S3 Boost Levels

I was told 0.9 bar on a standard 210hp,1 bar on the 225hp.

Maximum efficient boost level on an S3 is 1.45-1.5 Bar tops

It is your wee turbo that is becoming inefficient that will stop you going higher. Any higher and your back pressure will be really bad - running anything above 2.8 PR on that turbo, i.e. anything above 1.6 Bar makes the turbo surge which means that basically it can't fill the engine with the air flow it's putting out and the air flow is coming back into the blades of the turbo making it

If you are holding 1.4 Bar at 6k RPM to get around 280HP you are pushing the turbo close to 165k RPM and if you read compressor maps the max for that turbo is 170k. Above 1.6Bar, efficiency of the turbo is not good, and you will get stupid high intake temps which means the ECU has to ****** timing. Retarded timing means high combustion temps/EGTs and in order to compensate for that, it means dumping lots of fuel.

You will get very high intake temperatures with more than 1.6 Bar and will only produce power when it's cold outside and I know David has some trick Intercoolers but they can only do so much.

Running over 1.6 Bar, or even not tailing off boost at high rpm (to 1 Bar at 7k) also means your backpressure makes the engine more prone to detonation which means even more retarding on top of what it's retarding from high intake temps and even higher EGTs

It's all about diminishing returns - there is a point where if you go past it, you're just throwing money at your project.

HTH

Gee's Guys,

I have to hand it to you two, you know your stuff!

Doug, 600bhp! Your the man! Would love to see that go! Surely you cant be fed up with 438bhp already??!

Doug, where did you learn how to read compressor maps? I have looked at a few and can't make head nor tail of them.

Cheers,

Stevie

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Maximum efficient boost level on an S3 is 1.45-1.5 Bar tops


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On standard ICs...it's probably less than that...and that's just at peak boost.
The S3 ICs are awful...they heat soak and aren't efficient.

With correctly set up ICs you can run higher boost to gain torque.
I regularly ran 1.85-1.89 bar...


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It is your wee turbo that is becoming inefficient that will stop you going higher. Any higher and your back pressure will be really bad -


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Back pressure where exactly, Doug?
Back pressure in the exhaust manifold / cats / exhaust...perhaps.

Possible back pressure in the metal pipe from the turbo outlet to the first SMIC, because of the restrictor / silencer installed in the 'bump' part...maybe. But that's no cause for concern on Davids S3...it doesn't exist anymore!


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running anything above 2.8 PR on that turbo, i.e. anything above 1.6 Bar makes the turbo surge which means that basically it can't fill the engine with the air flow it's putting out and the air flow is coming back into the blades of the turbo making it


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I disagree...
I spend my working life setting up and calibrating industrial compressor control systems...and I'm fully aware of what compressor surge or stall sounds like, once you've heard it, you never forget it!!
...and running 1.8 bar on my S3 didn't cause surge, I can assure you.

I can see that you may get 'stonewalling' of the compressor...where you physically can't move the compressed charge round the system as the engine can't get rid of it (use it)...probably because the exhaust manifold is the restriction (on the S3 it's my belief that this is the case).

With 'stonewalling' you can incrase the compressed pressure but get nothing positive out the other end...although with my S3 gaining torque with every increase in boost at peak torque, this would suggest that the K04 compressor was not 'stonewalling'.

With a decent inlet system, efficient filter etc and a decent IC system...I wouldn't expect to ever get surge...the ECU will hit limp mode well before you risk destroying a compressor with surge.

My experience with surge is that there are no second changes. Surge to wrecked. One directly follows the other!


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If you are holding 1.4 Bar at 6k RPM to get around 280HP you are pushing the turbo close to 165k RPM and if you read compressor maps the max for that turbo is 170k. Above 1.6Bar, efficiency of the turbo is not good,


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I don't believe this is even possible...
Even running the K04 flat out...I couldn't get much more than 1.2 ish bar at 6k RPM.
I just don't think the K04 can move enough air to generate the pressure at those sort of revs.

I know that the K04 on my old S3 was well out of it;s design range, or for that matter efficiency range...but you can run it, as long as you fully understand and address the problems associated with running outwith design parameters.


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and you will get stupid high intake temps which means the ECU has to ****** timing. Retarded timing means high combustion temps/EGTs and in order to compensate for that, it means dumping lots of fuel.


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True...the ECU winds back timing under high inlet charge situations...
But under 30 degrees at the engine, with 1.8+ bar peak boost isn't high temperatures...and logging the ignition timing values would suggest that thet were not being retarded.

EGTs are up...but again, you can roughly log them with VAG Com...and EGTs are far more likely to go high running lean, than they are running high boost - as long as the ICs are working!
The S3s EGTs are fine...as are the AFRs...infact, it's running slightly rich - even at silly high boost!
AFR of approx 0.85 under any boost condition you care to test it... so to some degree it is using fuel to cool the cylinders.

Also, my experience of retarding the ignition timing is that it reduces power, and decreases the temperature of the burn...reducing cylinder temperatures.
In my experience, winding on ignition advance will cause the engine to run hotter...never colder....which again needs a cooler inlet charge to exploit.


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You will get very high intake temperatures with more than 1.6 Bar and will only produce power when it's cold outside and I know David has some trick Intercoolers but they can only do so much.


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Again...I disagree.
I have never seen air temperatures above 30 degrees - summer or winter, road or dyno.

Hell, a standard S3 on standard boost has higher inlet temperatures...
Trick ICs can do exactly what they were disigned for...if they were designed and mounted correctly.


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Running over 1.6 Bar, or even not tailing off boost at high rpm (to 1 Bar at 7k) also means your backpressure makes the engine more prone to detonation which means even more retarding on top of what it's retarding from high intake temps and even higher EGTs


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Agreed...
This i've proved by running an Optimax high boost map on BP Ultimate fuel...you can detect the ECU pulling back the timing to protect the engine.
Logging the knock sensor's input to the ECU will also confirm this...

But, run the correct fuel, and it's not an issue.

Again, I dissagree with the fact that retarding the timing causes higher EGTs...I';ve found the exact opposite.


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It's all about diminishing returns - there is a point where if you go past it, you're just throwing money at your project.


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So very true...
You don't push the limits unless you are prepared to shrug you shoulders and say 'ah well...' when a turbo / bottom end lets go on the dyno!

Think I'm following here chaps. But not commenting, mearly watching from the side lines!

Talking of logging timing - what degrees of ****** do you guy see with vag-com?

Dunc

Having studied the compressor map,1.2bar is still pretty efficient after that it's a flame thrower.

Im going to map one in March myself, realtime on the road.

As I don't own one, I'll be borrowing one, so can't really argue with Dave or Glen (yet) - then we'll see what a standard one can do safely and pushed to it's limits.

I'm confused here doug ...... just to clarify who's mapping one in march you or mineha? It will be interesting to see what is achieved as after a recent run in davids car it reminded me just how good the map is on that car and how strong it feels - It's a case if it's not broken don't fix it - but it will be interesting to see what happens.

No need to be confused Barry /ubbthreads/images/graemlins/smirk.gif

Mihnea is offerring his services to yourself and David - this is in February.

There is only so much you can learn with reading/studying on theory of engine tuning/mapping - the next step is to do it - and relate that to the theory - which I plan to be able to do soon.

Iv'e got the APR stage 2. Problem is my boost gauge tops out at 20psi so i cant see if it goes any higher!

It certainly goes past the 20psi mark but cant go any further. Think I should have bought a 30psi one!

Doug_S2 - it would appear that you know your stuff after reading your response to "S3 Boost Levels". I bought a standard 210bhp S3 back in September 04. I'm looking at having it "chipped" to get more power out of it, being a bit of a novice to this upgrade game, could you point me in the right direction regarding companies to contact, whether other parts of the car will need up grading, ie - brakes, clutch etc etc. Your advice would be greatly appreciated.

Doug_S2 - Thanks for that, I had a quick look at MRC-Developments - looks good. Money will be a factor to be honest regarding the upgrades, so I've got to plan this carefully. The few people that I have spoken to, say that the max you can go to on an 210hp S3 is 265HP, obviously not the case. Been quoted in the area of about £500 for "standard" upgrades, giving about 21% increase in power and torque - is this about right?

My questions are open to anyone else who has the knowledge on S3 upgrades, didn't mean to offend by directing my question to just Doug_S2 - any advice would be welcomed, I'm a new comer to this site, so i'm still feeling my way around.

Doug_S2 - Got say that the figures on your S2 are well impressive, I got a friend who has an S2, told him last night, I'm afraid i can't repeat what he said, I might get barred from this site, he was very impressed to say the least. Hope you get the 600hp figure you're after.

Some interesting points.

I shall make some reccomendations based on experience.

There are essentially 3 or 4 tuning paths to follow.

Firstly a standard generic remap. £500ish will give about 250-260bhp and similar torque. Most manufacturers offer a very similar product, and shopping around doesn't really make too much of a difference.

The next step is to addess some weak points. Namely intercoolers, hoses and to a lesser extent exhaust and cats. In isolation they will not yield any power, but it puts you in the territory of a custom remap which (with the appropriate i/c mods especially) will allow you to run higher boost and more ingnition advance. You'll maybe see 270ish bhp and 280-300lb.ft with an appropriate custom map on the end of the correct mods. Star performance, MRC, AmD (if you specifically ask) can do custom maps to your spec. This option runs the turbo very hard and is likely to reduce service life though.

After that the big turbo kits. You'll ideally need to do the exhaust / cats / manifold / downpipes and cooling with these kits, and as such you would be spending at least £4000. As for power, the jury is out. I have seen some comedy dyno plots showing ridiculous figures that just don't make sense, but i guess you would be looking at about 320bhp / 320lbft (conservatively). There are few companies that do a big turbo kit currently for the RHD S3, and this is something of a holy grail, and has been for some time.

In my mind, £4000 is not worth the outlay for 30ish bhp, and it doesn't make the S3 a really fast car.

IMO you are correct to look at the engine mods, but you'll need to consider chassis mods too (roll bars, suspension, geometry) as well as brakes... A 300bhp S3 with standard suspension and brakes is a write off looking for an accident location...

Re doug's post, I would question the worth of downpipes on a standard turbo car. It has been shown that a 3" downpipe does NOT make power, and I beleive the restriction for power on the standard turbo engine lies in the manifold rather than the downpipe (it makes sense if you have seen an S3 manifold, the ports are TINY)...

David - thanks for that, the more advice/info i can get the easier it will be to plan the up grade. £4000 seems a lot of money, but it would be nice though.

I'm with Stevie S3 when he says you guys know your stuff.

David/Doug - Thanks again for your words and spending the time to write them - appreciated.

I'm still not buying the DP theory Doug. It makes no sense...

If the absolute limit (and therefore pressure obstruction) is the manifold (which I beleive it is) then it doesn't matter how much bigger the downpipe is, it is not going to make a difference.

If the DP was a restriction then why does a car with a 3" DP make no more power, no more boost and no more torque than a standard DP car?

It should, according to your theory make more of each, but real world it doesn't.

A better less restrictive manifold still looks like the key part to change in the exhaust system. There is no evidence that any of the OEM system offers a particluar resitriction with the OEM turbo and manifold.

Like I have said before - I have no experience of the S3 directly - if you do have a 3" exhaust (I was under the impression it was smaller - is it not a twin DP) then you might not gain anything going bigger as you have maxed out your hotside. I know Simons (TT engined Golf) needs a bigger DP to get more than his 270ish bhp - Jim tried to sell him one at the last RR at Star.

What DPs have you tried on the S3?

Read here about exhaust theory on turbocharged cars (I found it interesting):

http://www.tantrumwerks.com/html/Split%20DP%20support%20theory.pdf

a bigger dowpipe may also cause more turbo lag - the velocity of the gases is slower and this results in a slower spool-up of the turbo

this happened on my volvo t5 with a 3" downpipe - more top end power due to bigger gas flow, but poorer torque and turbo lag and the real usable end due to slower exhaust gases.

I strongly agree with the DP theory. Whilst my S2 was being mapped with the original 2.5" exhaust/DP it was struggling to get rid of the spent gas. This was shown by pinking, and we had to back the timing off. After installing a 3" exhaust/DP the boost could be kept higher for longer also allowing us to run more advance, that means more power. I too run a seperate wastegate pipe, this is shown to be a very key feature in gaining extra power. You cant argue with real life figures. I have seen the difference first hand on my own S2.

Just fitting a 3" DP wont give your more power, but add to that a custom map and it will show increases in power and reductions in lag. BTDT.

I have no direct experience of the S3, but the theory is the same on ANY turbo car. A downpipe can never be big enough, to a point. Some of the real high power cars use 4"+ DP's!! and 2" wastegate pipes.

People who saw my car on the rollers at Star Performance in november could vouch for the way that the boost was able to be held higher for longer due to better exhaust flow.

Inlet manifold design isnt as critical. The stock S2 IM is used on my car and doesnt prove to be a problem in the cars setup.

check this video out for the figures:
www.rcmr.co.uk/videos/cap0017.mpg

The S3's IC's are a limiting factor.

On the subject of turbo surging, a turbo can surge without it dying quickly. I too know what it sounds like. You can push a small turbo too hard by running massive peak boost, yeah it gives great torque, but that doesnt aid to long term reliability. If you want the small turbo to last more than 10k miles or so then its best to stay within its limits, not outside. Any decent tuner can read a compressor map and will know how hard he/she can push it without comprimising its life span

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II have no direct experience of the S3

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Thats a good start...

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but the theory is the same on ANY turbo car.

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And similarly fact is FACT and the downpipe theory has been PROVEN to be ineffective in the S3. It may all be well and good on an S2... but we aren't talking about S2s.

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A downpipe can never be big enough, to a point. Some of the real high power cars use 4"+ DP's!! and 2" wastegate pipes.

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As far as I can see the DP could be as big as my hallway, but if the restriction is upwind of it, it'll make sod all difference.

Continuing with my hallway as an example, if I wanted to flood my living room with water from the front of the house, I could have a hallway the size of Blenheim palace, but the letterbox is still going to limit the flow of water into my living room...

A DP on a standard manifold is a waste of time, money, effort and thought... The dyno graphs prove it..

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People who saw my car on the rollers at Star Performance in november

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...would have seen it wasn't an S3.

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Inlet manifold design isnt as critical. The stock S2 IM is used on my car and doesnt prove to be a problem in the cars setup.

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Perhaps on an S2, but for fear of sounding repetitive, we are not running S2s.

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The S3's IC's are a limiting factor.

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True, we have said this all along, whats your point?

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On the subject of turbo surging, a turbo can surge without it dying quickly. I too know what it sounds like. You can push a small turbo too hard by running massive peak boost, yeah it gives great torque, but that doesnt aid to long term reliability. If you want the small turbo to last more than 10k miles or so then its best to stay within its limits, not outside.

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How does 3.5 years and 30k miles sound for longeveity - again theory is theory, but fact always trumps it.

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Any decent tuner can read a compressor map and will know how hard he/she can push it without comprimising its life span

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Again, theory, not reflected in the real world...

There are some very well respected tuners out there using boost levels in what has been branded the danger zone - surely it's all about risk / benefit? We know the risks of upping the boost, but also we know the risks of driving fast and crashing - again, what's your point?

I'm wondering whether a certain Belgian tuner has put something in everyone's tea?

/ubbthreads/images/graemlins/lol.gif

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And similarly fact is FACT and the downpipe theory has been PROVEN to be ineffective in the S3. It may all be well and good on an S2... but we aren't talking about S2s.

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You are correct - we started talking about volvos, reductions in torque, and general DP theory. /ubbthreads/images/graemlins/wink.gif

Watch this space /ubbthreads/images/graemlins/tongue.gif

Call me stupid David, but i have my views. Thats what this forum is for. Clearly you have a good experience of the S3. The theory is proven on EVERY turbo car. Not just the S2. OK so the 1.8T engine is different. Maybe im wrong. But i have a good understanding of a turbo car and how it works. You have your views and i respect them. Like you pointed out, i have no direct experience of the S3. But i do have experience of high powered engines. I DRIVE ONE EVERY DAY, and i know what needs to be done to acheive the figures that count. BTDT.You saw the car. It doesnt take a fistful of notes to make a car quick, it takes knowledge and hard work.

The main restrictions on the s3 are the manifold and turbo.There are no off the shelf kits to replace these so any amount of tuning or a 3" downpipe is going to see minimal gains.The standard ic's are also not the best of design and improvement will prevent high intake temps and retardation of timing and boost.Also i have my misgivings of a series ic set-up as it might produce to much pressure drop and therefore make the turbo work hard(heat) to produce a given peak boost but guys who are running big fmic on TT's don't seem to have much higher figures than guys with standard ic's so may this is tosh?

Dont Jabbasport do a high flowing manifold IIRC?? But this may only work with the IHI turbo. Not K04.

The Jabba manifold is specific to the aftermarket turbo. AFAIK there is no replacement manifold for the K04 available.

With regard to I/Cs, running a very large capacity FMIC may be problematic, but the ideal solution is to increase the surface area as much as possible, whilst maintaining the volume close to OEM

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Getting back into it slightly and this goes out to David R…….well, to anyone actually. If I were to opt for a "standard" chip to just 265bhp, in order to satisfy my urge for more power at the moment, would I need to upgrade any thing else, or would the standard running gear on an S3 be able to handle it. Could I get the engine remapped to 265bhp, and not worry about brakes, suspension, clutch etc etc.


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It's perfectly feasible to run 265bhp on an otherwise standard S3, but not so much fun. It is underbraked and underdamped as well as having a rather safe and nannying understeer setup.

Some work on brakes and suspension will make the car more controllable, alot more fun and quite a bit quicker point to point.

David - So what mods would you recommend??

suspension -

1) slighlty lower springs 20-30mm eg mtm/quattro gmbh -20mm springs
with bilstein dampers

2) uprated neuspeed front and rear anti-roll bars (fantastically effective once you have done the springs and dampers)

3) tweaked geometry - as much negative camber at the front as possible, slight toe out at the front

4) rear adjustable tie bars - then set -0.75 to -1deg negative camber

brakes-
best for road and chipped car is probably the junior bremboi kit (about £800 or so)

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AFAIK there is no replacement manifold for the K04 available.

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Hi all.

I understand TurboDynamics do one. I asked about their hybrid K04 and they mentioned it...

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AFAIK there is no replacement manifold for the K04 available.

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Hi all.

I understand TurboDynamics do one. I asked about their hybrid K04 and they mentioned it...

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They don't, I have emailed them.

A replacement manifold is available for other turbos, but not the K04

Cool. My first post and I'm wrong. /ubbthreads/images/graemlins/tongue.gif

Could've sworn that was what he was getting at...

He did say that the Cupra R has the "better" manifold - I'm now not sure what he was getting at there either?

Dunk - Cheers for that mate, sorry for not getting back to you sooner, been a bit tied up at work, that thing that gets in the way of your day!!

.

Guys - can I just say - all your advice and thoughts that you have offered have been printed out onto paper and filed. Can i thank you all for your tech know how, hints and tips. If you see a silver S3 pulling up behind you rather quickly - it could just be me!!

i agree with david r, there is no point what so ever with a bigger diameter down pipe if the manifold is restrictive. he is correct you could let it go to atmosohere and it would still make no difference, BIGGER MANIFOLD NEEDED!!!

lasarge, have a custom map that is not pushing the engine too far, good tuners can set this up for around £500 ish, just get a brake upgrade maybe cross drilled and groved, your s3 should already have a roll bar on the front of the engine, depending on build date.

the rest of the car should be up to the job! capable of 260-280bhp without many more modificatiions!

Ok, thanks for that, I'll let y'all know what happens. You said "without many more mods", what would you suggest, if at all???

Hi,
Rather thick on this subject and only had the S3 just over a year it's always been a bit strange like turning a switch on and of .
Question .
After some recent repairs on a test drive it was compared to a standard 225 TT and found to perform rather differently ?the TT being quicker initially but the S3 being quicker midrange not really pulling until 3500rpm does this mean it's been modified or chip etc as it has very little below this level and it's running spot on ,no fault codes etc.
What do you guy's think.
Merdock