

Anyone who actually knows what they are on about care to pipe up, its like the blind leading the blind here lol

From what I can work out when the engine is ticking over there should be a high vacuum. If its got a lower vacuum then maybe there's a split breather pipe?

Sent from my GT-I9100. Not a Crapple!

Wasn't having a go lol

We just seem a little unsure

Wasn't having a go lol

We just seem a little unsure

Err I know that lol, I'm trying to figure it out myself as this is the first I've heard of it lol

Sent from my GT-I9100. Not a Crapple!

Mine normally reads about 12 psi on idle. But thats through torqe app so not sure how acurate it is.

When engine idles, TB is closed. Then you should see maximal vacuum, if it`s not then you`ve got a leak somewhere usually Y breather hose which is connected to the top of the engine and the S pipe which is connected to check valve underneath intake.

Part 2 & 5; http://www.briskoda.net/forums/topic/239183-engine-management-light-came-on-today-breather-pipe-split/

Edited 26 May, 201214 yr by Gonzaga

he said on idle, he's reading around -28 inHg of vacuum, whcih is really strong. A higher number means a better vacuum. Assuming his gauge is OK, I's probably rule out a vac leak TBH. If there was a leak, the reading would go up towards 0, rather than the other way round. The only thing I can thing of that would cause a really strong vacuum like that is a really gummed up throttle plate (manifold under strong vac) or a diabolically dirty air filter (whole intake system under negative pressure, but I doubt it).

What are your boost readings like? A good mapped K03s should spike around 21-ish PSI, and then hold 15-16 at the rev limiter. Does it drop suddenly or slowly as the revs build?

Try looking at vagcom to see what you airflow readings are.

Edited 28 May, 201214 yr by rk696

Well Torque says about -23 on idle,gauge says -28, maf pulling 190 g/s so that looks fine

It's always been like you say to the limiter, until now, Inatke temps look fine @ around 35c, evrything looks clean around hoses, tb cleaned a few months back,

I hit just over 5k in third and it drops back 5psi, then flutter about going back up a bit, but very wobbly on the way back up, I think it did it in second the other day aswell

What about N75's do they just go dead or can they be twitchy ??

PCV valve at the back near the DV has been mentioned too, any idea on these ??

he said on idle, he's reading around -28 inHg of vacuum, whcih is really strong. A higher number means a better vacuum. Assuming his gauge is OK, I's probably rule out a vac leak TBH. If there was a leak, the reading would go up towards 0, rather than the other way round. The only thing I can thing of that would cause a really strong vacuum like that is a really gummed up throttle plate (manifold under strong vac) or a diabolically dirty air filter (whole intake system under negative pressure, but I doubt it).

What are your boost readings like? A good mapped K03s should spike around 21-ish PSI, and then hold 15-16 at the rev limiter. Does it drop suddenly or slowly as the revs build?

Try looking at vagcom to see what you airflow readings are.

All depends on supporting mods!

Mines peaks 21, holds 15/16 then tails off as i have the stock cat in place

Well Torque says about -23 on idle,gauge says -28, maf pulling 190 g/s so that looks fine

It's always been like you say to the limiter, until now, Inatke temps look fine @ around 35c, evrything looks clean around hoses, tb cleaned a few months back,

I hit just over 5k in third and it drops back 5psi, then flutter about going back up a bit, but very wobbly on the way back up, I think it did it in second the other day aswell

What about N75's do they just go dead or can they be twitchy ??

PCV valve at the back near the DV has been mentioned too, any idea on these ??

MAF readings look spot on, like you said. As for suddenly dropping to 5 psi, this sounds like it might be a soft limp mode of some kind.

The N75 can look OK, but still be at fault. I had to change mine, as it was surging on boost (going from 13-17 backwards and forwards). They work on a PWM cycle, so turn on and off at high frequency. If the valve is sticking or operating slowly, it can cause the ECU to over-react and dump too much boost, like mine was doing. If the N75 fails completely, the car will only boost to about 6 PSI, as the wastegate will operate at it's natural spring pressure without the N75 controlling it. It's a failsafe to stop the turbo self destructing.

The Upper PCV valve (technically a PRV, or pressure release valve) has a diaphragm and a spring, a large hole and a small hole in it. It works in conjunction with the PCV valve under the inlet manifold. At idle or vacuum, it's designed to let air from the filter through the large hole to the manifold via the lower pcv valve, along with crankcase gases. The diaphragm is normally open so that the engine block doesn't go under vacuum and lose oil through the system. It's like a controlled vac leak, but the air has been through the MAF sensor, so isn't a problem. Under boost, the valve works the other way round and the diaphragm closes with the lower pressure in the TIP. The boost closes the lower PCV, and the crankcase gases go back up the system to the upper prv valve and go through the small hole to the turbo inlet. If there is too much pressure (excessive crankcase gas, knackered engine etc), the diaphragm will open and let the excess pressure go through.

If the lower PCV valve was broken, boost could theoretically go through the PCV system, open the diaphragm and go back to the inlet pipe, causing a leak, but it wouldn't be a massive leak, as the lower valve is so small.

Just realised how big this post is lol.

Anyway, I don't think it's a boost leak, as it drops off so suddenly. Limp mode usually occurs when the ECU senses too much boost. It feels like hitting a wall.

All depends on supporting mods!

Mines peaks 21, holds 15/16 then tails off as i have the stock cat in place

Yep, I have the stock cat too, so it's about the same. I'm just trying to demonstrate how the boost doesn't stay constant and tails off towards redline, as the turbo can't keep the pressure up. On a standard map, it will hold 10 psi all the way over the rev range, as it was designed to be run at that boost level.

Edited 29 May, 201214 yr by rk696

At the redline im putting out about 10-11psi

But i change at 5.5k rpm when its still about 15psi and it drops back to 4k rpm (still 15 psi) fastest way to drive it

Edited 28 May, 201214 yr by BigJase88

Thanks for the info. Fuel filter has also been mentioned, how that effect it ??

If the fuel filter is blocked of restrictive, it can cause fuel starvation at high RPM, which could cause a limp mode if the mixture goes too lean. Should put the EML light on though, I would have thought.

Well I gotta a spare N75 off an AGU golf(IIRC) block and a fuel filter is cheap enough, theres something bugging me about the FF though, I'm sure theres something to watch for when fitting