my car is too slow!

[S4_SAT]

my reg is r33 tus so its easy to spot. a 'little' renault clio [img]images/graemlins/thumb.gif[/img]

[Hinesy]

are they still wet lined engines - my missus had a renault 5 which blew up spectacularly one evening outside Edinburgh


also seen a blue RS4 on the M8 in Glasgow...

[S4_SAT]

its a common rail dci engine.1.5 turbo diesel.65bhp and shitloads of torque for the size of car.i get wheelspin in fourth on wet days.raced an e46 m3 on the motorway,dunno how but i beat it. hail to the clio [img]images/graemlins/notworthy.gif[/img]

[Golich]

I live in Aberdeen but I am thinking of getting Jim at Star performance to service my chipped S4 and carry out a rolling road test at the same time.

I just need to check my service book to confirm when the next service is required. I'd be up for a meet then. If you two want to meet up? [img]images/graemlins/clap.gif[/img] [img]images/graemlins/yellows4.gif[/img]

[Dippy]

I did some more 50-70 timings this morning, with the following results:
50-70 in 4/5/6 - 4.75s/5.6s/6.9s
so maybe it's not as bad as I thought [img]images/graemlins/smirk.gif[/img]

Also, I had initially been filling up with regular unleaded, and last time switched to super.

I think those times are OK for a standard S4, but DJG is the authority on roll-on times [img]images/graemlins/bowdown.gif[/img]

If you've been using 95 RON then that's certainly your problem.

DavidT asked for it so:

The octane number (RON = research octane, a measurement technique used primarily by the oil refiners) is an indication of the 'reliability' of fuel detonation.

When the fuel/air mix is compressed in the engine's cyclinder and detonated with a spark, the actual explosion must be 'perfectly' timed in relation to the position of the piston as it goes up and down in the cylinder. If it detonates too late, the full energy of the explosion won't be harnessed, get it right and the use of the energy is optimised.

However the other scenario, detonation too soon, is the bad one. This means that some of the energy of combustion actually acts against the piston. Not only does this mean that the energy is not properly harnessed, but it can cause damage to the engine. This 'pre-detonation' can be caused by bad ignition timing (more relevant to older engines with distributors), in which case it's known as 'pinking'. However pre-detonation can also occur when the fuel/air mix spontaneously combusts due to temperature and compression. This is known as 'knocking'. The octane number of fuel primarily relates to how easily it will 'knock'.

Now the energy you get from an internal combustion engine is very simply related to how much fuel/air mixture you can detonate in a given time. Thus high performance engines need a combination of displacement and compression. Compression occurs from the design of the engine (cylinder bore and piston stroke) but also in some engines, by forcing the air in (e.g. turbo charging). Hence high performance engines, and in particular turbocharged engines are more susceptible to knock.

Since knocking is bad, our engines come with knock sensors to detect the condition. If knocking is detected, the ECU will immediately <beep> the ignition timing to ensure that combustion is controlled. However as a result the full energy of the detonation will not be harnessed, and full performance will not be achieved.

So in order to get full performance from the engine without getting knocking, a high octane fuel is required. Engines are designed to use a certain octane, and the S4's was designed for 98 RON. Using 95 RON in it will mean that knocking will start and so the ECU will <beep> the performance in order to protect the engine.

So what if you use higher than 98 RON? Well that depends on the engine design. If the engine was designed such that the timing can be advanced further to increase performance, then it will be beneficial to used higher RON fuel. However IMO I don't think this is true for an OEM ECU car.

What is true, however, is that higher octane fuel burns more slowly than lower octane. It should certainly be true that using a higher octane fuel should make the engine run smoother. However since the fuel burns slower, then the 'delivery' of the energy will also be slower and therefore again, IMO, it should be more effectively harnessed in the cylinders.

In terms of "real-life", I have the following experience:

1) Using 95 RON seriously reduces my engine's performance.
2) Using 97 RON from Sainsburys produces noticibly less performance from my engine than using Shell Optimax.
3) I have never satisfactorily felt any improvement in performance by using Millers with Optimax, however I believe that it should make an improvement, but it is subtle. Nevertheless I know that the improvement to fuel burn caused by Millers is good for my engine and I will continue to use it.

Cheers,
Dave

[DavidR]

David_R, thanks for the offer. Maybe we could get a few others and arrange a Scottish meet? Is your car standard? I'd quite like to see the difference between a standard and chipped S4 - although maybe not until I can afford to get mine chipped [img]images/graemlins/wink.gif[/img]

There are several who suspect it is chipped, but I have not had time to either crack the ECU open or get it on the rollers. I'm off out to do the 50-70 and compare. I PMd you also with some meet details.

Cheers

David

[ammwhite]

Dave (Dippy),

Great post. Thanks for that explanation - I've heard all the terms (pinking, knocking etc..) before but never knew exactly what they meant [img]images/graemlins/confused.gif[/img]

I'll definitely try to stick to Optimax in the future. [img]images/graemlins/062802drink_prv.gif[/img]

[DJG]

Hi,

I did collect quite a few standard 50-70 figures on the old Audi-Sport site.

Here are what I found:

Standard S4s.
50-70 4th, 5th 6th
Andy 4.75s, 5.6s, 6.9s
Toasty 4s, 5s, 6s
DJG (old) 4.1s, 5.2s, 6.2s
DJG (now) 4.5, 5.5, 6.5
Laurence 5s, 5.5s, 6.5s (Think there turned out to be something wrong with Laurence's car when he got it chipped)

Modified
Dippy's S4 2.5s, 3s, 3.5s
Nige S4 3s, 4s, 5s
JR's RS4 2.3s, 2.7s, 3.1s

Because I am such a sad bastard I have measured my 50-70 loads of times when bored on my way to work and until recently would always get between 6.0 and 6.2s in 6th. In fact the 20MPH increments up to quite high speeds [img]images/graemlins/grin.gif[/img]were pretty consistent.

With new DVs it is now normally 6.5s, but the car has just been RRed at 271BHP/329lb ft, so is basically healthy and otherwise drives fine.

Just one of those things [img]images/graemlins/confused.gif[/img]

Sorry for starting this.....paranoia is catching!

David

[cidered]

Just accessed the site after a long break without internet - and found I have exactly the same concerns as Andy, and also exactly the same timings through the gears (7.4 secs 50 - 70 in 6th).

It was a mate's S3 along a motorway slip-road that started me worrying - only a 215bhp version, but it was definitely pulling away from me.

Mr S4 is a late 98, immaculate condition but high milage (93,000 - it's seen a lot of motorway!). However, the neither have tools, skills or really the time to check anything out myself - are there specialists in the South anyone would recommend as being a dead cert to pinpoint whatever problems I might have? Ideally - I'd like to see a before and after rolling road test, but from earlier posts that may be prohibitively expensive.

Basically - if there's even a hint the turbos are on the way, I need to get shot of the S4 straight way.. so a recommendations of a company who really know their stuff would be appreciated!!

Thanks.

[Dippy]

QS Tuning.

Your turbos could be on their way out at that mileage, but then it could also be an air leak. The telltale signs of turbo failure are noise and oil.

Healthy turbos only make a soft whistling noise between 1000-2000 revs (IIRC), and often you can only hear this at low speeds with a window open. So I suggest that you go for a drive at 20-30 mph with your passenger window open and listen for it. Then try gently applying boost and listening. If you start to hear any 'whistling' sound then something may be wrong.

If the oil seals are going then you will start to get oil leaking into the exhaust. Look for smoke on start-up. If you see any then there is some cause for concern. If it lasts for more than a few seconds then there is serious cause for concern.

If you have none of the above problems then you need to check for air leaks. This does take time, so you'll need someone like QS tuning to do it. Alternatively an Audi service dept should be able to do it, but that depends on how experienced the tech is - for example they need to know which hoses to check and which need to be removed in order to check for tears.

Cheers,
Dave

[Dippy]

I am not too sure about the if you can hear the turbos whistle then they are probably on their way out, as i would be very suprised if you cannot hear them spool up on a brand new car.

On a brand new S4 you can barely hear the turbos with the windows down. I have experienced this on 3 new S4s including my own.

...i think the question is how loud the whistling is, which must be an experience thing i think. I can hear my turbos spool up with the windows up or down, but i don't think they are knackered as the car uses next to no oil between changes.

I'm not sure that using no oil is a surefire guarantee that nothing is wrong. However you are correct that you need to know what sort of sound you are hearing for. All I know is that whenever an S4 owner has complained of a whistling sound, especially with the windows up, it has been because the turbos are on their way out.

However such reports are also often accompanied by complaints of loss of performance, so if you car is performing well, then it must be OK.

[Dippy]

[img]images/graemlins/beerchug.gif[/img]

[cidered]

Thanks for your suggestions... I have noticed a little smoke on startup, but no detectable whine at present (will check later tonight though).

Do you have any contact details for QS Tuning? I've had a quick scan on the web and can't find anything. Like I said, having an expert certify that things are bad or good would be very useful - any hint that the turbos are on the way out, and a straight swap for a C36 AMG until RS6 residuals reach £25k* seems a good idea!


*If I'm not too busy to pick one up on Tuesday week! [img]images/graemlins/wink.gif[/img]