New S3 Owner with Graphs - Wheres my BOOST

[audiss3 10]

hi all,

Having recently acquired an S3 I have been having bit of a rough time of it! From day 1 I have felt that the car just didn't seem to deliver the right power when trying to accelerate through the range. I am experiencing whooshing sounds, and not getting the power I would expect i guess.

The car is a 2001 S3 with a REVO map, uprated DV and pipercross panel filter. I have in the last two weeks done the following:-

New vacum hose near dipstick fitted (was split)

New coolant thermostat (was stuck open)

New Genuine Audi MAF (old one was dead)

The car seems a bit more responsive now, and below are the figures I got on a VAGCOM run (i had to let off the throttle at circa 5,200rpm as I ran out of road). Can you tell me what you think of the figures and is there cause for concern? I am worried about the boost figures which show the actual boost I am getting is significantly lower than the requested boost, and also the air flow i have read should be over 200 g/s for a mapped car? However I think I would have exceeded the 250bhp mark if I kept my foot on it?

Can anyone advise on what could be the cause of this given the background so far?

Figures :-

[Decked 0]

Is that map of your actual car?

The Vag-com boost figures look very low! You's getting about half a bar..... I'd expect double that. The flow isn't too bad, it could do with getting a little higher but as you say, you ran out of road!

Looks like a boost leak if you ask me, have you checked all the hoses? Is the DV asking?

[MattS3 0]

I've still got the graph of my 02 plate 225 S3 which had Revo.

I'll try adding it here now....it may help. (it may not)

[shark_90 8]

You definitely have a boost leak. Check your DV, intercooler and pipework.

[safety69 0]

Is it possible to make a DIY pressure test kit to try and locate the boost leak?

I would like to do this myself and as I am experiencing the same problems and it's frustrating after having paid for a remap.

I remember reading someone doing the same, but cannot find the post!!

[audiss3 10]

Thanks for all the responses so far guys. It is a map of my actual car using the spreddie on the Ross-tech site.

I have heard all sorts of things that could cause the low actual boost as you have stated. Where is it best to start? I have visually checked the DV and it seems connected fine. Should I get a boost pressure check done first and then take it from there or is there as stated some simple DIY checks i could do first before shedding more money into this?

[shark_90 8]

I would change the DV for a new one, aftermarket if you can. Then I'd do a pressure test to see if you have any split hoses or leaks

[audiss3 10]

Can I get away with a stock DV (701N Bosch item I believe) even though my car has a remap? Reason for asking is that I know I have an uprated DV in there at the moment which was installed at the same time as my REVO map.

When I plant my foot down, after about 4,000rpm I sometimes here a couple of very loud 'whoosh' sounds coming from the back of the engine near the dash, not sure if this is normal? Can the N249 or N75 valves be in question given the stats above that the car is producing?

Sorry for the 20 questions but having spent over £300 in a week on the car and still not any closer to the problem I really would like to do the next steps in a logical manner rather than just replace parts everywhere as a process of elimination if possible.

[Mollox 0]

Sounds like a leaky hose. Back of the dash could be anywhere but I'd check the various hoses that come off of the metal "turbo pipe". In particular, look on the inside of 'bends' and give everything a very close look. These things aren't often that easy to see. Traces of oil (fairly normal) can be a giveaway.

And of course, check everything is clamped on properly too.

[Mollox 0]

Having said that, have you had any fault codes? Boost leaks can often leave tell tale codes (e.g. Maximum charge pressure exceeded) etc.

Thinking about it, if your boost is low - its likely that any leak is on the pre-turbo side (right hand side as you look at the engine) although this is by no means definitive and, also, you're just as likely not to have a fault code....

[Decked 0]

Do you have a boost gauge? or has it ever had one? Could be a pipe running in there letting pressure out behind the dash.

[audiss3 10]

I don't have a boost guage, and VAGCOM has given the car a clean bill of health with no engine related fault codes. I think i may need to get the car on a ramp to check for the leaks because apart from the hoses going from the MAF the others are immpossible to see, especially the big red one going into the back of the engine. Does anyone know if the DV can be replaced with a satndard Bosch one or is that a big no no.

If I have no luck finding a leak I may get a boost pressure leak test done. Does anyone know how much I should be paying for this to be done?

[Mollox 0]

I've run an OEM Bosch DV with a Revo remap for years with no problem

[audiss3 10]

thanks for the info. Just called Audi Dealership and they do them for £28 all in, and it is a product number ending with 710N so i believe this is the latest revision of the part. If it can't do any harm with my remap then its worth the gamble. I will for sure do a boost leak test first and then go down the DV route.

I asked the dealer about the N75 valve, and they didn't have a scoobies as to what it was :0)

[Hopsta 93]

revision N has been about for years so it well and truly tested

[audiss3 10]

Excellent, I always prefer OEM where possible. Can you guys give me an order at which I should check and replace the items. I have spent £300 this week already on the car without getting much closer to the cause of the lack of actual boost pressure, so just want to try do the next steps logically .. Just ran a VAGCOM scan again with no faults whatsover showing.

Based on likelyhood of the cause of the issue, and the symptoms (boost falling short by upto 600mbar, and sometimes get 'whooosh' sounds from behind dash)

- Pressure leak test - £45

- Replace Diverter Valve with 710N - £38

- Replace N75 valve with 'J' variant - Not sure of cost but i believe its around £50-60.

- Replace N249 Valve - Not sure of cost

Is there anyway I can test any of these valves without ripping them open? I do the diverter valve I have installed right now is a Forge 007p one I believe (says Forge Turbo on the receipt).

[safety69 0]

Did you get the pressure test quote for £45 from Audi?

I have the exact same problems as you, I am also running a revo map and the boost on a rolling road is very similar to yours. I am using a Forge diverter valve with the OEM hoses which have been checked over with no concern.

I have run VagCom with no fault codes on the engine which is very frustrating because like you I want the full performance of the remap.

I am going to be pressure testing my pipework but need to work out how I am going to do this. I don't want to be pressurising pipework that doesn't hold boost i.e air intake which will possibly lead to further problems.

Please make sure you return to this post if you are successful in finding the problem.

[mooch 10]

I was loosing boost and turned out to be both IC's leaking like a sieve, both end plates on both ic's were perforated, boost was down to 0.8, replaced the IC'c (£1800!!) and got back to 1.4b.

I know someone who swears by 710's and others who swear at em!

I run Forge DV's and to date they have been fine.

[audiss3 10]

saftey69 - mate I have the exact problem as you and will surely post up if I get to the bottom of it. I had shed lots of money into trying to find out, and if I can save someone else the same bother then thumbs up to that.

Do you ever get a big 'wooosh whooosh' sound coming from behind the passenger side dash, when the throttle is to the floor? almost as if air is literally being dumped out or sucked in ?

The boost leak test is the quote I got from two different Audi specialists so assuming it is the going rate. Would the test pick up leaks on the IC im not too sure, but given that £1800 cost I really hope it isn't the IC.

My forge valve is literally under 2 years old so I'd be really dissappointed if it was that. I am suspecting more a leak, or a N75 valve issue.

From my stats you can see that the lack of boost is pretty much consistent throughout the rev range which to me seems more symptomatic of a leak rather than a busted valve...although I do know nothing about turbo's hence why all options are still on the table. Can anyone shed light into this?

Edited August 14, 2009 by audiss3

[safety69 0]

Audiss3, like you I have spent quite a bit of money so far in trying to correct the problem, a new MAF, Forge DV, new latest green top coolant sensor and lots of rolling road tests at different room temperatures and many trips to various Audi dealerships, but still I cannot beat it.

My last attempt will be a pressure test in the hope that its an easy fix. If I am unsuccessful I think that a part exchange is on the cards which is a real shame because I really love driving my S3 but I want the most from it.

Will be testing mine over the next 2 weeks and will post my findings.

[audiss3 10]

Took the car to another two mechanics today who both didn't have a clue as to what the fault could be. So car is booked in for Thursday with a German 'specialist' who advised he will check over the whole engine including a boost leak test and let me know the outcome. He is charging £50 and said it can take anything upto a good couple of hours to get to the bottom of it.

It's probably the one time when I actually want a mechanic to tell me my car has a fault, as I'm in a similar position to you where I am thinking of getting rid of it, if i can't get the power from the car which is supposed to be delivered.

[audiss3 10]

Update on this one guys. My garage appointment had to be cancelled, so I decided to try get to the bottom of it with a friend yesterday afternoon.

We swapped over our N75 valves (he has a VW 1.8T) and I test drove the car and no difference. Still could feel a lack of boost and the 'whoosh whoosh' sound coming from the dash.

Then I took off my Forge 007p DV and done the check where you blow into it and all seemed very strong and intact.

So finally got our hands right behind the engine and followed the Big Red Turbo hose down to the Turbo. Although you can't see it visually, we following it down to find a Jubilee Clip loose and just spinning on the hose holder at the Turbo end. Feeling the hose we found that the hose has perished towards the bottom end, and we forced as much of the hose onto the turbo end as we could and tightened the jubilee clip. Took the car for a drive, and the power is definetly alot better now.

As per my previous stats, when I hit 4k rpm, it would go all flat and I wouldn't achieve any additional boost, notwthe power rise and turbo boost continues past 4k right towards the top end.

Will have to get this hose replaced (i hear its like £100....ouch), and get the car onto VAGCOM again to see if my boost is back to fully requested levels.

Anyone else with these types of symptoms, please check this hose for splits or lose connections.