Losing boost

P

Paul S3

Registered User
Joined
Oct 19, 2014
Messages
28
Reaction score
4
Points
3
Image
Image
Image
Hi all, I've been an avid fan of this forum for a long time an used it many times for info which seems to be so elusive anywhere else an finally got around to joining up. So I brought my s3 last weekend off everyone's favourite bidding site an it's a beaut, 2001 s3, it's got a full custom 2.5 de cat exhaust with cherry bomb tail pipe (not everyone's cup of tea but I like it), neuspeed induction kit, forge splitter dump valve, amd remap to a claimed 270 bhp, forge quick shift, drilled an slotted front discs (not sure the make) with ebc pads, an just the pads on the rear, bilstein shocks all the way round, an eibach springs, boost gauge, an a rather crazy sound system that could base the dead back to life, an lambo gallardo rep wheels. The car is so much fun to drive, an does everything it's supposed to but I noticed the other day that the boost which normally sits at around 14-15psi when on full boost, an after a few decent runs she sits on 10 psi an tonight after the same treatment she sat at 9psi. She seems fine when I drive her normally then give her a poke. Am I right in thinking it's the stock intercoolers? Any info or input would be greatly appreciated.
Paul.
 
Hi Paul, welcome to audi-sport.net. I will move this post over to the 8l section where you will get more help from the guys. Hope you enjoy your car and the forum. :) x
 
Scanned for fault codes?

14-15 psi isn't alot... stage one is normally higher than that and 270hp isn't stage one power...

Stock SMIC's are rubbish but don't really affect boost... does sound like a hardware issue though... I would try getting a smoke test if you can to see if you have any leaks

<tuffty/>
 
  • Like
Reactions: Sandra
Cheers tuffty, ill scan for fault codes tomorrow an post up what comes up, had another little spin an it did it again only peaked at 15 briefly then dropped to a steady 10, I could actually see the boost gauge dropping while revving thru 4500k-6000k. What kind of hardware do you think could be at fault? I'll get a smoke test asap to help the diagnosis. Cheers for the help
 
I'm surprised tuffty didn't mention the forge split r. It's quite possible that it is leaking boost
 
As above, the forge slit R is well known for leaking boost, I fitted one a while back and soon found it didn't like the heat so started to stick when hot and then soon after it wouldn't close fully and hold boost.

VCDS came up with something like intermittent boost leak cant remember exactly, i'm sure someone will correct me there

Steve
 
Ah skim read fail... bin the split-r right off.... :)

Replace it with a brand new OE valve at teh very least...

<tuffty/>
 
Tuffty if you could have any valve in the world for free, what would you fit in your car. (pretend you didn't care about looks, purely performance and sound)
 
Image
Image
Image
So I just scanned for fault codes an this came up. Slightly worrying about the misfire :( An now the hazards won't turn off!
 
Oh forgot to mention the split r is relocated to the cold side
 
Jenno007 said:
Tuffty if you could have any valve in the world for free, what would you fit in your car. (pretend you didn't care about looks, purely performance and sound)
Click to expand...

Most likely an OE one if running power up to around 350hp... Forge SuperSize (or dual OE valves if I could find a place to fit them) for power over that

Paul S3 said:
Oh forgot to mention the split r is relocated to the cold side
Click to expand...

Sorry dude... makes no difference... split-r is a crap valve... the actual end... VAG ecu's can cope with small leaks but don't run well with atmos or inherently leaky valves like the split-r...

From the fault codes it looks like your post cat lambda is missing or faulty, the fuel pressure regulator (FPR) could be blocked leading to the over rich code and the ECU thinks its over boosting (the spike to 15/16psi before dropping) so is trying to operate the N249 valve to dump boost using the DV but can't as no doubt you have an N249 delete in place...

Check the lambda for the cat (under the car just past the twin CATs)... there is a little plastic box where the probe plugs into on the floor pan under the drivers side footwell...

Remove the FPR (right hand side of the fuel rail as you look in the engine bay) and see if its clogged up... if so its advised to remove the rail and clean it and the injectors too...

Replace
the split-r with an OE valve

Reset fault codes and see what comes back...

Misfires are most likely a result of the over rich running btw

<tuffty/>
 
Cheers for the help, so I spoke to the last owner an he said it has the n249 delete, an he also said it should be boosting to 20-22 psi an suggested a boost leak an to test with a squirt bottle an some washing up liquid, would this be advisable? An the cat doesn't actually have any wires or sensors on it.
 
Get a smoke test done to check for leaks ideally... washing up liquid trick would be tricky to pull off accurately... check all pipes and hoses for signs of oil and splits etc...

If the cat has no sensors then you have an issue... post cat lambda should remain plugged in for adaptions to work unless fully coded out (although not seen a successful one as yet)... doubt yours is mapped out as the basic fault codes are popping up

<tuffty/>
 
Alex C said:
I always thought it was the pre-cat lambda that played with the fuelling adaptions and post-cat was just a cat efficiency check?
Click to expand...

Precat is the lambda the ECU uses to manage AFR and you are correct it does affect fuel trims... however the map requires the presence of a few other bits (it would appear) for the adaption process to work... unplugging post cat lambda and the N249 electrically are a couple that spring to mind...

post cat can be mapped out completely I think (never tried it myself as I still have a post cat lambda plugged in) but typically everything is left electrically connected and efficiency fault codes are mapped out to stop the CEL coming on... this method doesn't affect the logic that drives adaptions

<tuffty/>
 
  • Like
Reactions: Alex C
Right so a quick update, I've booked the car in for a smoke an vacuum test on Monday an hopefully that should point out the problem, if not then I'll replace the split r, only problem is I love the blow off noise it makes I know it's childish but I love the phsss when you let off the throttle, is there anyway of getting another dv that makes the same noise but isn't prone to leaking? Cheers.

S3 paul
 
Oh checked the cat to be sure an there are no sensors on the cat at all, the are sensors before it on the dp side but nothing on or after the cat.
 
Paul S3 said:
Right so a quick update, I've booked the car in for a smoke an vacuum test on Monday an hopefully that should point out the problem, if not then I'll replace the split r, only problem is I love the blow off noise it makes I know it's childish but I love the phsss when you let off the throttle, is there anyway of getting another dv that makes the same noise but isn't prone to leaking? Cheers.

S3 paul
Click to expand...

Split-R is sh*te... the end... sorry...

Decent airfilter and proper boost will give the noise... any atmos valve on std VAG management can cause running issues...

Fit an new OE valve or if you really must have bling under the bonnet then a Forge 007 or 008 but you still need to service the Forge ones regularly to maintain them

<tuffty/>
 
Tbh I'm not fussed how it looks in the slightest as long as it does what it's supposed to, I'll order a new oe valve tonight, I'm going to miss the classic dump valve blow off noise I must admit. Will the oe valve still fit ok even tho it's been relocated to the cold side, I'll take a photo tomorrow bcos I'm pretty sure the split r is supposed to be recirculating by a hose on the top? Mine doesn't have any other than the main inlet I think.
 
What air filter or induction kit do you recommend? Was thinking about the bmc one.
 
Paul S3 said:
Tbh I'm not fussed how it looks in the slightest as long as it does what it's supposed to, I'll order a new oe valve tonight, I'm going to miss the classic dump valve blow off noise I must admit. Will the oe valve still fit ok even tho it's been relocated to the cold side, I'll take a photo tomorrow bcos I'm pretty sure the split r is supposed to be recirculating by a hose on the top? Mine doesn't have any other than the main inlet I think.
Click to expand...

Take a pic mate... sounds like some idiot has royally screwed up fitment...

<tuffty/>
 
So how do I get one of the badger 5 induction kits? I've just been on their website an can't seem to find much other than throttle bodies an a kit for a seat, just ring up?
 
Paul S3 said:
View attachment 43090 So i got a pic this morning.
Click to expand...
why is there no hose to the top of the DV valve - is it supposed to **** boost away at all times?

its not even being used as a split re-circulation valve is it? it dumps all boost to atmosphere. Not much point doing a cold-side relocation on a dump valve
 
Paul S3 said:
View attachment 43090 So i got a pic this morning.
Click to expand...

Set fire to it mate... ;P

In seriousness... its not even recirculating and looks like you will need to source more than just a valve to put it right mate... looks like they have done a bodge job coldside relocation... at the very least you will need to source some hose and fittings to connect the new DV back to the TIP...

Bit of work to do mate to get her back into a working state lol

<tuffty/>
 
Cheers for the input, I knew it looked wrong as soon as I saw it! So I'll get some Hoses an what not along with the full silicone hose kit I'm getting an try an sort this mess out. An ill grab one of those badger 5 kits while I'm at it. Tbh I've driven cars with atmospheric dump valves before an knew something was up as soon as I drove it but wasn't sure exactly I thought it might be the spring in the dv at first then saw it didn't have a hose to recirculate. Half the fun is playing around with the car getting it right :)
 
Paul S3 said:
Cheers for the input, I knew it looked wrong as soon as I saw it! So I'll get some Hoses an what not along with the full silicone hose kit I'm getting an try an sort this mess out. An ill grab one of those badger 5 kits while I'm at it. Tbh I've driven cars with atmospheric dump valves before an knew something was up as soon as I drove it but wasn't sure exactly I thought it might be the spring in the dv at first then saw it didn't have a hose to recirculate. Half the fun is playing around with the car getting it right :)
Click to expand...

Fingers crossed you sort it as clearly the previous owner was clueless!.. :)

<tuffty/>
 
Evening all, another update..took the car to get it a smoke test and then after 2 days decide to tell me they can't do it now because the car is modified an they won't touch it. So after going to ace cafe last night to the VAG meet I was told about a vw/audi specialist who does engine swaps an is a turbo yoda who is local to me, the company is called vara technik, so the car is booked in for next month to get all the little niggles fixed an remapped while it's there as he is a official jabbsport dealer with rolling road. So also a slight curve ball but while I was at ace cafe I got talking to this fella an he was running a meth injected 650 awhp s3 8l that looked stock other that some lightweight wheels an brakes that were the size of dustbin lids an said I he could do it all again he would have gone the turbo r32 swap route which got me thinking :) so spoke to my guy at vara an he said he could easily do the swap an tuning, so seeing as my end goal was in the 600awhp range I've decided to go with a 3.2 r32 swap to start with an go from there :) I know it's going to cost a fair old lump of money but this is my car now, I dont intend on ever selling it so it can take as long as it needs to get done an done right! Any thoughts from you guys would be great.
 
  • Like
Reactions: jojo
Get it done and don't come back until you are ready for a build thread with lots of pictures LOL...

...and don't use the term awhp... thats a yank term.... we are British here you know ;P

<tuffty/>
 
<tuffty/> said:
Get it done and don't come back until you are ready for a build thread with lots of pictures LOL...

...and don't use the term awhp... thats a yank term.... we are British here you know ;P

<tuffty/>
Click to expand...
Is awhp a yank term? I thought it was just a different method of measuring the cars power. Instead of measuring at the fly you're measuring it at the wheels, and since its an awd car that results in awhp.

Once you know a car has x awhp, how else can you refer to how much power it makes? Because it wouldn't have x fwhp (bhp)
 
Jenno007 said:
Is awhp a yank term? I thought it was just a different method of measuring the cars power. Instead of measuring at the fly you're measuring it at the wheels, and since its an awd car that results in awhp.

Once you know a car has x awhp, how else can you refer to how much power it makes? Because it wouldn't have x fwhp (bhp)
Click to expand...

Pretty sure we have covered this before... all dyno measure wheel horsepower... its how they work... coast down losses are whats important and this gives you the flywheel horsepower...

Wheel horsepower will vary depending on the extent of these losses which are subject to things like gearbox oil temp, tyre temp, how much glue uses to stop wheelspin on the dyno from the more powerful cars...

<tuffty/>
 
<tuffty/> said:
Pretty sure we have covered this before... all dyno measure wheel horsepower... its how they work... coast down losses are whats important and this gives you the flywheel horsepower...

Wheel horsepower will vary depending on the extent of these losses which are subject to things like gearbox oil temp, tyre temp, how much glue uses to stop wheelspin on the dyno from the more powerful cars...

<tuffty/>
Click to expand...
Yeah you've explained that to me before. But if you only know your wheel horse power (some dynos don't give flywheel hp) you can't convert it yourself as far as I'm aware (you can make an educated guess). I know my car makes 530rwhp, I have no idea what that is at the fly so I couldn't quote it..

But back to my original point, how is saying awhp American?
 
Jenno007 said:
Yeah you've explained that to me before. But if you only know your wheel horse power (some dynos don't give flywheel hp) you can't convert it yourself as far as I'm aware (you can make an educated guess). I know my car makes 530rwhp, I have no idea what that is at the fly so I couldn't quote it..

But back to my original point, how is saying awhp American?
Click to expand...

It was kinda meant more as a joke dude... and whp is all the yanks talk about horsepower... that is all

<tuffty/>
 
<tuffty/> said:
It was kinda meant more as a joke dude... and whp is all the yanks talk about horsepower... that is all

<tuffty/>
Click to expand...
Ahh stupid me. I thought you knew a magic way to convert whp to fwhp haha
 
Jenno007 said:
Is awhp a yank term? I thought it was just a different method of measuring the cars power. Instead of measuring at the fly you're measuring it at the wheels, and since its an awd car that results in awhp.

Once you know a car has x awhp, how else can you refer to how much power it makes? Because it wouldn't have x fwhp (bhp)
Click to expand...

they will ALL measure atw, but then some dynos will ALSO measure coastdown losses and combine that to the atw figures to give fly.
atw only without a "measurement" of coastdown is not taking into account anything in rolling losses, and is'nt the whole story. It is of course the usa way of doing things but its subject to massive dyno lottery and their "atw" figures are more like are @fly figures such are the over reading dynos in abundance.
 
badger5 said:
they will ALL measure atw, but then some dynos will ALSO measure coastdown losses and combine that to the atw figures to give fly.
atw only without a "measurement" of coastdown is not taking into account anything in rolling losses, and is'nt the whole story. It is of course the usa way of doing things but its subject to massive dyno lottery and their "atw" figures are more like are @fly figures such are the over reading dynos in abundance.
Click to expand...
Yeah, the dynos I've had my cars on don't measure fwhp. So I thought it was a bit harsh that Paul was telling the guy not to quote awhp, when he might not know any different. But what I didn't realise is that Paul was joking haha
 
Haha well that escalated quickly! Note to self don't use the term awhp :) Well anyway I'm not going to go on about the swap until it's in progress an I've got a decent amout of work an pictures done. Until then il post some updates of the minor work I'm doing to the car like the full respray, wheel refurb an other little bits that happen along the way, I know to some people a full respray an wheel refurb aren't little jobs but as I spray paint cars for a living it's an everyday occurrence for me. Hope you all enjoy the thread as the car comes to life.
 
  • Like
Reactions: <tuffty/>
You must log in or register to reply here.

Similar threads

B
S3 losing boost
Replies
10
Views
2K
badger5
badger5
Stuart B
Another losing power under boost thread
Replies
29
Views
3K
hydro s3
hydro s3
Z
Losing speed
Replies
5
Views
1K
ZeroOne
Z
s3 beast
losing power!!!
Replies
7
Views
1K
<tuffty/>
<tuffty/>
bhavin1986
Losing Coolant!
Replies
8
Views
6K
A3 Oly
A3 Oly
Top
Back